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HARVARD UNIVERSITY e Library of the Museum of
Comparative Zoology
Gilbert Dennison Harris (1864 - 1952)
Founder of the Bulletins of American Paleontology (1895)
ISBN 0-87710-42 1 y
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Begun in 1895
OLUME 105,NUMBER343— SC OCTOBER 20, 1993
Jurassic and Cretaceous Trigoniid Bivalves from
West-Central Argentina
by
Hector A. Leanza
Paleontological Research Institution 1259 Trumansburg Road Ithaca, New York, 14850 U.S.A.
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Begun in 1895
VOLUME 105, NUMBER 343 OCTOBER 20, 1993
Jurassic and Cretaceous Trigoniid Bivalves from
West-Central Argentina
by
Hector A. Leanza
Paleontological Research Institution 1259 Trumansburg Road Ithaca, New York, 14850 U.S.A.
a
ISSN 0007-5779 ISBN 0-87710-430-1 Library of Congress Card Number: 93-085393
Printed in the United States of America Allen Press, Inc. Lawrence, KS 66044 U.S.A.
CONTENTS
Page
ENRTIRIIE( a ots ps Ae rare Pe OSC ate EASE Tenia ois Renin Gon cIc amen oma enema cir Aan etn Pas Gone OOO OCHO Cone Umno eae 5 ETN EDCOLUGEL OMe een Hers ee acre ae ae Saas PNET avr Te Toy Snare STORMS hte osenecte coe eiecna den aren enceatcayana fe Peweveus seieteousneblorevere eieyeveie atevaveyayersteparaveneker 6 Comments onthe: Family sMriponiidae: eo oyeie sje ciel lescisvcicvere eteicte ste cis creschevets esse eleva rctava: ora tovata,etevaleles otal olete a) fe) sje! fail eletheteteieleveeten-ts|=tei= 6 Geological setting of the trigoniid bearing strata in west-central Argentina .......... 22.2... 00 e eee eee eee eens 8 Temporal distribution of trigoniid bivalves in west-central Argentina ...............- eee e eee eee eens 9 MEQ WE TP JUTASSIC SPECIES sere cl ocie ore oie) -atel eschrsvere ei syn reuse) axeneven shes eleven eveteve 21 cueterevalenesereve fetteve fate aietevene slerekeyenetale coveretelYetey sta) Veter seve) tev eteeretal 9 IMitd dle py UraSSIC!SPECIES A here se cise cee rere etic tetera cir ear she foie co eds snot cteleyccfcTs/c eyans chtevevars efelaverorer RoveWars lofe) sNetece el ete te letateset=tclisicl= tate! isieye¥aretsls tees 10 NO PPELAVULASSIC SPECIES) cots sort stave acre onesie sieieis eos eehote w ehel cetevare le) aie crave Svefeva vena sheverai nets tush ove t\epe¥eysusrereiieyete dene) sewers (reel telatars) ayepavatolotee/a(ovol= 11 OWET SretaACCOUSISDECIES! © crece safest sie esos are eve tese. re tevwicte ror alaveyeveysteve re tetci susie late evevenehe le ete ers tale stelelolse)eveis (afesmraxeislehetatarsWanetotesebafsis|orenee tarsi 11 WiopenCretaceousSpecies! y eryere ey iore octave er ctavercie ence eters eee eve erensen = teeter olcvans elevedassteaelateten Neneysvavataje vaveyesenevs sTeiehoenehed Meveretecteie Tater 12 Species durations of the Family Trigoniidae in west-central Argentina ........... 2.6... e eee eee eens 12 PACK OW] EC SETILEMIUS Searcy eter ye eis fe syere ene Fe rarer ene oyaleTe ul ReveNews Te sterebe ave ener h at steLevey sv eeeiearanehe ay cveneuslievsyeyerelet arevsta a) overereteneVNeyetoloyetotetererevey ole tctor-vetets 14 Iniroductionstorsystematicipaleontology) Wecriccisciyas actos ctl onveynrstevavete elcteneve iciene ie orsraie are evorercteretelel = ctevere/alotetetatel elevate) easter siis shel -¥eieat-y<¥s 14 Plea iortenll Conistelsetsot, Mme don ado vednaseocdassanclbe duce bine oUbAncoppancothiascupenooupmnadcqood oo doccospneonndas 14 BICONE ITO] OZ Va maven save recess eee are cic eke ss vctetctc tate eer eetevene vars cre yetaveyep Nev eteepayelelclevensvafenacsversucte eveveVeresstctevenete fevetereseterensheliotetetetor etetehoneiottey=Felelet¥=[< 16 IMeasurementS:andsabbreviatlOnS) cicis ericic.c ole c cre eysicteteieetone fete iate eteliens absl ovaraue eetaevehe: aravenactevsraveve epeveWat ts, nev etore) oFateWoltexefovebel “heVevehatetevanssonet= V7/ Abbreviations ofrepository anstitutions: <2s22.c. xcinctern sins s cre weil © 0 «we Sree hee apetetciete als ole atsra el shevatavalesovsy aol alfelevafe/elete)seheleVevere/eteleyverene 18 Systematicdescriptioms: waystccy- cree cicovin.c setec seciceste rar rere eva teene spare ons eke aaesbe e eirstays ay shsvecatec ees yvauera Vere teveyey ate cets) Shekel taysectenfelaratefekelarayeitet= 18 Appendix: Fossil localities of the described taxa and associated fauna ............. 2600 e eee eee eee eee eee 65 RSP Rae CN etl oo Ae erat ee aaa ae ee ee St Rint nl rah hohe irr ge cen nr etn ne GMerr cua pOeonn GoM tT UOTa Lr Od.cn 68 TGS oaie Gb Sb SG CAE CA ALOE EIS Ge ce ene Rn Pan a eed hs BIG eC Oe EM MIC AES nn nCURAE OO RAA SOSA SO Oc PADD AntRoGHME no coma Sa 74
TDYGLERS scare. eps BRS uO EO CECT CEERI Pa DIRE Tee ini Oe ceiMcHcn too ern osoctie aor cosmncd aUcoboncd nde neo rincMnn oct 91
LIST OF ILLUSTRATIONS
Text-figure Page 1. Wocationof fossil localities’ 2 sc)ecacccnge ccesros o-oo 3 ore Se c/o teens reisiors sycusis ove elle ela) eve eet ye ate eget seeee er sas hats oot Reka tee ae 7 2. Schematic stratigraphic section for the Jurassic and Cretaceous of west-central Argentina: ...20 fxg. 11. 0 eesti oe 9 3. Morphological terminology used to describe trigoniid bivalves in this paper... ..-.--- 6-5 e seen 17
LIST OF TABLES
Table Page
1. Stratigraphic distribution of Jurassic and Cretaceous trigoniid bivalves in west-central Argentina, in stratigraphic order ......... 13
2. Stratigraphic distribution of Jurassic and Cretaceous trigoniid bivalves in west-central Argentina, in systematic order ........... 15
JURASSIC AND CRETACEOUS TRIGONID BIVALVES FROM WEST-CENTRAL ARGENTINA
By Hector A. LEANZA! With the contribution of JosE I. GARATE ZUBILLAGA?
ABSTRACT
This monograph describes 73 species and | subspecies of precisely dated Trigoniidae from the Lower Jurassic (Liassic) to the Upper Cretaceous (Maastrichtian) of western central Argentina. These are classified into 14 subfamilies as follows: Minetrigoniinae, Trigoniinae, Neuquenitrigoniinae, n. subfam., Frenguelliellinae (emend.), Myophorellinae, Vaugoniinae, Steinmanellinae, An- ditrigoniinae, n. subfam., Megatrigoniinae, Buchotrigoniinae, n. subfam., Pterotrigoniinae, Laevitrigoniinae, Austrotrigoniinae and Nototrigoniinae. The Frenguelliellinae are reinterpreted to range in age from the Triassic to the Middle Jurassic (Bajocian), and include only the genera Frenguelliellaand Kumatrigonia. Neuquenitrigoniinae, n.subfam., include the very specialized Middle Jurassic genus Neuquenitrigonia, which shows a transversely costate flank and escutcheon, characteristics that are absent in Trigoniinae s.s. Anditrigoniinae, n. subfam., is erected to group the Middle Jurassic to Lower Cretaceous genera and subgenera Eoanditrigonia, n. subgen., Anditrigonia, Paranditrigonia, Antutrigonia, Virgotrigonia, and Lambertrigonia, n. gen., which are characterized by an smooth area in early representatives, or by transverse or radial ornamentation, or a combination of both, and a poor to well developed marginal carina. The Buchotrigoniinae, n. subfam. include the very specialized Lower Cretaceous genera Buchotrigonia and Syrotrigonia, which are characterized by a tripartite development of oblique, subconcentric and subvertical costae on the flank. The treated genera are twenty one, including: Groeberella, n. gen. (type species: Myophoria neuquensis Groeber, 1924), Trigonia, Frenguelliella, Jaworskiella, Myophorella, Scaphotrigonia, Scaphorella, Neuquenitrigonia, Vaugonia, Andivaugonia, n. gen. (type species: Trigonia radixscripta Lambert, 1944), Steinmanella, Virgotrigonia, Lambertrigonia, n. gen. (type species Trigonia pichimoncolensis Lambert, 1944), Anditrigonia, Antutrigonia, Rutitrigonia, Syrotrigonia, Pterotri- gonia, Quoiecchia, Austrotrigonia, and Pacitrigonia. The genus Myophorella is divided into the subgenera Myophorella sensu stricto, Promyophorella, and Haidaia. The genus Steinmanella is represented by the subgenera 7ransitrigonia, Macrotrigonia, and Splenditrigonia, n. subgen. (type species: Trigonia splendida A. F. Leanza, 1941). Anditrigonia is represented by Anditrigonia sensu stricto, and by an early representative, Eoanditrigonia, n. subgen. (type species: Trigonia keideli Weaver, 1931). The Upper Jurassic and Cretaceous genus Pterotrigonia is divided into the subgenera Prerotrigonia sensu stricto, Scabrotrigonia, Rinetrigonia, and Notoscabrotrigonia.
Ten new species and one new subspecies are established, as follows: Frenguelliella poultoni (Liassic), Trigonia losadai, Trigonia levyi, Frenguelliella perezreyesi, and Scaphorella camachoi (Middle Jurassic); Myophorella (Myophorella) schulzi, Myophorella (Haidaia) elguetai, Pterotrigonia (Notoscabrotrigonia) coheni, and Anditrigonia (A.) eximia tesselicaudata (Upper Jurassic); Ru- titrigonia kauffmani and Syrotrigonia brocardoi (Lower Cretaceous).
Comments on the Family Trigoniidae, as well as taxonomic considerations, stratigraphic occurrence, and facies relationships of the described species are presented. With the new taxonomy proposed here, the trigoniids have a much greater temporal resolution than previously thought, especially at the species level.
RESUMEN
En la presente monografia se describen 73 especies y una subespecie de Trigoniidae precisamente datadas del Jurasico inferior (Liasico) al Cretacico superior (Maastrichtiano) del oeste central de la Argentina. Estas se clasifican en 14 subfamilias a saber: Minetrigoniinae, Trigoniinae, Neuquenitrigoniinae, n. subfam., Frenguelliellinae (emend.), Myophorellinae, Vaugoniinae, Stein- manellinae, Anditrigoniinae, n. subfam., Megatrigoniinae, Buchotrigoniinae, n. subfam., Pterotrigoniinae, Laevitrigoniinae, Aus- trotrigoniinae y Nototrigoniinae. La subfamilia Frenguelliellinae se reinterpreta extiendiéndose en edad desde el Triasico hasta el Jurasico Medio (Bajociano), e incluye solamente los géneros Frenguelliella y Kumatrigonia. Neuquenitrigoniinae, n. subfam. incluye al muy especializado género del Jurasico Medio Neuquenitrigonia, que muestra costulacién transversal en area y flanco, caracteristica que esta ausente en Trigoniinae s.s. Anditrigoniinae, n.subfam., se erije para agrupar generos y subgéneros que se extienden desde el Jurasico Medio al Cretacico Inferior, tales como Eoanditrigonia, n. subgen., Anditrigonia, Paranditrigonia, Antutrigonia, Virgotrigonia, and Lambertrigonia, n. gen., que se caracterizan por areas lisas en representantes tempranos, 0 por una ornamentacion transversal 0 radial, 0 una combinacion de ambas, y una débil a bien desarrollada carena marginal. Buch- otrigoniinae, n. subfam., incluye los muy especializados géneros del Cretacico Inferior Buchotrigonia y Syrotrigonia que se caracterizan por un desarrollo tripartito de costillas obliquas, subconcéntricas y subverticales sobre los flancos. Los géneros tratados son veintiuno, incluyendo: Groeberella, n. gen. (especie tipo: Myophoria neuquensis Groeber, 1924), Trigonia, Fren-
' Secretaria de Mineria. Member of the National Research Council (CONICET). Av. Julio A. Rosa 651. 1067 Buenos Aires. Argentina. * Museo Juan Olsacher. Direccion General de Mineria. Olascoaga 421. 8340 Zapala. Neuqueén. Argentina.
BULLETIN 343
guelliella, Jaworskiella, Myophorella, Scaphotrigonia, Scaphorella, Neuquenitrigonia, Vaugonia, Andivaugonia, n. gen. (especie tipo: Trigonia radixscripta Lambert, 1944), Steinmanella, Virgotrigonia, Lambertrigonia, n. gen. (especie tipo: Trigonia pichi- moncolensis Lambert, 1944), Anditrigonia, Antutrigonia, Rutitrigonia, Syrotrigonia, Pterotrigonia, Quoiecchia, Austrotrigonia, and Pacitrigonia. El genero Myophorella se divide en los subgéneros Myophorella sensu stricto, Promyophorella, y Haidaia. El género Steinmanella esta representado por los subgéneros Transitrigonia, Macrotrigonia, y Splenditrigonia, n. subgen. (especie tipo: Trigonia splendida A. F. Leanza, 1941). Anditrigonia esta representado por los subgéneros Anditrigonia sensu stricto, y por un representante temprano, Eoanditrigonia, n. subgen. (especie tipo: Trigonia keideli Weaver, 1931). El genero Pterotrigonia caracteristico del Jurasico Superior y Cretacico se divide en los subgéneros Pterotrigonia sensu stricto, Scabrotrigonia, Rinetrigonia, and Notoscabrotrigonia.
Se establecen diez nuevas especies y una nueva subespecie a saber: Frenguelliella poultoni (Liassico), Trigonia losadai, Trigonia levyi, Frenguelliella perezreyesi, y Scaphorella camachoi (Jurasico Medio); Myophorella (Myophorella) schulzi, Myophorella (Haidaia) elguetai, Pterotrigonia (Notoscabrotrigonia)coheni y Anditrigonia (A.) eximia tesselicaudata, n. ssp. (Jurasico Superior); Rutitrigonia kauffmani y Syrotrigonia brocardoi (Cretacico Inferior).
Se efectian comentarios sobre la Familia Trigoniidae, asi como consideraciones taxonomicas, distribuciOn estratigrafica, y relaciones de facies de las especies descriptas. Segiin la nueva taxonomia propuesta, los trigonidos muestran una mucho mayor
resolucion temporal de la que se creia previamente, especialmente al nivel de especie.
INTRODUCTION
This revision of the Trigoniidae from west-central Argentina was necessary in order to update the taxo- nomic knowledge of this interesting group of bivalves, and to improve the Jurassic and Cretaceous biostra- tigraphy and paleontology of the southern Andes.
The first description of trigoniids in west-central Ar- gentina was made by Gottsche (1878), based on fossils from Espinacito Pass in the High Cordillera of San Juan Province. The knowledge of the family in this region was later improved by Behrendsen (1891-1892), Tornquist (1898), Burckhardt (1900a, 1900b, 1901, 1903), Haupt (1907), Douvillé (1910), Jaworski (1916, 1925, 1926), Groeber (1924), Weaver (1931) and A. F. Leanza (1941, 1942). It was Lambert (1944) who published the first paper exclusively dedicated to tri- goniids from Neuquén Province, describing a total of 24 species. Levy (1966, 1967a, 1967b, 1967c, 1969, 1985) published a number of papers devoted to the taxonomic revision of the Argentine trigoniids, and Marinelarena (1959) described an Upper Jurassic spe- cies from Neuquén. Camacho (1967, 1968) described Upper Cretaceous trigoniids, and Camacho and Ric- cardi (1978) published a list of fossil invertebrates from Neuquén including an updated list of trigoniid bi- valves. In recent years, Camacho and Olivero (1985), Leanza (1981, 1985), Leanza and Garate (1983a, 1983b, 1985, 1986, 1987), Leanza, Pérez and Reyes (1987), Mancenido and Damborenea (1984), Farinatti, Quat- trocchio and Labudia (1987), and Leanza and Casadio (1991) described several species mainly from the Ju-
assic and Cretaceous of the Neuquén Basin. he present monograph includes the description and xonomic revision of 73 species and one subspecies trigoniid bivalves. Of these, 71 species have been
\lected in Neuquén Province, one species is common both in Neuquén and La Pampa Provinces, and the remaining two taxa were found in La Pampa Province. The studied material has been collected over the past
20 years from 41 different fossil localities (Text-figure 1). In the systematic descriptions, a concise diagnosis is provided for each genus and/or subgenus, and a discussion is added in the case where new morphologic information or new taxa are described. New concepts of trigoniid morphology and descriptive features, which are valuable in differentiating taxa, are included in the systematic descriptions, such as the dorsoposterior and ventroposterior angles or junctions (Kauffman et al. in preparation); these parameters better define the shell shape of each species than those previously used. Char- acters of the ornamentation of the area (see Termi- nology, p. 16) were especially taken into account when distinguishing species or even genera and subgenera (Pérez and Reyes, 1987). Many previous trigoniid workers (e.g., Cox, 1952, 1969; Nakano, 1960) have been conservative in their approach to higher taxo- nomic division of the Trigoniaceae, but more detailed morphologic analysis in this study has allowed new revisions at the subfamily level. Taking as a point of departure the interpretations of the family by van Hoe- pen (1929), Kobayashi (1954), and Saveliev (1958), 13 subfamilies, two of them new, are herein distinguished. Species duration may be as little as one million years for 27% of the described trigoniid species; the average species duration is 3.8 million years.
COMMENTS ON THE FAMILY TRIGONIDAE
The bivalve family Trigoniidae, generally the group of ‘les trigonées” of Lamarck (1819), had a cosmo- politan distribution throughout the Mesozoic. During this time they developed immense diversity of form and external sculpture, which is reflected in a large number of genera and species described from every continent. The family is characterized by a peculiar paleoheterodont dentition and by varied, highly or- nate, thick shells of trigonal shape.
The superfamily Trigoniaceae, which includes both
TRIGONIID BIVALVES OF ARGENTINA: LEANZA
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Los Laja ' <
5 VN.DOMUYO } Pom \ . , ee cHos '|\ MENDOZA LA |- Co.Pitren J jimi nVaAs 4 2- Puerto Curaco iS MAL AIL Ro) 3- Pichaihue Abajo a79e =a rae Oe 4- Trahuncuré © } ee BGO | PAMPA 5- Bajada del Agrio mes | 6- Bajado Vieja ° Bue | 7- Mallin Quemado CONEGRO [8] | 8- Co.Mesa(Covunco) @peHuENcHE pit 68° 9- Co. Negro(Covunco) Sei ree 10- Co.Covunco Pavia ia ROR Q iN are teen ven ken seem ee! 14 - Cto.Caracoles ‘. 48 CO.AUCA MAHUIDA 12- Los Catutos » {3- Laguna Blanca SS = Hualcupen ; ‘ ae = VF ‘ 14- Ea Marichelar,Nirecd 38°. yy ——_ ‘ +-38° ae \(Loncopue 15- Los Pozones . be oat 16- Barda Negra Sur oY t o Nic oO PU : be
17- P.Leufu creek & route 40 48- Co.Negro(P Leufu)
19- Aguada del Overo
20- Canadén del Sapo 21 - Maquina Cur, Chacaicd 22- Caichigiie
23- Fortin4°deMayo
24- Cto Roth,Piedra Pintada
. KS Ss PicdnLeuty K
Graphic scale 50
SOUTH AMERICA
25 - Mirador del Chachil 26 - Cerro Granito
27- Cerro Villegas
R i 0 28- Arenal deLas Lajas
29- Los Hornos,Covunco NEGRO 30- Salitral delos Alazanes 31 - Cerro Pancho
32 - Cerro Lotena
33 - Laguna Miranda
34 - Camino nuevo a LosMolles 35 - Conhadon Nancu Huau 36 - Las Cortaderas
37 - La Amarga
38 - Ea.Souraya
39 - Ea. Santa Isabel
40 - CarrinCuré
- Bardo Baya
Gib. Ines LopezPardo
Text-figure 1.—Location of fossil localities.
the Trigoniidae and the Myophoriidae, has been phy- letically isolated since the Late Silurian. A modest ra- diation occurred in the late Early Permian, leading to increased diversity. The radiation of the Trigoniaceae was interrupted briefly by the major extinctions of the Late Permian. But the radiation continued and in-
creased through the Mesozoic, during which time the family Trigoniidae reached its acme. The majority of trigoniid lineages terminated abruptly at the end of the latest Cretaceous (Maastrichtian) in coincidence with the world wide mass extinction episode at or near the Cretaceous/Tertiary boundary. During the Cenozoic a
8 BULLETIN 343
few trigoniaceans survived in temperate waters of the continental shelf of the Austral Province, where they were represented by Eotrigonia, now extinct, and the only living genus Neotrigonia.
Paleozoic and Mesozoic trigoniaceans inhabited di- verse environments within epeiric seas. They were physiologically adapted to or tolerant of a wide range of salinities (poikilohaline) as indicated by the com- mon occurrence of their shells with stenohaline forms, such as ammonoids, and in dolomites, in association with evaporites and red beds. In the southern Neuquén Basin, Argentina, the Piedra Pintada Formation yields Liassic trigoniids in association with muddy tuffaceous sandstones that also contain abundant remains of land plants. The trigoniids commonly are found in a variety of sedimentary rocks such as bituminous shales and many kinds of calcarenites, but they are by far most common in fine- to medium grained arenitic sand- stones.
The combination of sedimentological evidence and paleoecological analysis indicates that a large majority of Mesozoic trigoniids inhabited areas of the seafloor no deeper than perhaps 10 or 15 meters (Stanley, 1977). Living populations of Neotrigonia live primarily in deeper waters (150 m) in terrigenous muddy sands, so that the occurrence of the genus in this environment is quite atypical for the family, and may represent a refugium.
The trigoniids are considered suspension feeders, possibly supplementing their diet of living plankton and bacteria with organic detritus (Purchon, 1957).
Hinge teeth of the Trigoniidae are large and distinc- tive, radiating from the beaks far into the interior of the shell. The dentition consists typically in the left valve of a strong median tooth and a weaker one on each side, and in the right valve of two main teeth dividing deep sockets which receive the teeth of the left valve; additional, smaller teeth may be present. The articulating surface of the teeth typically bear very well developed transverse ridges which are interpreted to have a crucial role in the alignment of the valves (Stanley, 1977). Fossil evidence documents the origin of this kind of dentition early in the Mesozoic. Newell and Boyd (1975) suggested that dentition evolved in parallel in several lineages that are recognized by their external morphology. In coincidence with Poulton’s (1979) opinion, however, this view is not tenable, as once established, this specialized dentition remained
1 conservative and stable feature, changing little from the early Mesozoic trigoniids to the living Neotrigonia.
The ligament is external, paravincular and opis- thodetic, showing remarkable conservatism during evolution (Newell and Boyd, 1975). The insertion ar- eas of the anterior and posterior adductor muscles are generally small, and are placed very close to the hinge
teeth. The pallial line is complete, and the ostracum nacreous. As far as known, the original constitution of the shell was wholly aragonitic, and commonly pris- mato-nacreous. The shell microstructure of Neotrigo- nia was studied in detail by Taylor, Kennedy and Hall (1969).
One of the most important features of living Neo- trigonia is its large and muscular foot, which gives species within this genus the ability to jump when threatened (Ansell, 1969; Stanley, 1977, p. 870, his pl. 116, fig. 6-9), showing a strong resemblance to the typical muscular foot of the Cardiidae. The foot and visceral mass are closely appressed to the anterior ad- ductor muscle. Posteriorly, the foot attaches to the shell above the adductor by an elongate and discrete pedal muscle (Tevesz, 1975, p. 333). Though not itself fos- silized, the unusual muscular foot can be traced back through trigoniid phylogeny by indirect means because of its coadaptative relationship to certain skeletal fea- tures (Stanley, 1970, 1977).
Although Cox (1969) stated that the Trigoniidae were non-byssate, contrary to the view of Lycett (1870), a study by Gould (1969) on the non-functional byssal apparatus of Neotrigonia margaritacea (Lamarck) con- cluded that this system functions in juveniles only. Gould therefore dismissed previous arguments that this is a vestigial organ reduced from an hypothetical bys- sate adult ancestor. Supporting Gould’s assertion, in the collection of Trigoniidae from Argentina there are some examples of trigoniids with possible byssal slits, e.g., T. carinata (see Weaver, 1931), T. aliexpandita Leanza and Garate (1983) and some species of Stein- manella (see Leanza and Garate, 1987). Judging by their functional morphologies (Kauffman et al., in press), these species are presumed to have possessed an active bysal apparatus, at least as juveniles.
GEOLOGICAL SETTING OF THE TRIGONIID-BEARING STRATA IN WEST-CENTRAL ARGENTINA
The Neuquén Basin of west central Argentina is fa- mous for its well exposed Mesozoic sediments; in this area up to 6000 m of marine and continental deposits accumulated in a typical back-arc setting. The basin expands toward the eastern foreland forming a large embayment in which different sedimentary cycles of lowermost Jurassic to uppermost Cretaceous age can be recognized. Text-figure 2 shows, in simplified form, the stratigraphic terms used in this paper from the Hettangian to the Maastrichtian in the Neuquén Basin, including the trigoniid-bearing formational units. The oldest marine deposits belong to the Cuyo Group, which is represented by a system of marine, transitional and continental sediments deposited between the Intra- liassic and Intracallovian tectonic episodes. During the
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 9
Pliensbachian, deposition of near-shore marine tuffa- ceous sediments (Piedra Pintada Formation) occurred in southern Neuquén and silicified limestones and tuffs (Chachil Formation) in central Neuquén. During the Toarcian to Aalenian, thick, mostly anoxic shales (Los Molles Formation) were deposited, from which no tri- goniids have been recovered. Therefore the Toarcian extinction event could not be analyzed from the point of view of trigoniid evolution in this region.
A subsequent gradual fall of sea level is indicated by the presence of shore-face arenaceous sediments with several well developed hardgound tops containing abundant trigoniids (Lajas Formation). This unit ex- tends from the Lower Bajocian to the early Bathonian, depending on the area considered. The regression reaches its maximum expression with the accumula- tion, during the early Callovian, of a redbed facies (Challaco Formation), but again no trigoniid-bearing strata have been recorded in this sequence. After the Intermalmic tectonic episode took place, the wide- spread marine transgression of the Mendoza Group, ranging in age from Kimmeridgian s.s. to early Bar- remian occurred. The Mendoza Group extends widely from southern Neuquén to southern Mendoza Prov- inces, and contains several formational units with abundant trigoniids (Tordillo, Vaca Muerta, Picun Leufu, Mulichinco, and Agrio Formations). The Ray- oso Group follows conformably, ranging in age from Hauterivian-Barremian to Aptian-Albian. The Pata- gonidic tectonic episode broke for the first time the connection of this region of Neuquén with the Pacific, and extensive continental dinosaur-bearing strata of the Neuquén Group were deposited. The last Mesozoic marine transgression connects the Atlantic with the Pacific through the Malargue Group. In the shallow marine Maastrichtian sediments (Jagiel Formation) some important trigoniid species are present. The Cen- omanian/Turonian extinction event could not be an- alyzed in this study, because in west-central Argentina thick continental dinosaur-bearing deposits of the Ne- uquén Group were deposited during that time.
TEMPORAL DISTRIBUTION OF TRIGONIID BIVALVES IN WEST-CENTRAL ARGENTINA
LOWER JURASSIC SPECIES
Lower Jurassic trigoniid species in west-central Ar- gentina have been described by Burckhardt (1901), Jaworski (1916, 1925, 1926), Groeber (1924), A. F. Leanza (1942), Lambert (1944), Levy (1967a) and Leanza and Garate (1987). In the present paper eight Lower Jurassic (Liassic) species from western central Argentina are described. These are distributed among the genera Groeberella, n. gen., Myophorella, Jawor-
Age Formations Groups PALEOCENE Roca MAASTRICHTIAN Jaguel Malargue CAMPANIAN Aen SANTONIAN Rio Colorado Rfo Neuquen Neuquén Rio Limay
Rayoso Rayoso
Huitrin
Agrlo
Mulichinco
SOOKE
Picun Leufu Mendoza
,
7 te
en
Vaca Muerta
<> Voy
-
tees
Tordillo
BS
Auquilco La Manga Lotena
Challaco
Lajas
Los Molles
Chachil/PPintada
PLIENSBACHIAN
SINEMURIAN
Precuyano
Choiyoi r
Text-figure 2.—Schematic stratigraphic section for the Jurassic and Cretaceous of west-central Argentina.
HETTANGIAN
Choiyoi
skiella, and Frenguelliella. These taxa have been found in the Piedra Pintada Formation (Stipanicic et al., 1978) which is approximately equivalent to the Lower and Upper Pliensbachian Ofapiria neuquensis and Radu- lonectites sosneadensis Zones recently established by Damborenea (in Riccardi, Damborenea and Mancen- ido, 1990); and in the Chachil Formation (Weaver, 1942) which is equivalent to the Pliensbachian “*Fan- ninoceras Zone” as recently established by Riccardi (in Riccardi, Mancenido and Damborenea, 1990). Groeberella, n. gen. has been erected, with Myopho- ria neuquensis Groeber (1924) as the type species, to differentiate species with only radial ornament from the Triassic Myophorigonia Cox (1952), which is char- acterized by both radial and transverse ornament. The
10 BULLETIN 343
genus is represented by its type species from the Pliens- bachian Piedra Pintada Formation at La Amarga, near Rincon del Aguila, and by Groeberella, sp. indet. from the Middle (now Early) Bajocian Lajas Formation at Barda Negra Sur. The genus Myophorella is repre- sented by its subgenus Myophorella sensu stricto [e.g., Myophorella (M.) araucana (A. F. Leanza), Myopho- rella(M.) catenifera (Hupé) and M. (M.) cf. M. tubercu- lata (Agassiz)]; the last two taxa are cited for the first time in Argentina. The genus Jaworskiella is repre- sented by very well preserved adult and juvenile spec- imens of the type species Jaworskiella burckhardti (Ja- worski). The genus Frenguelliella is represented by the type species Frenguelliella inexspectata (Jaworski) and by a new species named Frenguelliella poultoni, n. sp. which appears to be identical to Frenguelliella, sp. B of Poulton (1979, p. 18, pl. 1, fig. 10) from the early Sinemurian Laberge Group, Yukon Territory, Canada. Myophorella (M.) araucana, M. (M.) catenifera, M. (M.) cf. M. tuberculata, Jaworskiella burckhardti, Frenguelliella inexspectata, and Groeberella neuquen- sis have been found in the near-shore Piedra Pintada Formation. Frenguelliella tapiai, Frenguelliella poul- toni, n. sp. and also Myophorella (M.) catenifera are found in the Chachil Formation (Weaver, 1942).
MIDDLE JURASSIC SPECIES
The first description of a trigoniid species in west- central Argentina was made by Gottsche (1878) from Middle Jurassic strata at the Espinacito Pass region in the High Cordillera de Los Andes, followed by work of Tornquist (1898) and Behrendsen (1891-1892). In this century Middle Jurassic trigoniid species have been described by Weaver (1931), Lambert (1944), Leanza and Garate (1983, 1985, 1986, 1987) and Leanza, Pé- rez and Reyes (1987). The present study provides the description of 21 Middle Jurassic trigoniid species dis- tributed among eleven genera and subgenera, all of which have been found in the Lajas Formation (Weav- er, 1931). This unit outcrops in the southern part of the Neuquén Basin and is represented by a well de- veloped shoreface unit characterized by fine- to coarse- grained sandstones. This facies was very favorable to habitation by trigoniid bivalves, and reflects a number of marine oscillations belonging to eustatic fourth or- der cycles. In a previous paper (Leanza and Garate, 1987) the author considered the specimens from Los Pozones and Covunco Pavia to range between Middle to early Callovian. According to its ammonite content (Westermann and Riccardi, 1985, p. 12, fig. 3), how- ever, the age of the Lajas Formation in these localities ranges from the Early Bajocian to the Early Bathonian, and is approximately equivalent to the Emiliea giebeli to the Cadomites—Tulitidae Assemblage Zones (Ric- cardi, Westermann and Damborenea, 1990).
The following trigoniid genera are present in the Middle Jurassic Lajas Formation: Groeberella, n. gen., Frenguelliella, Trigonia, Neuquenitrigonia, Vaugonia, Andivaugonia, n. gen., Myophorella (Myophorella), Myophorella (Promyophorella), Scaphorella, Scapho- trigonia and Anditrigonia (Eoanditrigonia). Groeber- ella is represented by a single undetermined Early Ba- jocian species at Barda Negra Sur. Although the poor preservation of the specimen precludes any further tax- onomic determination, it has a relatively small size and thin shell in comparison with the Pliensbachian G. neuquensis (Groeber). Frenguelliella is represented by a new Early Bajocian species, F. perezreyesi, which is characterized by small size and relatively flat and transversely costate area. The genus 7rigonia is well represented at several localities from the Early Bajo- cian to the Middle Bathonian by Trigonia corderoi Lambert, 7rigonia mollesensis Lambert, Trigonia den- sestriata Behrendsen, and the new species Trigonia losadai from Los Pozones which shows close affinities with the group of Trigonia costata Agassiz. Neuqueni- trigonia 1s represented in Barda Negra Sur by some fragmentary specimens belonging to its type species N. huenickeni. The genus Vaugonia is represented by two typical elongated Vaugoniinae species: V. rectangularis (Gottsche, 1878) and V. chunumayensis (Jaworski), both occurring in association at Barda Negra Sur. The genus Andivaugonia, n. gen. has been erected with “Trigonia”’ radixscripta Lambert as the type species in order to group somewhat large and inflated species characterized by a non- to poorly developed marginal carina, and an area that is usually smooth or orna- mented only by growth lines. This new genus consti- tutes a homogeneous stock including Andivaugonia ra- dixscripta (Lambert), Andivaugonia covuncoensis (Lambert), Andivaugonia fuenzalidai (Reyes and Pé- rez) and Andivaugonia lissocostata (Reyes and Pérez); the last two species were originally described from the Middle Jurassic of Chile, and are recorded herein for the first time in Argentina at the localities of Chacaico and Fortin 12 de Mayo. The genus Myophorella is rep- resented by the subgenus Myophorella (Myophorella), with the single species M/. (/.) argentinica (Jaworsk1), and by the subgenus Myophorella (Promyophorella) containing M. (P.) praescabroidea (Jaworski). Both oc- cur in association at the Early Bajocian locality of Bar- da Negra Sur. This last species is considered as the Jurassic ancestor of the Upper Jurassic and Cretaceous Pterotrigoniinae. The genus Scaphorella is well docu- mented by Scaphorella leanzai (Lambert), Scaphorella kruusei Leanza and Garate, and by the new species Scaphorella camachoi; the last species is very similar in size and shape to Trigonellina Parnes (1981), but the shell area exhibits transverse instead of radial cos- tellae. The subgenus Eoanditrigonia, n. subgen., based
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 11
on Anditrigonia keideli (Weaver), is present at the lo- cality of Los Pozones.
UPPER JURASSIC SPECIES
Upper Jurassic trigoniids in west-central Argentina have been described by Behrendsen (1892), Burck- hardt (1900a, 1900b, 1903), Haupt (1907), Douville (1910), Weaver (1931), A. F. Leanza (1941), Lambert (1944), Marinelarena (1959), Levy (1967c) and Leanza and Garate (1987). The present study treats 21 species and one subspecies of Upper Jurassic (Kimmeridgian to Upper Tithonian) Trigoniidae which occur in the Mendoza Group. The Kimmeridgian Tordillo For- mation (Groeber, 1946), yields trigoniids near Laguna Miranda and Los Catutos, Lambertrigonia pichimon- colensis (Lambert) and Trigonia mirandaensis Lam- bert. Both species occur in association in coarse-grained to conglomeratic, brown sandstones. The remaining 19 species and one subspecies have been found in Mid- dle and Upper Tithonian strata, namely in shoreface facies of the Carrin Cura (Leanza, Marchese and Riggi, 1977) and Pictin Leufi (Leanza, 1973) formations. These units interfinger with shales and marls of the Vaca Muerta Formation (Weaver, 1931). In this study the genera and subgenera Trigonia, Anditrigonia, An- tutrigonia, Rutitrigonia, Steinmanella (Splenditrigo- nia), Myophorella (Myophorella), Myophorella (Pro- myophorella), Myophorella (Haidaia), Pterotrigonia (Rinetrigonia), Pterotrigonia (Scabrotrigonia), and Pterotrigonia (Notoscabrotrigonia) have been recog- nized. The genus 7rigonia is represented by 7. carinata Agassiz, T. levyi,n. sp., T. fortinensis Lambert and T., sp. juv. indet. Anditrigonia is represented by the sub- genus Anditrigonia s.s., with A. (A.) eximia (Philippi), A. (A.) carrincurensis (A. F. Leanza), A. (A.) lamberti Levy, A. (A.), sp. juv. indet., and A. (4.) eximia tes- selicaudata, n. ssp. Antutrigonia is represented by A. frenguellii (Marinfelarena) and A. groeberi (Weaver). The genus Steinmanella is represented by the subgenus Splenditrigonia, n. subgen. which groups an homoge- neous stock composed by S. (Sp/.) splendida (A. F. Leanza), S. (Spl.) erycina (Philippi) and S. (Sp/.) haupti (Lambert). The genus Myophorella is represented by Myophorella (M.) schulzi, n. sp., the subgenus Pro- myophorella by M. (P.) hillebrandti Reyes and Pérez, and by the subgenus Haidaia containing the new species M. (A) elguetai. Rutitrigonia appears in west- central Argentina for the first time in the Upper Ti- thonian and is represented by an undetermined juve- nile species from the Picin Leufi Formation at Cerro Caracoles. The genus Prerotrigonia appears for the first time in the Upper Tithonian, represented by the sub- genera Scabrotrigonia, Rinetrigonia, and Notoscabro- trigonia. Scabrotrigonia is represented by P. (Scabro- trigonia) transatlantica (Behrendsen), redescribed here
for the first time since the original description in 1892, and by P. (Rinetrigonia), sp. juv. indet. The subgenus Notoscabrotrigonia is represented by P. (Notoscabro- trigonia) coheni, n. sp. The age of these taxa has been precisely determined by co-occurring ammonites in the Aulacosphinctes proximus, Windhauseniceras internis- pinosum (Middle Tithonian), Corongoceras alternans, and Substeueroceras koeneni (Upper Tithonian) Zones (Leanza, in Riccardi, Leanza and Volkheimer, 1990).
LOWER CRETACEOUS SPECIES
Lower Cretaceous trigoniid species have been de- scribed in west-central Argentina by Behrendsen (1892), Burckhardt (1900a, 1900b, 1903), Weaver (1931), Lambert (1944), Leanza (1985), Camacho and Olivero (1985) and Leanza and Garate (1987). In the present paper, 21 species of Lower Cretaceous age (Berriasian to Hauterivian, and probably also Early Barremian) are described. The species are confined to the Mendoza Group (Groeber, 1946), and are present in shoreface facies and/or on the top of hardgrounds of the Vaca Muerta, Mulichinco and Agrio formations (Weaver, 1931). The recorded Lower Cretaceous genera and sub- genera are mainly Steinmanella (Transitrigonia), Steinmanella (Macrotrigonia), Steinmanella (Splen- ditrigonia), Virgotrigonia, Antutrigonia, Trigonia, Quoiecchia, Syrotrigonia, Rutitrigonia, Anditrigonia, Pterotrigonia (Pterotrigonia), Myophorella (Myopho- rella), Myophorella(Promyophorella) and Myophorella (Haidaia). The genus Steinmanella is present in the Berriasian, Valanginian and Hauterivian, and proba- bly the Early Barremian. The genera Virgotrigonia and Pterotrigonia have been found in the Berriasian, whereas Antutrigonia has been found in the latest Ber- riasian/earliest Valanginian. 7Trigonia, Myophorella, Quoiecchia, Rutitrigonia, Anditrigonia and Syrotrigo- nia are clearly dominant in the Hauterivian.
Berriasian species are represented by Virgotrigonia hugoi (Leanza) formerly the type species of the genus Maputrigonia, and by Pterotrigonia (Pterotrigonia) al- iformis (Parkinson). Both species occur in association at Mallin Quemado in the Argentiniceras noduliferum Zone. In addition, a description of Steinmanella (Tran- sitrigonia) neuquensis (Burckhardt) from Trahuncura is presented. Late Berriasian/Early Valanginian species include Antutrigonia opistolophophora (Lambert) from the Mulichinco Formation at Mallin Quemado in the Spiticeras damesi/Neocomites wichmanni Zones, and Steinmanella (Transitrigonia) quintucoensis (Weaver) and Steinmanella (Splenditrigonia) splendida (A. F. Leanza). Both species occur in association at Trahun- cura in the same ammonite assemblage. The Valan- ginian Steinmanella (Transitrigonia) steinmanni (Phi- lipp1) from the Mulichinco Formation at Puerta Curaco in the Olcostephanus curacoensis Zone is also de-
1 BULLETIN 343
scribed. Steinmanella (Transitrigonia) transitoria (Steinmann) is present in the Agrio Formation in the Late Valanginian/Early Hauterivian locality of Cerro Pitrén, whereas Lower Hauterivian species are de- scribed from Pichaihue Abajo, including Syrotrigonia brocardoi, n. sp. and Quoiecchia sigeli Leanza and Gar- ate. Lower to Middle Hauterivian species are abundant and diverse. They are mostly found in the Agrio For- mation of the Cerro Mesa and Cerro Negro (Covunco) areas. The list includes Steinmanella (Transitrigonia) raimondii (Lisson), Myophorella (Promyophorella) garatei Leanza, Myophorella (Haidaia) volkheimeri Leanza and Garate, Trigonia wiedmanni Leanza and Garate, T. angustecostata Behrendsen, T. aliexpandita Leanza and Garate, Rutitrigonia agrioensis (Weaver), Rutitrigonia kauffmani, n. sp., and undetermined spe- cies of Anditrigonia from the Arenal of Las Lajas. These species occur in the Lyticoceras pseudoregale and Hol- coptychites neuquensis Zones. In light of the revision of Pterotrigoniinae by Cooper (1989), the Hauterivian species coihuicoensis of Weaver, formerly thought to be a representative of Myophorella (Myophorella), is herein placed in the subgenus Pterotrigonia (Rinetri- gonia). Pterotrigonia (Rinetrigonia) coihuicoensis (Weaver) ranges throughout the Hauterivian, and probably the Early Barremian, whilst Steinmanella (Macrotrigonia) vacaensis (Weaver) is found in the Up- per Hauterivian Crioceratites (Paracrioceras) andinus Zone.
UPPER CRETACEOUS SPECIES
Upper Cretaceous trigoniid species have been de- scribed in west-central Argentina, including Rio Negro and La Pampa Provinces, by Levy (1967b), Camacho (1967, 1968), Farinati, Quattrocchio and Labudia (1987) and Leanza and Casadio (1991). The species are usually found in the Maastrichtian Jaguel For- mation (Windhausen, 1914) and equivalents, mostly in association with Eubaculites argentinicus (Weaver). The present study describes three Upper Cretaceous trigoniid species. Pacitrigonia sobrali Leanza and Cas- adio and Austrotrigonia pampeana Leanza and Casa- dio are from the Jagiiel Formation at the locality of Barda Baya, La Pampa Province. The remaining spe- cies Pterotrigonia (Rinetrigonia) windhauseniana (Wilckens), was found by the authors in the Jagiel Formation at the locality of Cerro Villegas in the north-
astern part of the Neuquén Province.
SPECIES DURATIONS OF THE FAMILY TRIGONIIDAE IN WEST-CENTRAL ARGENTINA
Each of the 74 described Jurassic and Cretaceous trigoniid species and subspecies have been referred to known ammonite zones, and in the localities in which
cephalopods are not present, bivalve zonations have been used for reference. For the Lower Jurassic the bivalve zonation by Damborenea (in Riccardi, Dam- borenea and Mancenido, 1990), and the ammonite zo- nation by Riccardi (in Riccardi, Damborenea and Mancenido, 1990) have been used. For the Middle Jurassic the ammonite zonation proposed by Riccardi (in Riccardi, Westermann and Damborenea, 1990) was utilized. The Upper Jurassic trigoniid occurrences in west-central Argentina were matched with the am- monite zones proposed by Leanza (in Riccardi, Leanza and Volkheimer, 1990), whereas the Lower Cretaceous were correlated with the ammonite zonation published by Leanza (1981a). The Upper Cretaceous trigoniid occurrences occur within the Maastrichtian Eubacu- lites Assemblage Zone (see Riccardi, 1984).
In Table 1 the vertical range of each species from its first to its last occurrence has been plotted against the linear time scale in millions of years before present of Haq et al. (1988), and the duration of species ranges calculated. At the specific level, 27% of the trigoniid species had durations of approximately one million years. The average species duration for all described trigoniids was approximately 3.8 million years. It is worth noting that 69% of the described species have durations of one to three million years, and the re- maining 31% have longevities from three to 17.5 mil- lion years.
For practical purposes, the trigoniids discussed in this paper have been divided into four groups, as fol- lows:
1) Longevities up to one million year: 20 species (27%).
Groeberella, sp. indet., Trigonia densestriata, Tri- gonia, sp. juv. indet., Trigonia fortinensis, Neuqueni- trigonia huenickeni, Frenguelliella perezreyesi, My- ophorella (Myophorella) argentinica, M. (M.) schulzi, M. (Promyophorella) praescabroidea, M. (Haidaia) el- guetai, Scaphotrigonia rierafonti, Scaphorella cama- choi, S. kruusei, Steinmanella (Splenditrigonia) ery- cina, Vaugonia chunumayensis, V. rectangularis, Andivaugonia lissocostata, Syrotrigonia brocardoi, Pterotrigonia (Rinetrigonia), sp. juv. indet., and Quoiecchia sigeli.
2) Longevities from one to three million years: 30 species and | subspecies (42%).
Trigonia levyi, T. aliexpandita, T. wiedmanni, T. angustecostata, T. mirandaensis, Frenguelliella tapiai, F. poultoni, Myophorella (Promyophorella) hillebrand- ti, M. (P.) garatei, M. (Haidaia) volkheimeri, Stein- manella (Macrotrigonia) vacaensis, S. (Transitrigonia) raimondii, Anditrigonia (Anditrigonia) carrincurensis, A. (A.) lamberti, A. (A.), sp. indet., A. (4.), sp. juv. indet., A. (A4.) eximia tesselicaudata, Antutrigonia op-
Table 1.—Stratigraphic distribution of Jurassic and Cretaceous trigoniid bivalves in west-central Argentina, in stratigraphic order.
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snodJoVvl3ayo OISSVYNr
14 BULLETIN 343
istolophophora, A. frenguellii, A. groeberi, Lambertri- gonia pichimoncolensis, Virgotrigonia hugoi, Rutitri- gonia agrioensis, R. kauffmani, R. sp. juv. indet., Pterotrigonia (Notoscabrotrigonia) coheni, P. (Scabro- trigonia) transatlantica, P.(Rinetrigonia) windhausen- iana, P. (Pterotrigonia) aliformis, Austrotrigonia pam- peana, and Pacitrigonia sobrali.
3) Longevities from three to 11.5 million years: 21 species (29%).
Steinmanella (Transitrigonia) transitoria, S. (T.) quintucoensis, S. (T.) steinmanni, S. (T.) neuquensis, S. (Splenditrigonia) haupti, Pterotrigonia (Rinetrigon- ia) coihuicoensis, Anditrigonia (Anditrigonia) eximia, A. (Eoanditrigonia) keideli, Trigonia corderoi, T. mol- lesensis, T. losadai, Andivaugonia radixscripta, A. co- vuncoensis, A. fuenzalidai, Groeberella neuquensis, Frenguelliella inexspectata, Jaworskiella burckhardti, Myophorella (Myophorella) araucana, M. (M.) caten- ifera, M.(M.) cf. tuberculata, and Scaphorella leanzai.
4) Longevities from 11.5 to 17.5 million years: two species (2%).
Steinmanella (Splenditrigonia) splendida and Tri- gonia carinata.
The maximum species longevity (17.5 million years) recorded is for Trigonia carinata Agassiz, a taxon which ranges from the Upper Tithonian to the Middle Hau- terivian, although a diminution in size has been noted for the Hauterivian representatives of the species. The second most long-lived species (15.5 million years) is Steinmanella (Splenditrigonia) splendida which ranges from the Lower Tithonian to the Early Valanginian of Argentina and Chile.
ACKNOWLEDGEMENTS
The John Simon Guggenheim Memorial Founda- tion supported this study through a Research Fellow- ship to the senior author which was held in Department of Geological Sciences of the University of Colorado at Boulder, U. S. A. The Guggenhiem Foundation also contributed to the printing costs of this paper. The Secretaria de Mineria and the Consejo Nacional de Investigaciones Cientificas y Técnicas (CONICET) of Argentina authorized the tenure of the Fellowship in the United States of America. The author is particu- larly grateful to Dr. Erle G. Kauffman (University of Colorado, Boulder) for his critical comments on the
ianuscript and improvement of the English text, and for his kind assistance and stimulating discussions with
he author during his stay in Boulder. Terry P. Poulton
(Calgary), Cathryn R. Newton (Syracuse) and Peter R. Hoover (Ithaca) acted as kind reviewers. Thanks to their precise observations, the presentation of this monograph has been significantly improved.
Special thanks are due, in different stages of the prep- aration of this monograph, to A. C. Riccardi and S. E. Damborenea (La Plata), C. A. Hugo, M. A. Uliana, L. Legarreta, C. Gulisano, W. Volkheimer (Buenos Ai- res), U. Rosenfeld (Minster), J. Wiedmann (Tibing- en), T. P. Poulton (Canada), M. R. A. Thompson (En- gland), E. Pérez d’Angelo (Santiago), and T. Villamil (Bogota).
