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Gyils 


Nata 


VELIGER 


A Quarterly published by 

CALIFORNIA MALACOZOOLOGICAL SOCIETY, INC. 
Berkeley, California 

R. Stohler (1901-2000), Founding Editor 


Volume 48 


ISSN 0042-3211 


June 30, 2006 


Number 2 


CONTENTS 


A Preliminary Study on the Biology of the Predatory Terrestrial Mollusk Rathouisia leonina 
MIN WU, JIAN-YING GUO, FANG-HAO WAN, QI-LIAN QIN, QIN Wu, 
ANID AWNIDIRZAR WIERINONR: 6 oot: 8! 0,6" OG By COC Cro HL MOR OnE ee OS IEE Tae nan 61 


The Genus Offadesma Iredale, 1930 (Bivalvia: Periplomatidae) in the Miocene of Patagonia 
IMIG UE EA GRIEBINGANID)’ GUIDO! PASTORIN Os pj25 5/242) 5. iapilelay/si) ao 628 Gite ence) ae ele ale ates 75 


Cretaceous Acila (Truncacila) (Bivalvia: Nuculidae) from the Pacific Slope of North America 
RICHARDS Ss. S@OUIRESHAN DELO UB TBAVRe SAUL sh s)sfae dae cles ys es se ous ss fovea cls te es 83 


Temporal and Spatial Recruitment Patterns in Bankia martensi Stempell (Bivalvia: Teredini- 
dae) 
ST ORORNIAN GD) ay HOOPEZ ANDI I GONZALEZ 5s ee dene ee eee dee 105 


Two Introduced Pest Slugs: Zandonia budapestensis New to the Americas, and Deroceras pan- 
ormitanum New to the Eastern USA 
HEIKE REISE, JOHN M. C. HUTCHINSON, AND DAVID G. ROBINSON...........0+0005- 110 


Larval and Early Juvenile Development in Zegula funebralis (Adams, 1855) (Gastropoda: Troch- 
idae) in Baja California Sur, México 
SERGIO A. GUZMAN DEL PROO, TEODORO REYNOSO-GRANADOS, 
PABLO MONSALVO-SPENCER, AND ELISA SERVIERE-ZARAGOZA 2.0... eee eee eens 116 


The Veliger (ISSN 0042-3211) is published quarterly in January, April, July, and October by the 
California Malacozoological Society, Inc., % Santa Barbara Museum of Natural History, 2559 
Puesta del Sol Road, Santa Barbara, CA 93105. Periodicals postage paid at Berkeley, CA and 
additional mailing offices. POSTMASTER: Send address changes to The Veliger, Santa Barbara 
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THE VELIGER 


Scope of the journal 


The Veliger is an international, peer-reviewed scientific quarterly published by the California Malaco- 
zoological Society, a non-profit educational organization. The Veliger is open to original papers pertain- 
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column; in this column will also appear notices of meetings and other items of interest to our members 
and subscribers. 


Editor-in-Chief 

Geerat J. Vermeij, Department of Geology, University of California at Davis, One Shields Avenue, 
Davis, CA 95616 

e-mail: veliger@geology.ucdavis.edu 


Managing Editor 
Edith Vermeij 


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Terrence M. Gosliner, California Academy of Sciences, San Francisco (President) 
Hans Bertsch, National University, San Diego 

Henry W. Chaney, Santa Barbara Museum of Natural History 
Matthew J. James, Sonoma State University 

Rebecca F. Johnson, California Academy of Sciences, San Francisco 
Michael G. Kellogg, City and County of San Francisco 
Christopher L. Kitting, California State University, Hayward 
David R. Lindberg, University of California, Berkeley 

Peter Roopharine,California Academy of Sciences 

Barry Roth, San Francisco ; 

Angel Valdés, Natural History Museum of Los Angeles County 
Geerat J. Vermeij, University of California, Davis 


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This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper). 


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The Veliger 48(2):61—74 (June 30, 2006) Nee L ES 
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THE VELIGER 
© CMS, Inc., 2006 


A Preliminary Study on the Biology of the Predatory Terrestrial Mollusk 
Rathouisia leonina 


MIN WU 


College of Life Sciences, Hebei University, Wusidonglu 180, Baoding 071002, Hebei Province, China 
(e-mail:minwu @ mail.hbu.edu.cn) 


JIAN-YING GUO Aanp FANG-HAO WAN 
Biological Control Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, China 
QI-LIAN QIN 


State Key Laboratory of Integrated Management of Insects & Rodents; Institute of Zoology, Chinese Academy of 
Sciences, Beijing, 100080, China 


QIN WU 
College of Life Sciences, Hebei University, Wusidonglu 180, Baoding 071002, Hebei Province, China 


ANDRZEJ WIKTOR 


Museum of Natural History, Wroclaw University, Sienkiewicza 21, 50-335 Wroclaw, Poland 


Abstract. A study about the natural history of the slug Rathouisia leonina Heude, 1882 was carried out both in the 
field and in the laboratory. The external morphology, distribution, habitat, food range and preference, predatory behavior 
and reproduction were studied. Adult slugs were up to 1.02 g in weight and 35 mm long when kept inactive. They 
always preyed upon eggs, juveniles and adults of snails, rather than those of slugs of other families. Smaller individuals 
(0.18—0.55 g) showed preferences for feeding on bradybaenid snails Trichobradybaena submissa with larger diameter 
and larger apertural opening, while larger slugs (0.63—1.02 g) showed no such preference. The slugs also showed a 
preference for the eggs of Acusta ravida over those of Bradybaena similaris and T. submissa. The length of feeding 
scars on snail eggs made by infant slugs measured 0.24—0.47 mm, and those made by adult slugs 0.41—0.62 mm. After 
copulation adult slugs laid 10—49 eggs per clutch. The number of eggs was not correlated with their parent slugs’ weight 
but the diameter of the eggs (1.88—3.09 mm) showed a positive correlation to the parent slugs’ weight. It took 25—29 
days for the eggs to hatch at 17.5—23.5°C, 86% + 5% RH in the laboratory. 


INTRODUCTION 


Rathouisia leonina Heude, 1882 (Heude abbreviated as 
H. below) is a mollusk species that has not received at- 
tention since its original description. Among the approx- 
imately two thousand known species of land- and fresh- 
water gastropods in China, rathouisiid slugs have re- 
ceived little attention. Soleolifera (sensu Solem, 1978) 
comprise two families: Rathouisiidae and Veronicellidae 
(= Vaginulidae). Along with these two terrestrial fami- 
lies, there is a marine family Onchidiidae (order Onchi- 
diacea, sensu Solem, 1978) arranged in the superorder 
Systellommatophora Pilsbry, 1948. In China, six veroni- 
cellid species and three rathouisiids have been recog- 
nized: Vaginulus carbonaria H., 1882, V. fargesiana H., 
1882, V. chinensis (MOllendorff, 1881), V. lemonieriana 
H., 1882, V. patriatiana H., 1882, V. pictor H., 1882, 


Rathouisia tantherina H., 1882, R. tigrina H., 1882 and R. 
leonina H., 1882 (syn. Vaginulus sinensis H., 1882), dis- 
tributed in Sichuan, Hubei, Jiangsu, Guangdong, Guangxi, 
Yunnan (Wu, unpublished report) and Hong Kong. The 
known northernmost limit of rathouisiids in China is the 
northern bank of lower Yangtze River (Heude, 1882— 
1890). 

Heude’s family Rathouisiidae was based on the lack of 
a jaw and the presence of a protrusile proboscis or suction 
trunk, as well as those characters shared with the related 
group Veronicellidae (= Vaginulidae). The uniqueness of 
the mouth structure corresponds with its predatory life. 
There are three species belonging to the genus Rathoui- 
sia. R. tigrina with the smallest body size is black when 
alive and purple when preserved in ethanol solution; its 
dorsal striation is elongatedly ovate, similar to that of R. 


Page 62 


The Veliger, Vol. 48, No. 2 


Figure 1. 


leonina. R. leonina lives in the limestone hills of Cheng- 
kou county (31°54'N, 108°36'E), Sichuan. R. tantherina 
lives in the same habitat as R. figrina, but has a lighter 
body color and a longer body; its dorsal striations are 
polygonal to amorphous spots. R. /eonina, studied in the 
present work, has a larger body size than the previous 
two species and its body is elongatedly cylindrical in dor- 


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Group 1 Group 2 

Figure 2. Mean weight + SE (g) of R. leonina Group 1 and 


Group 2 in the experiment on prey size choice. 


R. leonina. 


sal view. R. leonina colonizes the eastern valley of the 
Yangtze River. Besides the localities mentioned below, 
one specimen (ZMIZO0801) collected by the Zoological 
Museum (Institute of Zoology, Chinese Academy of Sci- 
ences) suggests another occurrence of R. leonina at Shao- 
guan (24°48'N, 113°36’E), Guangdong, in S. China (Wu, 
unpublished). 

Heude (1882-1890) noticed that R. leonina is a pred- 
atory carnivore, preying upon land snails (Helix sensu 
Heude, 1882, which might belong to Bradybaenidae and 
families with similar shell shapes, according to the recent 
classification of land stylommatophoran shells). Heude 
also mentioned in the paper (1882-1890) that R. leonina 
lives in a similar habitat to the slug Meghimatium bili- 


Table 1 


K-means Cluster Analysis for the investigated parameters 
of tested 7. submissa, showing cluster centers. 


Ratio of Apertural 
Cluster Height Diameter height/ area 
center (mm) (mm) diameter (mm?) 
1 6.30 7.29 51 10.32 
2 5.40 11.48 .60 23.92 
3 4.24 9.53 15) 17.33 


Min Wu et al., 2005 


Page 63 


Table 2 


Preference records of the predatory slugs to different parameters of T. submissa, in Group 1 (slugs’ weight 0.189—0.55 
g) and Group 2 (slugs’ weight 0.63—1.02 g). Abbreviations: J—juvenile, A—adult, H—shell height, D—shell diameter, 


RHD—ratio of height/diameter, Ap. A.—apertural area, Asymp. Sig.—Asymptotic significance. Asterisk “‘*’? means 
statistically significant here. 
Conchological parameters of preys 
(Eee RHD RHD RHD Ap. Ap. Ap. 

Slug group J A H1 H2 H3 D1 D2 D3 1 2 3 Al A.2 A.3 
Group 1 

Sum of records 6 16 10 10 2 2 11 9 8 4 10 2 9 11 

Asymp. Sig. 0.033* 0.055 0.048* 0.280 0.048* 
Group 2 

Sum of records 5 3 3 1 4 3 3 a 3 2 3 2 3 3 

Asymp. Sig. 0.480 0.417 0.882 0.882 0.882 


neatum (Benson, 1842) (Philomycidae), although the for- 
mer species is not observed commonly. 

Although having a larger body size, R. leonina closely 
resembles Jncillaria sp. (sensu Kurozumi, 1985; Incilaria 
Benson, 1842, a synonym of Meghimatium van Hasselt, 
1823), which is distributed in Okinawa (26°13'N, 
127°40’E), Japan, based on available information on mor- 
phological characters and biology (Kurozumi, 1985). In- 
terestingly, R. leonina attacked all snails tested in the 
present work only through the shell aperture rather than 
both in this manner and drilling into the snails’ shells, 
reported for Jncillaria sp. (sensu Kurozumi, 1985). None 
of the two reports (Heude, 1882; Kurozumi, 1985) pro- 
vides a picture or photograph of such drilled shells with 
feeding scars, although the photograph of the scars left 
on the calcareous egg shells, which is quite similar to 
those left by R. leonina, were shown from Jncillaria sp. 
(sensu Kurozumi, 1985). Based on this point and the mor- 


Figure 3. 
leonina. 


Experimental set used to detect the egg choice of R. 


phological similarity, Jncillaria sp. (sensu Kurozumi, 
1985) might be more closely related to R. leonina than 
to herbivorous philomycid slugs. The eventual solution 
for this question will be based on the intensive compar- 
ative study of their morphology, habitats and other rele- 
vant ecological issues. 

This paper is the preliminary part of a work dealing 
with several aspects of R. leonina, which originated from 
both the interest in this rarely seen predatory slug and 
using it as a potential bio-control agent. However, the 
latter idea has been postponed, because of both the lack 
of detailed biological data and the extremely powerful 
predatory capacity of this creature shown in the experi- 
ments which raised special bio-safety considerations. 
Other problems revealed during this work and others in 
progress will be discussed elsewhere. 


MATERIALS AND METHODS 
Field Survey 


Field surveys were conducted respectively during May 
2000 in Zhongshanling (32°00'N, 118°42’E), Nanjing, 
Jiangsu province, China, and during March 2001 in Yi- 
chang (30°36’N, 111°12’E), Hubei province, China. 


Mollusk Collection and Rearing 


R. leonina (Figure 1): One living animal was collected 
from Zhongshanling, 2nd May 2000, two ones from 
Yichang on 30th Sept. 2000 and 49 (both adults and ju- 
veniles) from the same site in Yichang on 19th March 
2001, respectively. In the meantime, the predatory be- 
havior of R. leonina was observed both in the field (at 
Nanjing and Yichang) and in the laboratory. The R. /eo- 
nina slugs used in the present experiments and non- 
experiment observation were more than 52 slugs from the 
field and their offspring cultured in the laboratory. Hatch- 
lings were separated from their parents and were raised 


Page 64 


The Veliger, Vol. 48, No. 2 


Figure 4. Empty shells of prey. Upper row and left five of lower row: Trichobradybaena submissa; right four of lower row: 


Opeas arctispirale. 


together in the same container as the parents’ (see below), 
with fresh eggs of Trichobradybaena submissa (Deshay- 
es, 1873; generic position see Wu & Guo, 2003) as their 
daily food and with the empty snail egg shell not removed 
in this period. When they reached about 10 mm, they 
were separated and two non-experiment slugs were ran- 
domly picked out and raised together in one keeping con- 
tainer. All the slugs used in the experiments (see below) 
were adult individuals, whose maturity were proven by 
the fact that they began laying eggs. Each adult predatory 
slug used in the experiments and in non-experiment ob- 
servation was given a unique code such as A, E2 or Q4. 


Tested preys: Plenty of living slugs (both adults and ju- 
veniles) of Limacidae, Lehmannia valentiana (Férussac, 
1823) and Limax (Limacus) flavus (Linnaeus, 1858), slugs 
of Philomycidae, Meghimatium bilineatum, snails of 
Bradybaenidae, Bradybaena similaris (Rang, 1831), 
Acusta ravida (Benson, 1842), and Trichobradybaena 
submissa, and snails (both adults and juveniles) of Sub- 
ulinidae, Opeas arctispirale (Gredler, 1887), were col- 
lected in Yichang for this purpose. The snails not co- 
occurring with R. /eonina: both adults and juveniles of 
Cathaica fasciola (Draparnaud, 1801) (Bradybaenidae), 
were collected in the outskirts of Beijing; Helix (Cryp- 
tomphalus) aspersa (O. EK Miiller,) (Helicidae) and Acha- 
tina fulica (Bowdich) (Achatinidae), were taken from lab- 
oratory cultures. All above mentioned slugs and snails as 
well as their offspring, raised and used in the experi- 
ments, were kept in the laboratory located in Beijing. The 


eggs of B. similaris, A. ravida, and T. submissa, \aid in 
the keeping containers in the laboratory, were available 
all the time during the experiments. 


Food for tested non R. leonina slugs and prey snails: 
Snail’s biscuit made of hen eggshell 6%, soybean 27%, 
food-pellets for egg-laying hens 16%, maize 50%, Vita- 
min C 1%, finely smashed and well mixed with an ap- 
propriate amount of water, molded into blocks of 1 cm’, 
dried in a microwave oven. The biscuit was soaked with 
water for 1 min before feeding. Lettuce was offered and 
changed every two days, and the keeping containers were 
cleaned frequently. 


Keeping containers for R. leonina: Transparent poly- 
thene boxes (123 mm X 80 mm X 50 mm), a 0.5 mm 
space between the lid and the base ensuring the humidity 
and necessary air supply. A 10-mm layer of wet vermi- 
culite was evenly spread over the bottom of the box, and 
every ten days some water was added to the box to keep 
the humidity stable. The relative humidity in the keeping 
containers was kept at 86% + 5%. The different-sized 
individuals of 7. submissa, as well as their newly laid 
eggs (which were laid in other containers and/or laid by 
the food 7. submissa put into the keeping container for 
R. leonina) were supplied as slugs’ daily food. 


Design of Experiment on Prey Size Choice 


Fifteen predatory slugs (from adults collected in Yichang 
in March 2001 and their mature offspring) were studied 


Min Wu et al., 2005 


Page 65 


Figure 5. Empty shells of prey. Upper row: Cathaica fasciola; left two of middle row: Acusta ravida; right three of middle row: 


Bradybaena similaris; lower row: Trichobradybaena submissa. 


to test whether or not their choice of prey snails depended 
upon the snails’ size, shell shape or the different degree 
of maturity, from March 28th to May 11th, 2001. All the 
fifteen R. leonina individuals, which in size (estimated by 
the weight) included the smallest and the largest slug 
(Figure 2), were tested for the full period. In each exper- 
imental system (treatment), one predatory slug was 
placed into a keeping container together with six num- 
bered 7. submissa individuals, whose size and morphol- 
ogy were measured and the degree of maturity was re- 
corded. If 7. submissa laid eggs during the experimental 
period, the laid-eggs were quickly moved away. After a 
kill by the slug, the empty snail shell was promptly re- 
moved and a healthy snail of similar size and maturity, 
numbered and measured, was added. During the experi- 
ment, the fifteen tested individuals’ weights were mea- 
sured every week. 

The laboratory-kept predatory slugs were grouped into 
two groups according to their weights, using K-means 
Cluster Analysis. The slugs in Group 1 with the weight 
ranging from 0.18 to 0.55 g were represented by the final 
cluster center 0.31, and those of weights ranging from 


0.63 to 1.02 g in Group 2 were represented by the final 
cluster center 0.80 (Table 1). Using the same method, all 
the tested snails of 7. submissa were grouped into three 
groups by shell height, shell diameter, and relative aper- 
tural area approximately represented by the product of 
apertural length and apertural width (Wu & Chen, 1998). 
Then, if a snail was preyed on during the experiment 
period, its shell parameters and the degree of maturity 
were recorded as ‘‘1’’; otherwise they were recorded as 
“0” (sum of the records see Table 2). Npar Analysis was 
employed to detect if any of these factors affected the 
slugs’ predation. 


Design of Experiment on Egg Choice 


A food choice test of three kinds of snail eggs, to detect 
whether or not R. leonina prefers specific snail eggs (T. 
submissa, B. similaris and/or A. ravida), was designed 
and the experimental set was depicted as Figure 3. This 
experiment lasted for ten days from April 18th to 27th, 
2001. In each of thirteen tested predatory slugs (E1—E13, 
slugs from adults collected in Yichang in March 2001 and 


Page 66 


The Veliger, Vol. 48, No. 2 


Figure 6. Shells of juvenile Achatina fulica, preyed upon by R. leonina. 


their mature offspring cultured in the laboratory), 10 new- 
ly laid eggs each of 7. submissa, B. similaris, and A. 
ravida were added to pits A, B and C respectively (each 
pit was dug by 0.5 cm depth and partially separated by 
two pieces of thin glass (40 mm X 40 mm, thickness 0.5 
mm); the distance between the centers of the two adjacent 
pits was 30 mm). In eight controls (C1—C8): each pit of 
C1—C3 contained 10 newly laid eggs of T. submissa, each 
pit of C4—C6 contained 10 newly laid eggs of B. simi- 
laris, and each pit of C7—C8 contained 10 newly laid eggs 
of A. ravida. During the experiment the tested slugs re- 


Table 3 


The predation by R. leonina in the field and/or in the 

laboratory. +: offered and preyed upon in the laboratory; 

++: predation was observed in the field; —: offered but 

not preyed upon in the laboratory; ?: not tested in the 
present experiments. 


Hatch- Elder 


Species Eggs lings juveniles Adults 
Acusta ravida + + + + 
B. similaris + + + atcha sks 
T. submissa + + + + 
C. fasciola ? + + + 
H. (C.) aspersa us + ap = 
O. arctispirale ? ? + + 
Achatina fulica ue ar + ? 


M. bilineatum = = = = 
Limax (Limacus) favus = = a 
Lehmannia valentiana = on = 


ceived no additional food. The number of eggs consumed 
was recorded at the end of the experiment. 


Method of Weighing, Measuring 
and Data Analysis 


The weight of slugs was measured with a calibrated dig- 
ital electronic balance (accuracy +1 mg, EX-200A, Meh- 
cuhy), in the experiment on prey size choice. The length 
measurements of 7. submissa were made with a calibrated | 
electronic digital display caliper (accuracy +0.01 mm). 
The maximum diameter of R. /Jeonina eggs was obtained 
from digital photographs and measured by Photoshop 5.0. 
Statistical calculations were performed using SPSS for 
Windows 8.0.0 (SPSS Inc, 1989-1997, Standard Ver- 
sion). Bivariate correlation (2-tailed Pearson Correlation), 
non-parametric tests for several related samples (Ken- 
dall’s W Test and Friedman Test) and K-means Cluster 
Analysis using for grouping numerical characters were 
employed. 


RESULTS 
Morphology of R. leonina 


The weight of the adult slug ranges from 0.18 g to 1.02 
g (Figure 2). The length is shorter than 35 mm when 
inactive. Its body contracts inconspicuously when pre- 
served in 70% ethanol. The body color is light grayish 
brown to dark gray, sometimes reddishly tinted, and the 
color fades in ethanol solution. It has numerous discon- 
tinuous short black longitudinal striations, which are 
shortened and turned into elliptic spots when the slug 


Min Wt et al., 2005 


Page 67 


Figure 7. R. leonina preying on a mature T. submissa. 


contracts, distributed on its dorsal side. The sole of the 
animal is uniformly light reddish brown. The epidermis 
excretes a small amount of very sticky mucus. The optic 
tentacles are short and black, the lower pair of tentacles 
is somewhat shorter, lead-colored, bifurcate, and distally 
tapering when fully stretched (Figure 1). 


Habitat 


R. leonina is distributed from the middle to lower reaches 
of the Yangtze River, and is only known in Nanjing, 
Yichang and Shaoguan from our collection. It lives usu- 
ally at foothills and adjoining land, sometimes also in city 
gardens. In field observation during the dry season in 
May 2000 at Nanjing, R. leonina inactively rested be- 
tween the surface of sandy loam and thick litter layer, 
with co-occurring land mollusk species Cyclophorus sp. 
and A. ravida which were also inactive. In September 
2000 and March 2001 at Yichang, in the fairly humid 
environment, this species actively moved on the litter-free 
laterite, with co-occurring mollusks L. valentiana, L. (Li- 
macus) flavus, M. bilineatum, B. similaris, A. ravida and 
O. arctispirale. It prefers conditions of high humidity and 
shade, and usually rests on cool and smooth surfaces, 
such as on the underside of earth-free stones, bricks, and 
even on plastic pieces. Sometimes it retreats within the 


crevices of moist clods or within earth tunnels produced 
by other organisms. In the field, they are known to be 
active in temperature ranges from 10.5°C (lowest tem- 
perature in May) to 35.5°C (highest temperature in May) 
in Nanjing, and from 4.0°C (lowest temperature in March) 
to 35.0°C (highest temperature in March or October) in 
Yichang. 


Predation 


In the field, several times one to three R. leonina were 
observed around an egg clutch of M. bilineatum. Some 
egg clutches with R. /eonina resting nearby became milky 
and irregular in shape, and well distinguished from those 
in normal condition. However, we never observed R. 
leonina feeding on the eggs of M. bilineatum in the field 
or in the laboratory. In the laboratory, R. leonina was 
observed to prey on animals of O. arctispirale, C. fasci- 
ola, A. fulica and H. (C.) aspersa, and animals and eggs 
of B. similaris, A. ravida and T. submissa Deshayes (Fig- 
ures 4—6; Table 3). None of the slugs tested were attacked 
or preyed upon. When preying on snails, they always at- 
tacked the body through the shell aperture. The prey snail 
contracted faster than normal, and secreted a large 
amount of foam or mucus. They then became quiescent 
and seemed to be insensitive to the predation by R. leo- 


Page 68 The Veliger, Vol. 48, No. 2 


Figure 8. R. leonina, preying on a hatchling of A. fulica. 


Figure 9. Empty egg shells of 7. submissa, preyed upon by R. leonina. 


Min Wu et al., 2005 


Page 69 


Major diam. of feeding scars, mean + 2 SE (mm) 


2 


N- 12 8 4 
Maturity degree Adult Large juv. Small juv. 


Figure 10. Mean major diameter + SE (mm) of feeding scars 
left on the eggshells of T. submissa made by R. leonina of dif- 
ferent maturity degree. 


nina. Two methods of feeding were used by this slug, 
inserting its head into the aperture (Figure 7), or just pro- 
truding the proboscis (termed ‘suction trunk’ by Heude, 
1884) into the aperture (Figure 8), depending upon the 
aperture size of the prey. 

The statistical results shown in Table 2 indicated that 
smaller slugs (from Group 1) preferred mature snails, 
which were generally those with a larger shell diameter 
and larger aperture (asymptotic significance <0.05), to 
juveniles. For larger slugs (from Group 2), no preference 
was detected (Table 2). 

When R. leonina fed on snail eggs, it always kept a 
pose of curving its head and ‘neck’ in order to hold and 
fasten the egg, and bit into the egg a tiny hole, or feeding 
scar, which usually showed the shape of an elongated 
ellipse, a circle or rarely amorphous shapes. The edge of 
the hole was smooth or somewhat serrate (Figure 9). The 
laboratory observation on non-experiment predatory 
slugs showed: if they found eggs in the egg-laying pits 
dug by 7. submissa, they sometimes stayed in the pits 
until all inside eggs had been consumed; the holes pro- 
duced by the adults and the juveniles could be distin- 
guished by the major diameter range, as for older or 


Figure 11. R. leonina in copulation. 


