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HARVARD UNIVERSITY
e
Library of the
Museum of

Comparative Zoology

Gilbert Dennison Harris
(1864 - 1952)

Founder of the Bulletins of American Paleontology (1895)

eer a AT tn se eee
JLUME 104, NUMBER 342 APRIL 14, 1993

Late Wenlock and Ludlow (Silurian)
Plectograptinae (Retiolitid Graptolites),

Cape Phillips Formation, Arctic Canada

by

Alfred C. Lenz

Paleontological Research Institution
1259 Trumansburg Road
Ithaca, New York, 14850 U.S.A.

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JLUME 104, NUMBER 342 APRIL 14, 1993

Late Wenlock and Ludlow (Silurian)
Plectograptinae (Retiolitid Graptolites),

Cape Phillips Formation, Arctic Canada

by

Alfred C. Lenz

Paleontological Research Institution
1259 Trumansburg Road
Ithaca, New York, 14850 U.S.A.

Library of Congress Card Number: 93-083904

Printed in the United States of America
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CONTENTS

Page
SAN IRTET, 4 URS oP eee cota onde an Senet CORRE nn MEIETe La cee a a eR a eR ae ee fee Riis eee etre cite nested Sirsa 5
BYTE gS eee a Oe een NC PR ae Seer oar CA ears RL TPIT er TET 5
Bee TIOW ICU EEINIEMES ese arcyccava cher tee wieysayalersteroe oieictokteon a eaalanthein pcehsteie ie aie Tan See opesatcdela aia te ase eiales era thone Gravee ntars binaranic rete tededelon Tae 6
MENU COLISES CLIC St 2 evo ils soccer oa avon see sven COuSie Sule uci sors 27a cue ee speh os sci SiaesvtSie ES petcched Sees cov cna ols aioe oy BBY ov sire aN a en Cols eye No cits (Sue uml el ovetet ee stars 6
Berni CuesiOrmRecOvelyOMGraptolites frOmINOGUIES? sije ria erereis sete ey apecciesede elt belie = cle eye severeeronelev ene /olevs) ss spetavet slay stotsvelolstetorn\'s|eyahersel stone = y/
“OMT Wy 0 gion gen conc eee Eom atria Ore nene cae cnan ton Saacsn tae meas oS ecmaa rs sua run Ganemane se aoen oc. ate 8
Ps hoanyy anal) Bang leee eGR Titer io) Ne 3 a aewandacdagacoddnmosensecomntauda nudes ssocDuduGoDH ao couSnnoongnoconueesuseEs 10
Systematic Paleontology
METER OO CLUIC UL OM beey coy eretts vey ecac Cae) ke eecrer acres tu edocs te wver cloaks és epee eye ehe Lobe veuaharesaiaualls caval tate oVsvesetel eaiiatatefavaysya¥esefaneysteraal aps evel taper uae erereve rete 10
Monrphologyzand) Morphological: Terminology, arcs sca 22 oiee ele eee = © ee lescicte ele alesieie esieieieie atstetete eleichevate. ol icjetel ey el okey eke lete= ice sta) sets 12
Abbreviations ofRepositony Institutions: 5.2 /.r. ah sceccreiseacevereyerststece cfeistescie ens exe oye evausveparfiara/avats ya eva rcntia ystevayncal vate toe) ci evans ehautyerseehaysyens 13
BUS CEMTIACE CS fumee oer cere cose SVN SIAVSL SLA SUNSET NG eyo SLT ica NDOT fe OMe Shee ecor sich. PSVEVS CII feud eiekerehe cuore. iSie ase belay See eek ianahoe.cehaleie sil s te icienerenscolemenvevenoe 13
Reppendix— Collecting Mocalitiesianditheir Contained! Faunass) fee cree: ccte--setel ets waters avevcts eretever ay loeverctevey syelaVefclopeiave ieler Ine sla evelereisverete 24
) AIRC TS (OTS t) ae ae ce eae enone SR tee Dig RE Sr an en Ee Ee Ree Recaro ete ah EI ORES A NEE be ta Koo 26

GLEE. a ose Ree rene eye REL ETERS ere rR RRS nega gs AE Re tee PY ter ae dee RNG as co-op a rs ar pee eg Oi aS AY aN 50

LIST OF ILLUSTRATIONS

Text-figure

L Indexsmap) showing lOcalities: << sans ccia.s ersvsseczegew oo snoeg, ee ise acd Stone dS Se bem er npepehad Se SSIES che Se eS ee ee Oe
- Portion: of the Separation Point Mapsheet 58; showing the’Snowblind Creek area... 00... joanesane esse oe eee eee
: Wenlock:and' Ludlow: graptolite biozonations of the Arctic Islands) 2.22. .00..2 2.0.0 -0cc 2c cease nee eis/s)« asin ic stoic eee
Diagrammatic composite sketches of morphological components of plectograptines .. 2.2.0... cee eee eee

Fwn

LIST OF TABLES

Table
1. Matrix.of morphologic features’ofiplectograptines: ~<;- << 2 oa. < << cece ec cee sees wine. neve sseioe alee ole lees eicieielse ls iets epee eee

Page

Page

LATE WENLOCK AND LUDLOW (SILURIAN) PLECTOGRAPTINAE
(RETIOLITID GRAPTOLITES), CAPE PHILLIPS FORMATION, ARCTIC CANADA

by
A. C. LENZ

Department of Geology
University of Western Ontario
London, Ontario, N6A 5B7
CANADA

ABSTRACT

A rich fauna of beautifully preserved, isolated and uncompressed late Wenlock and early Ludlow retiolitids of the Subfamily
Plectograptinae were recovered through acid dissolution of limestone nodules in the Cape Phillips Formation, central Arctic
Islands. The fauna ranges in age from the late Wenlock Cyrtograptus lundgreni-Monograptus testis Zone to the mid-Ludlow
Saetograptus fritschi linearis Zone.

The fauna consists of seven genera/subgenera, Agastograptus, Gothograptus, Holoretiolites, Paraplectograptus, Plectograptus
(Plectograptus), Plectograptus (Sokolovograptus), and Spinograptus; and sixteen species: Agastograptus clathrospinosus (Eisenack),
Agastograptus quadratus, n. sp., Gothograptus nassa (Holm)', Gothograptus chainos, n. sp., Gothograptus eisenacki (Obut and
Sobolevskaya)*, Gothograptus marsupium, n. sp., Gothograptus? sp., Holoretiolites mancki (Minch), Paraplectograptus eiseli
(Manck)?, Paraplectograptus praemacilentus (Bouéek and Minch), Paraplectograptus sagenus, n. sp., Plectograptus (Plectograptus)
macilentus (Térnquist)*, Plectograptus (Sokolovograptus) textor Bouéek and Minch, Plectograptus (Sokolovograptus?) sp., Spi-
nograptus apoxys, n. sp., and Spinograptus nevadensis (Berry and Murphy). Spinograptus spinosus (Wood) and Balticograptus
are recognized in only flattened form, are rare and poorly preserved, and are not described.

Biostratigraphic ranges of the taxa, as known from the Arctic occurrences, are as follows: Plectograptus (Sokolovograptus) and
Paraplectograptus begin in the late Llandovery and range to the end of the Cyrtograptus lundgreni- Monograptus testis Zone;
Spinograptus nevadensis ranges through the Cyrtograptus perneri-Monograptus opimus and the Cyrtograptus lundgreni-Mono-
graptus testis zones; Gothograptus eisenacki, Gothograptus marsupium, and Gothograptus? sp. appear in, and are confined to,
the Cyrtograptus lundgreni-Monograptus testis Zone, while Gothograptus nassa and Gothograptus chainos are restricted to the
latest Wenlock “Pristiograptus” ludensis Zone, Agastograptus clathrospinosus begins slightly below the Cyrtograptus lundgreni—
Monograptus testis Zone and extends into the Lobograptus progenitor Zone; Spinograptus spinosus® ranges from the **Pristio-
graptus” ludensis Zone through the early Ludlow Lobograptus progenitor Zone; Agastograptus quadratus, n. sp. is confined to
the Lobograptus progenitor Zone; and Holoretiolities mancki and Plectograptus (Plectograptus) macilentus range through the
Lobograptus progenitor and Saetograptus fritschi linearis zones.

Morphological characteristics of the long-ranging taxa Paraplectograptus and Plectograptus (Sokolovograptus) suggest they are
the progenitors of two late Wenlock and early Ludlow subgroups: the first being those in which the virgula is attached throughout,
or to some distal part of the rhabdosome; the second being those in which the virgula is free distally. Representatives of both

groups ranged through to the early or mid-Ludlow, prior to the final extinction of the plectograptines.

INTRODUCTION

Retiolitids, including the plectograptines, by virtue
of the reduction of their skeletal elements to a series
of narrow lists, are among the most beautiful groups
of graptolites. Because of this much-reduced skeleton,
and the small size and fragility of many of the taxa,
they are relatively rarely preserved, even as flattened
films on shale. They have, therefore, been among the
least understood groups of graptolites. The recovery of
isolated, uncompressed specimens, particularly from
‘the Arctic, has recently contributed much to the un-
derstanding of the overall morphology, growth, and

‘Uncommon and found only in flattened form.

> Abundant.

* Rare.

* Rare.

’ Found only in flattened form and not described.

development and, to some extent, the evolutionary
development of the retiolitids (Lenz and Melchin,
1987a, 1987b).

The Cape Phillips Formation of the Canadian Arctic
Islands has long been recognized for its superb pres-
ervation of graptolites, including retiolitids, in lime-
stone nodules (Thorsteinsson, 1958). My recent work
on these upper Wenlock and Ludlow shales and their
enclosed nodules led to the recovery of sixteen species
of plectograptine retiolitids, all uncompressed. The
collecting localities from which these specimens were
recovered are shown in Text-figures | and 2. The late
Wenlock and Ludlow forms are specifically focussed
on because plectograptines in that part of the strati-
graphic column are much less known or understood
than those of the late Llandovery. During the late Wen-
lock and Ludlow, an unprecedented evolutionary di-
versification occurred among the plectograptines, prior

oS
S6 Grinnell
“Peninsula

36 Baillie

Hamilton/ (

Telawdiey 5

Cornwallis

/

“\) Island |

Text-figure 1.—Index map showing collecting localities. The inset
shows details of sections from which samples were collected in the
Snowblind Creek area (loc. 1) during the 1990 field season.

to their extinction in mid-Ludlow time. This diversi-
fication of the plectograptines during the latest Wen-
lock and earliest Ludlow coincided with a distinct drop
in monograptid diversity.

ACKNOWLEDGEMENTS

This study was greatly facilitated by the field assis-
tance and support through the years of a number of
individuals, among them B. Chatterton, K. Dewing, J.
Hill, J. Jin, A. McCracken, D. Perry, S. Senior, and J.
Shaw. Special thanks go to M. Melchin who acted as
assistant on a number of occasions and who subse-
quently independently collected, and generously do-
nated, graptolite-bearing nodules. Most of the studies

BULLETIN 342

of plectograptine graptolites were carried out while I |
was on Sabbatical leave at Trinity College, Dublin. The
support of the Department of Geology at that insti-_
tution, and particularly of C. H. Holland, is particularly
acknowledged. Appreciation is also expressed to the |
faculty and technical staff of that Department, as well
as to D. John and C. Reid of the Trinity College Elec-
tron Microscopy Unit, for the many kindnesses and
assistances while at Trinity. A. Pratt operated the Scan- |
ning Electron Microscope at Surface Science Western,
University of Western Ontario, and his fine services
were much appreciated. H. Jaeger, Berlin, generously
shared some of his knowledge and information on plec- |
tograptines in his collections, and provided a photo-—
graph and line drawings of some; T. Koren, St. Pe-—
tersburg, supplied range charts of late Wenlock
graptolites, including plectograptines, in her collec- |
tions; and A. Kozlowska-Dawidziuk, Warsaw, provid- |
ed an SEM photograph of a long specimen of Gotho-
graptus eisenacki Obut and Sobolevskaya, 1965. N. H. |
Kirk and D. E. B. Bates readily shared their under-
standing of the retiolitids during my visit to Aberys-
twyth in 1990. Finally, the assistance of V. Jaanusson
in obtaining a loan of retiolitid specimens from the
Riksmuseum, Stockholm, is acknowledged. The
manuscript was reviewed by C. Carter and C. E. Mitch-
ell, both of whom offered valuable comments and sug-
gestions. In particular, I am indebted to Mitchell for
pointing out some inconsistencies in the interpretation
of thecal apertural structures. To both I give my thanks.
Financial support has been through a Natural Sci-
ences and Engineering Research Council (Canada) op-
erating grant, and logistical support in Arctic Canada
has been through the Polar Continental Shelf Project.

PREVIOUS STUDIES

Silurian retiolitids were noted among the graptolite
faunas recovered from limestone nodules in the Cape
Phillips Formation of Cornwallis Island by Thorsteins-
son (1958): none, however, was illustrated. A small
fauna of flattened Wenlock and Ludlow plectograptine
graptolites from the same general region was described
and illustrated in Lenz (1978), and a single Ludlow
species was illustrated in Jackson, Lenz, and Pedder
(1978). Subsequently, all genera of isolated and un-
compressed Silurian retiolitids recognized at that time
were discussed and illustrated in Lenz and Melchin
(1987a), and to a minor extent in Lenz and Melchin
(1987b). Finally, a few taxa of Arctic Silurian retioli-
tids, most commonly of the Retiolites geinitzianus type,
have been illustrated in papers devoted to growth and
development, or the nature of the skeletal elements of
the retiolitids (Kirk, 1973; Bates and Kirk, 1978, 1984,
1986; Crowther, 1981). Although it does not illustrate
Arctic retiolitids, the paper of Berry and Murphy (1975)

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ iT

on Silurian and Devonian graptolites of Nevada is also
relevant.

Elsewhere in the world, studies of uncompressed and
isolated Wenlock and Ludlow retiolitids include: iso-
lated specimens of Stomatograptus Tullberg, 1883 and
Gothograptus nassa (Holm, 1890) by Holm (1890), and
of Gothograptus nassa by Wiman (1896), both from
Gotland; the pioneering studies of Eisenack (1935,
1951) on the Silurian, particularly Ludlow, glacial er-
ratics of northern Germany, which yield a number of
beautifully preserved taxa; Obut and Sobolevskaya’s
(1965) studies of isolated specimens of Gothograptus
eisenacki Obut and Sobolevskaya, 1965; Obut and Zas-
lavskaya’s (1976) study of isolated material of Refiol-
ites Barrande, 1850, Pseudoretiolites Boucek and
Minch, 1944, and Sokolovograptus Obut and Zaslav-
skaya, 1976 from boreholes in Siberia; and finally, the
important study of Obut and Zaslavskaya (1983, and
its English translation [1986]), which discussed Silu-
rian retiolitid classification and recognized as new the
genus Agastograptus Obut and Zaslavskaya, 1983.