Acknowledgements are due also to persons who in one way or another supported the activities of the Mu- seum Juan Olsacher in Zapala, as follows: Eliseo Se- pulveda, Klauss Eppinger, Marzio Smareglia, Jorge Diz, Eduardo Jawerbaum, Carlos Zabala, Jorge Preloran, Daniel Ghedin, Kurt Hirt von Sigel, Segundo Vasquez, Domingo and Ramona Elgueta, Luis Ardanaz, Juan Domingo Soto, Pablo di Laudo, Juan Carlos Vega, Roberto Lépez, Chiyomi Masuda de Nishimoto, Guil- lermo and Gabriel Nicolossi, Gustavo Azta, Daniel Sanchez, Daniel Fernandez Ramphastos, Enrique Schulz, Francisco Romero, Juan Mario Raone, Héctor and Hugo Marichelar, Laura Ibanez, Heraclio Osvaldo Ortiz, Gustavo Atienza, Luis and Jorge Demetrio, San- tiago Jara, Maria Soledad Azar, Enrique Riera Font, Marcelo Martinez, Roberto Suarez, Oscar Encina, Ed- uardo Mundano, Rodolfo Zimmt, Roberto P. and Te- resa H. Garate, Richard Cohen and Eduardo J. Rebord. Thanks also to Sergio Eduardo and Juan Rafael Cocca for the permanent improvement of the Museum’s col- lections.
INTRODUCTION TO SYSTEMATIC PALEONTOLOGY
PHILOSOPHICAL CONSIDERATIONS
Evolution of trigoniids in each geographic realm oc- curred mostly in isolation for long periods of time, punctuated by episodic regional interchange at maxi- mum flooding episodes at times of sea level rise. Al- though there are general signatures between trigoniids of different regions that can be traced at the generic level, species are almost invariably endemic. In order to clarify the great radiation of the Trigoniacea during the Mesozoic, and contrary to the view of Cox (1969), a non-conservative taxonomy is used in the classifi- cation of the trigoniid faunas of west-central Argentina. Although the views presented here are in agreement with those of Cooper (1991), who has recently revised the classification of the order Trigonioidea, his paper appeared almost simultaneously with the completion of this manuscript. Therefore his taxonomy higher than subfamily level has not been adopted, as this needs still further analysis.
The philosophy used by the author in taxonomic determinations in this paper was to consider the most important characteristics of the trigoniid shell, namely:
TRIGONUD BIVALVES OF ARGENTINA: LEANZA
tematic order.
ina, in sys
Table 2.—Stratigraphic distribution of Jurassic and Cretaceous trigoniid bivalves in west-central Argent
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suoynod oyayjjenbuedy — — ~|~ 4—~—~ 4 — Doj2adxAU) OpJaljjanbualy Jojdoj oyayjanbuasy __ __ jueyqueny oluobsyjuanbnay — oyojso2ysnbuo ojuob/s, — JuuowpesM 0/u06/4/ O¢puogB)/0 O/U0b 11, S/SUBUNIOJ OJUOBIAY _
yepul ant ds 0/u0b/411 Janay o1wob/ 41 Djoulso2 o1uobIsy
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-r- 4apul as ojjesaqaos9 ~~~ + —~1~— SISGANbNAU 0//818G8019 — -— ~ +--+ ——E + a pe ae en ny ite T a o on _— @o ow nn o — wo 256 6 DD| aD sffeauanse wo roe. oS =s 1 TF ae oti a a Hi o. V, ad va | | = — c = © = c| elic = = S = o ra =I sols = c S 2) 28es4 | se/e/ 5] 83) siS| £]5]/ 5] 5] = ° ©] Cleolg lee sql SS} ec} 2) 2)—| 2 110.0) ce jc) 2; ¢ o|> CRI = s oO alses§ & joa®| c|—| of Lia) 2] e) c/o] & oO ° = flo5| o| &] cE} ofS] £] Oo] © Bejesicl ga] 2) co] Se} SiS| =| S) =] oo] © =| Seed = Ss2itistasacieizizici=z =| 0 OF < Sat) >|a F<) 5/6 ala) <i ja 1 UE J:
16
(1) size, (2) shape, (3) convexity, (4) direction of coiling of the umbo, and (5) nature of ornamentation on the outer surface. This last feature includes mainly strength, orientation and ontogenetic changes in the nature of the costae and carinae (cf., Poulton, 1979).
The dentition and other internal features of the tri- goniids are conservative characters showing little change from the origin of the group to the present. Taxonomic determinations in this paper thus have been based largely upon external shell shape and ornamen- tation, of which the surface features of the area are the most relevant to the distinction of different genera and subgenera within the family (Perez and Reyes, 1987).
A good example of what the author interprets as useful generic level characteristics is provided by mem- bers of the subfamily Anditrigoniinae. Although the flank ornamentation displays more or less similar pat- terns in different genera, the area of Anditrigonia has transverse costellae near the umbo and a smooth distal area, whereas Paranditrigonia bears faint radial cos- tellae over the entire area. Antutrigonia bears trans- verse costellae in the whole area, whilst Virgotrigonia shows transverse costellae near the umbo and radial costellae in the distal part of the area. Similarly, mar- ginal carinae may be absent (Antutrigonia), only de- fined in the umbonal region (Anditrigonia, Parandi- trigonia), or continuous along the whole length of the shell (Virgotrigonia, Lambertrigonia).
Subgeneric interpretation may be exemplified by members of the genus Myophorella, in which the sub- genus Myophorella sensu stricto bears tuberculated costae, whilst the subgenus Promyophorella displays beaded or almost smooth costae, and Haidaia shows flank costae with crenulations in their ventral parts. In general, escutcheon, area and marginal carinae con- serve similar patterns. The subgenus Foanditrigonia, in a similar way, shows on the flanks subconcentric costae forming with the posterior set of costae a ven- trally directed V- or L-shaped inflection. But these pos- terior costae are fewer, thicker and in inverse relation to those of Anditrigonia sensu stricto.
Concerning the author’s concept of subspecies, 4n- ditrigonia (A.) eximia tesselicaudata n. subsp. serves as an example. It displays a not very elongate shell shape and a comparatively less convex anterior margin in comparison with Anditrigonia eximia, but these dif- ferences fall in the intraspecific variability of this spe- cies, already demonstrated by Lambert (1944) and Pe- rez and Reyes (1983). Nevertheless, the reticulate ornamentation on the posterior flank resulting from the intersection of subvertical costae with subhorizon- tal grooves is interpreted as a secondary character of subspecific value.
The key points followed in this paper for taxonomic purposes may be summarized as follows:
BULLETIN 343
Subfamily level: general trends of the outer shell, or- namentation of escutcheon, area and flank;
Generic level: ornamentation of escutcheon, area and marginal carina;
Subgeneric level: ornamentation of flank, mainly cos- tae;
Species level: size, shape, convexity of shell, nature of ornamentation;
Subspecies level: minor differences in flank ornamen- tation not falling beyond the intraspecific variability of a species.
Each genus treated here has a diagnosis based on the author’s own observations. References are also given to previous authors who may have made different di- agnoses of a given genus. Temporal and geographic distribution are given for each genus, and age assign- ments for units that have yielded trigoniids are doc- umented briefly.
The phylogeny of trigoniids is complex and, in the view of the author, still poorly understood. Kobayashi (1954), Kobayashi and Mori (1955), Saveliev (1958) and Nakano (1960), among others, made attempts to establish some phylogenetic trends among the Trigon- iacea, but most of them resulted in misinterpretations and confusion, due in large part to lack of taxonomic certainty. It is not the purpose of this paper to promote particular phylogenetic interpretations, but the refined taxonomy developed here may provide a basis for fu- ture discussions.
TERMINOLOGY
The terminology used in the systematic descriptions is in general agreement with the Trigoniid Glossary of Terms by Kauffman, Leanza and Villamil (in prepa- ration). The following original trigoniid morphological terms have been commonly used (see Text-figure 3), and are here described with the permission of the above cited authors:
Antecarinal sulcus/groove: A narrow radial depression located at the posterior edge of the flank, just anterior to the marginal carina, extending from the umbo to the ventral-posterior junction.
Anterior margin: The margin of the shell extending anteriorly from the beaks to the beginning of the ventral margin.
Area: Commonly triangular-shaped dorsal-posterior portion of the shell surface bounded by the marginal carina, the posterior margin and the escutcheon ca- rina. The area commonly bears distinct ornamen- tation important to the differentiation of different genera within the family.
Beak: The sharply to bluntly pointed dorsal tip of the umbo, projecting above the hinge margin.
TRIGONID BIVALVES OF ARGENTINA: LEANZA 17
Costa: A moderately prominent elevated ornamental feature of the outer shell surface that may be oriented radially, obliquely or concentrically. Same as “rib” in previous literature.
Costella: A small and narrow, elevated ornamental feature of the shell, usually present in the area and/ or escutcheon, which is normally radial, as in 77i- gonia, but may be oblique, as in Apiotrigonia, or concentric, as in Frenguelliella. Same as “‘riblet” in previous literature.
Dorsal margin: The margin of the shell extending from the beaks to the dorsoposterior junction.
Dorsoposterior junction: The normally angular, pre- dominantly obtuse, intersection between the dorsal and posterior margins, forming the dorsoposterior angle.
Escutcheon: A dorsal surface on either side of the lig- amental groove extending posteriorly from the beaks. The escutcheon is commonly bounded by the es- cutcheon carina in each valve. The shape may be highly excavated to strongly convex, as in Trigonia aliexpandita. The escutcheon surface may be smooth, or usually ornamented by radial, oblique, or con- centric growth lines or costellae, but exceptionally it can bear transverse costae, as in Neuquenitrigonia.
Escutcheon carina: A narrow elevated ridge or keel extending posteriorly from the beak along the dorso- lateral margins of the escutcheon and forming a dis- crete border.
Flank: The entire valve surface between the anterior and ventral margins and the marginal carina. The term flank is equivalent to “disk” of the bivalve literature, but is more used by trigoniud workers. The ornamentation of this surface is important in the distinction of different taxa within the family.
Intercostal space: Concave depression between adja- cent costae.
Ligamental fossette: A narrow depressed lunate plat- form extending posteriorly from the beak along the dorsal margin, within the escutcheon, and serving for attachment of ligament.
Lunule: A concave depression along the dorsoanterior margin below the beaks.
Marginal carina: A prominent fold or subangular ridge that extends from the beak and umbo to the ven- troposterior junction. This ornamental feature is im- portant to the differentiation of taxa within the fam- ily. It may be smooth, beaded or tuberculate, and strongly defined on the whole shell or sharply defined only in the umbonal region, becoming distally in- distinct or completely absent. Same as ‘‘umbonal ridge”’ in bivalve literature.
Median carina/groove/sulcus: A narrow radial ridge, fold or depression that divides the area into inner and outer parts and extends from the beak or umbo
DORSAL Ligamental fossette Marginal carina Lunute Commisure Plane WIDTH Median carina
t_----=3 Escutcheon carina LATERAL Beak DORSAL Fo Manone a MARGIN—*
mbo Escutcheon ] \ | Dorsoposterior Sa | Z junction Costae Ss ek Ice ANTERIOR YQ ahi S\ posterior ® MARGIN Me PACA MR MARGIN Ty or, 22 5 a5 —\ 'rF 777-\\ Ventroposterior ; | junction oe. | Intercostal! |S Antecarinal spaces | Marginal , | Sulcus
caring | | SVEN A al MARGIN
LENG ——————
dib. Ines Lopez Pardo
Text-figure 3.—Morphological terminology used to describe tri- goniid bivalves in this paper.
to the mid-posterior margin. In cases in which the area is divided into two asymmetrical parts, the term submedian carina/groove/sulcus is used.
Postcarinal sulcus/groove: A radial depression located on the inner area, just posterior to the marginal ca- rina.
Posterior margin: Margin of the shell between the dor- soposterior junction and the ventroposterior junc- tion, and defining the distal edge of the area.
Umbo: The dorsal portion of the valve just below the beaks, marking the inflation and curvature at the growth axis in many trigoniids. This region may be demarcated ventrally by a change from juvenile/ear- ly adult to normal adult ornamentation.
Ventral margin: The margin of the valve between the ventroposterior and anterior-costal junctions.
Ventroposterior junction: The normally angular inter- section between the posterior and ventral margins, forming the ventroposterior angle.
MEASUREMENTS AND ABBREVIATIONS
The trigoniid sizes are in accordance with the con- ventional scale of Saveliev (1958), as follows: =< 10 mm, very small; 10-20 mm, moderately small; 20-30 mm, small; 30-50 mm, medium size; 50-100 mm, large; and = 100 mm, very large. The following mea- sures have been taken into account, whose definitions have been taken after Kaufmann, Leanza and Villamil (in preparation):
18 BULLETIN 343
Length (L): The horizontal distance between two ver- tical planes perpendicular to the cardinal axis or hinge line. These planes pass through the most anterior and most posterior projections of the shell margin when the cardinal axis is oriented horontally.
Height (H): The perpendicular distance between two planes parallel to the cardinal axis. The planes pass through the most dorsally and ventrally projecting portions of the shell when oriented with the cardinal axis horizontal. These points are normally the beak and the mid-ventral margin.
Width (W): The distance taken perpendicular to the commissural plane and extending to the point of maximum inflation of one valve.
Ratio H/L: Ratio between the height and the length of a single valve.
Ratio W/L: Ratio Between the width and length of a single valve.
ABBREVIATIONS OF REPOSITORY INSTITUTIONS
MOZ - Museo Juan Olsacher. Direccion General de Mineria de la Provincia del Neuquén. Olascoaga 421. 8340 Zapala, Neuquén, Argentina.
GHUNLPam - Catedra de Geologia Historica de la Universidad Nacional de La Pampa. Uruguay 151. 6300 Santa Rosa. La Pampa, Argentina.
SGN -Servico Geologico Nacional. Av. Santa Fe 1548. 1060 Buenos Aires. Argentina.
SYSTEMATICS Order TRIGONIOIDA Dall, 1889 Suborder TRIGONIINA Dall, 1889 Superfamily TRIGONIACEA Lamarck, 1819 Family TRIGONIIDAE Lamarck, 1819
Subfamily MINETRIGONIINAE Kobayashi, 1954
Genus GROEBERELLA, new genus
Type species.— Myophoria neuquensis Groeber, 1924, Liassic (Pliensbachian), Neuquén, Argentina.
Diagnosis.—Shell of large size, inequivalve. Um- bones opisthogyrous. Flank ornamented with radial plicae extending from the umbonal region to the ven- tral margin. Marginal carina of the same strength as the flank plicae. Area smooth. Escutcheon narrow and smooth. Concentric or transverse costae absent, growth lines weak.
Distribution.—Lower Jurassic (Pliensbachian) to Middle Jurassic (Bajocian). Argentina and Chile.
Etymology.—This genus is dedicated to the memory of the outstanding geologist Dr. Pablo Groeber, author of the type species.
Discussion.—Groeber (1924) described Myophoria neuquensis from the Chachil Formation (Weaver, 1942), which he assigned to the Triassic based on the occurrence of this bivalve. Today the associated fauna found in this unit is thought to indicate a Liassic (Pliensbachian) age. Levy (1967a) assigned “MM.” neu- quensis to Myophorigonia Cox, 1952 (type species: My- ophoria paucicostata Jaworski, 1922) but strong dif- ferences with the type species of this genus exist. Damborenea (in Riccardi, Damborenea and Mancen- ido, 1990, p. 89) considered the generic assignment of the neuquensis species of Groeber to Myophorigonia with quotation marks while discussing the age range of this species. The genus Groeberella, n. gen. differs from Myophorigonia Cox in: (1) being of larger size; (2) having a subquadratic instead of subrectangular shell shape; (3) having thicker valves; (4) in the total total absence of transverse or concentric costae; and (5) in the absence of nodes, tubercles, beads or knobs in any part of the shell. This new genus includes, apart from the type species, an Early Bajocian undetermined species which is also described in this paper. C. Newton (written communication, 1991) believes that there may be some specimens of Groeberella from the North American Triassic.
Groeberella, n. gen. is here tentatively included in Minetrigoniinae Kobayashi (1954). This subfamily fluorished in the Permo-Triassic, but some represen- tatives are present in the Lower Jurassic (Hettangian) from Chile (Pérez and Reyes, 1977, p. 19). It might be possible to group this taxon into a new subfamily. The lack of preservation of the internal structures in the Argentine material, however, precludes assessing this possibilty for the time being.
Groeberella neuquensis (Groeber, 1924) Plate 1, figures 2-3
Myophoria neuquensis Groeber, 1924, p. 92, pl. 1, figs. a, b; Wahnish, 1942, p. 59, pl. 6, figs. 3a—c; Levy, 1967a, p. 13.
Description. —Shell large. Strongly inequivalve, with the left valve largest than the right valve. Thick valved (4 mm). Umbones opisthogyrous, situated anteriorly. Dorsal margin short and straight. Dorsoposterior angle slightly obtuse. Posterior margin short. Ventroposteri- or junction rounded. Ventral margin convex, passing abruptly to the almost straight anterior margin. Flank occupying two-thirds of the shell surface, ornamented by two strong radial plicae extending from the umbonal region to the ventral margin. Marginal carina or um- bonal ridge of the same strength as the flank plicae, extending from the beaks to the ventroposterior junc- tion. Area smooth and slightly concave. Escutcheon narrow and smooth, bounded by smooth escutcheon carinae. Concentric weakly defined growth lines best
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 19
developed at the shell margins. No concentric rugae or costae.
Material.—One hypotype specimen, MOZ P4060, a left valve with the ventroposterior part broken, but still preserving its internal mold.
Measurements (in mm).—
Specimen No. 1F H WwW H/L W/L MOZ P4060 51 50 30 0.98 0.58
Remarks.—The differences between Groeberella neuquensis (Groeber) and the type species of the Tn- assic Myophorigonia paucicostata Jaworski (1922) from Pert are the same as for the genus. Groeberella neuquensis differs from the Middle Bajocian Groeber- ella sp. indet. (this paper) in (1) having larger size; (2) having a different shell shape; and (3) having thicker valves.
Age and occurrence.—Pliensbachian, Otapiria neu- quensis and Radulonectites sosneadensis Zones, Piedra Pintada Formation; Cerrito Roth, Canadon de la Pied- ra Pintada (Locality 24), Dept. Collon Cura, Neuquén, Argentina.
Groeberella, species indeterminate Plate 3, figure 16
Myophorigonia, sp. indet. Leanza and Garate, 1987, p. 225, pl. 1, fig. 3.
Description.—This specimen is a fragment of a left valve on which it 1s possible to distinguish an elevated opisthogyrous umbo situated centrally on the valve. The flank ornament consists of two strong radial costae or plicae which radiate from the beaks and extend in a straight line toward the ventral margin. These are crossed by weak concentric growth lines. Area and es- cutcheon not well impressed.
Material.—One (adult ?) fragment , MOZ P1375, of a poorly preserved left valve.
Measurements (in mm).—
Specimen No. IE H WwW H/L W/L MOZ P1375 21 18 8 0.85 0.38
Remarks.—This fragment can be assigned to Groe- berella, n. gen. on the basis of shell shape and the strong radial flank plicae crossed only by weak concentric growth lines, but its poor preservation precludes any finer taxonomic assignment. It differs from Groeberella neuquensis (Groeber) (herein described) by its smaller size and much thinner shell.
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, Neuquén, Argentina.
Subfamily TRIGONIINAE Kobayashi, 1954
Genus TRIGONIA Bruguiére, 1789
Type species.— Venus sulcata Hermann, 1781 (see Crickmay, 1932), Upper Liassic, Alsacia.
Diagnosis.—Trigonal to trigonally ovate. Inequi- valve. Area, flank and escutcheon distinctly separated. Area wide, generally bipartite, with radial or reticu- lated ornament in areas where the radial and transverse costae intersect. Marginal carina prominent, usually tuberculated. Distinct antecarinal groove in left valve and postcarinal groove in right valve. Flank with con- tinuous subconcentric costae on its main part. Costae generally meet the anterior margin at a high angle. Escutcheon smooth, or with transverse to oblique ridg- es (Crickmay, 1932; Cox, 1952).
Distribution.— Middle Triassic to Upper Cretaceous. Cosmopolitan.
Trigonia corderoi Lambert, 1944 Plate 3, figure 11; Plate 4, figures 5, 9; Plate 5, figures 1, 2 Trigonia corderoi Lambert, 1944, p. 366, pl. 4, figs. 1-3; Pérez and
Reyes, 1977, p. 11, pl. 1, figs. 1, 11; Leanza and Garate, 1987, p. 206, pl. 2, figs. 1, 2.
Description.—Shell large, inequivalve. Umbones prominent, opisthogyrous, strongly raised above the hinge line. Dorsal margin concave. Dorsoposterior an- gle obtuse. Posterior margin relatively short. Ventro- posterior angle acute. Ventral margin nearly straight, forming a sharp obtuse angle with the nearly vertical anterior margin. Flank occupying only two-thirds of the shell surface, ornamented with more than 30 equal- ly spaced, prominent, subconcentric costae. Marginal carina well developed; antecarinal sulcus present on the flank of the left valve; postcarinal sulcus occurs in the area of the right valve. Area wide, bipartite, with narrow, radial, beaded costellae and transverse growth lines, divided into two equal parts by a beaded median area carina. Escutcheon lanceolate, excavated, orna- mented only by oblique growth lines, bounded by a well developed, clavate escutcheon carina. Ligamental fossette wide, short and deep.
Material.—Three hypotype specimens: MOZ P0910, complete adult specimen; MOZ P5235, complete adult specimen; MOZ P3022, juvenile complete specimen.
Measurements (in mm).—
Specimen No. IE, H WwW H/L W/L MOZ P0910 82 68 21 0.82 0.25 MOZ P5235 1s) 54 21 0.72 0.28 MOZ P3022 53 45 16 0.84 0.30
Remarks.—Trigonia corderoi Lambert (1944) differs from the associated Trigonia mollesensis Lambert
20 BULLETIN 343
(1944, p. 364, pl. 3, figs. 1-4, pl. 10, fig. 6; described herein) from the Bajocian of Neuquén, Argentina in the following details: (1) its shape is different, char- acterized by a more erect anterior margin which passes evenly to the ventral margin; (2) the flank occupies a proportionally smaller surface of the shell; and (3) it is ornamented by much more sinuous concentric cos- tae. Affinities of J. corderoi Lambert can also be traced to the Jurassic Trigonia bajuranasi Saveliev (1960, pl. 6, figs. la—b) from Mangyschlak, Turkmenistan; but the latter species differs in having more numerous and more arched costae on the flank. Damborenea (in Ric- cardi, Westermann and Damborenea, 1990, p. 118) tentatively considered 7. corderoi Lambert as a junior synonym of 7. stelzneri Gottsche (1878, p. 24, pl. 6, figs. la—d)), a species which has also been found in the Middle Jurassic of Pert (see Cox, 1956, p. 1184, pl. 128, figs. 5-6). Although 7. stelzneri and T. corderoi are species which appear to be rather similar, a re- examination of the Gottsche’s type would be necessary to confirm this. Moreover, Pérez and Reyes (1977, p. 9 and p. 11) have described separately 7. ste/zneri and T. corderoi as valid species from different fossil local- ities in Chile, and Lambert (1944, p. 364, pl. 2, figs. 6-7) reported 7. stelzneri in the same paper in which he founded T. corderoi.
It is highly probable, however, that “7rigonia stelz- neri’> Weaver non Gottsche (Weaver, 1931, p. 240, pl. 20, figs. 103-104) from the Lajas Formation in Central Neuquén, which was not included in the synonomy of the true Trigonia stelzneri by Lambert (1944), consti- tutes a juvenile specimen of 7. corderoi, very similar to the one figured in Plate 4, figures 5 and 9 of this monograph.
Age and occurrence.—Early Bajocian to Early Bath- onian, Emileia giebeli to Cadomites—Tulitidae Zones, Lajas Formation; Los Pozones (Locality 15), Dept. Za- pala, and Chacaico (Locality 21), Dept. Catan Lil, Ne- uquén, Argentina. Also present in Chile in similar aged rocks.
Trigonia mollesensis Lambert, 1944 Plate 2, figures 12, 19
Trigonia mollesensis Lambert, 1944, p. 364, pl. 3, figs. 1-4; pl. 10, fig. 6; Leanza and Garate, 1987, p. 207, pl. 2, figs. 3, 4.
Description.—Shell large, inequivalve, trigonally ovate. Umbones opisthogyrous, not as prominent as in 7. corderoi. Dorsal margin slightly concave. Dor- soposterior angle obtuse. Posterior margin very short. Ventroposterior angle acute. Ventral margin convex, very slightly sinuous at its posterior end; ventral mar- gin curves evenly into the convex anterior margin. Flank wide, occupying four-fifths of the shell surface, orna- mented by 25 to 32 subconcentric costae that show a
marked undulation on the anterior flank. Area not very wide, divided into two asymmetrical parts by a median carina, ornamented by 10-12 beaded, radial costae. Marginal carina well developed, with crenulations du- plicating in number the flank costae. Antecarinal sulcus present in the left valve; postcarinal sulcus found in the right valve. Escutcheon lanceolate, depressed, bounded by a well developed, clavate escutcheon ca- rina.
Material.—One hypotype, adult specimen, MOZ P0911, complete, with both valves very well preserved.
Measurements (in mm).—
Specimen No. IL, H WwW H/L W/L MOZ P0911 1? 58 23 0.80 0.32
Remarks.—Trigonia mollesensis Lambert clearly dif- fers from the associated Trigonia corderoi Lambert in that: (1) the umbones are less prominent; (2) the ventral margin shows a sinuosity near its posterior end; (3) the anterior and ventral margins merge very gradually; (4) the flank occupies a relatively major proportion of the shell surface; and (5) the costae describe a clear sinu- osity at the anterior flank.
Age and occurrence.—Early Bajocian to Early Bath- onian, Emileia giebeli to Cadomites—Tulitidae Zones, Lajas Formation; Los Pozones (Locality 15), Dept. Za- pala, Neuquén, Argentina.
Trigonia losadai, new species Plate 5, figures 3, 4
Holotype. —MOZ P3017, a complete and well pre- served specimen.
Type locality.—Los Pozones (Locality 15), Dept. Za- pala (39°10’S, 70°04’W). Lajas Formation (Weaver, 1931), Cuyo Group (Groeber, 1946).
Etymology.—In memoriam of Dr. Carlos A. Losada, former Director of the Mining Bureau of Neuquén Province, who improved the activities of the Museum Juan Olsacher.
Diagnosis.— Classic Trigoniidae of the costata group characterized by unusually wide flanks which are or- namented by sparse subconcentric costae. Marginal ca- rina poorly defined. Area asymmetrically divided by a median carina, and ornamented by radial, beaded costellae. Escutcheon apparently with weak growth lines. Both area and escutcheon with rather flattened surfaces.
Description.—Shell large, inequivalve, trigonal. Umbones prominent, opisthogyrous. Dorsal margin slightly concave, very short. Dorsoposterior angle very obtuse. Posterior margin short. Ventroposterior angle acute. Ventral margin slightly convex, markedly sin- uous at its posterior end, and curving evenly to the convex anterior margin. Flank very wide, occupying
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 21
five-sixths of the shell surface, ornamented by 18-20 subconcentric costae which are separated by intercostal spaces equal to three times the width of the costae. Area divided into two asymmetrical parts by a shallow median carina, ornamented by fine, beaded radial cos- tae. Marginal carina not well developed. Antecarinal sulcus present in the left valve, and postcarinal sulcus occurs in the right valve. Escutcheon short and narrow, excavated, apparently with growth lines, bounded by a beaded escutcheon carina.
Measurements (in mm).—
Specimen No. 1G H WwW H/L W/L MOZ P3017 70 58 23 0.82 0.32
Remarks.—Trigonia losadai, n. sp. differs from the associated Trigonia mollesensis Lambert in the follow- ing details: (1) its more trigonal shell shape; (2) its relatively shorter dorsal margin; (3) both the area and escutcheon form a more flattened surface; (4) the flanks occupy a relatively greater surface of the shell; and (5) the costae on the flank are regularly concentric and less abundant, resulting in wider intercostal spaces.
Trigonia losadai, n. sp. differs from the associated T. corderoi Lambert, in having: (1) a different shell shape; (2) the flank occupying a relatively larger pro- portion of the shell surface; (3) fewer flank costae; (4) a more indistinct marginal carina; and (5) a much more flattened area.
Trigonia costata Lamarck (in Agassiz, 1840, pl. 3, figs. 12-14) from the Liassic of Switzerland is a closely related species, but differs from 7. /osadai, n. sp. in that: (1) the flanks occupy a relatively greater surface of the shell; (2) the costae on the flank are more nu- merous; and (3) the marginal carina is much more prominent on T. costata. Trigonia similis Agassiz (1840, pl. 2, figs. 18-21, pl. 3, figs. 7, 7’) from the Liassic of Gundershofen, Haut-Rhin, Germany, also shows strong affinities, but differs from 7. /osadai, n. sp. in having: (1) a more prominent marginal carina; and (2) more regular concentric costae.
Age and occurrence.—Early Bajocian to Early Bath- onian, Emileia giebeli to Cadomites—Tulitidae Zones, Lajas Formation; Los Pozones (Locality 15), Dept. Za- pala, Neuquén, Argentina.
Trigonia densestriata Behrendsen, 1892 Plate 3, figures 7-9
Trigonia densestriata Behrendsen, 1892, pl. 1, fig. 8; Leanza and Garate 1987, p. 207, pl. 1, fig. 4.
Description.—Shell small, shape trigonal, inequi- valve. Umbones opisthogyrous. Dorsal margin flat- tened. Dorsoposterior angle very obtuse. Posterior margin short. Ventroposterior angle acute. Ventral margin well rounded, curving continuously into the
convex anterior margin. Flank ornamented by more than 25 very fine, concentric costae, with the inter- costal spaces equal to the width of the costae. Marginal carina poorly defined. Area ornamented by radial cos- tellae. Escutcheon ornamented by oblique growth lines, bounded by a shallow, poorly defined escutcheon ca- rina.
Material.—One hypotype adult specimen, MOZ P3042, complete, with both valves not very well pre- served.
Measurements (in mm).—
Specimen No. IE, H WwW H/L W/L MOZ P3042 28 18 8 0.64 0.28
Remarks.—This hypotype allows new morphologi- cal observations to be made on the previously poorly known T. densestriata Behrendsen. The shell is longer than high, and the escutcheon is ornamented by oblique growth lines. Although in lateral view the flank orna- mentation resembles that of Frenguelliella perezreyesi, n. sp. (this paper) from the same beds, the transversely costulate area of the latter species easily differentiates these taxa. Leanza and Garate (1987, p. 207, pl. 1, fig. 4) previously described this species from Los Pozones (Locality 15).
Age and occurrence.— Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, Neuquén, Argentina.
Trigonia mirandaensis Lambert, 1944 Plate 5, figure 7
Trigonia mirandaensis Lambert, 1944, p. 371, pl. 1, fig. 9.
Description. —Shell small, trigonal, somewhat longer than high, slightly inflated. Umbones opisthogyrous, situated in the anterior one-third of the shell. Dorsal margin slightly concave. Dorsoposterior angle very ob- tuse. Posterior margin short. Ventroposterior angle acute. Ventral margin slightly convex, curving strongly into the almost straight anterior margin. Flank occu- pying four-fifths of the shell surface, ornamented by nearly 18 smooth, subconcentric, relatively wide cos- tae. The intercostal spaces are equivalent to twice the width of the costae. Area subplanate, forming almost a right angle with the plane of the flanks, divided into two parts by a median carina, ornamented by 3 or 4 radial costellae on each portion. Marginal carina pro- truding, with antecarinal sulcus in the left valve and postcarinal sulcus in the right valve. Escutcheon, short and wide, apparently smooth.
Material.—One topotype adult specimen, MOZ P4252/3, a poorly preserved right valve, in a coarse- grained, light-brown sandstone.
22 BULLETIN 343
Measurements (in mm).—
Specimen No. 1c H WwW H/L W/L SGN 41-201 26 20 - 0.75 -
Remarks.—Trigonia mirandaensis Lambert shows affinities with 7. angustecostata Behrendsen (1892, p. 28, pl. 3, fig. 7) from the Hauterivian Agrio Formation of Neuquén (see Leanza and Garate, 1987, p. 208), but in this species the flank costae are narrower and more numerous, and the intercostal spaces narrower. This species occurs in association with Lambertrigonia pi- chimoncolensis (Lambert) in coarse-grained, light- brown sandstones from the Tordillo Formation.
Age and occurrence.—Kimmeridgian (unknown ammonite Zone), Tordillo Formation; northwest of Laguna Miranda (Locality 33), Dept. Zapala, Neu- quén, Argentina.
Trigonia carinata Agassiz, 1840 Plate 7, figures 7-9
Trigonia carinata Agassiz, 1840, p. 43, pl. 7, figs. 7-10; d’Orbigny, 1843, vol. 3., p. 132, pl. 286, fig. 7; Lycett, 1877, p. 179, pl. 35, figs. 3-6; Burckhardt, 1900a, p. 22, pl. 25, figs. 6-8; 1903, p. 75, pl. 13, fig. 6, pl. 14, fig. 3; Weaver, 1931, p. 263, pl. 26, figs. 137- 141, pl. 27, figs. 147-149; A. F. Leanza, 1945, p. 94, fig. 17; Corvalan and Pérez, 1958, p. 40, pl. 3, figs. la, b; Corvalan, p. 31, fig. 5; Leanza and Garate, 1987, p. 207, pl.5, figs. 6, 7.
Trigonia stelzneri Agassiz. Philippi, 1899, p. 68, pl. 31, figs. 1-3, pl. 35) figs 2:
Trigonia (Trigonia) carinata Agassiz. Reyes and Pérez, 1978, pl.1, figs. 1, 2.
Description.—Shell large. Trigonally ovate. Inequi- valve, with very wide and thick valves. Umbones op- isthogyrous, not elevated above the hinge line. Dorsal margin flat, slightly elevated in its middle part. Dor- soposterior angle very obtuse. Posterior margin short. Ventroposterior angle also obtuse. Ventral margin short and strongly convex, passing abruptly to the slightly convex anterior margin. Flank occupying more than two-thirds of the shell surface, ornamented by nearly 28 strong, subconcentric costae that meet the anterior margin at very high angles. Marginal carina prominent, ornamented by short, raised costae that duplicate the number of costae on the flank. Antecarinal sulcus pres- ent in the flank of the left valve; postcarinal sulcus occurs in the area of the right valve. Area well defined, divided almost symmetrically by a tuberculated me- dian carina, and ornamented with beaded radial costae which are intercepted by concentric growth lines; con- centric lines more dominant in the distal portion of the area. Escutcheon very wide and subplanate, with a shallow elevation in its middle part, ornamented by radial and prominent growth lines. Escutcheon carina well developed, tuberculated. A short, deep ligamental fossette is present. Both valves show a shallow anterior
byssal gape at the plane of commissure, just below the beaks.
Material.—Two hypotype adult specimens, MOZ P0915, complete, with both valves very well preserved (see Leanza and Garate, 1987, pl. 5, figs. 6-7) and MOZ P4395, from Cerrito Caracoles (Locality 11), and one hypotype adult specimen, MOZ P5607, complete, with both valves very well preserved, from Cerro Mesa, Covunco (Locality 8).
Measurements (in mm).—
Specimen No. Ib H WwW H/L W/L
MOZ P0915 92 57 38 0.61 0.41 MOZ P5607 58 40 225 0.68 0.38
Remarks.—There is a possibility that the Andean specimens of Trigonia carinata Agassiz figured since Philippi (1899) and Burckhardt (1900a,b) belong to other new taxa, but a reexamination of the specimens of T. carinata figured by d’Orbigny (1843) and Lycett (1877) is needed to determine this.
T. carinata Agassiz (1840, pl. 7, figs. 7-10) from the Neocomian of Neuchatel, Switzerland, was originally founded on the basis ofan internal mold which exhibits significant differences when compared with the south- western Gondwanan forms. The assignment of the South American specimens to 7. carinata Agassiz thus follows the interpretation of this taxon by previous workers (Burckhardt, 1903; Weaver, 1931; Corvalan and Pérez, 1958; Corvalan, 1959; Reyes and Pérez, 1978; Leanza and Garate, 1987).
Age and occurrence.— Upper Tithonian, Substeuer- oceras koeneni Zone, Pican Leufa Formation; Cerrito Caracoles (Locality 11), Dept. Zapala. Lower/Middle Hauterivian, Lyticoceras pseudoregale and Holcop- tychites neuquensis Zones, Agrio Formation; Cerro Mesa, Covunco (Locality 8), Dept. Zapala, Neuquén, Argentina.
Trigonia levyi, new species Plate 6, figures 3, 4
Holotype.—MOZ P5314, a well preserved adult right valve with the posterior part broken, fossilized as a quartz geode with calcite in the center.
Type locality.—Las Cortaderas (Locality 36), Dept. Catan Lil (39°23'S, 70°11'W), Picun Leufa Formation (Leanza, 1973), Mendoza Group (Groeber, 1946).
Etymology.—This species is dedicated to the Argen- tine paleontologist Regina Levy of Buenos Aires, Ar- gentina, former specialist in trigoniid bivalves.
Diagnosis.—Shell large, with flank ornamentation similar to Trigonia carinata Agassiz, but area and es- cutcheon distinctly ornamented by protruding trans- verse rugae crossed by deep radial grooves.
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 23
Description.—Shell large, trigonally ovate. Umbones opisthogyrous, situated in the extreme anterior part of the shell. Escutcheon, area and flank distinctly sepa- rated. Dorsal margin slightly convex in its middle part. Dorsoposterior angle obtuse. Posterior margin and ventroposterior angle not preserved. Ventral margin not preserved, but presumably short and convex. An- terior margin widely convex. Flank occupying only one-half of the shell surface, ornamented by more that 20 sharp, elevated, subconcentric costae that meet the anterior margin at high angles, similar to the style of costulation of Trigonia carinata Agassiz. Marginal ca- rina prominent, ornamented by short, transverse ru- gae. Area well defined, ornamented by protruding transverse rugae, symmetrically divided by a deep me- dian groove, and the remaining lower and upper por- tions of the area by further deep radial grooves, giving the area a corn-like aspect. Escutcheon relatively wide and long, separated form the area by a deep groove, ornamented by oblique rugae which are smaller than those of the area, but equally crossed by deep radial grooves.
Measurements (in mm).—
Specimen No. L H W H/L W/L MOZ P5314 =85 - 28 - 0.32
Remarks.—Trigonia levyi, n. sp. differs from any other known species of the genus 7rigonia Bruguiére by the characteristic ornamentation of area and es- cutcheon, consisting in protruding transverse rugae crossed by deep radial grooves producing a corn-like aspect. Trigonia levyi, n. sp. has a flank ornamentation similar to the South American Tithonian and Neo- comian representatives of Trigonia carinata Agassiz (1840, p. 43, pl. 7, figs. 7-1; Weaver, 1931, p. 263, pl. 26, figs. 137-141; pl. 27 figs. 147-149; herein de- scribed), or the Hauterivian Trigonia aliexpandita Leanza and Garate (1983, p. 106, pl. 1, figs. 1-3; herein described), but the different pattern of the ornamen- tation of area and escutcheon easily allows differenti- ation of these taxa.
Age and occurrence.— Middle Tithonian, Windhau- seniceras internispinosum Zone, Picun Leufa Forma- tion; Las Cortaderas (Locality 36), Dept. Catan Lil, Neuquén, Argentina.
Trigonia, species juvenile indeterminate Plate 8, figure 5
Description.—Shell very small (L = 8.5 mm), tri- gonally ovate. Umbones opisthogyrous, situated in the anterior one-third of the shell. Dorsal margin straight. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle almost 90°. Ventral mar- gin straight, curving strongly into the widely convex
anterior margin. Flank occupying four-fifths of the shell surface, ornamented by twelve, equally spaced, weakly beaded, subconcentric costae. Surfaces of flank and area meet at a high angle where a poorly defined mar- ginal carina is present. Area ornamented by faint radial costellae. Escutcheon not observable. Material.—One juvenile specimen, MOZ P5466, consisting of a rather well preserved right valve, fos- silized in a yellowish-white calcarenite. Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P5466 8.5 525 2 0.64 0.23
Remarks.—A\though this very small right valve is relatively well preserved, the juvenile nature of the specimen precludes further taxonomic determination.
Age and occurrence.—Upper Tithonian, Substeuer- oceras koeneni Zone, Pican Leufu Formation; Laguna Blanca (Locality 13), Dept. Zapala, Neuquén, Argen- tina.
Trigonia fortinensis Lambert, 1944 Plate 6, figures 6, 7
Trigonia fortinensis Lambert, 1944, p. 386, pl. 4, figs. 5-8.
Description.—Shell small, elongated. Umbones prominent, opisthogyrous. Dorsal margin short, nearly straight. Dorsoposterior angle very obtuse. Posterior margin relatively long. Ventroposterior angle acute. Ventral margin slightly convex, passing evenly to the convex anterior margin. Flank ornamented by nearly 30 very narrow, subconcentric costae. Marginal carina poorly defined, except that the surfaces of flank and area meet at a high angle. Area relatively narrow, or- namented by numerous radial costellae. Escutcheon narrow, ornamented by radial growth lines, bounded by a poorly defined escutcheon carina.
Material.—One hypotype adult specimen, MOZ P3006, complete, with both valves relatively well pre- served.
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P3006 30 19 5:5 0.63 0.18
Remarks.—Trigonia fortinensis Lambert closely re- sembles the Bajocian 7. densestriata Behrendsen from the Lajas Formation of the Neuquén Basin (herein described), but it differs in having more elevated um- bones, a rostrate shell, and denser costae on the flank. The Hauterivian 7. angustecostata Behrendsen (1892) from the Agrio Formation (herein described) is also a closely related species, but differs from 7. fortinensis in being much wider and shorter, in not exhibiting the
24 BULLETIN 343
elongate pattern of the shell, and in having the area and escutcheon approximate a flattened surface.
Age and occurrence.—Upper Tithonian, Corongo- ceras alternans Zone, Picun Leufa Formation; Cerro Lotena (Locality 32), Dept. Zapala, Neuquén, Argen- tina.
Trigonia aliexpandita Leanza and Garate, 1983b Plate 10, figures 3, 4
Trigonia carinata Lambert, 1944 (non Agassiz), p. 383, pl. 8, fig. 5.
Trigonia carinata aliexpandita Leanza and Garate, 1983b, p. 106, pl. 1, figs. 1-3; Leanza and Garate, 1987, pl. 5, figs. 1-3; pl. 6, fig. 1.
Description.—Shell large, inequivalve, trigonally ovate. Umbones opisthogyrous, very anteriorly situ- ated. Dorsal margin notably expanded in correspon- dence with the large escutcheon. Dorsoposterior angle obtuse. Posterior margin relatively short. Ventropos- terior angle almost 90°. Ventral margin short and strongly convex, passing abruptly to the gently convex anterior margin. Flank occupying more than two-thirds of the shell surface, ornamented by strong, subconcen- tric costae. Marginal carina prominent, ornamented by transversely elongated short costae, duplicating dis- tally the number of flank’s costae. Antecarinal sulcus present in the left valve: postcarinal sulcus present on the right valve. Area well-defined, strongly ornament- ed by beaded radial costae which are intercepted by concentric growth lines, producing a reticulate orna- ment. Escutcheon well defined, diagnostic of the spe- cies, notably expanded in the form of a wing in its mid- posterior region. Escutcheon carina clavate, prominent.
Material.—The holotype specimen, MOZ P0951/1 (see Leanza and Garate, 1983b, pl. 1, figs. 1-3), an adult specimen, complete, with both valves very well preserved.
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P0951/1 78 63 0.80 0.29
he w
Remarks.— Although this species was originally de- scribed by Leanza and Garate (1983b) as a variety of T. carinata, it is now considered that the strongly pro- truding escutcheon is a unique feature in the shell mor- phology of specific significance. This feature may also have importance in the mode of life of this trigoniid bivalve; the escutcheon seems likely to have had re-
piratory functions, and may have been elevated above the water-sediment interface, resembling the living po- sition of Trigonia as drawn by Stanley (1977, p. 881, text-fig. 5). For this reason the subspecies aliexpandita is here elevated to species rank.
Age and occurrence.—Lower and Middle Hauteri- vian, Lyticoceras pseudoregale and Holcoptychites neu-
quensis Zones, Agrio Formation; Cerro Mesa, Covun- co (Locality 8), Dept. Zapala, Neuquén, Argentina.
Trigonia wiedmanni Leanza and Garate, 1987 Plate 17, figures 7-10
Trigonia wiedmanni Leanza and Garate, 1987, p. 209, pl. 6, figs. 3-5.
Description.—Shell small, inequivalve. Trigonally ovate. Umbones opisthogyrous, very anteriorly situ- ated. Dorsal margin short and nearly flat. Dorsopos- terior angle obtuse. Posterior margin long. Ventropos- terior angle almost 90°. Ventral margin slightly convex, curving continuously to the convex anterior margin. Flank ornamented by eight to nine smooth, raised, subconcentric costae, separated by intercostal spaces equivalent to three times their width. Marginal carina strongly developed. Antecarinal sulcus present in the left valve; postcarinal sulcus occurs in the right valve. Area occupying one-third of the shell surface, divided in two equal parts by a median carina, and ornamented by a narrow, widely spaced costellae, protruding above the otherwise smooth surface. Escutcheon smooth, somewhat excavated, bounded by a well-defined, raised, escutcheon carina. Byssal gape occurs just below the beaks.
Material.—Holotype, a well preserved adult shell MOZ P0942/1 (see Leanza and Garate, 1987, pl. 6, figs. 3-5). Paratype, an adult specimen, MOZ P0942/ 2, with both valves well preserved.
Measurements (in mm).—
Specimen No. Ib H WwW H/L W/L MOZ P0942/1 29 24 9 0.83 0.31 MOZ P0942/2 28 22 8.5 0.78 0.30
Remarks.—Trigonia wiedmanni Leanza and Garate (1987) resembles in its general shape some juvenile forms of 7. cassiope d’Orbigny, as figured by Lycett (1863, 1872). But these forms differ in having a greater number of costae on the flanks. Affinities of T. wied- manni can also be traced to the original Neocomian T. carinata Agassiz (1840, pl. 7, figs. 7-10), but this species has a proportionally greater shell length, a dif- ferent general shape, and has a distinct dorsal margin and anteroventral margin.
Age and occurrence.—Lower and Middle Hauteri- vian, Lyticoceras pseudoregale and Holcoptychites neu- quensis Zones, Agrio Formation; Cerro Negro, Co- vunco (Locality 9), Dept. Zapala, Neuquén, Argentina.
Trigonia angustecostata Behrendsen, 1892 Plate 13, figures 3-5
Trigonia angustecostata Behrendsen, 1892, p. 28, pl. 3, fig. 7 (= 1922, pl. 4, fig. 7); Steinmann, 1929, p. 220, fig. 29; Leanza and Garate, p. 208, pl. 5, figs. 4, 5.
TRIGONID BIVALVES OF ARGENTINA: LEANZA 25
Description.—Shell small, inequivalve, trigonally ovate. Umbones depressed. Escutcheon and area col- lectively form a flattened surface. Dorsal and posterior margins forming both a straight line. Ventral margin slightly convex, curving gradually into the convex an- terior margin. Flank ornamented by fine subconcentric costae parallel to the ventral region of shell, and meet- ing the anterior margin at high angles. Marginal carina forming a sharp edge between flank and dorsal face of shell. Area wide, with radial costellae asymmetrically divided by a very shallow submedian carina. Escutch- eon lanceolate, ornamented by faint radial costellae.
Material.— One hypotype, an adult specimen, MOZ P0950, complete, with both valves relatively well pre- served. (See Leanza and Garate, 1987, pl. 5, fig. 5).
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P0950 26 18 9 0.69 0.35
Remarks.—Trigonia angustecostata Behrendsen shows some affinities with T. fortinensis Lambert (1944, pl. 4, figs. 5, 8) from the Tithonian of Arroyo del Fortin (middle course of Catan Lil river), but the latter species is essentially rostrate, the umbones are more promi- nent, the flank is more densely costate, and the area and escutcheon do not conform to a flattened surface.
Age and occurrence.—Lower and Middle Hauteri- vian, Lyticoceras pseudoregale and Holcoptychites neu- quensis Zones, Agrio Formation; Cerro Mesa, Covun- co (Locality 8), Dept. Zapala, Neuquén, Argentina.
Subfamily NEUQUENITRIGONIINAE, new subfamily
Diagnosis.—Same as for genus.
Distribution.— Middle Jurassic (Bajocian), Argenti- na and Chile.
Discussion.—As restricted here, the new subfamily comprises only the nominate genus, Neuquenitrigonia, which bears transverse costellae on the escutcheon, and thick, widely spaced, transverse flank costae. Although Neuquenitrigoniinae clearly belongs to the family Tri- goniidae s.s., as it displays a broad area with truncated posterior margin, prominent marginal carina, and an antecarinal groove restricted to the left valve, the pres- ence in Neuquenitrigonia of a wide, flat, transversely costate escutcheon, as well as thick transverse flank costae precludes assignment of this taxon to the Tri- goniinae Lamarck (1819), as this subfamily is char- acterized by an escutcheon with radial ornament, and subconcentric flank costae (see Cooper, 1991, p.7). Ac- cordingly, Neuquenitrigonia is regarded as an indepen- dent lineage, justifying a new subfamily.
Genus NEUQUENITRIGONIA Leanza and Garate, 1987
Type species.— Trigonia huenickeni Leanza and Gar- ate, 1985, Bajocian, Neuquén, Argentina.
Diagnosis.—Shell large, inequivalve, trigonally ovate. Flank ornamented by thick, widely spaced, transverse costae. Area relatively wide, ornamented by beaded radial costae crossed by transverse growth lines, di- vided into two asymmetrical parts by a submedian carina. Marginal carina very well developed. Escutch- eon large, elevated, subplanate, and ornamented by transverse costae (Leanza and Garate, 1985, 1987).
Distribution.— Middle Jurassic (Bajocian). Argenti- na.
Neuquenitrigonia huenickeni (Leanza and Garate, 1985) Plate 3, figures 10, 17 Trigonia huenickeni Leanza and Garate, 1985, p. 290, pl. 1, figs. 1-3. Neuquenitrigonia huenickeni (Leanza and Garate). Leanza and Gar- ate, 1987, p. 209, pl. 3, figs. 1-3.
Description.—Shell large, inequivalve, trigonally ovate, longer than high, and very wide. Umbones op- isthogyrous, very anteriorly situated. Dorsal margin short and straight, coincident with the escutcheon. Dorsoposterior angle obtuse. Posterior margin rela- tively long. Ventroposterior junction rounded. Ventral margin short and slightly convex, abruptly curving into the gently convex anterior margin. Flank occupying one-half of the shell surface, ornamented by thick, widely spaced, transverse costae that meet the anterior margin at nearly 90°. Marginal carina prominent, rounded, ornamented by short, transverse costae that duplicate in number those costae arising from the flanks. Area relatively wide, divided into two asymmetrical parts by a submedian carina; ornamented by beaded radial costae, terminated by transverse growth lines, giving this region a reticulated aspect. Escutcheon large, elevated, subplanate, ornamented by thick transverse costae. Ligamental fossette wide, short, extending pos- teriorly from the beaks.