Page 70 


Table 4 


R. leonina’s preference for the eggs laid by three species. 
In experimental systems (treatments) E1-E13, pit A con- 
tained 10 T. submissa eggs, pit B contained 10 B. simi- 
laris eggs, and pit C contained 10 A. ravida eggs. In 
controls, each pit contained 10 eggs—in controls C1—3, 


pits A, B and C with 7. submissa eggs; in controls C4— 


6, pits A, B and C with B. similaris eggs; incontrols C7 
and 8, pits A, B and C with A. ravida eggs. 


Sum of con- 
sumed eggs 


Sum of con- 
sumed eggs 


Sum of con- 
sumed eggs 


in Pit A in Pit B in Pit C 
El-E13 11 ff 28 
Cl1-C3 8 8 7 
C4—C6 13 6 6 
C7, C8 8 3 10 


younger juveniles the holes were smaller (Figure 10). The 
major diameter of feeding holes made by a mature indi- 
vidual of R. leonina ranged from 0.41 mm to 0.62 mm, 
and those made by elder or younger juveniles ranged 
from 0.24 mm to 0.47 mm. 


The Veliger, Vol. 48, No. 2 


R. leonina showed a significantly different preference 
for eggs laid by 7. submissa, B. similaris and A. ravida 
(Table 4, Test for several related samples, Asymp. Sig. = 
0.010; in controls, Asymp. Sig. = 0.267). The preference 
rank from high to low is: eggs of A. ravida > eggs of T. 
submissa > eggs of B. similaris. 


Reproduction 


Mature individuals: The mature slugs ranged from 0.18 
g to 1.02 g. In the laboratory, only a few mating cases 
were observed in time. A copulating pair of R. leonina 
could be instantly distinguished from their connecting the 
right sides of the anterior parts (Figure 11). 

Prior to egg laying, the slug dug a hole in the vermi- 
culite layer. The hole was slightly broader than the slug 
itself and of ca. 5-10 mm depth. Then the animal inserted 
its anterior body into the hole and began to lay eggs. It 
seldom laid eggs on the surface of the vermiculite layer 
(Figure 12). The eggs of R. leonina were translucent, light 
smoke-blue to light pink, spherical or ellipsoidal (Figures 
12, 13). In the field, the eggs of R. leonina could not be 
easily distinguished from those laid by L. valentiana (Fig- 
ure 14). In the laboratory, recorded egg laying was ob- 
served 8 times in 5 different individuals, i.e., predatory 


Min Wu et al., 2005 


Figure 13. 


Eggs of R. leonina, eggs normal smoke-blue. 


Figure 14. Eggs 


of Lehmannia valentiana, similar to those of R. leonina. 


Page 


va 


Egg number per clutch 
nm 
Cc 
—A_. 


1a 
16 21 22 40 76 
Parent slug's weight (g) 


Figure 15. The relationship of parent R. leonina slug’s weight 
(g) and the egg number per clutch. 


slug A laid 4 clutches during the experiment on prey size 
choice and during the daily culture. Most egg laying data 
from the slug daily culture were not recorded in order to 
avoid influencing the cultured slug maintenance. The 
predatory slug A laid its 4 clutches in the intervals of 6, 
6 and 4 days respectively. Each one of the 8 clutches was 
made up of 10—49 eggs, the large diameter of the eggs 
ranged from 1.88 mm to 3.09 mm (mean 2.30 mm). The 
weight of the parent predatory slugs showed no correla- 
tion to the numbers of eggs of each clutch (Figure 15; 2- 
tailed Pearson Correlation, sig. = 0.508), but showed a 
positive correlation to the eggs’ diameters (Figure 16; 2- 
tailed Pearson Correlation, sig. = 0.025). 


Hatching 


The embryos were visible by the naked eye when the 
eggs started to develop. In the condition of 17.5—23.5°C 
in the laboratory, it took 25-29 days for the eggs to hatch 
(Figure 17). In the first 1-3 days the hatchlings remained 
inside the egg-laying pit before they moved out of the pit 
and searched for food. Like their parents, the juveniles 
fed on calcareous snail eggs, hatchlings of snails and nev- 
er fed on herbivorous slug’s eggs. 


DISCUSSION 


Prey preference of the predatory land mollusks is always 
an important topic (Cowie, 2001). The present result 
showed that smaller individuals of the predatory slugs 
were particularly selective with respect to shell shape and 
size of prey, although larger individuals showed no pref- 
erence. The Indian carnivorous shelled snail Gulella bi- 
color preferred the snails Opeas gracile of the size close 
to themselves (Raut & Shahbabu, 1986). Under natural 
conditions, compared with Jncillaria sp. (sensu Kuro- 
zumi, 1985), R. leonina shows a more narrow prey range, 


The Veliger, Vol. 48, No. 2 


28 


Mean egg diameter (mm) per clutch 


16 21 22 70 76 
Parent slug’s weight (g) 


Figure 16. The relationship of parent R. leonina slug’s weight 
(g) and the mean egg diameter (mm). 


i.e., a less developed species preference. The former spe- 
cies was observed to consume the snails and eggs of hel- 
icoids such as Satsuma mercatoria (Camaenidae), Bra- 
dybaena circulus and Aegista elegantissima (Bradybaen- 
idae), the animals and eggs of prosobranch snails such as 
Georissa fukudai (Hydrocenidae) and Cyclophorus tur- 
gidus (Cyclophoridae), and perhaps Achatina fulica (only 
inferred from the feeding scars left on the egg shells) 
(Kurozumi, 1985). For R. leonina, only species without 
operculum, such as bradybaenids, and perhaps subulinids 
(not directly observed in the field, only inferred from sub- 
ulinids co-occurred in the habitats being predated in the 
laboratory). 

The most interesting result of the present study is the 
prey preference of R. leonina, showed by the experiment 
based on the eggs of three species T. submissa, B. simi- 
laris and A. ravida. However, limited by the food material 
for R. leonina, using eggs of T. submissa as the daily 
food of R. leonina might have influenced the results of 
the egg choice experiments: The slugs might have been 
““saturated”’ with 7. submissa eggs, and preferred eggs of 
the other two snail species for a change (Heike Reise, 
reviewing comments, 2004). This consideration raised the 
subsequent work which will be of great interest and nec- 
essary. 

In addition to the general interest in the natural history 
of predatory land mollusks, the idea for this study arose 
partly from the desire of choosing some ‘beneficial’ spe- 
cies with the purpose of controlling other harmful terres- 
trial snails such as the introduced A. fulica. For instance 
in Asia, Gulella bicolor (Hutton) that can prey on A. fu- 
lica, had been introduced into South Andamans in order 
to control the giant African snail before 1975 (Raut & 
Shahbabu, 1986). The present field observations show 
that R. leonina can occupy open habitats, such as at Yi- 
chang, and dry environments, such as at Nanjing. The 


Min Wu et al., 2005 


Page 73 


oe a 


Fe pen ae 
a ro 


Figure 17. Hatchlings of R. /eonina, making for the eggs of T. submissa; notice some eggs with regular feeding scars left on the egg shells. 


present direct observations have enriched our knowledge 
of the habitat of this group, adding to data for related 
species described by Kurozumi (1985). The use of similar 
habitats by the dubious “philomycid’ U/ncillaria sp., sensu 
Kurozumi, 1985) and A. fulica implies that such species 
may be considered as a bio-control agent against A. fulica 
(Kurozumi, 1985). However, the present experiments 
challenge such consideration promptly, and at least two 
obvious problems exist. First, the experiments showed 
clearly that R. /eonina preys on a wide variety of snail 
species and eggs. Although the experiments showed the 
preference for the eggs of agriculture pest snail A. ravida, 
people know almost nothing about whether or not the 
predatory slugs will show a stronger preference to other 
snails untested in the present study, whether the prefer- 
ence is of high plasticity which might be revealed when 
adding the species of the tested snails, and so on. Second, 
presuming we know this predatory slug well in the lab- 
oratory, what the situation will be when the slugs are in 
the field? It is well known that usually the laboratory 
result is too weak to predict the relevant situation in the 
field. The well known examples here are the East African 
carnivorous snails Gonaxis kibweziensis (Smith) and G. 
quadrilateralis (Preston) (Streptaxidae), and the rosy wolf 
snail Euglandina rosea (Férussac) (Spiraxidae), once the 


introduced ‘bio-control agents’ and eventually known as 
the dangerous invasive species, which in Hawaii and oth- 
er places have been causing ecological calamities (Cowie, 
2001). So the risk of their possible impact on the native 
biota should be adequately assessed before any consid- 
eration can be made on using them as so-called “benefi- 
cial bio-control agent’. The effort of using predatory non- 
marine mollusks as bio-control agents, as well as the di- 
rect damage and potential danger, has been well reviewed 
by Cowie (2001). Because very little biological research 
has ever been carried out upon this species, and much 
more remains to be done prior to making any conclusion, 
especially in relation to biocontrol practices. Besides the 
biology of R. leonina, the impact on the population dy- 
namics of different landsnail species should be empha- 
sized in further work. 

Acknowledgments. We are grateful to Dr Riidiger Bieler (Field 
Museum of Natural History, USA), Dr Beata Pokryszko (Mu- 
seum of Natural History, Wroclaw University, Poland), Dr José 
W. Thomé (Laboratério de Malacologia PUCRS, Brazil), Dr 
Robert H. Cowie (Hawaii University, USA) and an anonymous 
referee, for their good suggestions to relevant work. Great thanks 
go to Dr Tim Pearce and Dr Heike Reise for reviewing the man- 
uscript and providing critical comments. The work could not 
have been performed without having been sponsored by the Lab- 
oratory of Biocontrol Resources, Ministry of Agriculture, China 


Page 74 


The Veliger, Vol. 48, No. 2 


(LOBOR-00-04), the grants from the Natural Science Foundation 
of China (NSFC, No. 30100017). 


LITERATURE CITED 


Cowie, R. H. 2001. Can snails ever be effective and safe bio- 
control agents? International Journal of Pest Management 
47(1):23—40. 

HeEubE, P. M. 1882-1890. Notes sur Les Mollusques Terrestres 
de la Vallée du Fleuve Bleu. Mémoires Concernant 
LUHistorire Naturelle De L Empire Chinois 1-179. 

KurozuMi, T. 1985. Evidence of slug predation on land snail 
eggs. Applied Entomology and Zoology 20(4):490—491. 

MOLLENDORFF, O. FE 1881. Beitrage zur Molluskenfauna von 
Siidchina. Jahrbiicher der Deutschen malakozoologischen 
Gesellschaft 8:302—312. 


Raut, S. K. & A. K. SHAHBABU. 1986. Predatory behavior of the 
carnivorous snail Gulella bicolor. Environment & Ecology 
14(2):335-336. 

SoLeM, A. 1978. Classification of the land mollusca. Pp. 49-97. 
in V. Fretter, and J. Peake (eds.), Pulmonates. Vol. 2A. Sys- 
tematics, Evolution and Ecology. Academic Press. 

SPSS Inc, 1989-1997. SPSS for Windows Release 8.0.0 (22 Dec 
1997), Standard Version. 

Wu, M. 2003. Contribution to the knowledge of the Chinese 
terrestrial malacofauna (Gastropoda: Pulmonata: Helicoi- 
dea): description of a new Bradybaenid genus with three 
species. The Veliger 46(3):239-251. 

Wu, M. & D. N. CHEN, 1998. Zoogeography of Laeocathaica (s. 
str.) subsimilis subsimilis (Deshayes) in Sichuan, China and 
the conchological change trend in the genus Laeocathaica 
(s. str.) (Gastropoda: Pulmonata: Bradybaenidae). Acta Zoo- 
taxonomica Sinica 23 (Suppl.):107—116. 


The Veliger 48(2):75—82 (June 30, 2006) 


THE VELIGER 
© CMS, Inc., 2006 


The Genus Offadesma Iredale, 1930 (Bivalvia: Periplomatidae) in the 
Miocene of Patagonia 


MIGUEL GRIFFIN 


Facultad de Ciencias Exactas y Naturales, Universidad Nacional de La Pampa, Av. Uruguay 151, 
L6300CLB Santa Rosa, La Pampa, Argentina 
(e-mail: miguelgriffin@ aol.com) 


AND 


GUIDO PASTORINO 


Museo Argentino de Ciencias Naturales, Av. Angel Gallardo 470 3° piso lab 57, C1405DJR Buenos Aires, Argentina 
(e-mail: pastorin@mail.retina.ar) 


Abstract. 


The periplomatid genus Offadesma Iredale, 1930 was known from a few species found from the middle 


Eocene to Recent in New Zealand and Australia. Two new records are added from southern South America in Argentina. 
Offadesma sp., represented by a sole specimen from the Monte Leon Formation (late Oligocene-early Miocene) exposed 
near Santa Cruz, in southern Patagonia, and Offadesma isolatum n. sp., collected at Punta Pardelas (northern Patagonia) 
in late Miocene rocks referred to the Puerto Madryn Formation. The relationships to other periplomatids from South 
America seem to be remote, and therefore the migration of Offadesma from Australasia to South America during 
Cenozoic times as a consequence of the onset of the Antarctic Circumpolar Current is proposed. 


INTRODUCTION 


The family Periplomatidae includes—among others—a 
number of species known from shelf environments along 
the Pacific and Atlantic coasts of America and in tropical 
West Africa. They are generally not very abundant and 
as fossils they have been recorded occasionally in rocks 
of different ages ranging from Jurassic to Recent (Harper 
et al., 2000). Their occurrence—whether living or fos- 
sil—is restricted to specialized environments (Morton, 
1981b). In addition to their apparently low numbers, the 
aragonitic nature of their fragile shells conspires also 
against their preservation. 

In southern South America, the family is represented 
by two extant species, i.e., Periploma ovatum d’ Orbigny, 
1846 and Periploma compressum d’Orbigny, 1846. Both 
species occur along the coast from southern Brazil to 
northern Patagonia (Rios 1994). These two species be- 
long in Periploma s.s., and are clearly different from our 
material and appear to be unrelated to it. 

Periploma is represented by Periploma topei Zins- 
meister (1984, p. 1525-1526, fig. 10F—G; Stilwell & 
Zinsmeister, 1992, p. 89, pl. 10, fig. e-i) in the Eocene 
La Meseta Formation just off the Antarctic Peninsula. 
The interior of this shell, however, is unavailable and the 
shape is reminiscent of the rather quadrate Thracia mer- 
idionalis E. A. Smith, 1885 (Dell, 1990, p. 63-65, fig. 
109-111), an extant circum-Antarctic species. Shell in- 
teriors and conjoined specimens are necessary to ascer- 


tain the correct generic placement of Periploma topei. 
Other records of fossil Periplomatidae in southern South 
America are restricted to only six species. Periploma 
(Aelga) primaverensis Griffin, 1991 (p. 141-142, fig. 
10.3—10.6) appears very rarely in Eocene rocks exposed 
at the southernmost tip of the continent and has been 
referred to the subgenus Ae/ga Slodkewitsch, 1935 (type 
species Tellina bessohensis Yokoyama, 1924; p. 14, pl. 
3, fig. 1-5; Makiyama, 1957, pl. 12, fig. 1-5) because of 
the sinuous character of its commissure in ventral view. 
The second record is a specimen illustrated herein—prob- 
ably belonging in a new species—coming from the late 
Oligocene-early Miocene Monte Leon Formation exposed 
at Punta Beagle, a few kilometers upstream from the 
mouth of the Santa Cruz River, in southern Patagonia. 
The preservation of the sole specimen is too poor to war- 
rant full description, but it apparently belongs in Offa- 
desma, becoming thus the earliest representative of this 
subgenus in South America. 

The third record—i.e., the new species described here- 
in—is from Miocene rocks that outcrop along the coast 
of northern Patagonia and is the first one of the genus in 
Neogene deposits here, despite the fact that the faunas 
included in them are very diverse and well known. This 
testifies to the rarity of this taxon, which has obviously 
been overlooked during previous collecting in the area. 

The other three nominal species referable to the Peri- 
plomatidae were described from Tertiary localities along 


Page 76 


the Pacific coast of Chile. These are “‘Anatina” subor- 
bicularis Philippi, 1887 (p. 154, pl. 33, fig. 2) from Mil- 
lanejo, “‘Anatina” davilae Philippi, 1887 (p. 155, pl. 33, 
fig. 1) from Levu and ‘“‘Anatina” araucana Philippi, 1887 
(p. 155, pl. 23, fig. 14) also from Levu. Only “‘Anatina” 
suborbicularis may be possibly referable to Offadesma. 
“‘Anatina”’ davilae is a closed shell with damaged edges 
and apparently lacks an umbonal slit. This seems to pre- 
clude its inclusion even in Periploma. *‘Anatina”’ arau- 
cana is represented by an internal mold with only frag- 
ments of the shell adhered to it, and it is practically un- 
identifiable. 


GEOLOGY 


In the area surrounding Punta Pardelas (Figure 10) there 
are numerous exposures of rocks referred to as the Puerto 
Madryn Formation (Haller, 1978), a marine unit that has 
yielded an abundant and diverse mollusk fauna known 
from the earliest years of the Twentieth Century (e.g., 
Ihering, 1907; Brunet, 1995, 1997; del Rio & Martinez 
Chiappara, 1998 and references therein). The lithostrati- 
graphic unit comprises about 90 meters of sandstone and 
siltstone representing the widespread marine transgres- 
sion that occurred at the end of the Miocene covering 
large areas of southern South America (Frenguelli, 1920, 
1926, 1947; Camacho, 1967; Acenolaza, 1976; Irigoyen, 
1969; Haller, 1978; Herbst & Zabert, 1987; del Rio, 1992, 
1994, 2000 and references therein). Previous paleoenvi- 
ronmental work by Scasso & del Rio (1987) suggested a 
near-shore shelf environment for these deposits in the 
Puerto Madryn area. A sequence stratigraphic study by 
del Rio et al. (2001), allowed discrimination of a number 
of different cycles representing diverse shell accumula- 
tions reflecting changes in sea level and environments. 
The age of the Puerto Madryn Formation was believed 
to be Late Miocene based on its fossil content (del Rio, 
1988, 1992), K/Ar dating (Zinsmeister et al., 1981) and 
Sr°7/Sr*° dating (Scasso et al., 1999). 

At Punta Pardelas, only about 20 meters of the total 
thickness of the Puerto Madryn Formation are exposed. 
They include a bottom bed of gray mudstone with an 
abundant and well preserved invertebrate fauna (6.5 m), 
overlain by very hard yellowish tuffaceous sandstones 
(3.5 m), a very fine gray sandstone with abundant mol- 
luscan shells and echinoids (4 m), a yellow fine sandstone 
with abundant mollusks and echinoids (1 m), yellowish 
laminated mudstones with intercalated gypsum beds (6 
m) and cross-bedded light brown calcareous sandstone 
with abundant invertebrates. The material described here- 
in comes from the fine yellow sandstone at 15 meters 
above the base of the exposed section. 

The specimen of Offadesma n. sp. illustrated in Figure 
3 comes from the Monte Entrada Member of the Monte 
Le6n Formation, exposed at Punta Beagle, about 15 km 
inland from the mouth of the Santa Cruz River, at its 


The Veliger, Vol. 48, No. 2 


junction with the Chico River, province of Santa Cruz, 
Argentina, southern Patagonia. The Monte Leén Forma- 
tion (Bertels, 1970, 1980) comprises about 200 m of 
sandstone, siltstone and tuffaceous sandstone with a very 
diverse, abundant and well preserved mollusk fauna 
(Ihering, 1897, 1907, 1914; Ortmann, 1902; del Rio & 
Camacho, 1998, among others). The restricted outcrop at 
Punta Beagle includes only 10 to 12 meters of silty sand- 
stone, topped by a 60 cm oyster bank overlain by a hard 
and massive yellow sandstone from where the specimen 
was collected. The age of the Monte Leon Formation has 
been subject to controversy, but is generally accepted as 
latest Oligocene-earliest Miocene (Bertels, 1980; Nafiez, 
1990; Legarreta & Uliana, 1994; del Rio & Camacho, 
1998; Barreda & Palamarczuk, 2000). 

All specimens described are housed in the Museo Pa- 
leontol6gico Egidio Feruglio (MEF-Pi), Trelew, Argenti- 
na and the University of La Pampa (GHUNPam), Santa 
Rosa, Argentina. 


SYSTEMATICS 
Class Bivalvia Linné, 1758 
Subclass Anomalodesmata Dall, 1889 
Order Pholadomyoida Newell, 1965 


Superfamily THRACIOIDEA Yonge & Morton, 
1980 


Family PERIPLOMATIDAE Dall, 1895 
Genus Offadesma Iredale, 1930 
Type species: Offadesma angasi Crosse & Fischer, 1864. 


Remarks: Offadesma has been considered a subgenus of 
Periploma Shumacher, 1817 by various authors (Keen, 
1969), while others considered it a distinct genus within 
the family (Rosewater, 1968; Fleming, 1950). The much 
more pronouncedly inequivalve shells, the posteriorly in- 
clined chondrophore with poorly developed anterior and 
posterior outer ligaments, and the entirely missing litho- 
desma seem to warrant generic distinction (Fleming, 
1950; Coan et al., 2000). 


Offadesma isolatum Griffin & Pastorino sp. nov. 
(Figures 1—9) 


Diagnosis: Medium sized Offadesma (height about 40 
mm, length about 60 mm) with chondrophore strongly 
directed postero-ventrally, anterior margin somewhat pro- 
duced, right valve inflated (about 25% more than left 
valve), posterior rostrum occupying 28-30% of total shell 
area. 


Description: Shell strongly inequivalve, inequilateral, 
very thin, about 60 mm long and 40 mm high; right valve 
deeply cup-shaped; left valve gently convex; right umbo 


M. Griffin & G. Pastorino, 2005 


Figures 1-9. Offadesma isolatum n. sp. Figures 1—3. holotype MPEF-PI 190, left. right and umbonal views, Punta Pardelas. Chubut, 
Argentina, Puerto Madryn Formation. Figures 4—9. paratype. MPEF-PI 191 Figure 4—5. Internal and external views of the left valve 


Figures 6—7. Ventral and dorsal views of the same specimen. Figures 8—9. External and internal views of the mght valve. Scale bar = 
1 cm. 


Page 78 


arched over left one; anterior margin rounded, narrowly 
gaping anteroventrally; posterior margin rostrate, truncat- 
ed and slightly directed upwards and leftwards; rostrum 
slightly gaping; weak oblique ridge running from umbo 
to base of anterior margin; broader and slightly stronger 
ridge extending from umbo to base of posterior trunca- 
tion; area between posterior ridge and dorsal border of 
shell apparently covered by fine sand grains which are 
impressed on the shell surface; transverse umbonal crack 
present, running perpendicular to dorsal antero-posterior 
axis of shell for about 10% of total height; anterior edge 
of crack overlying posterior edge; primary ligament in 
deep spoon-shaped chondrophore directed postero-ven- 
trally; anterior outer lamellar ligament running in short 
moderately deep slit for about dorsal fourth of total height 
of inner fibrous ligament; posterior outer lamellar liga- 
ment in slightly wider and longer slit; chondrophores sup- 
ported by clavicles extending from the posterior face of 
chondrophore in postero-ventral direction; chondrophores 
unequally aligned vertically, displaced to the right into 
the cup-shaped right valve; adductor muscle scars and 
pallial line unknown; external surface carrying weak and 
regularly spaced commarginal ribs and growth lines evi- 
dent in the intercostal spaces. 


Type locality: The material comes from Punta Pardelas 
in Peninsula Valdés, northeastern Chubut, Patagonia, Ar- 
gentina. All specimens come from rocks included in the 
late Miocene Puerto Madryn Formation. 


Type material: Holotype, MEF-Pi-190a, a_ bivalved 
specimen (valves loose); paratype, MEF-Pi-190b a bi- 
valved shell, partly broken. 


Remarks: This species closely resembles Offadesma 
marwicki Fleming, 1950 (p. 246—247, pl. 24, fig. 10). The 
type specimens come from Black Point in the Waitaki 
Valley, New Zealand, where they were collected in late 
middle Eocene (Bortonian) rocks. Fleming also mentions 
this species from the Pahi Greensands in North Auckland, 
also Bortonian in age; these are the earliest record of 
Offadesma. As in the material from Punta Pardelas, the 
shell is not quite as strongly inequivalve as in the type 
species, which has a more inflated left valve. The New 
Zealand specimens seem to be slightly smaller and the 
umbos are more prominent than in our material. 

Offadesma angasi (Crosse & Fischer, 1864) lives pres- 
ently along the coast of southeastern, south and south- 
western Australia and also in New Zealand (Rosewater, 
1968; Morton 1981a). The only apparent difference with 
Offadesma isolatum n. sp. 1s that the shell in the type 
species 1s more strongly inequivalve and the anterior mar- 
gin of the shell is more evenly rounded. 

Offadesma sp. (Marwick, 1931, p. 83, fig. 110-111; 
Fleming, 1973, pl. 64, fig. 720-721) from the Kapitean 
(late Miocene) of New Zealand is very similar, except 
perhaps in that the shell is more strongly inequivalve. 


The Veliger, Vol. 48, No. 2 


42°S4 


Punta Norte 
Golfo San Matias 


South Pacific 


Golfo San José 


Puerto Piramide\y. 
Punta Pardelas 


Puerto Golfo 
Madryn Punta Loma Nuevo 


Figure 10. Location map of the fossil locality in the Valdés 
Peninsula area, Argentina. 