TECHNIQUES FOR RECOVERY OF
GRAPTOLITES FROM NODULES

Because they commonly have a thin siliceous coat-
ing, nodules are broken open to aid in the acid-diges-
tion process. For best recovery of graptolites, partic-
ularly the delicate types, acid dissolution must be very
slow, using only 1—2% HCl®, with small amounts of
acid being added daily or more often. Periodically, the
surface of the acid is skimmed gently with a 60-100
mesh stainless steel sieve to collect graptolites floating
on the surface. Most graptolites float because of the
CO, bubbles inside or clinging to the rhabdosomes.
The graptolites in the sieve are then rinsed very gently
in hot water to wash away clays or other fine particles
as well as some of the organic matter derived from the
nodules’. The residue is then gently washed in absolute
alcohol to remove all traces of the oily organics, fol-
lowing which it is washed into small, tightly-closed jars
and stored in absolute alcohol. The graptolites may be
stored this way indefinitely. A very fine hair brush is
subsequently used to pick and transfer specimens.

When the dissolution of the nodule is complete, and
the surface has been skimmed one more time, the en-
tire contents of the container are poured slowly and
gently through a 60-100 mesh sieve, until the bottom
sediments are just beginning to accumulate on the sieve.
After this, the washing procedure outlined above is
repeated.

® Acetic or other organic acids are even more gentle, but require
much more time.

’ Nodules from the Cape Phillips Formation contain a large amount
of “oily” organics.

Text-figure 2.—A portion of the Separation Point Mapsheet 58
G/2 (scale 1:50,000), showing the Snowblind Creek area (loc. 1) in
relation to local topography. Contour interval = 10 m. Letters des-
ignate sections from which samples were collected during the 1990
field season.

Most graptolites from any one nodule will float to
the surface and will be recovered by skimming. Some,
and often many, specimens will, however, sink, par-
ticularly those containing pyrite. It is important, there-
fore, to examine the residues on the bottom of the
container. In rare cases, nearly monospecific assem-
blages have been recovered almost entirely from the
bottom residue.

Depending on the size of the nodule or amount of

8 BULLETIN 342

nodular material being digested, the processes de-
scribed above may be repeated several times before
dissolution is complete. Some clay-rich nodules will
readily dissolve only to the point where the clays be-
come so thick as to totally impede dissolution; a further
problem arises in this case because graptolites may
remain lodged in the clays. If the clay layers are thin,
periodic scrubbing of the nodules will permit addi-
tional dissolution and further recovery of graptolites.
At times, however, the clay content is too great, and
the nodule must be discarded.

BIOSTRATIGRAPHY

Wenlock, Ludlow, and Pridoli graptolite sequences
of the Arctic Islands have been the focus of study for
several years. As a result, recent zonal schemes based
on flattened graptolite material for the Wenlock (Lenz
and Melchin, 1990, 1991) and for the Ludlow (Lenz,
1990) are readily usable. The zones discussed below
are a composite of those defined in these studies: the
species names used to define the zones are those of
Lenz and Melchin (1991).

WENLOCK

Cyrtograptus centrifugus—Cyrtograptus insectus Zone

The zone is recognized by the appearance of either
of the two index species. Monograptus cf. M. flexilis
(Elles, 1900) appears in the zone, but extends beyond,
as does Monograptus flemingi (Salter, 1852).

Monograptus instrenuus—Cyrtograptus kolobus Zone

Most commonly, the zone is recognized by the first
appearance of Monograptus instrenuus Lenz and Mel-
chin, 1991, and this is reinforced by the occurrences
of Cyrtograptus kolobus Lenz and Melchin, 1991, Cyr-
tograptus preclarus Lenz, 1988b [rare], as well as pos-
sibly by Pristiograptus meneghini (Gortani, 1922).

Cyrtograptus perneri-Monograptus opimus Zone

The appearance of either of the index species indi-
cates the base of the zone. Cyrtograptus pseudomancki
Lenz and Melchin, 1991, is restricted to the zone, and
Cyrtograptus multiramis Tornquist, 1910 attains its
acme in this zone, but ranges into the overlying zone.

Cyrtograptus lundgreni—Monograptus testis Zone

This is the earliest zone of relevance to this study.
The index species are very characteristic of the zone,
but important other elements include Cyrtograptus ra-
dians Tornquist, 1887 and Cyrtograptus hamatus (Bai-
ly, 1861). Plectograptines include Paraplectograptus
Pribyl, 1948 (three species), Spinograptus spp., Plec-
tograptus (Sokolovograptus) spp., Gothograptus eisen-
acki Obut and Sobolevskaya, 1965, Gothograptus mar-

supium, n. sp., and Agastograptus clathrospinosus
(Eisenack, 1951).

*Pristiograptus” ludensis Zone

The composition of the zone is markedly different
from that of the underlying zones. ‘‘Pristiograptus”
ludensis (Murchison [sensu Wood, 1900]), “‘Pristio-
graptus” sherrardae (Sherwin, 1975), and *“‘Pristio-
graptus” praedeubeli (Jaeger, 1990), are typical. Goth-
ograptus nassa, Gothograptus chainos, n. sp., and
Agastograptus clathrospinosus, among the plectograp-
tines, are also found in the zone, the first two being
restricted to the zone.

LUDLOW

Lobograptus progenitor Zone

Characteristic of the zone are Lobograptus progen-
itor Urbanek, 1966, Pseudomonoclimacis dalejensis
(Bouéek, 1936), and the first appearance of Bohemo-
graptus bohemicus bohemicus (Barrande, 1850). Plec-
tograptines include Spinograptus spinosus (Wood,
1900), Holoretiolites Eisenack, 1951, Agastograptus
spp., and Balticograptus Bouéek and Minch, 1952.
Spinograptus Bouéek and Minch, 1952 and Baltico-
graptus are found in flattened form only, and are not
well-preserved.

Saetograptus fritschi linearis Zone

The first appearance of the index species in associ-
ation with Monograptus ceratus Lenz, 1988a is diag-
nostic. The fauna is of low diversity, although Pseu-
domonoclimacis dalejensis is common in the interval,
and Bohemograptus bohemicus bohemicus continues
through the zone. Holoretiolites mancki (Minch, 1931)
and Plectograptus (Plectograptus) macilentus (T6rn-
quist, 1887) are the only plectograptines in the zone.

Bohemograptus bohemicus tenuis Zone

The first appearance in abundance of the index spe-
cies is the primary indicator of the zone. The zonal
equivalent elsewhere contains several other species of
Bohemograptus Pribyl, 1967. The zone appears to be
devoid of plectograptines.

ZONAL CORRELATION

The suggested correlation of the Arctic Islands Wen-
lock and Ludlow strata with a composite of zones from
Great Britain (Rickards, 1976) and Czechoslovakia
(Pribyl, 1983; Jaeger, 1986) is shown on Text-figure 3.
For more detailed discussions of the correlations, see
Lenz (1990) and Lenz and Melchin (1991). Biostrati-
graphic ranges of the plectograptine species described
herein are shown in same figure. Zonal assignments
and zonal ranges shown for the plectograptine species

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 9

GRAPTOLITE BIOZONES BIOSTRATIGRAPHIC RANGES OF

ARCTIC BRITISH ISLES and
ARCTIC ISLANDS PLECTOGRAPTINAE
ISLANDS CZECHOSLOVAKIA cae

fragmentalis

fecundus

bohemicus tenuis| | |
insignitus

inexspectatus

"bohemicus beds"

fritschi linearis | 102845

fritschi linearis

LUDLOW

scanicus

progenitor progenitor

Gothograptus eisenacki

nilssoni

ludensis

Plectograptus (Sokolovograptus) textor
Paraplectograptus praemacileatus
Spinograptus nevadensis

Paraplectograptus sagenus
Gothograptus marsupium

Paraplectograptus eiseli
Spinograptus apoxys

nassa

Jundgreni-testis Jundgreni

ellesi

perneri-opimus
linnarssoni-flexilis

rigidus
instrenuus-

kolobus

WENLOCK

riccartonensis

centrifugus- murchisoni

insectus

Holoretiolites (Holoretiolites) mancki
Plectograptus (Plectograptus) macilentus

Agastograptus clathrospinosus

Gothograptus nassa*
Gothograptus chainos
Spinograptus spinosus*
Agastograptus quadratus

centrifugus-insectus

Text-figure 3.—Wenlock and Ludlow graptolite biozonations of the Arctic Islands (after Lenz, 1990, and Lenz and Melchin, 1991), in
comparison with a composite of the biozones of the British Isles and Czechoslovakia (after Rickards, 1976; Pribyl, 1983; and Jaeger, 1986),
and the biostratigraphic ranges of plectograptine retiolitids recognized in the Arctic Islands. Species marked with an asterisk are found only
in flattened form on bedding planes in shale. Excluded from the chart are taxa recognized only at the generic level.

10 BULLETIN 342

are based on the position of graptolite-bearing nodules
relative to the adjacent, subjacent, and/or superjacent
graptolites flattened on shale surfaces.

PHYLOGENY AND PHYLOGENETIC
CLASSIFICATION

It has long been believed that Ordovician retiolitids
are unrelated, phyletically, to Silurian forms (see Rick-
ards, Hutt, and Berry, 1977; Rigby, 1986; Mitchell,
1987, for up-to-date references), and it is only the Si-
lurian taxa in the Family Retiolitidae that are relevant
in this study. Furthermore, Silurian retiolitids have
been subdivided, largely for convenience, into early
Silurian Retiolitinae and later Silurian Plectograptinae
(Bouéek and Miinch, 1952; Bulman, 1970). With the
advent of electron microscopy, and the recognition of
a distinctly different micro-ornament on the skeletal
elements in the two subfamilies (Lenz and Melchin,
1987a), there is now a sounder basis for formal rec-
ognition of the two subfamilies. Thus, all taxa with a
pustulose micro-ornament are assigned to the Subfam-
ily Plectograptinae, while those earlier forms with a
parallel linear pattern are members of the Subfamly
Retiolitinae.

Relatively little has been written of the evolution of
the Silurian retiolitids. Bou¢ek and Minch (1952), for
example, say nothing of the ultimate origin of the two
subfamilies, except to tentatively suggest that they are
derived independently. Bulman (1970) is even more
vague, and only suggests a derivation of the family
members from one or more lines of diplograptids.
Rickards, Hutt, and Berry (1977) point to the similarity
between petalograptids and Silurian retiolitids and sug-
gest a phylogenetic relationship. They further suggest
that taxa such as Plectograptus? bouceki Rickards, 1967
[= Plectograptus (Sokolovograptus) bouceki Rickards,
1967] might be ancestral to plectograptines. Bates and
Kirk (1984) point out the strong similarity between the
ancorae of petalograptids and those of the retiolitids,
and suggest that the retiolitid clathrium is derived from
further development of the ancoral structures. They,
however, make no comment on the derivation of the
two subfamilies. Mitchell (1987) and Melchin and
Mitchell (1991) consider that the “‘pattern I’ devel-
opment is characteristic of the retiolitids, and propose
that the early skeletal framework of retiolitids and the
ancoral processes of petalograptids and ‘“‘Orthograp-
tus” obuti Rickards and Koren, 1974, are homologous
structures. Some workers, then, accept the concept of
the derivation of Silurian retiolitids from one or more
petalograptid ancestors. The problem, however, is
compounded by the fact that the post-coronal orifices
(discussed below) are ancora-related structures, and
not true thecae, which are sicula-derived structures.

Turning to the Plectograptinae (i.e., essentially late

Llandovery to Ludlow retiolitids), the group, as already
noted, is united by the common occurrence of pustu-
lose micro-ornament, a feature therefore considered to
be primitive. The origin of the group, however, is in
doubt. Rickards, Hutt, and Berry (1977), as well as
Boucek and Minch (1952), considered the group most
likely to be derived separately from the Retiolininae.
I do not accept that view: the reasons are twofold. First,
a continuous record of retiolitines and plectograptines
exists in Arctic Canada; and second, there appear to
be at least two primitive features linking the plecto-
graptines directly with Retiolites Barrande, 1850 or
closely related retiolitines. A prosicula is commonly
present in Retiolites (Lenz and Melchin, 1987a); is ap-
parently present, though rare, in the long-ranging Plec-
tograptus (Sokolovograptus) Obut and Zaslavskaya,
1976; and has been observed for the first time herein
in Paraplectograptus Pribyl, 1948. Equally important-
ly, both Retiolites and all plectograptines have a sim-
ple, four-pronged ancora in which two opposed
branches usually join with the lists forming the base
of the post-coronal orifices, the other pair of prongs
being involved in development of the corona. Such
primary (plesiomorphic) astogenetic structures surely
provide an adequate link between the two subfamilies.
On the other hand, the appearance of the pustulose
micro-ornament is apparently sudden and without
transition.

Beyond that level, the picture is less clear. However,
two distinct morphotypes are present in the late Llan-
dovery: the Paraplectograptus type, in which the vir-
gula is incorporated into the skeletal wall or into the
distal part of the rhabdosome in younger forms; and
the Plectograptus (Sokolovograptus) type in which the
virgula is free throughout (see Text-fig. 4). These mor-
photypes consitute good ancestral models for two sub-
groups of later Silurian plectograptines (the Plecto-
graptus Subgroup and the Paraplectograptus Subgroup
of this study). Geochronologically, the progenitors of
the two subgroups appear in the late Llandovery, but
do not undergo major diversification until the late
Wenlock (see Table 1, p. 24).

If it is accepted that there are two distinct subgroups,
the ramifications are important; namely, that at or about
the time of final extinction of the plectograptines, spe-
cies of both subgroups were present, making the ex-
tinction even more profound.

SYSTEMATIC PALEONTOLOGY

INTRODUCTION

Graptolites, being an extinct group, are difficult to
compare with living, colonial organisms, and conse-
quently there are no analogs to indicate the degree of
inter- and intra-specific variation common among spe-

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 11

horizontal list

r sigmoidal structure

apertural
list

<— pleural list

aboral list

aperture

a

DP === =
\\
<< upper apertural
i

pleural lists
interpleural list

inner connecting list
lower apertural list

aperture

Text-figure 4.— Diagrammatic composite sketch of morphological components in (a) Paraplectograptus-type plectograptines, and (b) Plec-
tograptus-type plectograptines. Most terms are those standardardized in Bulman (1938, 1970); new morphological terms are sigmoidal structure,

interpleural list, and inner connecting list.

cies. Furthermore, the vast majority of graptolites are
preserved as flattened, two-dimensional objects on shale
surfaces, a fact that sometimes makes taxonomic stud-
ies difficult. In rare instances, however, such as in the
present study, graptolites are enclosed as uncom-
pressed, three-dimensional objects in limestone nod-
ules, and may be released by acid dissolution.