Material.—One topotype specimen (Barda Negra Sur), MOZ P2319, consisting of a well preserved adult right valve, with the umbonal region of the left valve. Two hypotype specimens (Maquina Cura, Chacaico), MOZ P4919/1, a beak of an adult left valve with the internal structure preserved; and MOZ P4919/2, a fragment of the umbonal region of a left valve.
Measurements (in mm).—
Specimen No. iE, H Ww H/L W/L
MOZ P2319 86 59 35 0.68 0.40
26 BULLETIN 343
Remarks.—The clear demarcation between the flank, area and escutcheon, and the general shape of the shell favors the inclusion of the genus Neuquenitrigonia into the subfamily Trigoniinae. Neuquenitrigonia huenick- eni is easily distinguished by the thick, widely spaced, transverse costae on the flanks, and by its wide, flat, transversely costated, escutcheon. Neuquenitrigonia has recently been found in the Middle Jurassic of Chile (E. Pérez, written communication, 1991).
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, and Maquina Cura, Chacaico (Locality 21), Dept. Catan Lil, Neuquén, Argentina.
Subfamily FRENGUELLIELLINAE Nakano, 1960 emend.
Genus FRENGUELLIELLA A. F. Leanza, 1942
Type species.— Trigonia inexspectata Jaworski, 1916 (=1925), Liassic, Piedra Pintada, Neuquén, Argentina.
Diagnosis.—Trigonally ovate. Umbones less prom- inent than in 7rigonia. Area with transverse costae or growth lines. Marginal carina ornamented by costae arising from the flank or area, or both. Flank with concentric costae that meet the anterior margin at high angles, and that may be somewhat irregular (A.F. Lean- za, 1942: Cox, 1969: Poulton, 1979).
Distribution.— Upper Triassic to Upper Cretaceous. Cosmopolitan.
Frenguelliella tapiai (Lambert, 1944) Plate 1, figure 8
Trigonia tapiai Lambert, 1944, p. 358, pl. 13, fig. 1
Trigonia (Frenguelliella) tapiai Lambert. Perez and Reyes, 1977, p. 12 ple fig. Ie
Frenguelliella tapiai (Lambert). Leanza and Garate, 1987, p. 210, pl. 1, fig. 5.
Description.—Shell of small to medium size. Ovate to subquadrangular in shape. Umbones prominent, very anteriorly situated. The flank, which occupies less than two-thirds of the shell surface, is ornamented by more than 30 very thin, equally spaced, concentric costae. Marginal carina well developed and antecarinal sulcus present, both ornamented by the costae arising from the flanks. Area triangular, widening strongly poste- riorly, asymmetrically divided by a submedian groove, and ornamented by numerous very thin, transverse costellae.
Material.—Hypotype, an adult specimen, MOZ P2679, consisting in an incomplete left valve that pre- cludes measurements.
Remarks.—The described specimen undoubtedly belongs to Frenguelliella tapiai (Lambert, 1944, pl. 13, fig. 1) from the southeast of Cerro Chachil, Neuquén, especially because it possesses a similar shell shape and
the same number of concentric costae on the flanks. H. Leanza and Garate (1987, p. 210, pl. 1, fig. 5) described the escutcheon of this species as narrow and elongated from a specimen preserved in butterfly position, or- namented by 8-10 very fine oblique costellae which are finally parallel to the dorsal margin. C. Newton (written communication, 1991) has pointed out that this taxon is also present in North America and Pert.
Age and occurrence.—Pliensbachian. Fanninoceras Zone, Chachil Formation; Estancia Marichelar, Ar- royo Nireco (Locality 14), Dept. Catan Lil, Neuquén, Argentina.
Frenguelliella inexspectata Jaworski, 1916 Plate 2, figure 9
Trigonia inexspectata Jaworski, 1916, p. 377, pl. 5, figs. 2a, b(=1925, p. 79, pl. 1, figs. 2a, b).
Trigonia (Frenguelliella) inexspectata (Jaworski). A. F. Leanza, 1942, p. 265, pl. 7, fig. 1.
Description.—Internal mold of a large shell. Inequi- valve. Umbones opisthogyrous, not very prominent. Flank occupying two-thirds of the shell surface, or- namented by nearly 30 simple, regularly spaced sub- concentric costae. Marginal carina poorly defined. Area ornamented by transverse, equally spaced, narrow cos- tae which duplicate in number those costae present on the flank. Escutcheon not recognizable.
The internal mold preserves evidence of a broad, bifid tooth 2 (Douvillé notation, 1913) in the left valve, and a transversely ridged 3a tooth in the right valve.
Material.—Hypotype, MOZ P2766, consisting in an internal mold, poorly preserved juvenile specimen, showing part of the left and right valves.
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P2766 =55 40 15 0.72 0.27
Remarks.— Although the described specimen is an internal mold, its morphological features allow assign- ment to Frenguelliella inexspectata (Jaworsk1).
Age and occurrence.—Pliensbachian, Otapiria neu- quensis and Radulonectites sosneadensis Zones; Estan- cia Santa Isabel (Locality 39), Dept. Catan Lil, Neu- quén, Argentina.
Frenguelliella poultoni, new species Plate 2, figures 3-6
Frenguelliella sp. B. Poulton, 1979, p. 18, pl. 1, fig. 10.
Holotype.—MOZ P5315, a complete, well preserved right valve.
Paratypes.—MOZ P5316, a well preserved adult right valve; MOZ P5317/1, a relatively well preserved ju- venile right valve; MOZ P5317/2, an external cast of an adult right valve.
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 27
Type locality.— Arroyo Nireco. Estancia Marichelar (Locality 14), Dept. Catan Lil (39°02’S, 70°32'W), Chachil Formation (Weaver, 1942), Cuyo Group (Groeber, 1946).
Etymology.—The species is dedicated to the Cana- dian paleontologist Terry P. Poulton (Calgary, Cana- da).
Diagnosis.— Finely sculptured and more nearly rect- angular in outline than any other known species of Frenguelliella. Area broad, with fine regular transverse costellae. Marginal carina distinct. Flank with no more than 18 very regular, equally spaced, concentric costae.
Measurements (in mm).—
Specimen No. IL H WwW H/L W/L MOZ P5315 18 15 - 0.83 - MOZ P5317/1 18 15 3.5 0.83 0.19 MOZ P5316 33 25 - 0.75 - MOZ P5317/2 23 17 4 0.74 0.17
Description.—Shell small, rectangular in shape, much longer than high. Umbones very anteriorly situated. Dorsal margin slightly concave. Dorsoposterior angle slightly obtuse. Posterior margin long. Ventroposterior angle almost 90°. Ventral and anterior margins forming a broad, continuous convex margin up to the beaks. Area wide, asymmetrically divided by a median groove, strongly flaring toward the posterior margin, orna- mented by transverse costellae in the proximal portion, and by growth lines in the distal part. Marginal carina distinct. Escutcheon carina poorly defined except near umbo. Flank ornamented by no more than 18 very regular, equally spaced, concentric costae that meet the anterior margin at high angles. Escutcheon probably with very faint oblique growth lines.
Remarks.—This species appears to be identical with Frenguelliella sp. B of Poulton (1979, p. 18, pl. 1, fig. 10) from the Early Sinemurian of Laberge Group, Yu- kon Territory, Canada, in the rectangular shape of the shell, and the great similarity of ornamentation on the area and flank, including a distinct marginal carina. It differs from the English “*Trigonia” costatula Lycett (1872-1879, pl. 12, figs. 6, 6a) in being more elongated and in having a more flared area. Frenguelliella tapiai (Lambert, 1944, pl. 13, fig. 1), which occurs in the same formation in the southwestern part of the Neuquén Basin, differs from Frenguelliella poultoni, n. sp. in having a subquadrangular shape, an area with marked transverse costae occupying a relatively larger portion of the shell surface, as well as by a greater number of costae on the flanks.
Age and occurrence.—Sinemurian, Laberge Group, Yukon, Canada. Pliensbachian, Fanninoceras Zone, Chachil Formation; Estancia Marichelar, Arroyo Ni- reco (Locality 14), Dept. Catan Lil, Neuquén, Argen- tina.
Frenguelliella perezreyesi, new species Plate 2, figures 1-2, 7-8
Holotype.—MOZ P3030/1, consisting in a well-pre- served, adult right valve.
Paratype.—MOZ P3030/2, consisting in a small adult, right valve.
Type locality.—Barda Negra Sur (Locality 16), Dept. Zapala (39°10'S, 69°57'W). Neuquén. Argentina, Lajas Formation (Weaver, 1931), Cuyo Group (Groeber, 1946).
Etymology.—This species is dedicated to the Chil- ean paleontologists and trigoniid specialists Ernesto Pérez d’Angelo and Renato Reyes.
Diagnosis.—Shell of small size, trigonal. Umbones opisthogyrous. Flank densely ornamented by narrow subconcentric costae. Marginal carina forming a strong junction between the flank and dorsal face of the shell. Area wide, with narrow transverse costellae that du- plicate in number those of the flank. Escutcheon very narrow, apparently smooth.
Measurements (in mm).—
Specimen No. 1, H WwW H/L W/L
MOZ P3030/1 19 14 6 0.73 0.31
MOZ P3030/2 15 10 4 0.66 0.26
Description.—Shell moderately small, inequivalve. Umbones opisthogyrous, relatively prominent. Es- cutcheon and area forming a flattened surface. Dorsal and posterior margins extending through a same line up to the ventroposterior junction. Ventral and ante- rior margins forming a wide convexly curved margin. Flank ornamented by more than 30, very narrow, equally spaced, subconcentric costae. Marginal carina distinct, but not well developed, coinciding with a strong junction between the flank and dorsal face of the shell. Area relatively wide, ornamented by transverse cos- tellae that duplicate in number those arising from the flank. Escutcheon very narrow, apparently smooth.
Remarks.—This new species of Frenguelliella is eas- ily distinguished from other known species by its mod- erately small size and the shell shape, in which the dorsal face of the valve forms a flattened surface that meets the flank surface almost perpendicularly. This feature also distinguishes this new species from the densely costate Pliensbachian Frenguelliella tapiai (herein described), in which the area is also compar- atively wider. Frenguelliella poultoni, n. sp. exhibits a much more sparsely costate flank, and the shell shape is also different. Resemblance of the new species with Trigonia densestriata Behrendsen and Trigonia an- gustecostata Behrendsen (both herein described) are only superficial, as these species display radial orna- ment in the area and escutcheon, a feature which is absent in Frenguelliella.
28 BULLETIN 343
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, Neuquén, Argentina.
Subfamily MYOPHORELLINAE Kobayashi, 1954 Genus JAWORSKIELLA A. F. Leanza, 1942
Type species.— Trigonia burckhardti Jaworski, 1916 (=1925), Liassic (Pliensbachian), Piedra Pintada, Ne- uquén, Argentina.
Diagnosis.— Oblong, strongly inequivalve. Area with strong, transverse ridges. Marginal carina well devel- oped. Costae on the anterior flank gently oblique, an- teroventrally sloping; costae on the posterior flank up- wardly curved. These can be either continuous or with lines of pustules. Antecarinal groove present, across which faint extensions of the costae may extend. Each costa of the area may correspond with a flank costa, or there may be a larger number of spaced costae (A.F. Leanza, 1942; Cox, 1969; Poulton, 1979).
Distribution.—Lower Jurassic. North and South America.
Jaworskiella burckhardti (Jaworski, 1916) Plate 1, figures 1, 6-7, 10
Trigonia gryphitica Burckhardt non Steinmann. Burckhardt, 1901, p. 21, pl. 4, fig. 4.
Trigonia burckhardti Jaworski, 1916, p. 380, pl. 5, fig. 3 (= 1925, p. 81, pl. 1, fig. 3).
Trigonia (Jaworskiella) burckhardti (Jaworski). A. F. Leanza, 1942, p. 166, pl. 6, figs. 2, 3.
Jaworskiella burckhardti (Jaworski). Perez and Reyes, 1977, p. 14, pl. 2, figs. 1, 3, 6; Leanza and Garate, p. 210, pl. 1, figs. 1, 2.
Description.—Shell of medium to very large size. Oblong, inequivalve, somewhat inflated, with thick valves. Umbones prominent, opisthogyrous, slightly raised above the hinge line. Dorsal margin concave. Dorsoposterior angle obtuse. Ventroposterior angle al- most right to slightly obtuse. Posterior margin short. Ventral margin well rounded, curving into the convex anterior margin. Flank occupying more than four-fifths of the shell surface, ornamented in the adult stage by more than 22 subconcentric, more or less sinuous cos- tae. On the anterior flank these are bifurcated in some cases, and on the posterior flank they are pustulate and upwardly curved. In the juvenile specimen, the costae follow the same pattern, but they do not show com- plications on the anterior flank, and they are fewer in number. Area well-defined, bounded by tuberculated marginal and escutcheon carina, ornamented in the adult by strong oblique ridges and growth lines, and asymmetrically divided by a submedian groove. The juvenile shells have narrow, transverse costellae. Es- cutcheon elongated, slightly concave, apparently smooth.
Material.—Hypotype, MOZ P3044, complete adult shell, very well preserved, with the right valve some- what broken posteriorly; hypotype, MOZ P3043, com- plete juvenile shell, very well preserved.
Measurements (in mm).—
Specimen No. 1t, H WwW H/L W/L
MOZ P3044 105 78 28 0.74 0.26 MOZ P3043 41 33 13 0.80 0.31
Remarks.—A\though the type species of Jaworskiel- /a bears simple costae (see Jaworski, 1916, pl. 5, fig. 3), the presence of pustulose costae in the posterior flank of J. burckhardti is interpreted to represent intra- specific variation. The presence of somewhat tuber- culated costae in this part of the flank was already referred to in this species by Leanza and Garate (1987, p. 210); the other essential features of the species re- main constant, in agreement with the interpretation of this genus made by Poulton (1979, p. 19). The small specimen is interpreted to be a juvenile representative of J. burckhardti. It displays similar morphometric parameters, with the only exception being that the flank costae are simple, as in the type species of Jaworskiella.
Quadratojaworskieila pustulata Reyes and Pérez (1980, p. 89, pl. 1, figs. 1-4; pl. 2, figs. 1-4) from the Early Pliensbachian of Quebrada Los Asientos, north- ern Chile, differs from J. burckhardti by its quadrate shape, nearly straight anterior margin, greater number of costae, and presence of true tubercles on the flank ornamentation.
Age and occurrence.—Pliensbachian, Otapiria neu- quensis and Radulonectites sosneadensis Zones, Piedra Pintada Formation; Cerrito Roth, Canadon de la Pied- ra Pintada (Locality 24), Dept. Collon Cura, and Es- tancia Santa Isabel (Locality 27), Dept. Collon Cura, Neuqueén, Argentina.
Genus MYOPHORELLA Bayle, 1878
Type species. —Myophorella nodulosa Bayle, 1878, Upper Jurassic (Oxfordian), France.
Diagnosis.—Trigonally ovate, strongly inequivalve. Area bipartite, with transverse costae or growth lines, and in some species with oblique costae superimposed on the transverse ornament. Marginal and escutcheon carinae generally distinct. Flank variously ornament- ed, usually with oblique and curved costae which may bear rows of different type and size of tubercles. Es- cutcheon very distinct, shallow, with transverse to oblique costellae or growth lines (Crickmay, 1932; Cox, 1969; Poulton, 1979).
Distribution.—Lower Jurassic (Middle Liassic) to Upper Cretaceous. Cosmopolitan.
TRIGONID BIVALVES OF ARGENTINA: LEANZA 29
Subgenus MYOPHORELLA sensu stricto
Myophorella (Myophorella) araucana (A. F. Leanza, 1942) Plate 1, figures 4, 5
Trigonia aff. angulata Sowerby. Burckhardt, 1901, p. 22, pl. 4, figs. 5; 6.
Trigonia (Clavitrigonia) araucana A. F. Leanza, 1942, p. 162, pl. 6, figs. 4-6.
Myophorella(Promyophorella) araucana (A. F. Leanza). Levy, 1966, p. 240.
Myophorella (Myophorella) araucana (A. F. Leanza). Pérez and Reyes, 1977, p. 13, figs. 1-3. (= T. (C.) araucana A. F. Leanza, 1942, pl. 6, figs. 4-6); Pérez, 1982, pl. 14, fig. 9; Leanza and Garate, 1987, p. 211, pl. 1, figs. 6-8.
Description.—Shell medium to large in size. Ovate, somewhat longer than high, inequivalve. Umbones op- isthogyrous, very anteriorly situated, slightly raised above the hinge line. Dorsal margin concave. Dorso- posterior angle obtuse. Posterior margin relatively long. Ventroposterior angle obtuse. Ventral margin round- ed, curving continuously into the convex anterior mar- gin. Area wide, ornamented by fine transverse costae, bounded by a tuberculated marginal carina, more marked in its distal portion, and a clavate escutcheon carina. Flank ornamented with concentric tuberculated costae, with intercostal spaces widening toward the ventral margin. Antecarinal sulcus present. Escutcheon smooth, highly excavated.
Material.—One adult topotype specimen, MOZ P0875, a complete shell, with both valves well pre- served.
Measurements (in mm).—
Specimen No. I H WwW H/L W/L MOZ P0875 65 48 20 0.73 0.30
Remarks.—Levy (1966, p. 240) suggested that this species should be included in the subgenus Promy- ophorella Kobayashi and Tamura (1955), but the pres- ence of sharp tubercles precludes such assignment. Al- though this species was recorded in the Pliensbachian of Piedra Pintada, it may range in Argentina well into the Early Toarcian Dactylioceras simplex and D. ten- uicostatum chilense Zones.
Age and occurrence.—Pliensbachian, Ofapiria neu- quensis and Radulonectites sosneadensis Zones, Piedra Pintada Formation; La Amarga, near Rincon del Agui- la (Locality 37), Dept. Zapala, Neuquén, Argentina.
Myophorella (Myophorella) catenifera (Hupé, 1854) Plate 2, figures 10, 11
Trigonia catenifera Hupé in Gay, 1854, p. 388, pl. 5, fig. 8; Philippi, 1899, p. 85, pl. 36, fig. 5.
Myophorella (Myophorella) catenifera (Hupé). Pérez and Reyes, 1977, p. 12, pl. 3, fig. 6.
Description.—Shell small. Umbones opisthogyrous, very anteriorly situated. Dorsal margin strongly con- cave. Dorsoposterior junction situated slightly above the plane of the beaks, almost forming a right angle. Posterior margin relatively long. Ventroposterior angle obtuse. Ventral and anterior margins forming a con- tinuous, convex curve. Area ornamented with narrow transverse costellae, bounded by a prominent marginal carina and a poorly defined escutcheon carina. Flank ornamented with subconcentric costae that bear small and equally prominent tubercles. Escutcheon not pre- served.
Material.—Two adult hypotype specimens, MOZ P2682 (Estancia Souraya, Espinazo del Zorro), con- sisting in a well preserved left valve, and MOZ P4525 (Cerrito Roth, Canadon de la Piedra Pintada) consist- ing of a mold of a right valve.
Measurements (in mm).—
Specimen No. L H W H/L W/L MOZ P2682 28 23 4.6 0.82 0.16
Remarks.—The general shell shape and ornamen- tation of the specimens closely resembles Myophorella (Myophorella) catenifera (Hupé, in Gay, 1854, pl. 5, fig. 8) from the Pliensbachian of Chile (see Pérez and Reyes, 1977, p. 12), especially in having the dorso- posterior junction in a plane situated slightly above a horizontal line passing through the beaks. Myophorella (Myophorella) catenifera (Hupé) is here cited for the first time in the Argentine Liassic.
Age and occurrence.—Pliensbachian, Fanninoceras Zone, Chachil Formation; Estancia Souraya, Espinazo del Zorro (Locality 38), Dept. Catan Lil; Otapiria neu- quensis and Radulonectites sosneadensis Zones, Piedra Pintada Formation; Cerrito Roth, Canadon de la Pied- ra Pintada (Locality 24), Dept. Collon Cura, Neuqueén, Argentina.
Myophorella (Myophorella) cf. M. tuberculata (Agassiz, 1840) Plate 1, figure 9
Description.—Shell small. Umbones opisthogyrous. Dorsal margin flat. Anterior and ventral margins form- ing a continuous convex curve. Posterior part of the shell not preserved. Area well defined, bounded cen- trally by a distinct, beaded, marginal carina, and or- namented by narrow, sharp, transverse costae. Flank ornamented with widely spaced, prominent, concen- tric costae which bear very small, equal-sized tubercles.
Material.—One adult hypotype specimen, MOZ P2675, consisting of an incomplete external mold of a poorly preserved left valve which precludes mea- surements.
30 BULLETIN 343
Remarks.—The described specimen closely resem- bles Myophorella tuberculata (Agassiz, 1840, p. 20, pl. 2, fig. 17; pl. 9, figs. 7-8) from the Liassic of Gunder- shofen, Germany, but the poor preservation of the Argentine specimen precludes comparison of the shell shape and other morphological features.
Age and occurrence.—Pliensbachian, Otapiria neu- quensis and Radulonectites sosneadensis Zones, Piedra Pintada Formation; Estancia Santa Isabel (Locality 39), Dept. Collon Cura, Neuquén, Argentina.
Myophorella (Myophorella) argentinica (Jaworski, 1926) Plate 2, figures 14, 17
Trigonia argentinica Jaworski, 1926, p. 180, pl. 1, fig. 6. Myophorella argentinica Jaworski. Leanza and Garate, 1987, p. 211, pl. 3, fig. 10.
Description.—Shell of medium size, elongated. Um- bones opisthogyrous, prominent, situated in the an- terior one-quarter of the shell. Dorsal margin slightly concave. Posterior margin not preserved. Ventral mar- gin slightly convex, curving evenly into the convex anterior margin. Flank occupying two-thirds of the shell’s surface, ornamented by distant, subconcentric costae which bear small, rounded tubercles which closely touch each other. The intercostal spaces be- come wider toward the anteroventral region of the shell. Marginal carina sharp, equally beaded over its whole length. Area contains faint transverse costellae. Es- cutcheon not recognizable.
Material.—Two adult hypotype specimens, MOZ P1879 (Barda Negra Sur), consisting in a right valve without its posterior part, and MOZ P4914 (Maquina Cura, Chacaico), consisting of a right valve.
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P4914 43 24 9 0.55 0.20
Remarks.—The characteristic tubercles on the flank costae support assignment of this specimen to My- ophorella (M.) argentinica Jaworski (1926, pl. 1, fig. 6). It can be differentiated from Myophorella (Pro- myophorella) praescabroidea Jaworski (1926, p. 86, pl. 1, figs. Sa—b; herein described) by: (1) its different shape; (2) its sharper tubercles which merge into each other; and (3) its less dense flank costae.
4ge and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, and Maquina Cura, Chacaico (Locality 21), Dept. Catan Lil, Neuquén, Argentina.
Myophorella (Myophorella) schulzi, new species Plate 8, figures 8, 9
Holotype.—MOZ P3075/1, consisting of a poorly preserved right valve.
Paratypes.—MOZ P3075/2, 3, and 4, three poorly preserved adult right valves in yellowish-white calcar- enites.
Type locality.x—Camino nuevo a Los Molles (Lo- cality 34), Dept. Zapala (39°13’S, 70°05'W), Picun Leu- faa Formation (Leanza, 1973), Mendoza Group (Groe- ber, 1946).
Etymology.—This species is dedicated to Enrique Schulz (Zapala, Neuquén) a friend of the Museum Juan Olsacher.
Diagnosis.—Myophorella of medium size, charac- terized by very few, widely spaced and uncurved flank costae, which bear isolated and rounded, relatively large tubercles. Area narrow, transversely ornamented by low ridges arising from the tubercles of the marginal carina.
Measurements (in mm).—
Specimen No. IF H WwW H/L W/L MOZ P3075/1 52 42 10 0.80 0.19
Description.—Right valves of medium size. Um- bones not prominent, opisthogyrous, very anteriorly situated. Dorsal margin long, almost straight. Dorso- posterior angle rounded. Ventral margin very convex, curving evenly into the slightly convex éanterior mar- gin. Flank occupying three-fourths of the shell surface, ornamented by no more than 10 very widely spaced straight costae. These bear isolated, rounded, relatively large tubercles. Marginal carina not well developed, demarcated by transversely elongated tubercles cor- responding to each flank costae. Area narrow, trans- versely ornamented by shallow ridges arising from the tubercles of the marginal carina, apparently asymmet- rically divided by a submedian groove. Escutcheon not recognizable, probably very narrow.
Remarks.—This new species can be easily distin- guished from any other known species of Myophorella Bayle by its extremely low number of flank costae which are almost straight instead of concavely curved as in most myophorellids, and by the presence of a some- what transversely rugate area. These features make this species very similar to Steinmanella Crickmay, a genus which arose in the Tithonian and flourished in the Neocomian with increasing diversity. Myophorella (M.) schulzi, n. sp. shows some affinities with Myophorella mearnsi (Stoyanow, 1949, p. 78, pl. 12, fig. 5) from the Upper Aptian of Arizona, but the North American species differs in having: (1) a more subquadrangular
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 31
shape; (2) a relatively larger size; and (3) very well developed tubercles along its whole marginal carina.
Age and occurrence.—Upper Tithonian, Substeuer- oceras koeneni Zone, Pictin Leufu Formation; Camino nuevo a Los Molles (Locality 34), Dept. Catan Lil, Neuqueén, Argentina.
Subgenus PROMYOPHORELLA Kobayashi and Tamura, 1955
Type species.—Myophorella (Promyophorella) sig- moidalis Kobayashi and Tamura, 1955, Bajocian, Ja- pan.
Diagnosis.—Myophorella with narrow and uninter- rupted subconcentric costae on the flanks bearing very small tubercles or beads regularly aligned on their crests. These may be obsolete in some species (Kobayashi and Tamura, 1955; Leanza, 1981).
Distribution.— Middle Jurassic to Neocomian. Cos- mopolitan.
Discussion.— Although Cox (1969, p. N485) and Poulton (1979, p. 27) considered the subgenus Pro- myophorella Kobayashi and Tamura (1955) as a junior synonym of Myophorella Bayle, the presence of flank costae with or without very small tubercles is consid- ered to be an important morphological feature that allows a division between these two taxa. Fleming (1987, p. 36) considered Promyophorella as a junior synonym of Scaphogonia Crickmay, 1930b (type spe- cies: Scaphogonia argo Crickmay, 1930b, pl. 5, figs. a, b) on the basis that Kobayashi and Tamura (1955) included Crickmay’s species in the list of species as- signed to Promyophorella. This view 1s not supported, inasmuch as Scaphogonia argo, placed in Myopho- rella by Cox (1969, p. N485) and Poulton (1979, p. 31), displays flank costae with well-developed tuber- cles, and a minor break occurring in the anterior part of the flank, a feature which is unknown in any other species of Promyophorella. For this reason, the author considers Scaphogonia as a junior synonym of My- ophorella Bayle, in agreement with Cox (1969) and Poulton (1979), and maintaining Promyophorella Ko- bayashi and Tamura as a valid subgenus of Myopho- rella.
Myophorella (Promyophorella) praescabroidea (Jaworski, 1916) Plate 3, figures 5, 6 Trigonia praescabroidea Jaworski, 1916, p. 385, pl. 5, figs. 5a, b (=Jaworski, 1925, p. 386, pl.1, figs. Sa,b).
Myophorella (Promyophorella) praescabroidea (Jaworski). Levy, 1966, p. 240; Leanza and Garate, 1987, p. 212, pl. 3, figs. 8, 9.
Description.—Shell of medium size, elongated. Slightly inflated anteriorly, posteriorly attenuated. Umbones prominent, opisthogyrous, very anteriorly
situated. Dorsal margin concave. Dorsoposterior angle slightly obtuse. Posterior margin very short. Ventro- posterior angle not known. Ventral margin broadly convex, curving evenly into the convex anterior mar- gin. Flank ornamented by nearly 20 subconcentric beaded costae, with intercostal spaces becoming wider toward the ventral margin of the shell. Marginal carina well defined, formed by a beaded keel. Area orna- mented by narrow transverse costellae which are more numerous than those of the flank. Escutcheon short, narrow and excavated, completely smooth.
Material.—One adult hypotype specimen, MOZ P0953/2, a complete shell, relatively well preserved shell.
Measurements (in mm).—
Specimen No. IE H W H/L W/L MOZ P0953/2 34 24 9 0.70 0.26
Remarks.—This species is very important because it represents in South America the Middle Jurassic ancestor of Pterotrigonia van Hoepen (1929), a char- acteristic Upper Jurassic and Cretaceous genus. My- ophorella (P.) praescabroidea (Jaworski) has some af- finities with Myophorella (M.) agniaensis Levy (1966, p. 283, figs. la—b) from the Liassic of Pampa de Agnia, Chubut, Argentina. Both of these species, however, have a comparatively less club-shaped form, larger area, and better defined tubercles.
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, Neuquén, Argentina.
Myophorella (Promyophorella) garatei Leanza, 1981 Plate 12, figures 1-4
Myophorella (Promyophorella) garatei Leanza, 1981, p. 4, figs. 1-7; Leanza and Garate, 1987, p. 212, pl. 13, figs. 8-11.
Description.—Shell small, subtrigonal, somewhat anteriorly inflated. Umbones opisthogyrous, situated in the anterior one-fourth of the shell. Dorsal margin concave. Dorsoposterior angle slightly obtuse. Poste- rior margin short. Ventroposterior angle almost 90°. Ventral margin broadly convex, curving evenly into the convex anterior margin. Flank occupying four-fifths of the shell surface, ornamented anteriorly by subcon- centric costae which bear, near the umbonal region, weak transverse crenulations; toward the anterior and ventral margins the costae tend to be smooth, thicker, and more widely separated. On the posterior flank the costae become narrower and more crowded, inter- secting the ventral margin almost perpendicularly. Both marginal and escutcheon carina well developed. Area
32 BULLETIN 343
with submedian sulcus, ornamented with transverse costellae. Escutcheon elongated, transversely ridged. Commissural plane crenulate.
Material.—Four topotype adult specimens, MOZ P0930/4—7, complete shells, very well preserved. The specimen MOZ P0930/4 shows a ventrally directed V-shaped inflection on the anterior flank costae (see Leanza and Garate, 1987, pl. 13, figs. 8a—b).
Measurements (in mm).—
Specimen No. IL lal W H/L W/L MOZ P0930/4 24 19 6 0.79 0.25
MOZ P0930/6 19 16 Se) 0.84 0.28
Remarks.—Myophorella (P.) garatei Leanza (1981) is closely related to Myophorella (P.) hillebrandti Reyes and Pérez (1985, p. 95, pl. 1, figs. 1-20) from the Neo- comian Pedernales Formation, Chile, but the Argen- tine species differs by: 1) its smaller size; 2) different shell shape; and 3) more densely costulate flank. My- ophorella (Promyophorella) eufalensis (Gabb in Myers, 1968, p. 61, pl. 10, fig. 6), a species widely distributed in the Upper Cretaceous of Mexico and southern Unit- ed States, is a very closely related species, but differs from M. (P.) garatei Leanza in having: 1) a more elon- gate shell; 2) the area occupying a smaller surface of the shell; and 3) the marginal carina not well devel- oped.
The specimen MOZ P0930/4 shows a ventrally di- rected V-shaped inflection on the anterior flank. The author has observed this anomaly in a few specimens (see Leanza and Garate, 1987, p. 213, pl. 13, figs. 8a— b), and these might well constitute a new variety or subspecies.
Age and occurrence.—Lower and Middle Hauteri- vian, Lyticoceras pseudoregale and Holcoptychites neu- quensis Zones, Agrio Formation; Cerro Mesa, Covun- co (Locality 8), Dept. Zapala, Neuquén, Argentina.
Myophorella (Promyophorella) hillebrandti Reyes and Pérez, 1985 Plate 8, figure 6
Myophorella (Myophorella) hillebrandti Reyes and Perez, 1985, p. 95, pl. 1, figs. 1-20.
Description.—Shell small, longer than high. Um- bones very anteriorly situated. Dorsal margin straight. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle very acute. Ventral mar- gin widely convex, curving evenly into the convex an- terior margin. Flank occupying four-fifths of the shell surface, ornamented by scarce, subconcentric costae in its anterior part, and ventroposteriorly sloping costae in its posterior portion. The costae are smooth or con- tain some obsolete, small beads. Area narrow, orna-
mented by very weak, transverse striae. Escutcheon not known.
Material.—One hypotype, probably an adult speci- men, MOZ P3075, consisting of a well preserved frag- ment of a left valve.
Measurements (in mm).—
Specimen No. 1b H WwW H/L W/L MOZ P3075 19 15 4 0.78 0.21
Remarks.—The specimen strongly agrees with My- ophorella hillebrandti Reyes and Pérez (1985, p. 95, pl. 1, figs. 1-20) from the Neocomian of northern Chile. Although Reyes and Pérez (1985) originally included this species in the subgenus Myophorella s.s., the lack or obsolescence of tubercles in the flank costae favors its assignment to the subgenus Promyophorella Ko- bayashi and Tamura.
Age and occurrence.—Middle Tithonian, Aulacos- phinctes proximus Zone, Carrin Cura Formation; For- tin 12 de Mayo (Locality 23), Dept. Catan Lil, Neu- quén, Argentina.
Subgenus HAIDAIA Crickmay, 1930a (emend. Kobayashi and Tamura, 1955)
Type species.—Trigonia dawsoni Whiteaves, 1876, Jurassic, British Columbia, Canada.
Diagnosis.—Myophorella with subconcentric and uninterrupted costae on the flanks, which are charac- terized by narrow ridges and grooves respectively ex- tending from tubercles and depressions. These give rise to crenulations in their ventral parts (Kobayashi and Tamura, 1955, p. 99).
Distribution.— Middle Jurassic to Cretaceous. Cos- mopolitan.
Myophorella (Haidaia) volkheimeri Leanza and Garate, 1987 Plate 12, figures 8-12
Myophorella (Haidaia) volkheimeri Leanza and Garate, 1987, p. 213, pl. 6, figs. 6-9.
Description.—Shell moderately small, inequivalve. Umbones opisthogyrous, very anteriorly situated. Dorsal margin slightly concave, with a slight expansion in its middle part. Dorsoposterior angle obtuse. Pos- terior margin very short. Ventroposterior angle almost 90°. Ventral and anterior margins broadly convex. Flank occupying four-fifths of the shell surface, ornamented by 15-16 fine and prominent subconcentric costae. The first 10-11 costae in the anterior flank bear narrow ridges and grooves on their ventral part, producing the characteristic crenulations of the subgenus. These cos- tae are concave-curved, and progressively more sep- arated from each other toward the ventral and anterior margins. The last five to six costae situated in the pos-
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 33
terior flank are more crowded, intersecting the ventral margin almost perpendicularly. The marginal and es- cutcheon carinae contain sharp beads on their distal portion. Area ornamented by fine transverse costellae, asymmetrically divided by a submedian sulcus. Es- cutcheon elongated, ornamented by very fine and dis- tant, transverse costellae, with a little protruding ex- pansion in its middle part. Commissure plane slightly crenulated.
Material.—Three adult specimens, MOZ P1752/1, the holotype (see H. A. Leanza and Garate, 1987, pl. 6, figs. 7-9) a complete shell; MOZ P1752/2 and 3, the original paratypes, consisting of complete shells with both valves well preserved.
Measurements (in mm).—
Specimen No. 15 H WwW H/L W/L MOZ P1752/1 17 14 3 0.82 0.18 MOZ P1752/2 21 19 4 0.90 0.19 MOZ P1752/3 20 15 4 0.75 0.20
Remarks.—The subgenus Haidaia, according to the emended diagnosis of Kobayashi and Tamura (1955), is characterized by shells very similar to Promyopho- rella Kobayashi and Tamura, but which display char- acteristic crenulations on the ventral part of the costae. This feature is well represented in M. (H.) volkheimeri Leanza and Garate, and it might have played an im- portant role in the mode of burrowing of this species. Myophorella (H.) crenulata Kobayashi and Tamura (1955, p. 100, pl. 5, figs. 8-10) from the Jurassic of Soma Mountains, Fukushima Prefecture, Japan, is a closely related species, but differs from M. (/.) volkhei- meri in: 1) having a more elongate shell shape; and 2) the flanks occupying a smaller proportion of the shell surface. Myophorella (H.) elegans Baily (in Woods, 1906, p. 293, pl. 35, figs. 3-4) from the Cretaceous of South Africa, is a comparable species, but differs from M. (H.) volkheimeri in having: 1) a more densely cos- tulate flank, and 2) a different shell shape.
Myophorella (Haidaia) elguetai, n. sp. (this paper) from the Upper Tithonian of Cerrito Caracoles area, Neuquén, is also a closely related species, but differs in having: (1) a different shell shape, (2) an poorly- defined marginal carina, (3) a very weakly ornamented area, and (4) proportionally fewer costae on the flanks.
Age and occurrence.—Lower and Middle Hauteri- vian, Lyticoceras pseudoregale and Holcoptychites neu- quensis Zones, Agrio Formation; Cerro Mesa, Covun- co (Locality 8), Dept. Zapala, Neuquén, Argentina.
Myophorella (Haidaia) elguetai, new species Plate 9, figures 9-11 Holotype.—MOZ P3067, consisting in a very well
preserved right valve, in a hard, pink-yellowish, coarse- grained limestone.
Paratypes.—Seven specimens, all adults unless oth- erwise indicated: MOZ P2486/2, a well preserved left valve; MOZ P5767, a well preserved complete shell; MOZ P5768, a poorly preserved right valve; MOZ P5769, a very well preserved right valve; MOZ P5770, a broken right valve; MOZ P3898, a complete juvenile shell, well preserved; MOZ P5766, a complete shell with both valves poorly preserved.
Type locality.—Cerrito Caracoles (Locality 11), Dept. Zapala (38°49'S, 70°09”W), Piciun Leufai Formation (Leanza, 1973), Mendoza Group (Groeber, 1946).
Etymology.— After Ramona and Domingo Elgueta, inhabitants of Aguada del Overo, and friends of the Museum Juan Olsacher.
Diagnosis.—Shell of small to medium size, slightly longer than high. Umbones very anteriorly situated. Flank very wide, ornamented by equally spaced sub- concentric costae, bearing characteristic crenulations on their ventral part. Marginal carina poorly defined, except near umbo. Area very narrow, transversely or- namented by weak costellae. Escutcheon apparently smooth.
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P3067 19 14 5 0.73 0.26 MOZ P5767 18 15 4 0.83 0.22 MOZ P2486/2 34 30 7 0.88 0.20
Description.—Shell of small to medium size, trigo- nally ovate, slightly longer than high. Umbones opis- thogyrous, very anteriorly situated. Dorsal margin con- cave. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle slightly obtuse. Ven- tral margin broadly convex, curving evenly into the slightly convex anterior margin. Flank very wide, oc- cupying five-sixths of the shell surface, ornamented by 12-14 subconcentric costae with intercostal spaces widening toward the ventral and anterior margins. The costae exhibits characteristic crenulations on their ven- tral side. Area very narrow, transversely ridged by faint costellae. Marginal carina weakly developed. Escutch- eon poorly preserved, apparently smooth.
Remarks.—Myophorella (Haidaia) elguetai, n. sp. can readily be assigned to the subgenus Haidaia Crick- may (1930a) emend. Kobayashi and Tamura (1955) on the basis of the myophorellid shell shape, and the characteristic crenulations on the ventral side of the flank costae. The species 1s recognized by its slightly longer than high shell shape, very wide flanks, and poorly defined marginal carina. Myophorella (Haidaia) elguetai, n. sp. differs from the Hauterivian MM. (/7.) volkheimeri Leanza and Garate (1987, p. 213, pl. 6, figs. 6-9) (herein described) in having: (1) a lesser num- ber of flank costae; (2) a less well defined marginal
34 BULLETIN 343
carina and (3) a slightly concave dorsal margin, instead of one with a slight expansion on its middle part, as in M. (H.) volkheimeri. Myophorella (Haidaia) elgue- tai, n. sp. also differs from the Jurassic 4. (H.) cren- ulata Kobayashi and Tamura (1955, p. 100, pl. 5, figs. 8-10) from the Soma Mountains, Fukushima Prefec- ture, Japan, in having: (1) shorter valves, (2) flanks occupying a larger portion of the shell surface, and (3) more poorly defined marginal carina.
Age and occurrence.— Upper Tithonian, Substeuer- oceras koeneni Zone, Pican Leufii Formation; Cerrito Caracoles (Locality 11), Dept. Zapala, Neuquén, Ar- gentina.
Genus SCAPHOTRIGONIA Dietrich, 1933
Type species.—Trigonia navis Lamarck, 1819, Aalenian, Alsacia.
Diagnosis.—Trigonally ovate, with prominent um- bones. Marginal carina and escutcheon carina poorly defined except in early growth stages. Area initially transversely ridged, and subsequently smooth, or per- sistently smooth. Escutcheon smooth. Anterior end of shell broadly flattened. Flank ornamented by two sets of costae: the anterior with subconcentric costae, usu- ally terminating in tubercles, and the posterior set with ventroposteriorly sloping, usually tuberculated, costae. Both sets of costae are separated on the anterior flank by a smooth band (Cox, 1969; Leanza and Garate, 1986).
Distribution.—Lower Jurassic (Upper Liassic) to Middle Jurassic (Bajocian). North and South America (Argentina), Europe.
Scaphotrigonia rierafonti Leanza and Garate, 1986 Plate 3, figures 3, 4
Scaphotrigonia rierafonti Leanza and Garate, 1986, p. 156, fig. 2: 1-8; Leanza and Garate, 1987, p. 214, pl. 3, figs. 4, 5, pl. 4, figs. 4-6.
Description.—Shell small, longer than high. Um- bones somewhat prominent, opisthogyrous, very an- teriorly situated. Dorsal margin slightly concave. Dor- soposterior angle obtuse. Posterior margin short. Ventroposterior angle almost 90°. Ventral and anterior margins forming a broad and continuous convex curve up to the beaks. Flank ornamented by two series of costae interrupted by a smooth band. Marginal carina defined by a continuous line. Area smooth. Escutcheon smooth, narrow and elongated almost up to the pos- terior margin.
Material.—One adult topotype, MOZ P0931, acom- plete shell with both valves very well preserved (see Leanza and Garate, 1987, pl. 4, figs. 4-6).
Measurements (in mm).—
Specimen No. 1, H WwW H/L W/L MOZ P0931 24 19 5 0.79 0.20
Remarks.—The differences between Scaphotrigonia rierafonti and Scaphotrigonia navis are clear, and have been described by Leanza and Garate (1986). “Sca- photrigonia”’ somensis Kobayashi and Tamura (1957, p. 40, pl. 1, figs. 1-3) from the Middle Jurassic of Japan belongs to the genus Scaphorella Leanza, Pérez and Reyes (1987).
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, Neuquén, Argentina.
Genus SCAPHORELLA Leanza, Pérez, and Reyes, 1987
Type species.—Trigonia leanzai Lambert, 1944, Middle Jurassic (Bajocian-Bathonian), Neuquén, Ar- gentina.
Diagnosis.—Shell of medium to large size, trigonally rounded or somewhat elongated. Shell moderately con- vex. Umbones prominent, opisthogyrous, very ante- riorly situated. Flank ornamented by two series of tu- berculated costae, the anterior one radial and the posterior one radial-retroverse; these meet the ventral margin at nearly 90°. Area transversely ridged, asym- metrically divided by a submedian groove. Escutcheon wide, lanceolate and excavated, ornamented posteri- orly by the continuation of the costae of the area (Lean- za, Pérez and Reyes, 1987).
Distribution.—Middle Jurassic. North and South America, Japan.
Scaphorella leanzai (Lambert, 1944) Plate 3, figures 1, 2
Trigonia leanzai Lambert, 1944, p. 362, pl. 1, figs. 5, 6. Myophorella (Promyophorella) leanzai (Lambert). Levy, 1966, p. 240.
Myophorella leanzai (Lambert). Camacho and Riccardi, 1978, table 9
2 Myophorella cf. argo (Crickmay). Poulton, 1979, p. 32, pl. 4, figs. 18-22
**Myophorella” leanzai (Lambert). Leanza and Garate, 1987, p. 213, pl. 4, figs. 7-10.
Scaphorella leanzai (Lambert). Leanza, Pérez and Reyes, 1987. p. 84, pl. 1., figs. 1-4.
Description.—Shell large, subrounded in shape, al- most as long as high. Umbones prominent, opistho- gyrous. Dorsal margin slightly concave. Dorsoposter- ior angle obtuse. Posterior margin relatively short. Ventroposterior junction obtuse. Ventral margin broadly convex. Anterior margin slightly rounded. Flank ornamented by two series of tuberculated costae,
TRIGONID BIVALVES OF ARGENTINA: LEANZA 35
the anterior set radial, and the posterior one radial- retroverse in direction, meeting the ventral margin at nearly 90°. Area well defined, occupying one-fourth of the surface of the shell, ornamented by transverse and somewhat rugate costae, asymmetrically divided by a submedian groove. Marginal carina well defined, bear- ing progressively more well defined tubercles toward the ventroposterior junction. Escutcheon carina bear- ing at first oblique, and subsequently transversely en- larged tubercles. Escutcheon lanceolate, wide, orna- mented in its proximal part by growth lines, and in its distal part by diagnostic transverse costae arising from the area.
Material.—Two specimens. One adult hypotype, a left valve, MOZ P0919/1 (Los Pozones), very well pre- served (see Leanza and Garate, 1987, pl. 4, figs. 7-9; Leanza, Pérez and Reyes, 1987, pl. 1, figs. 2a, b, c), and one topotype, a fragmentary left valve MOZ P4557 (Canadon Nancu Huau, Chacaico).
Measurements (in mm).—
Specimen No. L H W H/L W/L
MOZ P0919/1 55 54 17 0.90 0.38
Remarks.—Scaphorella leanzai (Lambert) is very closely related to Myophorella sp. cf. M. argo (Crick- may, 1930b) as figured by Poulton (1979, p. 32, pl. 4, figs. 18-22) from the Middle (now Early) Bajocian Kialagvik (Alaska) and Weberg (Oregon) Formations, western United States. Although the poor preservation of the North American species precludes confirmation that they are conspecific, this taxon has been placed in the genus Scaphorella by Leanza, Pérez and Reyes (1987, p. 85).
““Scaphotrigonia”’ somensis Kobayashi and Tamura (1957, p. 40, pl. 1. figs. 1-3) from the Middle Jurassic of Soma County, Fukushima Prefecture, Japan, may also be included in Scaphorella on the basis of its shell shape, similar flank ornamentation pattern, and in having area pervasively ornamented by transverse cos- tae.
Age and occurrence.—Early Bajocian to Early Bath- onian, Emileia giebeli to Cadomites—Tulitidae Zones, Lajas Formation; Los Pozones (Locality 15), Dept. Za- pala, and Canadon Nancu Huau, Chacaico (Locality 35), Neuquén, Argentina.
Scaphorella kruusei Leanza and Garate, 1987 Plate 3, figures 14, 15 “Myophorella” kruusei Leanza and Garate, 1987, p. 214, pl. 4, fig. Ne
Scaphorella kruusei Leanza and Garate. Leanza, Pérez and Reyes, 1987, p. 85.
Description.—Shell large, subrectangular, much lon- ger than high. Umbones situated in the anterior one-
fifth of the shell. Dorsal margin almost straight. Dor- soposterior angle widely obtuse. Posterior margin short. Ventroposterior angle obtuse. Ventral margin very slightly convex. Anteroventral junction well defined. Anterior margin almost straight. Flank ornamented by two sets of beaded costae, the anterior radially orient- ed, and the posterior ventroposteriorly inclined. Area and escutcheon forming a flattened surface. Area oc- cupying one-third of the shell surface, ornamented by transverse costae. Escutcheon wide, excavated and smooth.
Material.—One adult topotype specimen, MOZ P1813, consisting of a rather well preserved left valve.
Measurements (in mm).—
Specimen No. IE, H WwW H/L W/L MOZ P1813 59 42 12 0.71 0.20
Remarks.—Based on the original description, Dam- borenea (in Riccardi, Westermann and Damborenea, 1990, p. 118) considered Scaphorella kruusei Leanza and Garate as a junior synomym of Scaphorella leanzai (Lambert). The specimen described herein, however, provides more details of this taxon, and it can be dem- onstrated that it differs from Scaphorella leanzai by its shell shape that results in: (1) a subrectangular out- line, much longer than high; (2) umbones more ante- riorly situated; (3) anterior margin which is almost straight; and (4) a better defined anteroventral junc- tion. In addition, S. Aruusei has a narrower area, and lacks a submedian groove. For these reasons this spe- cies is considered to be valid.
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Fortin 12 de Mayo (Locality 23), Dept. Catan Lil, Neuquén, Argentina.
Scaphorella camachoi, new species Plate 3, figures 12, 13
Holotype.—MOZ P4920/1, a complete small adult, well preserved right valve, fossilized in a fine-grained, reddish-brown sandstone.
Paratype.—MOZ P4920/2, an small adult, well pre- served left valve.
Type locality.—Maquina Cura, Chacaico (Locality 21), Dept. Catan Lil (39°20'S, 70°22'W), Lajas For- mation (Weaver, 1931), Cuyo Group (Groeber, 1946).
Etymology.—The species is dedicated to the Argen- tine paleontologist Dr. Horacio H. Camacho, of Bue- nos Aires.
Diagnosis.—Shell moderately small, trigonally ovate. Flank occupying two-thirds of the shell surface, or- namented by two sets of costae: the anterior one sub- concentric, and the posterior one following a ventro- posterior direction. Protruding marginal carina. Area
36 BULLETIN 343
ornamented by narrow, transverse costellae. Escutch- eon unknown. Measurements (in mm).—
Specimen No. IE H WwW H/L W/L MOZ P4920/1 13 11 4 0.84 0.30 MOZ P4920/2 14 11 5 0.78 0.35
Description.—Shell moderately small, trigonally ovate, with the anterior part broadly flattened. Um- bones opisthogyrous, very anteriorly situated. Dorsal margin straight. Dorsoposterior angle slightly obtuse. Posterior margin relatively long. Ventroposterior angle obtuse. Ventral margin slightly convex, curving abruptly into the slightly straight anterior margin. Flank occupying two-thirds of the shell surface, ornamented by two sets of costae: the anterior consisting in seven subconcentric costae; the posterior with only five ven- troposteriorly inclined serrated costae with intercostal spaces equal to two times the thickness of each costa. A protruding marginal carina is present. Area wide, ornamented throughout by very narrow transverse cos- tellae. Escutcheon unknown.