Unfortunately, the interior of the material described by 
Marwick is not visible for further comparison. 

Of the three species of Periplomatidae described by 
Philippi (1887) from Tertiary rocks in Chile, none show 
the interior of the shells. Therefore their inclusion in Of- 
fadesma (and in two cases even in Periploma) is at pre- 
sent at least doubtful. The species that most closely re- 
sembles ours in shape is “‘Anatina”’ suborbicularis Phi- 
lippi, 1887 (p. 154, pl. 33, fig. 2). However, it is much 
higher and apparently the posterior end of the shell is less 
clearly defined and the posterior gape is much narrower 
than in Offadesma isolatum n. sp. 

Other species of Periplomatidae from South America 
can not be compared with our material. They all fall with- 
in Periploma s.s. and their differences with Offadesma 
are readily clear. Such is the case of the extant species 
from the Caribbean and northern South America Periplo- 
ma (Periploma) coseli Ardila & Diaz, 1998 (p. 69-71, 
Fig. 1-2, 5) and Periploma (Periploma) sanctamarthaen- 
sis Ardila & Diaz, 1998 (p. 72, Fig. 3-4, 6). These are 
missing the distinctive backward pointing chondrophore 
and the posterior rostrum of Offadesma, which are clearly 
visible on our specimens. Likewise, the west African re- 
cord of this genus, i.e. Periploma camerunensis Cosel, 
1995 (p. 102-110, figs. 144-145) is also very different 
from Offadesma, while it appears to be quite close to the 
Caribbean species. 


Etymology: From the Latin isolatum = detached, sepa- 
rate, in allusion to its isolate occurrence from other rec- 
ords of the genus. 


Offadesma sp. 
Figures 11—13 


Material: One specimen, partly decorticated and some- 
what crushed (GHUNLPam26300). 


M. Griffin & G. Pastorino, 2005 


Page 79 


Figures 11-13. Offadesma sp. (GHUNLPam26300) from Punta Beagle, province of Santa Cruz, southern Patagonia, Argentina, Monte 
Entrada Member of the Monte Leon Formation. Scale bar = 1 cm. 


Occurrence: Punta Beagle, province of Santa Cruz, 
southern Patagonia, Argentina (49°57'S 68°41'W). The 
specimen was found within the Monte Entrada Member 
of the Monte Leon Formation, at the top of the exposure 
of this unit in Punta Beagle. 


Remarks: The only specimen available is somewhat de- 
formed and the margins too broken to allow proper de- 
scription or even accurate comparisons with other taxa. 
However, what is visible of its hinge shows a chondrop- 
hore that leaves no doubt it is an Offadesma. It is smaller 
and slightly more rounded than Offadesma isolatum n. 
sp. from the Puerto Madryn Formation. The significance 
of this material lies in that it is the earliest record of the 
genus in South America. 


BIOGEOGRAPHIC HISTORY OF OFFADESMA 


The living species of Offadesma are restricted to Austra- 
lia and New Zealand, while Periploma s.s. is known to 
occur along both coasts of the American continent (in- 
cluding the coast along northern Patagonia) and along the 
western coast of tropical Africa (Cosel, 1995). The pres- 
ence of Periploma in Africa can be easily explained 
through passive dispersal of larvae across the Atlantic in 
an eastwards direction by means of the Equatorial Un- 
dercurrent or the Equatorial Countercurrent. The role of 
these marine currents in passive dispersal of larvae of 
different groups of mollusks in the tropical Atlantic 
Ocean has been discussed by Scheltema (1995). Morton 


(1981a) assumed a short planktonic period for the larvae 
of Offadesma, based on the size of the eggs and compar- 
isons with other anomalodesmatans. He even suggested 
that the eggs may be incubated in the ctenidia, although 
admitting that there is no evidence for this. While the 
larval development of this genus remains obscure and 
further research is needed to assess its role in the geo- 
graphic distribution of its species, the evidence provided 
by the fossil record suggests that it was far more wide- 
spread earlier in the Cenozoic than at present. No larval 
stages are known for fossil forms, but it could be possible 
that with increasing specialization and concomitant oc- 
cupation of narrower niches, a shortening in the duration 
of larval stages would ensure the rapid development cru- 
cial to ensure rapid colonisation of difficult environments. 

In Patagonia, the family is represented by Periploma 
ovatum d’Orbigny, 1846 (p. 514, pl. 81, fig. 10-12) and 
Periploma compressum d Orbigny, 1846 (p. 514, pl. 78, 
fig. 19-20), both ranging from (northern?) Brazil to 
northernmost Patagonia. As already stated, although all 
these species undoubtedly belong in Periploma, their 
shell characters show that they are unrelated to the Indo- 
Pacific Offadesma and thus to Offadesma isolatum n. sp. 
from the Puerto Madryn Formation. The two extant spe- 
cies from the southwestern Atlantic seem to be closely 
allied to the Caribbean taxa mentioned above. This leads 
to the presumption that the origin of the two living taxa 
must lie in a southward migration of Caribbean fauna as 
proposed by del Rio (1991) and Martinez Chiappara & 


Page 80 


The Veliger, Vol. 48, No. 2 


del Rio (2002). This migration would have been respon- 
sible for the development of the Valdesian and Paranaian 
Malacological Provinces (Martinez Chiappara & del Rio, 
2002) along the coasts of the southernmost tip of South 
America during the late Miocene. Although the south- 
ward flowing Brazil current could have played a role in 
the dispersal of larvae along the coast of South America, 
it was probably far more important in the establishment 
of appropriate ecological conditions for the settlement of 
species from warmer water. These species could have ex- 
tended or restricted their southward range merely by oc- 
cupying or vacating progressively warmer or colder areas 
at the southernmost extreme of their distribution as the 
influence of the Brazil Current varied with the evolving 
circulation pattern in the South Atlantic during the Ce- 
nozoic. The warmer conditions that enabled the devel- 
opment of the provinces proposed by Martinez Chiappara 
& del Rio (2002) would have been caused—according to 
them—by a temporary blocking of the Antarctic Circum- 
polar Current (ACC) due to the appeatance of the Scotia 
volcanic arc. This, together with the fact that the cold 
northwards-flowing Malvinas Current (MC) was not fully 
developed yet, would have been the main cause of the 
warming of the surface water in northern Patagonia. Nev- 
ertheless, Martinez Chiappara & del Rio (2002) suggested 
that a proto-MC may have been to some extent already 
influencing the conditions in the area during the late Mio- 
cene, as indicated by the fossil content of some of the 
shell bearing beds in the Puerto Madryn Formation. 

At any rate, some elements of the Miocene fauna from 
the Puerto Madryn Formation could possibly have orig- 
inated elsewhere. It is well known that the opening of 
Drake Passage was crucial in the development of the pre- 
sent marine circulation pattern in the southern oceans. 
This opening probably occurred at the end of the Oligo- 
cene (23.5 + 2.5 Ma; Barker & Burrell, 1977, 1982), 
although it could have been a long process beginning as 
far back as 37 Ma (Crame, 1999). The consequent onset 
of the ACC—and its intensification with the beginning of 
glaciation in West Antarctica just before the end of the 
Miocene (Kennet et al., 1975; Kennet, 1977; Kennet & 
von der Broch, 1985)—provided a gateway for the mi- 
gration of many mollusk genera from New Zealand east- 
wards to South America and from South America east- 
wards to Australasia. Examples of such migrations are 
many (Beu & Griffin, 1996; Beu et al., 1997) and taxo- 
nomic work on the Patagonian faunas may prove that 
there are even more cases that have been overlooked. One 
of these could be the case of Offadesma isolatum n. sp. 
The rarity of this species due to its fragile shells and 
restricted habitat (Morton, 1981b) could explain why it 
has not been previously mentioned in the Patagonian fos- 
sil record. The affinities of the new species described 
herein seem to lie with Indo-Pacific taxa ranging back 
into the Paleogene. While yet unclear and possibly sub- 
ject to change with further collection, the fossil record 


and present distribution of Offadesma point towards a 
southern Indo-Pacific origin. Although the fossil record 
of this genus is very poor, its appearance in New Zealand 
as early as the Bortonian (late middle Eocene) appears to 
be consistent with its present distribution and the only 
discordant records are the early and late Miocene South 
American occurrences. While acknowledging its poor 
chances of preservation, the absence of Offadesma from 
Cenozoic rocks anywhere in North, Central or elsewhere 
in South America suggests that its presence in the early 
Miocene Monte Leon Formation and the late Miocene 
Puerto Madryn Formation is unlikely to be caused by its 
southern migration from warmer water further north 
along the Atlantic coast. More plausible seems to be its 
arrival in southern South America as a consequence of 
dispersal by means of the ACC. The fact that it appears 
earlier in New Zealand is consistent with the postulated 
Indo-Pacific origin of the genus. The chances of passive 
dispersal of larvae in an eastwards direction from New 
Zealand to South America—rather than from South 
America to New Zealand—would be enhanced by the 
shorter distances involved and the increased speed of the 
ACC during the Miocene. The distribution of some mol- 
lusks common to South America and New Zealand/Aus- 
tralia is still poorly understood. However, it may be pos- 
sible that migration between both areas occurred repeat- 
edly throughout the Cenozoic in both directions, even as 
recently as the late Pleistocene, when the bivalve Ana- 
dara trapezia suddenly appeared in New Zealand (OIS11) 
and Australia (OIS7), probably descending from a South 
American ancestor (Beu & Griffin, 1995; Beu et al., 
1997; Murray-Wallace et al., 2000). 


Acknowledgments. Rodolfo Brunet generously provided the ma- 
terial described herein. We would like to thank the thoughtful 
comments by two reviewers which helped improve the original 
manuscript. We acknowledge funding by the Consejo Nacional 
de Investigaciones Cientificas y Técnicas (CONICET) of Argen- 
tina, to which both authors belong as members of the “‘Carrera 
del Investigador Cientifico y Técnico.” 


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The Veliger 48(2):83—104 (June 30, 2006) 


THE VELIGER 
© CMS, Inc., 2006 


Cretaceous Acila (Truncacila) (Bivalvia: Nuculidae) from the Pacific Slope 
of North America 


RICHARD L. SQUIRES 
Department of Geological Sciences, California State University, Northridge, California 91330-8266, USA 


AND 


LOUELLA R. SAUL 


Invertebrate Paleontology Section, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, 
Los Angeles, California 90007, USA 


Abstract. 


The Cretaceous record of the nuculid bivalve Acila (Truncacila) Grant & Gale, 1931, is established for 


the first time in the region extending from the Queen Charlotte Islands, British Columbia, southward to Baja California, 
Mexico. Its record is represented by three previously named species, three new species, and one possible new species. 
The previously named species are reviewed and refined. The cumulative geologic range of all these species is Early 
Cretaceous (late Aptian) to Late Cretaceous (early late Maastrichtian), with the highest diversity (four species) occurring 
in the latest Campanian to early Maastrichtian. Acila (T.) allisoni, sp. nov., known only from upper Aptian strata of 
northern Baja California, Mexico, is one of the earliest confirmed records of this subgenus. “‘Aptian”’ reports of Trun- 
cacila in Tunisia, Morocco, and possibly eastern Venzeula need confirmation. 

Specimens of the study area Acila are most abundant in sandy, shallow-marine deposits that accumulated under warm- 
water conditions. Possible deeper water occurrences need critical evaluation. 


INTRODUCTION 


This is the first detailed study of the Cretaceous record 
of the nuculid bivalve Acila H. Adams & A. Adams, 
1858, in the region extending from the Queen Charlotte 
Islands, British Columbia, Canada southward to the 
northern part of Baja California, Mexico (Figure 1). 
Schenck (1936) did a detailed study of Cretaceous to Re- 
cent specimens of Acila from the Pacific slope of North 
America, but his emphasis was on Cenozoic species be- 
cause they had been better collected, both as to number 
of specimens and stratotype placement. Schenck (1943) 
added more information about some Cretaceous species. 
In the last 60 years, knowledge of Pacific slope of North 
America Cretaceous stratigraphy has increased signifi- 
cantly, and much more collecting has been done. This 
present investigation, which greatly expands on 
Schenck’s work, is based on collections borrowed from 
all the major museums having extensive collections of 
Cretaceous fossils from the study area. We detected 122 
lots (72 = LACMIP, 26 = CAS, 15 = UCMP, 9 = other), 
containing a total of 868 specimens of Acila. Our work 
establishes a documentable paleontologic record of Trun- 
cacila from late Aptian to early late Maastrichtian on the 
Pacific slope of North America (Figure 2), with the high- 
est diversity (four species) occurring during the latest 
Campanian to early Maastrichtian. 

Acila lives today in the marine waters of the Pacific 


and Indo-Pacific regions and is a shallow-burrowing de- 
posit feeder. Like other nuculids, it lacks siphons but has 
an anterior-to-posterior water current (Coan et al., 2000). 
It is unusual among nuculids, however, in that it com- 
monly inhabits sandy bottoms. Although is does not have 
a streamlined shell, it is a moderately rapid burrower be- 
cause of its relatively large foot (Stanley, 1970). Acila 
has a very distinctive divaricate ornamentation, and, al- 
though this type of ornamentation is uncommon among 
bivalves, it “‘shows widespread taxonomic distribution, 
brought about through adaptive convergence” (Stanley, 
1970:65). 

Recent Acila has a considerable tolerance for temper- 
ature ranges, from cold to tropical waters, but the greatest 
number of specimens comes from temperate waters 
(Schenck, 1936). One example of having this eurythermal 
adaptability is Acila (Truncacila) castrensis (Hinds, 
1843), known to range from the cold waters of Kam- 
chatka and the northeastern Bering Sea into the tropical 
waters of the Golfo de California, Baja California Sur, 
Mexico (Coan et al., 2000). Cretaceous Acila in the study 
area lived mostly during warm-ocean periods. The Aptian 
fauna of the Alisitos Formation of northern Baja Califor- 
nia is wholly tropical in aspect. Warm-temperate water 
conditions existed during the Albian to Turonian in the 
study area. Some cooling took place from the Coniacian 
to early Maastrichtian, but the faunas that lived during 


Index map showing locales mentioned in text. | 
Skidegate Inlet, Queen Charlotte Islands. 2 = Hornby and Den- 
Nanaimo area. 4 = Chemainus River and 
5 = Mitchell and Antone areas. 6 
= Ono. 9 = Redding area. 10 = Chico 
= Sites. 13 = Franklin Canyon. 14 = 


Saltspring Island areas. 
Phoenix. 7 = Yreka. 8 


The Veliger, Vol. 48, No. 2 


this time also contain warm-water elements. There was a 
warming trend during the late Maastrichtian (Saul, 
1986a). 

Recent Acila also has a considerable depth range, from 
below the intertidal zone (5 m) into the bathyal zone (400 
m) (Schenck, 1936:34, fig. 10; Coan et al., 2000). There 
are many shallow-water marine occurrences of Creta- 
ceous Acila in the study area (e.g., Alisitos Formation, 
Pentz Road member of the Chico Formation, and Jalama 
Formation), but deeper water occurrences are equivocal, 
largely because of lack of detailed depositional-environ- 
ment studies on beds containing Acila specimens. Based 
on a survey of the literature, it seems that the Moreno 
Formation (see Stratigraphy) has the best potential of 
containing relatively deep-water occurrences of Acila, but 
detailed studies are needed to confirm this assertion. 

Sundberg (1980, 1982) defined an Inoceramus-Acila 
paleocommunity, which included the bivalves Propea- 
mussium and ‘‘Parallelodon,”’ as well as the scaphopod 
Dentalium, that occupied most of the Holz Shale Member 
of the Ladd Formation, Santa Ana Mountains, Orange 
County, southern California. He believed that this paleo- 
community probably existed in restricted lagoonal waters, 
at depths between 0 and 100 m. Almgren (1973), on the 
basis of benthic foraminifera, however, reported that the 
major part of the Holz was deposited in slope depths. Saul 
(1982), on the basis of gastropods and bivalves, reported 
that the lower Holz was deposited in middle to outer shelf 
depths and that the upper Holz was deposited in outer to 
shallow shelf depths. 

The earliest documented records of Acila are Acila 
(Truncacila) schencki Stoyanow, 1949 [not Acila schen- 
cki Kuroda in Kira, 1954:83, 155-156, pl. 41, fig. 6], 
from the upper Aptian Pacheta Member of the Lowell 
Formation, southeastern Arizona and Acila (Truncacila) 
allisoni, sp. nov. from the upper Aptian, lower part of the 
Alisitos Formation, Baja California, Mexico. 

Acila (T.) bivirgata (J. de C. Sowerby, 1836) is the 
name that has been most commonly applied to Aptian- 
Albian specimens of Aci/a found anywhere in the world. 
The type locality of Sowerby’s species is in southeastern 
England, in rocks correlative to the lower Albian am- 
monite Douvilleiceras mammilatum Zone (Casey, 1961: 
605). Schenck’s (1936:35, 47) reports of Acila (T.) bivir- 
gata in the Aptian of Tunisia and Morocco, the Aptian- 
Albian of eastern Venezuela (also see Schenck, 1935a), 
and the Albian of France and Morocco all need confir- 


ce 


Mount Diablo and Corral Hollow Creek. 15 = Garzas Creek. 16 
= Charleston School Quadrangle area. 17 = Panoche. 18 = Lake 
Nacimiento. 19 = North Shale Hills. 20 = Jalama Creek. 21 = 
Simi Hills. 22 = Santa Ana Mountains. 23 = Carlsbad. 24 = 
Punta Banda. 25 = Punta China and Punta San Jose. 26 = San 
Antonio del Mar. 27 = Arroyo Santa Catarina. 


R. L. Squires & L. R. Saul, 2005 


120(my.) 115 110 105 100 95 


LOWER CRETACEOUS 


Aptian Albian Cenomanian | Turonian Campanian Maastrichtian 


allisoni (A 


Fe aE ec 
C34 ————__ ——— C33 —_ €311C30 
demessa 


haidana 


AS SWRI 


n. Sp.? | ? EERE ? 


Figure 2. 
(black = 


mation as to geologic age. Until this verification is done, 
global-migration routes of the earliest Acila (Truncacila) 
cannot be worked out. 

Most of the study area specimens that have been men- 
tioned in faunal lists or found in major museums have 
been identified as Acila (Truncacila) demessa Finlay, 
1927, even though some of them belong to other species. 
Our study revealed that A. (7.) demessa ranges from late 
Turonian to late late Campanian and possibly early Maas- 
trichtian, an interval of approximately 18 million years, 
thereby making it the longest ranging of the Cretaceous 
Acila (Truncacila) species in the study area. Such long 
ranges are not unusual for Acila; for example, Acila 
(Truncacila) hokkaidoensis (Nagao, 1932) from the Cre- 
taceous Himenoura Group in Kyushu, Japan, ranges from 
Coniacian to Maastrichtian (Tashiro, 1976), an interval of 
approximately 19 million years. 

Our study has refined also the geographic and strati- 
graphic ranges of the other two previously named study 
area species: Acila (Truncacila) haidana Packard in 
Schenck, 1936 and Acila (Truncacila) princeps Schenck, 
1943. In addition, we discovered three new species and 
one possible new species. 

Umbonal angle refers to the angle of divergence of the 
antero-umbonal and postero-umbonal surfaces, with the 
sides of the angle drawn to obtain maxiumum tangenti- 
ality with the valve surfaces. The umbonal-angle mea- 
surements were made from photographs of specimens. 
Although drawing the postero-umbonal part of the angle 
is easy because this surface is usually fairly straight, 
drawing the antero-umbonal part of the angle was usually 
subject to variation because this surface is usually con- 
vex. Chevron-angle measurements were also made using 
photographs of specimens, and measurements were taken 
near the point of divarication of the ribs, on approxi- 
mately the medial part of the disk. It makes a significant 
difference where one measures this angle, because the 


—_;—-- 


nee 85 80 75 70 
| pre et | | | 


UPPER CRETACEOUS 


| [Lower Middle Lower |Upper 
Alea ae i | 


rosaria (LET 


princeps frst] 
ae] 


Chronostratigraphic positions of the new and restudied Acila (Truncacila) species. Geologic ages, geomagnetic polarities 
normal, white = reversed), and chrons from Gradstein & Ogg (2004:fig. 2). 


sides of the chevron angle becomes increasingly wider 
ventrally. In this study, the imaginary line bisecting the 
chevron angle is used as a reference point and referred 
to as a bisecting line. 

In this study, shell size, rib width, and rib interspace 
width are all denoted by relative terms pertaining to sub- 
genus Truncacila Grant & Gale, 1931. Rib width and rib 
interspace information, furthermore, pertain only to the 
area posterior to the line bisecting the chevrons on the 
disk area of adult specimens. Umbo and ventral margin 
areas posterior of the bisecting line are excluded. In the 
case of multiple chevrons, the rib-width and rib-inter- 
space information pertain to the area posterior of the line 
bisecting the posteriormost chevron. 

The suprageneric classification system used here fol- 
lows that of Coan et al. (2000). Abbreviations used for 
catalog and locality numbers are: ANSP, Academy of 
Natural Sciences, Philadelphia; CAS, California Acade- 
my of Sciences, San Francisco; GSC, Geological Society 
of Canada, Ottawa; LACMIP, Natural History Museum 
of Los Angeles County, Invertebrate Paleontology Sec- 
tion; LSJU, Stanford University, California (collections 
now housed at CAS); RBCM, Royal British Columbia 
Museum, Victoria, UCMP, University of California Mu- 
seum of Paleontology, Berkeley; UO, University of 
Oregon, Eugene. 


STRATIGRAPHY AND DEPOSITIONAL 
ENVIRONMENTS 


The geologic ages and depositional environments of most 
of the formations and members cited in this paper have 
been summarized by Squires & Saul (2001, 2003a, b, c 
d, 2004a, b). Stratigraphic and depositional-environment 
information mentioned below concerns those rock units 
not discussed in recent literature. The stratigraphic units 
are listed from oldest to youngest. 


Page 86 


Hudspeth Formation 


This formation crops out in the Mitchell area, Wheeler 
County, northeast-central Oregon (Figure 1, locale 5) and 
consists mainly of marine mudstone (Wilkinson & Oles, 
1968). The type locality of Acila (T.) sp. nov.? plots on 
the geologic map of Wilkinson & Oles (1968:fig. 1) in 
the lower part of the ““Main Mudstone member”’ of the 
Hudspeth Formation. Based on ammonites, Wilkinson & 
Oles (1968) reported the age of this part of the formation 
to be early or early middle Albian. There have been no 
detailed studies of the depositional environments of this 
formation. 


Haida Formation 


This formation crops out in the central part of the 
Queen Charlotte Islands, northern British Columbia (Fig- 
ure 1, locale 1) and consists of two members, which ac- 
cumulated as part of the same transgression event. The 
two members, a nearshore sandstone member and an 
overlying mostly outer shelf shale member, are laterally 
equivalent and interfinger. Storm deposits, which char- 
acterize the sandstone member, are also found in the shale 
member and are represented by fine- to medium-grained 
sandstone with associated shell lags (McLearn, 1972; 
Haggart, 1991a). The type locality of Acila (Trunacila) 
haidana Packard in Schenck, 1936, was reported to be a 
beach-cliff exposure of the Haida Formation, and utiliz- 
ing the geologic map of Haggart (199 1a:fig. 3), this ex- 
posure would seem to plot in the shale member. 
Schenck’s (1936:51) description of the type locality 
“about | mile east of Queen Charlotte City,’ however, 
is not precise and could refer to outcrops in either the 
shale member or the sandstone member, depending on if 
one uses as a Starting point the old hotel or the current 
post office in Queen Charlotte City, respectively (J. Hag- 
gart, personal communication). No Acila has been found 
by recent collecting in the sandstone member, and, con- 
sequently, Schenck’s material probably came from the 
lower part of the shale member (J. Haggart, personal 
communication). The type specimens of A. (7.) haidana 
occur in fine-grained sandstone, and the holotype consists 
of conjoined valves. If these type specimens are part of 
a storm lag, then the amount of post-mortem transport 
was not great. All indications are that these specimens 
probably lived in a transitional nearshore to slightly deep- 
er environment. This would be in keeping with the shal- 
low-water environments of localities in the study area at 
which additional specimens of this species are found. 

The sandstone member of the Haida Formation is Al- 
bian in age, based on a rich assemblage of ammonites 
(McLearn, 1972), and the shale member ranges from lat- 
est Albian to Cenomanian to early Turonian in age, based 
on scarce remains of inoceramid bivalves (McLearn, 
1972; Haggart, 1987, 1991a). The exposures at the type 
locality of A. (7.) haidana, however, are probably latest 


The Veliger, Vol. 48, No. 2 


Albian to Cenomanian (J. Haggart, personal communi- 
cation). 

The Queen Charlotte Islands and Vancouver Island, 
which is mentioned later in this paper, are parts of an 
amalgamated sequence of tectonic terranes, collectively 
called the Insular Superterrane, whose accretional history 
is currently in dispute. Two mutually contradictory hy- 
potheses deal with this accretionary history, and both 
have been summarized by Cowan et al. (1997) and Ward 
et al. (1997). One hypothesis suggests that the Insular 
Superterrane was already in place in its current position 
(more or less) relative to western North America by the 
Cretaceous and perhaps earlier. The second hypothesis, 
known as the ‘‘Baja BC hypotheses,’ suggests that the 
superterrane was situated 3000 km south of its present 
position. Kodama & Ward (2001), using paleomagnetic 
paleolatitudinal distribution of bivalve rudists, suggested 
that Baja BC was no farther south than 40°N (.e., north- 
ern California) in the Late Cretaceous. The distribution 
of Acila (T.) haidana supports the contention that the In- 
sular Superterrane was not any farther south than northern 
California during the Cretaceous, because besides being 
found in the Haida Formation, this species is only known 
elsewhere from southern Oregon and northern California. 