The recovery of these freed, uncompressed speci-
mens of Silurian retiolitids represents a unique op-
portunity to better understand the astogeny, classifi-
cation, morphological variation, and evolution of the
group. Most genera and some species of retiolitids have
been illustrated in isolated, uncompressed form by ear-
lier workers, so that the morphologic criteria of most
genera are well understood. Paradoxically, the superb
preservation of such specimens creates a problem in
the recognition of, and comparison with, species and
even genera that are preserved in the more common,
flattened mode. As examples, the distinctions between
Paraplectograptus Pribyl, 1948 and Plectograptus
Moberg and Tornquist, 1909 (sensu stricto); Spino-
graptus Boucek and Munch, 1952 and Agastograptus
Obut and Zaslavskaya, 1983; and Holoretiolites Eisen-
ack, 1951 and Balticograptus Boucek and Minch, 1952
are difficult, and at times impossible, to make in flat-
tened forms.

In this study, the Plectograptinae have been divided
into two informal subgroups: those with the virgula
attached throughout or to the distal part of the rhab-
dosome, and those in which the virgula is totally free
beyond its ancoral attachment. As such, the formal
recognition of two subgroups at the Tribe level, or the

elevation of the Subfamily Plectograptinae to the Fam-
ily level might seem justified. However, until the large
group of Silurian retiolitids, including the plectograp-
tines, is studied in toto, the informal division seems
justified.

Morphological criteria used in the recognition of
genera are primarily qualitative ones; they include de-
gree of attachment, if any, of the virgula; profile of the
rhabdosome, and whether it remains parallel-sided or
narrows distally; the presence or absence of an appen-
dix; gross construction of the rhabdosome, particularly
the nature of the primary clathria; shape and profile
of the thecal walls; nature of the thecal aperture; and
the presence or absence of thecal spines or spinoreti-
cull.

The routine recovery of large numbers of immature
to mature specimens from any one horizon or nodule
permits the recognition of all growth stages, and thus
eliminates most of the problems in misidentification
of early growth stages. Furthermore, these growth stages
record the progressive increase in density and the change
in mesh size and shape of the secondary skeleton, the
reticulum. Both mesh size and shape can vary consid-
erably from species to species. Intraspecific variation
is high, even allowing for changes during maturation
of the rhabdosome, and admittedly there is a degree
of subjectivity. In this study, all specimens recovered
from a single nodule or from a series of nodules from
the same stratum, which share most characters, are
considered to represent the same species. The existence
of large numbers of specimens permits ready compar-
ison of material from different sections and stratigraph-

ic levels. In most cases, therefore, the differences be-
tween species recognized in this study are fairly clearcut
and unequivocal. The exception to this is a group of
species of Paraplectograptus: P. eiseli Manck, 1917, P.
praemacilentus (Bouéek and Miinch, 1952), an unde-
scribed species from older strata illustrated in Lenz
and Melchin (1987a), and P. sagenus, n. sp., all of
which show degrees of overlap. The differences among
these species are outlined in the discussion of P. prae-
macilentus.

Measurements of rhabdosomal features such as
length, width, and thecal spacing were made directly
from SEM photographs. Size comparators are defined
as follows: small = 1-3 mm; medium/moderate = 3—
7 mm; and large = >7 mm.

Synonymies used herein are not exhaustive; instead
they comprise the original author and a varying num-
ber of subsequent authors, all of which are considered
to be of taxonomic importance.

MORPHOLOGY AND MORPHOLOGICAL TERMINOLOGY

The retiolitid rhabdosome meshwork requires some
terminology beyond that normally used in the Treatise
(Bulman, 1970) for fully sclerotized forms such as
monograptids and diplograptids. Skeletal-element ter-
minology as used specifically for retiolitids by Bulman
(1938) and Rickards (1967) is adapted herein, and new-
ly named skeletal elements are shown on Text-figure
4. Because of the strikingly different development in
those taxa with a virgula attached throughout the length
of the rhabdosome (e.g., Paraplectograptus Pribyl,
1948), in comparison with those in which the virgula
is free throughout (e.g., Plectograptus Moberg and
Tornquist, 1909), or attached only at the distalmost
end of the rhabdosome (e.g., Gothograptus Frech, 1897),
a uniform terminology applicable to all retiolitids/plec-
tograptines is not possible.

In this study, in which some new species and several
taxa not previously or adequately known in uncom-
pressed form are described, several new morphological
terms are employed. The most commonly occurring,
newly named structures are thin, vertically oriented
lists connecting the lower apertural list of one theca to
the upper apertural list of the preceding one, and termed
herein interpleural lists (see Text-fig. 4). A second new
structure consists of a thin, internal, threadlike, in-
wardly curved list joining the upper apertural list of
one theca to that of the preceding or succeeding theca.
This is given the name inner connecting list (Pl. 17,
fig. 5; Pl. 18, fig. 6). Finally, a structure seen thus far
in only a single species, Spinograptus apoxys, N. sp., iS
a solidly sclerotized, sigmoidally curved, bladelike
structure connected to the lower apertural list of one
theca, and curving inward to connect with the inner

iD BULLETIN 342

connecting list of the underlying theca. This is termed
the sigmoidal structure (Pl. 18, fig. 5).

Traditionally, morphological terms applied to re-
tiolitids have been those used in more “‘conventional”’
graptolites such as the diplograptids. The reason for
this is easy to comprehend: large retiolitids such as
Retiolites Barrande, 1850 (s. 1.) and Stomatograptus
Tullberg, 1883, with their heavy, dense, meshwork re-
ticulum, and the rare “sheeting-over” of the entire
meshwork by a thin periderm, plus the presence of
ephemeral, fully or partly sclerotized thecal ‘‘floors”
(see Lenz and Melchin, 1987b), make it an easy step
to apply such terms as theca, thecal wall, thecal floor,
by extrapolation from the fully sclerotized diplograp-
tids. The continuation of this extrapolation from
heavily reticulated to lightly or not-at-all reticulated
retiolitids (e.g., Holoretiolites Eisenack, 1951) appears
logical.

A feature common to all plectograptines is their early
developmental stage (see p. 13). Typically, the two
short, opposing branches of the ancora each divide into
a pair of considerably longer and distally curving
branches, each pair diverging at an angle of about 60°
(Pl. 1, fig. 2; Pl. 5, fig. 10; Pl. 13, fig. 8). One opposing
pair of ancoral branches whose alignment is parallel
to and intimately connected with the development of
the subsequent thecal apertures, attaches directly to
the lists forming the “‘base”’ of left and right openings
(the post-coronal orifices of this study). These openings
define the top of the corona (see openings above strong-
ly curved coronal lists in Pl. 5, fig. 10). The second
opposing pair of ancoral branches, which are oriented
at an angle of about 60° to the plane of the rhabdosomal
axis, generally undergo further splitting and are mainly
involved in the further development of the corona (see
stereopairs on Pl. 14, figs. 5, 6).

The left and right openings, herein termed post-co-
ronal orifices, are superficially similar to thecal aper-
tures (see opening above strongly curved list in lower
right corner of Pl. 3, figs. 5, 7; openings above low-
ermost left and right lists in PI. 4, fig. 7; Pl. 5, fig. 10;
Pl. 9, figs. 8, 9). It is clear, however, from the exami-
nation of plectograptines such as several species of
Gothograptus, and by extrapolation from older retiol-
itines such as Pseudoretiolites Boucek and Minch, 1944
and Pseudoplegmatograptus Pribyl, 1948, which pre-
serve the prosicula and which have elaborately devel-
oped internal structures, that the first true thecae (7.e.,
thecae 1' and 1’) are the first openings distal of the
post-coronal orifices. In Gothograptus eisenacki Obut
and Sobolevskaya, 1965, for example, the floor of theca
1? clearly extends below and inside of the post-coronal
orifice®.

5 | thank Bates and Kirk for pointing this out.

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 13

It appears, therefore, that the post-coronal orifices
are features of the ancora, whereas thecae 1! and 1?
derive directly from the region where the sicula was,
as is typical in all diplograptids; /.e., they are homo-
logues.

The fully or partially sclerotized prosicula is a struc-
ture that gradually disappears in the evolution of the
Retiolitidae. Earlier taxa such as Pseudoretiolites and
Pseudoplegmatograptus consistently retain the prosi-
cula, as does the later Stomatograptus. Retiolites rel-
atively often retains a prosicula, prosicular threads, or
a prosicular “ring” (Lenz and Melchin, 1987a). The
plectograptines, on the other hand, seldom show any
trace of a prosicula, although Obut and Zaslavskaya
(1976) illustrated immature specimens of Plectograp-
tus (Sokolovograptus) parens (Obut and Zaslavskaya,
1976) that retain fragments or threads of a prosicula,
as do rare specimens of Paraplectograptus illustrated
herein (PI. 13, figs. 5-10). The presence of sicular rem-
nants in other plectograptines is more problematic.
Bates and Kirk (written commun., 1990), however, are
confident that they can recognize vestiges of the pros-
icula and the prosicular ring, and are therefore able to
distinguish between the sicula-derived virgella and the
post-sicular virgula. This helps in the understanding
of the early growth stages, and recognition of thecae
1' and 1*. However, in the absence of any vestige of
the sicula, the term ’virgula’ is consistently used for
the entire rodlike structure in the following taxonomic
section.

Throughout, conventional terms such as_ theca,
clathrium, reticulum, are used, even though it is rec-
ognized, as implied above, that some of the structures
may not be homologous. While revisions of morpho-
logical terms as applied to Silurian retiolitids are prob-
ably necessary, this should only be done in light of a
thorough study of all Silurian retiolitids, rather than
from the viewpoint of only the plectograptines.

There has been much discussion of life orientations
of graptolites (Kirk, 1990 and numerous citations
therein; Rigby and Rickards, 1990). In this study, the
traditional ‘“‘ancora-down”’ position is used, and terms
such as up, down, proximal, and distal are employed
in the traditional sense [/.e., Treatise (Bulman, 1970)].

ABBREVIATIONS OF REPOSITORY INSTITUTIONS

Described specimens, with one exception, are housed
in the type collection of the Geological Survey of Can-
ada, Ottawa, and are assigned Survey (GSC) numbers.
A single specimen of Gothograptus nassa (Holm, 1890)
on loan from the Riksmuseum, Stockholm, Sweden,
carries the acronym RM. The other repository noted
is University of California, Riverside, designated by
the acronym UCR.

SYSTEMATICS

Order GRAPTOLOIDEA Lapworth in
Hopkinson and Lapworth, 1875

Family RETIOLITIDAE Lapworth, 1873

Subfamily PLECTOGRAPTINAE
Boucek and Miinch, 1952

Diagnosis®.—Clathria well-developed, sometimes
with reticula, lacinia absent; development with ancora
stage; one opposed pair of ancoral branches joins lists
of post-coronal orifices, the other pair oriented at angle
to plane of rhabdosome and involved in development
of corona; proximal end of rhabdosome may be some-
what inflated (corona), may narrow distally, and in
some genera terminates in slender tubular appendix.
Virgula free or incorporated into ventral wall. Lists
pustulose on outside surfaces. Seams of the clathria
and reticula face in and out, respectively.

Plectograptus Subgroup’?

Genus PLECTOGRAPTUS
Moberg and Tornquist, 1909

Type species. — Retiolites macilentus Tornquist, 1887.
Early Ludlow colonus shales, Germany.

Remarks.—This genus is characterized by posses-
sion of a rhabdosome that is rectangular in cross-sec-
tion, generally parallel-sided, although forms that in-
crease or decrease in width distally are known, and by
a clathrium of subhexagonal meshes, with or without
some minor reticulum, and a central, free virgula.

Two more or less distinct morphologic groups exist;
one group, characterized by the genotype, typically lacks
or has only minor reticulum, and the skeletal frame-
work is well-ordered. This group constitutes Plecto-
graptus (Plectograptus), the second group possesses a
more disorderly skeleton and variable amounts of re-
ticulum; following the practice of Lenz and Melchin
(1987a), these forms are assigned to Plectograptus (So-
kolovograptus)!''.

Subgenus PLECTOGRAPTUS
Moberg and Tornquist, 1909

Plectograptus (Plectograptus) macilentus
(Tornquist, 1887)
Plate 1, figures 6-8

Retiolites macilentus Térnquist, 1887, p. 491, fig. 3.

° Modified after Lenz and Melchin (1987a).

'0 Includes Plectograptus (Plectograptus) Moberg and ToOrnquist,
1909, Plectograptus (Sokolovograptus) Obut and Zaslavskaya, 1976,
and possibly Agastograptus Obut and Zaslavskaya, 1983.

'! This is in contrast to Obut and Zaslavskaya (1976, 1986), who
defined Sokolovograptus as a separate genus.

14 BULLETIN 342

Plectograptus macilentus (Térnquist). Moberg and Térnquist, 1909,
p. 13, pl. 1, figs. 1-12; BouGek and Minch, 1952, p. 120, pl. 1,
figs. 1-4; text-figs. le, 6a, 7a-f; Jackson, Lenz, and Pedder, 1978,
pl. 2, figs. 10-12.

Retiolites (Plectograptus) tetracanthus Eisenack, 1951, p. 140, pl. 23,
figs. 6-8; pl. 24, fig. 8; pl. 25, fig. 9; text-figs. 4, 5.

Material.—A single, fragmentary isolated specimen
from locality 1, section B; one from locality 1, section
SBC 4, 7 m; six fragments from a single nodule at
locality 3. Illustrated specimens consist of GSC 10398 1-
103983.

Occurrence.— Early Ludlow, Lobograptus progenitor
and Saetograptus fritschi linearis zones.

Description.—Rhabdosome a simple, orderly mesh-
work of clathria and parietal lists, on ventral and dorsal
sides joined to a zigzag median list. Thecal profile cli-
macograptid, defined by equally strongly looped lower
and upper apertural lists joined by single central in-
terpleural list. Thecal margins parallel, or inclined at
angle to rhabdosomal axis. Rhabdosomal width (based
on flattened specimens) ranges from 1.6-1.9 mm and
thecal spacing is 5—5.5 in 5 mm. Ancora and corona
simple, consisting of four long, curved lists; corona
lacks rim, and a simple square opening between the
ancora and the horizontal list links earliest-formed pa-
rietal lists. Two proximally directed spines emerge from
ancora (PI. 1, figs. 6, 8).