Remarks.—Scaphorella camachoi, n. sp. differs from Scaphorella leanzai (Lambert, 1944; herein described), also from Bajocian beds of the Lajas Formation, in the following details: (1) smaller size; (2) the flank occupies a smaller proportion of the shell surface; (3) the area is proportionally wider; (4) the flank is less densely costate, and (5) the marginal carina is very well de- veloped. Scaphorella kruusei Leanza and Garate (1987, p. 214, pl. 4, fig. 1) from the Middle Bajocian Lajas Formation at Fortin 12 de Mayo (Neuquén), has a dif- ferent shell shape, with subrectangular outline which gives a different morphological pattern to the shell, and it lacks a protruding marginal carina. Trigonellina Parnes, 1981 (type species: Myophorella (Trigonellina) delicata Parnes, 1981) from the Bajocian Makhtesh Ramon Formation, Israel, is very similar in size and shape, but the area is ornamented by radial and trans- verse costellae.
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Maquina Cura, Chacaico (Locality 21), Dept. Catan Lil, Neuquén, Argentina.
Subfamily VAUGONIINAE Kobayashi, 1954 Genus VAUGONIA Crickmay, 1930b
Type species.— Vaugonia veronica Crickmay, 1930b, Middle Jurassic, British Columbia, Canada.
Diagnosis.—Trigonally ovate to elongate. Umbones opisthogyrous, anteriorly situated. Escutcheon, area and flank distinctly demarcated by protruding carinae. Flank ornamented by distinctive costation, character-
ized by simple and/or tuberculate costae up to an ad- vanced stage of growth, with the V-shaped inflection situated in a relatively posterior position. Area bipar- tite, transversely costate (Crickmay, 1930b; Cox, 1969; Poulton, 1979; Reyes and Pérez, 1984).
Distribution.— Lower to Upper Jurassic. Cosmopol- itan.
Discussion.—The distinctive flank costation char- acteristic of Vaugonia Crickmay is formed by the in- tersection of the anterior and posterior sets of costae, forming a down-pointing (i.e., ventrally-directed) V-shaped inflection, which is hereafter referred to as ““vaugonic costation’’. This kind of costation may be present in other genera, including Jotrigonia, Anditri- gonia, Paranditrigonia, Lambertrigonia, Apiotrigonia, Andivaugonia, and in some growth stages of Bucho- trigonia and Syrotrigonia. The position of the V-shaped inflection on the flank, the angle of divergence between both sets of costae, and the numbers of costae on the anterior portion of the flank, are of diagnostic value. ‘““Vaugonic costation”’ is here regarded, however, as a secondary character. The nature of the ornamentation of the area and the escutcheon, as well as the charac- teristics of the marginal carina are considered of greater importance in making taxonomic determinations at the generic level (see ‘‘Philosophical Considerations”’, p. 14).
Vaugonia chunumayensis (Jaworski, 1916) Plate 2, figure 15
Trigonia chunumayensis Jaworski, 1916, p 384, pl. 5, fig. 4; (=Ja- worski, 1925, p. 83, pl. 1, fig. 4); Weaver, 1931, p. 236.
Vaugonia (Vaugonia) chunumayensis (Jaworski). Reyes and Pérez, 1978, p. 9, pl. 2, fig. 3
Vaugonia chunumayensis (Jaworski). Leanza and Garate, 1987, p. 219, pl. 4, fig. 3.
Description.—Shell small, strongly elongated. Um- bones opisthogyrous, prominent, situated in the an- terior one-fourth of the shell. Dorsal margin concave. Dorsoposterior angle obtuse. Posterior margin short. Ventroposterior angle acute. Ventral margin straight, curving evenly to the strongly convex anterior margin. Flank occupying two-thirds of the shell surface, or- namented by narrow and elevated costae forming ven- trally directed V-shaped inflection in a relatively pos- terior position; some beads may be present in this zone. Area bipartite, with median groove, and transverse growth lines. Marginal carina well defined from the beaks to the ventroposterior junction. Escutcheon with some transverse, very faint, growth lines.
Material.—Three adult hypotype specimens, MOZ P1903, a well preserved right valve, MOZ P3193/1 and 2, two relatively well preserved right valves.
Measurements (in mm).—
TRIGONID BIVALVES OF ARGENTINA: LEANZA 37
Specimen No. Ie, H WwW H/L W/L
MOZ P1903 45 27 6 0.60 0.13
Remarks.— Pérez, Bird and Reyes (1987, p. 36) have recently assigned specimens formerly classified as Vau- gonia (Vaugonia) chunumayensis (Jaworski; see Reyes and Pérez, 1978, 1979) from the Berriasian of Lo Valdés Formation, Central Cordillera of Chile, to Virgotri- gonia hugoi (Leanza). Therefore, Vaugonia chunu- mayensis (Jaworski) can be now regarded as an exclu- sively Middle Jurassic species.
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, Neuquén, Argentina.
Vaugonia rectangularis (Gottsche, 1878) Plate 2, figure 13 Trigonia rectangularis Gottsche, 1878, p. 26, pl. 6, figs. Sa, b. Vaugonia (Vaugonia) rectangularis (Gottsche). Perez and Reyes, p. 18, pl. 3, figs. 8, 9 Vaugonia rectangularis (Gottsche). Leanza and Garate, 1987, p. 219, pl. 4, fig. 2.
Description.—Shell small, strongly elongated. Um- bones opisthogyrous, prominent, situated in the an- terior one-fifth of the shell. Dorsal margin strongly concave. Dorsoposterior angle obtuse. Posterior mar- gin very short. Ventroposterior angle acute. Ventral margin slightly convex, curving evenly into the convex anterior margin. Flank ornamented by widely sepa- rated, narrow, elevated, tuberculate costae, forming a ventrally pointing V-shaped inflection in a relatively posterior position. Area narrow, bipartite, ornamented by faint transverse growth lines; median groove pres- ent. Marginal carina protruding throughout its entire length. Escutcheon lanceolate and narrow, probably smooth.
Material.—One adult hypotype specimen, MOZ P1753, consisting of a right valve with the anteroven- tral part of the shell broken (see Leanza and Garate, 1987, pl. 4, fig. 2).
Measurements (in mm).—
Specimen No. IL, H WwW H/L W/L MOZ P1753 35 21 5 0.60 0.14
Remarks.— Vaugonia rectangularis (Gottsche) is very similar to the associated Vaugonia chunumayensis (Ja- worski, 1915, p. 384, pl. 5, fig. 4; herein described), but differs in having a somewhat different style of cos- tation, with persistent small tubercles in the flank cos- tae.
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas
Formation; Barda Negra Sur (Locality 16), Dept. Za- pala, Neuquén, Argentina.
Genus ANDIVAUGONIA, new name (= Lambertiella Cooper, 1991)
Type species.— Trigonia radixscripta Lambert, 1944, Middle Jurassic (Early Bajocian/Early Bathonian), Ne- uquén, Argentina.
Diagnosis.—Trigonally ovate to elongate, somewhat inflated. Demarcation between escutcheon, area and flank poorly defined. Area wide, generally bipartite, smooth or transversely ridged by growth lines or rugae. Marginal carina poorly defined in the proximal portion of the shell, becoming obsolete in the distal part. Flank ornamented by vaugonic costae. Escutcheon smooth.
Distribution.— Middle Jurassic (Lower Bajocian to Lower Callovian). Argentina and Chile.
Etymology.—Andi= Andes, meaning Vaugonia from the Andes.
Discussion.— Cooper (1991) proposed the new genus Lambertiella, with Trigonia radixscripta Lambert as type species. I agree that this species probably repre- sents a distinct genus. The name Lambertiella, how- ever, is preoccupied by Lambertiella Chechi-Rispol, 1917 (Echinoidea) and so is unavailable. The new name Anditrigonia 1s proposed in replacement.
Trigonia radixscripta Lambert (1944) is a very com- mon species in Middle Jurassic strata from western central Argentina, and it has been the subject of some uncertainty regarding its taxonomic position. Kobay- ashi and Mori (1955, p. 75) were the first to assign the species of Lambert to the genus Jotrigonia van Hoepen. This view was only partially accepted by later workers who included 7. radixscripta as well in Jotrigonia (see Reyes and Pérez, 1978, p. 21, Reyes and Pérez, 1979, p. 20; Leanza and Garate, 1987, p. 225), in Trigonia (see Reyes and Pérez, 1984, p. 40) or in Vaugonia (see Leanza, Pérez and Reyes, 1987, p. 86) without com- ments. It is worth noting, however, that Jotrigonia van Hoepen (type species: J. crassitesta van Hoepen, 1929, p. 6, pl. 2, fig. 4; pl. 3, figs. 1-2) has the umbones in a much more central position of the shell, producing a very different morphological pattern to the shell with the ventrally pointing V-shaped inflection in a central position on the flank (see Fleming, 1987, p. 58). The genus Vaugonia Crickmay (type species: V. veronica Crickmay, 1930b, p. 53, pl. 7, figs. Sa—b) has the um- bones situated in a more anterior position of the shell. The affinities of Jotrigonia to Vaugonia, however, are only superficial. This genus is clearly characterized by mostly elongated representatives, with areas orna- mented by transverse costae, and the presence of a well developed marginal carina throughout its develop- ment. These features are clearly recognizable in elon- gated South American Vaugoniinae such as V’. sub-
38 BULLETIN 343
striata (Burmeister and Giebel, 1861), V. lycetti (Gottsche, 1878), V. rectangularis (Gottsche, 1878), V. praelonga (Gottsche, 1878), V. gottschei Moricke (1894), V. exotica (MOricke, 1894) and V. chunumay- ensis (Jaworski, 1915). Based on the lack of transverse costae in the area and the poor development of the marginal carina, restricted only to the proximal portion of the shell, it is proposed to institute the genus An- divaugonia, n. gen. with Trigonia radixscripta Lambert as type species. The new genus comprises a homoge- neous stock including the Middle Jurassic “7.” covun- coensis Lambert (1944) from Argentina and “‘ Vaugon- ia (V.)” fuenzalidai Reyes and Pérez (1984) and “Vaugonia (V.)” lissocostata Reyes and Pérez (1984) from Chile. All of these taxa are not very elongated, somewhat inflated forms characterized by smooth or poorly ornamented areas, and lacking well developed marginal carinae. On the basis of the general charac- teristics of the shell and the vaugonic style of costation on the flanks, the new taxon is placed in the subfamily Vaugoniinae Kobayashi.
The Jurassic Trigonia manflarum (Philippi, 1899, p. 77, pl. 34, fig. 4) from the Liassic—Bajocian (?) Lau- taro Formation, Chile, transferred doubtfully to Jotri- gonia by Nakano (1965, p. 19), is considered here to be a Vaugonia (?) (see Pérez and Reyes, 1989). There- fore, according to the new taxonomy proposed here, Totrigonia van Hoepen remains as an exclusively Cre- taceous genus characteristic of the southern circum- Pacific region. Apart from the differences between the genera Andivaugonia, n. gen., Vaugonia Crickmay (1930b) and Jotrigonia van Hoepen (1929) already re- ferred to, the new genus shows superficial affinities with Anditrigonia Levy (1967c) and with Anditrigonia (Par- anditrigonia) Reyes and Pérez (1983) especially in the shell shape, and in exhibiting a very poorly defined marginal carina. The areas, however, are totally dif- ferent among these taxa; the genus Anditrigonia shows transverse costellae on the proximal area, and the sub- genus Paranditrigonia exhibits radial costellae on the whole area.
Andivaugonia radixscripta (Lambert, 1944) Plate 4, figures 1-2, 4, 10 Trigonia radixscripta Lambert, 1944, p. 369, pl. 1, figs. 7, 8, pl. 6, fig. 1. Totrigonia radixscripta (Lambert). Kobayashi and Mori, 1955, p. 75;
Reyes and Pérez, 1978, p. 21, pl. 3, fig. 1; Leanza and Garate, 1987, pl. fig. 7.
Description.—Shell medium to large in size, very elongated. Umbones prominent, opisthogyrous, situ- ated in the anterior one-fifth of the shell. Dorsal margin almost straight, slightly concave. Dorsoposterior angle obtuse. Posterior margin relatively short. Ventropos- terior angle acute. Ventral margin slightly convex,
curving evenly into the convex anterior margin. Flanks occupying nearly three-quarters of the shell surface, ornamented by two sets of costae on the anterior and posterior flank respectively. The line of junction be- tween the two sets of costae begins in the umbonal region and terminates in the posterior portion of the ventral margin, forming a V-shaped inflection of 45° to 80°. The anterior set of costae, which is narrower than the posterior one, is characterized by some irreg- ularities forming a radix-like inflection on the mght valve, and a similar but inverted inflection in the left valve. The intercostal spaces are wider than the costae in the anterior set, and the relations are inverse in the posterior one. Area relatively wide, asymmetrically di- vided by a median carina containing in its posterior two-thirds transversely elongate swellings. The area is ornamented by transverse growth lines in the proximal region, and by transverse rugae in its distal portion. Marginal carina developed only in the umbonal region, subsequently undefined, forming a blunt crest. Es- cutcheon carina somewhat similar to the submedian carina. Escutcheon somewhat excavated, rather long, ornamented only by growth lines.
Material.—Ten adult hypotype specimens: MOZ P0936/2, a left valve with the umbonal region broken; MOZ P0936/3, a right valve (Canadon del Sapo); MOZ P4926, a poorly preserved right valve; MOZ P4571, complete, with both valves well preserved; MOZ P4572, a poorly preserved left valve; MOZ P4573, a well preserved right valve; MOZ P4574, a right valve with the area very well preserved; MOZ P4575, a right valve with the posterior part broken; MOZ P4576, a very well preserved right valve; MOZ P4577, a well preserved right valve (Maquina Cura). All the speci- mens are fossilized in a coarse-grained, brown, calcar- eous sandstone.
Measurements (in mm).—
Specimen No. 1b; H WwW H/L W/L MOZ P4571 58 42 14 0.72 0.24 MOZ P4572 83 48 17 0.57 0.20 MOZ P4573 72 47 18 0.65 0.25 MOZ P4576 80 47 19 0.58 0.23
Remarks.—Andivaugonia radixscripta (Lambert) is very closely related to Andivaugonia fuenzalidai (Reyes and Pérez, 1984, p. 37, pl. 1, figs. 1-13; pl. 2, figs. 8- 14) from the Upper Bathonian (?)-Lower Callovian Asientos Formation, northern Chile, especially in its large size and poorly developed carinae. But in the Chilean species the vaugonic pattern of the flank or- namentation does not reach the ventral margin of the shell, and it is replaced by isolated subhorizontal costae which are not present in the Argentine species (Reyes and Pérez, 1984, p. 40).
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 39
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Maquina Cura, Chacaico (Locality 21), Dept. Catan Lil, Neuquén, Argentina. Andivaugonia may also reach in Argentina the early Callovian Eu- rycephalites vergarensis Zone.
Andivaugonia covuncoensis (Lambert, 1944) Plate 4, figure 3
Trigonia covuncoensis Lambert, 1944, p. 360, pl. 1, fig. 1.
Vaugonia (Vaugonia) covuncoensis (Lambert). Reyes and Pérez, 1979, pl. 6, fig. 1.
Vaugonia covuncoensis (Lambert). Leanza and Garate, p. 219, pl. 3, fig. 11.
Description.—Shell small, trigonally ovate, posteri- orly enlarged and attenuated. Dorsal margin straight. Dorsoposterior angle almost 90°. Posterior margin very short. Ventroposterior angle obtuse. Ventral margin slightly convex, curving evenly into the convex ante- rior margin. Flank occupying almost the whole surface of the shell, ornamented by 10-15 fine, subconcentric costae which are parallel to the ventral margin. Acute V-shaped inflection of costae in the posterior flank, resulting in a lesser number of wider costae. Area nar- row and smooth. Marginal carina poorly defined in the proximal region, subsequently indistinct. Escutcheon smooth, bounded by a very poorly defined marginal carina.
Material.—One adult topotype specimen, MOZ P0932/1, complete shell, but with both valves poorly preserved (see Leanza and Garate, 1987, pl. 3, fig. 11).
Measurements (in mm).—
Specimen No. 1b H W H/L W/L MOZ P0932/1 40 33 12 0.83 0.30
Remarks.—The described specimen shows a smooth area and very weakly defined marginal and escutcheon carinae which are characteristic of the new genus An- divaugonia.
Age and occurrence.—Early Bajocian to Early Bath- onian, Emileia giebeli and Cadomites—Tulitidae Zones, Lajas Formation; Covunco Pavia (Locality 10), Dept. Zapala, Neuquén, Argentina.
Andivaugonia fuenzalidai (Reyes and Pérez, 1984) Plate 4, figure 11
Vaugonia (Vaugonia) fuenzalidai Reyes and Pérez, 1984, p. 37, pl. 1, figs. 1-13, pl. 2, figs. 8-14.
Description.—Shell large, oblong. Umbones prom- inent, opisthogyrous, situated in the anterior one-eighth of the shell. Dorsal margin straight. Dorsoposterior angle very obtuse. Posterior margin straight and rela-
tively short. Ventroposterior junction almost 90°. Ven- tral margin convex, curving evenly into the slightly convex anterior margin. Flank occupying two-thirds of the shell surface, ornamented on its anterior part successively from the umbo to the ventral margin by smooth or weakly beaded, vaugonic, subhorizontal and subconcentric costae. The posterior flank is character- ized by the ascending vaugonic branch of costae which are wide and smooth, and oriented in a subvertical direction. Area wide and subplanate, ornamented by faint, transverse growth lines, asymmetrically divided by a submedian groove. Marginal carina poorly defined in the umbonal region, subsequently undefined. Es- cutcheon carina poorly defined by a row of transversely elongate beads arising from the growth lines of the area. Escutcheon relatively wide and excavated, apparently smooth.
Material.—One adult hypotype specimen, MOZ P2314, a complete right valve.
Measurements (in mm).—
Specimen No. JE H W H/L W/L MOZ P2314 82 52 28 0.63 0.34
Remarks.—This species can be readily assigned to the genus Andivaugonia, n. gen. on the basis of its large size, weakly defined marginal carina, and the special costation of the anterior part of the flank, which show successively vaugonic, subhorizontal and subconcen- tric stages. At specific level the described specimen coincides with Andivaugonia fuenzalidai (Reyes and Pérez, 1984, p. 37, pl. 1, figs. 1-13; pl. 2, figs. 8-14) from the Upper Bathonian (?)-Lower Callovian Asien- tos Formation, northern Chile, and the specimen fig- ured by the Chilean authors in their pl. 2, fig. 13 is practically identical with the Argentine specimen. An- divaugonia fuenzalidai (Reyes and Pérez) shows strong resemblances with A. radixscripta (Lambert), the type species of Andivaugonia, n. gen., but in the first species the vaugonic pattern on the flank does not reach the ventral margin of the shell. 4. fwenzalidai (Reyes and Pérez) is cited here for the first time in the Middle Jurassic of west-central Argentina.
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humpriesianum Zones, Lajas Formation; Chacaic6 (Locality 21), Dept. Catan Lil, Neuquén, Argentina.
Andivaugonia lissocostata (Reyes and Pérez, 1984) Plate 4, figures 6-8
Vaugonia (Vaugonia) lissocostata Reyes and Pérez, 1984, p. 40, pl. 2, figs. 1-7.
Description.—Shell small, trigonally elongate. Um- bones opisthogyrous, situated in the anterior one-sixths
40 BULLETIN 343
of the shell. Dorsal margin concave. Dorsoposterior angle obtuse. Posterior margin short. Ventroposterior angle almost 90°. Ventral margin slightly convex, curv- ing evenly into the convex anterior margin. Flank oc- cupying three-fourths of the shell surface, ornamented by concentric costae in the umbonal region, then by smooth vaugonic costae with the junction between them anteroventrally inclined from the umbo toward the posterior part of the ventral margin. Area ornamented by faint transverse growth lines; asymmetrically di- vided by a narrow and shallow submedian groove. Marginal and escutcheon carinae poorly defined near the umbo, then undefined, forming a blunt crest in the distal portion. Escutcheon lanceolate, excavate and smooth.
Material.—Three hypotype juvenile specimens, MOZ P1821/1, somewhat broken, left valve; MOZ P1821/2, a poorly preserved left valve, and MOZ P4322, a poorly preserved left valve.
Measurements (in mm).—
Specimen No. 1 H WwW H/L W/L
MOZ P1821/1 20 15 5 0.75 0.25 MOZ P1821/2 32 27 8 0.84 0.25 MOZ P4322 20 13 7 0.65 0.35
Remarks.— Although juveniles, the described spec- imens are identical to 4ndivaugonia lissocostata (Reyes and Pérez, 1984, p. 40, pl. 2, figs. 7) from the Upper Bathonian (?)—Lower Callovian Asientos Formation of northern Chile. The assignment of this species to 4n- divaugonia, n. gen. is based on the less elongated shell shape and the presence of a very poorly defined mar- ginal carina which distinguishes it from other known species of Vaugonia. The most closely allied species is Andivaugonia covuncoensis (Lambert, 1944, pl. 1, fig. 1; herein described) but this species has anterior flank costae parallel to the ventral margin, whereas in An- divaugonia lissocostata the costae are posteroventrally inclined (see Reyes and Pérez, 1984, p. 41).
Age and occurrence.—Early Bajocian, Emileia gie- beli and Stephanoceras humphriesianum Zones, Lajas Formation; Fortin 12 de Mayo (Locality 23), Dept. Catan Lil, Neuquén, Argentina.
Subfamily STEINMANELLINAE Cooper, 1991 Genus STEINMANELLA Crickmay, 1930a
Type species.—Trigonia holubi Kitchin, 1908, Up- per Valanginian, southeastern Africa.
Diagnosis.—Oblong to subquadrangular. Flank or- namented by strong, concave, tuberculated costae. Area smooth except for tuberculate carinae, or transversely ridged by rugate costae that may or may not arise from the flank, and which may be asymmetrically divided by a submedian groove. Escutcheon variable in size,
containing oblique, strongly tuberculate ridges or rugae in most representatives (Crickmay, 1930a, Cox, 1969, Pérez, Reyes and Pérez, 1981).
Distribution.— Upper Jurassic (Tithonian) to Upper Cretaceous. Cosmopolitan, except for boreal regions.
Discussion.—The genus Steinmanella was proposed without an adequate diagnosis by Crickmay (1930a, p. 50), with the Neocomian Trigonia holubi Kitchin (1908) as type species. In a later reference to this genus, Crick- may (1932, p. 459) described its area as “*... broad, costellate in juvenile, smooth but for carinal tubercles in middle growth, irregular costellae in mature”’. After examining a plastotype of the South African 7rigonia holubi Kitchin, I confirm that it has a smooth proximal area except for tuberculate carinae (see also Camacho and Olivero, 1985, pl. 1, figs. 1-2).
Dietrich (1933) described the genus 7ransitrigonia, with the Neocomian South American Trigonia tran- sitoria Steinmann (1881, pl. 13, fig. 3) as type species. This species is characterized in juvenile specimens by an area with transverse costae or rugae that may reach the upper part of the posterior flank. Although some authors (Cox, 1952, 1969: Kobayashi and Amano, 1955; Levy, 1969: Poulton, 1979) considered Transi- trigonia Dietrich as a synonym of Steinmanella Crick- may, the present author, in coincidence with Saveliev (1958) and Camacho and Olivero (1985), believes that both taxa are valid based mostly on the different or- namentation of the area. In my opinion 77rigonia tran- sitoria Steinmann, the type species of Transitrigonia Dietrich, possesses the morphological patterns of the South American Steinmanellas. The genus Steinma- nella will be divided in this study into four different groups as follows: subgenus Steinmanella sensu stricto [S. (S.) holubi], subgenus Transitrigonia Dietrich [S. (T.) transitoria, S. (T.) quintucoensis, S. (T.) neuquen- sis, S. (T.) steinmanni, S. (T.) raimondii], subgenus Macrotrigonia Camacho and Olivero [S. (/.) vacaen- sis], and subgenus Splenditrigonia, n. subgen. [S. (Sp/.) splendida, S. (Spl.) erycina, S. (Spl.) haupti).
Subgenus TRANSITRIGONIA Dietrich, 1933
Type species.— Trigonia transitoria Steinmann, 1881, Neocomian, Caracoles, Chile.
Diagnosis.—Shell large, ovate to subquadrate. Flank ornamented by evenly spaced, tuberculate, concave costae. Area ornamented by transversely elongated tu- bercles in the proximal portion, and by transverse cos- tae or rugae in its mid- and distal part. These may well cross onto the upper part of the posterior flank. Mar- ginal and escutcheon carinae mostly defined in the um- bonal region by rows of tubercles, then indistinct. Es- cutcheon mostly ornamented with the same pattern as found on the area (Dietrich, 1933; Saveliev, 1958; Ca- macho and Olivero, 1985).
TRIGONUD BIVALVES OF ARGENTINA: LEANZA 41
Distribution.— Upper Jurassic (Middle Tithonian) to Lower Cretaceous (Barremian and ? Aptian), South America, southern North America.
Steinmanella (Transitrigonia) transitoria (Steinmann, 1881) Plate 10, figures 1, 2
Trigonia transitoria Steinmann, 1881, p. 260, pl. 13, figs. 3, 3a; 1882, p. 221, pl. 7, figs. 3, 4, pl. 8, figs. 1-3; Philippi, 1899, p. 63, pl. 29, figs. 5-7; Burckhardt, 1900a, p. 21, pl. 25, figs. 1-3; 1900b, p. 73, pl. 14, figs. 1, 2; Douvillé, 1910, p. 20, fig. 5; Lambert, p. 374, pl. 7, figs. 1, 2 (non pl. 6, fig. 1 = S. quintucoensis Weaver; non pl. 6, fig. 2 = S. vacaensis Weaver)
Steinmanella (Steinmanella) transitoria (Steinmann). Reyes and Peé- rez, 1978, p. 23, pl. 5, fig. 2
Steinmanella transitoria (Steinmann). Reyes, Serey and Pérez, 1981, pl. 2, fig. 16; Leanza and Garate, 1987, p. 214, pl. 9, fig. 2.
Steinmanella transitoria transitoria (Steinmann). Pérez, Reyes and Pérez, 1981, p. 105.
Description.—Shell large, oval, longer than wide. Umbones opisthogyrous, very anteriorly situated. Dorsal margin straight. Dorsoposterior angle obtuse. Posterior margin relatively short, curving evenly into the well rounded ventral margin, and then continu- ously to the convex anterior margin. Flank ornamented by concave costae, bearing medium sized, rounded and closely spaced tubercles. Antecarinal groove very poor- ly defined. Marginal carina poorly defined near umbo, and disappearing in the posterior part of the shell. Area ornamented by tubercles in the umbonal region, and then by transverse rugae which reach the upper part of the flank. Escutcheon with isolated and irregularly distributed tubercles.
Material.—One hypotype adult specimen, MOZ P0916, a complete shell, very well preserved (see also Leanza and Garate, 1987, pl. 9, fig. 2).
Measurements (in mm).—
Specimen No. L H W H/L W/L MOZ P0916 114 89 20 0.78 0.17
Remarks.— Although this species is very common in Hauterivian strata of the Agrio Formation at several localities of the Neuquén Basin, its first appearance was recorded in outcrops of the Upper Tithonian Vaca Muerta and Pictun Leuft Formations. For further com- parisons between this species and other species of Steinmanella from the Andean region see Reyes, Serey and Pérez (1981) and Pérez, Reyes and Pérez (1981).
Age and occurrence.—Late Valanginian/Early Hau- terivian, Olcostephanus curacoensis and Lyticoceras pseudoregale Zones, Agrio Formation; Cerro Pitrén (Locality 1), Dept. Norquin, Neuquén, Argentina. This species may range also in western central Argentina well into the Middle and Upper Hauterivian.
Steinmanella (Transitrigonia) quintucoensis (Weaver, 1931) Plate 14, figures 1-2, 4, 10
Trigonia transitoria var. quintucoensis Weaver, 1931, p. 248, pl. 21, fig. 111, pl. 23, figs. 119-125; Corvalan and Pérez, 1958, p. 40, pl. 3, figs. 2a, b
Trigonia transitoria Steinmann. Lambert, 1944, p. 374, pl. 6, fig. 1 (non pl. 6, fig. 2 = S. vacaensis (Weaver), non pl. 7, figs. 1-1 = S. transitoria (Steinmann)).
Steinmanella transitoria quintucoensis (Weaver). Saul, 1978, pl. 11, figs. 7, 8; Reyes, Serey and Pérez, 1981, pl. 1, fig. 4.
Steinmanella quintucoensis (Weaver). Leanza and Garate, 1987, p. 215, pl. 12, figs. 5, 6.
Description.—Shell large, ovate to subquadrate. Umbones opisthogyrous, very anteriorly situated. Dorsal margin straight. Dorsoposterior angle obtuse. Posterior margin relatively long. Ventroposterior angle rounded, curving into a broadly convex ventral mar- gin, and then continuously to the somewhat convex anterior margin. Flank ornamented by slightly concave and rather distant costae, which contain sparse, me- dium-sized, tubercles. Presence of a broad antecarinal sulcus which becomes wider toward the posterior part of the shell. Area asymmetrically divided by a median groove, ornamented by oblique rugae. Escutcheon with oblique growth lines and some scattered tubercles. Lig- amental fossette narrow, short, and deep.
Material.—Two topotype adult specimens. MOZ P0925, a complete shell, with both valves very well preserved, and MOZ P2552, a complete shell with Ly- cettia epizoans.
Measurements (in mm).—
Specimen No. 16; H WwW H/L W/L MOZ P0925 83 63 18 0.75 0.21 MOZ P2552 87 67 19 0.77 0.21
Remarks.—Leanza and Garate (1987, p. 215) ele- vated the original variety of Weaver (1931) to the rank of species on the basis of its easily recognizable shape in which the wide antecarinal sulcus is its outstanding feature. Stoyanow (1949, p. 69) has compared S. quin- tucoensis (Weaver) with “Trigonia” vyschetzkii Cragin (1905, pl. 8, fig. 2) from the Upper Jurassic (Kim- meridgian) Malone Formation of Texas, which was placed in Steinmanella by Saul (1978, p. 11), but the North American species differs in having: (1) a different shell shape; (2) a tuberculated marginal carina; and (3) less well developed antecarinal sulcus.
In the specimen MOZ P2552, which shows attach- ment of Lycettia epizoans, it is possible to recognize clearly an exhalant aperture in the upper part of the posterior margin, and also an inhalant aperture coun- terpart of greater size in the lower part of the posterior margin. These epizoans also allow reconstruction of
42 BULLETIN 343
living position and the depth of burrowing for this species. The living position of S. quintucoensis using the occurrence of epizoans coincides with the inter- pretation already made by Saul (1978, p. 19, fig. 8) for the North Pacific Cretaceous genus Yaadia Crickmay (1930a), and it is the subject of a further paper (Kauff- man, Leanza and Villamil, in press).
Age and occurrence.— Upper Berriasian/Lower Va- langinian, Spiticeras damesi and Neocomites wich- manni Zones, Vaca Muerta Formation; Cerrito de la Ventana, Trahuncura (Locality 4), Dept. Loncopué, Neuquén, Argentina.
Steinmanella (Transitrigonia) neuquensis (Burckhardt, 1903) Plate 12, figures 6, 7
Trigonia aff. nodosa Sowerby. Burckhardt, 1900a, p. 22, pl. 25, figs. ASS%
Trigonia neuquensis Burckhardt, 1903, p. 74, pl. 14, figs. 4-6; Weav- er, 1931, p. 254, pl. 22, figs. 112-114; Lambert, 1944, p. 383, pl. 9, fig. 5.
Steinmanella (Steinmanella) neuquensis (Burckhardt). Reyes and Pérez, 1978, p. 22, pl. 4, fig. 2.
Steinmanella neuquensis (Burckhardt). Cooper, 1979, p. 62, fig. 11; Pérez, Reyes and Pérez, 1981, p. 105; Reyes, Serey and Pérez,
1981, pl. 2, fig. 21; Leanza and Garate, 1987, p. 216, pl. 11, figs. 1 a)
Steinmanella (Transitrigonia) neuquensis (Burckhardt). Camacho and Olivero, 1985, pl. 2, fig. 1, pl. 4, fig. 2.
Description.—Shell large, rather inflated, subquad- rate. Umbones opisthogyrous, situated very anteriorly. Dorsal margin straight, with a slight expansion in its middle part. Dorsoposterior angle obtuse. Posterior margin relatively short. Ventroposterior angle also ob- tuse. Ventral margin gently convex, curving evenly into the convex anterior margin. Flank ornamented by reg- ularly concave, somewhat distant, tuberculated costae. Area exhibits transversely elongate tubercles in its proximal portion, and rugae arising the flank in its distal portion. Escutcheon as in other species of Stein- manella.
Material.—One hypotype adult specimen, MOZ P2767, a complete shell, with both valves very well preserved.
Measurements (in mm).—
Specimen No. IE; H WwW H/L W/L
MOZ P2767 81 66 21 0.81 0.25
Remarks.—Steinmanella neuquensis (Burckhardt) shows close affinities with S. transitoria (Steinmann) and S. steinmanni (Philippi), differing from these spe- cies by its subquadrate shape, straighter anterior mar- gin, with the umbones more anteriorly situated and shell more inflated.
Age and occurrence.—Upper Berriasian, Spiticeras damesi Zone, Vaca Muerta Formation; Cerrito de la Ventana, Trahuncura (Locality 4), Dept. Loncopué, Neuquen, Argentina. In the Neuquén Basin this species range in age from the Upper Berriasian to the Hau- terivian.
Steinmanella (Transitrigonia) steinmanni (Philippi, 1899) Plate 13, figures 1, 10
Trigonia steinmanni Philippi, 1899, p. 64, pl. 30, figs. 1, 2; Lambert, 1944, p. 378, pl. 9, figs. 1-4.
Trigonia transitoria var. curacoensis Weaver, 1931, p. 245, pl. 22, figs. 115-118.
Steinmanella (Steinmanella) transitoria (Steinmann) var. curacoen- sis Weaver. Reyes and Pérez, 1978, p. 25, pl. 3, fig. 4.
Steinmanella(Steinmanella) steinmanni (Philippi). Reyes and Pérez, 1978, p: 23, pl. 5, fig. 5.
Steinmanella steinmanni (Philippi). Pérez, Reyes and Pérez, 1981, p. 105; Reyes, Serey and Pérez, 1981, pl. 2, figs. 12-15; Leanza and Garate, 1987, p. 216, pl. 13, figs. 1, 2.
Steinmanella (Transitrigonia) steinmanni (Philippi). Camacho and Olivero, 1985, p. 49, pl. 1, figs. 3, 4.
Description.—Shell of medium size, oval, somewhat inflated. Umbones opisthogyrous, very anteriorly sit- uated, somewhat prominent. Dorsal margin straight. Dorsoposterior angle obtuse. Posterior margin rela- tively short. Ventroposterior angle obtuse. Ventral margin widely convex, curving evenly into the convex anterior margin. Flank ornamented by strongly con- cave costae exhibiting small tubercles which are par- tially united, this is a diagnostic character. Marginal carina partially developed in the proximal part of the shell and absent in the distal portion. Area contains in its distal portion, strong, crowded transverse rugae that cross the carinal line, reaching the upper part of the posterior flank. Escutcheon as in other species of Stein- manella.
Material.—One hypotype adult specimen. MOZ P0917, a complete shell, with both valves very well preserved (see Leanza and Garate, 1987, pl. 13, figs. 1-2).
Measurements (in mm).—
Specimen No. Iv H Ww H/L W/L MOZ P0917 91 63 2 0.69 0.24
Ne
Remarks.—This species is easily distinguishable from the other known species of Steinmanella by its oval shape, with anterior margin strongly convex, and es- pecially by its strongly concave costae of the flank which bear small and partially united tubercles. Lambert (1944, p. 379) demonstrated that the variety cura- coensis of Weaver (1931, p. 245, pl. 22, figs. 115-118) belongs to this species; this criterion was already adopt- ed by Leanza and Garate (1987, p. 216).
TRIGONUD BIVALVES OF ARGENTINA: LEANZA 43
Age and occurrence.— Valanginian, Olcostephanus curacoensis Zone, Mulichinco Formation; Puerta Cur- aco (Locality 2), Dept. Pehuenches, Neuquén, Argen- tina.
Steinmanella (Transitrigonia) raimondii (Lisson, 1930) Plate 11, figures 1-4
Trigonia Bronii Gabb (non Agassiz), 1877, p. 288.
Trigonia transitoria var. raimondii Lisson, 1930, p. 15, pl. 8, figs. ile
Steinmanella transitoria raimondii (Lisson). Pérez, Reyes and Perez, 1981, p. 105; Reyes, Serey and Pérez, 1981, pl. 1, figs. 19, 20. Steinmanella raimondii (Lisson), Leanza and Garate, 1987, p. 218,
pl. 11, figs. 8-13.
Description.—Shell small, subquadrate. Umbones opisthogyrous, very anteriorly located. Dorsal margin straight. Dorsoposterior angle obtuse. Posterior margin short. Ventroposterior angle widely obtuse. Ventral margin gently convex. Anteroventral angle present, widely obtuse. Anterior margin rather straight. Flank occupying two-thirds of the shell surface, ornamented by widely spaced, slightly concave, tuberculate costae. Antecarinal sulcus present widening toward the pos- terior part of the shell. Marginal and escutcheon ca- rinae very sharp, provided with tubercles. Area or- namented by transverse costae that do not reach the flank. Escutcheon elongate and narrow, crossed obliquely by rugose growth lines, with some irregular, unordered nodes.
Material.—Fourteen hypotypes, adult specimens unless otherwise indicated: MOZ P1756/1, whole shell, very well preserved; MOZ P1756/2, whole shell, but with the posterior part broken; MOZ P1756/3, whole shell, well preserved; MOZ P1756/4, whole shell, but with the left valve broken; MOZ P1756/5, whole shell, well preserved; MOZ P1756/6, whole shell, poorly pre- served; P 1756/7, with both valves, but somewhat bro- ken; MOZ P1756/8, whole shell, well preserved; MOZ P1756/9-11, whole shell, but poorly preserved; P 1756/ 12, a right valve poorly preserved; P 1756/13, a right valve of a juvenile specimen; MOZ P1756/14, a well preserved left valve. All specimens are preserved in a light green siltstone.
Measurements (in mm).—
Specimen No. iG H WwW H/L W/L MOZ P1756/3 29 24 8.5 0.82 0.29 MOZ P1756/9 36 28 9 0.77 0.25
Remarks.—Steinmanella raimondii (Lisson) was cited for the first time in Argentina by Leanza and Garate (1987, p. 218). It clearly differs from the other known species of Steinmanella by its small size, shell shape, and characteristic marginal and escutcheon ca- rinae.
Age and occurrence.—Lower and Middle Hauteri- vian, Lyticoceras pseudoregale and Holcoptychites neu- quensis Zones, Agrio Formation; Cerro Mesa, Covun- co (Locality 8), Dept. Zapala, Neuquén, Argentina.
Subgenus SPLENDITRIGONIA, new subgenus
Type species.—Trigonia splendida A. F. Leanza, 1941, Upper Jurassic (Tithonian), Neuquen, Argenti- na.
Diagnosis.—Shell large, subquadrate to subrectan- gular. Flank ornamented by nearly straight, tuberculate costae, arranged in narrow or wide bundles. Area wide, strongly tuberculated or with lines of beads. Marginal carina tuberculated in the umbonal region, or distinctly demarcated by different ornamentation of flank and area. Escutcheon wide, irregularly tuberculated.
Distribution.— Upper Jurassic (Tithonian) to Lower Cretaceous (Lower Valanginian). Argentina and Chile.
Discussion.— Kobayashi and Amano (1955) were the first to include Trigonia erycina Philippi and Trigonia haupti Lambert in the genus Steinmanella Crickmay (1930a). This view was later accepted by Levy (1969), who also added Trigonia splendida A. F. Leanza to this group. Reyes et al. (1981) noted the strong affinities of Steinmanella haupti with Steinmanella erycina, grouping these two species in their subgroup B1. Pérez, Reyes and Pérez (1981) considered S. splendida and S. haupti as Steinmanella characterized by tuberculate areas. Camacho and Olivero (1985, p. 51), in their revision of the genus Steinmanella, stated that the group of trigoniids composed of S. splendida, S. erycina and S. haupti might constitute a different lineage or even a separate genus related to Steinmanella. In agreement with this view, and based on newly collected material from western central Argentina, the subgenus Splen- ditrigonia, n. subgen. is proposed herein, with T. splen- dida A. F. Leanza as type species. The new subgenus constitutes an homogeneous stock composed by S. (Spl.) splendida, S. (Spl.) haupti and S. (Spl.) erycina, the first two species characterized by strong tubercu- lation on the area, and the third species being closely linked with S. (Sp/.) haupti in shell shape and flank ornamentation, and with the area ornamented by lines of beads.
Steinmanella (Splenditrigonia) splendida (A. F. Leanza, 1941) Plate 11, figures 5-8
Trigonia splendida A. F. Leanza, 1941, p. 225, pl. 1, figs. 1, 2.
? Trigonia cf. splendida A. F. Leanza. Corvalan, 1959, p. 33, pl. 2, fig. 6.
Steinmanella (Steinmanella) splendida (A. F. Leanza). Reyes and Pérez, 1978, p. 22, pl. 5, fig. 3.
Steinmanella splendida (A. F. Leanza). Pérez, Reyes and Perez, 1981, p. 105; Reyes, Serey and Pérez, 1981, pl. 1, fig. 23; Leanza and Garate, 1987, p. 217, pl. 13, fig. 7.
44 BULLETIN 343
Description.—Shell large, subquadrate. Umbones opisthogyrous, very anteriorly situated. Dorsal margin straight. Dorsoposterior angle obtuse, rounded. Pos- terior margin short. Ventroposterior angle very round- ed. Ventral margin gently convex, curving evenly into the straight anterior margin. Flank ornamented ini- tially by straight costae and subsequently by slightly concave costae, bearing irregularly sized tubercles. Area completely ornamented by oblique lines of irregularly sized tubercles. Marginal carina tuberculate. Antecar- inal groove absent. Escutcheon ornamented, as the area, also by irregular tubercles. Exhalant aperture well de- veloped.
Material.—One hypotype adult specimen, MOZ P2553, a whole shell, with both valves very well pre- served, bearing Lycettia sp. epizoans.
Measurements (in mm).—
Specimen No. L H W H/L W/L MOZ P2553 91 77 20 0.84 0.22
Remarks.—Steinmanella (Splenditrigonia) splendi- da differs from other species of the subgenus Jransi- trigonia by its characteristic tuberculate area and es- cutcheon, and also by its subquadrate shape. This species closely resembles the Neocomian Mediterra- neotrigonia Nakano (1974) (type species: Trigonia hondeana Lea, 1841) from the Barremian/Aptian of Pert, Colombia and Venezuela, and it might be con- sidered its direct ancestor in the Andean region. Orig- inally S. (Sp/.) splendida was found in Lower Tithonian beds of Carrin Cura (see A. F. Leanza, 1941), but sub- sequently the authors found the same species in the Upper Tithonian (Substeuroceras koeneni Zone) of Mallin Quemado, and in the Lower Valanginian (Neo- comites wichmanni Zone) from Cerrito de la Ventana, Trahuncura area (Leanza and Garate, 1987). One of the specimens illustrated here (Pl. 11, fig.7) shows the well-developed exhalent aperture particularly well.
Age and Occurrence.—Early Valanginian, Neocom- ites wichmanni Zone, Vaca Muerta Formation; Cerrito de la Ventana, Trahuncura (Locality 4), Dept. Lon- copué, Neuquén, Argentina. In the Neuquén Basin this species is known from strata of Lower Tithonian to Early Valanginian age.
Steinmanella (Splenditrigonia) erycina (Philippi, 1899) Plate 7, figure |
Trigonia erycina Philippi, 1899, p. 66, pl. 30, figs. 3-5; Lambert, 1944, p. 379, pl. 8, fig. 4.
Steinmanella erycina erycina (Philippi)). Pérez, Reyes and Pérez, 1981, p. 105.
Steinmanella erycina (Philippi). Reyes, Serey and Pérez, 1981, pl. 2, figs. 3-8 [non figs. 4, 8 = S. haupti (Lambert)]; Leanza and Garate, 1987, p. 217, pl. 13, fig. 6.
Steinmanella (S.) erycina (Philippi). Pérez and Reyes, 1989, p. 10, pl. 1, figs. 5, 10.
Description.—Shell large, subrectangular. Umbones opisthogyrous, very anteriorly situated. Dorsal margin straight and long. Dorsoposterior angle obtuse. Pos- terior margin relatively long. Ventroposterior angle ob- tuse, very rounded. Ventral margin straight, curving abruptly into the straight anterior margin. Flank oc- cupying four-fifths of the shell surface, ornamented with straight costae in its ventral portion, curving abruptly near the marginal carina; the costae bear closely spaced medium size tubercles. Marginal carina absent, only demarcated by the distinct ornamentation of flank and area. Area narrow, showing rows of finely beaded transverse costae. Escutcheon with elongated tubercles forming oblique lines toward the escutcheon carina. Ligamental fossette elongate. Shell rather thick.
Material.—One adult hypotype specimen, MOZ P0921, an incomplete left valve with its posterior part broken.
Measurements (in mm).—
Specimen No. IL H WwW H/L W/L MOZ P0921 80 69 24 0.86 0.30
Remarks.—Although Steinmanella (Splenditrigo- nia) erycina (Philippi) has weakly defined costae on the area, they bear small tubercles which clearly relate this species with Steinmanella (S.) splendida (A. F. Leanza) and Steinmanella (Spl.) haupti (Lambert); these species form an homogeneous stock. S. (Sp/.) erycina differs from S. (Sp/.) splendida in its subrectangular instead of subquadrangular shape, and in having small- er tubercles in the area. S. (Sp/.) haupti (Lambert), as it was stated by Lambert (1944) differs from S. (Sp/.) erycina in having lines of small tubercles over the whole area.
Age and occurrence.—Upper Tithonian, Corongo- ceras alternans Zone, Picin Leufi' Formation; Cai- chigiie, Charahuilla (Locality 22), Dept. Catan Lil, Ne- uqueén, Argentina.
Steinmanella (Splenditrigonia) haupti (Lambert, 1944) Plate 6, figures 1-2
Trigonia erycina Haupt (non Philippi), 1907, p. 215, pl. 8, figs. Sa, b.
Trigonia erycina Weaver (non Philippi), 1931, p. 259, pl. 21, figs. 109, 110.
Trigonia haupti Lambert, 1944, p. 381, pl. 5, figs. 7, 8; A. F. Leanza and Castellaro, 1955, p. 188, pl. 1, fig. 18.
Steinmanella (Steinmanella) haupti (Lambert). Reyes and Pérez, 1978, p. 21, pl. 5, fig. 4.
Steinmanella erycina haupti (Lambert). Pérez, Reyes and Pérez, 1981, p. 105.
Steinmanella haupti (Lambert). Reyes, Serey and Pérez, 1981, pl. 2, figs. 1, 2; Leanza and Garate, 1987, p. 218, pl. 12, figs. 1, 2.
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 45
Description.—Shell large, subrectangular. Umbones opisthogyrous, very anteriorly situated. Shape of the shell and ornamentation of the flanks very similar to Steinmanella (Spl.) erycina (Philippi), but the area is characterized throughout its whole development by lines of very small tubercles.
Material.—One adult hypotype specimen, MOZ P0913, a complete shell, with both valves very well preserved.
Measurements (in mm).—
Specimen No. IU, H WwW H/L W/L MOZ P0913 90 64 20 0.71 0.22
Remarks.—The differences between Steinmanella (Spl.) haupti (Lambert) with S. (Sp/.) splendida (A. F. Leanza) and S. (Sp/.) erycina (Philippi) have been treat- ed in the descriptions of those species.
Age and occurrence.—Upper Tithonian, Corongo- ceras alternans Zone, Pican Leuf Formation; Aguada del Overo (Locality 19), Dept. Catan Lil, Neuquén, Argentina. Although Lambert (1944) ascribed Stein- manella (Splenditrigonia) haupti to the Valanginian, later studies by H. Leanza (1973, 1981) have revealed that this species only extends from the Middle Ti- thonian to the Lower Berriasian (see Leanza and Gar- ate, 1987).
Subgenus MACROTRIGONIA Camacho and Olivero, 1985
Type species.—Steinmanella (Macrotrigonia) kat- terfeldensis Camacho and Olivero, Hauterivian/Bar- remian, Chubut, Argentina.
Diagnosis.—Shell very large, elongated, with acu- minate ventroposterior angle. Anterior margin of the shell subplanate. Flank ornamented by almost straight or only gently tuberculated costae. Area tuberculated, transversely ridged by prominent rugae on its distal portion. Escutcheon wide, ornamented as on the area (Camacho and Olivero, 1985).
Distribution.—Lower Cretaceous (Valanginian to Barremian). Argentina, Chile and South Africa.
Steinmanella (Macrotrigonia) vacaensis (Weaver, 1931) Plate 15, figures 6-7; Plate 16, figure 13
Trigonia transitoria var. vacaensis Weaver, 1931, p. 251, pl. 24, figs. 126-130; Lambert, 1944, p. 377, pl. 7, fig. 3, pl. 8, figs. 1-3.
Trigonia transitoria Steinmann. Lambert, 1944, p. 374, pl. 6, fig. 2 (non pl. 6, fig. 1 = S. quintucoensis (Weaver), non pl. 7, figs. 1, 2 = S. transitoria (Steinmann).
Steinmanella (Steinmanella) transitoria (Steinmann) var. vacaensis Weaver. Reyes and Pérez, 1978, p. 26, pl. 4, fig. 4.
Steinmanella transitoria vacaensis Weaver. Reyes, Serey and Pérez, 1981, pl. 1, figs. 14-18; Pérez, Reyes and Perez, 1981, p. 105.
Steinmanella (Macrotrigonia) vacaensis (Weaver). Camacho and Olivero, 1985, p. 59, pl. 3, figs. 3, 4.
Steinmanella vacaensis (Weaver). Leanza and Garate, 1987, p. 215, pl. 10, figs. 1-3.
Description.—Shell very large, strongly elongated and posteriorly acuminate. Umbones opisthogyrous, very anteriorly situated. Dorsal margin straight. Dorsopos- terior angle very obtuse. Posterior margin very long. Ventroposterior angle slightly acute, resulting in an acuminate end of the shell. Ventral margin slightly convex. Anteroventral angle nearly 90°. Anterior mar- gin straight, giving the anterior part of the shell a sub- planate aspect. Flank ornamented by strongly tuber- culated, almost straight or only gently curved costae. Area and escutcheon ornamented as in other species of Steinmanella.
Material.—One hypotype adult specimen, MOZ P2329, a whole shell, with both valves very well pre- served.