Upper Cedar District Formation, West Shoreline 
of Denman Island 


Both A. (T.) demessa and A. (Truncacila) grahami, sp. 
nov., occur in mudstone exposed in an intertidal bench at 
Locality 4 on the west-central shoreline of Denman Is- 
land, off the east coast of Vancouver Island, British Co- 
lumbia (Figure 1, locale 2). The latest geologic map of 
this island shows these exposures to be part of the Cedar 
District Formation of the Nanaimo Group (Katnick & 
Mustard, 2001). Mustard et al. (2003) reported that this 
formation along the west side of Denman Island consists 
of proximal-turbidite deposits in lower and middle sub- 
marine-fan complexes. Mustard (1994:table A6) reported 
that megafossils found in these turbidite deposits include 
resedimented shallow-water taxa. All the acilid specimens 
collected from Locality 4 are single valves, and although 
this suggests that they might have been resedimented, 
taphonomic studies are needed. 

Mustard et al. (2003:127) reported that molluscan fos- 
sils found locally in the Cedar District Formation on the 
west side of Denman Island indicate a late Campanian 
age. Mollusks found at Locality 4 include the ammonites 
Metaplacenticeras cf. pacificum (Smith, 1900) and Des- 
mophyllites diphylloides (Forbes, 1846). The Metaplacen- 
ticeras pacificum biozone is of late middle to early late 
Campanian age (Elder & Saul, 1996:fig. 1), and the geo- 
logic range of D. diphylloides is “‘relatively long, cov- 
ering most of the Campanian’? (Matsumoto, 1959:10). 
The Cedar District Formation ranges in age from early to 
middle late Campanian (Jeletzky, 1970; Ward, 1978; 


R. L. Squires & L. R. Saul, 2005 


Haggart, 1991b), therefore, the strata at Locality 4 belong 
to the upper part of this formation. Enkin et al. (2001: 
figs. 3, 4) took paleomagnetic samples from the imme- 
diate vicinity of Locality 4 and determined that these 
samples represent sediments deposited sometime during 
the 33 N (normal) polarity interval, which is equivalent 
to the middle to early late Campanian (see Figure 2). 
Based on the molluscan and paleomagnetic data, there- 
fore, the age of the fossils at Locality 4 can be assigned 
a late middle to early late Campanian age. 


Moonlight Formation? 


A few specimens of Acila spp. were detected in two 
collections made from muddy siltstones exposed in a 
small area on the north side of Shale Hills, southwest side 
of Antelope Valley, eastern Temblor Range, Kern County, 
south-central California (Figure 1, locale 19). CAS loc. 
1552 yielded a specimen of Acila (Truncacila) rosaria, 
sp. nov., and a specimen of A. (T.) grahami. CAS loc. 
69095 yielded another specimen of Acila (T.) rosaria. 
These muddy siltstones were mapped by English (1921: 
pl. 1), who described them as being a soft clay shale. 
They are most likely correlative to the shallow-marine 
siltstone facies of the Moonlight Formation, which crops 
out on the other side of Antelope Valley (Marsh, 1960: 
pl. 1). This facies, which is soft and clayey, closely re- 
sembles the rocks described by English. Matsumoto 
(1959:11; 1960:63) noted that the ammonite Baculites rex 
Anderson, 1958, is found at CAS loc. 1552, and this bio- 
zone is early late Campanian in age (Elder & Saul, 1996: 
fig. 1). 


Northumberland Formation at Collishaw Point, 
North End of Hornby Island 


The type locality of Acila (T.) grahami occurs in mud- 
stone exposed in an intertidal bench at Locality 3 at Col- 
lishaw Point, north end of Hornby Island, off the east 
coast of Vancouver Island, British Columbia (Figure 1, 
locale 2). The latest geologic work done on the Collishaw 
Point outcrops is that of Katnick & Mustard (2001, 2003) 
and Mustard et al. (2003). These workers assigned the 
mudstone in question to the Northumberland Formation 
of the Nanaimo Group. In Mustard et al. (2003:figs. 23, 
24), Collishaw Point is also mentioned as a field-trip stop, 
and reports dealing with the fossils (including ammonites, 
inoceramids, and shark teeth) from this locale have been 
summarized by these authors. The beds there consist of 
silty mudstones intercalated with less common sandstone 
beds of turbidite origin. The A. (T.) grahami material is 
from a “thin lens of what appears to be a debris flow 
containing abundant shell fragments, numerous and di- 
verse shark teeth, and rare bird bones” (R. Graham, per- 
sonal commun.). No studies have been done yet on the 
depositional environment or of the taphonomy of the fos- 
sils found in this particular lens. All the specimens of A. 


Page 87 


(7.) grahami are single valves, and they appear to be 
unabraded. 

In spite of the presence of ammonites and inoceramids 
in the beds at Collishaw Point, there is no consensus on 
the age of these beds. As summarized by Mustard et al. 
(2003), the age has been variously reported as either latest 
Campanian or early Maastrichtian, and further work is 
needed to resolve this age disagreement. 

As mentioned under the discussion of the Haida For- 
mation, the amount of tectonic displacement that Van- 
couver Island (which is part of the Insular Superterrane) 
has undergone is controversial. As summarized by Enkin 
et al. (2001), sedimentologic and paleontological evi- 
dence, as well as some paleomagnetic studies (Kodama 
& Ward, 2001), indicate that the Nanaimo Group of Van- 
couver Island was deposited near its present northern po- 
sition, whereas other paleomagnetic studies indicate that 
these sediments were deposited near the modern-day lo- 
cation of Baja California (Enkin et al., 2001). 


Moreno Formation 


This formation crops out along the western side of the 
San Joaquin Valley, central California (Figure 1, locales 
15 and 16) and is a clastic sedimentary sequence that 
records the shoaling of the central San Joaquin basin from 
deep water to shelf depths. The formation, which is time- 
transgressive (Saul, 1983), consists of four members that 
span an interval from the Maastrichtian through early 
Danian (Paleocene) (McGuire, 1988). Members revelant 
to this report are the Tierra Loma and the supradjacent 
Marca Shale; both are discussed below. 


Tierra Loma Member 


This member, which crops out south of Los Banos, 
southwestern Merced County, California, consists mainly 
of muddy siltstones and turbidites containing irregularly 
interbedded, channelized sandstones (McGuire, 1988). 
One of these channelized sandstones, approximately in 
the middle of the Tierra Loma Member, was referred to 
by Schenck (1943) and Payne (1951) as the Mercy sand- 
stone lentil. The type locality of A. (7.) princeps occurs 
within this lentil, and this locality was plotted on geologic 
maps by Schenck (1943:fig. 1) and by Payne (1951:fig. 
2). 

Acila (T.) rosaria also occurs in the Tierra Loma Mem- 
ber, and deposition of this member took place in an ox- 
ygen-deficient, lower to upper slope environment (Mc- 
Guire, 1988). Specimens of this bivalve occur as a few 
single valves. Detailed work is needed to determine if 
these specimens are in situ or have undergone post-mor- 
tem transport from a shallower water environment. 

Saul (1983) and Squires & Saul (2003a) discussed the 
geologic age of the Tierra Loma Member, which is late 
early to early late Maastrichtian age, based on turritellas, 
bivalves, and ammonites. 


Page 88 


The Veliger; Vol. 435 Now 


Marca Shale Member 


This member crops out for a distance of approximately 
20 km (in northwestern Fresno County) southward of 
where the Mercy sandstone lentil (see above) lenses out. 
The Marca Shale Member gradationally overlies the Ti- 
erra Loma Member and consists of 80 to 95 m of finely 
laminated siliceous shale and diatomaceous shale that ac- 
cumulated in a gently inclined, upper slope environment 
under intense anoxic conditions associated with an up- 
welling system (McGuire, 1988). According to Payne 
(1951), at the top and bottom of this member, there are 
white, hard, calcareous concretions containing a few 
poorly preserved megafossils. A few specimens of Acila 
(T.) grahami have been collected from the Marca Shale 
Member. Only one specimen (Figure 32) is conjoined, 
and it is in a matrix of diatomaceous shale. It is unlikely 
that this specimen underwent any post-mortem transport 
by means of a turbidity current, because, according to 
McGuire (1988), there is a complete absence of any sand- 
stone or other coarse terrigenous sediment in the Marca 
lentil. This absence indicates that the slope environment 
on which this unit accumulated was isolated from the 
source(s) of sands found in all other members of the Mo- 
reno Formation. 

According to Saul (1983:fig. 10), the Marca Shale con- 
tains the ammonite Trachybaculites columna (Morton, 
1834). This ammonite, which is an intracontinental zonal 
indicator of late early to early late Maastrichtian age 
(Cobban & Kennedy, 1995), also occurs in the underlying 
Tierra Loma Shale (see Squires & Saul, 2003b). Although 
the age of the Marca Shale is approximately the same age 
as that of the Tierra Loma Member, the Marca Shale is 
slightly younger because of its stratigraphic position. 


Panoche Formation at Franklin Canyon 


This formation crops out in Franklin Canyon in the 
Franklin Ridge area (Dibblee, 1980) just west of Marti- 
nez, Contra Costa County, northern California (Figure 1, 
locale 13). Weaver (1953) provided a faunal list of mol- 
lusks found in these rocks, and at a few localities he listed 
“Acila (T.) demessa”’ in association with the bivalve 
Meekia sella Gabb, 1864. Saul (1983:fig. 4) showed 
Meekia sella to range from early to late Maastrichtian (67 
Ma), but not into the latest Maastrichtian. The only spec- 
imen of Acila we were able to find in any museum col- 
lection that was derived from this area was Schenck’s 
(1943) specimen (hypotype CAS 69086.02) of Acila sp. 
D. This specimen is identified herein as A. (7.) princeps 
and is illustrated in Figure 46. 


El Piojo Formation 


This formation crops out in the vicinity of Lake Na- 
cimiento, San Luis Obispo County, west-central Califor- 
nia (Figure 1, locale 18) and consists mainly of sandstone 


(Seiders, 1989). No detailed depositional-environment 
studies have been done on this formation. Although mol- 
luscan fossils are uncommon in this formation, Saul 
(1986b) studied the mollusks from LACMIP loc. 30141 
and reported them to be of early late Maastrichtian age, 
including a single specimen of Acila sp. Additional clean- 
ing of this specimen revealed it to be Acila (Truncacila) 
princeps. 


Deer Valley Formation 


Two specimens of Acila (Truncacila) princeps were 
detected in the LACMIP collection from very fine- 
grained sandstone in Deer Valley on the north flank of 
Mount Diablo, Contra Costa County, northern California 
(Figure 1, locale 14). This sandstone is in Colburn’s 
(1964) informal Deer Valley formation, which, according 
to him, was deposited in a nearshore, above wave base, 
open-ocean environment. Colburn (1964) also mentioned 
the presence of A. (7.) princeps in this formation. Based 
on the presence of the bivalves Meekia sella Gabb, 1864, 
and Calva (Calva) varians (Gabb, 1864), this sandstone 
can be assigned to the upper Maastrichtian (Saul & Po- 
penoe, 1962, 1992). 


SYSTEMATIC PALEONTOLOGY 
Phylum MOLLUSCA Linnaeus, 1758 
Class BIVALVIA Linnaeus, 1758 
Order NUCULOIDEA Dall, 1889 
Superfamily NUCULOIDEA J. E. Gray, 1824 
Family NUCULIDAE J. E. Gray, 1824 
Genus Acila H. Adams & A. Adams, 1858 


Type species: Nucula divaricata Hinds, 1843, by sub- 
sequent designation (Stolickza, 1871); Recent, China. 


Discussion: Like other nuculids, Aci/a has a posteriorly 
truncate, nacreous shell with opisthogyrate beaks, and an 
internal ligament in a resilifer. Three subgenera have been 
named: Acil/a sensu stricto, which ranges from Oligocene 
to Recent (Keen, 1969); Lacia Slodkevich, 1967, which 
ranges from late Eocene to late Pliocene (Slodkevich, 
1967); and Truncacila Grant & Gale, 1931, which ranges 
from Early Cretaceous (late Aptian) to Recent (Schenck, 
1936). Acila s.s. is characterized by large size, well-de- 
fined rostral sinus, a rostrate (protruding) posterior end, 
and strong divaricate ornamentation (Schenck, 1935b; 
Keen, 1969; Slodkevich, 1967; Addicott, 1976; Coan et 
al., 2000). Lacia is characterized by a very poorly defined 
rostral sinus. The characteristics of Truncacila are men- 
tioned below. 


R. L. Squires & L. R. Saul, 2005 


Page 89 


Table | 


Check list of key morphologic characters used in differentiating the studied species. 


Other* 


#Ribs/ 

valve Divarication 
Species Shell size (approx.) on venter 
allisoni small 55 central 
n. sp.? medium 55 anterior 
haidana medium 40 usually central 
demessa medium 70 anterior 
grahami small 50 usually anterior 
rosaria medium 80 anterior 
princeps large 85 anterior 


roundly subquadrate: ribs very narrow, interspaces approximately ), as 
wide; escutcheonal ribs continuous with ribs on disk 

quadrate; ribs narrow, interspaces approximately ¥, as wide 

usually subquadrate; ribs very narrow to narrow, interspaces /, approxi- 
mately , as wide to same width as ribs 

ribs flat and very narrow to moderately wide, interspaces approximately 
¥; to /, as wide: escutcheonal area bounded by smooth groove 

can be trigonal; ribs narrow to moderately wide, interspaces approxi- 
mately ’, to 4 as wide; escutcheonal ribs continuous with ribs on 
disk 

shell weakly rostrate postero-ventrally; ribs very narrow to narrow, in- 
terspaces approximately Y, as wide to same width as ribs; escutcheon 
bounded by flattish to shallowly grooved area usually crossed by ribs 
not continuous with ribs on disk 

subquadrate, rarely trigonal: ribs flat and narrow to wide, interspaces ap- 
proximately 4 to Y, as wide 


* Rib and interspace information pertains only to the area posterior to chevron-bisecting line on adult specimens: umbo and ventral- 


Margin regions are excluded. 


Subgenus Truncacila Grant & Gale, 1931 


Type species: Nucula castrensis Hinds, 1843, by original 
designation; Pliocene to Recent, northeastern Pacific. 


Discussion: Truncacila is characterized by small size, 
relative to other acilids, and an absence of a rostral sinus 
(Slodkevich, 1967; Coan et al., 2000). Although Trun- 
cacila has been reported as lacking a rostrate posterior 
end (Slodkevich, 1967: Coan et al., 2000), it can have a 
small rostration at the point of meeting of the ventral and 
posterior margins (Stoyanow, 1949:62). Acila (T.) rosaria 
has such a rostration. So do some of the subquadrate 
forms of A. (T.) demessa and A. (T.) grahami, as well as 
the best preserved specimens of A. (T7.) princeps. 

The key characters of the studied species are given in 
Table 1. 


Acila (Truncacila) allisoni Squires & Saul, 
sp. Nov. 


(Figures 3-8) 


Acila (Truncacila) bivirgata (Sowerby). Allison, 1974:tables 
4, 6, 7. 

Not Acila (Truncacila) bivirgata (J. de C. Sowerby, 1836: 
335, pl. 11, fig. 8). 


Diagnosis: Shell small, roundly subquadrate. Chevrons 
bisected by line meeting center of ventral margin. Total 
number of ribs on disk of each valve approximately 55; 
ribs (posterior of chevron-bisecting line) very narrow, 
with interspaces approximately % as wide. Escutcheonal 
ribs continuous with ribs on disk. 


Description: Shell small for subgenus (up to 12.1 mm in 
height and 15.5 mm in length), longer than high, height/ 
length ratio = 0.78. Roundly subquadrate, inequilateral, 
equivalved, valves moderately inflated. Anterior end 
broadly rounded. Antero-dorsal margin long and straight. 
Posterior margin truncate and set off from escutcheon by 
moderately strong rostration. Ventral margin convex. Um- 
bones low, located posteriorly; umbonal angle 98 to 116°. 
Beaks pointed, incurved, opisthogyrate. Disk broad, or- 
namented with abundant ribs diverging from umbo area 
and forming chevron-shaped (divaricate) pattern. Chev- 
ron angle 38 to 47°. Chevrons bisected by line extending 
from slightly anterior of umbo to center of ventral mar- 
gin; ribs anterior to bisecting line 23 to 34; ribs posterior 
to bisecting line 24 to 33 (excluding occasional short bi- 
furcations near ventral margin). Total number of ribs on 
disk of each valve usually approximately 55; ribs very 
narrow with interspaces approximately 4% as wide, except 
anterior of chevron-bisecting line, where ribs become 
slightly wider, occasionally wavy, and more widely 
spaced. Growth checks irregularly spaced from medial 
part of disk to ventral margin. Escutcheon moderately 
prominent, slightly sunken, and bounded by shallow 
groove crossed by very narrow ribs continuous with ribs 
on disk; ribs stronger (approximately same strength as 
those on disk) on elevated central part of escutcheonal 
area. Hinge with at least 14 anterior taxodont teeth and 
11 posterior taxodont teeth. Resilifer opisthocline, nar- 
row. 


Dimensions of holotype: Conjoined valves (partial right 


Page 90 The Veliger, Vol. 48, No. 


% 16 
Explanation of Figures 3 to 17 


Figures 3-8. Acila (Truncacila) allisoni Squires & Saul, sp. nov., rubber peels. Figure 3. Holotype UCMP 154232, 
UCMP loc. B-5665, left valve, 2.8. Figure 4. Paratype UCMP 154233, UCMP loc. B-5665, left valve, <3.2. 
Figure 5. Paratype UCMP 154234, UCMP loc. A-6275, right valve, X2.8. Figure 6. Holotype UCMP 154232, 
UCMP loc. B-5665, posterior view, 3. Figure 7. Paratype UCMP 154233, UCMP loc. B-5665, posterior view of 


R. L. Squires & L. R. Saul, 2005 


valve), height 12.1 mm, length 15.5 mm (incomplete), 
thickness 7.8 mm (approximate). 


Holotype: UCMP 154232. 


Type locality: UCMP B-5665, near Punta China, Baja 
California, Mexico, 31°30’N, 116°40’W. 


Paratypes: UCMP 154233, 154234, 154235. 
Geologic age: Late Aptian. 


Distribution: Alisitos Formation, Baja California, Mex- 
ico. 


Discussion: The above description of the new species is 
based on eight rubber peels: one left valve, three right 
valves, two with conjoined valves, and two partial hinges. 

The new species is most similar to Acila (Truncacila) 
bivirgata (J. de C. Sowerby, 1836:335, pl. 11, fig. 8) from 
upper Aptian strata of England. The similarity is close 
enough for Allison (1974) to have identified as Sowerby’s 
species specimens from the Alisitos Formation. Illustra- 
tions (Figures 9-11) of A. (7.) bivirgata are herein pro- 
vided for comparison, and this is the same specimen used 
in Schenck (1936:47, pl. 2, figs. 1, 2). The new species 
differs from A. (T.) bivirgata by having the line bisecting 
the chevrons located nearer the center of the ventral mar- 
gin, slightly wider ribs, narrower interspaces, and a less 
sunken escutcheon. 

The new species differs from Acila (T.) schencki Stoy- 
anow (1949:61—63, pl. 8, figs. 1-8), the only other Aptian 
acilid known from western North America, by having 
more numerous and narrower ribs (especially on the an- 
terior half of the disk), no tendency for the line bisecting 
the chevrons to be slightly anterior of the center of the 
ventral margin, and an absence of strong curvature dor- 
sally of the ribs near the anterior edge of the disk. 


Etymology: Named for the late E. C. Allison, in recog- 
nition of his extensive collecting of mollusks from the 
Alisitos Formation. 
Acila (Truncacila), sp. nov.? 
(Figure 12) 
Acila (Truncacila) sp. A. Schenck, 1936:51, pl. 2, fig. 13. 


Diagnosis: Shell medium, quadrate. Chevrons bisected 
by line meeting-ventral margin near meeting of anterior 


Page 91 


end and ventral margin. Total number of ribs on disk of 
left valve approximately 55; ribs (posterior of chevron- 
bisecting line) narrow, with interspaces approximately % 
as wide. 


Description: Shell medium for subgenus (14.2 mm in 
height and 21.2 mm in length), longer than high, height/ 
length ratio = 0.67. Quadrate, inequilateral, equivalved, 
valves moderately inflated. Anterior end broadly rounded. 
Antero-dorsal margin long and straight, generally parallel 
to ventral margin. Posterior end straight, truncate. Um- 
bones low, located posteriorly; umbonal angle 100°. Disk 
broad, ornamented with abundant ribs diverging from 
umbo area and forming chevron-shaped (divaricate) pat- 
tern. Chevron angle 55°. Chevrons bisected by line ex- 
tending from slightly anterior of umbo to point located 
near where anterior end and ventral margins meet; ribs 
anterior to bisecting line about 21; ribs posterior to bi- 
secting line about 34 (excluding occasional short bifur- 
cations near ventral margin). Total number of ribs on disk 
usually approximately 55; ribs narrow with interspaces 
approximately % as wide, except anterior of chevron-bi- 
secting line, where ribs become more widely spaced. 


Geologic age: Early Albian or early middle Albian, pos- 
sibly Cenomanian. 


Distribution: POSSIBLY LOWER ALBIAN: Budden 
Canyon Formation, upper lower Chickabally Mudstone 
Member, Ono area, Shasta County, northern California. 
LOWER ALBIAN OR LOWER MIDDLE ALBIAN: 
Hudspeth Formation, lower part of “‘Main Mudstone 
member,”’ near Mitchell, Wheeler County, northeast-cen- 
tral Oregon. POSSIBLY CENOMANIAN: Unnamed stra- 
ta, near Antone, Wheeler County, northeast-central 
Oregon. 


Discussion: The possible new species is known only 
from a single specimen (hypotype CAS 69097 = UO 
6000), a left valve (height 14.2 mm, length 21.2 mm), 
the posterior end of which is not preserved. This hypo- 
type is the only moderately well preserved specimen of 
Acila of Albian age known from the study area. It is like- 
ly that this species is new, but until more specimens are 
discovered, we are reluctant to name it. 

A possible record of A. (7.) sp. nov.? is a latex peel of 
a fragment from CAS loc. 69110 in the upper lower 
Chickabally Mudstone Member of the Budden Canyon 


left valve, X4. Figure 8. Paratype UCMP 154235, UCMP loc. A-6275, right-valve hinge, *3.7. Figures 9-11. Acila 
(Truncacila) bivirgata (J. de C. Sowerby, 1836), CAS hypotype 5770, Gault Formation, Folkestone, England, 3.7. 
Figure 9. Left valve. Figure 10. Right valve. Figure 11. Posterior view. Figure 12. Acila (Truncacila) sp. nov.?, 
hypotype CAS 69087, UO loc. 461, left valve, x 1.8. Figures 13—17. Acila (Truncacila) haidana Packard in Schenck, 
1936, CAS loc. 69080. Figure 13. Holotype CAS 69081, left valve, 3. Figure 14. Paratype CAS 69080.01, left 
valve, X2.8. Figure 15. Hypotype LACMIP 13227, LACMIP loc. 24365, right valve, x3.4. Figure 16. Holotype 
CAS 69081, posterior view, <3. Figure 17. Hypotype CAS 69106.03, LACMIP loc. 23950, partial mght-valve 


hinge, 4.8. 


Page 92 


Formation in the Huling Creek area, southwest of Redd- 
ing, Shasta County, northern California. Jones et al. 
(1965) assigned these rocks to the early Albian. Another 
possible record of A. (7.) sp. nov.? is a plastic replica of 
a partial specimen from unnamed strata at UCMP loc. 
814 south of Antone, between Rock Creek and Spanish 
Gulch, Wheeler County, northeast-central Oregon. Popen- 
oe et al., (1960:column 54 of chart 10e) assigned rocks 
from this area to the Cenomanian. 

Acila (T.) sp. nov.? is similar to A. (7.) rosaria but 
differs by having a truncate posterior end, usually slightly 
wider ribs, and slightly wider spaced ribs. Acila (T.) sp. 
nov.? is somewhat similar to A. (7.) allisoni but differs 
by having a larger size, more widely spaced ribs that are 
never wavy, uniform-rib strength over the entire disk, and 
chevrons bisected by a line located anterior of center of 
ventral margin. 


Acila (Truncacila) haidana Packard 
in Schenck, 1936. 


(Figures 13-17) 


Acila (Truncacila) demessa Finlay, var. haidana Packard in 
Schenck, 1936:50—51, pl. 2, figs. 3, 4, 6, 10. 
?Nucula (Acila) truncata Gabb. Whiteaves, 1884:232. 


Diagnosis: Shell small, subquadrate (usually) to elliptical. 
Chevrons bisected by line usually meeting center of ven- 
tral margin (rarely to anterior of center). Total number of 
ribs on disk of each valve approximately 40; ribs (pos- 
terior of chevron-bisecting line) very narrow to narrow, 
with interspaces %4 as wide to same width as ribs. 