Remarks.—The simple, orderly arrangement of the
clathrial and parietal lists of both ventral and dorsal
sides of the rhabdosome, as well as the square, cli-
macograptid thecal profile, are characteristic of the spe-
cies. The single, central interpleural list is also typical,
but is often difficult to recognize, particularly in flat-
tened specimens, and the proximally directed ancoral
spines seem unique to the species, as noted by Bouéek
and Munch (1952).

The small number and fragmental nature of the spec-
imens prevents a more detailed description.

Subgenus SOKOLOVOGRAPTUS
Obut and Zaslavskaya, 1976

Type species.—Sokolovograptus textor (Bouéek and
Munch, 1952). Mid-Wenlock Cyrtograptus rigidus
Zone, Motol Shale, Czechoslovakia.

Plectograptus (Sokolovograptus) textor
Bouéek and Minch, 1952
Plate 2, figures 1-8

Plectograptus? textor Boucek and Minch, 1952, p. 127, text-figs.
9a-e.

?Sokolovograptus parens Obut and Zaslavskaya, 1976, pl. 3, figs.
1-8.

Plectograptus (Sokolovograptus) textor (Bouéek and Minch). Lenz
and Melchin, 1987a, pl. 3, figs. 6, 10, 13.

Material.—Nine specimens from locality 4, Cape
Phillips; eight from locality 2, Rookery Creek; and two

from locality 1, section E. Illustrated specimens consist
of GSC 78449, 103984— 103988.

Occurrence.— Rare in late Wenlock strata, but com-
mon in the early and mid-Wenlock Cyrtograptus cen-
trifugus—Cyrtograptus insectus and Cyrtograptus per-
neri—Monograptus opimus zones.

Description.— Rhabdosome rectangular in cross-sec-
tion, mostly parallel-sided and up to 8 mm long, but
a few specimens exhibit gradual distal widening to a
maximum width up to 1.5 mm exclusive of apertural
lists. Corona rounded, simple; post-coronal orifices
rectangular in outline; in some specimens, region from
corona to level of first theca may be somewhat bulbous
and inflated, and wider than regions immediately distal
of it. Virgula typically less than half length of long
rhabdosomes. Clathrial and reticular skeletal elements
almost indistinguishable on ventral and dorsal walls;
composed of irregular polygonal, triangular, or quad-
rate meshes. Meshwork more dense and less orderly
proximally, becoming progressively more orderly,
coarser, and more quadrangular distally. Thecae gen-
erally climacograptid in profile proximally, but more
orthograptid distally, about 7-8 in 5S mm. Apertural
list forming thecal “lip” generally strongly arcuate (PI.
2, fig. 2); thecal “walls” outlined by a less-curved list
or by a simple, loose, reticular network (PI. 2, fig. 5).
Thecae of most-distal region are generally defined only
by robust, highly curved apertural lists.

Remarks.—Obut and Zaslavskaya (1976) illustrated
a delicate prosicula or partial prosicula, in the early
growth stages in some of their specimens of Sokoloy-
ograptus parens. No hint of a prosicula has been seen
in the Cape Phillips specimens.

The distinguishing features of Plectograptus (Soko-
lovograptus) textor are a disorderly clathrium and re-
ticulum, which become less dense and more orderly
distally, and thecae that are more or less distinctly
orthograptid in profile distally. The species, as per-
ceived herein, differs from the similar Plectograptus?
bouceki Rickards, 1967, in being narrower, possessing
less dense clathrial/reticular elements, and in lacking
the extremely long and curved apertural list. It is re-
markably similar to Sokolovograptus parens Obut and
Zaslavskaya, 1976 in thecal as well as clathrial/retic-
ular characteristics, but appears to be consistently wid-
er. The two may be conspecific.

Plectograptus (Sokolovograptus?) species
Plate 1, figures 1-5

Material.—Two specimens from 28 m, and 24 from
68 m, at locality 1, section E. Illustrated specimens
consist of GSC 103976-103980.

Occurrence.—Late Wenlock, Cyrtograptus lund-
greni— Monograptus testis Zone.

Description.—Rhabdosome distinctly rectangular in

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 15

cross-section; coronal region bowl-shaped, rhabdo-
some widening relatively rapidly to about level of theca
2, then gradually decreasing in width distally. Corona
simple, comprised of a few sinuous lists; post-coronal
orifice indistinct, square in outline. Rhabdosomal wall
pleural lists more or less straight. Thecal walls con-
sisting of long and strongly looped apertural lists (PI.
1, fig. 5), proximal of which much less strongly curved
lists outline the thecal “‘walls’’. Internal to the apertural
list is an inwardly curved aboral list. Meshwork a loose,
irregular arrangement of coarse clathrial lists, and finer,
more regularly spaced and shaped reticular lists. Re-
ticulum progressively denser and finer with maturity.
In immature specimens, pleural, apertural, and aboral
lists may extend well beyond level of clathrium/retic-
ulum of the rhabdosomal walls, giving a ladderlike
appearance to distal walls. Virgula long and free
throughout, even in mature specimens.

Remarks.—This species is tentatively assigned to
Plectograptus (Sokolovograptus) due, in part, to the
rarity of mature specimens. Like species of Plecto-
graptus (Plectograptus) Moberg and Toérnquist, 1909,
the species is rectangular in cross-section and the vir-
gula is free throughout. It differs in possessing a dis-
orderly clathrium and relatively dense reticulum, but
its thecal lists show a distinct alternation between long
and medium length, features that are typical of Plec-
tograptus (Sokolovograptus).

The study specimens differ from those of Plecto-
graptus (Sokolovograptus) textor in possessing a more
dense and orderly reticulum. The reticular fabric of the
species is reminiscent of Spinograptus nevadensis (Ber-
ry and Murphy, 1975), as are the ladderlike walls of
immature specimens. The study specimens, however,
totally lack spines (some specimens appear superfi-
cially to possess spines, but those structures are merely
broken apertural lists).

Genus AGASTOGRAPTUS
Obut and Zaslavskaya, 1983

Type species.—Agastograptus robustus Obut and
Zaslavskaya, 1983, pl. 24, fig. 1; holotype, 251/42-4/
1'?. Early Ludlow Neodiversograptus nilssoni Zone.

Diagnosis'3.—

Clathria clearly visible; may have reticulum and zigzag membrane
in the middle of the rhabdosome. Thecal apertures with twin spi-
noreticuli-reticular ends formed by reticular fibres and lists turned
in the direction opposite the thecal mouth. Virgula placed in the
middle of the rhabdosome, apparently unattached distally (the vir-
gula is almost always broken off close to its proximal end).

Remarks.—Obut and Zaslavskaya (1983, 1986) as-
sign Retiolites nevadensis Berry and Murphy, 1975 to

' Repository unknown; not given by Obut and Zaslavskaya (1983).
'S From Obut and Zaslavskaya (1986, p. 210).

Agastograptus. Berry and Murphy (1975, p. 100), how-
ever, note only the presence of “lists that appear as
spines or flanges” and do not mention any elabora-
tions. A retention of the species within Spinograptus
Boucek and Minch, 1952 is therefore reasonable.

The chief diagnostic characteristic of Agastograptus
is the presence of spinoreticuli. Some species of the
genus are otherwise little different from Plectograptus
(Plectograptus) Moberg and Toérnquist, 1909 or Plec-
tograptus (Sokolovograptus) Obut and Zaslavskaya,
1976. Whether spinoreticuli can always be distin-
guished in specimens flattened on shale, and thereby
prevent confusion with Spinograptus Boucéek and
Munch, 1952, remains to be seen.

Agastograptus clathrospinosus (Eisenack, 1951)
Plate 3, figures 1-7; Plate 4, figures 1-9
Retiolites clathrospinosus Eisenack, 1951, p. 139, pl. 23, figs. 1, 2a,

2b.

?Spinograptus spinosus (Wood). Berry and Murphy, 1975, p. 102,
pl. 15, fig. 8.

Spinograptus cf. spinosus (Wood). Lenz, 1978, p. 636, pl. 7, figs.
3, 4.

Agastograptus clathrospinosus (Eisenack). Obut and Zaslavskaya,
1983, p. 108, pl. 25, figs. 1-3; Obut and Zaslavskaya, 1986, p.
212, figs. 2a—c.

Material.—One-hundred-ten specimens from local-
ity 6, section SJF 145; 32 from locality 1, sections E
and F. Several flattened specimens (not illustrated) have
been collected in shale from north-central Bathurst
Island (76°10'N; 99°10'W). Illustrated specimens con-
sist of GSC 99150-99153, 103989- 103997.

Occurrence.—Late Wenlock. Cyrtograptus lund-
greni— Monograptus testis and “‘Pristiograptus” luden-
sis zones, and mainly, the earliest Ludlow Lobograptus
progenitor Zone.

Description.— Rhabdosome rectangular in cross-sec-
tion, parallel-sided or widening gradually distally,
maximum observed width and length 1.3 mm and 6
mm, respectively, rhabdosome apparently open at dis-
tal end. Thecae about 8 in 5 mm. Ancora of two short
branches that quickly divide into four relatively long
branches, one pair of which joins with basal lists of
post-coronal orifices; orifices large, distinctly rectan-
gular in outline, directed laterally. Corona ofa few lists,
open, broadly bowl-shaped, base of post-coronal ori-
fice formed of long, broadly looped list that may curve
proximally (Pl. 4, fig. 7). Thecal lateral walls pleural
lists moderately undulose. Thecal lower apertural list
strongly arcuate (PI. 4, fig. 2); thecal ““hood” that marks
base of succeeding theca a strongly arcuate list, which
on the proximal side may be elaborated by a few finer
reticular lists. Thecal apertures arcuate in profile, di-
rected laterally, overall thecal profile climacograptid.
Thecal “hoods” bear a pair of marginally located, long
spinoreticuli that are up to 1.2 mm long and contain

16 BULLETIN 342

as many as 25 reticular fibres; spinoreticuli ranging
from parallel-sided to club-shaped or spatulate, some
showing evidence of continuous-sheeting peridermal
tissue. Spinoreticuli occcurring primarily as “hoods”
over thecal apertures, but may be present elsewhere,
including on the post-coronal orifice, or on mid-regions
of the rhabdosome (PI. 3, fig. 2). Clathrial framework
of interlinked and crudely alternating left and right
curved lists and thinner secondary lists; reticulum very
fine, absent in immature specimens, rare in mature
forms. Meshes 0.07-0.08 mm across. Pustules elon-
gated, in distinct rows.

Remarks.— Diagnostic characters of this species are
the relatively long and broad spinoreticuli, and the
comparatively fine and dense reticular meshwork; this
meshwork being much finer and denser than in any
other species of Agastograptus Obut and Zaslavskaya,
1983.

Spinograptus cf. spinosus (Wood) was reported in
flattened form from the Arctic Islands (Lenz, 1978).
Obut and Zaslavskaya (1983, 1986) consider this to
be Agastograptus clathrospinosus; my reexamination
of the Arctic specimens confirms this. In like manner,
the broad and poorly defined “spines” of “\Spinograp-
tus spinosus” of Berry and Murphy (1975) strongly
suggest spinoreticuli.

Agastograptus quadratus, new species
Plate 5, figures 1-10

Origin of species name.—L. quadratus = square, four-
cornered; referring to the square, boxlike profile of the
thecae.

Type specimens.— Holotype, GSC 99173; paratypes,
GSC 99171, 99172, 103998, 103999.

Material.—Hundreds of specimens'* from a single
nodule at Cape Sir John Franklin, locality 6, section
SJE 155:

Occurrence.— Early Ludlow. Lobograptus progenitor
Zone.

Diagnosis.— Large species with a simple zigzag clath-
rial skeleton, minimal reticulum, distinctly square the-
cae, and short, broad spinoreticuli.

Description.—Rhabdosome 7-8 mm long, rectan-
gular in cross-section, widening slowly from top of
coronal region to about level of first three to four the-
cae, parallel thereafter; maximum width 1.8-2.0 mm
exclusive of spinoreticuli, thecae 5—6 in 5 mm. Ancora
of two moderate-length primary, and four longer sec-
ondary branches; corona simple, broad, with gently
curved base; post-coronal orifices large, pentagonal in
outline, directed laterally, proximal margin tongue-like
(Pl. 5, fig. 10). Clathria of long, alternating left- and

'S Because the specimens are so entangled, it is impossible to give
a precise number.

right-curving lists joined to more-or-less vertical pleu-
ral lists on both sides of rhabdosome. Upper apertural
lists strongly arcuate, constituting a hoodlike structure
of one theca and the base of the succeeding theca.
Hoodlike aspect of upper apertural lists accentuated
by development of marginally positioned pairs of short,
broad, spatulate spinoreticuli containing up to 12 criss-
crossing reticular fibres (Pl. 5, fig. 8). Lower apertural
lists, corresponding to the lower apertural “‘lip”’, strongly
arcuate, joined to inwardly deflected part of the pleural
lists. Upper and lower apertural lists joined by a single,
thin, medially placed interpleural thread (PI. 5, fig. 7),
attached to which may be a vertically oriented spi-
noreticulum. Thecal profile distinctly square and cli-
macograptid, accentuated by deep, horizontally ori-
ented thecal apertures. Reticulum absent to weakly
developed, of rare crisscrossing lists joined to coarse
clathrial network. Virgula apparently free throughout.
All lists, including spinoreticuli and virgula, are pus-
tulose.

Remarks.—The most striking feature of the species
is the distinctly square or boxlike climacograptid pro-
file of the thecae, with the spinoreticuli superficially
resembling supragenicular hoods. Overall, the rhab-
dosome of the species is substantially like Plectograp-
tus macilentus (TO6rnquist, 1887), to which spinoreti-
culi have been added.

Agastograptus quadratus differs from Agastograptus
robustus Obut and Zaslavskaya, 1983 in possessing a
less orderly zigzag clathrium and, most distinctly, in
its boxlike thecae, the latter feature also readily sepa-
rating it from Agastograptus munchi (Eisenack, 1951).
Agastograptus balticus (Eisenack, 1951), while bearing
spinoreticuli, is otherwise much more like Gothograp-
tus Frech, 1897, especially species like Gothograptus
nassa (Holm, 1890), which bear thecal hoods.

The species is somewhat like “‘Retiolites” wimani
Eisenack, 1951 in its simple clathrium, but the thecal
“‘walls” of that species are inclined at a moderately
high angle to the rhabdosomal axis, and its pleural lists
are much more strongly undulose.