Measurements (in mm).—
Specimen No. 1 H W H/L W/L MOZ P2329 164 86 26 0.52 ONS
Remarks.—Steinmanella (M.) vacaensis (Weaver) can readily be distinguished from the other known species of Steinmanella by its very large size, with almost straight anterior margin and an acuminate end of the shell. In this species the exhalant and inhalant apertures are well developed (see Pl. 15, fig. 6). Dif- ferences with other representatives of the subgenus Macrotrigonia [S. (M.) posadensis Camacho and Oliv- ero (1985, p. 55, pl. 4, figs. 1,3); S. (7.) maxima Ca- macho and Olivero (1985, p. 58, pl. 1, fig. 5; pl. 3, fig. 1); .S. (M.) katterfeldensis Camacho and Olivero (1985, pl. 2, figs. 3-4)] from the Hauterivian/Barremian of Chubut, Argentina, and with S. (M.) herzogi (Goldfuss) from the Valanginian of South Africa, are principally based on shell shape and the curvature of the flank costae.
Age and occurrence.— Middle Hauterivian, Holcop- tychites neuquensis Zone, Agrio Formation; Los Hor- nos, Covunco Creek (Locality 29), Dept. Zapala, Ne- uquén, Argentina. In the Neuquén Basin this species is also very common in the Upper Hauterivian.
Subfamily ANDITRIGONIINAE, new subfamily
Diagnosis.—Shell small to large in size, mostly pyr- iform, but also subquadrate to elongate. Flank orna- mented by two sets of costae meeting on different parts of the flank forming L-, V- or W-shaped patterns or a combination of these in which tuberculate costae or isolated tubercles may be present. Area practically smooth in early representatives (Eoanditrigonia), later ornamented by transverse costellae near umbo and a smooth distal area (Anditrigonia), faint radial costellae
46 BULLETIN 343
on the area (Paranditrigonia), transverse costellae on the whole surface (Antutrigonia), or transverse costel- lae near umbo and then radial costellae on the distal area (Virgotrigonia). Marginal carina may be absent (Antutrigonia), only defined in the umbonal region (Eoanditrigonia, Anditrigonia, Paranditrigonia) or continuous along the whole length of the shell (Lam- bertrigonia, Virgotrigonia). Escutcheon usually wide and smooth, and not very well impressed.
Distribution.—Early Jurassic (Early Bajocian) to Lower Cretaceous (Hauterivian). North America (Can- ada, United States, México) and South America (Ar- gentina, Chile, Peru).
Discussion.—Nakano (1965) revised Megatrigoni- inae van Hoepen (1929), and defined the subfamily as follows:
Shell large to small in size, triangularly ovate to pyr- iform, inequilateral, moderately inflated; umbo large, opisthogyrous and located anteriorly; marginal and escutcheon carinae evanescent except near umbo; area narrow, curved, with an upward-facing concav- ity; median carina or groove indistinct; escutcheon narrow and depressed: on flank several early costae concentric or subconcentric; but most others are di- agonal, V- or L-shaped and sometimes effaced later; costellae on area and escutcheon first transverse but die out later. Internally, a lengthy radial ridge con- icides approximately with the middle of the area; test rather thick (Nakano, 1965, p. 14).
When Nakano (op. cit.) revised the Megatrigoniinae, however, the genus Anditrigonia Levy (1967c) (type species: Trigonia carrincurensis A. F. Leanza, 1941) had not yet been erected. In recent years the knowledge of this taxon has significatively improved thanks to the studies of Reyes and Pérez (1982) and Pérez and Reyes (1983, 1989). These authors (Reyes and Pérez, 1983) erected the subgenus Paranditrigonia to differentiate forms of Anditrigonia with radial costellae on the area. Leanza and Garate (1987) created the genus Antutri- gonia to identify species closely related and formerly included in Anditrigonia, but in which the area is char- acterized by transverse costellae throughout its entire development. Alleman (Nov. 1985) erected the genus Virgotrigonia (=Maputrigonia Leanza, Dec. 1985) with flank ornamentation similar to Anditrigonia, but with the area characterized by transverse costellae near the umbo, and by radial costellae on the remaining surface. In the present study the subgenus Eoanditrigonia, n. subgen. and the genus Lambertrigonia, n. gen. are pro- posed. The first taxon includes Middle Jurassic forms with a smooth area and flank pattern opposite to that of Anditrigonia; the second taxon includes forms very closely related to Paranditrigonia, on the basis of radial costation on the area, but with a well developed mar-
ginal carina and a protruding submedian groove on the area.
These new and numerous very closely related taxa confirm that the subfamily comprises a phyletically homogeneous stock. Several taxa have superimposed ornamentational patterns on the area which were not adopted in the differential diagnosis of the Megatri- goniinae by Nakano (1965), especially the nature of the marginal and escutcheon carinae, and the orna- mentation of the area. Therefore the relationships of this North and South American group of Trigoniidae with Megatrigoniinae appear to be only superficial, and the subfamily Anditrigoniinae, n. subfam. is proposed herein. Anditrigoniinae, n. subfam., includes the fol- lowing taxa: Eoanditrigonia, Lambertrigonia, Paran- ditrigonia, Anditrigonia, Virgotrigonia and Antutrigo- nia. The Megatrigoniinae are considered to include, in agreement with Nakano (1965, p. 20), the genera Me- gatrigonia van Hoepen and Jotrigonia van Hoepen.
Genus ANDITRIGONIA Levy, 1967c
Type species.—Trigonia (Megatrigonia) carrincu- rensis A. F. Leanza, 1941, Upper Jurassic (Middle Ti- thonian), Neuquén, Argentina.
Diagnosis.—Shell usually large, ovate, subtrigonal or pyriform. Flank ornamented by subconcentric costae, followed by a two sets of costae, the anterior one sub- horizontal or sinuous, and the posterior subvertical or oblique. The junction of these two sets of costae can be simple, sinuous, in L-shape, or in more complex V- or W- shape. In the mid-anterior flank tubercles may be present. Area narrow, with faint transverse or con- centric costellae near umbo, then smooth, with or with- out submedian groove. Marginal and escutcheon ca- rinae poorly defined. Escutcheon elongated, narrow, excavated and smooth, or ornamented by oblique growth lines (Levy, 1967c; Reyes and Pérez, 1982; Leanza and Garate, 1987).
Distribution.—Early Jurassic (Early Bajocian) to Lower Cretaceous (Hauterivian). North America (Can- ada, United States, México) and South America (Ar- gentina, Chile, Peru).
Subgenus EOANDITRIGIONIA, new subgenus
Type species.— Trigonia keideli Weaver, 1931, Mid- dle Jurassic (Middle Bajocian/Early Callovian), Neu- quén, Argentina.
Diagnosis.—Shell medium to large in size, pyriform. Umbones prominent, very anteriorly located. Anterior flank ornamented by up to 40, very narrow, subcon- centric costae that form on the posterior flank a ven- trally directed V- or L-shaped inflection with a pos- terior set of costae. But these are fewer, thicker, and in inverse relation to those of Anditrigonia sensu stric- to. Area narrow and smooth, with submedian groove.
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 47
Marginal carina only defined in the umbonal region. Escutcheon narrow and smooth.
Distribution.— Middle Jurassic (Middle Bajocian to Early Callovian). Argentina and Chile.
Discussion.—The type species of Eoanditrigonia, n. subgen., Trigonia keideli Weaver, has been discussed in detail by Leanza and Garate (1983, p. 98; 1987, p. 220), who demonstrated the affinities to Anditrigonia Levy, as well as the synonymy of 7. keideli and Tri- gonia chacaicoensis Lambert. In accordance with the grade of refinement of the taxonomy proposed in this monograph, there is a strong argument for the sepa- ration of this form as an independent subgenus of An- ditrigonia. It is based principally on the presence of a totally smooth area which is not present in Levy’s ge- nus, and an exactly inverse costation on the flank with regard to Anditrigonia: the anterior part is crowded with narrow subconcentric costae, whilst the posterior set includes thick and fewer costae.
Eoanditrigonia, n. subgen. shows affinities with An- divaugonia, n. gen. (this paper), but this genus is a member of Vaugoniinae, showing the two set of costae meeting in a narrow V-shaped inflection of vaugonic style; the area is wider, and usually ornamented by transverse rugae or growth lines, whereas the marginal carina is somewhat better defined than in Eoanditri- gonia, n. subgen.
Anditrigonia (Eoanditrigonia) keideli (Weaver, 1931) Plate 2, figures 16, 18
Trigonia literata Y oung and Bird var. keideli Weaver, 1931,p. 367, pl. 20, fig. 102.
Trigonia chacaicoensis Lambert, 1944, p. 367, pl. 2, figs. 1-5.
Totrigonia chacaicoensis (Lambert). Kobayashi and Mori, 1955, p. 75.
Megatrigonia chacaicoensis (Lambert). Nakano, 1965, p. 17.
Anditrigonia chacaicoensis (Lambert). Levy, 1967c, p. 137; Reyes and Pérez, 1982, p. A291.
Anditrigonia keideli (Weaver). Leanza and Garate, 1983a, p. 98, pl. 1, figs. 1, 2, pl. 2, figs. 1-3; Leanza and Garate, 1987, p. 220, pl. 2, figs. S—5S, pl. 3, figs. 6, 7.
Description.—Shell medium to large in size, pyri- form. Umbones highly opisthogyrous, very anteriorly situated. Dorsal margin strongly convex. Dorsopos- terior angle obtuse. Posterior margin short. Ventro- posterior angle almost 90°. Ventral margin sinuous in coincidence with the antecarinal region, subsequently slightly convex, curving evenly into the convex ante- rior margin. Flank occupying fourth-fifths of the shell surface, with a highly variable ornamentation char- acterized by 25 to 40 faint, subconcentric costae that form in the posterior part of the flank a ventrally di- rected V- or L-shaped inflection with another set of costae, but these being fewer and thicker. Area nearly smooth, ornamented only by very faint, transverse
growth lines. A shallow submedian groove divides the area into two asymmetrical parts. Marginal carina only poorly defined in the proximal part of the shell, and absent in the distal portion. Escutcheon narrow and smooth.
Material.— Four topotype specimens: MOZ P0902/ 3, an adult left valve; MOZ P2748, an adult left valve: MOZ P2749/1, a juvenile left valve; MOZ P1749/2, ajuvenile right valve. All specimens are well preserved in a fine-grained, reddish-brown sandstone.
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P2748 =28 20 5 0.71 0.17 MOZ P2749/2 24 19 8 0.55 0.33 MOZ P2749/1 19 12 7 0.63 0.36 MOZ P0902/3 53 38 9 0.71 0.16
Remarks.—Anditrigonia (Eoanditrigonia) keideli (Weaver) has been extensively discussed by Leanza and Garate (1983a), and it constitutes the oldest represen- tative of the genus Anditrigonia Levy as it has been recorded in Middle Jurassic (Middle Bajocian, Early Callovian) Lajas Formation from Neuquén, and equiv- alent strata in Chile. Anditrigonia plumasensis (Hyatt) (in Poulton, 1979, p. 43, pl. 11, figs. 6-7) from the Callovian Hinchman Formation of Mount Jura, Cal- ifornia, U.S.A., and the Lower Oxfordian Hazelton and Bowser Lake Groups, British Columbia, Canada, is another Middle and Upper Jurassic representative of the genus in the Northern Hemisphere. It 1s worth noting that some specimens (Leanza and Garate, 1987, pl. 3, figs. 6-7) show on the flank costae similarities to A, (A.) eximia, although this Upper Jurassic and Lower Cretaceous species show an inverse relation 1n the cos- tation of the flank: the posterior set of costae are more numerous and narrower than in A. (E£.) keideli (Weav- er)!
Age and occurrence.—Early Bajocian to Early Bath- onian, Emileia giebeli to Cadomites—Tulitidae Zones, Lajas Formation; Los Pozones (Locality 15), Dept. Za- pala, Neuquén, Argentina.
Subgenus ANDITRIGONIA Levy, 1967c
Anditrigonia (Anditrigonia) carrincurensis (A. F. Leanza, 1941) Plate 5, figures 8, 9
Trigonia (Megatrigonia) carrincurensis A. F. Leanza, 1941, p. 229, pli25 figs: liv.
? Trigonia cf. carrincurensis A. F. Leanza. Lambert, 1944, p. 390, pl. 5, fig. 6.
Anditrigonia carrincurensis (A. F. Leanza). Levy, 1967c, p. 137; Reyes and Pérez, 1978, p. 16, pl. 2, fig. 1; Reyes and Perez, 1982, p. A298; Leanza and Garate, 1987, p. 221, pl. 7, figs. 1, 2.
Description.—Shell of medium to large size, sub- ovate, longer than high. Umbones opisthogyrous, sit-
48 BULLETIN 343
uated in the anterior one-third of the shell. Dorsal margin strongly convex. Dorsoposterior angle obtuse. Posterior margin relatively short. Ventroposterior an- gle a right to obtuse angle. Ventral margin slightly con- vex, curving abruptly into the slightly convex anterior margin. Flank somewhat proximally inflated, and dis- tally flattened, ornamented by two sets of well defined costae; anterior set subconcentric; posterior set radial retroverse, both meeting in undulations forming irreg- ular V- or W-shaped inflection on which some scat- tered tubercles may be present. Area narrow, asym- metrically divided by a shallow submedian groove, ornamented near the umbones by faint transverse cos- tellae, subsequently smooth. Marginal carina poorly defined, only present in juvenile stages of growth. Es- cutcheon smooth, elongate and excavated. Material.—One adult hypotype specimen, MOZ P0923/1, a complete shell, with both valves relatively well preserved (Leanza and Garate, 1987, pl. 7, fig. 1). Measurements (in mm).—
Specimen No. L H W H/L W/L MOZ P0923/1 68 54 15 0.79 0.22
Remarks.—The holotype of Anditrigonia (A.) car- rincurensis was found at Carrin Cura in the southern- most Tithonian outcrops of the Neuquén Basin (A. F. Leanza, 1941). According to the ammonite biochro- nology proposed by Leanza and Hugo (1977), the ho- lotype of A. (4.) carrincurensis can be regarded as mid- Middle Tithonian (Aulacosphinctes proximus Zone) in age, and stratigraphically belongs to the Carrin Cura Formation (Leanza, Marchese and Riggi, 1977). This species is also very common in fine-grained green sand- stones of the distal tongues of the Carrin Cura For- mation in the Cerro Caichigiie and Fortin 1° de Mayo areas.
Age and occurrence.— Middle Tithonian, Windhau- seniceras internispinosum Zone, Picun Leufu Forma- tion; Canadon del Sapo (Locality 20), Dept. Catan Lil, Neuqueén, Argentina.
Anditrigonia (Anditrigonia) eximia (Philippi, 1899) Plate 9, figures 3, 4
Trigonia eximia Philippi, 1899, p. 76, pl. 34, figs. 3, 3a, 3b; Gillet, 1924, p 92; Lambert, 1944, p. 391, pl. 10, figs. 1, 2, pl. 11, figs. 1, 2, pl. 12, figs. 1, 2, pl. 13, fig. 1 (non pl. 10, figs. 3-5 = Andi- trigonia lamberti Levy).
Trigonia eximia var. B. Philippi, 1899. p. 76.
Trigonia crassidens Philippi, 1899, p. 73, pl. 33, fig. 1.
Trigonia arnisoe Philippi, 1899, p. 76, pl. 34, fig. 2.
Trigonia macrorrhyncha Philippi, 1899, p. 77, pl. 34, fig. 5.
Trigonia pusilla Philippi, 1899, p. 78, pl. 34, fig. 7.
Trigonia consanguinea Philippi, 1899, p. 79, pl. 34, fig. 9.
Trigonia gampsorrhyncha Philippi, 1899, p. 79, pl. 34, fig. 10.
Trigonia angusta Philippi, 1899, p. 79, pl. 35, figs. 1, 2.
Trigonia foveata Philippi, 1899, p. 80, pl. 35, fig. 3.
Trigonia semicostata Philippi, 1899, p. 82, pl. 35, fig. 7.
Trigonia aff. conocardiiformis Krauss. Burckhardt, 1903, p. 72, pl. 13 Sfigswle2
Trigonia cf. eximia (Philippi). Haupt, 1907, p. 216.
Trigonia picunensis Weaver, 1931, p. 261, pl. 25, figs. 131-136, pl. 27, fig. 150.
Megatrigonia eximia (Philippi). Nakano, 1965, p. 17.
Anditrigonia eximia (Philippi). Levy, 1967c, p. 137; Reyes and Perez,
1978, p. 17, pl. 1, fig. 8; Perez and Reyes, 1982, p. A294; Leanza and Garate, 1987, p. 221, pl. 9, fig. 1; Pérez and Reyes, 1989, p. 14, pl. 2, figs. 7, 11, 14, 15.
Anditrigonia picunensis Weaver, Levy, 1967c, p. 138.
Description.—Shell large, pyriform, anteriorly in- flated. Umbones opisthogyrous, situated in the ante- rior one-third of the shell. Dorsal margin convex. Dor- soposterior angle obtuse. Posterior margin short. Ventroposterior angle almost 90°. Ventral margin slightly convex, curving evenly into the strongly con- vex anterior margin. Flank occupying five-sixths of the shell surface, ornamented by a highly variable costa- tion, consisting in two sets of costae, the anterior and the posterior. These meet in patterns of diverse com- plexity from V, W, or zig-zag shape. The more distal costae are isolated and vertical. Area very narrow, or- namented with faint transverse costellae barely devel- oped near the umbonal region, subsequently disap- pearing. Submedian groove divides area into two asymmetrical parts. Marginal and escutcheon carinae only distinguishable near the umbones, disappearing in the distal portion. Escutcheon narrow, lanceolate, smooth, except near the umbo where diagonal growth lines or faint costellae occur on very well preserved specimens.
Material.—Two adult hypotype specimens, MOZ P1902/1, a left valve with a Ptychomya sp. epizoan and MOZ P1902/2, a complete shell, with the two valves relatively well-preserved.
Measurements (in mm).—
Specimen No. IG H Ww H/L W/L MOZ P1902/1 98 63 24 0.64 0.24 MOZ P1902/2 64 41 13 0.64 0.20
Remarks.—Anditrigonia (A.) eximia (Philippi) is one of the more common and highly variable species from the Andean region, and was considered to be an ab- errant form of the taxon Scabrae Agassiz (1840) by Gillet (1924, p. 92). As evidenced by the large syn- onymy, this species has received much attention from paleontologists. Lambert (1944, p. 391, pl. 10, figs. 1- 5; pl. 11, figs. 1-2; pl. 12, figs. 1-2; pl. 13, fig. 1) dem- onstrated the great variability of this species in which it is hard to find one specimen similar to another even
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 49
in a same bed or community. In recent years Reyes and Pérez (1982) and Pérez and Reyes (1983, 1989) have made substantial progress in the knowledge of this species. They distinguished the subgenus Paran- ditrigonia Reyes and Pérez 1983 (type species: Andi- trigonia (Paranditrigonia) potrerillensis Reyes and Peé- rez, 1983, p. 62, pl. 1, figs. 4, 7 and 9) to identify forms with only radial ornamentation on the area; these are barely distinguishable when this portion of the shell is not well preserved inasmuch all other features remain the same.
Age and occurrence.—Upper Tithonian, Corongo- ceras alternans and Substeueroceras koeneni Zones, Picun Leuf’ Formation; Aguada del Overo (Locality 19), Dept. Catan Lil, Neuquén, Argentina.
Anditrigonia (Anditrigonia) lamberti Levy, 1967c Plate 9, figure 7
Trigonia eximia Philippi. Lambert, 1944, p. 391, pl. 10, figs. 3-5 (non 7. eximia Philippi, 1899).
Anditrigonia lamberti Levy, 1967c, p. 139, pl. 1, figs. 2a-c, text-fig. on p. 139; Leanza and Garate, 1987, p. 222, pl. 7, fig. 3.
Description.—Shell small, pyriform, anteriorly in- flated. Dorsal margin slightly convex. Dorsoposterior angle obtuse. Posterior margin very short. Ventropos- terior angle nearly 90°. Ventral margin slightly convex, curving evenly into the strongly convex anterior mar- gin. Flank ornamented by two sets of costae: the an- terior one with subconcentric, widely spaced costae meeting the posterior set in a L-shaped junction. Area narrow and smooth, except in the portion near the umbo where some faint transverse costellae are pres- ent. Marginal and escutcheon carinae undefined. Es- cutcheon smooth.
Material.—One complete hypotype adult specimen, MOZ P0914, complete, very well-preserved with the valves in butterfly position (Leanza and Garate, 1987, pl. 7, fig. 3).
Measurements (in mm).—
Specimen No. L H WwW H/L W/L MOZ P0914 46 22 - 0.48 -
Remarks.—It is possible that the specimen figured as Trigonia eximia var. multicostata by Corvalan (1959, pl. 1, fig. 1) from the Chilean Tithonian, also illustrated and considered by Pérez and Reyes (1983, pl. 4, fig. 13) as Anditrigonia discors (Philippi), belongs to An- ditrigonia (A.) lamberti Levy.
Age and occurrence.— Middle Tithonian, Windhau- seniceras internispinosum Zone, Pican Leufi: Forma- tion; Los Catutos (Locality 12), Dept. Zapala, Neu- quén, Argentina.
Anditrigonia (Anditrigonia), species indeterminate Plate 16, figures 5, 8
Description.—Shell of medium size, pyriform, lon- ger than high. Umbones orthogyrous, situated in the anterior one-third of the shell. Posterior dorsal margin slightly concave; anterior dorsal margin slightly con- vex. Posterior portion of the shell not preserved. Ven- tral margin slightly convex, curving evenly into the strongly convex anterior margin. Flank very wide, oc- cupying five-sixths of the shell surface, ornamented by two sets of costae. The anterior set is widely spaced, raised and subconcentric, meeting the anterior margin at right angles. The posterior flank set of costae meet the posterior set in L- or V- shaped junctions. These costae trend subvertically: their intercostal spaces are narrower than the costae. Both area and escutcheon comprise a narrow and somewhat concave surface, but the preservation of the specimen precludes any obser- vation on the nature of the ornamentation in these regions.
Material.—One adult specimen, MOZ P5236, a complete shell with both flanks well preserved, but with area and escutcheon not observable, and the pos- terior part of the shell broken.
Measurements (in mm).—
Specimen No. I H WwW H/L W/L MOZ P5236 =58 34 14 0.58 0.24
Remarks.—The extremely convex anterior margin differentiates this species from Anditrigonia (A.) exi- mia (Philippi), and Anditrigonia (A.) discors (Philippi). As these taxa are highly variable (see Lambert, 1944, Pérez and Reyes, 1983), however, and considering the shortage of material (only one specimen) 1n which the area and escutcheon are not observable, any further taxonomic comparison cannot be made.
Age and occurrence.— Middle Hauterivian, Holcop- tychites neuquensis Zone, Agrio Formation; El Arenal, Las Lajas (Locality 28), Dept. Picunches, Neuquén,
Argentina. 0G, FY yee. Anditrigonia (Anditrigonia),
species juvenile indeterminate Plate 9, figure 5
Description.—Shell of moderately small size, ante- riorly inflated, and posteriorly compressed. Umbones opisthogyrous, situated in the anterior one-third of the shell. Dorsal margin convex. Dorsoposterior angle ob- tuse. Posterior margin very short. Ventroposterior an- gle acute. Ventral margin convex, curving evenly into the convex anterior margin. Flank occupying four-fifths of the shell surface, ornamented by two sets of costae, the anterior subconcentric, and the posterior subvert- ical, meeting in an L-shaped inflection at the posterior
50 BULLETIN 343
flank. Marginal carina poorly defined. Area presum- ably ornamented in the umbonal region. Escutcheon not observable.
Material.—One juvenile specimen, MOZ P3014, consisting in a well preserved left valve, fossilized in a coarse-grained, brownish limestone.
Measurements (in mm).—
Specimen No. IE H WwW H/L W/L MOZ P3014 N33) 10 - 0.74 -
Remarks.—The described specimen differs from the Tithonian Anditrigonia (A.) lamberti Levy (1967c, p. 139, pl. 1, figs. 2a—c; herein described) by its different shell shape, and in that the junction of the two set of flank costae is situated more posteriorly on the flanks. This form could also be considered questionably as a juvenile representative of the highly variable Tithon- ian and Neocomian Anditrigonia (A.) eximia (Philip- pi), but the immature nature of the specimen precludes a firm determination.
Age and occurrence.— Upper Tithonian, Substeuer- oceras koeneni Zone, Picin Leufu Formation; Cerro Pancho, Bajada de La Americana (Locality 31), Dept. Zapala, Neuquén, Argentina.
Anditrigonia (Anditrigonia) eximia tesselicaudata, new subspecies Plate 9, figures 1, 2
Holotype.—MOZ P1901, consisting in an adult spec- imen, with both valves very well preserved.
Type locality.—Camino nuevo a Los Molles (Lo- cality 34), Dept. Cataan Lil (39°13’S, 70°05'W), Picun Leufa Formation (Leanza, 1973), Mendoza Group (Groeber, 1946).
Etymology.—from the Latin, tesseli= forming squares; caudata=tail. Refers to the superimposed ver- tical costae and horizontal grooves resulting in a re- ticulate pattern of the posterior flank.
Diagnosis.—Shell large, pyriform. Not as elongate, and anterior margin not as convex, as in other species of Anditrigonia. Flank ornamented by two set of costae, the anterior one characterized by strong, widely spaced, subhorizontal and ondulate costae that meet the pos- terior set at the mid- flank in a form ofa V. Posterior flank crowded by subvertical, narrowly spaced costae superimposed by subhorizontal grooves, giving as a result a subquadrate pattern. Area very narrow, nearly smooth. Escutcheon wide, excavated, ornamented by faint oblique growth lines.
Measurements (in mm).—
Specimen No. if H WwW H/L W/L
MOZ P1901 90 65 23 0.72 0.25
Description.—Shell large, pyriform, anteriorly in- flated and posteriorly compressed, but not as elongate as other species of Anditrigonia. Umbones opistho- gyrous, situated in the anterior one-third of the shell. Dorsal margin concave. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle al- most 90°. Ventral margin slightly convex, curving evenly into the slightly convex anterior margin. Flank occupying almost the whole surface of the shell, or- namented by two set of costae, the anterior one being situated in the anterior flank and characterized by strong, widely spaced, subhorizontal and undulate cos- tae that meet the posterior set on the mid-flank in a form of a V. Posterior flank crowded by subvertical, narrowly spaced costae which are superimposed by subhorizontal grooves, giving as a result a reticulate pattern diagnostic for the species. Area very narrow, nearly smooth, ornamented by faint radial growth lines. Submedian groove present. Marginal and escutcheon carinae only impressed in the umbonal region, dis- appearing distally. Escutcheon wide, excavate, orna- mented by faint oblique growth lines.
Remarks.—Lambert (1944) demonstrated the high variability of Anditrigonia eximia (Philippi) and Pérez and Reyes (1983) included a number of “species” of Philippi under this heading. The described specimen clearly belongs in Anditrigonia eximia. Its not very elongate shell shape and moderately convex anterior margin fall within the range of variability of this spe- cies. The reticulate ornamentation on the posterior flank resulting from the intersection of subvertical costae with subhorizontal grooves, however, constitutes a sec- ondary character of subspecific value, and hence the previously described taxon is here regarded as a new subspecies of Anditrigonia (A.) eximia.
Age and occurrence.—Upper Tithonian, Substeuer- oceras koeneni Zone, Pican Leuft Formation; Camino nuevo a Los Molles (locality 34), Dept. Catan Lil, Ne- uquen, Argentina.
Genus ANTUTRIGONIA Leanza and Garate, 1987
Type species.— Trigonia opistolophophora Lambert, 1944, Berriasian/Valanginian boundary, Neuquén, Ar- gentina.
Diagnosis.—Shell of variable size, including oval, subquadrate or subrectangular forms. The flank is or- namented with concentric costae in the umbonal re- gion, which can be subsequently (1) interrupted by tubercles in the mid-anterior flank, (2) united by a tuberculate region forming an irregular V- or W- shaped inflection, or (3) showing alternations along a zone on the flank of ventral convexity in which bifurcation or trifurcation of costae may be present. Marginal carina only developed in the umbonal region, in later growth stages only demarcated by the different ornamentation
TRIGONUD BIVALVES OF ARGENTINA: LEANZA 51
of flank and area. Area ornamented by transverse cos- tae on its entire development. Escutcheon very narrow, with occasional transverse costellae (Leanza and Gar- ate, 1987).
Distribution.—Middle Tithonian to Valanginian. Argentina and Chile.
Antutrigonia opistolophophora (Lambert, 1944) Plate 13, figures 2, 6-9
Trigonia opistolophophora Lambert, 1944, p. 388, pl. 3. figs. 5, 6.
Anditrigonia opistolophophora (Lambert). Levy, 1967c, p. 137; Reyes and Pérez, 1982, p. A291; Reyes and Pérez, 1983, p. 59.
Antutrigonia opistolophophora (Lambert). Leanza and Garate, 1987, p. 223, pl. 8, figs. 1-3.
Description.—Shell medium to large in size, ante- riorly slightly inflated and posteriorly compressed. Umbones opisthogyrous, prominent, situated in the anterior one-third of the shell. Dorsal margin slightly concave. Dorsoposterior angle very obtuse. Posterior margin relatively short. Ventroposterior angle almost 90°. Ventral margin slightly convex, curving very strongly into the almost straight anterior margin. Flank occupying fourth-fifths of the shell surface, ornament- ed by strong costae of rounded section, arising diver- gently from the marginal carina, suffering subsequently a series of alterations along a zone which begin near the umbo and finish in the posterior third of the ventral margin. This zone forms an arc of ventral convexity in which bifurcation or trifurcation of costae can be observed, as well as some small tubercles in the first millimeters of each costa. Marginal carina only defined in the proximal part of the shell by the different or- namentation of flank and area. Area ornamented by strong transverse costae which are parallel to the pos- terior margin of the shell. In the proximal part of the area, these costae regularly alternate with other ones arising from the flanks, adding in its middle part some secondary costae that are born at the same level of the flank costae, forming with them a right angle. Escutch- eon very narrow, apparently smooth.
Material.—One topotype adult specimen, MOZ P0903/2, consisting of a relatively well preserved left valve.
Measurements (in mm).—
Specimen No. Ie H WwW H/L W/L MOZ P0903/2 =73 64 26 0.87 0.36 SGN 41-93 =55 51 20 0.92 0.36
Remarks.—As the topotype specimens of Antutri- gonia opistolophophora (Lambert) figured by Leanza and Garate (1987, pl. 8, figs. 1-3) and in this paper (see Pl. 13, figs. 2, 6-7) do not show clearly the trans- verse costation on the area which is characteristic for the genus Antutrigonia, the original illustation by Lam-
bert (1944, pl. 3, figs, 5-6) of the type species is here reproduced (see Pl. 13, figs. 8-9). In the dorsal view it is possible to observe a transversely costate area and a marginal carina only developed in the umbonal re- gion, disappearing to the distal portion of the shell.
Age and occurrence.—Late Berriasian/Early Valan- ginian, Spiticeras damesi and Neocomites wichmanni Zones, Lower part of Mulichinco Formation; Mallin Quemado, Sierra de la Vaca Muerta (Locality 7), Dept. Picunches, Neuquén, Argentina.
Antutrigonia frenguellii (Marinelarena, 1959) Plate 8, figures 1, 2
Trigonia frenguellii Marinelarena, 1959, p. 183, pl. 1, figs. 2, 3.
Anditrigonia frenguellii (Marinelarena). Levy, 1967c, p. 141; Reyes and Pérez, 1978, p. 20, pl. 5, fig. 1.
Anditrigonia (?) frenguellii (Marifelarena). Reyes and Perez, 1982, p. A298; Reyes and Pérez, 1983, p. 59.
Antutrigonia frenguellii (Marinelarena). Leanza and Garate, 1987, p. 223, pl. 7, figs. 5, 6.
Description.—Shell large, subrectangular. Umbones opisthogyrous, very anteriorly situated. Dorsal margin slightly concave. Dorsoposterior angle obtuse. Poste- rior margin relatively short. Ventroposterior angle con- vex. Ventral margin slightly convex, curving abruptly into the almost straight anterior margin. Flank occu- pying three-fourths of the shell surface, ornamented with two sets of mostly tuberculate costae meeting unordered along a band extending from the umbones toward the posterior one-third of the ventral margin. Area relatively narrow, ornamented by transverse cos- tellae in its whole development, extending from the escutcheon carina to the marginal carina. Submedian groove present. Marginal carina with transversely elon- gate swellings in its distal part. Escutcheon carina poor- ly defined. Escutcheon narrow and smooth.
Material.—One adult topotype specimen, MOZ P0918, a well preserved right valve (see Leanza and Garate, 1987, pl. 7, figs. 5, 6).
Measurements (in mm).—
Specimen No. Iv, H W H/L W/L MOZ P0918 76 58 18 0.76 0.24
Remarks.—Antutrigonia frenguellii (Marinelarena) shows transverse ornamentation on the whole area as it was stated by Marinelarena (1959, pp. 183-188) and confirmed by Leanza and Garate (1987, p. 224). For this reason, its assignment to Antutrigonia Leanza and Garate (1987) instead to Anditrigonia Levy (1967c) is doubtless. Antutrigonia frenguellii is a species closely related to Antutrigonia groeberi (Weaver, 1931, p. 257, pl. 20, fig. 105; herein described), but the latter species has subquadrate shape, and a more defined tuberculate stage in the mid-anterior flank which sharply separates the anterior and posterior set of costae.
52 BULLETIN 343
Age and occurrence.— Middle Tithonian, Windhau- seniceras internispinosum Zone, Picun Leufi Forma- tion; Canad6on del Sapo (Locality 20), Dept. Catan Lil, Neuqueén, Argentina.
Antutrigonia groeberi (Weaver, 1931) Plate 8, figures 3, 4, 7, 10
Trigonia groeberi Weaver, 1931, p. 257, pl. 20, fig. 105.
Anditrigonia groeberi (Weaver). Levy, 1967c, p. 137.
Anditrigonia (?) groeberi (Weaver). Reyes and Pérez, 1982, p. A291; Reyes and Pérez, 1983, p. 59.
Antutrigonia groeberi (Weaver). Leanza and Garate, 1987, p. 224, pl. 7, figs. 5, 6.
Description.—Shell medium to large in size, subquadrate, with rounded margins. Umbones opis- thogyrous, very anteriorly situated. Dorsal margin straight. Dorsoposterior angle very obtuse. Posterior margin long, almost of the same size as the anterior margin. Ventroposterior angle 90°. Ventral margin slightly convex, curving in an almost 90° angle into the straight anterior margin. Flank ornamented by two sets of costae which are separated in the mid-anterior flank by a region only ornamented by irregularly distributed tubercles. Area relatively narrow, ornamented by transverse costae in its whole development. Subme- dian groove absent. Marginal carina indistinct, only defined by the different ornamentation of area and flank. Escutcheon carina poorly defined. Escutcheon very narrow, containing very faint transverse costellae.
Material.—Four topotype adult specimens: MOZ P2069, complete, with both valves very well preserved; MOZ P0922/3, complete, but with the left valve bro- ken; MOZ P0367/1, a small right valve, relatively well preserved; MOZ P0367/2, a poorly preserved left valve. All specimens are fossilized in a fine-grained, yellow- ish-white limestone.
Measurements (in mm).—
Specimen No. 1b, H WwW H/L W/L MOZ P2069 78 68 30 0.87 0.38 MOZ P0922/3 40 37 13.5 0.92 0.33 MOZ P0367/1 30 29 10 0.96 0.33
MOZ P0367/2 33 31 11 0.93 0.33
Remarks.—Antutrigonia groeberi (Weaver) differs from Antutrigonia frenguellii (Marinelarena; herein de- scribed) in its subquadrate shape, in having a sharp tuberculate region 1n the mid-anterior flank which sep- arates the anterior and posterior set of costae, and ab- sence of a submedian groove in the area.
4ge and occurrence.—Upper Tithonian, Corongo- ceras alternans and Substeueroceras koeneni Zones, Picun Leuft Formation; Picin Leufa Creek and Route 40 (Locality 17), Dept. Zapala, Neuquén, Argentina.
Genus VIRGOTRIGONIA Alleman, 1985 (= Genus Maputrigonia Leanza, 1985)
Type species.— Virgotrigonia peterseni (non peter- senensis) Alleman, 1985. Lower Cretaceous (Valan- ginian), Peru.
Diagnosis.—Shell small to medium in size, pyri- form, posteriorly elongated, inequivalve. Umbones anteriorly situated. Flank ornamented in the umbonal region by concentric costae, then by two sets of tuber- culate costae that meet forming a V-shaped inflection in the anterior part of the flank. Area very narrow, ornamented with transverse costellae near the umbo, and radial costellae on its remaining surface. Shallow median groove present. Marginal carina beaded, well developed from the umbo to the ventroposterior junc- tion. Escutcheon carinae present. Escutcheon smooth (Leanza, 1985; Alleman, 1985; Pérez, Biro and Reyes, 1987).
Distribution.— Upper Jurassic (Upper Tithonian) to Lower Cretaceous (Valanginian). Argentina, Chile and Peru.
Discussion.—The genus Virgotrigonia Alleman (Nov. 1985) (=Maputrigonia Leanza, Dec. 1985) differs from Totrigonia van Hoepen (1929), Vaugonia Crickmay (1930b) and Anditrigonia Levy, 1967c, although hav- ing a similar flank ornamentation pattern, by the pe- culiar ornamentation of the area characterized by transverse costellae in the umbonal region, and by ra- dial costellae in the remaining surface. Anditrigonia (Paranditrigonia) Pérez and Reyes (1983) has a similar flank ornamentation with regard to Virgotrigonia, but differs in having only radial ornamentation on the area, and a marginal carina only developed in the umbonal region. Heterotrigonia Cox (1952) differs from Virgo- trigonia (=Maputrigonia) in having only radial cos- tation on the area, and untuberculated flank costae. The genus Lambertrigonia, n. gen. (type species: 77ri- gonia pichimoncolensis Lambert, 1944) is very similar to Virgotrigonia in shell shape, flank ornamentation, and presence of a well developed marginal carina; but in the area only exhibits radial costellae. At subfamily level, the taxonomic position of Virgotrigonia and Lambertrigonia, n. gen. offers some difficulties. Leanza (1985) stated that Maputrigonia (now Virgotrigonia) has affinities with the Vaugoniinae Kobayashi (1954), giving also the possibility that this genus could belong into the Iotrigoniinae Savelievy, if this subfamily is in- terpreted as a Cretaceous derivative of Vaugoniinae. In view of the importance that the author ascribes to the ornamentation of the area, however, it seems clear that affinities with Vaugoniinae or Iotrigoniinae are entirely superficial, as these subfamilies are integrated by representatives with totally different ornamenta- tional patterns on the area. As already mentioned in
TRIGONUD BIVALVES OF ARGENTINA: LEANZA 53
the discussion of Anditrigoniinae, n. subfam., these genera can be better assigned to this subfamily as it includes forms with radial and transverse ornament on the area.
Virgotrigonia hugoi (Leanza, 1985) Plate 14, figures 5-9 Maputrigonia hugoi Leanza, 1985, p. 280, figs. 2 : 1-5; Leanza and Garate, 1987, p. 220, pl. 8, figs. 8, 9.
Virgotrigonia hugoi (Leanza). Pérez and Reyes, 1987, p. 39, pl. 1, figs. 1-6, 10-15.
Description.—Shell of small to medium size, pyri- form, strongly inequilateral. Umbones prominent, sit- uated at anterior one-fourth of the shell. Dorsal margin slightly concave. Dorsoposterior angle obtuse. Poste- rior margin very short. Ventroposterior angle acute. Ventral margin slightly convex, curving evenly into the widely convex anterior margin. Flank occupying five-sixths of the shell surface, ornamented by two sets of tuberculate costae meeting in the anterior flank forming an irregular V-shaped inflection with angles between 50° and 90°. The posterior flank costae are subvertically inclined, intercepting the ventral margin at high angles. These costae are triangular in section, and their vertices bear faint crenulations giving them a serrated aspect. Area ornamented near the umbo with transverse costellae, by radial costellae in the mid- and distal portion, those being crossed by faint transverse growth lines, giving to the area a reticulate aspect. Mar- ginal carina well defined, with faint beads along its entire length. Escutcheon very narrow and elongate, smooth, exhibiting a small elevation in its proximal portion.
Material.—Seven topotype adult specimens from Mallin Quemado: MOZ P2733/1, complete; MOZ P2733/2, anterior part of the shell; MOZ P2733/3, complete, but the posterior part broken; MOZ P2733/ 4, with only the umbonal part of both valves preserved; MOZ P2733/5, fragment ofa right valve; MOZ P2733/ 6, external mold of a right valve; MOZ P0949/1, a complete right valve (see Leanza and Garate, pl. 8, fig. 8). These specimens were found in dark brown silt- stones in association with collophane nodules (see Leanza, 1985). Three hypotype adult specimens from Salitral de Los Alazanes: MOZ P2332/1, anterior flank with both valves; MOZ P2332/2, anterior flank with both valves; MOZ P2332/3, anterior flank of a right valve. These specimens are replaced by a white silic- ified material.
Measurements (in mm).—
Specimen No. 1G H WwW H/L W/L
MOZ P2733/1 62 39 10 0.62 0.16
Remarks.— Virgotrigonia hugoi (Leanza) differs from V. peterseni Alleman (1985) from the Valanginian of Morro Solar, Distrito de Chorrillos, Lima, Peru, in having tuberculate costae on the flanks, and narrower radial costellae on the area. Pérez, Biro and Reyes (1987) have recently assigned to Virgotrigonia hugoi (Leanza) specimens previously assigned to Vaugonia chunumayensis (see Reyes and Pérez, 1978, 1979) from the uppermost Tithonian/lowermost Berriasian (Ju- rassic—Cretaceous boundary) of Lo Valdés Formation, southwest from Santiago, Central Chile. The north- western European late Jurassic—early Cretaceous genus Turbitrigonia Kelly, 1984 (type species: Turbitrigonia boudiccae Kelly, 1984) exhibits flank ornamentation and shell shape comparable in some extent to Virgo- trigonia, but the area is completely smooth, lacking marginal and escutcheon carina.
Age and occurrence.— Lower Berriasian, Argentini- ceras noduliferum Zone, Vaca Muerta Formation; Mal- lin Quemado (Locality 7), Dept. Picunches, and Sali- tral de los Alazanes (Locality 30), Dept. Picunches, Neuqueén, Argentina.
Genus LAMBERTRIGONIA, new genus
Type species.—Trigonia pichimoncolensis Lambert, 1944, Upper Jurassic (Kimmeridgian), Neuquén, Ar- gentina.
Diagnosis.—Shell small, pyriform. Flank orna- mented by two sets of costae forming an L- or V-shaped inflection on its mid-posterior portion. Marginal carina beaded, well developed along its entire length. Area radially ornamented by faint costellae, asymmetrically divided by a submedian groove. Escutcheon carina poorly defined. Escutcheon excavate, apparently smooth.
Distribution.—Upper Jurassic (Kimmeridgian). Ar- gentina.
Etymology.—This genus is dedicated to Luis R. Lambert, who in 1944 produced the first trigoniid monograph in Argentina.
Discussion.—Trigonia pichimoncolensis Lambert (1944) remained as a taxonomically uncertain species for a long time. In 1988 the present author had the opportunity to rediscover the fossil locality near La- guna Miranda, and to collect some new specimens. The completely radial costation of the area and the pro- truding marginal carina of this species have been con- firmed, thus allowing erection of Lambertrigonia, n. gen. The new genus has superficial affinities with Het- erotrigonia Cox (1952), Anditrigonia (Paranditrigonia) Reyes and Pérez (1983), and Virgotrigonia Alleman (1985) (=Maputrigonia Leanza, 1985). The Upper Cre- taceous Heterotrigonia Cox, 1952 (type species: Tri- gonia diversicostata Whiteaves, 1876) exhibits round-
54 BULLETIN 343
ed and strong radial costae on the area, lacks a marginal carina, and the flank is ornamented by two sets of strong and rounded costae forming an L-shaped in- flection in the anterior flank. The Early Cretaceous Virgotrigonia Alleman (type species: Virgotrigonia pe- terseni Alleman, 1985) has a very similar flank cos- tation pattern, but the area is ornamented by transverse costellae in the umbonal portion which are totally ab- sent in Lambertrigonia, n. gen. Leanza (1985) and Leanza and Garate (1987) tentatively included pichi- moncolensis of Lambert in the genus Maputrigonia, but as Pérez, Bird and Reyes (1987, p. 39) observed, T. pichimoncolensis lacks transverse costellae in the umbonal region of the area, and Pérez and coauthors stated that this species might constitute the type of a new genus. The Neocomian subgenus Anditrigonia (Paranditrigonia) Reyes and Pérez (1983) (type species: A. (P.) potrerillensis Reyes and Pérez, 1983) exhibits an area with faint, radial costellae, but the size of its representatives is much larger, the marginal carina is only poorly developed in the umbonal region, and the flank ornamentation is much more complex, as it dis- plays V- and W-shaped junctions of the two sets of costae in which some tubercles can occur. Therefore, the affinities to Paranditrigonia can be regarded as only superficial. For discussion of inclusion of Lambertri- gonia in Anditrigoniinae, n. subfam., see remarks above.
Lambertrigonia pichimoncolensis (Lambert, 1944) Plate 5, figures 5, 6
Trigonia pichimoncolensis Lambert, 1944, p. 372, pl. 4, fig. 4. cf. Maputrigonia pichimoncolensis (Lambert). Leanza and Garate, 1987, p. 20, pl. 7, fig. 4.
Description.—Shell small, pyriform, somewhat in- flated. Umbones opisthogyrous, situated in the ante- rior one-fourth of the shell. Dorsal margin slightly con- cave. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle acute. Ventral mar- gin slightly convex, curving evenly in the strongly con- vex anterior margin. Flank occupying three-fourths of the shell surface, ornamented by two sets of costae, the anterior composed by 12-14, faint, widely spaced, sub- concentric costae, that meet the posterior set in a V-shaped junction. The posterior costae are subvert- ically oriented, thicker and their interspaces narrower. To one anterior costa usually correspond two poste- rior costae. The line of junctions of these two sets of costae begins in the umbonal region and finishes in the mid-posterior part of the ventral margin. Marginal ca- rina beaded, well developed along its entire length, smooth, and slightly arched. Area completely orna- mented by two faint, radial costellae at both sides of a very protruding submedian groove. Escutcheon ca-
rina poorly defined. Escutcheon excavate, apparently smooth.
Material.—Four topotype adult specimens, MOZ P4252/1, a very well preserved a right valve; MOZ P4251/2,a very well preserved left valve, MOZ P4252/ 3&4, poorly preserved right valves. The specimens were found in coarse-grained, light-brown sandstones.
Measurements (in mm).—
Specimen No. L H W H/L W/L
MOZ P4252/1 15 8 - 0.53 = MOZ P4252/2 23 13 - 0.56 -
Remarks.—Lambertrigonia pichimoncolensis (Lam- bert) shows superficial affinities with Heterotrigonia Cox (1952), Anditrigonia (Paranditrigonia) Reyes and Pérez (1983) and with Virgotrigonia Alleman (1985). This taxon remains as an isolated and monospecific genus of Kimmeridgian age, from which probably were phyletically derived the very abundant Tithonian and Neocomian South American Anditrigoniinae.
Age and occurrence.—Kimmeridgian, unknown am- monite Zone, Tordillo Formation; northwest of La- guna Miranda (Locality 33), Dept. Zapala, Neuquén, Argentina.
Subfamily RUTITRIGONIINAE van Hoepen, 1929
Genus RUTITRIGONIA van Hoepen, 1929
Type species.— Rutitrigonia peregrina van Hoepen, 1929, Lower Cretaceous, Zululand, South Africa.
Diagnosis.—Pyriform to ovate. Flank ornamented on its anterior part with narrow, rather flexuous, sub- concentric costae. Area narrow, ornamented by oblique costae on the umbonal region, subsequently smooth except for growth lines. Marginal and escutcheon ca- rinae poorly defined, except near umbo. Escutcheon narrow, smooth or with oblique costellae (see van Hoe- pen, 1929; Cox, 1969).
Distribution.— Upper Jurassic (Tithonian) to Upper Cretaceous. Cosmopolitan.
Rutitrigonia agrioensis (Weaver, 1931) Plate 16, figures 1-3 Trigonia agrioensis Weaver, 1931, p. 266, pl. 27, figs. 142-146; Lambert, 1944, p. 373, pl. 5, figs. 1-4.
Rutitrigonia agrioensis (Weaver). Nakano, 1963, p. 526; Reyes and Pérez, 14, pl. 2; Leanza and Garate, 1987, p. 224, pl. 12, figs. 3, 4.
Description.—Shell of medium size, pyriform, an- teriorly inflated and posteriorly compressed. Umbones opisthogyrous, situated on the anterior one-third of the shell. Dorsal margin concave. Dorsoposterior angle ob- tuse. Posterior margin very short. Ventroposterior an- gle almost 90°. Ventral margin slightly convex, curving evenly into the strongly convex anterior margin. Flank
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 55
occupying almost the whole surface of the shell, or- namented only on its anterior part by nearly 30 sub- horizontal costae exhibiting abrupt dorsal slope, and softly inclined ventral slope. These costae tend to dis- appear in the posterior flank where only faint growth lines remain. Area extremely narrow, ornamented by faint, oblique costellae in the proximal region, subse- quently smooth except for growth lines. Marginal ca- rina only defined in the umbonal region, distally be- coming wide and blunt. Escutcheon carina forming a shallow edge in the proximal region, then undefined. Escutcheon very elongated and strongly depressed, with some proximal faint oblique costellae, subsequently smooth.
Material.—Four adult hypotype specimens, MOZ P0920/1,2 and MOZ P0920/3, all of them complete, with both valves well preserved; MOZ P3112, a well preserved right valve.
Measurements (in mm).—
Specimen No. L H W H/L W/L MOZ P0920/1 56 39 16 0.69 0.28 MOZ P0920/2 46 30 13 0.65 0.28 MOZ P0920/3 59 38 15 0.64 0.25
Remarks.—In contrast with the generic diagnosis of Rutitrigonia by Cox (1969, p. N487), the area and escutcheon of the present material are not smooth, but are ornamented by faint transverse and oblique cos- tellae, especially in the umbonal region. Rutitrigonia agrioensis (Weaver) has affinities with the type species R. peregrina van Hoepen (1929, p. 31, pl. 7, figs. 13- 16) from the Lower Cretaceous from Zululand, South Africa, but the Argentine species has less dense costae that disappear more anteriorly on the flanks. Rutitri- gonia weaveri (Stoyanow, 1949, p. 87, pl. 15, figs. 4— 8) from the Lower Cretaceous of southeastern Arizona, U.S.A., is also a very closely related species, but the South American species is relatively longer, and the wavy character of the costae in the anterior region of the flank is much less pronounced.