Description: Shell small for subgenus (up 14.4 mm in 
height and 16.7 mm in length), longer than high, height/ 
length ratio = 0.73 to 0.86. Subquadrate (usually) to el- 
liptical, inequilateral, equivalved, valves moderately in- 
flated. Antero-dorsal margin long, straight to lowly con- 
vex. Posterior end truncate and set off from escutcheon 
by weak rostration. Ventral margin convex. Umbones 
low, located posteriorly; umbonal angle 101 to 116°. 
Beaks pointed, opisthogryate. Disk broad, ornamented 
with abundant ribs diverging from umbo area and form- 
ing chevron-shaped (divaricate) pattern. Chevron angle 
46 to 59°. Chevrons bisected by line extending from 
slightly anterior of umbo to center (rarely anterior) of 
ventral margin; ribs anterior to bisecting line 18 to 20, 
ribs posterior to bisecting line about 20 to 28. Secondary 
divarication rare, only on specimens with anteriorly lo- 
cated divarication. Total number of ribs on disk of each 
valve usually approximately 40; ribs very narrow to nar- 
row, with interspaces approximately 4% as wide to same 
width as ribs, except anterior of chevron-bisecting line, 
where ribs become wider and more widely spaced. 
Growth checks near ventral margin or absent. Escutcheon 
moderately prominent, slightly sunken, and crossed by 
narrow ribs. Hinge with at least 18 anterior taxodont teeth 


The Veliger, Vol. 48, No. 2 


and, at least, six posterior taxodont teeth. Resilifer op- 
isthocline, narrow. 


Dimensions of holotype: Conjoined valves (partially 
open), height 11.5 mm, length 15.7 mm, thickness 9 mm 
(taking into account the partial opening). 


Holotype: CAS 69081 [= CAS 5090]. 


Type locality: CAS 69080, just east of Queen Charlotte 
City, Bearskin Bay, Skidegate Inlet region, Queen Char- 
lotte Islands, British Columbia. 


Paratypes: CAS 69080.01 [= CAS 5091] and CAS 
69080.02 [= CAS 5092]. 


Geologic age: Latest Albian (probably) to early Turonian. 


Distribution: UPPERMOST ALBIAN (PROBABLY) 
TO CENOMANIAN: Haida Formation, just east of 
Queen Charlotte City, Bearskin Bay, Skidegate Inlet re- 
gion, Queen Charlotte Islands, northern British Columbia. 
LOWER TURONIAN: Hornbrook Formation, Osburger 
Gulch Member, Jackson County, southern Oregon; Redd- 
ing Formation, Frazier Siltstone, Shasta County, northern 
California; Cortina formation (informal), Venado Sand- 
stone Member, near Sites, Colusa County, northern Cal- 
ifornia; Panoche Formation, Garzas Creek, Stanislaus 
County, north-central California. 


Discussion: The above description of this species is 
based on eight specimens: one left valve, six right valves, 
and one with conjoined valves. The escutcheonal area is 
poorly preserved on all of these specimens. 

Whiteaves (1884:232) reported one specimen of Nu- 
cula (Acila) truncata Gabb, 1864, from the type locality 
area of A. (T.) haidana and one specimen from the vicin- 
ity of Alliford Bay, also in the Skidegate Inlet region, 
Queen Charlotte Islands. Whiteaves, unfortunately, did 
not figure these specimens, nor could they be located by 
us in any museum collection. Based on their geographic 
occurrence, however, it is most likely that they are A. (T.) 
haidana. 

Schenck (1936:50) included tentatively ““?Nucula (Aci- 
la) truncata Gabb. Whiteaves, 1879:162; 1903:389— 
390,’ in his synonymy of A. (7.) haidana, but Whiteaves 
reported that these specimens were collected at localities 
on 1) the northwest side of Hornby Island, 2) the south- 
west side of Denman Island, Vancouver Island, and 3) 
Sucia Island, Washington. All of these localities occur in 
the Nanaimo Group. Both A. (7.) demessa and A. (T.) 
grahami are herein recognized from this group, but A. 
(T.) haidana is not. It does not seem likely, therefore, that 
these Nanaimo Group specimens of Whiteaves (1879, 
1903) should be identified as A. (T.) haidana. Whiteaves, 
furthermore, provided no type numbers and no illustra- 
tions of these specimens. In addition, Bolton (1965) did 
not list type numbers from them. Additionally, none of 
them is part of the GSC collection. 


R. L. Squires & L. R. Saul, 2005 


One specimen of Acila (T.) haidana is from USGS loc. 
M-175 near Sites, Colusa County, northern California. 
Although this locality is usually reported as being in the 
upper part of the Cenomanian Antelope Shale, Popenoe 
et al. (1987:79) reported that some of the fossils at this 
particular locality probably slumped from the overlying 
basal Venado Formation of early Turonian age. We con- 
cur, based on the presence of the following Turonian gas- 
tropods found with the Acila (T.) haidana specimen: Gy- 
rodes (?Sohlella) yolensis Popenoe et al., 1987 and Gy- 
rodes (Gyrodes) dowelli White, 1889. 


Acila (Truncacila) demessa Finlay, 1927 
(Figures 18—26) 


Nucula truncata Gabb, 1864:198, pl. 26, figs. 184, 184a, 
184b. 

not Nucula truncata Nilsson, 1827:16, pl. 5, fig. 6. 

Acila demessa Finlay, 1927:522 (new name for Nucula trun- 
cata Gabb, not Nilsson); Stewart, 1930:45, pl. 3, fig. 6. 

Acila (Trunacila) demessa Finlay. Schenck, 1936:48—SO, pl. 
2, figs. 5, 7, 8, 9, text-fig. 7; 1943:pl. 8, fig. 5; pl. 9, 
fs al Shai 

Acila shumardi Dall. Ludvigsen & Beard, 1994:90, fig. 54 
(in part); 1997:110, fig. 65 (in part). 

?Nucula (Acila) truncata Gabb. Whiteaves, 1879:162 (in 
part); 1903:389—390 (in part). 


Diagnosis: Shell medium, subtrigonal to subquadrate. 
Chevrons bisected by line meeting ventral-margin ante- 
rior. Total number of ribs on disk of each valve approx- 
imately 70; ribs (posterior of chevron-bisecting line) flat 
and very narrow to moderately wide, with interspaces ap- 
proximately ¥; to % as wide. Escutcheon bounded by 
smooth area not crossed by ribs. 


Description: Shell medium for subgenus (up to 20.4 mm 
in height and 26.5 mm in length, most specimens ap- 
proximately 13 mm in height and 16 mm in length), lon- 
ger than high, height/length ratio = 0.72 to 0.89. Subtri- 
gonal to subquadrate; inequilateral, equivalved, valves 
moderately inflated. Anterior end broadly rounded. An- 
tero-dorsal margin long, straight to convex. Posterior end 
straight, abruptly truncate and set off from escutcheon by 
weak rostration. Ventral margin convex. Umbones low, 
located posteriorly; umbonal angle 103 to 117°. Beaks 
pointed, incurved, opisthogyrate. Disk very broad, orna- 
mented with abundant ribs diverging from umbo area and 
forming chevron-shaped (divaricate) pattern. Chevron an- 
gle approximately 30 to 34°. Secondary development of 
chevrons on few specimens. Chevrons bisected by line 
extending from slightly anterior of umbo to center of ven- 
tral margin; ribs anterior to bisecting line 22 to 39 (ex- 
cluding occasional bifurcations near where anterior and 
ventral margins meet), ribs posterior to bisecting line 26 
to 47. Total number of ribs on disk of each valve usually 
approximately 70; ribs flat and very narrow to moderately 
wide, with interspaces approximately ’; to ¥, as wide, 


Page 93 


except anterior of chevron-bisecting line, where ribs be- 
come wider and more widely spaced. Growth checks near 
ventral margin common on some specimens and associ- 
ated, from about 4 of distance from posterior end to 
where anterior end meets ventral margin, with bifurcation 
of ribs into riblets and riblet insertion. Prominent growth 
checks, corresponding to same position on each valve, 
occasionally continue across escutcheon area to beaks. 
Ventral-margin edge and inner margin (for short distance) 
finely crenulate. Escutcheon prominent, sunken, and 
bounded by shallow groove not crossed by ribs; narrow 
ribs present on slightly inflated central part of escutch- 
eonal area. Interior nacreous. Adductor scars well delin- 
eated. Left-valve hinge with approximately 11 posterior 
taxodont teeth, similar in form, becoming stronger pos- 
teriorly; approximately 23 anterior taxodont teeth, similar 
in form, becoming stronger anteriorly. Resilifer narrow, 
opisthocline; bordered posteriorly by strong, high tooth. 


Lectotype: ANSP 4417 (designated by Stewart, 1930: 
46). 


Type locality: Pentz, Butte County, northern California. 


Geologic age: Late Turonian to late late Campanian and 
possibly early Maastrichtian. 


Distribution: UPPER TURONIAN: Budden Canyon 
Formation, Gas Point Member, Shasta County, northern 
California; Ladd Formation, Baker Canyon Member to 
Holz Shale Member transition, Santa Ana Mountains, 
Orange County, southern California. CONIACIAN: 
Redding Formation, Member V, upper part, Shasta Coun- 
ty, northern California. LOWER SANTONIAN: Redding 
Formation, Member V, Shasta County, northern Califor- 
nia. UPPER SANTONIAN: Haslam Formation, lower 
part, Chemanius River, near Nanaimo, Vancouver Island, 
British Columbia; Haslam Formation, lower part, Salt- 
spring Island, British Columbia; Redding Formation, 
Member VI?, Shasta County, northern California; Chico 
Formation, Musty Buck Member, Butte County, northern 
California. SANTONIAN UNDIFFERENTIATED: Pa- 
noche Formation, Merced County, north-central Califor- 
nia. UPPER SANTONIAN/LOWERMOST CAMPANI- 
AN: Haslam Formation, upper part, Brannen Lake, near 
Nanaimo, Vancouver Island, British Columbia. LOWER 
CAMPANIAN: Chico Formation, Ten Mile Member, 
Butte County, northern California; Chico Formation, 
Pentz Road member (informal), Butte County, northern 
California; Ladd Formation, upper Holz Shale member, 
Santa Ana Mountains, Orange County, southern Califor- 
nia. LOWER MIDDLE CAMPANIAN: Ladd Formation, 
upper Holz Shale Member, Santa Ana Mountains, Orange 
County, southern California. UPPER MIDDLE TO 
LOWER UPPER CAMPANIAN: Cedar District Forma- 
tion, upper part, west shoreline of Denman Island off east 
coast of Vancouver Island, British Columbia. Chatsworth 
Formation, Dayton and Bell canyons, Simi Hills, Ventura 


Page 94 The Veliger, Vol. 48, No. 2 


Explanation of Figures 18 to 32 


Figures 18-26. Acila (Truncacila) demessa Finlay, 1927. Figure 18. Hypotype LACMIP 13228, LACMIP loc. 
10835, left valve, X2.6. Figure 19. Hypotype LACMIP 13229, LACMIP loc. 17611, left valve, <2.6. Figure 20. 
Hypotype RBCM.EH2003.009.0001, Locality 1, left valve, X 1.7. Figure 21. Hypotype LACMIP 13229, LACMIP 
loc. 17611, right valve, 2.6. Figure 22. Hypotype LACMIP 13230, LACMIP loc. 10832, right valve, <2.7. 


R. L. Squires & L. R. Saul, 2005 


County, southern California: Williams Formation, Pleas- 
ants Sandstone Member, Santa Ana Mountains. Orange 
County, southern California. LOWER UPPER CAM- 
PANIAN: Jalama Formation, Santa Barbara County. 
southern California. UPPER UPPER CAMPANIAN TO 
POSSIBLY LOWER MAASTRICHITAN: Rosario For- 
mation at Punta San Jose and San Antonio del Mar, Baja 
California, Mexico. 


Discussion: The above description is based on 847 spec- 
imens: 320 left valves, 356 right valves. and 171 with 
conjoined valves. 

Our study revealed. for the first tme. that on A. (T.) 
demessa, ribs commonly bifurcate into riblets near the 
ventral margin, the left-valve hinge has approximately 11 
posterior teeth, and the right-valve hinge has approxi- 
mately 18 anterior teeth. 

Schenck (1936:48—50) reported A. (7.) demessa (from 
strata now referred to as the Rosario Formation) at Punta 
Banda and San Antonio del Mar, Baja California (Figure 
1, locales 25 and 26. respectively). Only his San Antonio 
del Mar specimen is A. (7.) demessa. His Punta Banda 
specimen (hypotype CAS 6205) is A. (7.) grahami. 

Whiteaves (1879, 1903) reported Nucula (Acila) trun- 
cata Gabb, 1864. from various localities, including the 
Nanaimo area, Vancouver Island. British Columbia, and 
Sucia Island, Washington. He provided no type numbers 
nor any illustrations of these specimens, and none is part 
of any known museum collection. Based on their geo- 
graphic occurrences, however, it is possible that the Na- 
naimo area and Sucia Island specimens are A. (T.) de- 
messa. 

Page et al. (1951:1738—1739) mentioned that Acila de- 
messa Was found at four LSJU localities in beds in the 
Santa Ynez Mountains northeast of Santa Barbara. Santa 
Barbara County, southern California. These beds were 
later placed in the Espada Formation by Dibblee (1966: 
17). which ranges in range from latest Jurassic or Early 
Cretaceous to Late Cretaceous age (Dibblee. 1966). He 
also mentioned that these Aci/a specimens were found 
associated with the rudist Coralliochama orcutti White, 
1885. This rudist is known to be of late Campanian to 
early Maastrichtian age (Marincovich, 1975). An attempt 
to find these Acila and rudist fossils in the CAS collection 
was unsuccessful. If the identification of the rudist is ac- 


Page 95 


curate, these Aci/a specimens could be A. (7.) demessa, 
A. (T.) grahami, sp. nov., or A. (T.) rosaria, sp. nov. 

Haggart & Higgs (1989) reported Acila (Truncacila) 
sp. from the upper Santonian in marine shales apparently 
overlying the Honna Formation in the area of Skidegate 
Inlet. Queen Charlotte Islands. British Columbia. Al- 
though the geologic age of this bivalve is within the range 
of A. (7.) demessa, closer investigation of this Queen 
Charlotte bivalve revealed that its preservation is too poor 
to even allow generic identification (J. Haggart. personal 
communication). 


Acila (Truncacila) grahami Squires & Saul, 
sp. nov. 
(Figures 27-38) 


Acila (Truncacila) cf. demessa Finlay, 1927. Schenck, 1936: 


50. 

Acila (Truncacila) sp. E. Schenck, 1943:65—66, pl. 9. figs. 
DAY 

?Nucula (Acila) truncata Gabb. Whiteaves. 1879:162 (in 
part). 


Diagnosis: Shell small. trigonal to subquadrate. Chevrons 
bisected by line usually meeting ventral-margin anterior 
(rarely center). Total number of ribs on disk of each valve 
approximately 50: mbs (posterior of chevron-bisecting 
line) narrow to moderately wide, with interspaces ap- 
proximately % to 4% as wide. Escutcheonal ribs continuous 
with ribs on disk. 


Description: Shell small for subgenus (up to 13.1 mm in 
height and 16.5 mm in length. most specimens approxi- 
mately 8 mm in height and 9 mm in length), longer than 
high, height/length ratio = 0.75 to 0.92. Trigonal to sub- 
quadrate,. inequilateral, equivalved, valves moderately in- 
flated. Anterior end broadly rounded. Antero-dorsal mar- 
gin long and straight. Posterior end truncate and set off 
from escutcheon by weak rostration. Ventral margin con- 
vex. Umbones moderately low. located posteriorly: um- 
bonal angle varying from 86° (most trigonal shells) to 
114° (most subquadrate shells). Beaks pointed. incurved. 
opisthogyrate. Disk very broad, ornamented with abun- 
dant ribs diverging from umbo area and forming chevron- 
shaped (divaricate) pattern. Chevron angle varying from 
38° (most trigonal shells) to 56° (most subquadrate 


Figure 23. Hypotype RBCM.EH2003.010.0001, Locality 2. right valve. X 1.8. Figure 24. Hypotype LACMIP 13231. 
LACMIP loc. 22406, right valve. X2.7. Figure 25. Hypotype LACMIP 13232, LACMIP loc. 28780. left-valve 
hinge. X3. Figure 26. Hypotype LACMIP 13233, LACMIP loc. 10832, posterior view, X 1.4. Figures 27-32. Acila 
(Truncacila) grahami Squires & Saul, sp. nov. Figure 27. Paratype RBCM.EH2003.012.0002, Locality 3. left valve. 
x4.4. Figure 28. Paratype ,RBCM.EH2003.014.0001, Locality 4. left valve. X2.8. Figure 29. Holotype 
RBCM.EH2003.011.0002. Locality 3. left valve. X3.8. Figure 30. Paratype RBCM.EH2003.012.0001. Locality 3. 
left valve. X3.9. Figure 31. Paratype RBCM-.EH2003.013.0001. Locality 4, left valve. X2.8. Figure 32. Paratype 
CAS 69079. CAS loc. 69079. crushed specimen of left valve. <2.4. 


Page 96 The Veliger, Vol. 48, No. 2 


Explanation of Figures 33 to 48 


Figures 33-38. Acila (Truncacila) grahami Squires & Saul, sp. nov. Figure 33. Paratype RBCM.EH2003.012. 
0003, Locality 3, right valve, 4.4. Figure 34. Paratype RBCM.EH2003.011.0001, Locality 3, right valve, 3.2. 
Figure 35. Paratype CAS 69082.01, CAS loc. 69082, rubber peel of right valve, 2.4. Figure 36. Holotype 
RBCM.EH2003.011.0002, Locality 3, posterior view of left valve, <4.2. Figure 37. Paratype RBCM.EH2003. 
011.0003, Locality 3, posterior view of right valve, x4. Figure 38. Holotype RBCM.EH2003.011.0002, Locality 3, 


R. L. Squires & L. R. Saul, 2005 


Page 97 


shells). Chevrons bisected by line extending from slightly 
anterior of umbo to anterior part of ventral margin (rarely 
center); ribs anterior to bisecting line 12 to 30, ribs pos- 
terior to bisecting line 22 to 33. Total number of ribs on 
disk of each valve usually approximately 50; ribs narrow 
to moderately wide, with interspaces approximately % to 
% as wide, except anterior of chevron-bisecting line, 
where ribs become slightly wider and more widely 
spaced. Escutcheon moderately prominent, slightly sunk- 
en, and bounded by shallow groove crossed by ribs con- 
tinuous with ribs on disk; ribs slightly stronger on inflated 
central part of escutcheonal area. Anterior hinge with 16 
teeth, posterior hinge with 9 teeth. 


Dimensions of holotype: Left valve, height 9 mm, length 
10.8 mm. 


Holotype: RBCM.EH2003.01 1.0002. 


Type locality: Loc. 3, north end of Hornby Island, British 
Columbia, 49°32'57"N, 124°41'40"W. 


Paratypes: RBCM.EH2003.011.0001, RBCM.EH2003. 
011.0003, RBCM.EH2003.012.0001 to RBCM.EH2003. 
012.0003, RBCM.EH2003.013.0001, RBCM.EH2003. 
014.0001, and CAS 69082.01. 


Geologic age: Late middle Campanian to early late 
Maastrichtian. 


Distribution: UPPER MIDDLE TO LOWER UPPER 
CAMPANIAN: Cedar District Formation, upper part, 
west shoreline of Denman Island off east coast of Van- 
couver Island, British Columbia. LOWER UPPER CAM- 
PANIAN: Jalama Formation, Santa Barbara County, 
southern California. UPPERMOST MIDDLE CAMPAN- 
IAN TO LOWERMOST UPPER CAMPANIAN: Moon- 
light Formation?, north end of Shale Hills, southwest side 
of Antelope Valley, eastern Temblor Range, Kern County, 
south-central California. UPPERMOST CAMPANIAN 
OR LOWER MAASTRICHTIAN: Northumberland For- 
mation, Collishaw Point, north end of Hornby Island, east 
coast of Vancouver, British Columbia. UPPER UPPER 
CAMPANIAN TO POSSIBLY LOWER MAASTRICH- 
TIAN: Rosario Formation at Punta Banda, near Ensenada, 
Baja California. UPPER LOWER TO LOWER UPPER 
MAASTRICHTIAN: Moreno Formation, Ortigalita 
Creek, Merced County and Ciervo Hills, Fresno County, 


central California; Moreno Formation, Marca Shale 
Member, Fresno County, central California. 


Discussion: This new species is based on 18 specimens: 
five left valves, 10 right valves, and three with conjoined 
valves. The best preserved ones are from the Northum- 
berland Formation. 

The new species is most similar to Acila (Truncacila) 
haidana, but the new species differs by having a more 
variable shape, narrower interspaces between the ribs, and 
having the line bisecting the chevrons located more an- 
teriorly on the ventral margin. 

Acila (Truncacila) grahami is similar to Acila piura 
Olsson (1931:35, pl. 2, figs. 9, 10, 14) from the upper 
Oligocene Heath Formation of northern Peru. The new 
species differs from A. piura by having a narrower chev- 
ron angle, more variability in the width of the interspaces 
between the ribs, and more ribs (22 to 33 versus 17) 
posterior to the bisecting line. 

Whiteaves (1879:162) reported Nucula (Acila) truncata 
Gabb, 1864, from the northwest side of Hornby Island. 
He provided no type numbers nor any illustrations of any 
specimens, and none is part of any known museum col- 
lection. It is most likely, however, than any acilids found 
there would be A. (7.) grahami, because the type locality 
of this species is at the north end of Hornby Island. 


Etymology: The species is named for Raymond Graham 
who collected many of the specimens and who informed 
the authors about them. 


Acila (Truncacila) rosaria Squires & Saul, 
sp. nov. 


(Figures 39—43) 


Diagnosis: Shell medium, elliptical-subquadrate. Chev- 
rons bisected by line meeting ventral-margin anterior. To- 
tal number of ribs on disk of each valve approximately 
80; ribs (posterior of chevron-bisecting line), very narrow 
to narrow, with interspaces approximately %4 as wide to 
same width as ribs. Escutcheon bounded by flattish to 
grooved area usually crossed by ribs not continuous with 
ribs on disk. 


Description: Shell medium for subgenus (up to 19.6 mm 
in height and 25.5 mm in length), longer than high, 
height/length ratio = 0.68 to 0.78. Elliptical-subquadrate, 


left-valve hinge, X3.8. Figures 39-43. Acila (Truncacila) rosaria Squires & Saul, sp. nov. Figure 39. Holotype 
LACMIP 13234, LACMIP loc. 25431, left valve, 1.8. Figure 40. Paratype LACMIP 13235, LACMIP loc. 8068, 
left valve, X2. Figure 41. Paratype UCMP 155631, UCMP loc. B-5320, left valve, <2. Figure 42. Paratype LACMIP 
13236, LACMIP loc. 25431, right valve, < 1.8. Figure 43. Hypotype LACMIP 13234, LACMIP loc. 25431, oblique 
posterior view, X2.3. Figures 44—48. Acila (Truncacila) princeps Schenck, 1943. Figure 44. Holotype CAS 69075, 
CAS loc. 69075, left valve, X1.3. Figure 45. Hypotype LACMIP 13130, LACMIP loc. 23314, left valve, 1.5. 
Figure 46. Hypotype CAS 69086.02, CAS loc. 69086, rubber peel of left valve, 2.1. Figure 47. Paratype CAS 
69078, CAS loc. 69075, left valve, 1.5. Figure 48. Paratype CAS 69076, CAS loc. 69075, right valve, 1.5. 


Page 98 


inequilateral, equivalved, valves moderately inflated. An- 
terior end broadly rounded. Antero-dorsal margin long 
and straight. Posterior end straight, truncate and set off 
from escutcheon by weak rostration. Ventral margin con- 
vex. Lunule small, not very distinct, very slightly de- 
pressed, and crossed by ribs. Umbones low, located pos- 
teriorly; umbonal angle varying from 113 to 125°. Beaks 
pointed, incurved, opisthogyrate. Disk very broad, orna- 
mented with abundant ribs diverging from umbo area and 
forming chevron-shaped (divaricate) pattern. Chevron an- 
gle 34 to 44°. Chevrons bisected by line extending from 
slightly anterior of umbo to anterior of ventral margin 
(rarely near center); ribs anterior to bisecting line 30 to 
44 (excluding occasional bifurcations), ribs posterior to 
bisecting line 42 to 49. Secondary divarication common; 
tertiary divarication rare and only on those specimens 
where divarication is near center. Total number of ribs on 
disk of each valve usually approximately 80; ribs very 
narrow to narrow, with interspaces approximately “4 as 
wide to same width as ribs, except anterior of chevron- 
bisecting line, where ribs become slightly wider, more 
widely spaced, and occasionally of irregular width. Ribs 
on juvenile specimens minutely tuberculate. Growth 
check(s) prominent on some adult specimens near ventral 
margin; growth check(s) commonly associated with riblet 
insertion near ventral-margin center and anterior of ven- 
tral-margin center. Ventral-margin edge and, for short dis- 
tance, interior finely crenulate. Escutcheon prominent, 
sunken, bounded by flattish to shallowly grooved area 
usually crossed by ribs not continuous with ribs on disk, 
except on ventral part of escutcheon; flattish to shallowly 
grooved area occasionally smooth. Escutcheonal area el- 
evated centrally and with riblets more widely spaced than 
elsewhere on this area. Interior nacreous. Adductor scars 
well delineated. Right-valve hinge with at least 18 ante- 
rior teeth, similar in form, becoming stronger posteriorly. 
Resilifer narrow, oblique. 


Dimensions of holotype: Conjoined valves, height 18.0 
mm, length 25.4 mm, thickness 14.9 mm. 


Holotype: LACMIP 13234. 


Type locality: LACMIP loc. 25431, Punta San Jose, Baja 
California, Mexico, 31°265'30"N, 116°38'45”"W. 


Paratypes: LACMIP 13235 and 13236, and UCMP 
155631. 


Geologic age: Early late Campanian to early late Maas- 
trichtian. 