Paraplectograptus Subgroup!>

Genus GOTHOGRAPTUS Frech, 1897

Type species.—Retiolites nassa Holm, 1890, pl. 2,
figs. 12, 13 (holotype)'®. Late Wenlock nassa Zone,
Eksta beds, Gotland, Sweden.

Diagnosis.—Corona rounded, width may be equal
to maximum rhabdosomal width. Coronal meshwork

'S Includes Gothograptus, Holoretiolites Eisenack, 1951, Para-
plectograptus Pribyl, 1948, and Spinograptus Boucek and Minch,
1952 (described in this study), as well as Ba/ticograptus Bouéek and
Minch, 1952 (not described).

'e Repository unknown; not given by Holm (1890).

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 7

made finer through addition of reticular lists, although
not every species has a well-developed reticulum.
Rhabdosomes of most species narrow distally. Clath-
rial pattern complex and somewhat irregular; reticu-
lum often well-developed, becoming more dense with
maturity. Thecae long with climacograptid, glypto-
graptid, or pseudoglyptograptid profile, apertures di-
rected laterally, distally, or proximo-laterally. Rhab-
dosome commonly terminated by a tubular appendix
with fine meshes, or at least with a distally attached
and fairly robust virgula. Virgula may be free through
substantial part of rhabdosomal length, then moves to
ventral side and is incorporated into skeletal frame-
work, generally continuing beyond tubular appendix.

Gothograptus nassa (Holm, 1890)
Plate 6, figures 1-3, 5

Retiolites nassa Holm, 1890, p. 25, pl. 2, figs. 12-14; Wiman, 1896,
pl. 11, figs. 1, 4-6, 8-14; non figs. 2, 3, 7.

Retiolites (Gothograptus) nassa Holm. Elles and Wood, 1908, p. 343,
pl. 34, figs. 15a—d; text-fig. 225.

Gothograptus nassa (Holm). Bouéek and Minch, 1952, p. 112, pl.
1, figs. 9-11; text-figs. 2a, 3a—d; PaSkevicius, 1974, pl. 14, figs.
1, 2; Berry and Murphy, 1975, p. 101, pl. 15, fig. 2; Lenz and
Melchin, 1987b, figs. 4a—e; non Lenz, 1978, p. 635, pl. 6, fig. 5 [=
Gothograptus chainos, n. sp.].

Type specimens.—Not formally designated in Holm
(1890).

Material.—Fifteen moderately preserved flattened
specimens on shale from north-central Bathurst Island
(76°10'N; 99°10'W).

Occurrence.—Latest Wenlock “‘Pristiograptus” lu-
densis Zone.

Description'’.—Rhabdosome about | cm long, ex-
clusive of appendix. Maximum width of 1.3-1.6 mm
attained in proximal region, margins remaining par-
allel throughout most of length or, more commonly,
gradually narrowing distally. Distal end abruptly nar-
rowed, continuing as parallel-sided appendix. Mesh-
work of rhabdosomal walls dense, meshes square or
rectangular. Thecal apertures obscured by sclerotized,
lunate, proximally projecting thecal hoods that are
present throughout length of rhabdosome. Thecal spac-
ing about six in 5 mm.

Remarks.—The large size and uniquely developed
sclerotized thecal hoods throughout the length of the
thabdosome are characteristic of the species.

Gothograptus chainos, new species
Plate 7, figures 1-12
Gothograptus nassa Lenz, 1978, p. 635, pl. 6, fig. 5.

Derivation of name.—Gr. chainos = open mouth,
wide gape; referring to the gaping, hoodless, thecal ap-
ertures.

7 Based on specimens flattened on shale.

Type specimens.—Holotype, GSC 104004; para-
types, GSC 104001-104003; 104005-104009.

Material.—Thirty-three well-preserved specimens
from locality 1, section F 39, Snowblind Creek. Illus-
trated specimens consist of GSC 104001-104009.

Occurrence.— Latest Wenlock ‘‘Pristiograptus” lu-
densis Zone.

Diagnosis.—Rhabdosome small, rounded in cross-
section; meshwork dense, almost entirely of clathrial
lists. Thecal apertures open and with a yawning ap-
pearance, relatively deep, rims of thecae thickened,
totally without hoods. Virgula free throughout, but at-
tached to distal end, and incorporated into well-de-
veloped tubular appendix.

Description.—Rhabdosome small, width 0.9-1.1mm,
rounded to ovate in cross-section, maximum length 5
mm. Corona rounded, bowl-shaped. Rhabdosome
widens slowly from top of corona to first theca and
then width constant or decreasing slightly thereafter.
Rarely, maximum width attained and maintained just
anterior to top of corona; rhabdosome decreases in
width toward distal end, then abruptly narrows and
develops tubular appendix. Rhabdosomal walls straight
to gently undulose. Ancoral and coronal lists thickened
in mature specimens, coronal brim may be somewhat
lip-like; post-coronal orifice ovate to rounded, with a
thickened rim (PI. 7, figs. 6, 12). Meshwork coarse and
dense in mature specimens, individual meshes sub-
rounded to polygonal in outline, about 0.2 mm in di-
ameter, composed almost entirely of clathria in which
list “‘seams” face inward; reticulum represented only
by rare, scattered hair-like lists. Thecal apertures
prominent, with gaping, mouth-like outline, surround-
ed by thickened rims; proximal side of thecal lip
straight, that of the distal side arched (Pl. 7, fig. 4);
thecae totally devoid of hoods. Thecal size and depth
generally increasing distally, occupying 4 to 4, rhab-
dosomal width; thecae about five in 5 mm. Virgula
free throughout all but distal end of rhabdosome, and
incorporated into well-developed tubular appendix.
Appendix consists of nema and a tubular meshwork
of clathrial lists; nema extends beyond end of appen-
dix.

Remarks.—Superficially, the species bears consid-
erable resemblance to the typical, but somewhat im-
mature specimens of Gothograptus nassa (Holm, 1890)
(i.e., those without thecal hoods). Differences between
the two species are as follows: 1, thecal apertures of
Gothograptus chainos project laterally, while those of
Gothograptus nassa project more or less proximally,
and tend to overhang the thecal walls; 2, Gothograptus
chainos lacks thecal hoods, even in the most mature
specimens; 3, rhabdosomal walls of Gothograptus chai-
nos are straight to gently undulose, while those of Goth-
ograptus nassa are markedly undulose, in part because

18 BULLETIN 342

of the overhanging thecal apertures; and 4, the virgula
of Gothograptus chainos is entirely free throughout all
except the distal end of the rhabdosome, whereas in
Gothograptus nassa, it is an integral part of the skeleton
throughout.

The new species is more like an undescribed species
from Germany (photographs kindly sent by H. Jaeger)
in rhabdosomal shape and theca apertural outline, but
differs in totally lacking thecal hoods and, most im-
portantly, in possessing a virgula that is free through
all but the distalmost part of the rhabdosome.

Gothograptus eisenacki Obut and Sobolevskaya, 1965
Plate 8, figures 1-9; Plate 9, figures 1-9

Gothograptus eisenacki Obut and Sobolevskaya, 1965, p. 41, pl.
3, figs. 5, 6; Lenz and Melchin, 1987a, pl. 2, figs. 5, 13, 14; pl.
3, figs. 1, 8.

Type specimens.—Obut and Sobolevskaya, 1965, pl.
3, fig. 5 (holotype, 1087a/24!8). Late Wenlock Mono-
graptus testis Zone, central Taimyr, Russia.

Material.—Sixty-nine specimens from locality 1,
section E; three from locality 1, section 10C, 48 from
locality 1, section 10D, 20 from locality 1, section
10D?, and 53 from locality 2, Rookery Creek. Illus-
trated specimens consist of GSC 78440, 78446, 99146—
99149, 104011-104018.

Occurrence.— Cyrtograptus lundgreni—Monograptus
testis and “‘Pristiograptus” ludensis zones.

Description.—Rhabdosome round to ovate in cross-
section, small, seldom more than 0.7—0.8 mm in max-
imum width, but variable in length; length seldom more
than 3 mm, but a single incomplete specimen illus-
trated herein and in Lenz and Melchin (1987a) prob-
ably exceeded 5 mm. Rounded, complex, bulbous co-
ronal region; post-coronal orifices broadly lunate in
outline; large dorsal and ventral openings on theca 1
side of rhabdosome (PI. 8, fig. 1). Maximum width of
rhabdosome attained about midlength of theca 1!; width
narrowing distally; rhabdosome generally terminating
in a tubular appendix or, in immature specimens, in
a distally attached virgula. Toial thecal number varies
considerably, depending on length of rhabdosome, from
as few as two per side to sometimes four and, in one
case seven per side. Thecae distinct, even in immature
specimens; walls strongly rounded in cross-section and
markedly undulose in profile, formed of relatively fine
meshwork of clathrium and finer reticulum. Thecal
walls long, that of one theca generally projecting inside
and below apertural lip of previous theca; floor of theca
1? extends inside corona almost to base of ancora.
Thecal profile more-or-less pseudoglyptograptid in
profile. Main skeleton a relatively coarse clathrium of

'S Repository unknown; not given by Obut and Sobolevskaya
(1965).

long, more-or-less alternately left- and right-curving,
arcuate lists, between which is the relatively dense re-
ticulum. Reticulum added progressively, so that im-
mature specimens are relatively coarsely meshed while
mature specimens are finely and heavily meshed. Vir-
gula free and central through main part of rhabdosome,
distally joined by horizontal lists to clathrium. Distal
end of mature specimens with variable length, cylin-
drical, fine-meshed, spirally developed, tubular appen-
dix that incorporates the virgula on one side; free vir-
gula may extend some distance beyond end of appendix.
In immature specimens, appendix may not be devel-
oped.

Remarks.—The most striking feature of this species
is its variable length, and consequently the total num-
ber of thecae. Thecal number ranges from two to seven
in specimens from Arctic Canada, and Kozlowska-
Dawidziuk (1990) illustrates specimens from Poland
with up to ten thecae per side; in all other ways long
and short specimens are identical. The rhabdosomal
length and thecal number apparently bear no relation-
ship to maturity, since the appearance of the appendix
in essence marks the end of lengthening. No pattern
such as progressive lengthening or shortening through
time, nor of dimorphism, is apparent; considerable
variation may occur in any one collection.

Gothograptus eisenacki is, because of its size, shape
and unique thecal profile, readily distinguishable from
all other species of Gothograptus Frech, 1897.

Gothograptus marsupium, new species
Plate 10, figures 1-9; Plate 11, figures 1-8

Derivation of name.—L. marsupium = pouch, bag,
purse; referring to the pouch-like shape of the thecae.

Type specimens.—Holotype, GSC 104024; para-
types, GSC 99174-99176, 104019-104023; 104025—
104030.

Material.—Two-hundred-fifteen specimens from lo-
cality 1, section E; six from locality 1, section SBC
10C; 15 from locality 1, section 10D; and four from
locality 2, Rookery Creek. Illustrated specimens con-
sist of GSC 99174-99176, 104019- 104030.

Occurrence.—Late Wenlock Cyrtograptus lund-
greni— Monograptus testis Zone.

Diagnosis.—Rhabdosome ovoid-rectangular in
cross-section, corona open and tapering, thecae un-
dulose, pouch-like, skeletal meshwork fine and rela-
tively delicate, distal end weakly to moderately nar-
rowing, apparently without appendix, but with a long
virgula attached to, and extending well beyond distal
part of rhabdosome.

Description.—Rhabdosome ovoid-rectangular in
cross-section, coronal region V-shaped to rounded,
maximum width 1.2—-1.4 mm across first two thecae,
parallel-sided or gently tapering through the distance

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 19

of the next one or two pairs of thecae, consistently
narrowing thereafter, sometimes rapidly; distal end may
be very narrow. Virgula consistently attached to distal
region by one or several lists (Pl. 10, fig. 4), sometimes
extending as a simple rod for a distance equal to the
total length of the rhabdosome. Two to rarely five,
most commonly three thecae on each side. Corona
simple, open; post-coronal orifices ovate to rectangu-
lar. Large rounded ventral and dorsal openings present
on theca 1? side of rhabdosome (PI. 10, figs. 3, 6). Main
skeletal framework of pleural lists that zigzag prom1-
nently; thecal lip apertural list situated approximately
at medially incurved part of the pleural list. Median
part of outer wall of thecae curved and markedly bulg-
ing outwards (PI. 10, fig. 7; pl. 11, fig. 7), formed of
finer, intermeshed secondary lists, the density of which
increases with maturity. Internally, a curved inner con-
necting list may join the medial region of one thecal
network to that of the previous theca (Pl. 10, fig. 7).
Thecae long, with an overall pronounced sigmoidal or
even pseudoclimacograptid profile; floor of theca 1?
extended below level of top of corona. Thecae about
six in 5 mm. Distalmost thecae consist only of primary
clathrial framework. Virgula free and central until about
level of thecae 3 to 5, then joined by one to several
horizontal lists to a clathrial list, distal of which it is
free, and may be very long, equal to length of rhab-
dosome; no evidence of tubular appendix as in Goth-
ograptus nassa (Holm, 1890) or Gothograptus eisen-
acki Obut and Sobolevskaya, 1965. Skeletal meshes
polygonal, meshwork moderately fine, progressively
finer with maturity. Meshwork, with the exception of
an open coronal region, more dense proximally. Main
skeletal framework clathrial, all finer skeletal lists re-
ticular, progressive addition of reticulum leads to pro-
gessively finer meshwork of more mature specimens.

Remarks.—A\though lacking any evidence of a dis-
tal tubular appendix, the morphologic features of this
species, such as pronounced distal narrowing of the
rhabdosome, anchoring of the virgula to the distal part
of the rhabdosome, curved and complex thecal struc-
tures, and large, proximal ventral and dorsal openings,
are clearly those of Gothograptus Frech, 1897.

This species is distinguished from Gothograptus nas-
sa by its more rectangular cross-sectional shape, sig-
moidal thecal profile, coarser reticulum and lack of
thecal hoods, and by the fact that thecal openings are
directed distally. From Gothograptus eisenacki it 1s
readily distinguished by its much greater size (Pl. 11,
fig. 8), rectangularity, and relatively coarser reticulum;
however, the similarity in thecal profile is notable. It
is like Gothograptus intermedius Boucek and Minch,
1952 in general form, but differs from that species in
greater amount of reticulum (although it is possible
that maturation would add a greater amount of retic-

ular tissue to that species) and, most importantly, a
different thecal profile and apertural orientation.