Age and occurrence.—Lower Hauterivian, Lytico- ceras pseudoregale Zone, Agrio Formation; Cerro Ne- gro Chico de Pictn Leuft (Locality 18), Dept. Catan Lil, Neuquén, Argentina. The specimens were found in this locality at the lowermost levels of the Agrio Formation overlying the Mulichinco Formation. The same species is also present in Middle and Upper Hau- terivian outcrops of the Agrio Formation in other lo- calities of the Neuquén Basin.
Rutitrigonia kauffmani, new species Plate 15, figures 1-5
Holotype.—MOZ P3527/2, a well preserved left valve.
Paratypes.—MOZ P3527/1, a well preserved right valve; MOZ P3527/3, a complete specimen with both valves well preserved; MOZ P3527/3, a complete spec- imen, with the posterior part of the shell broken; MOZ P3527/5, a poorly preserved left valve; MOZ P3527/ 6, a well preserved right valve; MOZ P4295/1, a well preserved right valve; MOZ P4295/2, a well preserved left valve; MOZ P4295/3, a juvenile specimen with a well preserved right valve; MOZ P4281, a poorly pre- served left valve. All are adult specimens, with the exception of MOZ P4295/3.
Type locality.—Cerro Mesa, Covunco (Locality 8), Dept. Zapala (38°44'S, 69°55'W), Agrio Formation (Weaver, 1931), Mendoza Group (Groeber, 1946).
Etymology.—This species is dedicated to American paleontologist Dr. Erle G. Kauffman (Boulder, Colo- rado, U.S.A.).
Diagnosis.— Rutitrigonia moderately small to small in size, somewhat pyriform. Flank ornamented by faint subhorizontal costae that tend to disappear toward the posterior flank. Area ornamented by weak, oblique costae that are the continuation of those on the flank. Marginal carina defined by a sharp edge between the costae from the flank and area. Escutcheon only or- namented by faint growth lines.
Measurements (in mm).—
Specimen No. 1G; H WwW H/L W/L
MOZ P3527/1 19 1S 4.5 0.78 0.23 MOZ P3527/2 20 15 6 0.75 0.30 MOZ P3527/3 24 17 5 0.70 0.20 MOZ P3527/4 19 14.5 7 0.76 0.36 MOZ P3527/5 - 13%5 6 - -
MOZ P3527/6 24 17 6.5 0.70 0.27 MOZ P4295/1 27 19 7 0.70 0.25 MOZ P4295/2 WES, 13 5 0.74 0.28 MOZ P4295/3 7.8 Spe) 225 0.70 0.32 MOZ P4281 27.5 20 9 0.72 0.32
Description.—Shell moderately small to small in size, pyriform. Umbones opisthogyrous, situated in the an- terior one-third of the shell. Dorsal margin slightly convex. Dorsoposterior angle obtuse. Posterior margin short. Ventroposterior angle acute. Ventral margin slightly convex, curving evenly into the gently convex anterior margin. Flank occupying three-fourths of the shell surface, ornamented by nearly 22, at first sub- concentric, then subhorizontal, somewhat wavy, faint costae that tend to disappear on the ventroposterior region of the flank. These costae show an asymmetrical profile, very abrupt dorsally and weakly inclined ven- trally. Area very narrow, ornamented on almost its whole development by oblique costae which are the continuation of those arising from the flanks. Marginal carina defined by a sharp edge just formed when the flank costae penetrates the area. Escutcheon carina de-
56 BULLETIN 343
fined by a sharp change in direction of the costellae arising from the area. Escutcheon narrow and very elongated, ornamented by very fine oblique costellae arising from the area.
Remarks.—Rutitrigonia kauffmani, n. sp. 1s easily distinguishable from the other known species of Ru- titrigonia van Hoepen (1929): apart from its small size, it is not very elongated and it has on the umbonal region a sharp demarcation of escutcheon, area and flank. The juvenile specimen MOZ P4295/3 (L=7.8 mm) exhibits the same characteristics of the adult forms, which only reach maximum sizes of 28 mm. R. kauffmani, n. sp. differs from R. agrioensis (Weaver, 1931, p. 266, pl. 27, figs. 142-146; herein described) by: (1) its smaller size; (2) its less pyriform and elon- gated shape; (3) sharper demarcation of escutcheon, area and flank where, and (4) the ornamentation reach- es much more distal portion of the shell. The H/L ratio of both species are: Rutitrigonia agrioensis = 0.64 to 0.69, and Rutitrigonia kauffmani, n. sp. = 0.70 to 0.78.
Rutitrigonia sanchuensis (Nakano) (in Kobayashi and Nakano, 1958, p. 145, pl. 12, figs. 1-8) from the Albian of western Japan, is close to R. kauffmani, n. sp. but differs from the Argentine species in having a more prominent umbo, more elongated shell shape, and flank more densely costulate.
Age and occurrence.—Lower and Middle Hauteri- vian, Lyticoceras pseudoregale and Holcoptychites neu- quensis Zones, Agrio Formation; Cerro Mesa, Covun- co (Locality 8), Dept. Zapala, Neuquén, Argentina.
Rutitrigonia, species juvenile indeterminate Plate 9, figure 8
Description.—Shell small, rostrate, pyriform, ante- riorly inflated and posteriorly acuminated. Umbones opisthogyrous, situated in the anterior one-third of the shell. Dorsal margin concave. Dorsoposterior angle ob- tuse. Posterior margin very short. Ventroposterior an- gle acute. Ventral margin first straight, then slightly convex, curving evenly into the widely convex anterior margin. Flank occupying four-fifths of the shell surface, ornamented by approximately 10, widely separated, subconcentric costae which disappear in the smooth posterior flank. Marginal carina poorly defined except near umbo. Area and escutcheon too poorly preserved for an accurate description.
Material.—One juvenile specimen, MOZ P5002, consisting in a poorly preserved left valve, fossilized in a yellowish-white fine-grained, limestone.
Measurements (in mm).—
Specimen No. L H W H/L W/L
MOZ P5002 20 14 5 0.70 0.25
Remarks.—The described specimen is characterized by a pyriform shell with widely spaced subconcentric costae on the anterior flank. It can readily be assigned to Rutitrigonia van Hoepen (1929), but its immature status and poor preservation of the area and escutcheon preclude any more definite identification. This speci- men is very important, however, as it marks the earliest appearance of the genus Rutitrigonia in west-central Argentina in the Uppermost Jurassic.
Age and occurrence.—Upper Tithonian, Corongo- ceras alternans Zone, Picin Leufti: Formation; Cerrito Caracoles (Locality 11), Dept. Zapala, Neuquén, Ar- gentina.
Subfamily BUCHOTRIGONIINAE, new subfamily
Diagnosis.—Shell trigonal. Flank ornamented in the umbonal region by oblique costae. On a later growth stage two sets of costae appear, a subconcentric set in the anterior and central flank, and a subvertical set in the posterior flank, these forming a ventrally directed V-shaped inflection at their junction. This costation can be replaced in some species by concentric rugae near the ventral margin. Wide antecarinal depression usually present. Area diagonally costate in early growth stages, then smooth. Marginal carina well developed. Escutcheon carina absent. Escutcheon smooth, or weakly ornamented by growth lines or faint costellae.
Distribution.— Upper Jurassic (Upper Tithonian) to Upper Cretaceous (Campanian).
Discussion.—Kobayashi and Mori (1955, p. 76) placed Buchotrigonia Dietrich, 1938 (type species: T7i- gonia abrupta von Buch, 1839) into the subfamily Vau- goniinae. Saveliev (1958) assigned Buchotrigonia and Syrotrigonia Cox, 1952 [type species: Buchotrigonia (Syrotrigonia) fraasi Cox, 1952 = B. (S.) libanotica (Vokes, 1942, p. 168, pl. 4, figs. 8—12)] into his Quad- ratotrigoniinae together with the genera Asiatotrigonia Cox (1952) and Korobkovitrigonia Saveliev (1958). Nakano (1960) included Buchotrigonia in Vaugoni- inae. Some years later the same author, after revising the subfamily Quadratotrigoniinae, stated that Syro- trigonia‘*. . . possibly belonged to the Vaugoniinae and an issue derived from Vaugonia by the development of the antecarinal depression on the disk” (Nakano, 1968, p. 33). At the same time, Nakano (1968) com- mented that Buchotrigonia had been derived from Lin- otrigonia “*. . . by the effacement of the carinae and the development of the L shaped costation as can be judged from the surface sculpture’, and he transferred Buch- otrigonia to the Myophorellinae. Pérez and Reyes (1980, 1986) presented an excellent taxonomic and historical revision of Buchotrigonia and Syrotrigonia from South America and the rest of the world. These Chilean authors did not comment, however, on the subfamily status of either taxon, pointing out their
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 3)7/
differences from the genera Jotrigonia, Anditrigonia and Megatrigonia, including them plainly in the Fam- ily Trigoniidae.
In my opinion, Buchotrigonia and Syrotrigonia are extremely closely related taxa that cannot be separated into different subfamilies as Nakano did (1968, p. 33). Although probably derived from Vaugonia, their re- lationships with Vaugoniinae, Myophorellinae, Quad- ratotrigoniinae, or even Megatrigoniinae are entirely superficial, as strong differences in the evolution of flank costae and other morphological parameters in comparison with these subfamilies can be detected. The flank of Buchotrigonia and Syrotrigonia exhibits a very distinct ornamentation pattern characterized in the umbonal region by oblique costae, and in later growth stages by a subconcentric set of costae on the anterior and central flank, and a subvertical set of cos- tae in the posterior flank, both meeting in a form of V-, W- or zig-zag-shaped junction. Together with the presence of an antecarinal depression (Syrotrigonia) and transverse ornamentation in the proximal area (Buchotrigonia), these closely related taxa, elevated here to the genus rank, are very distinctive members of the Family Trigoniidae. As a matter of fact, this had al- ready been implicit in the work of Stoyanow (1949, p. 83), who created the Group of Trigonia abrupta while describing Trigonia reesidei, now considered a Buch- otrigonia. Therefore the subfamily Buchotrigoniinae, n. subfam. is proposed, including Buchotrigonia and Syrotrigonia, ranging in age from the Upper Tithonian to the Campanian. It is possible that the new subfamily was derived from the Jurassic Vaugoniinae, and de- veloped during the Lower Cretaceous in parallel evo- lution with the subfamily Apiotrigoniinae Tashiro (1979).
According to the revision of Buchotrigonia by Pérez and Reyes (1980), the following original species can be assigned to this genus: Trigonia abrupta von Buch (1839), Trigonia reesidei Stoyanow (1949), and Buch- otrigonia (B.) topocalmensis Pérez and Reyes (1980). Recently, Villamil (1991, in press) described three new species of Buchotrigonia from the Lower Cretaceous of Colombia ranging in age from the Berriasian to the Upper Valanginian. He demonstrated that the point where the costae meet has a more ventral position on the flank as the species become younger in age.
After the revision of Syrotrigonia by Pérez and Reyes (1986) the following species belong to this genus: S'yr- otrigonia fraasi Cox (1952), Trigonia distans (Noetling, 1886), Trigonia gerthi (Lisson, 1930), Trigonia stein- manni (Lisson, 1930), Trigonia paradisensis (Lisson, 1930), Buchotrigonia (?) aff. paradisensis (Lisson, 1930 in Etayo Serna, 1985), Buchotrigonia (B.) sp. (Man- cenido and Damborenea, 1984), Buchotrigonia (Syr- otrigonia) chilensis Pérez and Reyes (1986) and B. (S.)
biroi Pérez and Reyes (1986). These species range in age from the Late Jurassic (Upper Tithonian) to the Early Cretaceous (Neocomian). To this list the Lower Hauterivian Syrotrigonia brocardoi, n. sp. from the Agrio Formation from west-central Argentina, must now be added.
Genus SYROTRIGONIA Cox, 1952
Type species.—Buchotrigonia (Syrotrigonia) fraasi Cox, 1952 (=Trigonia libanotica Vokes, 1942; =T. syr- iaca Fraas, 1878 non Conrad), Lower Cretaceous, Mid- dle East (Syria).
Diagnosis.—Shell trigonal, short. Flank with ante- carinal depression ornamented by oblique, subconcen- tric and subvertical costae. The oblique costae are pres- ent in the umbonal region and cut the growth lines. The subconcentric costae are present in the anterior and central flank. The subvertical costae are situated in the posterior flank. These two sets of costae meet in the posterior flank forming a V-, W- or zig-zag- shaped pattern. Antecarinal depression present. Area wide, subplanate, with transverse costellae in the prox- imal region, then smooth. Marginal carina well de- veloped on its entire length. Escutcheon not well im- pressed (Cox, 1952, 1969, Pérez and Reyes, 1986).
Distribution.— Upper Jurassic (Upper Tithonian) to Lower Cretaceous (Aptian). Middle East (Syria), Eu- rope (Spain), and South America (Colombia, Peru, Chile and Argentina).
Syrotrigonia brocardoi, new species Plate 16, figures 4, 7, 10, 12
Holotype. —MOZ P5319, an adult, complete shell, with both valves relatively well preserved, fossilized in a yellowish-gray limestone.
Paratype. —MOZ P5318, and adult, complete shell, with both valves relatively well preserved. Same size and matrix as the holotype.
Type locality.—Pichaihue Abajo (Locality 3), Dept. Loncopué (37°45'S, 70°14’'W), Agrio Formation (Weaver, 1931), Mendoza Group (Groeber, 1946).
Etymology.—This species is dedicated to Prof. Giu- sepe Brocardo, Director of the Museum San Juan Bos- co (Torino, Italy), for his contributions to the Museum Juan Olsacher.
Diagnosis.—Shell of medium size, trigonal. Anterior margin straight. Flank weakly ornamented by oblique umbonal costae, and then by subconcentric and sub- vertical costae meeting in a down-pointing V-shaped inflection in the posterior flank, those being replaced in a mid-late growth stage by conspicuous concentric rugae. Antecarinal depression extremely shallow. Area ornamented by transverse costae in the umbonal re- gion, then smooth. Marginal carina well developed,
58 BULLETIN 343
forming an edge between area and flank. Escutcheon carina absent. Escutcheon smooth.
Description.—Shell of medium size, trigonal and short in shape. Umbones opisthogyrous, slightly ele- vated, very anteriorly situated. Dorsal margin straight. Dorsoposterior angle widely obtuse. Posterior margin short. Ventroposterior angle 90°. Ventral margin wide- ly convex, curving evenly into the straight, anterior margin. Flank occupying four-fifths of the shell surface, weakly ornamented in the umbonal region by approx- imately 10 oblique, faint costae that cut the growth lines. As the growth of the shell continues, a subcon- centric and subvertical set of costae appears, situated in the anterior and central flank, and in the posterior flank respectively, both meeting in a ventrally directed V-shaped junction. In the mid-late growth stage this ornamentation is replaced by concentric folds and ru- gae which are characteristic for the species. Antecarinal depression very shallow in the distal portion of the shell. Area narrow and flat, forming a sharp edge with the flank surface, ornamented in the umbonal region by transverse costae which are the continuation of those costae arising from the flank. Distal area smooth. Mar- ginal carina defined by the change in direction of the flank costae toward the area. Escutcheon carina absent. Escutcheon smooth.
Measurements (in mm).—
Specimen No. iv H W H/L W/L MOZ P5318 30 28 10 0.93 0.33 MOZ P5319 35 31 11 0.88 0.31
Remarks.—Syrotrigonia brocardoi, n. sp. is an ex- treme representative of Syrotrigonia Cox (1952), easily distinguishable by its weak flank ornamentation, its almost straight anterior margin, extremely shallow an- tecarinal depression, and by its sharp concentric rugae, which are present at a mid-late growth stage and re- place the more typical flank ornamentation of this ge- nus. In this sense, the closest species to Syrotrigonia brocardoi, n. sp. is Syrotrigonia biroi Pérez and Reyes (1986, p. 85, pl. 2, figs. 1-20) from the Neocomian Pedernales Formation, Chile, in which these characters are well developed. The Argentine species, however, has a different shell shape with an straight anterior margin, and the concentric rugae in the ventral part of the flank are more conspicuous and begin at an earlier growth stage. These specific characters also separate Syrotrigonia brocardoi, n. sp. from Syrotrigonia gerthi (Lisson, 1930, p. 8, pl. 3, figs. 1-5), Syrotrigonia stein- manni (Lisson, 1930, p. 6, pl. 2, figs. 1-3) and Syro- trigonia paradisensis (Lisson, 1930, p. 18, pl. 9, figs. 1-5) of the Valanginian of Pert.
Age and occurrence.—Lower Hauterivian, Lytico- ceras pseudoregale Zone, Agrio Formation; Pichaihue
Abajo (Locality 3), Dept. Loncopué, Neuquén, Argen- tina.
Subfamily PTEROTRIGONIINAE van Hoepen, 1929
Genus PTEROTRIGONIA van Hoepen, 1929
Type species.—Pterotrigonia cristata van Hoepen, 1929, Middle Cretaceous, Zululand, South Africa.
Diagnosis.—Shell small to medium size, crescent- shaped, gibbous, Umbones very elevated, strongly op- isthogyrous. Dorsal margin strongly concave. Flank anteriorly ornamented by narrow, high, widely-spaced, steep or oblique, usually tuberculated costae. Posterior flank costae subvertical, narrow, crowded, and finely crenulated. Area very narrow, smooth or transversely ridged, strongly curved, with an upward-facing con- cavity. Marginal and escutcheon carinae poorly de- fined, except near umbo. Escutcheon wide, well im- pressed near umbo (van Hoepen, 1929; Cox, 1969; Kobayashi and Nakano, 1957; Cooper, 1989).
Distribution. — Lower Cretaceous (Berriasian) to Up- per Cretaceous (Maastrichtian). Cosmopolitan.
Subgenus PTEROTRIGONIA van Hoepen, 1929
Pterotrigonia (Pterotrigonia) aliformis (Parkinson, 1811) Plate 14, figure 3 Trigonia aliformis Parkinson, 1811, p. 176, pl. 12, fig. 9; Agassiz, 1840, p. 31, pl. 7, figs. 14-16, pl. 8, fig. 12; d’Orbigny, 1843, p. 143, pl. 291, figs. 1-3; Coquand, 1865, p. 134; Lycett, 1875, p. 116, pl. 25, figs. 3-6. Trigonia cf. aliformis Parkinson. Weaver, 1931, p. 258. Pterotrigonia (Pterotrigonia) aliformis Parkinson. Reyes and Pérez, 1978, p. 12, pl. 3, fig. 2. Pterotrigonia aliformis Parkinson. Leanza and Garate, 1987, p. 225, pl. 11, figs. 3-7.
Description.—Shell of medium size, strongly ine- quilateral, longer than high. Umbones strongly opisth- ogyrous, elevated, situated in the anterior one-third of the shell. Anterior part of the shell inflated and pos- terior part compressed. Dorsal margin strongly con- cave. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle 90°. Ventral margin slightly convex, curving evenly into the strongly con- vex anterior margin. Flank very wide, occupying five- sixths of the shell surface, ornamented by simple, rounded, oblique, beaded costae, with their interspaces widening toward the anterior and ventral margins, be- coming at the same time thicker and more prominent. Posterior set of costae subvertical, showing subtrian- gular section and serrated surface. Area very narrow, with an upward-facing concavity, ornamented by transverse costellae in the proximal region, subse- quently smooth. Submedian groove present. Marginal carina well developed, smooth. Escutcheon carina
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 59
poorly defined. Escutcheon narrow, elongated and ex- cavated, ornamented by faint oblique costellae.
Material.—Two adult hypotype specimens: MOZ P2687, a very well preserved external mold of a left valve, and MOZ P2686/1, a complete shell with the posterior part somewhat damaged. The specimens are phosphatized, and preserved in a violet-brownish phosphatic siltstone, occurring in association with Vir- gotrigonia hugoi (Leanza).
Measurements (in mm).—
Specimen No. 1 H W H/L W/L MOZ P2687 36 18 6 0.50 0.16
Remarks.—Pterotrigonia (P.) aliformis (Parkinson, 1811) is a cosmopolitan species known in the Lower Cretaceous of Europe, North and South America, for- mer Soviet Union and Japan. The Argentine specimens show affinities with the Neocomian P. (P). aliformis attenuata (Lycett, 1878, p. 118, pl. 25, fig. 6) and P. (P.) vectiana (Lycett, 1875, p. 123, pl. 24, figs. 10-11, pl. 25, fig. 7) from the Isle of Wight, England, and with P. (P.) cubanica (Sinzow, in Saveliev, 1958, p. 291, pl. 34, figs. 1-6) from the Lower Cretaceous of Turkmen- istan. It is possible that all these very closely related species of Pterotrigonia are representatives of P. (P.) aliformis (Parkinson, 1811), but analysis of this pos- sibility falls beyond the scope of this paper.
Age and occurrence.—Lower Berriasian, Argentini- ceras noduliferum Zone, Vaca Muerta Formation; Mal- lin Quemado (Locality 7), Dept. Picunches, Neuquén, Argentina.
Subgenus NOTOSCABROTRIGONIA Dietrich, 1933
Type species.—Trigonia tocaimaana Lea, 1841, Lower Cretaceous (Neocomian), Venezuela and Co- lombia.
Diagnosis.— Like Pterotrigonia, but generally larger and with flank ornament, with coarse, widely spaced costae that are generally weakly tuberculated. Posterior flank costae rather distant (Dietrich, 1938; Cooper, 1989).
Distribution.—Upper Jurassic (Tithonian) to Cre- taceous (Neocomian—Campanian). South America, North America, Japan, England, South Africa.
Pterotrigonia (Notoscabrotrigonia) coheni, new species Plate 6, figures 5, 8-10
Holotype.—MOZ P4723, a well preserved adult left valve, fossilized in a yellow-grayish fine-grained lime- stone.
Paratypes.— Three adult specimens: MOZ P3073, a well preserved right valve; MOZ P5764, a poorly pre-
served left valve; MOZ P5765, a well preserved right valve.
Type locality.— Cerrito Caracoles (Locality 11), Dept. Zapala (38°49'S, 70°09'W), Picin Leufa Formation (Leanza, 1973), Mendoza Group (Groeber, 1946).
Etymology.—This species is dedicated to my friend Richard Cohen (Boulder, Colorado) who actively sup- ports the Museum Juan Olsacher.
Diagnosis.—Shell of medium to large size, inflated anteriorly and attenuated posteriorly, with the um- bones prominent, elevate and highly opisthogyrous. Flank ornamented anteriorly by coarse, widely spaced weakly tuberculated, costae, and posteriorly by rather distant subvertical costae. Area very narrow, with faint transverse costellae. Marginal and escutcheon carinae poorly defined. Escutcheon relatively wide, somewhat excavated, ornamented by faint oblique costellae.
Measurements (in mm).—
Specimen No. Ly H W H/L W/L MOZ P4723 52 39 16 0.75 0.30 MOZ P5764 =40 28 10 0.70 0.25 MOZ P5765 =41 28 10 0.68 0.24 MOZ P3073 54 37 16 0.68 0.29
Description.—Shell of medium to large size, ante- riorly inflated and posteriorly compressed, longer than high. Umbones very inflated, elevated, highly opistho- gyrous, and very anteriorly situated. Dorsal margin strongly concave. Dorsoposterior angle obtuse. Pos- terior margin very short. Ventroposterior angle almost 90°. Ventral margin broadly convex, curving evenly into the slightly convex anterior margin. Flank very wide, occupying five-sixths of the shell surface, orna- mented on its anterior and central region by subcon- centric, then oblique, coarse, widely spaced, weakly tuberculate costae, and in its posterior region by rather spaced, subvertical untuberculated costae. Area ex- tremely narrow, ornamented by faint transverse cos- tellae. Submedian groove present. Marginal and es- cutcheon carinae poorly defined. Escutcheon relatively wide, excavated, ornamented by faint oblique costel- lae.
Remarks.— Although Kobayashi and Nakano (1957) and Cox (1969) considered Notoscabrotrigonia Die- trich a synonym of Pterotrigonia van Hoepen, the pres- ent author follows the recent interpretation of this tax- on by Cooper (1989, p. 242), who placed it as a subgenus of Pterotrigonia characterized by sparsely or weakly tuberculated anterior costae, and rather widely-spaced posterior costae. The described specimens can there- fore be assigned to the subgenus Prerotrigonia (Notos- cabrotrigonia) Dietrich (1933) on the basis of their shell shape, characterized by a highly inflated anterior part, and the peculiar flank ornamentation, which exhibits
60 BULLETIN 343
on its anterior and central portions coarse, widely spaced, weakly tuberculated costae, and in its posterior region rather spaced, subvertical, untuberculated cos- tae. P. (N.) coheni, n. sp. differs from the Neocomian P. (N.) tocaimaana (Lea, 1841, p. 6, pl. 9, fig. 8, see also Dietrich, 1938, p. 94, pl. 19, figs. 1-2), the type species of Notoscabrotrigonia, by: (1) its relative small- er size; (2) its more widely spaced and therefore fewer costae on the flanks, and (3) the escutcheon only weakly ornamented by faint oblique costellae. P. (N.) stolleyi (Hill in Stoyanow, 1949, p. 88, pl. 15, figs. 9-11) from the Lower Cretaceous of Texas and Arizona, USA, is also a closely related species but differs from P. (N.) coheni, n. sp. in being: (1) comparatively shorter and wider, and (2) in having fewer flank costae. P. (N.) thoracica (Morton in Dane, 1929, p. 110, pl. 21, fig. 4) from the Cretaceous Saratoga Formation of south- western Arkansas, U.S.A., is a very closely related spe- cies, differing from P. (N.) coheni, n. sp. in having: 1) a less elongate shell shape and 2) a more densely costate flank.
Age and occurrence.—Upper Tithonian, Corongo- ceras alternans and Substeueroceras koeneni Zones, Picun Leufa Formation; Cerrito Caracoles (Locality 11), Dept. Zapala, Neuquén, Argentina.
Subgenus SCABROTRIGONIA Dietrich, 1933
Type species.— Trigonia scabra Lamarck, 1819, Up- per Cretaceous (Cenomanian), France.
Diagnosis.—Shell of medium size, crescent-shaped. Umbones prominent, with dorsal margin shallowly concave. Flank ornamented usually by tuberculated or rarely smooth costae. Area narrow, ornamented by oblique costae that form chevrons with the flank cos- tae, this being the most diagnostic feature of the sub- genus. Escutcheon depressed, wide, with transverse costellae (Dietrich, 1933, Kobayashi and Nakano, 1957, Cox, 1969, Cooper, 1989).
Distribution.—Tithonian to Maastrichtian. USA (Texas, North Carolina), México, Argentina, Europe.
Pterotrigonia (Scabrotrigonia) transatlantica (Behrendsen, 1892) Plate 7, figures 2-6
Trigonia transatlantica Behrendsen, 1892, p. 220, pl. 3, figs. 5a, b.
Scabrotrigonia transatlantica (Behrendsen). Kobayashi and Nakano, L957 pe23si
Scabrotrigonia transatlantica (Behrendsen). Levy, 1967b, p. 104.
Description.—Shell of medium size, crescent-shaped, height almost equals length. Umbones inflated and el- evated, very anteriorly situated, and highly opisthogy- rous. Dorsal margin strongly concave. Dorsoposterior angle obtuse. Posterior margin very short. Ventropos- terior angle almost 90°. Ventral margin widely convex, curving evenly into the straight anterior margin. Flank
very wide, occupying five-sixths of the shell surface, ornamented by prominent costae which in the ventral portion they bear characteristic ridges and grooves giv- ing as a result a crenulated Haidaia-like costation pat- tern. The costae exhibit in the umbonal region a con- centric direction, becoming oblique in the central flank, and subvertical in the posterior flank, with their in- terspaces widening toward the anterior and ventral margins. Area extremely narrow, ornamented by faint transverse costellae, forming a chevron-like feature when they meet the flank costae. Marginal and es- cutcheon carinae well defined especially near the umbo. Escutcheon wide, excavated and elongated, orna- mented on its whole development by sharp oblique costellae.
Material.—Twenty-seven hypotype specimens, all adult unless otherwise indicated: MOZ P2486, MOZ P2953, and MOZ P3190, well preserved right valves; MOZ P4002, anterior flank of a right valve; MOZ P3189, a complete shell, well preserved; MOZ P4400, a complete shell moderately well preserved; MOZ P4399 and MOZ P2638/4, left valves, well preserved; MOZ P4397, MOZ P2638/1, 3, 5, and 6, and MOZ P2554/5, poorly preserved left valves; MOZ P2638/ 7,8 and MOZ P3072, poorly preserved right valves; MOZ P2638/9, a fragment ofa left valve; MOZ P2638/ 1, a juvenile left valve well preserved; MOZ P2638/ 10, 12,14, juvenile left valves regularly preserved; MOZ P2638/1, 13,15, juvenile right valves, regularly pre- served; MOZ P2554/6, a juvenile complete shell, poor- ly preserved; MOZ P2638/15, a juvenile left valve mold. All specimens are fossilized in a yellowish-white, coarse-grained limestone.
Measurements (in mm).—
Specimen No.
IL, H Ww H/L W/L MOZ P2486 =31 28 10 0.90 0.32 MOZ P2953 ~28 21 12 0.75 0.42 MOZ P4399 =34 33 12 0.97 0.35 MOZ P3189 =40 35 12 0.87 0.30
Remarks.— Kobayashi and Nakano (1957, p. 231) were the first to suggest that Trigonia transatlantica Behrendsen might be a member of Scabrotrigonia Die- trich, and this view was accepted by Levy (1967b, p. 104). In Plate 7, figure 5 of the present paper it can be clearly observed that the costae of the area form a chevron-like angulosity with the flank costae. There- fore the transatlantica species of Behrendsen is as- signed to Scabrotrigonia, which is placed, according to Cox (1969), as a subgenus of Prerotrigonia van Hoepen. Although the flank bears Haidaia-like costae, their di- rections and pterotrigoniid shell shape preclude as- signment to this subgenus of Myophorella. Pterotri- gonia gerthi (Olsson, 1944, p. 42, pl. 3, figs. 4, 5, 10) from the Paita region, northern Peru, is a closely re-
TRIGONID BIVALVES OF ARGENTINA: LEANZA 61
lated species, but differs from P. (S.) transatlantica in having: 1) the area proportionally wider; 2) the flank less densely costate, and 3) the umbo less elevated. Moreover, the chevron-like feature is barely present. This report constitutes the first record of this species after the original description by Behrendsen in 1892.
Age and occurrence.—Upper Tithonian, Corongo- ceras alternans and Substeueroceras koeneni Zones, Picun Leufii Formation; Cerrito Caracoles (Locality 11), Dept. Zapala, Neuquén, Argentina.
Subgenus RINETRIGONIA van Hoepen, 1929
Type species.—Trigonia ventricosa Krauss, 1843, Lower Cretaceous, East Africa.
Diagnosis.—Shell small to large, not as elongate as Pterotrigonia; the height almost equals length. Anterior flank costae broader as in Pterotrigonia, more com- monly coarsely nodated than tuberculated, but in some species smooth. The nodes of the anterior costae be- come increasingly restricted ventrally, and connect with the area via a long thin stem. Posterior costae narrow, crowded, finely crenulated (van Hoepen, 1929, Coo- per, 1989).
Distribution.—Upper Jurassic (Tithonian) to Cre- taceous (Maastrichtian). South Africa, East Africa, South America, India, Australia, New Zealand.
Pterotrigonia (Rinetrigonia), species juvenile indeterminate Plate 9, figure 6
Description.—Shell moderately small, crescent- shaped, longer than high. Umbones inflated, highly opisthogyrous, and very anteriorly situated. Dorsal margin strongly concave. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle acute. Ventral margin slightly convex, curving evenly into the straight anterior margin. Flank very wide, or- namented anteriorly by six to eight first subconcentric, then oblique, prominent, smooth costae. Posterior flank not observable. Area very narrow, apparently smooth. Marginal and escutcheon carinae very poorly defined. Escutcheon ornament not impressed.
Material.—One juvenile specimen, MOZ P2489, a left valve with its posterior part broken, fossilized in a white-yellowish, coarse-grained, limestone.
Measurements.—
Specimen No. IE H WwW H/L W/L
MOZ P2489 11 9 5 0.70 0.25
Remarks.— Recently Cooper (1989, p. 242) claimed that if Pisotrigonia van Hoepen and Rinetrigonia van Hoepen are considered synonyms, Pisotrigonia has page priority. Kobayashi and Nakano (1957) revised for the first time the subfamily Pterotrigoniinae, and
(on pages 223 and 230) placed Pisotrigonia as a syn- onym of Rinetrigonia. According to the International Code of Zoological Nomenclature (p. 53, Article 24, Principle of the First Reviser) it can be interpreted that Kobayashi and Nakano (1957) acted as the first revis- ers, and therefore Rinetrigonia has to be retained as the valid name.
Although the described specimen can readily be as- signed to the subgenus Prerotrigonia (Rinetrigonia) on the basis of its shell shape, its juvenile nature, together with its relatively poor preservation and the shortage of material (only one specimen), precludes further tax- onomic resolution. Nevertheless, this find is important because it records the occurrence of Pterotrigonia (Ri- netrigonia) as early as the Middle Tithonian.
Age and occurrence.— Middle Tithonian, Windhau- seniceras internispinosum Zone, Picun Leufa Forma- tion; Cerro Lotena (Locality 32), Dept. Zapala, Neu- quén, Argentina.
Pterotrigonia (Rinetrigonia) coihuicoensis (Weaver, 1931) Plate 16, figures 6, 9, 11
Trigonia cothuicoensis Weaver, 1931, p. 268, pl. 27, fig. 151, pl. 28, figs. 155-160; Lambert, 1944, p. 384, pl. 7, figs. 4-7; Corvalan and Pérez, 1958, p. 40, pl. 4, figs. 3a, c.
Pterotrigonia coihuicoensis (Weaver). Freneix, 1958, p. 190.
Trigonia sp. aff. T. coihuicoensis Weaver. Corvalan, 1959, p. 32, pl. 2, fig. 9.
Myophorella (Myophorella) coihuicoensis (Weaver). Reyes and Pé- rez, 1978. p. 10, pl. 1, fig. 3; Leanza and Garate, 1987, p. 211, pl. 13, figs. 3-5.
Description.—Shell of medium size. Strongly inflat- ed anteriorly, attenuated posteriorly. Umbones prom- inent, opisthogyrous. Anterior face of the shell broad and flattened. Dorsal margin concave. Dorsoposterior angle slightly obtuse. Posterior margin very short. Ven- tral margin strongly convex, curving evenly into the almost straight anterior margin. Flank occupying five- sixths of the shell surface. Anterior and central flank ornamented by approximately 15 strong, subconcen- tric costae, which bear small but sharp tubercles. Pos- terior flank ornamented by approximately, beaded, re- troverse costae. Marginal carina beaded over its whole length. Area narrow, ornamented by transverse cos- tellae, asymmetrically divided by a submedian sulcus. Escutcheon well defined, ovate, narrow, ornamented by concentric growth lines.
Material.—Two hypotype adult specimens, MOZ P3018 (Bajada del Agrio), complete, very well pre- served shell, and MOZ P5313 (Cerro Mesa, Covunco), consisting of a fragment of a left valve.
Measurements (in mm).—
Specimen No. I H WwW H/L W/L
MOZ P5313 39 31 16 0.79 0.41
62 BULLETIN 343
Remarks.—It is difficult to determine whether the species coihuicoensis of Weaver (1931) belongs to My- ophorella or Pterotrigonia. Following Japanese authors (see Levy, 1966), this species was assigned for several years to Myophorella (Myophorella). Only Freneix (1958) (and a mention by Reyes and Pérez (1983, p. 63)) assigned the species to Pterotrigonia. Thanks to the recent revision of the Pterotrigoniinae by Cooper (1989), however, and his redefinition of several genera and subgenera of the family, the present author be- lieves that Weaver’s species, characterized by a very inflated, anteriorly flattened, being almost as high as long, and a posteriorly attenuate shell, can be better assigned to Pterotrigonia (Rinetrigonia) van Hoepen than to Myophorella Bayle. The suggestion of Kobay- ashi and Tamura (1955, p. 100) that the species coi- huicoensis might be considered as a member of Hai- daia Crickmay (1930b, emend. Kobayashi and Tamura, 1955) cannot be accepted, because the characteristic vertical crenulations that are present in the ventral part of the costae in Haidaia have not been observed in this species, and the shell shape is more related to Pterotrigoniinae.
Age and occurrence.—Lower to Upper Hauterivian, Lyticoceras pseudoregale, Holcoptychites neuquensis and Crioceratites (Paracrioceras) andinus Zones, Agrio Formation; Bajada del Agrio (Locality 5), Dept. Pe- huenches, and Cerro Mesa, Covunco (Locality 8), Dept. Zapala, Neuquén, Argentina.
Pterotrigonia (Rinetrigonia) windhauseniana (Wilckens, 1921) Plate 17, figures 6, 11-13
Trigonia windhauseniana Wilckens, 1921, p. 12; Petersen, 1946, p. 124, pl. 6, fig. 1.
Trigonia sp. Wichmann, 1927, p. 338.
Trigonia wilckensi Feruglio, 1936, p. 109, pl. 12, figs. 11, 12, pl. 21, figs: Wie2:
Pterotrigonia (Rinetrigonia) windhauseniana (Wilckens). Levy, 1967b, p. 103; Camacho, 1967, p. 132, pl. 1, fig. 2; Mancenido and Dam- borenea, 1984, p. 447, pl. 66, fig. 7; Farinati, Quattrocchio and Labudia, 1987, p. 157, pl. 1, fig. 1; Leanza and Casadio, 1991, pl. 1, figs. 9-12.
Description.—Shell small to medium size, crescent- shaped, almost as high as long. Umbones elevated, strongly opisthogyrous, and very anteriorly situated. Anterior part of the shell inflated and posteriorly com- pressed. Dorsal margin strongly concave. Dorsopos- terior angle obtuse. Posterior margin very short. Ven- troposterior angle obtuse. Ventral margin slightly convex, curving evenly into the straight anterior mar- gin. Flank occupying four-fifths of the shell surface, ornamented on its anterior part by 12-14 prominent and widely spaced, at first oblique and then subradial costae, which bear rounded tubercles. In some speci- mens the tubercles near the shell margin become closer
to each other and concentrically elongated, showing a typical gerontic growth stage. The posterior set 1s con- stituted by six to eight beaded, narrowly spaced, sub- vertical costae. In the ventral part of the flank the costae are crossed by sharp concentric growth lines. Area extremely narrow, ornamented on the umbonal region by faint transverse costellae, subsequently smooth. Marginal and escutcheon carinae poorly de- fined, except near umbo. Escutcheon wide, highly ex- cavated, ornamented in its proximal region by faint oblique costellae.
Material.—Three hypotype specimens: MOZ P2317/ 1, an adult relatively well preserved left valve with its posterior part broken; MOZ P2317/2, a well preserved right valve with its posterior part broken; MOZ P2317/ 3, a juvenile, well preserved left valve.
Measurements (in mm).—
Specimen No. L H WwW H/L W/L
MOZ P2317/1 48 38.5 13 0.80 0.27 MOZ P2317/2 =55 54 24 0.98 0.43 MOZ P2317/3 32 25 - 0.78 -
Remarks.—Pterotrigonia (Rinetrigonia) windhau- seniana (Wilckens, 1921) is a very common species in the Maastrichtian of Argentina, and has also been found in the provinces of Chubut, Rio Negro, Neuquén and La Pampa. P. (R.) windhauseniana (Wilckens) shows close affinities to P. (P.) feruglioi (Pianitzky, 1938, p. 75, pl. 1, figs. 5-6) from the Albian of Santa Cruz Province, with P. (P.) bustamantina (Feruglio, 1936, p. 196, pl. 21, figs. 3-4) from the Mastrichtian Bahia Bustamante Member of the Salamanca Formation in the Tetas de Pineda area, eastern Chubut Province, and with P. (P.) capricornia (Skwarko, 1963, p. 21, pl. 2, figs. 2-8) from the Neocomian of the Northern Ter- ritory, Australia. The described specimens differ from these species, however, in having a slightly different shell shape and flank ornamentation pattern.
Age and occurrence.—Maastrichtian, Eubaculites argentinicus Zone, Jagiiel Formation; Cerro Villegas (Locality 27), Dept. Anelo, Neuquén, Argentina.
Subfamily LAEVITRIGONIINAE Saveliev, 1958 Genus QUOIECCHIA Crickmay, 1930a
Type species.— Quoiecchia aliciae Crickmay, 1930a, Hauterivian/Barremian, British Columbia, Canada.
Diagnosis.—Rather small, oval, higher than long, without differentiated area or escutcheon. Flank or- namented by broad, rounded, radial folds, crossed by concentric grooves, present until mid-growth, where they are replaced by concentric folds (Crickmay, 1930a, Cox, 1969, Poulton, 1979).
Distribution.— Lower Cretaceous (Hauterivian/Bar-
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 63
remian). North America (Canada) and South America (Argentina).
Quoiecchia sigeli Leanza and Garate, 1987 Plate 17, figure 3
Quoiecchia sigeli Leanza and Garate, 1987, p. 226, pl. 8, figs. 4-7.
Description.—Shell of medium size, subtrigonal, al- most as wide as high, inflated. Dorsal and posterior margin almost conforming a continuous line. Ventro- posterior angle slightly acute. Ventral margin short and convex, curving abruptly into the straight anterior margin. Flank ornamented by subconcentric rugae bounded by parallel narrow grooves, and crossed in its posterior part by some radial folds. Area ornamented near the umbo by seven to eight transverse faint cos- tellae, and on the remaining surface by oblique striae arising from the flank. Marginal carina poorly defined in the umbonal region, becoming more indistinct to- ward the margin, where it is difficult to demarcate the boundary between area and flank. Escutcheon not 1m- pressed. Ligamental fossette well defined, ovate and short.
Material.—Seven adult specimens: MOZ P1610/2, acomplete shell with both valves well preserved; MOZ P1610/5, a poorly preserved right valve; MOZ P1610/ 6, a complete shell with both valves well preserved; MOZ P1610/7, a complete shell with both valves well preserved; MOZ P1610/8, a complete shell with the right valve broken; MOZ P1610/9, a well preserved right valve; MOZ P1610/10, a large complete shell, with the umbonal region broken.
Measurements (in mm).—
Specimen No. L H W H/L W/L MOZ P1610/10 50 51 15 1.02 0.30
Remarks.—This genus has been considered valid by Poulton (1977, p. 11), as a derivative of Myophorel- linae through a simplification of the ornamentation and changes in the shape and size of the shell. Saveliev (1958, p. 113) included Quoiecchia in his Laevitrigo- niinae based on the presence of subconcentric costa- tion, although this family includes forms very distantly related. Tashiro (1979, p. 211) considered Quoiecchia questionably as a member of his subfamily Apiotri- goniinae, and stated that the posterior series of costae are more closely related to those of Apiotrigonia s.s. or Heterotrigonia s.s. than to the costation of My- ophorella and Laevitrigonia. In the absence of newer evidence, however, I assign Quoiecchia to the Laevi- trigoniinae Saveliev, as I did in 1987.
Quoiecchia sigeli Leanza and Garate differs from the type species Q. aliciae Crickmay (1930a, p. 51, pl. 13, figs. 3-8) from the Hauterivian—Barremian of British Columbia, Canada, in having the area ornamented with
faint transverse costellae in the umbonal region, flanks ornamented by weaker subconcentric plicae, and a less dorsoventral elongation. The genus Quoiecchia as fig- ured by Tashiro (1979, p. 216, text-fig. 18) is very close in morphology to the Argentine species.
Age and occurrence.—Lower Hauterivian, Lytico- ceras pseudoregale Zone, Agrio Formation; Pichaihue Abajo, (Locality 3), Dept. Loncopué, Neuquén, Ar- gentina.
Subfamily AUSTROTRIGONIINAE Skwarko, 1963 Genus AUSTROTRIGONIA Skwarko, 1963
Type species. — Austrotrigonia prima Skwarko, 1963, Neocomian, Australia.
Diagnosis.—Shell very inequilateral, broad and gen- erally rounded anteriorly, produced and attenuated posteriorly. Umbones slightly opisthogyrous. Flank concentrically costate. Antecarinal sulcus very wide, flat, striated with irregular continuations of the flank costae. Area very narrow, with no obvious radial lin- eations. Sulcus, area and escutcheon ornamented with growth lines only (Skwarko, 1963, p. 33).
Distribution.—Cretaceous (Neocomian, Maastrich- tian). Australia, Antarctica ?, and South America (Ar- gentina).
Austrotrigonia pampeana Leanza and Casadio, 1991 Plate 17, figures 4, 5
Austrotrigonia pampeana Leanza and Casadio, 1991, pl. 1, figs. 4-8
Description.—Shell of medium size, trigonal, strong- ly inequilateral, posteriorly elongate. Umbones not el- evated, opisthogyrous, very anteriorly situated. The maximum inflation is situated in the central flank, de- creasing gradually toward the ventral and posterior region of the shell. Dorsal margin slightly concave. Dorsoposterior angle obtuse. Posterior margin very short. Ventroposterior angle acute. Ventral margin widely convex, curving evenly into the slightly convex anterior margin. Flank occupying four-fifths of the shell surface, ornamented by subconcentric costae and a wide sulcus characteristic for the genus. The costae, present in number of 10-12, are wide and convex in transverse section, and the intercostal spaces are equivalent to one-fourth of their thickness. The sulcus is triangular in shape, wide and shallow, widening gradually from the umbo toward the posteroventral region of the shell, and is ornamented by striae which are the continuation of the flank costae. Marginal carina undefined, es- pecially on the central and distal portion of the shell. Area excavated, narrow and smooth, ornamented by growth lines only. A barely identifiable submedian sul- cus is present in the umbonal region. Escutcheon very narrow, smooth and slightly concave.
64 BULLETIN 343
Material.—Two adult specimens: GHUNLPam 400 (the holotype, see Leanza and Casadio, 1991), com- plete, with both valves well preserved (Barda Baya); GHUNLPam 625, complete but poorly preserved (Sal- itral de La Amarga). The specimens are fossilized in a yellowish-white, fine grained limestone.
Measurements (in mm).—
Specimen No. 1G H WwW H/L W/L GHUNLPam 400 48 37 10 0.77 0.20 GHUNLPam 625 51 37 10 0.72 0.19
Remarks.—Austrotrigonia pampeana Leanza and Casadio differs from A. prima Skwarko (1963, p. 33, pl. 6, figs. 1-3 and ? 4) from the Neocomian of Queens- land, Australia, by its comparatively smaller size, less elongate shell shape, and less convex anterior margin of the shell. 4. secunda Skwarko (1968, p. 177. pl. 13, figs. 1-6) has a different shell shape, being compara- tively more inflated anteriorly, and more elongated posteriorly. Nototrigonia oliveroi (Medina, 1980, p. 109, pl. 4, fig. 1; pl. 6, figs. 2, 4) from the Campanian of James Ross Island, Antarctica, originally placed by its author in the genus Austrotrigonia, exhibits in the area some radial costae which invalidate any comparison with A. pampeana.
Age and occurrence.—Maastrichtian, Eubaculites argentinicus Zone, Jagiiel Formation; Barda Baya (Lo- cality 41) and Salitral de La Amarga (Locality 42), Dept. Puelén, La Pampa, Argentina.
Subfamily NOTOTRIGONIINAE Skwarko, 1963 Genus PACITRIGONIA Marwick, 1932
Type species.—Pacitrigonia sylvesteri Marwick, 1932, Maastrichtian, New Zealand.
Diagnosis.—Oblong, rather elongated, strongly in- equilateral shell shape. Umbo broadly rounded, pro- truding slightly. Flank with broad, smooth, sometimes depressed antecarinal space (or sulcus), but otherwise ornamented with broad, irregular undulations which may be broken up into elongated pustules, and are oblique in early growth stages but almost concentric near the ventral margin. Area smooth or with radial costellae that fade away in late growth stages, and are absent in younger species of the genus. Marginal and escutcheon carinae poorly defined, except in early growth stages. Escutcheon barely impressed (Marwick, 1932: Cox, 1952, 1969; Nakano, 1961; Fleming, 1987).
Distribution.—Upper Cretaceous (Campanian and Maastrichtian). South America (Argentina, Chile), New Zealand.
Pacitrigonia sobrali Leanza and Casadio, 1991 Plate 17, figures 1, 2
Pacitrigonia sobrali Leanza and Casadio, 1991, pl. 1, figs. 1-3.
Description.—Shell medium to large in size, inequi- lateral, longer than high. Umbones opisthogyrous, very anteriorly situated. Dorsal margin slightly concave near the umbo, then straight. Dorsoposterior angle obtuse. Posterior margin relatively long. Ventroposterior angle acute. Ventral margin slightly convex, curving strongly into the slightly convex anterior margin. Flank occu- pying three-fourths of the shell surface, ornamented by 18-20 subconcentric, somewhat sinuous costae that show a wavy character in the posterior flank. Appear- ing at the same time are elongate pustules typical of the genus. Shallow and narrow antecarinal sulcus pres- ent, ornamented only by faint growth lines. Marginal carina present in the umbonal region, then undefined. Area relatively narrow, ornamented by barely observ- able faint radial costellae, which become obsolete in the distal portion. Escutcheon not well impressed, or- namented with growth lines only.
Material.—Two adult specimens: GHUNLPam 399 (the holotype, see Leanza and Casadio, 1991), a com- plete shell, with both valves well preserved; and GHUNLPam 624, complete shell, but with both valves poorly preserved. The specimens are fossilized in a yellowish-brown, fine-grained, calcareous sandstone.
Measurements (in mm).—
Specimen No. 1S H Ww H/L W/L
GHUNLPam 399 62 42 11 0.67 0.26
Remarks.—Pacitrigonia sobrali Leanza and Casadio (1991) shows close affinities with P. hanetiana (d’Or- bigny, 1842) from the Maastrichtian of Isla Quiriquina, Chile (see Skwarko, 1963, text-fig. 5; Perez and Reyes, 1978, pl. 2, figs. 4 and 6; Fleming, 1987, text-fig. 12), but the Argentine species differs in having: (1) a lesser shell inflation; (2) a different shell shape; (3) antecarinal sulcus shallower and narrower, and (4) presence of elongate pustules in a more distal position on the pos- terior flank. Pacitrigonia patagonica (Feruglio, 1936, p. 271, fig. 2; pl. 21, fig. 5) from the Maastrichtian Lefipan Formation in the middle course of the Chubut river, Argentina, differs from P. sobrali in having: (1) a longer shell; (2), presence of pustules in the anterior flank; (3) the flank costae are more developed and el- evated: and (4) the ventral part of the flank is orna- mented by costae parallel to the ventral margin. Pa- citrigonia alamensis Levy (1985, p. 59, pl. 1, figs. 4— 6) from the Lower Campanian Puesto El Alamo For- mation in southern Santa Cruz Province, Argentina, clearly differs from P. sobrali in having: (1) the inter- section of the anterior and ventral margins forming a very sharp angulation; (2) a deeper antecarinal sulcus, and (3) a lesser density of flank costae. With regard to the different species assigned to Pacitrigonia by Flem- ing (1987, p. 46) the differences are still greater.