Distribution: LOWER UPPER CAMPANIAN: Moon- 
light Formation?, north end of Shale Hills, southwest side 
of Antelope Valley, eastern Temblor Range, Kern County, 
south-central California. UPPER UPPER CAMPANIAN 
TO POSSIBLY LOWER MAASTRICHTIAN: Point 
Loma Formation, near Carlsbad, San Diego County, 
southern California; Rosario Formation at Punta San Jose, 


The Veliger, Vol. 48, No. 2 


San Antonio del Mar, and Arroyo Santa Catarina, Baja 
California, Mexico. UPPER LOWER TO LOWER UP- 
PER MAASTRICHTIAN: Moreno. Formation, Tierra 
Loma Member, Merced County, north-central California. 


Discussion: This species is based on 40 specimens: 10 
left valves, 11 right valves, and 19 with conjoined valves. 
Most show excellent preservation, although a few shells 
are partially decorticated. Most specimens are from the 
Rosario Formation, and most of these are from or near 
the vicinity of Punta San Jose. 

The new species is most similar to A. (T.) demessa, but 
the new species differs by having a more oval shape, 
more projected anterior and posterior ends, generally 
more uniform sculpture over the entire valve surface, and 
usually a larger shell size. On the posterior part of the 
disk of the new species, the ribs have more prominent 
interspaces than those of A. (T.) demessa. In addition, 
large specimens of the new species have narrower ribs 
than large specimens of A. (7T.) demessa. In addition, the 
ribs on the anterior part of the valves of the new species 
can be elevated and minutely tuberculate, whereas cor- 
respondingly, on A. (T.) demessa these ribs are flat-topped 
and smooth. The escutcheonal area of the new species 
can be very similar to that of A. (7.) demessa, if the 
bounding shallow groove is smooth or smoothish, but 
most specimens of the new species have ribs across the 
entire escutcheon. 

Acila (T.) rosaria is similar to A. (T.) sp. nov.? but 
differs by having a more elliptical shape, usually narrow- 
er ribs, and slightly narrower spaced ribs. 


Etymology: The new species is named for the Rosario 
Formation, Baja California, Mexico. 


Acila (Truncacila) princeps Schenck, 1943 
(Figures 45—51) 


Acila (Truncacila) princeps Schenck, 1943:63—66, pl. 8, 
figs. 1-4, 6-8. 

Acila (Truncacila) sp. D. Schenck, 1943:65, pl. 9, fig. 5. 

Acila (Truncacila) sp. F Schenck, 1943:66, pl. 9, figs. 6, 8. 

Acila sp. Saul, 1986b:26. 


Diagnosis: Shell large, subquadrate, rarely trigonal. 
Chevrons bisected by line meeting ventral-margin ante- 
rior. Total number of ribs on disk of each valve approx- 
imately 85; ribs (posterior of chevron-bisecting line), flat 
and narrow to wide, with interspaces approximately /, 
to VY, as wide. 


Description: Shell large for subgenus (up to 25.8 mm in 
height and 34.4 mm in length), longer than high, height/ 
length ratio = 0.71 to 0.85. Subquadrate, rarely trigonal; 
inequilateral, equivalved, and valves inflated. Anterior 
end broadly rounded. Antero-dorsal margin long and low- 
ly convex. Posterior end straight, abruptly truncate and 
set off from escutcheon by weak rostration. Ventral mar- 


R. L. Squires & L. R. Saul, 2005 


Page 99 


Explanation of Figures 49 to 51 


Figures 49-51. Acila (Truncacila) princeps Schenck, 1943. Figure 49. Holotype CAS 69075, CAS loc. 69075, 
right valve, <1.3. Figure 50. Hypotype CAS 950.01, CAS loc. 950, right valve, x 1.7. Figure 51. Holotype CAS 


69075, CAS loc. 69075, posterior view, 1.3. 


gin convex. Lunule poorly developed, slightly depressed. 
Umbones low, located posteriorly; umbonal angle vary- 
ing from 94 to 119°. Beaks pointed, incurved, opistho- 
gyrate. Disk very broad, ornamented with abundant ribs 
diverging from umbo area and forming chevron-shaped 
(divaricate) pattern. Chevron angle 30 to 39°. Chevrons 
bisected by line extending from slightly anterior of umbo 
to anterior of ventral margin; ribs anterior to bisecting 
line 30 to 39, ribs posterior to bisecting line 45 to 54. 
Secondary divarication uncommon. Total number of ribs 
on disk of each valve usually approximately 85; ribs flat 
and narrow to wide, with interspaces approximately Y¥, 
to ¥Y, as wide, except anterior of chevron-bisecting line, 
and to a lesser extent on extreme posterior part of disk, 
where ribs become round and slightly wider. Each rib 
commonly bifurcates into two riblets along ventral mar- 
gin between approximately , of distance from posterior 
end to meeting of anterior end and ventral margin. 
Growth check(s) near ventral margin often associated 
with appearance of these bifurcated riblets. Ventral-mar- 
gin edge and interior, for short distance, finely crenulate. 
Escutcheon slightly? sunken, bounded by smooth? re- 
gion; middle part of area crossed by numerous oblique 
ribs, becoming stronger ventrally. Interior nacreous. Sim- 
ple pallial line. Adductor muscle scars well delineated. 
Approximately 21 anterior teeth and 11 posterior teeth. 


Dimensions of holotype: Conjoined valves, height 26 
mm, length 34.5 mm, thickness 18.7 mm. 


Holotype: CAS 69075 [= LSJU 6960]. 


Type locality: CAS 69075 [= LSJU 2372], west side San 
Joaquin Valley, northern California. 


Paratypes: CAS 69076 [= LSJU 6963]; CAS 69077 [= 
LSJU 6961], and CAS 69078 [= LSJU 6962]. 


Geologic age: Late late Campanian to early late Maas- 
trichtian. 


Distribution: UPPER UPPER CAMPANIAN TO POS- 
SIBLY LOWER MAASTRICHTIAN: Point Loma For- 


mation, La Jolla, San Diego County, southern California; 
Rosario Formation, San Antonio del Mar, Baja California, 
Mexico. UPPER LOWER TO LOWER UPPER MAAS- 
TRICHTIAN: Tesla Formation, Alameda and San Joa- 
quin counties, northern California; Moreno Formation, 
““Garzas Sand”? member and also Mercy sandstone lentil, 
within middle part of Tierra Loma Member, Merced 
County, north-central California. LOWER UPPER 
MAASTRICHTIAN: El Piojo Formation, Lake Naci- 
miento, San Luis Obispo County, west-central California. 
UPPER MAASTRICHTIAN UNDIFFERENTIATED: 
Panoche Formation, Franklin Canyon, west of Martinez, 
Contra Costa County, northern California; Deer Valley 
formation (informal), north flank of Mount Diablo, Con- 
tra Costa County, northern California. 


Discussion: The above description of this species is 
based on nine specimens: two left valves, one partial left 
valve, two right valves, three with conjoined valves, and 
one internal mold of a left valve. The lunule and escutch- 
eon are both poorly preserved on every examined spec- 
imen. 

Acila (T.) princeps is very closely similar to A. (T.) 
demessa in having, on some specimens, ribs that are flat- 
topped and very closely spaced. Acila (T.) princeps dit- 
fers from A. (T.) demessa by having larger size, more 
uniform sculpture, and more numerous ribs. Schenck 
(1943:63) mentioned an area of obsolete radial ribbing on 
the holotype, but that is not the case (see Figures 44 and 
49). 

Schenck (1943:63) reported that the chevron angle, 
which he referred to as the angle of bifurcation, of A. (7.) 
princeps is 60 to 67°. In this present study, we measured 
the chevron angle of A. (7.) princeps near where the di- 
varication begins, in the same manner as we measured 
this feature for all the other studied species. The only way 
we could obtain measurements of 60 to 67° is if we mea- 
sured the along the ventral margin of the valve, where 
the ribs usually curve significantly. 


Acknowledgments. We are very appreciative of the access given 


Page 100 


to us to browse the CAS, LACMIP, and UCMP collections and 
for being able to borrow numerous specimens. We are very grate- 
ful for the loan of specimens by Graham Beard (Vancouver Is- 
land Paleontological Museum at Qualicum Beach, British Co- 
lumbia), Tom Cockburn (Victoria Palaeontology Society), John 
Cooper (California State University, Fullerton), Raymond Gra- 
ham (RBCM), Eric Gohre (Oroville, California), Greg Slak (Los 
Angeles), and Lois Walker (Sidney, British Columbia). James W. 
Haggart (Geological Survey of Canada, Vancouver) provided 
very useful information about the type locality of Acila (T.) hai- 
dana. Raymond Graham generously provided color photographs 
and stratigraphic details of Cretaceous Acila from Vancouver Is- 
land. His help, and that of Tom Cockburn, were instrumental in 
the discovery of Acila (T.) grahami. Louie Marincovich, Jr. 
(CAS) kindly provided an English translation of Skodkevich 
(1967). The manuscript benefited from comments by Eugene V. 
Coan (Palo Alto, California) and an anonymous reviewer. 


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APPENDIX 
LOCALITIES CITED 


Locality 1. Private shale quarry at 340 Blackburn Road, 
6 km NW of Fulford Harbor, Saltspring Island, off 
southeast coast of Vancouver Island, British Columbia. 
Haslam Formation, lower part. Age: Late Santonian. 
Collector: Raymond Graham, September 29, 2000. 

Locality 2. Cliff on left bank of Chemainus River, 500 m 
downstream from the confluence with Banon Creek, 
3.3 km SW of town of Chemainus, southeastern Van- 
couver Island, British Columbia. Haslam Formation, 
lower part. Age: Late Santonian. Collectors: Lois 
Walker and Raymond Graham, August 25, 2002. 


R. L. Squires & L. R. Saul, 2005 


Page 103 


Locality 3. SE % of an intertidal bench, 300 m seaward 
from the high-water mark at Collishaw Point, N end of 
Hornby Island, off east coast of Vancouver Island, Brit- 
ish Columbia. Northumberland Formation. Age: Latest 
Campanian or early Maastrichtian. Collector: Raymond 
Graham, June 21, 1997. 

Locality 4. Intertidal bench 400 m N of Buckley Bay/ 
Denman Island ferry terminal, west-central shoreline of 
Denman Island, off east coast of Vancouver Island, 
British Columbia. Cedar District Formation, upper part. 
Age: Late middle to early late Campanian. Collector: 
Raymond Graham, June 21, 2001. 

CAS 950. Hard lens about 0.3 m thick outcropping be- 
hind old distillery on Johnson Ranch at San Antonio 
del Mar, Baja California, Mexico. Rosario Formation. 
Age: Late Campanian to early Maastrichtian. Collec- 
tors: E. K. Jordan and L. G. Hertlein, January, 1926. 

CAS 1552. 152 m W of center of section 28, T. 26 S, R. 
18 E., Sawtooth Ridge Quadrangle (7.5 minute, 1961), 
N end of Shale Hills, SW side of Antelope Valley, 
eastern Temblor Range, Kern County, south-central 
California. Moonlight Formation? Age: Latest middle 
Campanian to earliest late Campanian. Collector: G. D. 
Hanna and J. H. Snow, April, 1929. 

CAS 69075. [= SU 2372]. In second valley (with right 
turns), about 1.6 km N of Laguna Seca, on brow of 
hill on N side of valley, 366 m N and 503 m E of SW 
corner of section 12, T. 12 S, R. 10 E, Charleston 
School Quadrangle (7.5 minute, 1956), Merced Coun- 
ty, north-central California. Moreno Formation, Mercy 
sand lentil within Tierra Loma Shale Member. Age: 
Late early to early late Maastrichtian. Collector: M. B. 
Payne, 1941. 

CAS 69079. [= LSJU 1274]. White concretionary lime- 
stone bed embedded in shale, just NE of town of Oil 
City, 305 m NE of center of section 17, T. 19 S, R. 15 
E, Domengine Ranch Quadrangle (7.5 minute, 1956) 
Fresno County, north-central California. Moreno For- 
mation, about 91 to 122 m below top of formation. 
Age: Late early to early late Maastrichtian. Collector: 
P. W. Reinhart, January 27, 1934. 

CAS 69080. About 1.6 km E of Queen Charlotte City, 
above beach, Bearskin Bay, Skidegate Inlet region, 
southern Graham Island, Queen Charlotte Islands, Brit- 
ish Columbia, Canada. Haida Formation, probably 
Shale member. Age: Probably latest Albian to Ceno- 
manian. Collector: unknown. 

CAS 69082. [= LSJU 2575]. Limestone concretion em- 
bedded in purple shale, NE corner of SE % of section 
23, T. 16S, R. 12 E, Monocline Ridge Quadrangle (7.5 
minute, 1955), Fresno County, northern California. 
Moreno Formation, Marca Shale Member. Age: Late 
-early to early late Maastrichtian. Collector: D. C. 
Birch. 

CAS 69086. In railroad cut near Santa Fe Railroad tunnel 
above Franklin Canyon Inn, W of Martinez, Briones 


Valley Quadrangle (7.5 minute, 1959), Contra Costa 
County, northern California. Panoche Formation. Age: 
Late Maastrichtian. Collector: E. A. Watson. 

CAS 69095. In small area of Cretaceous siltstone in SW 
% of section 21, T. 26 S, R. 18 E, Sawtooth Ridge 
Quadrangle (7.5 minute, 1961), N end of Shale Hills, 
W side of Antelope Valley, eastern Temblor Range, 
Kern County, south-central California. Moonlight For- 
mation? Age: Latest middle Campanian or earliest late 
Campanian. Collector: G. Henny. 

CAS 69110. [= LACMIP 22874]. On E fork of Huling 
Creek, at edge of streambed in limestone bed, on S 
limb of hairpin meander, 1457 m N 25.5°E of conflu- 
ence of Huling Creek and North Fork of Cottonwood 
Creek, Ono Quadrangle (15 minute, 1952), Shasta 
County, northern California. Budden Canyon Forma- 
tion, Chickabally Mudstone Member. Age: Early Al- 
bian (Leconteites lecontei Zone). Collector: M. A. 
Murphy, summers 1951-1953. 

LACMIP 8068. Approximately 2.4 km S of Punta San 
Jose, Baja California, Mexico. Rosario Formation. 
Age: Late late Campanian to possibly early Maastrich- 
tian. Collector: unknown. 

LACMIP 10832. In the field on both sides of the E-W 
highway connecting Pentz and Chico, about 1.3 km 
N86°W of Pentz, Cherokee Quadrangle (7.5 minute, 
1949), Butte County, northern California. Chico For- 
mation, Pentz Road member (informal). Age: Early 
Campanian. Collectors: W. P. Popenoe and D. W. 
Scharf, August 15, 1931. 

LACMIP 10835. Loose blocks in landslide, SW % of SW 
% of section 8, T. 22 N, R. 3 E, Paradise Quadrangle 
(15 minute, 1953), Butte Creek, Butte County, northern 
California. Chico Formation, Ten Mile Member. Age: 
Early Campanian. Collectors: W. P. Popenoe and W. 
Findlay, September 3, 1933. 

LACMIP 17611. Outcrop in streambed of Dry Creek, 472 
m south and 152 m east of northwest corner of sec. 36, 
T. 21 N, R. 3 E, Cherokee Quadrangle (7.5 minute, 
1970), Pentz area, Butte County, northern California. 
Chico Formation, Pentz Road member (informal). Age: 
Early Campanian. Collector: E. Géhre, 2000-2002. 

LACMIP 22406. Gullies on both sides of highway ap- 
proximately 0.8 km straight W of Pentz, Cherokee 
Quadrangle (7.5 minute, 1970), Butte County, northern 
California. Chico Formation, Pentz Road member (in- 
formal). Age: Early Campanian. Collector: W. P. Po- 
penoe, July 18, 1946. 

LACMIP 23314. On W slope of gully near gully bed, 
about 640 m S28°W of NE corner of section 24, T. 1 
N, R. 1 E, of S side of Deer Valley, Antioch South 
Quadrangle (7.5 minute, 1973), Contra Costa County, 
northern Californa. Deer Valley formation (informal). 
Age: Late Maastrichtian Collector: W. P. Popenoe, Au- 
gust, 1944. 

LACMIP 23950 [= CAS 69106]. Gray mudstone in the 


The Veliger, Vol. 48, No. 2 


Page 104 


N bank, 732 m W and 610 m N of SE corner of section 
4, T. 29 N, R. 6 W, Ono Quadrangle (15 minute, 1952), 
Shasta County, northern California. Budden Canyon 
Formation, Gas Point Member. Age: Late Turonian. 
Collectors: W. P. Popenoe and W. A. Findley, 1933. 

LACMIP 24365. In fine-grained sandstone on left bank 
of French Creek [= Swede Creek], approximately 152 
m N and W of SE corner of section 5, T. 32 N, R. 2 
W, Millville Quadrangle (15 minute, 1953), Shasta 
County, northern California. Redding Formation, Fra- 
zier Siltstone Member. Age: Turonian. Collector: W. P. 
Popenoe, August 25, 1957. 

LACMIP 25431. Exposed in littoral zone and 3 to 6 m 
above high tide, S side of Punta San Jose, about 0.8 
km E of the point and 48 km airline S of Ensenada, 
Pacific coast of Baja California, Mexico. Rosario For- 
mation. Age: Late late Campanian to possibly early 
Maastrichtian. Collectors: W. P. Popenoe and W. Sliter, 
October, 1965. 

LACMIP 28780. Pentz, Butte County; northern Califor- 
nia. Chico Formation, Pentz Road member (informal). 
Age: Early Campanian. Collector: P. W. Reinhart, year 
unknown. 

LACMIP 30141. Fossils in pebbly sandstone, about 1.6 
km N of Nacimiento River on E side of road (?Bee 
Rock Road) near middle of northern-section line of 
section 18, T. 25 S, R. 10 E, Tierra Redonda Mountain 
Quadrangle (7.5 minute, 1949), San Luis Obispo Coun- 
ty, west-central California. El Piojo Formation. Age: 
Early late Maastrichtian. Collector: unknown. 

UCMP 814. South of Antone, between Rock Creek and 
Spanish Gulch, in sections 12 and 13 and SE % of 


section 11, T. 13 S, R. 24 E, Antone Quadrangle (7.5 
minute, 1985), Wheeler County, Oregon. Unnamed 
Cretaceous strata. Age: Cenomanian. Collector: un- 
known. 

UCMP A-6275. Rio de Santo Tomas, Punta China area, 
northwest Baja California, Mexico. Alisitos Formation. 
Age: Late Aptian. Collector: E. C. Allison. 

UCMP B-5320. Sea cliff on S side of Punta San Jose, 
Baja California, Mexico. Rosario Formation. Age: Late 
late Campanian to possibly early Maastrichtian. Col- 
lectors: E. C. Allison and E H. Kilmer, June 27, 1957. 

UCMP B-5665. In arenaceous bed 35 m stratigraphically 
below base of major volcanic-pyroclastic part of for- 
mation, upper Arroyo Ink, approximately 2 km due E 
of Punta China, Santo Tomas map (1:50,000, 1964), 
northwest Baja California, Mexico. Alisitos Formation. 
Age: Late Aptian. Collector: E. C. Allison. 

UO 461. Soft sandstone about 61 m above valley floor, 
NE side of Bridge Creek Valley, 0.8 km from and NW 
from Mitchell Rock, SE 4, SW % of section 26 and 
NE %4, NW % of section 35, T. 11 S, R. 21 E, Mitchell 
Quadrangle, Wheeler County, northeast-central 
Oregon. Hudspeth Formation, lower part of “Main 
Mudstone member.’ Age: Early Albian or early middle 
Albian. Collector: unknown. 

USGS M-175. 61 m E of the SW corner of sec. 33, T. 
18 N, R. 4 W, 2012 m S of point “1009 ft’? on Logan 
Ridge, Lodoga Quadrangle (15 minute, 1943), Colusa 
County, northern California. Probably float from lower 
Turonian Venado Sandstone Member of Cortina for- 
mation (informal). Collectors: R. D. Brown, Jr., and E. 
I. Rich, 1958. 


THE VELIGER 


© CMS, Inc., 2006 
The Veliger 48(2):105—109 (June 30, 2006) 


Temporal and Spatial Recruitment Patterns in Bankia martensi Stempell 
(Bivalvia: Teredinidae) 


L. A. SPORMAN, D. A. LOPEZ, AND M. L. GONZALEZ 


Universidad de Los Lagos, Laboratorio de Cultivos Marinos, Departamento de Acuicultura, Casilla 933, 
Osorno, Chile (e-mail: dlopez @ulagos.cl) 


Abstract. Temporal and spatial variations in the recruitment of Bankia martensi Stempell, 1899 (Teredenidae: Bival- 
via: Mollusca) were analysed in southern Chile. 

B. martensi is the only species of shipworm inhabiting Chilean waters and the cause of severe damage to wooden 
structures in the sea. Two experiments were carried out over a period of approximately 20 years, in Codihué (41°54'5; 
72°25'W) during 1979-1980 and Metri Bay (41°36'S; 72°42’W) during 2000-2001. Pine and oak panels were suspended 
at three depths and the density of recruits was determined based on the perforations or calcified cones produced when 
animals penetrate the wood. 

Recruitment patterns were similar during both series of experiments. Average recruitment density did not differ 
statistically, neither did the incidence of attacks on pine and oak panels. Similarly, no differences were registered between 
the occurrence of attacks on the upper or underside of the panels. Seasonal differences did occur with regard to the 
period of maximum recruitment, although in both locations recruitment was significantly lower in winter. No differences 
were registered at depths of over 3 m, and lower recruitment was registered on superficial panels only in Codihué. 

Results indicate continuous recruitment and low levels of temporal and spatial variability in spite of the different 
locations and periods when the data were collected. These patterns may be associated with the unpredictable presence 
of wood in the sea that is the specific substrate necessary for metamorphosis and adult development. B. martensi 
possesses reproductive characteristics that permit a constant supply of competent larvae, such as: reproduction throughout 
the year, early sexual maturity, alternative hermaphroditism and prolonged larval development, probably with teleplanic 


larvae. Low larval substrate selectivity also favours substrate colonization. 


INTRODUCTION 


There is only one species of wood-boring teredinid in 
Chile, Bankia martensi Stempell, 1899, which is the prin- 
cipal cause of attacks on wood in the sea (Stuardo et al., 
1970; Campos & Ramorino, 1990). Recruitment occurs 
throughout the year (Campos & Ramorino, 1990), al- 
though factors operating at different spatial and temporal 
scales can generate variations in recruitment intensity. 
Antecedents do exist with regard to seasonal variations 
(Stuardo et al., 1970) as well as differential attacks ac- 
cording to the particular physical characteristics of dif- 
ferent types of wood (Almuna et al., 1999). 

Teleplanic larvae, common among teredinids (Schel- 
tema, 1971), not only recruit on substrates at a distance 
from the breeders, but can also adjust their position in 
the water column in response to different environmental 
factors. In particular, reactions to light and depth are com- 
mon in competent larvae of bivalve molluscs (Jackson, 
1986). For this reason, the recruitment of B. martensi 
could vary seasonally according to the supply of larvae 
which is influenced by maturity periods and spawning 
factors, in addition to the degree of larval permanence 
and dispersion. It has been established that water circu- 


lation patterns (Varotto y Barreto, 1998) and the physical 
effect of water conditions on larval mobility (Gara et al., 
1997) can influence colonization in teredinids. Spatial 
variations in recruitment can be attributed to substrate 
characteristics and the position of larvae in the water col- 
umn (Turner, 1984; Baker & Mann, 2003). 

Recruitment of sessile or semi-sessile invertebrates can 
vary both spatially and temporally (Underwood & 
Keough, 2001), producing significant effects on popula- 
tions. Recruitment variations may determine the number 
of individuals that reach maturity, since they affect the 
survival (Bertness, 1989). Recruitment variations can also 
determine the reproductive potential and functional con- 
dition of individuals that reach maturity (Sutherland, 
1990). Evidence indicates that recruitment patterns ac- 
count for fluctuations in population size throughout the 
year and between years, as well as the age structure of 
open populations (Roughgarden et al., 1985). Neverthe- 
less, little is known about these aspects in terenids. 

This study aims to establish the recruitment patterns of 
the shipworm Bankia martensi by determining the effect 
of season, substrate location and type of wood in studies 
carried out during different periods and in different lo- 
cations. 


Page 106 


The Veliger, Vol. 48, No. 2 


MATERIALS AND METHODS 


Experiments were undertaken in two locations in southern 
Chile, with an interval of around 20 years between study 
periods. Experiments were initially carried out between 
October 1979 and October 1980 in the inlet of Codihué 
(41°45'S; 73°25'W) and then replicated in Metri Bay 
(41°36’S; 72°42'W) between November 2000 and No- 
vember 2001. The sites are separated by a distance of 
21.15 km, direct route. Both sites are located in the north- 
ern border of the Ancud Golf; Metri to the east of Re- 
loncavi Bay and Codihué to the west. Oceanographic and 
climatic conditions are similar in both sites. Surface water 
temperature followed a clearly seasonal pattern in both 
locations, with average maximum tides of 7 m. Average 
monthly temperatures in Codihué ranged from 9.5°C to 
16.8°C and in Metri Bay from 9.9°C to 17.5°C. Salinity 
in Codihué varied between 31%o and 35%o and in Metri 
Bay between 34%o and 35%o. 

Wood panels measuring approximately 20 x 10 x 5 
cm were suspended from long lines at three depths: su- 
perficial, between 0.5 and 1 m; middle, between 3 and 4 
m; and deep, between 6 and 8 m. Each group of 3 panels 
was placed at random, in triplicate. The panels were re- 
moved at monthly intervals and observed under a stereo- 
scopic microscope in order to determine the number and 
density of recruits, based on the perforations or calcified 
cones produced when animals bore into the wood (Turner 
& Johnson, 1971). 