In the zigzag nature of its outer wall, with the thecal
apertures developed in the most medially curved part
of the pleural lists, and the absence of a tubular ap-
pendix, Gothograptus marsupium 1s like Gothograptus
pseudospinosus (Eisenack, 1951) and Gothograptus ko-
zlowskii Kozlowska-Dawidziuk, 1990; both of these
species, however, possess spinelike thecal structures
and their meshwork is finer and more uniform.

Gothograptus? species
Plate 6, figures 4, 6-8

Material.—Six specimens, most apparently imma-
ture, from locality 1, section SBC 10B. Illustrated spec-
imens consist of GSC 99177-99179, 104000.

Occurrence.—Late Wenlock Cyrtograptus lund-
greni-Monograptus testis Zone.

Description.—Rhabdosome moderate-sized, maxi-
mum length 3.5 mm, ovate in cross-section, maximum
width of 0.9-1.1 mm near proximal end, then of con-
stant width or gradually narrowing distally. Virgula
free, length equal to that of rhabdosome in some spec-
imens. Corona bowl-shaped, moderately complex; post-
coronal orifices lunate in outline (Pl. 6, fig. 8); mod-
erate-sized, kidney-shaped ventral and dorsal openings
present above corona. Pleural lists of thecae zigzag, the
short, medially projecting portion joining strongly
curved apertural lists, and the long outward-projecting
pleural lists forming thecal lateral margins. Thecal walls
formed of a complex and interlocking meshwork of
lists that may extend below (more proximal of) level
of lip of preceding theca, giving thecae a distinct glyp-
tograptid profile, with apertures opening in a distola-
teral direction (PI. 6, figs. 4, 7). Thecal walls of both
thecae 1' and 1? extend below top of coronal rim.
Thecal spacing difficult to measure, about six to seven
in 5 mm. Ventral and dorsal sides of rhabdosome cov-
ered with meshwork, but clathrium and reticulum dif-
ficult to distinguish. Density of meshwork decreases
distally on ventral and dorsal walls as well as on thecal
walls.

Remarks.— The generic assignment of this species is
questionable. Like the type species of Gothograptus
Frech, 1897, it is ovate in cross-section, may decrease
in width distally, and possesses complex, curved and
long thecal walls; on the other hand, in none of the
specimens is the virgula seen to join with the skeleton.
Whether this is real, or merely due to immaturity or
incompleteness of the material, is unclear.

This species differs from Gothograptus marsupium,
n. sp., the most similar form, in its ovate cross-section,
more irregular and slightly coarser meshwork and, par-
ticularly, in that its thecal apertures open distolaterally.
From immature specimens of Gothograptus nassa

20 BULLETIN 342

(Holm, 1890) (see Lenz and Melchin, 1987b), it differs
in possessing a finer and more complex meshwork, and
having differently shaped and oriented thecae.

Genus HOLORETIOLITES Eisenack, 1951

Type species.— Retiolites mancki Minch, 1931!9.

Occurrence.—Early Ludlow colonus beds, Baltic
limestones, Germany.

Diagnosis*®.—Rhabdosome small. Corona always
developed, mediolar part cylindrical, quadrilateral, or
conically narrowing distally. Virgula in corona and ex-
tending to about mediolar region, central. Not known
distally. Narrow, cylindrical appendix in some species.
Skeleton of clathrium only [Holoretiolites (Holoretiol-
ites)] or clathrium and reticulum [Holoretiolites (Bal-
ticograptus) Boucek and Munch, 1952].

Remarks.—Bulman (1970, p. 131) places Baltico-
graptus in synonymy with Holoretiolites. However, be-
cause of the well-developed reticulum in Balticograp-
tus, 1t seems preferable to follow Boucek and Minch
(1952) in making it a subgenus of Holoretiolites. This
is analogous to the relationship between Plectograptus
(Plectograptus) Moberg and Térnquist, 1909 and Plec-
tograptus (Sokolovograptus) Obut and Zaslavskaya,
1976.

The close similarity in mode of rhabdosomal con-
struction, including the manner of development of the
first two thecae directly from ancoral lists (Eisenack,
1951, text-fig. 10), termination in a distal appendix,
as well as stratigraphic position, suggest that Holore-
tiolites is directly derived from Gothograptus.

Subgenus HOLORETIOLITES Eisenack, 1951

Holoretiolites (Holoretiolites) mancki (Munch, 1931)
Plate 12, figures 1-12
Retiolites mancki Minch, 1931, p. 35, figs. 1-13; Eisenack, 1935,
pl. 4, fig. 15; pl. 7, fig. 2.
Holoretiolites (Holoretiolites) mancki (Miinch). Boucek and Minch,
1952, text-fig. 4a.

Material.—Thirty-three specimens from locality 1,
section SBC 4, 7 m; five from locality 1, section B; two
from locality 1, section SBC 8E, and 24 from locality
3, section MCM. Illustrated specimens consist of GSC
99167-99170, 104031-104033.

Occurrence.—Early Ludlow Lobograptus progenitor
and Saetograptus fritschi linearis zones.

Description.—Rhabdosome rounded in cross-sec-
tion, 2.5-3.0 mm long (including tubular appendix),
maximum width about 0.6 mm across theca 1, tapering
gradually distally, maximum thecal number three to
four per side, distal end terminated by a short tubular

'° Repository unknown; not given by Miinch (1931).
20 Modified after Boucek and Miinch (1952).

appendix. Virgular maximum length about 4 that of

rhabdosome. Corona simple, open, bowl-shaped; post-

coronal orifices large, pentagonal in outline, directed —
laterally. Skeletal clathrium zigzag, of curved, left- and

right-alternating lists, forming pentagonally shaped —
meshes on both ventral and dorsal sides of rhabdo-

some. Reticulum not present. Thecal lower apertural

lip a short, gently curved list; upper apertural lip thecal

hoods comprise long, overhanging, strongly arcuate
lists (PI. 12, fig. 5). Arcuate list joined to lower apertural
list of succeeding theca by single medially placed in-
terpleural list. Thecal apertures directed proximo-lat-
erally. Distally, clathrial elements converge and fuse
with terminal, variable-length, spiralled, fine-meshed
tubular appendix (PI. 12, figs. 2, 10, 11), beyond which
an unsupported nema may extend. No evidence of
virgula seen in appendix.

Remarks.—Holoretiolites (Holoretiolites) mancki is
distinguished from the only other known species of the ©
subgenus, Holoretiolites (Holoretiolites) simplex (Ei-
senack, 1935), by being relatively much longer, more
gently tapering toward the distal end, and by possessing
a terminal appendix, unlike the simple, sharp point
seen in the latter species. All specimens recovered in
this study readily fall into the definition of Holore-
tiolites (Holoretiolites) mancki, although Lenz and
Melchin (1987a) described a single specimen tenta-
tively identified as Holoretiolites (Holoretiolites) sim-
plex from the same section.

Berry and Murphy (1975) report Holoretiolites from
Nevada. Their specimens are not sufficiently well-pre-
served to compare with other species, although two of
their illustrated specimens with long, gently tapering
rhabdosomes and a light skeletal framework are sug-
gestive of Holoretiolites (Holoretiolites) mancki.

Genus PARAPLECTOGRAPTUS Piibyl, 19487!

Type species.—Retiolites eiseli Manck, 1917. Re- |
pository and catalogue number unknown.

Occurrence.—Late Wenlock Monograptus testis
Zone, Germany.

Diagnosis*?.—Corona simple, rhomboid, square in
cross-section. Rhabdosome walls (clathrium) sharply —
angular. Virgula incorporated in, and part of, ventral —
wall throughout. Horizontal lists arise alternately on
left and right side of virgula and join outer walls. Dorsal
wall either of zigzag pleural lists connecting directly to
outer walls, or with short horizontal lists connecting
pleural lists and outer walls. Reticulum always makes
up dorsal wall, may or may not be present on ventral
wall of rhabdosome, is light or dense, generally finer
than clathrium, and may or may not be uniformly

2! = Pseudoplectograptus Obut and Zaslavskaya, 1983.
22? Modified from Lenz and Melchin (1987a).

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 21

distributed. Prosicula, represented mostly by threads
and a complete apertural region (PI. 13, figs. 5-10),
rarely seen.

Remarks.—As noted in Lenz and Melchin (1987a),
the definition of Paraplectograptus was expanded to
encompass forms that may have a moderately dense
reticulum, so long as the virgula is an integral part of
the ventral clathrial wall throughout. This definition
is further extended herein, considering the dense re-
ticulum in Paraplectograptus sagenus, n. sp. This ap-
pears to be justified by a gradation among three species:
Paraplectograptus eiseli (Manck, 1917) (almost no re-
ticulum), Paraplectograptus praemacilentus (Bouéek
and Minch, 1952) (moderate amount of reticulum),
and Paraplectograptus sagenus, n. sp. (dense reticu-
lum). Furthermore, and as already outlined in Lenz
and Melchin (1987a), there is good reason for sug-
gesting that the virgula of the type species, Paraplec-
tograptus praemacilentus, is incorporated into the skel-
etal wall; thus, the need for a new genus
(Pseudoplectograptus Obut and Zaslavskaya, 1983) for
Paraplectograptus praemacilentus is removed. Para-
plectograptus is unique among the plectograptines in
that it is the only genus whose virgula is continuously
part of the ventral skeletal structure of all species.

Of particular interest is the nature of the clathrium
and reticulum. The corona, pleural lists, aboral lists,
virgula, and its attached horizontal lists are entirely
clathrial. On the other hand, the skeletal lists of the
entire dorsal wall of the rhabdosome, and those ele-
ments ventral to the virgula are reticulum. This feature
appears to be unique among the plectograptines. A
feature of further interest is the rare occurrence of a
vestigial prosicula. The rare presence ofa prosicula has
been recognized in a single small collection from a talus
nodule of probable early Wenlock age (zonal assign-
ment uncertain) (PI. 13, figs. 5-10). Because all spec-
imens are immature, species identification 1s not pos-
sible.

Paraplectograptus eiseli (Manck, 1917)
Plate 13, figures 1-4

Retiolites eiseli Manck, 1917, p. 338, text-figs. 1-5; Hundt, 1924, p.
81, pl. 11, fig. 26; pl. 12, figs. 7-10.

Paraplectograptus eiseli (Manck). Boucek and Munch, 1952, p. 136,
pl. 1, fig. 8; text-figs. | la—h; Lenz and Melchin, 1987a, pl. 3, figs.
Ae 2; 12.

Material.—Twelve specimens from locality 1, sec-
tion E; four from locality 1, section SBC 10D; and six
from locality 4, section CP 850, Cape Phillips. Illus-
trated specimens consist of GSC 78450, 104034—-
104036.

Occurrence.— Late Llandovery to late Wenlock Cyr-
tograptus lundgreni—Monograptus testis Zone [rare].

Description.—Rhabdosome relatively long and nar-

row, relatively square in cross-section; skeletal frame-
work orderly, of predominantly clathrial lists. Corona
square, simple; post-coronal orifices pentagonal in out-
line, directed laterally. Virgula joins to alternating left
and right horizontal (parietal) lists, which in turn join
pleural and apertural lists. Dorsal side with zigzag list
that alternately joins directly to pleural lists; resulting
meshwork distinctly triangular (Pl. 13, fig. 2). Aper-
tural lists prominently curved, marking the apertural
lip. Reticulum present or absent on ventral wall, or-
derly and simple on dorsal wall; secondary reticulum,
when present, scattered over rhabdosome. Rhabdo-
some 0.7—0.9 mm wide, thecal spacing six to seven in
5 mm.

Remarks.—This species, which is rare in the study
collections, has been listed by Thorsteinsson (1958) as
occurring at 20 stratigraphic levels collections from
locality 4 in strata ranging in age from late Llandovery
to late Wenlock, but these have not as yet been illus-
trated.

Paraplectograptus praemacilentus
(Boucek and Munch, 1952)
Plate 14, figures 1-6

?Retiolites tenuis Eisenack, 1951, p. 131, pl. 21, figs. 1-13; pl. 22,
figs. 1-3; text-figs. 1, 2.

Plectograptus praemacilentus Bouéek and Minch, 1952, p. 124, pl.
1, fig. 5; text-figs. 8a-d; Lenz, 1978, p. 635, pl. 6, figs. 4, 8, 10,
isle

?Gothograptus tenuis Obut and Sobolevskaya, 1965, p. 40, pl. 3, figs.
1-4.

Paraplectograptus praemacilentus (Boucek and Minch). Lenz and
Melchin, 1987a, p. 166, pl. 3, figs. 2, 3, 5, 9.

Material.—Sixteen specimens from locality 1, sec-
tion E; 23 from locality 1, section F; eight from locality
1, section SBC 10C; three from locality 1, section SBC
10D; eight from locality 2; and 32 from three collec-
tions at locality 4. Illustrated specimens consist of GSC
78441, 104041-104045.

Occurrence.— Late Llandovery to late Wenlock (Lenz
and Melchin, 1987a), most common in late Llandov-
ery and early Wenlock strata; may extend into latest
Wenlock “‘Pristiograptus” ludensis Zone.

Description.— Rhabdosome rectangular in cross-sec-
tion, 4-5 mm long with maximum width of 0.9-1.0
mm attained between thecae | and 3, rhabdosome
parallel-sided thereafter. Corona simple, open, flat-
bottomed, bowl-shaped; post-coronal orifices pentag-
onal in outline, directed laterally. Skeleton of zigzag
clathria joined laterally, alternately to left and right
horizontal parietal lists, which in turn join with the
strongly zigzag pleural lists. Main skeleton-building
clathrium identical on dorsal and ventral sides, with a
prominently hexagonal network. Pleural lists joined by
horizontal, inward-deflected aboral lists. Virgula moves
to ventral side about the level of the second theca,

DD BULLETIN 342

alternately giving rise to left and right parietal lists that
join aboral lists; not directly connected to zigzag clath-
rium. Apertural lists strongly arcuate. Secondary re-
ticulum lightly built, scattered throughout and not
forming a distinct pattern, but often retaining a crude
zigzag pattern.

Remarks.—This species differs from Paraplecto-
graptus eiseli (Manck, 1917) chiefly in its possession
of a hexagonally arranged reticulum rather than a tri-
angular one, as well as being more robust and pos-
sessing a moderately well-developed secondary retic-
ulum. In overall rhabdosomal shape, it is more akin
to Paraplectograptus sagenus, n. sp.; the latter, how-
ever, has a much more strongly developed reticulum,
to the point where the medial zigzag pattern is not
visible and, uniquely, possesses thecal walls.