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 65
Age and occurrence.—Maastrichtian, Eubaculites argentinicus Zone, Jagiiel Formation; Barda Baya (Lo- cality 41), Dept. Puelén, La Pampa, Argentina.
APPENDIX.
FosstIL LOCALITIES OF THE DESCRIBED TAXA AND ASSOCIATED FAUNAS.
Locality 1.—Cerro Pitrén, Dept. Norquin (37°30’'S, 70°16'W). Steinmanella (Transitrigonia) transitoria (Steinmann) in association with Olcostephanus ath- erstoni (Sharpe), Karaskachiceras attenuatum (Beh- rendsen), Pseudofavrella angulatiformis (Behrendsen), Sarasinella, sp., Eriphyla argentina Burckhardt, Pty- chomya koeneni Behrendsen, and Myoconcha tran- satlantica Burckhardt. Agrio Formation. Late Valan- ginian/Early Hauterivian.
Locality 2.—Puerta Curaco, Dept. Pehuenches (37°30'S, 70°02'W). Steinmanella (Transitrigonia) steinmanni (Philippi) in association with Olcostephan- us atherstoni (Sharpe), Lissonia riveroi (Gerth), Mer- etrix quintucoensis Weaver, and Exogyra couloni (Defrance). Mulichinco Formation. Valanginian.
Locality 3.—Pichaihue Abajo, Dept. Loncopué (37°45'S, 70°14’W). Quoiecchia sigeli Leanza and Gar- ate and Syrotrigonia brocardoi, n. sp. in association with Pseudofavrella garatei Leanza and Leanza, Pseu- dofavrella angulatiformis (Behrendsen), Lyticoceras pseudoregale (Burckhardt), and Steinmanella (Tran- sitrigonia) transitoria (Steinmann). Lowermost part of the Agrio Formation. Lower Hauterivian.
Locality 4.—Cerrito de la Ventana, Trahuncura, Dept. Loncopué (38°00’S, 70°10’'W). Steinmanella (Transitrigonia) quintucoensis (Weaver) and Stein- manella (Splenditrigonia) splendida (A. F. Leanza) in association with Lissonia riveroi (Lisson), Acantholis- sonia gerthi (Weaver), Valanginites argentinicus Lean- za and Wiedmann, Meretrix quintucoensis Weaver, and Exogyra couloni (Defrance). Uppermost part of the Vaca Muerta Formation. Upper Berriasian/Early Va- langinian.
Locality 5.—Bajada del Agrio, Dept. Picunches (38°28’'S, 70°00'W). Pterotrigonia (Rinetrigonia) coi- huicoensis (Weaver) in association with Holcoptychites neuquensis (Douvillé), Crioceratites (Paracrioceras) andinus (Gerth), Ptychomya koeneni Behrendsen, Er- iphyla argentina Burckhardt, Myoconcha transatlan- tica Burckhardt. Upper Member of the Agrio For- mation. Middle and Upper Hauterivian.
Locality 6.—Bajada Vieja, Dept. Picunches (38°29’S, 70°05'W). Steinmanella, sp. indet. (in Leanza and Gar- ate, 1987, Pl. 6, fig. 2) in association with Argentini- ceras noduliferum (Steuer), Trigonia carinata Agassiz, and Steinmanella (T.) transitoria. Upper part of the Vaca Muerta Formation. Berriasian.
Locality 7.—Mallin Quemado, Dept. Picunches (38°33'S, 70°05'W). Virgotrigonia hugoi (Leanza), Steinmanella (Transitrigonia) neuquensis (Burck- hardt), Antutrigonia opistolophophora (Lambert), and Pterotrigonia (Pterotrigonia) aliformis (Parkinson) in association with Spiticeras (Kilianiceras) fraternum A. F. Leanza, Argentiniceras noduliferum (Steuer), Cuy- aniceras, sp., Anditrigonia (A.) eximia (Philippi), Tri- gonia carinata Agassiz, Steinmanella (Transitrigonia) transitoria (Steinmann), Steinmanella (Splenditrigo- nia) splendida (A. F. Leanza), Cucullaea mendozana Weaver, and Arca keideli Weaver. Vaca Muerta For- mation. Lower Berriasian to Early Valanginian.
Locality 8.—Cerro Mesa, Covunco, Dept. Zapala (38°44'S, 69°55'W). Trigonia aliexpandita Leanza and Garate, 7. carinata Agassiz, Myophorella (Promy- ophorella) garatei Leanza, Pterotrigonia (Rinetrigonia) coihuicoensis (Weaver), M. (Haidaia) volkheimeri Leanza and Garate, Steinmanella (Transitrigonia) rai- mondii (Lisson), S. (T.) neuquensis (Burckhardt), S. (Macrotrigonia) vacaensis (Weaver), and Rutitrigonia kauffmani, n. sp. in association with Pseudofavrella angulatiformis (Behrendsen), Acanthodiscus vaceki (Neumayr and Uhlig), Lyticoceras pseudoregale (Burckhardt), Holcoptychites neuquensis (Douville), Cucullaea gabrielis Leymerie, Pholadomya gigantea Sowerby, Pholadomya agrioensis Weaver, Ptychomya koeneni Behrendsen, Panopea neocomiensis (Leymer- ie), Astarte elongata d’Orbigny, Pecten vacaensis Weaver, Gervillia anceps Deshayes, Pinna robinaldina d’Orbigny, Gervillaria alaeformis (Sowerby), Nodomy- tilus trigonimimus Kauffman and Leanza, Tylostoma jaworskii Weaver, Natica cf. N. bulimoides (Deshayes), Cerithium cf. C. heeri Pictet and Renevier, Turritella aff. T. lineolata Roemer, and Actaeon andinus Haupt. Agrio Formation. Lower and Middle Hauterivian.
Locality 9.—Cerro Negro, Covunco, Dept. Zapala (38°46'S. 69°59'W). Trigonia angustecostata Behrend- sen, and 7. wiedmanni Leanza and Garate in associ- ation with Acanthodiscus, sp., Pseudofavrella angula- tiformis (Behrendsen), Lyticoceras pseudoregale (Burckhardt), Holcoptychites neuquensis (Douvillé), Trigonia carinata Agassiz, Steinmanella (Transitri- gonia) transitoria (Steinmann), Steinmanella (Macro- trigonia) vacaensis (Weaver), Pterotrigonia (Rinetri- gonia) coihuicoensis (Weaver), M. (Promyophorella) garatei Leanza, Cucullaea gabrielis Leymerie, Phola- domya gigantea Sowerby, Eriphyla argentina Burck- hardt, Myoconcha transatlantica Burckhardt, Gervillia anceps Deshayes, Ptychomya koeneni Behrendsen, Panopea sp, Astarte sp., Pecten sp., Tylostoma jawor- skii Weaver, Natica cf. N. bulimoides (Deshayes), Py- gaster gerthi Weaver, and Serpula antiquata Sowerby. Agrio Formation. Lower and Middle Hauterivian.
Locality 10.—Covunco Pavia, Dept. Zapala (38°49’S,
66 BULLETIN 343
70°09'W). Andivaugonia covuncoensis (Lambert). No associated fauna has been recorded. Lajas Formation. Early Bajocian to Middle Bathonian.
Locality 11.—Cerrito Caracoles, Dept. Zapala (38°49'S, 70°09'W). Trigonia carinata Agassiz, Ptero- trigonia (Scabrotrigonia) transatlantica (Behrendsen), Myophorella (Haidaia) elguetai, n. sp., and Rutitri- gonia, sp. juv. indet. in association with Corongoceras lotenoense Spath, Subdichotomoceras araucanense Leanza, Volanoceras, n. sp., Aspidoceras haupti Krantz, Anditrigonia (A.) eximia (Philippi), 4. (4.) lamberti Levy, Steinmanella (Splenditrigonia) erycina (Philip- pi), Ostrea lotenoensis Weaver, Ostrea minos Co- quand, Exogyra couloni (Defrance). Picin Leufu For- mation. Middle/Upper Tithonian.
Locality 12.—Los Catutos, Dept. Zapala (38°51’S, 70°12'W). Anditrigonia (A.) lamberti Levy in associa- tion with Aulacosphinctes proximus (Steuer), Wind- hauseniceras internispinosum (Krantz), Djurjuriceras catutosense Leanza and Zeiss, Zapalia fascipartita Leanza and Zeiss, and Lucina, sp. indet. Vaca Muerta Formation. Los Catutos Member. Middle Tithonian.
Locality 13.—Laguna Blanca, Dept. Zapala (39°04’S, 70°20'W). Trigonia, sp. juv. indet. in association with Anditrigonia (A.) eximia (Philippi), Trigonia carinata Agassiz, and Corongoceras sp. Picun Leuft Formation. Upper Tithonian. ie
Locality 14.—Estancia Marichelar, Arroyo Nireco, Dept. Catan Lil (39°02'S, 70°33'W). Frenguelliella tap- iai (Lambert) and Frenguelliella poultoni, n. sp. in as- sociation with Ctenostreon paucicostatum Leanza, Camptochlamys sp., Chlamys (Chlamys) textoria (Schlotheim), Weyla alata (von Buch), Entolium aff. E. disciformis (Schuebler), Entolium sp., Gryphaea sp., Neocrassina aureliae (Feruglio), Pholadomya sp., Lith- otrochus humboldti von Buch, Rhynchonellidae sp. in- det, and a number of ammonites of Pliensbachian age. Chachil Formation. Pliensbachian.
Locality 15.—Los Pozones, Dept. Zapala (39°10’S, 70°04'W). Trigonia corderoi Lambert, T. mollesensis Lambert, 7. /osadai, n. sp., Scaphorella leanzai (Lam- bert), Anditrigonia (Eoanditrigonia) keideli (Weaver), and Andivaugonia radixscripta (Lambert) in associa- tion with Trigonia densestriata Behrendsen, Vaugonia chunumayensis (Jaworski), Modiolus contortus Gottsche, Lucina sp., Protocardia striatula (Philippi), Lima laeviscula Sowerby, Myoconcha sp., Eriphyla sp., Nerinea cf. N. decorata Piette, Natica sp., Trochus sp., Pleurotomaria leufuensis Weaver, Bulla sp., Sonninia (Papilliceras) espinazitensis (Tornquist), Emileia mul- tiformis (Gottsche), Montlivaltia delabechei andina Gerth, Montlivaltia victoriae (Duncan), and Convex- astrea weaveri Gerth. Lajas Formation. Early Bajocian to Middle Bathonian.
Locality 16.—Barda Negra Sur, Dept. Zapala
(39°10'S, 69°57'W). Trigonia corderoi Lambert, T. densestriata Behrendsen, Neuquenitrigonia huenickeni (Leanza and Garate), Scaphotrigonia rierafonti Leanza and Garate, Myophorella (Promyophorella) praesca- broidea (Jaworski), Myophorella (Myophorella) argen- tinica (Jaworski), Vaugonia chunumayensis (Jaworsk1), Vaugonia rectangularis (Gottsche), Vaugonia, sp. 1n- det., Frenguelliella perezreyesi, n. sp., and Groeberella, sp. indet. in association with Sonninia (Papilliceras) espinazitensis (Tornquist), Emileia multiformis (Gottsche), Pseudotoites sphaeroceroides (Tornquist), Gervillia leufuensis Weaver, Pholadomya sp., Pleuro- mya sp., Goniomya sp. and Lucina sp. Lajas Forma- tion. Early Bajocian.
Locality 17.—Picun Leufi creek and Route 40, Dept. Zapala (39°14'S, 70°11'W). Antutrigonia groeberi (Weaver) in association with Substeueroceras sp., Co- rongoceras sp., Trigonia carinata Agassiz, Steinma- nella (Splenditrigonia) haupti (Lambert), Pholadomya agrioensis Weaver, Pholadomya sanctaecrucis Pictet and Campiche, Lucina neuquensis Haupt, and Sole- mya neocomiensis (Haupt). Picun Leufa Formation. Upper Tithonian.
Locality 18.—Cerro Negro Chico de Pictn Leufu, Dept. Catan Lil (39°16'S, 70°01'W). Rutitrigonia agrioensis (Weaver) in association with Steinmanella (Transitrigonia) transitoria, Myoconcha transatlantica Burckhardt, Pinna robinaldina @’ Orbigny, Eriphyla ar- gentina Burckhardt, Ptychomya koeneni Behrendsen, Panopea dupiniana @Orbigny, and Pholadomya gi- gantea Sowerby. Agrio Formation. Lower Hauterivi- an. Locality 19.—Aguada del Overo, Dept. Catan Lil (39°19'S, 70°11'W). Steinmanella (Splenditrigonia) haupti (Lambert) and Anditrigonia (Anditrigonia) ex- imia (Philippi) in association with Substeueroceras sp., Trigonia carinata Agassiz, Steinmanella (Splenditri- gonia) erycina (Philippi), Panopea dupiniana @’Orbig- ny, Lucina neuquensis Haupt, Lucina leufuensis Weav- er, Exogyra couloni (Defrance), Astarte elongata d’Orbigny, Pholadomya sanctaecrucis Pictet and Cam- piche, Pholadomya agrioensis Weaver, Grammatodon securis Leymerie, Cyprina ? argentina Behrendsen, So- lemya neocomiensis (Haupt), Isocardia koeneni Beh- rendsen, Jsognomon ricordeanus d’Orbigny, Anomya sp., and Pleuromya sp. Pican Leufi Formation. Upper Tithonian.
Locality 20.—Canad6n del Sapo, Dept. Catan Lil (39°18'S, 70°15'W). Antutrigonia frenguellii (Marine- larena) and Anditrigonia (A.) carrincurensis (A. F.Leanza) in association with Subdichotomoceras sp.,
Parapallasiceras sp. Anditrigonia (A.) eximia (Philip- |
pi), Steinmanella (Splenditrigonia) haupti (Lambert), Steinmanella (Splenditrigonia) erycina (Philippi), Tri- gonia carinata Agassiz, Lucina neuquensis Haupt, Lu-
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 67
cina leufuensis Weaver, Panopea dupiniana d@’Orbigny, and Pholadomya gigantea Sowerby. Picun Leufu For- mation. Middle Tithonian.
Locality 21.—Maquina Cura, Chacaico, Dept. Catan Lil (39°20'S, 70°22'W). Andivaugonia radixscripta (Lambert), Scaphorella camachoi, n. sp., Andivaugonia fuenzalidai (Reyes and Pérez), and Myophorella (My- ophorella) argentinica (Jaworski) in association with Trigonia corderoi Lambert, Trigonia mollesensis Lam- bert, (Lambert), Scaphorella leanzai (Lambert), Sca- Dhorella kruusei Leanza and Garate, Vaugonia chun- umayensis (Jaworski), Modiolus contortus Gottsche, Arcomya elongata d’Orbigny, Isognomon americanus (Forbes), Gervillaria leufuensis (Weaver), Chlamys sp., Amussium sp., Natica aff.N. catanlilensis Weaver, Ner- inea sp., Montlivaltia delabechei andina Gerth. Lajas Formation. Early Bajocian.
Locality 22.—Caichigiie, Charahuilla, Dept. Catan Lil (39°26'S, 70°21'W). Steinmanella (Splenditrigonia) erycina (Philippi) in association with Substeueroceras sp., Anditrigonia (A.) carrincurensis (A. F. Leanza), Anditrigonia (A.) lamberti Levy, Anditrigonia (A.) ex- imia (Philippi), Antutrigonia frenguellii (Marinelar- ena), Antutrigonia groeberi (Weaver), Steinmanella (Splenditrigonia) haupti (Lambert), Lucina neuquensis Haupt, Pholadomya gigantea Sowerby, Lucina leu- fuensis Weaver, Panopea dupiniana d’Orbigny, My- oconcha transatlantica Burckhardt, Ostrea minos Co- quand, Ostrea lotenoensis Weaver, and Exogyra couloni (Defrance). Picun Leuft Formation. Upper Tithonian.
Locality 23.—Fortin 1° de Mayo, Dept. Catan Lil (39°25'S, 70°38'W). Scaphorella kruusei Leanza and Garate and Andivaugonia lissocostata (Reyes and Pé- rez) in association with Trigonia corderoi Lambert, T. mollesensis Lambert, and Sonninia (Papilliceras) es- pinazitensis (Tornquist). Lajas Formation. Early Ba- jocian.
Locality 24.—Cerrito Roth, Canadon de la Piedra Pintada, Dept. Collon Cura (40°07’S, 70°16'W). Ja- worskiella burckhardti (Jaworski), Myophorella (My- ophorella) catenifera (Hupé), and Groeberella neu- quensis (Groeber) in association with Myophorella(M.) araucana (A. F. Leanza), Frenguelliella inexspectata (Jaworski), Weyla bodenbenderi (Behrendsen), My- ochoncha neuquena A. F. Leanza, M. neuquena torulosa A. F. Leanza, Cardinia andium (Giebel), C. cf. C. an- dium (Giebel), C. densestriata Jaworski, Entolium dis- ciformis (Schuebler), Cucullaea jaworskii A. F. Leanza, C. rothi A. F. Leanza. Isognomom jupiter (A. F. Lean- za), Gervillaria pallas (A. F. Leanza), Gervillia? turgida A. F. Leanza, Lopha longistriata (Jaworski), and Gry- phaea darwini Forbes. Piedra Pintada Formation. Pliensbachian.
Locality 25.—Mirador del Chachil, Dept. Catan Lil (39°13'S, 70°32'W). Frenguelliella tapiai (Lambert) (in
Leanza and Garate, 1987, p. 210) in association with Chlamys (Chlamys) textoria (Schlotheim),Entolium aff. E. disciformis (Schuebler) and Neocrassina aureliae (Feruglio). Chachil Formation. Upper Pliensbachian.
Locality 26.—Cerro Granito, Dept. Zapala (39°09'S, 69°34'W). Myophorella (Myophorella) araucana (in Leanza and Garate, 1987, Pl. 1, figs. 6-7) in association with Weyla bodenbederi (Behrendsen), Cardinia cf. an- dium (Giebel), Entolium disciformis (Schuebler), and Gervilliaria pallas (A. F. Leanza). Piedra Pintada For- mation. Pliensbachian.
Locality 27.—Cerro Villegas, Dept. Pehuenches (37°35'S, 69°55'W). Pterotrigonia (Rinetrigonia) wind- hauseniana (Wilckens) in association with Eubaculites argentinicus (Weaver), Baculites sp., Pterotrigonia sp., Pacitrigonia sp., Nototrigonia sp., Ostrea clarae \her- ing, and Pecten mahuidaensis Weaver. Jagiiel For- mation. Maastrichtian.
Locality 28.— Arenal de Las Lajas, Dept. Picunches. (38°31'S, 70°22'W). Anditrigonia (A.), sp. indet in as- sociation with Steinmanella (Transitrigonia) transi- toria (Steinmann) and Pterotrigonia (Rinetrigonia) coi- huicoensis (Weaver). Agrio Formation. Middle Hauterivian.
Locality 29.—Los Hornos, Covunco Abajo, Dept. Zapala (38°43'S, 69°59'W). Steinmanella (Macrotri- gonia) vacaensis (Weaver) in association with Stein- manella (Transitrigonia) raimondii (Lisson), Ptycho- mya koeneni Behrendsen, Panopea dupiniana d’Orbigny, Eriphyla argentina Burckhardt, and My- oconcha transatlantica Burckhardt. Agrio Formation. Middle Hauterivian.
Locality 30.—Salitral de los Alazanes, Dept. Pi- cunches (38°46’S, 70°13'W). Virgotrigonia hugoi (Leanza) in association with Argentiniceras sp., Cuy- aniceras sp., Arca keideli Weaver, and Cucullaea men- dozana Weaver. Vaca Muerta Formation. Berriasian.
Locality 31.—Cerro Pancho, Bajada de La Ameri- cana, Dept. Zapala (38°48’S, 70°02’W). Anditrigonia (4.), sp. juv. indet. in association with Corongoceras mendozanum (Gerth), Lytohoplites burckhardti (Mayr- Eymar), Volanoceras, n. sp., Substeueroceras sp., Os- trea minos Coquand, Ostrea lotenoensis Weaver, An- ditrigonia (Anditrigonia) eximia (Philippi), and Tri- gonia carinata Agassiz. Picun Leufu Formation. Upper Tithonian.
Locality 32.—Cerro Lotena, Dept. Zapala (39°10’S, 69°38'W). Trigonia fortinensis Lambert and Pterotri- gonia (Rinetrigonia), sp. juv. indet. in association with Subdichotomoceras araucanense Leanza, Subdichoto- moceras windhauseni (Weaver), Windhauseniceras in- ternispinosum (Krantz), Substeueroceras sp., Coron- goceras sp., Steinmanella (Splenditrigonia) haupti (Lambert), Anditrigonia (Anditrigonia) eximia (Philip- pi), Ostrea lotenoensis Weaver, Ostrea minos Co-
68 BULLETIN 343
quand, Pholadomya sp., Lucina neuquensis Haupt, and Lucina leufuensis Weaver. Pictn Leufa’ Formation. Middle [P. (P.), sp. juv. indet.] and Upper (7. forti- nensis) Tithonian.
Locality 33.—Laguna Miranda, Dept. Zapala (38°54'S, 70°15'W). Trigonia mirandaensis Lambert and Lambertrigonia pichimoncolensis (Lambert) in as- sociation with unindentified ammonite fragments, Nu- culidae ? molds, Nerinea ? sp., a small Exogyra, sp. indet., Pectinidae (Amussium ? sp.), and fragments of Pentacrinus sp. Tordillo Formation. Kimmeridgian.
Locality 34.—Camino nuevo a Los Molles, Dept. Catan Lil. (39°13'S, 70°05’ W). Anditrigonia (A.) eximia tesselicaudata, n. ssp. and Myophorella (Myophorella) schulzi, n. sp. in association with Himalayites andinus Leanza, Corongoceras sp., Substeueroceras sp, Stein- manella (Splenditrigonia) haupti (Lambert), S. (Sp/.) erycina (Philippi), and Lucina leufuensis Weaver. Pi- cun Leufa Formation. Upper Tithonian.
Locality 35.—Cafiad6n Nancu Huau, Chacaico, Dept. Catan Lil (39°17’S, 70°17'W). Scaphorella lean- zai (Lambert) in association with Sonninia (Papilli- ceras) espinazitensis (Tornquist), Sonninia variabilis (Schlotheim), Sonninia altecostata (Tornquist), Emi- leia spp., Otoites sauzei (d’Orbigny), Trigonia molle- sensis Lambert, Natica sp., Chlamys sp., Amussium sp., Protocardia sp., Lucina sp., Pentacrinites sp., Rhynconella cf. R. tetraedra MGericke, Rhynconella cf. R. variabilis Schlotheim, Ctenostreon neuquensis (Phi- lippi), Montlivaltia delabechei andina Gerth, Cycada- ceae fragments, silicified wood, and Ichthyosauridae. Lajas Formation. Early Bajocian.
Locality 36.—Las Cortaderas, Dept. Catan Lil (39°23'S, 70°11'W). Trigonia levyi, n. sp. in association with Subdichotomoceras sp., Parapallasiceras sp., An- ditrigonia (A.) eximia (Philippi), and Exogyra couloni (Defrance). Pican Leufti Formation. Middle Tithoni- an.
Locality 37.—La Amarga, near Rincon del Aguila, Dept. Zapala (39°05’S, 69°32'W). Myophorella (My- ophorella) araucana (A. F. Leanza) in association with Cardinia andium (Giebel), Cardinia densestriata Ja- worski, Weyla alata (von Buch), and Lopha sp. Piedra Pintada Formation. Pliensbachian.
Locality 38.—Estancia Souraya, Espinazo del Zorro, Dept. Catan Lil. (39°16’S, 70°37’ W). Myophorella (My- ophorella) catenifera (Hupé) in association with “Fan- ninoceras” behrendseni (Jaworski), Chlamys (Chlam- ys) textoria (Schlotheim), Entolium aff. E. disciformis (Schuebler), Entolium sp., and Camptochlamys sp. Chachil Formation. Pliensbachian.
Locality 39.—Estancia Santa Isabel, Dept. Catan Lil (39°52’S, 70°29'W). Myophorella (Myophorella) cf. M. tuberculata (Agassiz) and Frenguelliella inexspectata (Jaworski) in association with Myophorella (Myopho- rella) araucana (A. F. Leanza), Cardinia andium (Gie- bel), Lithotrochus sp., and Rhynchonellidae indet. Piedra Pintada Formation. Pliensbachian.
Locality 40.—Carrin Cura, Dept. Collon Cura (40°01'S, 70°20’W). Jaworskiella burckhardti (Sawor- ski) (sp. juv.) in association with Frenguelliella inex- spectata (Jaworski), Cucullaea rothi A. F. Leanza, Lo- pha longistriata (Jaworski), and Gervillia ? turgida A. F. Leanza. Piedra Pintada Formation. Pliensbachian.
Locality 41.—Barda Baya, Dept. Puelén. Prov. La Pampa (36°54'S, 67°55'W). Pacitrigonia sobrali Leanza and Casadio and Austrotrigonia pampeana Leanza and Casadio in association with Eubaculites argentinicus (Weaver), Pterotrigonia (Rinetrigonia) windhausen- iana (Wilckens), Panopea inferior Wilckens, Acesta la- tens Feruglio, Veniella pampaensis (A. F. Leanza and Hiinicken), Lahillia luisa (Wilckens), Cucullaea ant- arctica (Wilckens), Nucula sp., Ostrea clarae \hering, Pecten mahuidaensis Weaver and several species of Turritella. Jagiiel Formation. Maastrichtian.
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Ym BULLETIN 343
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74
Figures POs 7 =O:
. Groeberella neuquensis (Groeber)
. Frenguelliella tapiai (Lambert) ..........
BULLETIN 343
EXPLANATION OF PLATE |
(All figures natural size, unless otherwise indicated)
Pass burckhardti (Jaworski)
, Hypotype, MOZ P3044, lateral view of left valve; 6, Hypotype, MOZ P3043, juvenile specimen, dorsal view; 7, lateral view of left valve of same specimen. Pliensbachian, Piedra Pintada Formation, Carrin Cura (Locality 40). 10, dorsal view of same specimen. Pliensbachian, Piedra Pintada Formation, Cerrito Roth, Canadon de la Piedra Pintada (Locality 24).
2, Hypotype, MOZ P4060, dorsal view; 3, lateral view of left valve of same specimen. Pliensbachian, Piedra Pintada Formation, Cerrito Roth. Canadon de la Piedra Pintada (Locality 24).
. Myophorella (Myophorella) araucana (A. F. Leanza) ......... 600.0. e eee eee reenter essen es 29
4, Hypotype, MOZ P0875, dorsal view; 5, lateral view of left valve of same specimen. Pliensbachian, Piedra Pintada Formation, La Amarga, near Rincon del Aguila (Locality 37).
8, Hypotype, MOZ P2679, a mold of left valves Upper Pliensbachian. Chachil Formation, Estancia Marichelar, Arroyo Nirec6 (Locality 14).
. Myophorella (Myophorella) cf. M. tuberculata (Agassiz) ........-- ++. +0 eee cence eee e teen enter ene 29
9, Hypotype, MOZ P2675, a mold of left valve. Pliensbachian, Piedra Pintada Formation, Estancia Santa Isabel (Locality 39).
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105 PLATE |
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
PLATE 2
Figures ily Ay Weis
3-6.
14, 17.
16, 18.
TRIGONIUD BIVALVES OF ARGENTINA: LEANZA 75
EXPLANATION OF PLATE 2
(All figures natural size, unless otherwise indicated)
JORG VANAND RTGACNAL WLIO ete aatobo de dos ben coodaHe come EE Oro on Hee Horo EmeI arene easibacesonosoHeUSS 27 1, Holotype, MOZ P3030/1, dorsal view; 2, lateral view of of right valve of same specimen (* 2). 7, Paratype, MOZ P3030/
2, dorsal view; 8, lateral view of right valve of same specimen (2). Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
TRE ANTEANA ROI TO AL TOES NEG ae ists ote n mond uSpoSe boo nope das ootands EE Aoeodos Gu cumemoodaghooncehososeodopenoear 26 3, Holotype, MOZ P5315, lateral view of right valve (in association with a broken left valve). 4, Paratype, MOZ P5317/1, lateral view of a young right valve. 5, Paratype, MOZ P5316, lateral view of right valve. 6, Paratype, MOZ P5317/2, lateral view of a mold of right valve. Upper Pliensbachian, Chachil Formation, Arroyo Nirec6 (Locality 14).
Meh rencuelliellavinexspeclalai (i AWOLSKA) ge merase ee rere yoo Saas Sted SE TES CIRO ee ee nice 26
9, Hypotype, MOZ P2766, lateral view of an internal mold of right valve. Pliensbachian, Piedra Pintada Formation, Estancia Santa Isabel (Locality 39).
ae Viyopnorella(ivophorellacatentieraiTAupe) serene eee oe nee Ee Cee ee eee 29
10, Hypotype, MOZ P2682, lateral view of left valve. Upper Pliensbachian, Chachil Formation, Estancia Souraya, Espinazo del Zorro (Locality 38). 11, Hypotype, MOZ P4525, mold of upper portion of left valve. Pliensbachian, Piedra Pintada Formation, Cerrito Roth, Canadon de la Piedra Pintada (Locality 24).
PTI LONI VION ESCNSISANEAITI DET Ua cara ca ats yageteyeoN et ge fo iarae Talis an) sV 2 sav ays ate pein teadr exe etecska whale el ere sereie Sea rote a meyreras epee eiseal aleve rein eebalereietefere 20
12, Hypotype, MOZ P0911, lateral view of left valve; 19, dorsal view of same specimen. Early Bajocian to Early Bathonian, Lajas Formation, Los Pozones (Locality 15).
ME AULONIAIKECLANLUIATISN GOttSChe) arr rn ao che okes ashe een oe eo ac Ge SaaS RTE CG cee eet ae ee eee 37
13, Hypotype, MOZ P1753, lateral view of right valve. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16). Myophorella(Myophorella)vargentinica(Jaworski))) | eeas sac cae lee ace isc e ae ase eles neice ae eee cite oie eine relates 30 14, Hypotype, MOZ P1897, lateral view of right valve. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
17, Hypotype, MOZ P4914, lateral view of left valve. Middle Bajocian, Lajas Formation, Maquina Cura, Chacaico (Locality
21).
. Vaugonia chunumayensis (Jaworski) .................-...- Ce Sek a Se oe seen Pee Bec Sore eee Ae 36
15, Hypotype, MOZ P1903, lateral view of right valve. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
PAN Gitr i SONIA (E OANAILTI SONIA) KEIGEL WWEAVEL) ents nee ane nein eee ones eee eee EE nena 47 16, Topotype, MOZ P2749/2, lateral view of a young right valve. 18, Topotype, MOZ P0902/3, lateral view of left valve. Early Bajocian to Early Bathonian, Lajas Formation, Los Pozones (Locality 15).
76
Figures i D
BULLETIN 343
EXPLANATION OF PLATE 3
(All figures natural size, unless otherwise indicated)
Page
K Scaphorella leanzai\(LamBert)) o.oo... -se/.ceco cs ;osdve.w are.c.v a seusholelalipererevstere ole aielele'shs efefeua¥s evcueit Dieiel Meiers eee oe ee 34 1, Hypotype, MOZ P0919/1, dorsal view; 2, lateral view of left valve of same specimen. Early Bajocian to Early Bathonian, Lajas Formation, Los Pozones (Locality 15).
4S Caphotnigonia rierafontiiLeanza andi Garate® <,.y,<0 sc ois sie elon sae ooo sesteis ainsi ele eee eee 34 3, Topotype, MOZ P0931, dorsal view (1.5); 4, lateral view of left valve of same specimen (x 1.5). Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
© (Myophorella\(Promyophorella)) praescabroidea\(Jaworski)) <.... 2 d0.-220 oe 2-2 Jaren eee eee eee EEE Eee 31 5, Hypotype, MOZ P0953/2, lateral view of left valve; 6, dorsal view of same specimen. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
|, Trigonia-densestriata Beherendsen 46.56.65 do qavaci ove eon Gayee Boeacio 9.0 se) TeMT sey Fe os BRIA ORE On AOE eee eee 21 7, Hypotype, MOZ P3042, lateral view of right valve; 8, dorsal view of same specimen; 9, lateral view of left valve of same specimen. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
. Neuquenitrigonia huenickeni (Leanza‘and Garate), 2222 ...5. 222s 0 on wee eon eee eee see REE cee eee 25 10, Topotype, MOZ P2319, lateral view of right valve; 17, dorsal view of same specimen. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
+ Drigonia‘corderol Lambert 2. esc 2 Seep nis dee so isis wel ae ee eee SEO Re hice EE Oe ee 19 11, Hypotype, MOZ P5235, dorsal view. Early Bajocian to Early Bathonian, Lajas Formation, Los Pozones (Locality 15).
«aS caphorellacCamachol, NEW'SPECIES.. > svaie vistas ara wrerrorace eee ais De eC ESSE EEC SESE OL eee eee 35 12, Holotype, MOZ P4920/1, lateral view of right valve (x 2). 13, Paratype, MOZ P4920/2, lateral view of left valve (<2). Early Bajocian, Lajas Formation, Maquina Cura, Chacaico (Locality 21).
; Seaphorella;kruusel Leanza:and 'Garate «02<secsa cc cieictevens vince nia e Aes GIN MOET es efaes tose ants CIO RIC Rae ee 35 14, Topotype, MOZ P1813, dorsal view; 15, lateral view of left valve of same specimen. Early Bajocian, Lajas Formation, Fortin la’a de Mayo (Locality 23).
. ‘Groeberella, species indetermimate: <3 s:6(.//.5 6 s.yac/a-t,cnsb wre eteneye e evoreis. aie ee b anaroresnyetaps foShese natty sia) BSR Eee OG 19
16, Hypotype, MOZ P1375, lateral view of left valve. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105 PLATE 3
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
PLATE 4
Figure 1, 2, 4, 10.
359:
6-8.
Wile
A IIALVAU SOMIALCOVUNCOENSISN MEAT DEI Ls miei ces aeiesteere et cre ree ee OT TE ere ee een tee
TRIGONIID BIVALVES OF ARGENTINA: LEANZA Th
EXPLANATION OF PLATE 4
(All figures natural size, unless otherwise indicated)
Page AMaLVAUSOni Gs ad Xscripta\(LamDent)ianscrcen see ee Roe oe eo EEOC ee Eee eee ee 38 1, Hypotype, MOZ P4576, lateral view of left valve. 2, Hypotype, MOZ P4574, lateral view of a fragmentary right valve. 4, Hypotype, MOZ P4572, lateral view of right valve. 10, Hypotype, MOZ P4571, lateral view of right valve. Early Bajocian, Lajas Formation, Maquina Cura, Chacaico (Locality 21). 39
3, Topotype, MOZ P0932/1, lateral view of left valve. Early Bajocian to Early Bathonian, Lajas Formation, Covunco Pavia (Locality 10).
Tir i QONIATCOVACr OU AMI DET tease ce eye TI oie ease aI Ia CITI T TOTO CESPE TAT ST OTST ee ae ee se 19 5, Hypotype, MOZ P3022, dorsal view of a young specimen; 9, lateral view of left valve of same specimen. Early Bajocian, Lajas Formation, Barda Negra Sur (Locality 16).
ANALY AUP ONIONISSOCOSIQIG\ (REY ES;aNnGUPETEZ)) ieee ae nae eee te ee Ee ee eC EEE Sane 39 6, Hypotype, MOZ P1821/1, lateral view of left valve. 7, Hypotype, MOZ P1821/2, lateral view of left valve. 8, Hypotype, MOZ P4322, lateral view of left valve. Early Bajocian, Lajas Formation, Fortin 1° de Mayo (Locality 23).
ANAIVAULONIGN UCNZANGAN (REYES ANd IREIeZ) meen ents s cant ne Eee eee ee 39 11, Hypotype, MOZ P2314, lateral view of right valve. Early Bajocian, Lajas Formation, Chacaic6 (Locality 21).
78 BULLETIN 343 EXPLANATION OF PLATE 5 (All figures natural size, unless otherwise indicated)
Figures Page I 2. Grigonia:corderormlbam bert « siceyecjae rare does ee eee eR ees Seana eerie ere Ore ee eee 19 1, Hypotype, MOZ P0910, dorsal view; 2, lateral view of left valve of same specimen. Early Bajocian to Early Bathonian, Lajas
Formation, Los Pozones (Locality 15).
34. Trigonia losadai; MEwsSPECIeS’ 2 ...ens oso eo cies dee oe ee as aera = ee eee ee Peron lacie Sloe eile eee ee ee ee 20 3, Holotype, MOZ P3017, dorsal view; 4, inten view of left Taive of same specimen. Early Bajocian to Early Bathonian, Lajas Formation, Los Pozones (Locality 15).
5516.. Lambertrigonia’ pichimonceolensis (Lambert). -ss1.eaoce toe econ conn een ce oes see he eee eee eee 54 5, Topotype, MOZ P4252/1, lateral view of night valve (x 1.5). 6, Topotype, MOZ P4252/2, lateral view of left valve (x 1.5). Kimmeridgian, Tordillo Formation, Laguna Miranda (Locality 33).
7... Ufigoniaimirandaensis Lambert <5 sejcle societal Poe ee 6 5) «80s Sats spas dele re O EEE ca ae Ore eee 21 7, Reproduction of the Holotype, SGN 41-201, figured by Lambert (1944, pl. 1, fig. 9). Kimmeridgian, Tordillo Formation, Laguna Miranda (Locality 33). 8379! Anditrizonia\(Anditrigonia):carrincurensis (A. FE: Weanza)) 0... 20.220 fs nee eee 47
8, Hypotype, MOZ P0923/1, lateral view of left valve; 9 dorsal view foheame specimen. Middle Tithonian, Picun Leuft Formation, Canadon del Sapo (Locality 20).
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105 PLATE 5
PLATE 6
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
Figures Ie2:
3, 4.
5, 8-10.
. Trigonia fortinensis Lambert
TRIGONID BIVALVES OF ARGENTINA: LEANZA 719
EXPLANATION OF PLATE 6
(All figures natural size, unless otherwise indicated)
Page SAGA (SR EO AE NDI Erle), oopn coapsebdaussoacnenOoDanodanoptebaneesonDoeno buchos coms HooUmE OE 44 1, Hypotype, MOZ P0913, dorsal view; 2, lateral view of left valve of same specimen. Upper Tithonian, Pican Leufa Formation, Aguada del Overo (Locality 19). I SOMNE IARI WORP GOTO 5 Gocap evecehooe.s code non pedoGk Pandone so Sopadan aCe Rer ane cro tudo dadundds Doub Seeee 22
3, Holotype, MOZ P5314, dorsal view; 4, lateral view of right valve of same specimen. Middle Tithonian, Picun Leufu Formation,
Las Cortaderas (Locality 36).
ELErOLriZONiai(UNOLOSCAUOLFI OMA) ICORENL NE WASPECIES ae everest otras ocae eset craic tac aes eee = oes steers asc ane eS eee ciel aehe ee ate 59 5, Holotype, MOZ P4723, lateral view of left valve. 8, Paratype, MOZ P5764, lateral view of right valve. 9, Paratype, MOZ P5765, lateral view of left valve. 10, Paratype, MOZ P3073, lateral view of left valve. Upper Tithonian, Picun Leufu Formation, Cerrito Caracoles (Locality 11).
6, Hypotype, MOZ P3006, lateral view of left valve; 7, dorsal view of same specimen. Upper Tithonian, Picun Leufti Formation, Cerro Lotena (Locality 32).
80
BULLETIN 343
EXPLANATION OF PLATE 7
(All figures natural size, unless otherwise indicated)
Figures Page
NE
2-6.
7-9.
Steinmanella (Splenditrigonia) erycina (Philippi) .........- 2.2.0.0. eee eee center eee eee eee teen e neers eres 44 1, Hypotype, MOZ P0921, lateral view of left valve. Upper Tithonian, Picun Leufa Formation, Caichigiie, Charahuilla (Locality
22).
Pterotrigonia (Scabrotrigonia) transatlantica (Behrendsen) .............--- +++ -e eee cece reer eee teen eee eee ees 60 2, Hypotype, MOZ P2486, lateral view of right valve. 3, Hypotype, MOZ P2953, lateral view of right valve. 4, Hypotype, MOZ P4399, lateral view of right valve. 5, Hypotype, MOZ P3189, dorsal view; 6, lateral view of left valve of same specimen. Upper Tithonian, Picun Leufi Formation, Cerrito Caracoles (Locality 11).
Prigonia carinata} ABassiZ, 25% 2.2). 2 em. -\ 2 ies) = eH RAPE EEE RAMEE. ol occ oso bn Acaddnaoco os ConDbODESdgoN ORO. 22 7, Hypotype, MOZ P0915, lateral view of right valve, showing the attachment of an epizoan oyster on the posterior area; 8, dorsal view of same specimen; 9, ventral view of same specimen, showing a probable byssal slit. Upper Tithonian, Picin Leufa Formation, Cerrito Caracoles (Locality 11).
PLATE 7
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
Et >
AE hs ie) ee
i
PLATE 8
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
Figures 12s
3, 4, 7, 10.
Si:
TRIGONIID BIVALVES OF ARGENTINA: LEANZA
EXPLANATION OF PLATE 8
(All figures natural size, unless otherwise indicated)
Antutrigonia frenguellii (Marifielarena) .............6 000-0 e cece eee e cn nent nen c ene n erence renee etnies
1, Topotype, MOZ P0918, lateral view the right valve; 2, dorsal view of same specimen. Late Middle Tithonian, Picun Leufa Formation, Canadon del Sapo (Locality 20).
Alntutrigonia erOeDert (WEAVER) sri sle 1s icveksis eter sperst= races eines esle alo) eYoln che la ciel see atatafewloteF ofela\ese) lel oiazelerolenelerelotel lors sVateseiarala sere
3, Topotype, MOZ P2069, dorsal view; 4, lateral view of right valve of same specimen. 7, Topotype, MOZ P0922/3, dorsal view: 10, lateral view of left valve of same specimen. Upper Tithonian, Pican Leufa Formation, Pican Leufu creek and route 40 (Locality 17).
SR TTLZOMIG RSD Ay UVepATGE ted cre eyes shoe ssn ecciehoke te Lepener st stec svar eseIS er oYare Ceo oi = 2 =e cla apes asoasinteloVexovelefe/-vetet se evens seye]=sove “lcils) oknlnratonesuslanecenets
5, Type, MOZ P5466, lateral view of right valve (x 2). Upper Tithonian, Pictin Leufa Formation, Laguna Blanca (Locality 13).
. Myophorella (Promyophorella) hillebrandti (Reyes and Pérez) ......... 26-6002 eee eee eee ete teense
6, Hypotype, MOZ P3075, lateral view of left valve (x 1.5). Middle Tithonian, Carrin Cura Formation, Fortin 1° de Mayo (Locality 23).
Myophorella (Myophorella) schulzi, new SpeCieS ...... 2... 6. o cece ene tenn ne teen eee enter e nnn tees 8, Holotype, MOZ P3075/1, dorsal view; 9, lateral view of right valve of same specimen. Upper Tithonian, Pican Leufa Formation, Camino nuevo a Los Molles (Locality 34).
81
23
82 BULLETIN 343 EXPLANATION OF PLATE 9 (All figures natural size, unless otherwise indicated) Figures 1, 2. Anditrigonia (Anditrigonia) eximia gesselie Audata: NEW SUDSPECIES) oe sie cc. ciel circa re ae eer ores estate ate eke ot tenet Roe 1, Holotype, MOZ P1901, dorsal view; 2, lateral view of right valve of same specimen. Upper Tithonian, Pican Leufu Formation, Camino nuevo a Los Molles (Locality 34). 3, 4. Anditrigonia (Anditrigonia) eximia (Philippi) .............0...0e esse eee e cece eee eee eee eens etter rns ete es 3, Hypotype, MOZ P1902/1, lateral view of left valve. 4, Hypotype, MOZ P1902/2, lateral view of left valve. Upper Tithonian, Pictin Leufti Formation, Aguada del Overo (Locality 19). 5. Anditrigonia (Anditrigonia), sp. juv. ndet. ... 2... 2 22 2 nee ee we ole ee ee ee trie ene eee ele eo mais noo ete eiene ola = 5, Type, MOZ P3014, lateral view of left valve (« 1.5). Upper Tithonian, Picin Leufi Formation, Cerro Pancho, Bajada de La Americana (Locality 31). 6. Pterotrigonia (Rinetrigonia), sp. juv. indet. ... Seco coger a eharie/eugias Goa caresd GiSvese corel s 6 Seon e rei ele ee EOE inten ice talker 6, Type, MOZ P2489, umbonal view of left valve Sn iproken specimen (x 1.5). Middle Tithonian, Picun Leufi Formation, Cerro Lotena (Locality 32). 7. Anditrigonia (Anditrigonia) lamberti Levy ............0. 0000 e cece eect een e eee cee eer e reese ser ee sects resnsserecssre: 7, Hypotype, MOZ P0914, dorsal view of both valves in butterfly position. Upper Tithonian, Picin Leufa Formation, Los Catutos (Locality 12). 8. Rutitrigonia, sp: jUuV-indet:, .fij.e- 22 sas ere 60 + oie ieee si eleere ote reel lene aoe atelier ee eee 8, Type, MOZ P5002, lateral view of left valve ( x1. 5). Upper Tithonian, Picin Leuftii Formation, Cerrito Caracoles (Locality 11). 9-11. Myophorella (Haidaia) elguetai, new SpecieS ....... 22.2.6 0c cece nnn enn t eee e eens rene net cece senses
9, Paratype, MOZ P5767, lateral view of left valve. 10, Holotype, MOZ P3067, lateral view of right valve. 11, Paratype, MOZ P2486/2, lateral view of left valve. Upper Tithonian, Picin Leuft Formation, Cerrito Caracoles (Locality 11).
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105 PLATE 9
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
a cea’ ee ed
TRIGONUD BIVALVES OF ARGENTINA: LEANZA 83
EXPLANATION OF PLATE 10 (All figures natural size, unless otherwise indicated)
Figures
5 2b SAVATAGE) OLR ERO MARGIN) a ann cceon soos Geceae CA oOEn ae onm econ coooEnecHoneroosueeeneneesadae 41 1, Hypotype, MOZ P0916, lateral view of left valve; 2, dorsal view of same specimen. Late Valanginian/Early Hauterivian, Agrio Formation, Cerro Pitrén (Locality 1).
Bersalin Oni aialiexpanditallseanZaranG Gi arate pe rerce stoke epee ee Ke sre as ce ahve thee aoe eas eae eT eee Sa Tor ee ere (oye aie SIS IEE 3, Holotype, MOZ P0951/1, lateral view of left valve; 4, dorsal view of same specimen. Lower and Middle Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality 8).
84 BULLETIN 343 EXPLANATION OF PLATE | 1 (All figures natural size, unless otherwise indicated)
Figures Page 1—4* (Steinmanella\(fransitrigonia) raimondii (Lisson)... 00+.22.e 6 6 dee 2+ se a ee eee eee eee 43 1, Hypotype, MOZ P1756/9, lateral view of left valve; 2, dorsal view of same specimen. 3, Hypotype, MOZ P1756/3, dorsal view.
4, lateral view of right valve of same specimen. Lower and Middle Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality
8). 5-8. Steinmanella(Splenditrigonia)\splendida (A. EF. Leanza)) ...... .5<<ses cede eee eee Eee 43
5, Hypotype, MOZ P2553, lateral view of left valve; 6, dorsal view of same specimen; 7, posterior view of both valves of same specimen showing the exhalant aperture matching with the outer area; 8, lateral view of right valve of same specimen showing attachment of some Lycettia sp. epizoans. Early Valanginian, Cerrito de La Ventana, Trahuncura (Locality 4).
PLATE 11
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
Figures
1s.
5; 13:
TRIGONIID BIVALVES OF ARGENTINA: LEANZA
EXPLANATION OF PLATE 12
(All figures natural size, unless otherwise indicated)
IMyophorella(bromyophorella) | garater Mean Zaye. sere rersrer rate erento te Te Fe lo tek © el ise 1 oyaiel = =) efor ole eetereneverate tere leloke ees) ai ere! aieys) ste" adete 1, Topotype, MOZ P0930/4, dorsal view; 2, lateral view of left valve of same specimen (x 1.5). 3, Topotype, MOZ P0930/6, dorsal view; 4, lateral view of right valve of same specimen (1.5). Lower and Middle Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality 8).
TOGO. GALTON ERS nee ie Ont aRS DOGEe aD Oo GOR OO6 SHDS 6 pOODO GOD e acnocn cone OOD a DORantecsasccnudcon sakes obo dooD 5, Hypotype, MOZ P5607, lateral view of right valve; 13, dorsal view of same specimen. Lower and Middle Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality 8).
MS LELNINANEI GA GULANSILVILONIA) MIEUQUEMNSIS) (UTCKTATOL) i eye rere cites ets feetate e 2fere oa) ha/ataatahote deters tele yav ees lots afetete fejetn ofelFeneialeveleionsiel*/eie's)e.+ ele
6, Hypotype, MOZ P2767, dorsal view; 7, lateral view of left valve of same specimen. Upper Berriasian, Vaca Muerta Formation, Cerrito de La Ventana, Trahuncura (Locality 4).
meMyophorellai(Haidaia)ivolkheimeriWeanzaland!Garate verre ci ccoe sce alc tere trate oe atl ede ested svt shake abated sta sPaueh severe sboveystsvare tote otelon
8, original Paratype, MOZ P1752/2, lateral view of left valve (= 1.5). 9, original Paratype, MOZ P1752/3, dorsal view; 10, lateral view of left valve of same specimen (1.5). 11, original Holotype, MOZ P1752/1, dorsal view; 12, lateral view of left valve of same specimen (1.5). Lower and Middle Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality 8).
85
22
42
86
Figures 1, 10.
2, 6-9.
3-5.
BULLETIN 343
EXPLANATION OF PLATE 13
(All figures natural size, unless otherwise indicated)
Steinmanellal (Hransitrigonia)steinmanni (Philippi) "2... + sass eee seer ee ee eee eee eee 1, Hypotype, MOZ P0917, lateral view of left valve, showing attachment of serpulid epizoans; 10, dorsal view of same specimen. Valanginian, Mulichinco Formation, Puerta Curaco (Locality 2).