Monthly registers for both locations and study periods 
were grouped seasonally, in order to establish temporal 
variability; spatial variability was determined by compar- 
ing recruitment at different depths on the upper and lower 
surface of each panel. Three-way variance analysis was 
used: season, depth and panel surface, following root 
transformation of data (Sokal & Rolph, 1969). The Tukey 
test was used for a posteriori analysis (Steel & Torrie, 
1985). 

Parallel to the above-mentioned experiments, degree of 
substrate selectivity was evaluated in both locations and 
study periods. For this purpose, panels of two types of 
wood were used: pine (Pinus radiata) and oak (Notho- 
fagus sp.), and recruitment monitored over a two month 


Table 1 


Two-way ANOVA of the number of Bankia martensi re- 
cruits in Codihué 1979-1980 and Metri Bay, 2000—2001, 
according to depth. 


Source of 

variation MS df F P 
Locality 0.006 | 0.46 0.49 
Depth 0.026 2 1.98 0.14 
Interaction 0.017 2 1.28 0.28 
Error 0.013 84 


period. The wood was selected according to antecedents 
presented by Almuna et al. (1999), establishing that pine 
is more susceptible to attacks by Bankia martensi than 
oak. Data were compared with a two way and single var- 
iance analysis following root transformation. Similarly, 
we established whether recruitment was at random, using 
x? according to Poisson. 


RESULTS 


Bankia martensi recruitment did not differ statistically e1i- 
ther according to depth or between two closely located 
sites in southern Chile, where evaluations spanning a pe- 
riod of around 20 years were undertaken (Table 1); av- 
erage density of recruits in Codihué during 1980, was 
0.57 + SE: 0.09 individuals-cm~* and in Metri during 
2000, 0.69 + SE: 0.07 individuals-cm ~. 

Recruit density on pine and oak panels did not differ 
either in Codihué (F = 0.93; df = 1:42; P < 0.001 or 
Metri (F = 0.78; df = 1:11; P > 0.001). 

Spatial distribution of recruits on pine and oak panels 
submerged in Metri Bay was at random, following the 
Poisson rule (x? = 14.38; df = 13; P > 0.05) 

B. martensi recruitment occurred throughout the year 
in both locations (Figure 1) and at all depths (Figure 2). 
Nevertheless, it was possible to differentiate periods of 
maximum recruitment. In Codihué (1980), highest levels 
were reached in spring/summer, with a drop in winter, 
when lowest recruitment levels were recorded (F = 
12.65; df = 3;29; P < 0.001). In Metri Bay, on the other 
hand, highest recruitment occurred during summer/au- 
tumn, with significant differences compared to the winter 
period (F = 14.5; df = 3:77; P < 0.001). 

Recruitment on the upper and lower surfaces of the 
panels did not vary, either in Codihué (F = 0.29; df = 
1;29; P = 0.10) or in Metri (F = 1.72; df = 1377; P = 
0.19) (Figure 3). 


@ Spring 
Summer 

2 Autumn 

N Winter 


0.6 


04 


Density (N°/cm’) 


0+ —— 


1979 - 1980 Years 2000 - 2001 


Figure 1. Average seasonal density + SE of Bankia martensi 
recruits in Codihué, 1979-1980 and Metri Bay, 2000-2001. 


L. A. Sporman et al., 2005 


Superficial 
1 7 Middle 
7 Deep 


0.9 - 
0.8 
0.7 

a 

— 0.6 

= es 

—] 

ZS 

= 04 

- 

@ 03 - 

o 

A 02 
0.1 
0 


1979 - 1980 2000 - 2001 


Years 


Figure 2. Average density + SE of Bankia martensi recruits at 
three depths, in Codihué, 1979-1980 and Metri Bay, 2000-2001. 


DISCUSSION 


Recruitment experiments were carried out on Bankia 
martensi in two sites in southern Chile, located close by, 
separated by an interval of around 20 years; results re- 
vealed low temporal variability. Recruitment occurred 
throughout the year in both locations, as recorded by 
Campos & Ramorino (1990), in studies undertaken in the 
area of Valparaiso, approximately 1000 km further north; 
this suggests that species reproduction-type is continuous, 
with successive gametogenic cycles during the year, 
which would account for the low degree of synchroni- 
sation between individual specimens. 

Seasonal variations between study sites can produce 
local variations during periods of maximum recruitment. 
However, lowest recruitment levels always coincided 
with lower temperatures (winter). In studies carried out 
along the coast of Concepcion, 600 km north of the sites 
being studied, Stuardo et al. (1970) recorded attacks on 
wood from the end of winter to the beginning of spring, 
suggesting that spawning would occur in spring and at 
the beginning of autumn. On occasions, B. martensi re- 
cruitment could occur considerably later than the spawn- 
ing periods, since planktonic larvae may be highly dis- 
persed, as generally occurs with veligers of the Teredi- 
nidae family (Scheltema, 1971). Thus competent larvae 
could colonize areas at a distance from the parental pop- 
ulation. Furthermore, it has been established that recruit- 
ment and metamorphosis could be delayed in the absence 
of the substrate necessary for settlement (wood). Under 
laboratory conditions, pedivelifer larvae swam actively 
for more than 100 days after fertilisation when wood was 
not available and metamorphosised around 60 days after 
fertilisation in the presence of wood (Campos & Ramo- 
rino, 1990). Various morphological changes occur during 
metamorphosis; among others the disoconch develops ini- 
tially along the anterior margin of the shell, creating a 


Page 107 
1.2 - 
Ws @ Upper 
| es 
a 
g 0.8 - 
S 
0.6 - 
i@p 7 
a7 
S 04 
BO: 
0.2 5 
0 = = — 
1979 - 1980 2000 - 2001 


Years 


Figure 3. Average density = SE of Bankia martensi recruits on 
the upper and lower surface of panels, in Codihué, 1979-1980 
and Metri Bay, 2000-2001. 


denticulated external border which permits wood boring. 
If this does not occur, recruitment is not possible (Campos 
& Ramorino, 1990). 

In Bankia martensis, as with other species of ship- 
worm, a selective adjustment of reproductive processes 
can be expected in response to the availability of wood 
in the sea. Larvae only settle and grow on this particular 
type of substrate, whose temporal availability is estocas- 
tic. Thus, reproductive success should be substrate-de- 
pendent to a greater extent than in other species of sessile 
invertebrates. Reproductive processes should also tend to 
maximise colonisation of the substrate, both spatially and 
temporally. In the case of Bankia martensi, in addition to 
the capacity to recruit and grow on various types of wood, 
this is expressed in year-round recruitment and larval set- 
tlement with no significant spatial and temporal varia- 
tions. These characteristics are the result of reproductive 
factors, such as early sexual maturity, successive game- 
togenic cycles, development of teleplanic larvae and her- 
maphroditism with autofertility, not necessarily protan- 
dric (Turner, 1973; Spormann, 2004). 

Planktonic larvae of many species of bivalves can ad- 
just their position in the water column in response to dif- 
ferent factors, such as light, depth, temperature, salinity 
and current. This affects substrate colonisation (Jackson, 
1986). The combined effect of light and pressure can de- 
termine variations in substrates located at different 
depths. Other factors such as the relative quantity of sed- 
iments and organic film on the upper and underside of 
substrates, could also cause recruitment levels to vary 
(Keough & Raimondi, 1995; Gara et al., 1997). In Bankia 
martensi, the only variations detected between study sites 
related to quantity of recruits on superficial panels. No 
variations were detected at greater depths, or between the 
different surfaces of the panels, confirming a low level 
of spatial variability in recruitment. 


Page 108 


In Bankia martensi the presence of mature specimens 
all year round has been verified, including smaller sizes. 
Similarly, hermaphroditism, although non-protandric, has 
been confirmed (Spormann, 2004). Studies of sexual 
phases revealed that all the teredinid species are protan- 
dric hermaphrodites (Nair, 1962; Turner, 1966; McKoy, 
1980; Hiroki et al., 1994). Hoagland (1978) has reported 
that due to the opportunist and sedentary nature of these 
species and the discontinuous availability of the substrate 
in the environment, they adopt protandry and minimise 
age of first reproduction, thus increasing reproductive po- 
tential. Nevertheless, non-protrandric hermaphroditism is 
even more favourable to an opportunist strategy. Repro- 
ductive maturity in females is reached early. Campos & 
Ramorino (1990) have reported specimens with a shell 
length of 2.5 mm emitting gametes; this size is reached 
on wood panels maintained for 2.5 months in the water. 

The larval development period in B. martensi plankton 
appears to be prolonged. Under laboratory conditions, 
wood boring starts 65 days after fertilization, and at 74 
days larvae have already bored into the wood (Campos 
& Ramorino, 1990). The length of the development pro- 
cess is similar to that of other species of this genus such 
as Bankia setacea (Townsley et al., 1966). Although data 
obtained under controlled conditions cannot be extrapo- 
lated to the natural environment, they do suggest a high 
capacity for larval dispersion. The length of the larval 
period and current velocity determine the distance be- 
tween recruits and parental population (Scheltema, 1971). 
The duration of the larval period has also been associated 
to population size (Jablonski, 1986) as well as to genetic 
continuity among populations (Scheltema, 1971). 

All these reproductive characteristics tend to maximise 
colonisation on unpredictable substrates (Tuente et al., 
2002), given that longevity depends on the size and per- 
ishable characteristics of the substrate where larvae re- 
cruit and grow. For this reason, difficulties have been en- 
countered in controlling attacks on wood. 

Efforts have been made to control shipworm wood at- 
tacks using chemical compounds that can operate at three 
levels: preventing larval settlement, increasing mortality 
prior to total settlement or provoking mortality after set- 
tlement (Gitidice, 1999). Copper compounds and organ- 
ometalic compounds such as tributylium fluoride (TBTF), 
triphenytin fluoride (TPTF) and tributylton oxide (TBTO) 
have been used in antifouling paints (Gitidice, 1999). 
However, antecedents indicate that they pollute the en- 
vironment, in particular the latter compounds (Huggett et 
al., 1992). The need to settle on a specific type of sub- 
strate would limit the selectivity of competent larvae with 
respect to other substrate characteristics, as a result of 
which attacks on a wide variety of wood are to be ex- 
pected. Although antecedents of differential attacks by 
teredinids do exist (Nair, 1962; Turner, 1984) including 
B. martensi (Stuardo et al., 1970; Almuna et al., 1999), 
it has been established that this species can attack all 


The Veliger, Vol. 48, No. 2 


types of wood, although with greater intensity on soft as 
opposed to hard woods (Stuardo et al., 1970). Neverthe- 
less, a high degree of variability in attacks on panels of 
the same type of wood has been recorded (Stuardo et al., 
1970; Almuna et al., 1999), which indicates estocastic 
processes associated with a complex group of factors that 
determine physical contact between larvae and substrates. 
Results obtained in the present study indicate that fre- 
quency of attacks on pine is similar to that of attacks on 
oak and that recruitment was at random. 


Acknowledgments. The contributions of the Research Depart- 
ment of the Universidad de Los Lagos DIULA N° 3580 and of 
the Universidad de Valparaiso DIPUV N° 32-2300 are gratefully 
acknowledged. The support of the Master in Science Programme 
of the Universidad de Los Lagos is also much appreciated as is 
the collaboration of two anonymous referees for their valuable 
suggestions. Our thanks also to José M. Uribe for his work in 
the field and to Susan Angus for the translation of the manuscript. 


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HOAGLAND, E. K. 1978. Protandry and the evolution of environ- 
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The Veliger 48(2):110-115 (June 30, 2006) 


THE VELIGER 
© CMS, Inc., 2006 


Two Introduced Pest Slugs: Tandonia budapestensis New to the Americas, 
and Deroceras panormitanum New to the Eastern USA 


HEIKE REISE 
Staatliches Museum fiir Naturkunde Gorlitz, PF 300154, 02806 Gorlitz, Germany 
(e-mail: Heike.Reise@smng.smwk.sachsen.de) 
JOHN M. C. HUTCHINSON 


Max-Planck-Institut fiir Bildungsforschung, Lentzeallee 94, 14195 Berlin, Germany 
(e-mail: hutch @mpib-berlin.mpg.de) 


AND 


DAVID G. ROBINSON 


USDA APHIS PPQ, Department of Malacology, Academy of Natural Sciences, 1900 Ben Franklin Parkway, 
Philadelphia, Pennsylvania 19103, USA (e-mail: robinson @ansp.org) 


Abstract. 


This paper reports new findings in North America of two pest slugs from Europe. Tandonia budapestensis, 


previously unknown from America, was found in Washington DC and near Philadelphia. Deroceras panormitanum, 
unreported from the Eastern United States and from Eastern North America outside of greenhouses, was found in 
Washington DC. We describe how to recognize these species and briefly summarize knowledge of their distribution and 


ecology. 


INTRODUCTION 


Since the classic monograph of Pilsbry (1939-1948), a 
number of papers have dealt further with introduced ter- 
restrial mollusks in North America (e.g., Hanna, 1966; 
Chichester & Getz, 1969; Dundee, 1974, 1977; Rollo & 
Wellington, 1975; Roth & Pearce, 1984; Forsyth, 1999). 
However, in the last twenty years rather little has been 
published on this topic. This is surprising as the intro- 
duced species tend to dominate the malacofauna in dis- 
turbed habitats, and consequently are economically the 
most important pests. They are often also significant pests 
in their countries of origin (Godan, 1979, 1983). Without 
knowing the present distribution of an introduced species, 
or even if it is present in North America, the US De- 
partment of Agriculture’s Animal and Plant Health In- 
spection Service’s Plant Protection and Quarantine divi- 
sion (USDA APHIS PPQ) lacks the basis to determine 
whether a mollusk species intercepted on an imported 
commodity represents a potential novel agricultural or en- 
vironmental threat. 

In Europe the spread of some recent introductions has 
been followed in detail (e.g., De Wilde et al., 1986; von 
Proschwitz, 1996; Reise et al., 2000). In contrast, in 
North America the density of recording of terrestrial mol- 
lusks has been much lower. Consequently with novel re- 
cords there must often be uncertainty about how long ago 
the introduction had occurred. Nevertheless such initial 


reports are important in providing a baseline for later 
studies that follow up the subsequent survival and spread. 
Introductions of some species started long ago and have 
occurred repeatedly (e.g., Arion subfuscus (Draparnaud, 
1805): Chichester & Getz, 1969; probably also Arion sil- 
vaticus Lohmander, 1937: Geenen et al., 2003). However, 
other species might well have been introduced only very 
recently, as seems very probable with Boettgerilla pallens 
Simroth, 1912, since it has spread from the Caucasus 
through Europe only within the last few decades (Reise 
et al., 2000). Species currently unknown in North Amer- 
ica are frequently reported on incoming cargo (Robinson, 
1999). 

Species not yet reported for North America are liable 
to be overlooked because of the difficulties of identifi- 
cation when the North American literature does not deal 
with them. The problem is worse for slugs, because the 
lack of shell deprives them of many more obvious iden- 
tification characters. For unfamiliar species often the 
clearest characters require dissection, which is always 
necessary for some species. To further complicate the 
matter, ongoing research among malacologists in Europe 
has shown that several of the Palearctic taxa actually rep- 
resent complexes of closely related or superficially sim- 
ilar species: e.g., Arion hortensis Férussac, 1819 s.1. (Da- 
vies, 1979; Backeljau, 1987); A. subfuscus s.1. (Pinceel et 
al., 2004); Arion fasciatus (Nilsson, 1823) s.1. (Backeljau 


H. Reise et al., 2005 


et al., 1987; but see Jordaens et al., 2000). More anatom- 
ical evidence, perhaps coupled with molecular data, needs 
to be used to determine which members of these species 
complexes are present on the North American continent. 

This paper reports occurrences that considerably ex- 
tend the range of two pest slugs from Europe: Tandonia 
budapestensis (Hazay, 1881), previously unreported from 
America, and Deroceras panormitanum (Lessona & Pol- 
lonera, 1882), unreported from the Eastern United States 
and from Eastern North America outside of greenhouses. 
Because of its greater novelty, we give more details on 
identification and ecology of 7. budapestensis than of D. 
Ppanormitanum. 


COLLECTION DETAILS 


H.R. and J.M.C.H. found three juvenile specimens of 7. 
budapestensis on 28 July 1998 along Rock Creek in 
Washington DC (38°54.48'N, 77°03.24'W). The habitat 
was broad-leaved woodland along the slope above the 
creek, without much ground flora, but with garbage and 
flood debris. The specimens were raised in the laboratory 
for differing periods and then dissected to confirm iden- 
tification. Two specimens are stored in the collection of 
the State Museum of Natural History Go6rlitz, Germany 
(p13048 and p13049). 

Two adult specimens of 7. budapestensis were collect- 
ed on 29 May 1999 by Richard Horowitz (of the Acad- 
emy of Natural Sciences, Philadelphia) from under a de- 
caying log in Carroll Park, north bank of Cobbs Creek, 
south of Old Manor Road, Havertown, a suburban park- 
land area in Delaware County, just west of Philadelphia, 
Pennsylvania (39°58.78'N, 75°16.95’W). One specimen 
has been deposited in the collection of the Academy of 
Natural Sciences, Philadelphia (ANSP A 19999), the oth- 
er in the USDA National Mollusk Collection (USDA 
10294). In addition to the anatomical evidence, the iden- 
tity of the latter specimen was confirmed by matching 
DNA sequencing data from conspecific specimens from 
the United Kingdom and Belgium, by Douglas Prasher of 
the USDA APHIS PPQ Center for Plant Health, Science 
and Technology. 

H.R. and J.M.C.H. found two specimens of D. pan- 
ormitanum on 29 July 1998 outside the National Museum 
of Natural History on Constitution Avenue, Washington 
DC (38°53.50'N, 77°01.57'W). They were collected in 
litter under rhododendron bushes, surrounded by a sparse 
lawn; this was shaded by the museum building, and pe- 
riodically watered. Determination was based on genital 
anatomy. They are stored in the State Museum of Natural 
History Go6rlitz, Germany (p13050). 


TANDONIA BUDAPESTENSIS 
Taxonomy and Appearance 


Tandonia budapestensis (the Budapest slug) is a mem- 
ber of the Milacidae, a family of less than 50 species, 


Page 111 


with a center of distribution in the Balkans (Wiktor, 
1981). Until Wiktor’s taxonomic review of 1981, 7. bu- 
dapestensis was usually included in the other genus of 
the family, Milax. Milax gracilis (Leydig, 1876) is a syn- 
onym. In Britain it was not distinguished from Tandonia 
sowerbyi (Férussac, 1823) until Phillips & Watson’s paper 
of 1930. 

Like other milacids, 7. budapestensis has a prominent 
keel running from the tail to the rear of the mantle, the 
pneumostome is at the rear half of the mantle, and a 
horseshoe-shaped groove runs around the central part of 
the mantle. 7. sowerbyi, Milax gagates (Draparnaud, 
1801), and Milax nigricans (Philippi, 1836) are the other 
widespread synanthropic Milacidae in Western Europe 
(and M. gagates is known from North America), but T. 
budapestensis is slenderer and when resting often curls 
round into a C shape (Figure la), whereas these others 
hunch up into a bilaterally symmetrical dome (Kerney & 
Cameron, 1979). Boettgerilla pallens is another species 
known from North America with a long keel, but it is 
much paler, smaller, and wormlike (Reise et al., 2000). 
In color T. budapestensis is somewhat polymorphic, but 
usually of a dark dirty appearance due to dense dark 
speckling on a dull cream or orange background (Figure 
1b); the keel stands out owing to its lighter olive or dull 
orange color. However, in alcohol it is only the black 
pigment that remains prominent. The length when crawl- 
ing is 50-70 mm. For other characters, including anato- 
my, see Phillips & Watson (1930), Wiktor (1987) and 
Barker (1999). 


Ecology and Distribution 


The original range of this European species is probably 
the southern Alps and northern Balkans (Wiktor, 1987). 
However, it is now known from Turkey to northernmost 
Great Britain and Iceland, and in much of this range is 
clearly a still-spreading introduction, as it is in New Zea- 
land (Waldén, 1966; Wiktor, 1987; Barker, 1999; Kerney, 
1999). Waldén’s collection from Iceland was not restrict- 
ed to greenhouses (contra Kerney & Cameron, 1979; T. 
von Proschwitz, personal communication). Previous re- 
ports from America seem unreliable. Godan (1979:63) re- 
fers to occurrences in America, Hawaii and Australia, but 
this must have been a misprint (these localities are listed 
for M. gagates earlier in the book; we can find no such 
records for 7. budapestensis before or since). She else- 
where refers to interceptions of 7. budapestensis on ship- 
ments to the USA based on the “Lists of intercepted plant 
pests”’ of the ‘“‘Plant Protection and Quarantine Programs, 
Animal and Plant Health Inspection Service, US Depart- 
ment of Agriculture.’’ These lists record incidents of pests 
being discovered, at which point the plants would be fu- 
migated, incinerated or returned to the country of origin, 
so they are not cases of introductions. Moreover, D.G.R.’s 
redetermination of a sample of such records of a variety 


The Veliger, Vol. 48, No. 2 


Figure 1. (a) Tandonia budapestensis in its typical C-shape resting position within a soil cavity that was topped by a board. The eggs 
could well be from this specimen. (b) A pair of mating 7. budapestensis, as the species is commonly encountered because of its 
prolonged copulation (typically from evening to midday: Quick, 1960). Both pictures from Nork Park allotments, Banstead, Surrey, 


England. (c) Deroceras panormitanum, from England. 


of species has shown that the lists prior to 1993 are fre- 
quently based on faulty identification. Based on later re- 
cords, Robinson (1999) reported 7. budapestensis as oc- 
curring in <0.1% of interceptions, but this was based on 
a single juvenile specimen tentatively identified as this 
species, whereas other intercepted Tandonia from the 
same country of origin have all been 7. sowerbyi. Thus, 
despite the enormous volumes of imported commodities 
from Europe over the years, T. budapestensis has not 
been definitively identified among the many slug speci- 
mens intercepted by the USDA. 


Tandonia budapestensis is the commonest milacid in 
Britain, where its habitat includes gardens, ploughed 
fields, waste ground and woods that have been subject to 
some disturbance (Kerney, 1999). In Central Europe it 
has been observed to be associated with lowland plains 
rather than hilly areas (Dvorak et al., 2003). It occurs 
amongst litter, and is often easiest to find under wood and 
stones, but it also burrows up to 37 cm underground (Ste- 
phenson, 1966) and over summer the entire population in 
potato fields can temporarily disappear deeper than 15 cm 
(Wareing & Bailey, 1989). In Western Europe it can be 


H. Reise et al., 2005 


a serious pest on arable land, particularly of potatoes and 
other root crops, and some ornamental flowers (Van den 
Bruel & Moens, 1958; Godan, 1979, 1983; South, 1992), 
and in captivity at least it also eats grain seeds and seed- 
lings (Duthoit, 1964). Its underground habits make it less 
susceptible to control both by poison bait and cultivation 
(Symondson, 1997), but it is not so consistently a prob- 
lem as some other slug pests (South, 1992). 

In England the eggs hatch in spring and summer. The 
rate of development of both eggs and young is strongly 
dependent on temperature, being very slow at 5°C (Hunt- 
er, 1966a; Stephenson, 1966). Adults mature and mate in 
late autumn and winter, but this is usually their second 
winter, and they die off by August (Bett, 1960; Hunter, 
1966a). However, in the more continental climate of the 
Czech Republic and Slovakia, mating slugs are found 
mostly in summer (Hudec, 1963). 

For other aspects of its biology see Hunter (1966b) and 
literature cited in South (1992) and Symondson (1997). 


DEROCERAS PANORMITANUM 


This species has formerly been referred to as D. caruanae 
(Pollonera, 1991), which is now generally considered as 
a synonym (Wiktor, 2000). It is believed to originate from 
the Mediterranean, where there are several similar forms 
whose taxonomic status is still controversial (Wiktor, 
2000). 

In appearance it has a watery thin transparent skin 
(Figure 1c). Individuals vary from light grayish brown to 
chocolate brown, to almost black, and this is fairly uni- 
form over the body; the fine dark spotting usually present 
is only obvious under magnification. In North America it 
is most readily confused with Deroceras laeve (O. FE 
Miller, 1774), some morphs of which resemble D. pan- 
ormitanum much more closely, especially in size, than do 
specimens from Europe. In fact at the same site in Wash- 
ington DC where we collected the two D. panormitanum 
we collected 12 other specimens which we considered to 
be conspecific, but which upon dissection turned out to 
be aphallic or hemiphallic and thus were presumably D. 
laeve. Barker (1999) gives the pale rim to the pneumo- 
stome of D. panormitanum as a character distinguishing 
these species, but our examination of European and North 
American material has shown that it is sometimes not 
pale in D. panormitanum and it is often pale in D. laeve. 
A considerably more reliable character, although not clear 
in all specimens, is the shape of the tail (de Winter, 1988): 
seen in profile, the tail of D. panormitanum rises up from 
the sole vertically, or even curves backwards, whereas in 
D. laeve it slopes forward. The difference may exist be- 
cause in D. panormitanum a flattening and enlargement 
of the tail accompanies its use in courtship (H.R., per- 
sonal observation; Barker, 1999), but the character is still 
visible in non-courting individuals, especially if gently 
irritated. The difference is also usually apparent in alco- 


Page 113 


hol-preserved specimens. In Europe there are other ex- 
ternally very similar species such as Deroceras sturanyi 
(Simroth, 1894). 