The distinction between this species and Paraplec-
tograptus eiseli may at times be subtle, since some
specimens of Paraplectograptus praemacilentus are al-
most devoid of reticular lists. Paraplectograptus prae-
macilentus is more robust, with a broader corona, and
its walls are typically parallel throughout the length of
the rhabdosome. The prime distinction, however, is
that in Paraplectograptus eiseli, the zigzag lists are in
direct contact with the pleural lists, whereas in Para-
plectograptus praemacilentus, short, horizontal lists are
always inserted between the zigzag and pleural lists (PI.
14, fig. 1).

Lenz and Melchin (1987a) suggested that Retiolites
tenuis Eisenack, 1951 is an early growth stage of the
mature Paraplectograptus praemacilentus. If true, Par-
aplectograptus praemacilentus (Bouéek and Miinch)
would be a junior synonym of Paraplectograptus tenuis
(Eisenack). However, the immaturity of Eisenack’s
specimens prevents any confident species assignment,
although Eisenack’s species is clearly assignable to Par-
aplectograptus, a fact already recognized by Bouéek
and Munch (1952).

Paraplectograptus sagenus, new species
Plate 15, figures 1-9; Plate 16, figures 1-8

Origin of species name.—L. sagena = fish net; re-
ferring to the well-developed skeletal meshwork of the
thecal wall.

Type specimens.—Holotype, GSC 104048; para-
types, GSC 99154, 99155, 99157, 99158; 104046,
104047; 104049-104054.

Material.—Eighty-two specimens from locality 1,
section E; 100 from locality 1, section SBC 10A; 130
from locality 1, section SBC 10B; and ten each from
locality 1, sections SBC 10C and SBC 10D. Illustrated
specimens consist of GSC 99154, 99155, 99157, 99158,
104046-104054.

Occurrence.—Late Wenlock Cyrtograptus lund-
greni— Monograptus testis Zone.

Diagnosis.—Rhabdosome ovate in cross-section,
widening gradually throughout most of length. Clath-
rium and reticulum difficult to distinguish, meshwork
moderately dense and uniform. Thecal walls marked
by complex subapertural lists.

Description.—Rhabdosome ovate in cross-section,
up to 8 mm long, widening gradually from about 0.75
mm across corona to a maximum width of 1.1-1.3
mm. Thecae six to seven in 5 mm. Corona bowl-shaped,
open; post-coronal orifices pentagonal in outline, di-
rected laterally to slightly proximo-laterally. A medi-
ally placed, kidney-shaped opening, bordering on co-
rona, present on ventral and dorsal side of rhabdosome.
Main rhabdosomal skeleton of strongly zigzag margin-
al pleural lists and transversely connected apertural
lists (Pl. 16, fig. 1). Virgula alternately giving rise to
left and right bars that join to inwardly curved, inward-
positioned aboral lists; these, in turn, join with pleural

lists at their most medially deflected juncture. Aper- |

tural lists robust and strongly outwardly curved. Thecal
walls outlined by a curved, relatively fine network of
reticular lists (Pl. 15, fig. 6). Thecal profile orthograptid
to glyptograptid. Thecal wall network denser in mature
specimens. Reticular meshwork on ventral and dorsal
surfaces relatively dense, evenly distributed, individ-
ual meshes round, square or polygonal, 0.08—0.1 mm
across. Meshwork relatively uniform laterally, but less
dense in distal parts of long specimens.

Remarks.—Paraplectograptus sagenus, n. sp. differs
from Paraplectograptus praemacilentus (Bouéek and
Munch, 1952) in two features: the more dense and
uniform meshwork, and the possession of a thecal wall
meshwork, features that also differentiate it from Par-
aplectograptus sp. A of Lenz and Melchin (1987a).
Comparison with the heavily meshed “‘Plectograptus”
lejskoviensis Bouéek, 1931 (Bouéek and Miinch, 1952)
is difficult since that species is illustrated only by a
single line-drawing. With a stated width of 3.5 mm,
however, it is readily distinguished from Paraplecto-
graptus sagenus.

Genus SPINOGRAPTUS Bouéek and Minch, 1952

Type species.—Retiolites (Gothograptus) spinosus
Wood, 1900. Repository and catalogue number of ho-
lotype unknown. Early Ludlow Neodiversograptus nils-
soni Zone, Welsh borderland, United Kingdom.

Diagnosis*>.—Like Plectograptus, with well-devel-
oped reticulum and with characteristic spinelike awns
arising from the two margins of the upper apertural
list. Mesial transverse list lacking. Virgula distally at-
tached to clathrium. Micro-ornamentation of elongate
pustules in parallel rows.

Remarks.—The presence of a distally attached vir-

23 Emended after Boucek and Miinch (1952).

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 23

gula has not been previously reported for this genus
and it is unclear whether this feature exists in the type
species, Spinograptus spinosus. Boucek and Munch
(1952, p. 133), in discussing the virgula of that species,
comment ‘“‘we must conclude that it is free.”” However,
because the virgula is distally attached in the two spe-
cies described herein, I assume that this is also true of
the type species. This observation has important evo-
lutionary ramifications for the genus.

Spinograptus apoxys, new species
Plate 17, figures 1-7; Plate 18, figures 1-7

Origin of species name.—Gr. apoxys = tapering off,
becoming less; referring to the distally decreasing width
of the rhabdosome.

Type specimens.—Holotype, GSC 104055; para-
types, 99164— 99166, 104056-104058.

Material.—Ten specimens from locality 1, section
F: six from locality 1, section 8 A, five from locality
1, section 10 C, and four from locality 1, section 10
D. Illustrated specimens consist of GSC 99164, 99166,
104055-104058.

Occurrence.—Late Wenlock Cyrtograptus lund-
greni- Monograptus testis Zone.

Diagnosis.—Rhabdosome large, attaining max1-
mum width at level of thecae 2 or 3, width decreasing
distally; meshwork dense, uniform; thecae climaco-
graptid, apertures large, deep. Sclerotized sigmoidal
structure and stomata.

Description.—Rhabdosome rectangular in cross-sec-
tion, up to 8 mm long, broadly to narrowly rounded
proximally, attaining maximum width of 1.8-2.0 mm
between levels of thecae 2 and 3, gradually narrowing
distally, distal end apparently open. Corona rounded
to V-shaped, moderately deep and complex; post-co-
ronal orifices rectangular, directed laterally. Openings
kidney-shaped, moderate-sized, proximal of base of
theca 12 on ventral and dorsal walls of rhabdosome
(Pl. 17, fig. 7). Clathrium of loose, square to polygonal
lists and much finer reticulum forming a uniform
meshwork whose meshes are 0.13—0.16 mm across.
Stomata 0.15—0.22 mm in diameter may be present on
both sides of rhabdosome and raised above level of
meshwork (PI. 17, figs. 6, 7); without thickened rims.
Pleural lists alternately straight and strongly medially
deflected, deflection U-shaped. Upper part of U’ joined
to distally arched upper apertural list from which pro-
ject long, paired curved spines. Spines linked near bas-
es by one or more commonly two horizontal lists, im-
parting the effect of a prominent thecal hood. Lower
apertural lists about midway between preceding and
succeeding spine pairs, joined by one or two inter-
pleural lists, which in turn join lateral lists behind and
slightly above level of thecal hood, Long thin thread,
the inner connecting list, extends inward in a broad

arc from the horizontal list (the upper apertural list),
behind the thecal hood of one theca, to that of the
preceding theca (Pl. 17, fig. 5; pl. 18, fig. 6). Solid
sclerotized, vane-like sigmoidal structure (Pl. 18, fig.
5), connected to base of lower apertural list, extending
downward inside the upper apertural list of the pre-
ceding theca, curving inwardly and downwardly, and
finally connecting with inner connecting list (see Text-
fig. 4). Thecal profile distinctly climacograptid; aper-
ture large (Pl. 17, figs. 1, 2), almost half the thecal
length, deep, directed horizontally. Virgula of mature
specimens attached to skeleton distally (Pl. 17, fig. 4;
pl. 18, fig. 2), but free in immature specimens.

Remarks.—Distinctive of this species are the distal
narrowing of the rhabdosome, the strong climacograp-
tid profile of the thecae and the hoodlike thecal spines.
The presence of stomata, inner connecting lists, and
the vane-like sigmoidal structure are unusual. An inner
connecting list has previously only been seen in Pseu-
doretiolites Boucek and Minch, 1944 (Lenz and Mel-
chin, 1987a, p. 164), but stomata are present in other
retiolitids (e.g., Pseudoretiolites, Pseudoplegmatograp-
tus Pribyl, 1948, and Stomatograptus Tullberg, 1883).
The vane-like sigmoidal structure commonly, but not
invariably, appears early in the development of the
rhabdosome.

Spinograptus nevadensis (Berry and Murphy, 1975)
Plate 19, figures 1-6; Plate 20, figures 1-7
Retiolites nevadensis Berry and Murphy, 1975, p. 100, pl. 15, figs.

5, 6; Lenz, 1978, p. 636, pl. 7, figs. 1, 2, 5, 6.

Agastograptus nevadensis (Berry and Murphy). Obut and Zaslav-
skaya, 1986, p. 210.

Type specimen.—Specimen UCR 4225/3 (Berry and
Murphy, 1975, pl. 15, fig. 5). Late Wenlock Mono-
graptus testis Zone.

Material.—Two specimens from locality 1, section
SBC 10 B; two from locality 1, section 10 C; 12 from
locality 1, section 10 D; 12 from locality 1, section 10
E; and nine from locality 1, section E 68. Illustrated
specimens consist of GSC 99159-99162, 104059-
104061.

Occurrence.—Late Wenlock Cyrtograptus lund-
greni— Monograptus testis Zone.

Description.—Rhabdosome of moderate size, at least
7 mm long (flattened specimens up to 15 mm), rect-
angular in cross-section, maintaining constant width
of 1.2-1.4 mm (exclusive of spines) for about three-
quarters of length, then narrowing to a width equal to
about half maximum width. Thecae four-and-one-half
to five in 5 mm. Corona open, of four primary branch-
es, each of which divides into shorter, finer secondary
lists; broad, flat-bottomed and bowl-shaped (Pl. 19,
fig. 1); post-coronal orifices large, rectangular to pen-
tagonal in outline, directed laterally. Rhabdosomal

24

BULLETIN 342

Table 1.—Matrix of morphologic features of the plectograptines. Presence of a feature is indicated by a ‘+’, absence by ‘—’; ‘+’ indicates

presence or absence, depending on the species.

Matrix of morphologic characteristics of Plectograptinae

5 6 7 8 9

~
N

agastogr
balticogr =
gothogr =
holoret =
paraplecto

p. (sokolov)
p. (plecto) =
spinogr =
retiolites

t+tt+++4¢4¢4¢+4
lt+tettttt¢i]yu
(eee si rte aie fetta ats
I
1+ +
|
|
++ 4 +

at,
+

= = = a =

11 2” 13) 14 15167 AS 9 eee
Boot
+ + + =- + = = = = =
t+ -— + + = + + = = = =
$ = + = S$ |S £ = SSS

— _— aE _— —
SS eS =

$e = Ss = + St

1 = prosicula; 2 = ancora with 4 main lists; 3 = rim of post-coronal orifice attached only to one pair of ancoral main branches; 4 = round
pustular ornament; 5 = virgula incorporated into wall; 6 = virgula attached distally only; 7 = virgula free; 8 = rectangular cross section; 9 =
round cross section; 10 = orthogr-glyptogr thecal profile; 11 = thecal mms thickened; 12 = orthogr-climacogr thecal profile; 13 = thecal walls
long; 14 = reduced reticulum; 15 = no or only trace reticulum; 16 = thecal walls complex; 17 = distal appendix or terminal process; 18 =
elongate pustular ornament; 19 = thecal spines; 20 = boxlike thecal profile; 21 = spinoreticuli.

walls of straight to weakly undulatory pleural lists.
Clathrium comprises successive alternately left- and
right-curved lists; reticulum of moderately fine, equi-
sized, subrounded to quadrangular meshes about 0.1
mm across; reticular density increasing with maturity,
uniform except at lateral margins, where meshwork
more coarse. Upper apertural lists strongly curved to
broadly U-shaped, with long, laterally curved paired
spines at margins (Pl. 20, figs. 1, 2). Directly inward
of and just inside lateral margin of rhabdosome, hor-
izontal (aboral?) list joins pleural lists (Pl. 20, fig. 6).
Lower apertural lists weakly curved, joined to above-
mentioned horizontal list by one or two interpleural
lists. Thecal margin parallel to rhabdosomal axis. Vir-
gula free through all but distalmost part of rhabdo-
some, where attached by one or two lists. In flattened
specimens, virgula extends well beyond distal end of
rhabdosome.

Remarks.—Spinograptus nevadensis is character-
ized by a uniform, orderly and dense meshwork, and
thecal walls (pleural lists) that are essentially planar
and parallel to the rhabdosomal axis for most of its
length, whereas the type species, Spinograptus spinosus
(Wood, 1900) possesses thecae with a strong ortho-
graptid profile (Elles and Wood, 1908; Obut and Zas-
lavskaya, 1983, 1986). It differs from S. apoxys, n. sp.
in being predominantly parallel-sided rather than con-
tinuously narrowing distally, and its thecal apertures
are flush with the rhabdosomal wall rather than being
a deep U-shaped structure.

Elles and Wood (1908, p. 345) suggest the presence
of a sicula in S. spinosus; this has not been reported
from the isolated specimens of Obut and Zaslavskaya
(1986), and no hint exists in the study specimens of S.
nevadensis or of S. apoxys, n. sp.

APPENDIX

COLLECTING LOCALITIES AND THEIR
CONTAINED FAUNAS

The Cape Phillips Formation (Thorsteinsson, 1958),
a basinal limestone and shale facies and the main grap-
tolite-bearing unit of the region, is widespread through-
out the Arctic Islands, and consequently graptolites are
widely known (Melchin, 1989; Lenz and Melchin,
1990). In the central part of the Arctic Islands, and
chiefly on Cornwallis Island, graptolite-bearing nod-
ules are particularly abundant. Graptolite-bearing nod-
ules are common in Llandovery to mid-Wenlock stra-
ta, but are much less common in upper Wenlock and
Ludlow rocks. In this study, only the Snowblind Creek
locality has yielded dozens of both upper Wenlock and
Ludlow nodules.