Antutrigonia opistolophophoral\(ambert). «2.2.25 < « <..srac s a eisesisis felon ricieteeo a teat ee eee 2, Topotype, MOZ P0903/2, dorsal view; 6, anterior view of same specimen; 7, lateral view of left valve of same specimen. Late Berriasian/Early Valanginian, Mulichinco Formation, Mallin Quemado, Sierra de la Vaca Muerta (Locality 7). 8, reproduction of the Holotype figured by Lambert (1944, pl. 3, figs. 5-6), dorsal view, showing transverse costulation on the area characteristic
of Antutrigonia Leanza and Garate; 9, lateral view of same specimen. Same age, horizon and locality than specimen MOZ P0903/ 2
Mrigoniaangustecostata Behrendsen’ .oye.0.6. 6 s.0.0ays.5,+.550, 054 © » v.50: 24-0 1, Ble a eee een eee RECO EE Rene aaiae 3, Hypotype, MOZ P0950, lateral view of left valve; 4, dorsal view of same specimen; 5, lateral view of right valve of same specimen. Lower and Middle Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality 8).
PLATE 13
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105 PLATE 14
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 87
EXPLANATION OF PLATE 14 (All figures natural size, unless otherwise indicated)
Figures Page te sae OM Stemnmanell a (inransitrlZOnia) | QUINCUCOENSIS\ NVEAVEL) mmeciciic ee aitate rere ieie ilies ae tie alate eee el akervVateree eae NTIS eles ole © nicte 41 1, Topotype, MOZ P0925, lateral view of left valve; 2 dorsal view of same specimen. 4, Topotype MOZ P2552, lateral view of left valve; 10, lateral view of right valve of same specimen showing the attachment of three generation of Lycettia sp. epizoans. Late Berriasian/Early Valanginian, Vaca Muerta Formation, Cerrito de La Ventana, Trahuncura (Locality 4). 35 JARO goa CHOI GO ae VA oldms (ed sion)! Soocouenneneus canonodouEmaacHonsdGoaDo douuo0o0o 00S oungaoddonTeCee 58 3, Hypotype, MOZ P2687, lateral view of a mold of left valve. Berriasian, Vaca Muerta Fomation, Mallin Quemado, Sierra de la Vaca Muerta (Locality 7). SO ERO As Heh Fell 0 UE 11V7:) ees an Gant onioot tet oan ont or ESConAnOAEnAOhagscoocndouopoLonoueonmparcaqepan 53 5, Topotype, MOZ P2733/1, lateral view of left valve. 8, Topotype, MOZ P2733/4, lateral view of a broken right valve; 9, dorsal view of same specimen. Berriasian. Vaca Muerta Formation. Mallin Quemado, Sierra de la Vaca Muerta (Locality 7). 6, Hypotype, MOZ P2332/2, lateral view of left valve; 7, dorsal view of same specimen. Berriasian, Vaca Muerta Formation, Salitral de los Alazanes (Locality 30).
88 BULLETIN 343 EXPLANATION OF PLATE 15 (All figures natural size, unless otherwise indicated) Figures Page 15. Rutitrigonia Kauffmanis new SPECieS: = ei 2- jar = 2 olasefors ia «i= ere ale dete © eres = Riel eels olsislare ciel viele oi gleich) ie a ole ea 55 1, Paratype, MOZ P4295/2, lateral view of left valve (1.5). 2, Paratype MOZ P3527/3, lateral view of left valve (x 1.5). 3, Paratype, MOZ P4295/1, lateral view of right valve (1.5). 4, Holotype, MOZ P3527/2, lateral view of left valve (x 1.5). 5, Paratype. MOZ P3527/6, lateral view of right valve (x 1.5). Lower and Middle Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality 8). 6, 7. Steinmanella (Macrotrigonia) vacaensis (Weaver) ......------ 20-0 e eee eee ete eee n etter terete sees 45
6, Hypotype, MOZ P2329, dorsal view showing in the posterior area the inhalant and exhalant apertures, 7, lateral view of left valve of same specimen. Middle Hauterivian, Agrio Formation, Los Hornos, Covunco (Locality 29).
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105 PLATE 15
PLATE 16
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105
Figures
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 89
EXPLANATION OF PLATE 16
(All figures natural size, unless otherwise indicated)
SMRULIETELO NIAAA LTIOETISISI WWCAN Cl) eno rosesese sarees sieave ace TES ieee Sms oT Ree eee eee ne 54
1, Hypotype, MOZ P0920/3, lateral view of left valve; 2 dorsal view of same specimen. 3, Hypotype, MOZ P0920/1, lateral view of left valve. Lower Hauterivian, Agrio Formation, Cerro Negro Chico de Pictn Leufi (Locality 18).
Me SIV NOLLIS ONIIGNDEKOCATAOINNIE WAS DEGIES 9 create cies tere tas8 see Pt oe) Sie eee avery eo ok OCR OO ee eres odors =H
4, Paratype, MOZ P5318, dorsal view. 7, lateral view of right valve of same specimen. 10, Holotype, MOZ P5319, dorsal view; 12, lateral view of left valve of same specimen. Lower Hauterivian, Agrio Formation, Pichaihue Abajo (Locality 3).
AnairiconiaAnditrigonia) species indeterminatessss 1a ae ee ei rete niet eek tee eetsiay eee ae ree 49
5, Type, MOZ P5236, lateral view of left valve; 8 dorsal view of same specimen. Middle Hauterivian, Agrio Formation, Arenal de Las Lajas (Locality 28).
Se Rierotrigonial (Rinetrigonia) (COINUIGOeNSIS\(WEAVET)) 2. sires sele cco ks teas ee eke ele ede oe eer) eee) ecto eee 61
6, Hypotype, MOZ P5313, anterior view of both valves; 9, lateral view of left valve of same specimen; 11, dorsal view of same specimen. Middle and Upper Hauterivian, Agrio Formation, Cerro Mesa, Covunco (Locality 8).
BES TCIINIANEl a UMacrolrigoniad) VACGenSIS\(WEAVED) i cseck “risen one cen ann eee Eee tee 45
13, Hypotype, MOZ P2329, anterior view of both valves, with a probable byssal slit below the beaks. Middle Hauterivian, Agrio Formation, Los Hornos, Covunco (Locality 29).
90
Figures
2:
6, 11-13.
. Quoiecchia sigeli Leanza and Garate .
. Austrotrigonia pampeana Leanza and Casadio
. Trigonia wiedmanni Leanza and Garate .
BULLETIN 343
EXPLANATION OF PLATE 17
(All figures natural size, unless otherwise indicated)
Pacitrigonia'sobrali Leanza\ and \Gasadio: so <<< <:2csate sis) sic cs = ala 2 = oh = 0) forernye re) ohne eee aed aoa 1, Holotype, GHUNLPam 399, dorsal view showing radial costellae on the area; 2, lateral view of left valve of same specimen. Maastrichtian, Jagiiel Formation, Barda Baya, La Pampa (Locality 41).
3, original Paratype, MOZ P 1610/10, lateral view of right valve. Lower Hauterivian, Agrio Fomation, Pichaihue Abajo (Locality 3).
4, Holotype, GHUNLPam 400, lateral view of right valve; 5, dorsal view of same specimen. Maastrichtinan, Jagiiel Formation, Barda Baya, La Pampa (Locality 41).
7, Holotype, MOZ P0942/1, dorsal view; 8, iateral view fon right valve of same specimen. 9, Paratype MOZ P0942/2, dorsal view; 10, lateral view of left valve of same specimen. Lower and Middle Hauterivian, Agrio Formation, Cerro Negro, Covunco (Locality 9).
Pterotrigonia (Rinetrigonia) windhauseniana (Wilckens) ...........-- 20000 e cece eee eee eee eee eet eee eee 6, Hypotype, MOZ P2317/1, lateral view of right valve. 11, Hypotype, MOZ P2317/3, lateral view of left valve. 12, Hypotype MOZ P2317/2, lateral view of left valve; 13, dorsal view of same specimen. Maastrichtian, Jagiiel Formation, Cerro Villegas (Locality 27).
BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 105 PLATE 17
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 91
INDEX
(Bold numbers refer to plates in which a taxon is illustrated; italic numbers refer to pages in which a taxon is described; plain numbers refer
to pages in which a taxon is cited)
A
abrupta
PR UCHOMI SONI Aescnsee ccc varcececasctoseeronanaceesteouescsee sess esecs== 56,57 agniaensis
BUI VOD ONE) pee eaeaany concen toceten enearesassesesssneeeveseeecton- ane 31 agrioensis
PRUILLESO MI Gimme ancseoce-cesnetesacsesessecsansenssnss= 12,14,54,16,55,56 alamensis
PEICHITEO ONC enetenen sine senate aren ascseesccsacceertewsecseon scseansescose 64 aliciae
WORAOLE CCH Capertee ote a eec siete saeceasteceseecoamecaeeseccenedans 62,63 aliexpandita
TA IOVOTE scccetec tee Gee acco UCB COCA RCO SEE ELD Soe ES 8,12,17,23,24,10 aliformis
PICT OUVIZONIA c.cuescvccessssscresca se Jtese=sssese~ooseeens 11,14,58,14,59 Anditrigonia ........... 10,11,12,16,36,38,46,47,60,51,52,53,54,57
RINT IVICUIEIISIS tetean cos core rer cee eee coerce coo eeeen ee 11,12,46,47,5,48
RIES CONS PORsoecove wea oa ssa enon ease dante Sonatas See Seaheeeaeaiatssisesenes 49
TETATE copie RRC O EEE EDEOEEEE ROLE EEE EEECEEEES 11,14,16,47,48,9,50
(IZED ps lopetoe: CCIE LEDS CEPOL PEELE EEO BCOSECEC 11,12,46,49,9,50
PUILETTICSCVISISItasecsacce sac =eccsesc ate etesecneseeseccnesseeeceseorecsecccesans 47
RD MIDGCU cee ee ec ce sce e ces ewecesres sec sestectisse=teseeseteccssases 12,49,16
BPMN UV ent GCte cases seo. scccve: seocsvasesevesccercossneeeoe ences ee 11,12,49,9 >| TYCHO OTT E Goncocan diane nee gE Nene oS a ACO EEF ABREon Soca poe eEOEIDASIENO 45,54 BU AGLVQUZONIG) ac cveccnesanscs-sens sonsesecevsseseescssosse 10,36,37,38,39,40
COVUNCOENSIS) <occ seve cescsouessc2d2siceestceceestsece=: 10,14,38,39,4,40
WUC TIZCLIAAL = ctor soos oce ne aascanssce bance oveese sats coaseeeees 10,14,38,39,4
WESSOCOSLAL Geren occ roce esac ciao ee ete ee Testes tenets 10,12,38,39,4,40
CLL EXSCHID Ueno Aces esas te seenes feetezenbees 2 10,14,37,38,4,39 angulata
WIP EOONIICRAN US cocconsssneces snes ise sez rece sossschossccttacssessststecstessoss 29 angusta
WA SON iene ere ae = ee eae tae eSasecedessssssnsesscesscssecsstesteae sans 48 angustecostata
Hirt COMIGU Wee icc ce eerce. coi ivesccsesre zene 12,22,23,24,13,25;27 PENOUIPONIUINAG. cecccvaccxacscssssce8sc-senesstsiscsstcesscascostensesesceese 63 | TELE DULIED aeenie cece bocce ga RE ECC OO REREDARAARORACE HO 11,16,46,50,51,52
frenguellii .............. 11,14,57,8,52
ATOCDENL Fos occzsccecesess 11,14,51,52,8
opistolophophora 3 11,12,50,57,13 BIPOLUFEC OMIM enone scoces s0anesccescncasedeade cat cadence se caseaceessnees 17,36,63 araucana
WVAVODNOMEL Qimesesce ass ccasne ste setcesaseee te esc adee ses ssteeanene 10,14,29,1 argentinica
WAIVODROMEL Gace soic cic us seca ste scosd soe dicc ae oo censetstocessstetes 10,12,30,2 argo
PVAIODHONELI AGL: tassek conece cca atecavs sores caccttbeestesesicconsteries 34,35
Scaphogonia 31 arnisoe
TASS OLED! ocme coco ce eo CIEE EE EEE EEC EDE CECE EP EE OCECE SOURCE ACCC 48 BUSetl OLIE LONI GN os -2cevocan esos tac ecaeccetdonsssesscssctssccsstettewaasaeecences 56 attenuata
PICTOULZONIA GIfOTINIS NAN ...c22-222222:22-c2-csseoeeoecoscoesesentenss 59 BTUSTLOLFIR ONG caves swacwccnce sce eens socasesascs ta sssvessscteesenssaee 12,63,64
PIQIIDCANG asics ccccscevescssess sede ie thestrdsscscecesssceses 12,14,63,17,64
FOTUTEE! ceoreepagpe do COC EROS EEE OCI IG UE TEES EC COR DED SBE EEE SOCOSO 63,64
SACRE... saec AEB ORB CARE PRET E A: PORCECEOC DEED GEER ETO PEPE PP OIE 64 EMMISTHOUTIS ONIN AC yeseseae see eee seesccce sess sezeocsesebs ee entaa des casesaoeer 63
B
bajuranasi
LVI SONIG) eecene see sees eacesenencoe see rest tencesecsset cenceseascaseetesecanc es 20 biroi
ISVMOLFISONIGE se. senececentecestcetossseeraserasccessenesesss casremensis 57,58 boudiccae
AUP DILVI SOM ID eeace asco aeecece ate aieestee tenance scene sescoscse tees seeesers 53 brocardoi
SSI MOUGL CONIA merceaveccncts atte ae csr oseeescopccerscceasccees 12,57,16,58 Buchotrigonia 36,56,57
GQDFUPLA’ pace Fo con acenacscicastec ses acces ccercessecseecngesticceee testes 56,57
LODOCAIINENSIS) cc - coeasesceces stn cocseresstesecteccescen seers sesecuesscseoes 57
SD sec ee coe seet nen ccnecacctoceeveccecteccescer-conseatecssesacsrssesosecweseans 57 Buchotrigoniinaeyn suUbfandeycsse- sees se- eres ssc cesess-sessoesocees= 56,57 burckhardti
TQWOrSKIGH cee. «son cesa co cec tee cken soc deccsseesscocessetsee=se 10,14,28,1 bustamantina
IRLEV OL I SONI pear terre ae ee eesee sec caenes tse cccateces secon sen atenecratene 62
Cc
camachot
SCaphorella, = 2) 3. vecvssstestuseveceieecdseessvicntcessaceveues 10,12,35,3 capricornia
Phen OtniQOnial F220 ieeve case ses exes scwete end ccacsetenenciseesecoessee ses eeeee 62 (Gardin daetss hos eer ae ee rea ee 8 carinata
TPLQSONTAL Soca seccvcnceusOee sen goa Sek en Seve oe 8,11,14,22,7,23,24 carrincurensis
VA NCILTISONIAN oo 0x sox cseeces seeee ree oe eee eee 11,12,46,47,5,48 cassiope
DIT ISONIA ore cama aoce wore dear cece onc cena conan ee acee asec resect enente ss 24 catenifera
Miyophorell advice sete oc te aaa reas aGustussona sears 10,14,29,2 chilensis
SYMOLTEBONIA” fo. 8S Soca ccen csoicancwstassonus sdaxceeccsvecvexssedsticnetesee Si chunumayensis
WAU SONIA paren ncn centr nce orernreaeecerer: 10,12,36,2,37,38,53 chacaicoensis
INAEZOMLED cess socOe 47 Clavitrigonia 29 coheni
IRLCVOLTISONIG bac te eon e eee cence eeeiece secee et oneeree 11,14,59,6,60 cothuecoensis
IPLCFOLTIRONIG gore ener racic netics meee acon eaeetatenrerece 12,14,61,16,62 conocardliformis
TVEQONIG Allene sectn cece sececeecoees seceteeeatecsceaccesoeseceescenstentemaane 48 consanguinea
MATE ZONIAeetes a esdaseree ede ecee ta ssee toe saeweereccace soemeeeteremereaeee 48 corderoi
1 OAS) LC RE cere pore BEER EO CEEEECOSEOCEEO COL 10,14,3,4,5, 79, 20,21 costata
TIVES OMIA ease oe soon cowe woe koec tesco tenon aacaceeaeecnersa ce sesewe 10,21 costatula
sail ML QOTIIG weancwossenscascucsenecetestocerarncesre- ce seuntecereeesseeeeeeee 27 covuncoensis
PAINGIVAUGONI Aner eee ne ce ne ner ae eee 10,14,38,39,4,40 crassidens
TUZONIA wonsacncouscce ncn seen seen sees et sect ccccsecsetcusceedeesssaswecstssess 48
92 BULLETIN 343
crassitesta VOUES OLE. pac ceect ecco n EBS ne ERECT SI =E HORE IO OTC IG ICO ER ESO IO SSEOCED 37 crenulata Miyophonrellaric.cctes.caccsscocnonenccnece as ocene teceenttnenereeeeae ses 33,34 cristata IPLET OUI ZONI A arco ae eee oe eae sae oe sao en oor en ace ce ee season 58 cubanica (PIER OLTIZONIG a wenece ccc se ces er eae aaa cee esaeee ten son seas eeseesaeenes 59 curacoensis UI SONIAVANSUOTIA WN ale. ccasectadsccessoscccscsorccessracecceacases 42 D dawsoni Da elle (01 7 ene ene re Ror ee er ERE Re CER E SCO SDPO ace aE CCCOG IEEE COR CEES 32 delicata TTI SONCIING Jaen dencecsteas sess aceves ones: c2sseaeessntes jee eaavaeeswaecancs 36 densestriata FI ZONIQ) occvecssveosss caeeeurecs tec cnsce nese odsasces ests 10,12,2/,3,23,27 discors VANLIEPIQONIG cons Sess sheen ee Foe ceacnescoeee coe ceteteecenssee teses taesaee scene 49 distans MI QONID ev ecc ccwccccessartes te. daa ccecncascemcscnenacsss cesses seorecusneseans 57 diversicostata TIVES ONIG: a So eoRe ce Nec cos Sas a Se cae we acon sce stcaccheweSdacnweceeeee 53 E elegans Miyophorellar. sirco-2i secs 6a cc obec waenwovccoectuwecassaasacds set ssessneeeseee 33 elguetai Miyophorella se. s.c...<2sssccstses sssctacesearesenseeersorecs 11,12,33,9,34 I OANGILVI SONIA) nessa soc cvsccusecccct nee erecen eet tesenee eres 10,16,46,47 Ketel Pets ee ec occa see sas ccesuc sees sacecteeneoseaseane 11,14,46,47,2 IB OLAS ONIAE PR. ees cen fac een ew aat eden s de eat Soeeoeshsst 5 coe enen ene 8 EPIZOANS Hee eras shoes Sacnees Snsevcs onsen scassonccecntactstescacccccesoeerere 41,44 eufalensis My ODROMEL Al racacctestecmureeese sca cn sek eee eee saee teense nc cea tsias Seroeeceee 32 erycina SLEMMIMANELIGY mteters nee ste nsceases sce scesexesens 11,12,40,43,44,7,45 eximia VANGILVI RONG? Joc secess2ccccssssecc2---e4eeeceneeas 11,14,16,47,48,9,50 exotica VAUBONI A ern eree eer en cc asconoctee toneoee anes sens secberscnsceteoreese 38 F ferugliot PLC OLLI QONIOS siocaccaccccsccccscceseestccecs sou soos nae sncnseeseeeesessterer? 62 fortinensis EV LS ONG rece secs scene tee eee ec ee eae ees teneee eat ctsese 11,12,23,6,25 fuenzalidai ANGIVAUGONI ites. vescseasactadsceeecne rere eseseea tense sess 10,14,38,39,4 fraasi SV TOU IZONIG ces coreses svoccessccoudeestececee soe cceedessesecoesseneerees 56,57 Brenguellich a ccccccacesassce 2s nvassece- cron cearen se eeeneea as 9,10,17,26,27 ITIOXSDOCIALAT sence eon nce a coarse Serre Tenens en eee aes 10,14,26,2 PEN EZTOVOSE Fo Seve sc thve occa cccnce-Sccecesseascessecasesccsorees LO;V2521527,2 POULMON os vaner cons cc snes escorts eee ee eae cee teaeee 10,26,2,27 SDs Bis docceasseoctasetsccecohseosascansndseanedscees sausieescnaseacesesseeee 26,27 CODIQI cores ices csdeadectstecness <c5ssseseesaveusccentecen tt acuee 10,26,1,27 renpuelliellinaey...<..<c-ces-- ees ceeonceceneanseseecncern = sseseceseesses 26 frenguellii PANEULTIZONIGD EN coca cussctsessosscasccsceuscedcesnesteesnencese 11,14,57,8,52 G gampsorrhyncha
EYL ONIG.Sacewc ooh s ssas Se se ewe See ea eae oa ees wae ate seeee eater ene ee eee ee 48
garatet Myophorella gerthi Pterotrigonia Syrotrigonia gottschei VAUBONIG o.oo -c 2. seescsoc coos e Sees es ik sano 38 Groeberellan cn csScceeeecese ese ee ee 9,10,78,19 MCUQUENISIS some e ene rera orev ease ee 9,10,14,78,1,19 SP» ING Cte. oso. che coc cectwncewssedenncectne Se sees eee eee DET OES groeberi ANLULTISONIG I? on Piven Recs ox dee coe c os Seas eater 11,14,51,52,8 gryphitica TTIZONIG oss canes sacnvcevaguscesnsaeese=ten0uecesseccsesi eee eee eee ee 28 H UG e107 (7117 Seepper ren PCER EOE R Core CC BOoreeceee 11,12,16,32,33,60,62 AGWSOND: «53253 S5oscssi0000caedoueos stone stewet Some nwa be te Seer 32 hanetiana PACUMNIQONIG, o.2 ca cccsdeccdaudacczccessstwcenctnsce cooker deen eee 64 haupti ISLELIIINANCLIG Rixccoseck norecsene ene oe 11,14,40,43,44,6,45 herzogi St@INMNANELIG. ~ 005.000 sesseseseosoesase sss sacereee bee eseetee eR eee EEE 45 FT OLenOtri PONG: 2.2 sco.csen sats nae - noes Re Seas wa ceee REE OTS §2,53,54,63 hillebrandti Myopnorellai sic 32 Sccecnstewssetese ett ee 11,12,32,8 holubi SLCINMANENIG ~ <... 560 secs coscsseustoacscceecsecassdustueeeroe eee tee 40 hondeana TIQONIG ccsoeisesscosavdseests dvaiddssv-cecceeceeseeseesoeet coe ee eee 44 huenickeni INCUQUENILVIGONIA. co vesiectec-cbcosene da cen snes Coren oan 10,12,25,3,26 hugoi VirgOtriQONni.. sccccecsccese couse oases ceevo0ssesoestee 11,14,37,53,14,59 I inexspectata Frenguelliellay ..<c2cscnecst ees ose task ee eee ee 10,14,26,2 TOUIZONIA B Socccxeee vs coseu fees ooo i Wes ween eRe 36,37,38,46,52,57 CHASSUONG: sa ccvcvicn ve de jeuseave seas ode dca duwews estes coseee comet eee 37 Jotrigoniinae: cotc 02 0eveeesveczstecveceses~ ee cess ontee sl eeaee eee 52 J Taworskiella -scco2 ssa cts Soon oe oO 9,10,28 burckhardti 10,14,28,1 K kauffmani RRUELTIBONIA: cécecccccccsenseascte ssn scene ces =teeeateseenes 12,14,55,15,56 katterfeldensis Stein MANE) .cavcescenssssBesaecacwecsevasesoterisecen tent eee o RoR 45 keideli PF OANGIUTI SONIA Weeeseerense ns erner Nene eee sear 11,14,46,47,2 KoOroDKOVItrigOniG occ. 004:s5c0escoieonsndsenceece=<eesand es sntenee eee 56 kruusei SCAPNOVellG grav. scccadecccescoe onsen Oe 10,12,35,3,36 L Te QEVILTI SONIA oe cenascc dese scocees ssc ce onc one ea rereo cee seo cared tern eeeeme Laevitrigoniinae lamberti VA NAIL ISONIC rescceusecnessscecees cee aconenea renee eee eee 11,12,46,49,9,50 Eambertiellay cx cocccck soca ec aes eta ne an ee ere ere ence eee 37
TRIGONID BIVALVES OF ARGENTINA: LEANZA 93
WRATH DCTENL SONIC ox<2-22csiseesvossccsseseces acts sses% 11,16,36,46,52,53,54
PGICHIZIONCOICMSIS \cnssecesvees22-ese-sececasees 11,14,22,52,52,53,54,5 leanzai
IS GA DROV ELI weve cons: casces.cuecucactesssssesssusseccere 10,14,34,3,35,36 levyi
TABRDIATA 45 sscB0neeaeeepOes0d0C0 9000506000 eC OED ROB GO RO EABOCE 11,12,22,6,23 libanotica
ISU ROLT EO OMI Hmerenc meter eee weencaeee ne nasscses-secsestoesestaersisaal 56,57 BMETIOL IRON ec re cree cnt es cce sca nanecede-tornare-cerscscodeseesaseascosewemmece 56 lissocostata
VATIGEVQUPONNIG ree treeiene net cus cenceeadenc ees sonece sane 10,12,38,39,4,40 literata
TIS ON Liens settee enc ee cs cscesewastosess ae saetanesssreerenssce reise snares 47 losadai
TRAN ZO DL ec5e Rope eRe OCE COTE OCLCRE RCE ROOT EEEE CEE TEE EERE 10,14,205,21 lycetti
AUR ON I recon ctcocs te soreecon a. sate ecae sea eseeesecseseoseesscossseiecs 38 Lycettia
EDIZOADSTOM ree eee econ comes onecrce teeters tie sense sesce ee tate 41,44
M
macrorrhyncha
I IPONIG, wevcss.<cscsccese Macrotrigonia manflarum
Thy I SONIA peer renee oe renee eres cc eacaeat sane ctor sseve se cstcas sasctnensenees 38 RVI ADULTISONIGig mene see reece. Com enca ra sedest ssdesnsceacereess 11,46,52,53,54 margaritacea
INCOUPLZONIGN Reon n= wack sca cc vic stesciscst esses cots sae vacstu ste eteandressesecs 8 maxima
SS LCL TLIFICUIICLI tence acc ants cee sccccseereceseaen ce eet ee en oes ceeee ence aeseseens 45 mearnsi
AM ORO AGG GR seceepeme co Race ner ee cc RARE EE EED EES REE EEO SCOT eoRCAOCEGD 30 VICCILEFFANCOLTI SOT ip eee eee ee ene eee ee ose 44 RAC OMEN ISON Meee ence ete ect secre ccccedene nese nec oceemese teen ccsees 46,57 MepatrigOninacy ees esate ener ee reer ac eee eee ct oentcbossteaces 46,57 IMATE EIS ONIN AG erence. teen see eek e ee ornate ste eccsense soe cee steessescr ace 18 mirandaensis
ASSO Ee obec ac UE OSE ERE EEL OSOC EE PEELE PEPER ECRDOCEOCICOREIOIOOS LE 21795222 mollesensis
WAT ES OMNIA Baste swo ses cece es oa cs see ie ences Sete ee see N nee 10,14,19,20,2,21 multicostata
TI GONIQIEXIINIG NAL: oc. ccuscesacveseescecsscscceecdescessieseceseerees 49 Myophorella ..... 9,10,11,12,16,28,29,30,31,32,33,34,35,36,62,63
OPEL ASE O CEO EEE EPEC ERE 31
GV QUCON Open vant s focsnan cede seacensseie sc eseesecevs foceteacetceaes 10,14,29,1
ORFTIG TAD Veer Ber EE CECE ERE ASCE OAD ES 10,12,30,2
CHUA DO or onesie re voce Sea Se eee svacoce teu e sens ee tacdovesoiacuccnaeetes 34,35
catenifera .. es 10,14,29,2
ATTY TEER. POE EEOC OO ECE DEEEROCEREETEY EEO gOS 33,34
CIOQANIS ostcecesic dowsstaceceecctstasinntvdens sees itiesicecasicuessgusteeee tes 33
CL OUCL Be ee eee eS een re Sa 11,12,33,9,34
CUS I CNSIS fase cea osne sats Saclee Sea he ee eee See eake eee Nee See CENSUSES atone 32
STERN Tree ORO ACOREL REECE CERES LEREDT REET 1:2°3:7,12532
Wi EDrandtiirccks acco cccens ene ce cence cece reese leases susceue 11,12,32,8
PHICALPISU fous sees ccecscdesscecsovesectces seats terest bts eeiaie as sasictsedenets 30
LOC ULOS iment Paces cece ets Senet ee Ce ana eee Te 28
praescabroidea ... ve 1O312530531;3
SCHULZ ee ee ee ARTE eae ARR SA ieee eee NS 11,12,30,8
MUD EN CUIALE Bre ken fate en Tones code a a Be Teas eat eae an ae eon a 30
VOIKRELINEN IN. soo x on ested asad eee ee ake doe ee secten 12,32,12,33,34 Miyvophorellinae® 2asc.csveveccseccoecowesceesee soe so eveeesteete 28,56,57,63 PVIVODHONISONIGY scam ace cec tens Soaks ecco see ec cn icccniadieeTatesion eee 9,19
[RETR TRO LG URS BEER ROCL POPE COSOEPROCERCEPPCOCECER EOC EERE OECECOCP ECE CE SECE 19 My OPhOmMidacyemern: rec cereces rect cee eo see ree es oeeee rae eater et aber ser ee eeceee 7
N navis 1 AS $0) 1 17 paseo EPR EOP HEP O OR EC EECCODORD ROLE OC EDR IGEC ROCCO OOCOCCHOSEO CALC 34 NGOLKIQONIG: <oiiccvoccs suse sasasdeoecsssvattoececeosgiecesssaeeadserseesseteeseee: 8 INQFZATILACEG Po. scans sstoewerdseaenecsoatscsacceedessseensewsedseomisereencees 8 INCUQUENILFIBONIGN sca ccsecncecssce=sesetercteeosscsewasacenecdoacseee LOM 25 RUCNICKEND eestesstess ere 10,12,25,3,26 INGuquenitriponiinae: -+...-..2-.c2..-2s2z002-c22<0-4ceases secu scensters 25,26 neuquensis (Groeberell aes eee On 9,10,14,/8,1,19 neuquensis STEIN TNGANEl| ree aks coe eee cee eee 11,14,40,42,12 nodosa YORE O) 12 RE Bmree eect CrcEE eben eneceet ner eecooreccacrraeaccreRere: oon 42 nodulosa My Op hovel lQpriccnsonrcdiee teens coors tent eta eee cee nade wea e ease eee 28 Notoscabrotrigonia ... vee 11559560 INOLOLTISONI GN resre cence nescence asec sn ee oes tetera ee co saseea te tnteeee ee eee 64 OLIVEN Oli coceesvecns vance cecdes ee sae deee os det sezaeeatecde codecs donaconeen ees 64 INOtotmpontinaGeoscca tose ner oe eee ee aseeeceartenncceenscare 64 O oliverot IN OLOLFI SONI er anacac ce ceeses cates eee eae teeter tate tect arcsacereasernscces 64 opistolophophora ANLULTI SONI dma cere ena so saws dose cee deen eee tesciess ase 11,12,50,57,13 P pampeana PAUSLNOLTIP ONIG aoe aa aee cee or acct eee een eee eee 12,14,63,17,64 POCITISONIG ae socensecewesacs toce Foose seven su ee des Sede eee wer sene ee nee 12,64 CAIAINONSISS SE . Botenccae aioe cas ee ccna coe Sane eee ct esa nae eE ea ELe eS 64 RANCLIANG: aan scaececce cote see ooo oe he aT aera eee ce eee tae Ne eoecaas 64 IDALAQONICA OR ocean ess ot ee Neca leone aie cea acnsteteteotansdee sss 64 R001 701 | Re eRe ear eer rere REO CRED CRCE CEC EEEE ee SOcP EOE CECCCOACE 12,14,64,17 SYIVOSLEPL csocorcoas os se sceuedagsde oss aes sec thous dacaevebenes reas Seeeskay stan 64 patagonica PACUMNIZONIG® coc.0scteedeescesers nese css se 4: seacere se seedeeceweisseteaeccens 64 paradisensis SVPOLFIQONIG AN cc. sessvaccescsessss aes seteceee iene soeecodvateastesnsecse 57 SVIOMI SONIA Secccdeacvecdoscstoseacseetsessouete cdetaee odenses sna seserserses 58 (PAV ANGINIGONIG pacecceces seesecesteecces esse se 16,36,38,46,49,52,53,59 DOLFENLILENISIS fh oee cs oe cose ace seat sates ee ee 49,54 paucicostata MAY OPNOTISONIAG etree ooo eran ae Te eat eee Tene 19 perezreyesl ren guelligll aie rens cree stern eee re senen seven eee ren ese JO} 1:252'1527,2 peterseni Viv QOUTiQONIG: Fee.icc seco cece ceseseceascsessessicacsecseisssecesetees 52,53,54 peregrina IRULILTIQONIE Fooeec ect cone sectsuceea ec es cet ce ee ceed eet aeesee scree 54,55 pichimoncolensis TSAINDENINIGONIAiesene= eset ce creeeteeee ee eee 11,14,22,52,52,53,54,5 picunensis Trigonia 48 Pisotrigonia 61 plumasensis ANGILTIGONIDG tertescs vata dote eee eee eee ee 47 posadensis SleiInManella Rerasecen er tadessn stoner cscs reece oe coutywen eee eee a 45 potrerillensis (PAV ANCILTI CONIC waseee en rs cece see se conc sacneteeaenestencencees ees teers 49,54 poultoni
Prenguelliell anc. stor cnc cncwsk ost caecsscctesctascessescenes 10,26,2,27
94 BULLETIN 343
praescabroidea Miyophorellais sovccsscstene soca eer eee ea 10,12,30,31,3 prima VAUSLV OMNES ONIG Wee ree emcee mac eeee ce aesine ene es ie els commie cee aries 63,64 [RrOMYODROVE| | gtencnrcerecetece eres cece 10,11,12,16,29,30,37,32,34 SE OTN OIG ALIS Picci «Sanco uszs wee costs sees eetesso-teaeeecees stearate ones 31 PLCNOUNE ZONA sete eee eon eae enna 11,31,58,59,60,61,62 LIL ON TNAIS BBeae oes os Bee aes Seas oe See NCES 11,14,58,14,59 GN FONITIS VATA QUCNUGIG ann cece ce eseeeces seesenceteaseesneec terse ees 59 bustamantina’es---.-2.5--- eeaO2 CADIICOVIUG 2220 cosas cove noes send eee e basen en Sow eoe dee oe ese eae esas ss SeeT OSE 62 CONCMU BREN sd oo rosesatcaseeeon etwas xaos toe caceneneaetn 11,14,59,6,60 COLNUECOCNSISh asco tet shes noes 12,14,61,16,62 ICT ASU Qi. ch Pe ersls see eos eB ta es set eee ree Senne 58 cubanica ... 59 feruglioi .... Ss 62 DENN Ter merccncsccsess 60 SDepjUVApM eta sacs cece oe sace toesn ceesensesseenee soe oee oo 12,61,9 SLOWEY I secon cons sac acces aecseneenasees neta teant bec cateae etc ease rae cee MOOR 60 WECLIQNQ Sass ancacsae ae ses case Seodesswedsesneecn tasteassecse ac soe eR ee eReee ee 59 WIMGRGUSCNIANG a sc52eassecececescsecs essere enicee cose sease 12,14,62,17 PterotmigOntinae: 22. s0.2-<o.ccecceecs te aceon saccane eae sseseessnese 12,58,62 pusilla DVI SONIA Ss Soc cs.ccsucanave dec ces iota aveee nacce cen sugesterstee (eaceeecwesewes 48 pustulata Quadratojaworskiellaecinsec.c-sne-te ss accecseseseeeeneaaseseacessocce 28 Q (Ouadrajaworskiellad.2csscssccac se soeseeces ree erence oe ST eee 28 DUSTULALG eres. noncacnccn see a tee etek CUS Eee Oe CRO 28 @uadratotrigomiunae senses coceecs cose = cee eeeateas conc canes eet 56,57 quintucoensis Steinmanella 11,14,40,41,14,42 (ON) UR ol He crrer perpen eeeE CREEL PREC Racoon eer eee OEE 11,62,63 ALICIA oar aces se an iea tec baie ts dawn S0RtE Saw eee Re TORS eee 62,63 SURO Lernsaem seas Scouse cee ewes w oT ates 8s avons cbasaseescos ewes Seabees 12,63,17 R radixscripta PANAIVAUZONIG® csecccussaavewes nodeccsisecsteeeaiees sees 10,14,37,38,4,39 raimondit ISLET IN ANCL Gee eee een ek cect ee nee cee ee erence ese 12,40,43,11 rectangularis VQURONIG) : cacass cas teecws dacess cocseewas «WScsebeeceeseskewes 10,12,37,2,38 reesidei TI RON aan coe tere cre Reese sees e asa sen see cae eec ate ek STRUT 57 rierafonti ISCUDNOUM ISON Dye eeeres Snes ten seees eons eee ee 12,34,3 IRIMCLISONIG) «st seen cee c-acect teeeseeees 11,12,61,62 IRUELLTIBONIG ios sat cca scenes acca stasses soe tnwsst eecntecetist 11,12,54,55,56 ARTIOCNSIS <2 oc nce secs ccs snsscadneceesesstass Seeustoen 12,14,54,16,55,56 HAUT AME ese ose ce seo sass ee eee 12,14,55,15,56 IU ERTL UT ee CECE ECCI CCR EEC EEE ECO SOLO EEE CEEELECHOCOODOCOPECDA 54,55 SCMICHUENS IS) cerue scones vaes Snes e aac eae n cee ee 56 SpHjUV.indetsee5 ee cece ee «= 14;556;9 WEQVEND wc erase cascew de svouastede ste dooeneeene vacances gp aweeesineee nian eee 55 RUT tri POM Ae sees. esas cee asec sence ee eee ee ee 54,56 Ss sanchuensis IRULTUFI SONIA. teases cascasdeaesdssuocede svaeewusaueue cee th aaeaeasee meee 56 scabra DEVI ZONIG c02 ies soa scawsn ed chesce sock oes cen secs un dee eeee ae heen ee 60
SSCADIOLFIRONIG Po sens soso ssen ene aeee eae ae oe REE 11,60 Scaphogonia 31
ABO! Sies.ee0.0: 31 SCaphorella? is kssess wesecncire eicveen er 10,34
CAMACHOUS Fee een oe 10,12,35,3
VG UUSEL VoD korea ees as ee 10,12,35,3,36
NCO ZAIME eo al i RN Sa NS Ts HR eee 10,14,34,3,35,36
somensis ......... 34,35 Scaphotrigonia ... 10,34
TLCS ONED es seve Recess eesse oe SoS ee 12,34,3 schulzi
Myophorell a ...cescesvciscedicotes iene 11,12,30,8 secunda
AUSIFOLNI SONIA esi co oie doses sak Satu a ss coe ese Roe 64 semicostata
TYUQONIG 5.25 ccaceneencsssseece cot dveseseascudeot ou se sneer OTe 48 sigeli
QUOLECCNIG 2 oe 2 eee sso o2oe <n e522 ees oes sod Sep eee 12,63,17 sigmoidalis
Promyophorella’ <. .schccccdusctue ston sceekoanees ae 31 similis
DI BZONIAG 5 oe asec wadedicacee Sdeswen tan ba cacacscceee ett eee 21 sobrali
PACUY IRONED. ooo sos acs Sans ances os he ROS Se RUSTE 12,14,64,17 somensis
SCAPMOREUG: <2. <c. coc a0s sis. soko son sewseuse baton ee OTE 34,35 splendida
SEIN Mmanella re ern oe 11,14,49,43,11,44 SDIEnditnigOniai a seree ceceen eee 11,14,40,43,44,45 Sflelnmanella cece aces ee 8,11,12,30,40,41,42,43,45
erycina 11,12,40,43,44,7,45
haupti .... ee 11,14,40,43,44,6,45
WON ZOQL svawevcn a seocsusce< segue coda ces cose cece cece Tee EE 45
1:10) 171 2) HRA EE PPEPEEPECC CREEP EP EERE EC EET EER ECE EC ORE Foe sccocacnoroscoco7e0 40
Katterfeldensis ....c2.ccccacvcscocvees.aesveiet scussesoscssst enone 45
INAXLING. “vec cucnseeeeescee an oseccet seawes seule ts ole dua csdeees eee PR eR aeee 45
MCUQUCNISIS J svoccce se ccescsonsees ceee Rie eee renee ee 11,14,40,42,12
DPOSQGEMNSIS .. .2.2.s0c00050 000-05 e500es deosuessas edetevexte eee 45
quintucoensis ... e 11,14,40,417,14,42
FALINONGIL sores oeeen Serer ere ee oT 12,40,43,11
SDICNGIA Ajo srossceeca ere r nee eee 11,14,49,43,11,44
SLEINIMANML, swotcccscs cocenecen dese denn cac cane eee eee 11,40,42,13
MAA XY 110) 7 1 BEEP RPE EP ACEP EPEEE PEPE PEELE RACE CO PES ESO 12,14,40,4/7,10
VACARNSIS: 2.55) Soocdi oh ote es aoe EE OO 12,40,45,15,16 Steinmanellinae ’...<c.ccsc.< 202 scene .oscees-cssoec sc seecee a See ee 40 steinmanni
Stein Manel a: wccccceccicsscsioes seats doauawasastdes en eee eee 11,40,42,13
ISFOLTIBONIG’. Loses ss osc assacsdecusswava veces ee cee eae eoe Caen ee 57,58 stelzneri
TV ESONIG |v sossosecvccoecase~ csasds akon ew aa Sue eee Sue nee eU See eT 20,22 stolleyi
PLEVOUNLSOMNIG: ccavexcsheecs acoso sie tes thaseCose toe ent 60 substriata
VQUBONIG ....00.0008sce0sieccveccescsatessieats ies ceatessiaeseesceuserseeeeee 38 sulcata
VOUS foc czescsdesccewicceusniceisaceiei cules soak ose ene eee Te ROE 19 sylvesteri
PACUTISONIG® x ccses sous saean cme aesnoetnece ce ses et eee er eee ee 64 syriaca
DIVIZONIA s secsess scesweots daccawecenene eee cee oeee oes eee ee 57 Syrotrigonia 11,12,36,56,57,58
DIOL a: Boos de dace sst oe va Sock ace mean esse Cet essen RTE 57,58
DROCAT AOL as iexcdecseois ose cece eet neocon 12,57,16,58
CHILCNSIS 5.55. sc: sxe 5. oscsels dod ee seen late seen ate See 57
TRIGONIID BIVALVES OF ARGENTINA: LEANZA 95
RUGS Leeann cet nacswoveccntcartne sets rae sa ice cdcasccaanacses cueccees 56,57 Steinmann. ... 57,58 ZErtRD .....--- Sco BEBKS libanotica ........ pe OL 17, PROM QAGISCNSIS, coeccacicctixs Gecca2siesdovaseuecbu set cetesetsessdetsssenss-Es0es 58 ALND OT ACLISENSIS \3 02 ga sec sacenseciececaceeseseeeastceesechaacecesteees cured 57 T tapiai FCPOUCIITEL Ait encanes tee soc dcwushots stern eas cesecenssete sees 10,26,1,27 tesselicaudata VANAUTESONIQIEXLIMNIG! once socees- cose sce seaeeeesossecesisss 11,12,16,60,9 thoracica IPTC OUTIQONI A oe cce ac oc oes cae sa ccanscedcsoadestacesssbeceseeeesesseesieseoee= 60 tocaimaana FETE SONI Gan oaeres see ec sare as ts snake ds denlesjestase steseesesecceca seesaw 59,60 topocalmensis IBUCHOLTI SONIC warcacates te dstasc aces eared cows cee cee ese seme eee 57 transatlantica IPLCVOLVIQOMI Macedo vctsendenees sic 0s sede sce c- Seseee=seeseentee > 11,14,60,7,61 transitoria Steinmanella ... ee once ec 12,14,40,4/,10 Transitrigonia ... .. 11,12,40,41,42,43,44 HAT LO ONEIIN Anatase see cs ose eee ee eae Secie ee weee saaene Janecnseie ents 10,36 GeliGatale conse arsee recente Soras on tevin ecu ecvesgeeen desea tosesseesennces 36 HRI? RONIQ protec wasseeses sascce core coectectceeseciasss es LO} 11012-17,19:26:37 EILCXD ANG ILC pore nes ane ae eee ane 8,12,17,23,24, 10 ALTRI AL A ectewecnerce econ ce alee onde caeeecovds secnce osoaccueeteeetces 29 SISO oS p Ee PEDRO ROGET PEPE E EEE ECE EC EEE LERCH ECA eer EC EEE RE 48 angustecostata ... ie 12322'23524,13:525:27 Ai TIS OC Menno cme nnnes Socveas tosuscnestectceseseciccecsasscecdseetsesesstest 48 BOJUTCTIGSIR nee re ecco cae oer eee ee aerate 20 COTIPUAL Go see soc cag owas ante tntcereinakts doeteecceenscesee 8,11,14,22,7,23,24 CASSIOP Oc euc secs ces de tene ian case ouls Sones sn uewe veaaeos Costu ye tase eesese res 24 CRA CAIGOCNSIS Peaeen settee osc ee roe eaten serene wea eeee Snes Cea eet ee 47 ALL COMOCANAIJONINIS omen res ae dean nase eceaeare venen en eteeaes aateeee cee 48 CONS AN SUING Dimas see scoe as tones ee soon es caat one tessee eee ae Tee 48 CORUTROT a2 SPE OE EEE 10,14,3,4,5, 179, 20,21 10,21 48 LOD 2753523327, 57 53 49 HOES TIES eee eRe CEE EEE OTE 11,12,23,6,25 SSA SONTRYNCHE otic nas cose saan oN ceonk eee oo Ree kona ene ee ase ee ee 48 FOTY DR UIC eas ee coe nec chee be cee te cco hoes Soen eens teenie teanee ses 28 LONACAN AR aoe Sen eh SS oO ewes a nee eL eT Fede Naa Ee 44 LEVY Irae ee cae ec sect nidve ene de uedacte seis Senseatsateerees 11,12,22,6,23 UTR G OLE. oS Ea AP ec i ae a et Ce eae 47 HOOT ZTE pis area GCP AC DC PRICE ER ACE OSCR OORT EEE 10,14,20,5,21 IFLOACTONENY NCHA ceceeecee soot oe en she aeean es avese nese case eek ceeenss = tee ost 48 VLC A LLU sate See oe eet Nae toe ae nce at oe ae ee 38 TINTANGGAENSISPreraneene Pc nee e ene cae a neee TE neo ee: Ie 275 322 MNONCSENSIS ses sar cece rose c stent e est oae vice faese ese 10,14,19,20,2,21 LLY LS sae oe ena ce ne Ota co sid te Ne a Sema ens Dene ode Re eG SoA 34 ALT ey BOC OSAP nce e cen seer Re R Ee s Rne GO UR ETT SES ASE ee NESSOE ES 42 IDICUMENSIS: ss.c5s2ascvcessenvsessececesstasdsssscscasasesassaseracessessesesees 48 UST eee ean ne ae Poe ee Ss eee ne Senn Rec 48 REC TE sr ar R AEROS ERE BOER CORES BOSE EATER be RET SERED COE ERR EAE ScD ASE aCED Ear 57 SCLD Cee ene eee e tes eee tcs Ds ON No ns. c Wane Sena eters 60
ISEPVLLLES) Pate sess care een eae T on Uae tee OTR Oe CR See 21 sp. juv. indet. .... es 11,12,23,8 ISLEIZ NOR Diente ces rosea aes Noon adda nen SO ena A 20,22 SWIIAC! won. codecs ane dane nt arses coe nnawen ee onnct cemnee tence eccatecaaenee 57 EFANSILONIGI NAL} CULACOEMSIS oceseecceesdseceetaeescccneceasceeeecee neces 42 VENUTICOSG! Hiscacstetesus sus (du tncassveteescovesvicccsssiseceeasecewsunoneses 61 VYSCHELZRAL s30 cos cxase teense sisunsdoucsorsaceatissesinede sccusveasteesstetes 41 WICAIMANNI Se sese seas thent Sects cee eee ee nee ER ee CS NC RET 12,24,17 “Trigonia”’ costatula ...... Trigoniaceae ... Trigoniidae APTI PONT MAG see -esc esc ce secec ces cece cece cance sensei cece ace sues steeceseaueeee Trigonioida tuberculata Miyophorella'y.2. viccctomes? «coz sdoscshaucan does aaah ase sa de ee 30 tuberculata Miyophorellaicliarer neste ere ee 10,14,29,1 Turbitrigonia DOUGICCAC RT Rr ire d set ate Re eR Oa eR Let RTC ROTATE 53 Vv vacaensis S1elnmnanell dimer sereen cence ner eRe eee 12,40,45,15,16 VAQULONIGi mecer cera. spore sect ee aeei tee reee ee ece ee 10,36,37,38,40,52,57 CRUNUMAYVENSIS ress e-eee cere ctenn tener 10,12,36,2,37,38,53 OX OUGA Heer cteceas ct ecse ries ie: Sacesea Seta eeas ste eene Soe Sea eae CRETE POU SCH ET Rae se Sock Soe er ee RE en ee UYCOLEL a osreastcn ca seee <2 ea nce exes etestte ns aes oe sent see tat ons Serene oan eee rectangularis SUD SLT IOI wenee oe een nee WEN ONICG 2 cet eecedesces seceeees VaUgOMmicsCostatlONs cscs. cc sesso caeen ce naee ses a ee oo enna eee eeeeee 36 Wau gOniinae tenccceccccafecatc estos se ec es eres eee eer ee on tee 36,52,56,57 vectiana IPICFOLIISOMIA RD ea cocesevescac cae s konto te hea ce Saas ene eee ae aeae 59 VOCUS icc cc conc Sestecs setae sus cree ood cians wie ev ive ensues awe nen cacadaen ate neediee 19 SUI CALA toe ce rere eae Re TT Eee en Ee 19 ventricosa TPE QONI oc socccsecdeosees an aca ceded oa sk ese ida cocoa is usereveacecede ace secs 61 veronica UAE fo) 017 Bee sR are en She RR CERES ORCECTE REED CCE AEBCE COC EC RRCSEDCCROSES 36,37 Vil ZOU I LONIA econ ocean eee ec eee 11,16,46,52,53,54,59 ILIA 0) aes e RA Ba BPE a Fea ner EE aaa R PARP BS COREE 11,14,37,53,14,59 DELCVSOND.. rete ox See soe cose ree RAS OO re Ts cca $2,53,54 volkheimeri Myopnorellai.s-- te ccvccwsetesseoesn econ erent oer 12,32,12,33,34 vyschetzkii VI Q ONT) wk sc canacecevesncssst tate eatsceesnn oon aetna Sana e eee Te Sao 41 Ww weaver! TRULLI RON te se vac ceeds soescce se senees tae secee stsees cacae atone sei ceeeaere 55 wiedmanni UM EZONIA: oc se sshcb acs sudustecnecn coc ederedcesectien te wateaveteeee ven 12,24,17 windhauseniana Pterotrigonia .......... EOE 12,14,62,17 Y AAA See Te ACER eae os eee TE 42
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