Deroceras panormitanum has colonized large areas of 
Europe away from the Mediterranean and is still spread- 
ing (e.g., only recently reported for Poland (Wiktor, 
2001)). It occurs mainly in disturbed sites but in Britain, 
for instance, is also found in wilder habitats such as 
woods and sea cliffs (Kerney & Cameron, 1979; Kerney, 
1999). In Fennoscandinavia it occurs only in greenhouses 
(Waldén, 1966; von Proschwitz, 1993). It has also been 
introduced to the Canary Islands, South Africa, Colom- 
bia, Australia, New Zealand, Tristan da Cunha and even 
Marion Island 47°S (Smith, 1992; Barker, 1999; Preece, 
2001; Hausdorf, 2002). The first report in North America 
is from California where it was already widespread in the 
Bay Area by 1940 (Pilsbry, 1939-1948). The next report 
was from two greenhouses in Quebec (Chichester & Getz, 
1969), and it is now widespread in synanthropic habitats 
in the Pacific Northwest, both in the USA and Canada 
(Rollo & Wellington, 1975; H.R. & J.M.C.H., personal 
observation). But we know of no outdoor records from 
the East, nor any records from the Eastern United States. 
This is surprising as the USDA regularly intercepts the 
species on a wide variety of commodities, particularly on 
cut flowers and fresh fruits and vegetables from Colom- 
bia, Panama, the Netherlands, and New Zealand (D.G.R.., 
personal observation). Earlier records of interceptions 
into the USA cited by Godan (1979, 1983) and Dundee 
(1974) suffer from the same unreliability of the USDA 
lists as discussed above for T. budapestensis. 

Deroceras panormitanum can be important as a pest in 
pastures, nurseries, greenhouses, gardens and commercial 
crops such as asparagus and lettuce (Castillejo et al., 
1996; Barker, 1999), but seems not to be mentioned as a 
significant pest of cereals or root crops. In a 1988 survey 
of 372 gardens in Manchester, England, it was found in 
258 of them, more than any other slug (North & Bailey, 
1989). 

It may be helpful to note that Quick (1960) rightly 
questioned Gregg’s (1944) interpretation of the life cycle 
of D. panormitanum in California: probably the study 
population was mixed with D. laeve. 


CONCLUSION 


As mentioned above, the sparse recording of intro- 
duced slugs in North America makes it likely that T. bu- 
dapestensis and D. panormitanum are already more wide- 
ly distributed there than these three new records indicate. 
In an effort to collect slug data from throughout the Unit- 
ed States and Canada, and map the distributions of all 
introduced species, the USDA APHIS PPQ initiated in 
1998 the North American Slug Project (NASP), encour- 
aging any interested malacological workers to collect and 
submit slug specimens for identification. Most submitted 


Page 114 


slugs have been dissected to confirm identity, and sam- 
ples have been DNA sequenced to add to the national 
database. A number of individual State Departments of 
Agriculture have also participated in NASP over the last 
five years, and slug surveys have been conducted in a 
number of states under the Cooperative Agriculture Pest 
Survey (CAPS) program, producing vast amounts of data 
that is still being collated and analyzed. Although our 
understanding of the distribution of a large number of 
Palearctic species is now far better than before, NASP 
has not turned up additional records of T. budapestensis 
or D. panormitanum other than the latter from regions 
where it was already known. 

However, since the original submission of this manu- 
script, one of us (J.M.C.H.) spent one week in summer 
2004 surveying synanthropic habitats in the Denver re- 
gion of Colorado. D. panormitanum was widespread and 
common in garden centers, often together with externally 
very similar D. /aeve, but it also turned up in a park-like 
habitat along the unkempt grassy bank of a drainage 
ditch. This confirms our suspicion that it might occur 
more widely east of the Rocky Mountains. 


Acknowledgments. Gary Bernon alerted H.R. and J.M.C.H. to 
the novelty of their finding of 7. budapestensis. We thank Ted 
von Proschwitz for checking the label of Waldén’s sample of D. 
panormitanum from Iceland, and D. Godan for answering our 
inquiries about the sources of information for her book. Wolf- 
gang Junius took the photograph for Figure 1c. We thank Richard 
Horowitz for collecting the 7. budapestensis specimens from the 
Philadelphia area. Thanks also to Joseph Cavey, Tim Pearce and 
an anonymous referee for comments on the manuscript. 


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The Veliger 48(2):116—120 (June 30, 2006) 


THE VELIGER 
© CMS, Inc., 2006 


Larval and Early Juvenile Development in Tegula funebralis (Adams, 1855) 
(Gastropoda: Trochidae) in Baja California Sur, México 


SERGIO A. GUZMAN be PROO,!} TEODORO REYNOSO-GRANADOS,? 
PABLO MONSALVO-SPENCER,’ AND ELISA SERVIERE-ZARAGOZA?** 


' Escuela Nacional de Ciencias Bioldgicas, Laboratorio de Ecologia, IPN. Prolongaci6n de Carpio y Plan de Ayala 
s/n, México, D.E 02800, México 
> Centro de Investigaciones Biolégicas del Noroeste (CIBNOR), Mar Bermejo 195, Col. Playa Palo de Santa Rita, 
La Paz, B.C.S. 23090, México 
3 COFAA Grant Fellow 


Abstract. Larval and early juvenile development in Tegula funebralis was observed for 63 days under static culture 
conditions at temperatures ranging from 19°C—20°C. The post-larvae were fed Phaeodactylum trichornotum microalgae. 
Embryonic development from fertilized egg in vitro to competent larval stage lasted 8 days. Teleoconch secretion 
occurred on day 11. Very fine longitudinal striations, appearing on the anterior edge of the teleoconch on day 14, became 
parallel ribs extending from the teleoconch to the protoconch in juvenile stages. The shell aperture acquired a fanlike 
shape and the dextrally coiled spire rose, becoming conical on day 48. 


INTRODUCTION 


Along the central Pacific coast Baja California, the com- 
munity associated with abalone (Haliotis spp.) banks in- 
cludes a variety of gastropod species. Most common, in 
terms of frequency and abundance, are Megastraea (= 
Astraea) undosa (Wood, 1828), Megathura crenulata 
(Sowerby, 1825), and species of the genus Tegula (Guz- 
man del Proo et al., 1991). Tegula funebralis is widely 
distributed in the intertidal zone of the Pacific coast of 
the Baja California Peninsula (Guzman del Proo et al., 
1991). Other species of this genus, 7. aureotincta 
(Forbes, 1850), T. eiseni (Jordan, 1936), and T. regina 
(Stearns, 1892), share the habitat of H. fulgens in the 
subtidal zone of Bahia Tortugas (Carre6n-Palau, 2000). 

From recent studies on microhabitat and recruitment in 
juvenile Haliotis spp. (Carre6n-Palau, 2000; Carre6n-Pa- 
lau et al., 2003) and some preliminary experiments on 
settlement of post-larval abalone in artificial collectors 
(Ponce-Diaz, 2004) in this area, the need to identify post- 
larval and early juvenile stages of the gastropods asso- 
ciated with the abalone rocky reefs has emerged. These 
species share a habitat and overlap in their spawning sea- 
son, September to November (Belmar et al., 1991; Bel- 
mar & Guzman del Préo, 1992; Guzman del Proo, un- 
published data). 

Identification of these early life history stages has 
proved difficult because there is a dearth of literature on 
reproduction and development of members of the Tro- 
chidae (C. S. Hickman, quoted in Kulikova & 


* Corresponding author, e-mail: serviere04 @cibnor.mx 


Omel’yanenko, 2000). Consequently, in the laboratory, 
the authors have been culturing the major gastropods 
sharing the habitat of Haliotis spp. to obtain reference 
collections that will assist in identifying larval and early 
juvenile stages of these gastropods. 

Larval development in 7. funebralis (Adams, 1855) 
was described by Hewatt (1934) and later by Moran 
(1997) for a population in Oregon. This study presents 
results from a population in Baja California Sur, about 
2500 km to the south. Here, females were induced to 
spawn. Detailed drawings of the development, which 
complements available information, will facilitate future 
identification of the early stages of this species in all of 
its range. 


MATERIALS anp METHODS 
Collection and Maintenance of Specimens 


We collected 60 adult specimens of 7. funebralis (basal 
diameters 22—26 mm, shell height 15—20 mm, and total 
weight 5.17—8.04 g). The specimens were collected in the 
rocky intertidal zone of Bahia Tortugas, B.C.S. (27.7°N, 
114.9°W) in January 2002. The specimens were trans- 
ported in a cooler, maintaining humid conditions by lay- 
ering the specimens between folds of giant kelp (Macro- 
cystis pyrifera) leaves with an interior temperature of 
10°C. 

In the CIBNOR laboratory, the specimens were placed 
in 40-L plastic aquariums. Seawater in the aquariums was 
kept between 18°C—20°C with constant aeration. The 
specimens were fed rehydrated giant kelp (M. pyrifera) 
leaves. Water and food were replaced every other day. 


S. A. Guzman del Proo et al., 2005 


Gonad Conditioning 


To attain maximum gonad development, specimens 
were fed ad libitum and the water kept between 18°C-— 
20°C. Five snails were sacrificed weekly to monitor the 
stage of gonadal maturation by microscopic observations 
of gametes. Color of gonads (cream in males and moss 
green in females) provided determination of gender. 


Induction of Spawning 


After 60 days of gonadal conditioning, spawning was 
induced. Fifteen snails were removed from the aquarium 
(about 20°C) and were exposed to air for 30 min at 19°C 
in the shade and for 15 min at 29°C in the sunlight. They 
were then subjected to abrupt temperature shifts in sea- 
water: the snails were returned to an aquarium at 16°C, 
then to an aquarium at 25°C. The cold and warm treat- 
ment was done twice, holding the specimens in each 
aquarium for 30 min. The snails were then returned to 
the 40-L aquarium. About 24 hr after thermal stimulation, 
only unfertilized eggs were found on the bottom of the 
aquarium. These eggs were fertilized with sperm extract- 
ed form dissected males (1 oocyte/15 sperm). 


Sieving of Embryos and Larvae 


Embryos were cultured in 16-L tanks and benthic 
phase specimens in 20 X 30 X 5 cm trays. Seawater was 
passed through a filter (1 wm pore size). Larvae were 
sieved through Nytex mesh (236, 160, 140, and 100 wm 
pore size) to remove organic waste. Sieving was done 
every 48 hr throughout the experiment. Benthic post-lar- 
vae were fed Phaeodactylum tricornotum (Bohlin, 1974) 
microalga. A video monitor attached to a microscope was 
used to observe and record morphological changed as- 
sociated with larval and early juvenile development 
through day 63. Drawings were made from video images 
by tracing the outline and the main features of each stage 
directly from the TV screen. Mean (+SD) length of all 
stages was based on a sample of five individuals at each 
stage. From the veliger stage onward, size refers to the 
long axis of the shell. Seawater in the aquariums was kept 
at 19°C—20°C during growth phases through day 63. 


RESULTS 


Removal and maintenance of adult 7. funebralis in cool- 
ers with a humid environment proved effective. No deaths 
occurred following 14 hr of transport. In the laboratory, 
the specimens ate the food supplied (rehydrated M pyri- 
fera) as their regular diet throughout the experiment. 
Induced spawning had positive results in females, 
while males failed to spawn. Jn vitro fertilization was 
successful, allowing subsequent observation of larval de- 
velopment. Observations were made from the time of fer- 
tilization through the early juvenile phase. The following 


Page 117 


descriptions identify the stages and more prominent fea- 
tures during early development of the species (Figure 1). 


Embryonic Development 


Day 1. Fertilized eggs range in diameter, 145 + 5 pm. 
Eggs are enclosed in a membrane with outside diameter 
175 + 5 wm, with a thick, additional gelatinous cover 
140-320 wm thick (1). Eggs are bright green, remaining 
so throughout larval development. First cleavage occurs 
at 35—45 min, resulting in two same-sized cells (2). Sec- 
ond cleavage occurs at 55—65 min, forming four cells (3). 
Third cleavage occurs at 1—2 hr, forming eight cells. Sub- 
sequent cleavages occur after 2 hr (4). The ciliated gas- 
trula (S—6 hr) remain enclosed in the egg membrane, at- 
taining a diameter of 155 + 15 ym diameter (5). Invag- 
ination of the posterior end occurs (6), which corresponds 
to the shell gland. Trochophore forms at 9—10 hr, reaching 
a length of 160 + 10 pm (7). After elongation, proto- 
trochal girdle begins to develop at one end (8) and two 
lateral tufts of cilia appear on its base (9). Early veligers 
form at 21—22 hr and are 200 + 10 pm long (10). Velum 
(11) and primordium of the foot (12) are present. Shell 
covers the entire body (13) except the velum. 


Day 2. Veliger larvae after torsion, 223 + 16 wm long 
(14). Cephalo-pedal mass (15) with operculum (16). The 
velum branches into two sections (17) and lengthens pos- 
teriorly to form cephalic tentacles. Foot displays retractile 
movements and larvae swim with irregular motions. 


Days 4-7. Late veligers are 226 + 10 wm long (18). 
Larvae withdraw into shell. Formation of the first whorl 
occurs. Eye spots are apparent (19). Shedding of cilia 
begins (20). Larvae exhibit exploratory movements in 
search of attachment substrates. 


Benthic Phase 


Day 8. Post-larvae are 240 + 12 pm (21a). Cephalic 
tentacles (22) and mouth (23) appear, and operculum be- 
comes prominent (24). A few remnants of cilia tufts re- 
main but with little motility (25). All larvae have settled. 


Day 11. Post-larvae are 255 + 10 wm long (21b). When 
the first suture forms, it separates the protoconch from 
the teleoconch, which now begins to develop (26). 


Juveniles 


Day 14. Juveniles are 271 + 10 wm long (27a). Very fine 
longitudinal striations start to form on the anterior edge 
of the teleoconch (28). 


Day 22. Juveniles are 290 + 20 pm long (27b). Longi- 
tudinal striations become more conspicuous and take the 
shape of ribs running the length of the shell (29). Trans- 
verse sutures in the teleoconch increase (30). Shell spiral 


Page 118 The Veliger, Vol. 48, No. 2 


e7b ZC 2Td Ss 


Figure 1. Developmental stages of Tegula funebralis from egg to 48 days. (1) Fertilized egg. (2) First cleavage. (3) Second cleavage. 
(4) Morula. (5) Gastrula. (6) Shell gland. (7) Embryonic trochophore. (8) Proto-trochal girdle. (9) Lateral cilia. (10) Early veliger. (11) 
Velum. (12) Foot primordium. (13) Shell. (14) Veliger after torsion. (15) Cephalo-pedal mass. (16) Operculum. (17) Branching of velum. 
(18) Late veliger. (19) Eye spots. (20) Shedding of velum. (21a,b) Post-larvae. (22) Cephalic tentacles. (23) Mouth. (24) Operculum. 
(25) Remnant cilia. (26) First suture. (27a,b,c,d) Juvenile. (28) Longitudinal striations. (29) Ribs. (30) Transverse sutures. (31) Spire. 


(32) Cephalic tentacles. (33) Shell aperture. (34) Dextrally coiled shell. Bold numbers = different stages, normal numbers = morpho- 
logical characters. 


S. A. Guzman del Proo et al., 2005 


Table 1. 


Development time in Tegula funebralis from embryo to 
juvenile under laboratory conditions with temperature 
range of 19°C—20°C. 


Stage Time 

First cleavage (two cells) 35-45 min 
Second cleavage (four cells) 55-65 min 
Third cleavage (eight cells) 12h 
Ciliated gastrula 5-6 h 
Trochophore 9-10 h 
Early veliger 21-22 h 
Veliger 2 days 
Late veliger 4-7 days 
Settlement (benthic phase), two cephalic 

tentacles 8 days 
Postlarva: suture separates proto-conch from 

teleoconch 11 days 
Juvenile: fine longitudinal striations 14 days 
Juvenile: ribs running the length of the shell, 

cephalic tentacles with 12 papillae 22 days 
Juvenile: Cephalic tentacles with 18 papillae 34 days 
Juvenile: Cephalic tentacles with 21 papillae 43 days 
Conical shell 48 days 


is more evident (31). Cephalic tentacles have 12 papillae 
each. 


Day 34. Juveniles are 380 + 60 pm long (27c). Longi- 
tudinal ribs and transverse sutures become very evident. 
Cephalic tentacles have 18 papillae (32). 


Day 43. Juveniles attain length of 455 + 30 ym; cephalic 
tentacles have 21 papillae each. 


Day 48. Juveniles are 463 + 9 p long (27d). Shell ap- 
erture is now fan-shaped (33); dextrally coiled spire rises, 
becoming conical (34). Juvenile appearance remains un- 
changed from this day through day 63, when the exper- 
iment ended. Table | and Figure 1 summarize the stages 
of development. Figure 2 summarizes growth during the 
experiment. The rate of growth was about 5.6 4m day !. 


DISCUSSION 


Maintenance of 7. funebralis under laboratory conditions 
posed no problems. Specimens adapted easily to feeding 
on rehydrated M. pyrifera foliage. The induction to spawn 
through different methods (thermal shock, desiccation, 
hydrogen peroxide, UV-radiation of seawater, etc.) has 
been used in gastropods (Kikuchi & Uki, 1974; Holyoak, 
1988; Gonzalez et al., 1999; Leighton, 2000). In this 
study, although different temperatures and times to 
spawning induction were assayed, it was possible to ob- 
tain the spawning of females only. This species is natu- 
rally adapted to drastic thermal changes in their environ- 
ment, the intertidal zone, which may be related to its lim- 
ited response to changes in temperature. 


Page 119 
600 - 
ys 
500 - = 
= ant 
8 400 - yet 
= Joe 
SD 4 
5 300 os ~‘ 
2 ave ae y =5.6x+185.4 
100 - R°=0.9 


0+ T een ram 


0 5 10 15 20 25 30 35 40 45 50 55 60 65 


Age (days) 
Figure 2. Post-larval and juvenile growth of Tegula funebralis. 
Day O corresponding to veliger stage. ® = average of 5 mea- 
surements. 


Release of oocytes was an important factor for the suc- 
cess of the experiment because of attempts to obtain 0o- 
cytes through gonadal dissections failed. Female gamets 
have very fragile membranes that break when manipu- 
lated for artificial fertilization. Oocytes released into the 
water suggest that fertilization is external, agreeing with 
observations by Moran (1997), who rejected a process of 
internal fertilization reported years ago by Hewatt (1934). 

Embryonic development up to the formation of the 
trochophore took 9-10 hr. Moran (1997) reported 25 hr 
for this species. Kulikova & Omel’yanenko (2000) re- 
ported 16-17 hr for 7. rustica. From veliger larvae to the 
onset of the benthic phase, development time was similar 
to the report of Moran (1997), the larvae attaching be- 
tween days 6-8. Moran noted longitudinal striations on 
the shell on day 21, while our observations placed this 
feature at day 14. Another important difference is the ab- 
sence of pigmentation in the foot and head in our speci- 
mens, compared to Moran’s finding of pigmentation in 
juveniles at 2 months’ development. 

Such variations in T. funebralis may be a consequence 
of temperature conditions during the experiment: 18— 
20°C in our study and 13—15°C in Moran’s investigation. 
For 7. rustica, differences could be related to species 
characteristics, since early development in this species 
took place at temperatures similar to those used in our 
study. 

From day 14 onward, some events and features, such 
as transverse sutures in the teleoconch, number of papil- 
lae, shell-aperture shape, spire-raising, and time of adult 
characteristics, cannot be compared with Moran’s study 
because they were not described in his work. 

We found that larval development among the species 
that we studied is very similar until the veliger stage. To 
distinguish conspicuous differences, experiments need to 
be undertaken beyond that stage, preferably to the early 


Page 120 


juvenile stages, where teleoconch development begins to 
show different morphological characteristics. For exam- 
ple, in early juvenile T. funebralis, very fine longitudinal 
striations are formed on the anterior edge of the teleo- 
conch. These become longitudinal ribs in juveniles. In 
Megastraea undosa, early juveniles develop a crenulated 
ornamentation and brown spots at the edge of the teleo- 
conch (Guzman del Proo et al., 2003). 

The recognition of these differences among early ju- 
venile stages of gastropods living in rocky habitats, in 
association with abalone (Haliotis spp.), will provide im- 
portant information about intensity of reproductive activ- 
ity and settlement patterns shared by these species and 
the dynamics of interaction within the rocky communities 
of the central Pacific coast of Baja California. 

Understanding reproductive interactions and strategies 
that these species have developed for resource allocation 
may-help improve management of heavily exploited spe- 
cies, such as Haliotis spp. and M. undosa, as well as of 
other species associated with this benthic community that 
may come under future management by reason of their 
commercial value. 


Acknowledgments. The authors express their appreciation to 
CIBNOR (project grant AC5.1) and IPN (project grant CGEPI 
200494) for financial support of our bi-institutional study; Jorge 
Belmar and Jorge Carrillo helped procure broodstock; and Ale- 
jandra Mazariegos assisted in maintaining broodstock. Aquacul- 
tural Genetics Laboratory, CIBNOR supplied the microalgae 
used as food. Cooperative de Producci6n Pesquera Bahia Tor- 
tugas and their technicians, Alejandro Villa Bastida and Alberto 
Castro, provided support during fieldwork; Centro Regional de 
Investigaciones Pesqueras in La Paz provided their facilities in 
Bahia Tortugas. Illustrations were drawn by Alfonso Barbosa. 
The English text was reviewed by Ira Fogel at CIBNOR. 


LITERATURE CITED 


BELMAR-PEREZ, J., S. A. GUZMAN DEL PROO & I. MART{NEZ-Mo- 
RALES. 1991. Madurez gondadica y ciclo reproductor del car- 
acol panocha (Astraea undosa Wood, 1828; Gastropoda: 
Turbinidae) en Bahia Tortugas, B.C.S. Anales del Instituto 
de Ciencias del Mar y Limnologia. Universidad Nacional 
Aut6noma de México 18(2):169-187. 

BELMAR-PEREZ, J. & S. A. GUZMAN DEL PROO. 1992. Madurez 
sexual y ciclo gonadico en Haliotis fulgens y Astraea un- 
dosa. Taller México Australia sobre Reclutamiento de Ben- 
tonicos de Baja California. Secretaria de Pesca-Instituto Pol- 
itécnico Nacional. Pp. 121-130. 


The Veliger, Vol. 48, No. 2 


CARREON-PALAU, L. 2000. Microhabitat, distribuci6n y abundan- 
cia de juveniles de abulén, Haliotis fulgens y H. corrugata 
en Bahia Tortugas B.C.S., México. Masters Thesis. Escuela 
Nacional de Ciencias Bioldgicas, Instituto Politécnico Na- 
cional, Mexico, D.F 71 pp. 

CARREON-PALAU, S. A. GUZMAN DEL PROO, J. BELMAR-PEREZ, J. 
CARRILLO-LAGUNA & R. HERRERA-FRAGOSO. 2003. Micro- 
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fulgens and H. corrugata, in Bahia Tortugas, Baja California 
Sur, Mexico. Ciencias Marinas 29(3):1—17. 

GONZALEZ, M. L., M. C. PEREZ, D. A. Lopez, J. M. URIBE & C. 
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lin, 1791). The Veliger 42(3):275—277. 

GUZMAN DEL Proo, S. A., P. S. R. MILLE, G. R. GUADARRAMA, 
G. S. DE LA CAmpPaA, L. J. CARRILLO, C. A. PEREIRA, P. J. 
BELMAR, A. M. J. PARRA & G. A. LUQUE. 1991. La comu- 
nidad bent6nica de los bancos de abul6n (Haliotis spp. Mol- 
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GUZMAN DEL PROO, S. A., T. REYNOSO-GRANADOS, P. MONSALVO- 
SPENCER & E. SERVIERE-ZARAGOZA. 2003. Larval and early 
juvenile development of the wavy turbain snail Megastraea 
undosa (Word, 1828) (Gastropoda: Turbinidae). The Veliger 
46(4):320-324. 

Hewatt, W. G. 1934. Ecological studies on selected marine in- 
tertidal communities of Monterey Bay. Doctoral Thesis. 
Stanford University, Stanford, CA. 150 pp. 

Hotyoak, A. R. 1988. Spawning and larval development of the 
trochid gastropod Calliostoma ligatum (Gould, 1849). The 
Veliger 30(4):369-371. 

JENSEN, J. T. 1981. Distribution, activity, and food habits of ju- 
venile Tegula funebralis and Littorina scutulata (Gastro- 
poda: Prosobranchia) as they relate to resource partitioning. 
The Veliger 23(4):333-338. 

Kikucul, S. & N. UKi. 1974. Technical study on artificial spawn- 
ing of abalone, genus Haliotis Il. Effect of irradiated sea- 
water with ultraviolet rays on inducing to spawn. Bulletin 
of the Tonoku Regional Fisheries Research Laboratory 33: 
79-85. 

KULIKOVA, V. A. & OMEL’ YANENKO. 2000. Reproduction and lar- 
val development of the gastropod mollusk Tegula rustica in 
Peter the Great Bay, Sea of Japan. Russian Journal of Marine 
Biology 26(2):128—130. 

LEIGHTON, D. V. 2000. The Biology and Culture of the California 
Abalones. Dorrance Publishing Co.: Pittsburg. 216 pp. 
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black turban snail Tegula funebralis (Prosobranchia: Tro- 

chidae). Marine Biology 128:107—114. 

PONCE-DiAz, G. 2004. Efecto de la mortalidad por pesca y la 
variabilidad climatica en la pesqueria de abulo6n. Doctoral 
Thesis. Centro Interdisciplinario de Ciencias Marinas-Insti- 
tuto Politécnico Nacional, La Paz, B.C.S., Mexico. 118 pp. 


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