Late Wenlock and Ludlow plectograptine-bearing
nodules were collected from six localities (Text-fig. 1):
locality 1, Snowblind Creek (75°11'N, 93°47'W); lo-
cality 2, Rookery Creek (75°22'N, 95°46'W); locality
3, unnamed creek west of Cape Manning (75°27.5'N,
94°17'W: collected by M. J. Melchin); locality 4, Cape
Phillips Formation, type section (75°37'N, 94°30'W):
locality 5, Baillie Hamilton Island, south shore
(75°45'N, 94°22'W): and locality 6, Cape Sir John
Franklin, Grinnell Peninsula (76°42.5'N, 95°53’W).

Locality 1.—Snowblind Creek, because of its rich and nearly con-
tinuous sequences of nodular faunas, is the most important locality.
As a result, sections there were sampled twice, in 1988 and 1990.
Five sections, labelled A, B, D, E, and F were sampled in the 1990
field season (Text-figs. 1, 2). Section C of 1990 was unfossiliferous.
The same sections, when sampled previously in 1988, were labelled
numerically. Table 1 shows ages, graptolite zones, and section des-
ignation equivalents for the sections sampled in the two field seasons.

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 25

Only sections E (#10) and F (#8) were long and more-or-less con-
tinuous sections, and yielded nodules throughout. Because of the
difficulty in making precise stratigraphic correlations between the
collections of 1988 and of 1990, faunas collected in the two years
are listed and designated separately. This is justified because some
species recovered in 1990 were not recovered from nodules collected
in 1988, and vice versa; even within the same bed, different nodules
may yield distinct faunas. Therefore, for example, a sample collected
from the 41 m level in section E in 1990 is designated “SB E41”,
whereas a sample collected in the same place in 1988 is designated
“SBC 10B”.

Correlations between the section E of 1990 and section 10 of 1988
are approximately as follows: 10OA = E 20 m; 10B = E 28 m; 10C
= E 49 m; 10D and 10D? = E 68 m; and 10OE = E 85 m.

The following collection listings proceed from oldest to youngest.
Measurements are in meters above a designated section base.

Section A (of 1990) did not yield any nodular faunas, but flattened
specimens of Lobograptus progenitor Urbanek, 1966 were recovered.

Section 5 (of 1988) yielded Pseudomonoclimacis dalejensis (Bou-
éek, 1936).

Age: Ludlow, Lobograptus progenitor Zone.

Section B (of 1990) yielded the following:

2 m: Holoretiolites mancki (Miinch, 1931), Pseudomonoclimacis da-
lejensis (Bouéek, 1936).

3 m: Holoretiolites mancki.

5 m: Holoretiolites mancki, Pseudomonoclimacis dalejensis.

27 m: Pseudomonoclimacis dalejensis.

Section SBC 4 (of 1988) yielded the following species, preserved
in flattened form:

7 m: Bohemograptus bohemicus bohemicus (Barrande, 1850), Ho-
loretiolites mancki, Lobograptus progenitor Urbanek, 1966, Mon-
ograptus ceratus Lenz, 1988a, Plectograptus macilentus (TOrn-
quist, 1887), Pseudomonoclimacis dalejensis.

10 m: Bohemograptus bohemicus bohemicus, Pseudomonoclimacis
dalejensis.

15 m: ?Neolobograptus sp., Pseudomonoclimacis dalejensis.

Age: Ludlow, Lobograptus progenitor Zone.

Section D (of 1990) yielded the following:

10 m: Saetograptus fritschi linearis (Boucek, 1936) [flattened on
shale].

75 m: Pristiograptus sp., Saetograptus fritschi linearis. {nodule}

75 m: Bohemograptus bohemicus tenuis (Boucek, 1936), Monograp-
tus ceratus. [flattened on shale]

Section 7 (of 1988) yielded the following:

7A: Bohemograptus bohemicus tenuis, Monograptus ceratus, Pseu-
domonoclimacis dalejensis, Saetograptus fritschi linearis.

7B: Saetograptus fritschi linearis.

7C: Pseudomonoclimacis dalejensis, Saetograptus fritschi linearis.
Age: Ludlow, Saetograptus fritschi linearis Zone.

Section E (of 1990) yielded the following:

0 m: Cyrtograptus sp., Paraplectograptus eiseli, Paraplectograptus
praemacilentus, Plectograptus (Sokolovograptus) textor (Boucek
and Minch, 1952).

20 m: Cyrtograptus hamatus (Baily, 1861), Paraplectograptus sa-
genus, n. sp.

28 m: Cyrtograptus hamatus, Monograptus priodon (Bronn, 1835),
Paraplectograptus sagenus, Plectograptus (Sokolovograptus?) sp.

32 m: Cyrtograptus hamatus, Monograptus instrenuus Lenz and Mel-
chin, 1991, Monograptus priodon, Paraplectograptus praemaci-
lentus, Paraplectogratpus sagenus, Pristiograptus dubius (Suess,
1851).

41 m: Cyrtograptus hamatus, Cyrtograptus lundgreni Tullberg, 1883?,
Gothograptus marsupium, n. sp., Monograptus instrenuus, Para-
plectograptus sagenus, Nn. sp.

49 m: Gothograptus eisenacki, Gothograptus marsupium, Mono-
graptus instrenuus, Paraplectograptus praemacilentus.

53 m: Cyrtograptus lundgreni?, Gothograptus eisenacki, Gothograp-
tus marsupium, Pristiograptus dubius.

68 m: Agastograptus clathrospinosus, Monograptus instrenuus, Par-
aplectograptus sagenus, Plectograptus (Sokolovograptus?) sp.

85 m: Gothograptus marsupium, Monograptus instrenuus, Pristio-
graptus dubius.

102 m: Cyrtograptus lundgreni?, Gothograptus marsupium, Mono-
graptus instrenuus.

142 m: Agastograptus clathrospinosus (Eisenack, 1951), Pristiograp-
tus dubius, “‘Pristiograptus” ludensis (Murchison [sensu Wood,
1900)).

153 m: Agastograptus clathrospinosus, “Pristiograptus” ludensis,
Pristiograptus sherrardae (Sherwin, 1975).

155 m: “‘Pristiograptus” ludensis.

Age: Late Wenlock, Cyrtograptus lundgreni-Monograptus testis
Zone [from 0 m through 102 m], and latest Wenlock, “*Pristiograp-
tus” ludensis Zone [from the 142 m, 153 m, and 155 m samples].

Section 10 (of 1988), and a nearby small isolated outcrop [sample
10D?; approximately coeval with sample 10D] yielded the following:

10A: Cyrtograptus hamatus, Paraplectograptus sagenus.

10B: Gothograptus eisenacki, ?Gothograptus sp., Paraplectograptus
sagenus, Spinograptus nevadensis (Berry and Murphy, 1975).

10C: Cyrtograptus lundgreni, Gothograptus eisenacki, Gothograptus
marsupium, Monograptus testis Tullberg, 1883, Paraplectograptus
praemacilentus, Paraplectograptus sagenus, Spinograptus apoxys,
n. sp., Spinograptus nevadensis.

10D: Gothograptus eisenacki, Gothograptus marsupium, Monograp-
tus testis, Paraplectograptus eiseli, Paraplectograptus praemaci-
lentus, Paraplectograptus sagenus, Spinograptus apoxys, Spino-
graptus nevadensis.

10D?: Cyrtograptus cf. C. lundgreni, Gothograptus eisenacki, Goth-
ograptus marsupium, Monograptus testis, Spinograptus nevaden-
SIS.

10E: Spinograptus nevadensis.
Age: Late Wenlock, Cyrtograptus lundgreni-Monograptus testis

Zone.

Section F of 1990 yielded the following:

3 m: Cyrtograptus hamatus (Baily, 1861), Monograptus instrenuus
Lenz and Melchin, 1991, Monograptus testis Tullberg, 1883, Par-
aplectograptus praemacilentus Bouéek and Minch, 1952, Spino-
graptus apoXxys, N. sp.

22 m: Cyrtograptus lundgreni Tullberg, 1883?, Pristiograptus prae-
macilentus, Spinograptus apoxys.

26 m: Cyrtograptus hamatus.

39 m: Gothograptus chainos, Pristiograptus dubius, * Pristiograptus”
ludensis (Murchison [sensu Wood, 1900])?.

44 m: Agastograptus clathrospinosus (Eisenack, 1951).

57 m: Agastograptus clathrospinosus, ‘*Pristiograptus” ludensis.

62 m: Agastograptus clathrospinosus, “Pristiograptus” ludensis.

68 m2*: Cyrtograptus lundgreni, Monograptus instrenuus, Paraplec-
tograptus praemacilentus, Spinograptus apoxys.

24 Talus sample, almost certainly out of place.

26 BULLETIN 342

288 m: Pseudomonoclimacis dalejensis (Boucek, 1936).

300 m: Monograptus ceratus Lenz, 1988a, Pseudomonoclimacis da-
lejensis.

320 m: Monograptus ceratus, Pseudomonoclimacis dalejensis.

325 m: Saetograptus fritschi linearis (Boucek, 1936).

Age: Late Wenlock, Cyrtograptus lundgreni—Monograptus testis
Zone [from 0 m through 26 mJ]; latest Wenlock, ‘‘Pristiograptus”
ludensis Zone [from 39 m through 62 m, questionably 68 m]; early
Ludlow, Saetograptus fritschi linearis Zone [from 288 m through
350 m].

Section 8 (of 1988) yielded the following:

8A: Gothograptus eisenacki Obut and Sobolevskaya, 1965, Mono-
graptus testis Tullberg, 1883, Paraplectograptus sagenus, N. sp.,
Spinograptus apoxys, N. sp.

8C*: Bohemograptus bohemicus tenuis (Boucek, 1936), Monograp-
tus ceratus, Saetograptus ex gr. chimaera (Barrande, 1850).
8E: Agastograptus clathrospinosus, Colonograptus colonus (Bar-
rande, 1850), Holoretiolities mancki (Minch, 1931).

8F: ?Lobograptus sp.
Age: Late Wenlock, Cyrtograptus lundgreni—Monograptus testis

Zone [8A]; early Ludlow, Lobograptus progenitor Zone [?8C-8E].

Locality 2.—Rookery Creek (field designation MRC). Only a single
graptolite-bearing nodule of relevance to this study was recovered.
It contains abundant Gothograptus eisenacki Obut and Sobolev-
skaya, 1965, as well as lesser numbers of Plectograptus (Sokolovo-
graptus) textor (Boucek and Miinch, 1952), Gothograptus marsu-
plum, n. sp., and Monograptus opimus Lenz and Melchin, 1991.

Age: Late Wenlock, Cyrtograptus lundgreni-Monograptus testis
Zone.

Locality 3.—Unnamed creek west of Cape Manning (field desig-
nation MCM). The single nodule collected by M. J. Melchin yielded
Bohemograptus bohemicus tenuis (Bouéek, 1936), Holoretiolites
mancki (Minch, 1931), Plectograptus macilentus (Térnquist, 1887),
Pseudomonoclimacis dalejensis (Bouéek, 1936).

Age: Early Ludlow, probably Saetograptus fritschi linearis Zone.

Locality 4.—Cape Phillips (field designations, CP and MCP) yield-
ed two collections of relevance to this study:

213-220 m: Cyrtograptus cf. C. gracilis Bouéek, 1931, Cyrtograptus
sp., Monograptus firmus festinolatus Lenz and Melchin, 1991,
Monograptus instrenuus Lenz and Melchin, 1991.

244-250 m: Cyrtograptus sp., Paraplectograptus eiseli (Manck, 1917),
Paraplectograptus praemacilentus, Plectograptus (Sokolovograp-
tus) textor.

Age: Late Wenlock, Cyrtograptus lundgreni-Monograptus testis

Zone.

25 Possibly in part talus.

Locality 5.—Baillie Hamilton Island (field designation BH), yield-
ed two collections relevant to this study:

42 m: Bohemograptus bohemicus bohemicus (Barrande, 1850), Plec-
tograptus macilentus (flattened on shale).

72 m: Lobograptus progenitor Urbanek, 1966, Plectograptus maci-
/entus (flattened on shale).
Age: Ludlow, Lobograptus progenitor Zone.

Locality 6?°.—Cape Sir John Franklin (field designation SJF) yield-
ed the following:

145 m: Agastograptus clathrospinosus (Eisenack, 1951), Pristiograp-
tus dubius (Suess, 1851), ‘‘Pristiograptus” ludensis (Murchison
[sensu Wood, 1900])?

147 m: Bohemograptus bohemicus bohemicus, Saetograptus roemeri
(Barrande, 1850).

148 m: Bohemograptus bohemicus bohemicus, Lobograptus progen-
itor, Saetograptus roemeri, .

149 m: Bohemograptus bohemicus bohemicus, Lobograptus progen-
itor.

154 m: Bohemograptus bohemicus bohemicus, Plectograptus maci-
lentus.

155 m: Agastograptus quadratus, n. sp., Bohemograptus bohemicus
bohemicus.

160 m: Bohemograptus bohemicus bohemicus.

163 m: Balticograptus sp., Bohemograptus bohemicus bohemicus,
Saetograptus roemeri.

166 m: Bohemograptus bohemicus bohemicus, Plectograptus maci-
lentus.

170 m: Bohemograptus bohemicus bohemicus.

172 m: Saetograptus roemeri.

174 m: Bohemograptus bohemicus bohemicus, Plectograptus maci-
lentus, Spinograptus spinosus (Wood, 1900).

Age: Early Ludlow, Lobograptus progenitor Zone [147 m through

174 m].

One additional collection of flattened specimens, not shown on
the index map, is relevant to this study. This is a single collection
from Twilight Creek (76°10'N, 99°10'W), north-central Bathurst Is-
land (see Lenz and Melchin, 1990), yielding: Gothograptus nassa
(Holm, 1890), **Pristiograptus” ludensis, and “*Pristiograptus” sher-
rardae (Sherwin, 1975).

Age: Latest Wenlock, “‘Pristiograptus” ludensis Zone.

*e Locality 6 is important in that it is stratigraphically continuous
and yields a good Ludlow fauna. Only at the 145 m and 155 m
levels, however, were isolated specimens recovered from nodules.
These nodules contained large numbers of two species of plecto-
graptines, one new.

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Zur Gattung Bohemograptus, gen. nov. (Graptoloidea) aus
dem béhmischen und fremden Ludlovium. Casopis narod-
niho Muzea, vol. 3, pp. 133-136.

Graptolite biozones of the Kopanina and Pridoli formations
in the Upper Silurian of central Bohemia. Casopis pro
mineralogii a geologii, vol. 28, pp. 149-167.

Rickards, R. B.

1967.

1983.

1967. The Wenlock and Ludlow succession in the Howgill Fells
(north-west Yorkshire and Westmoreland). Quarterly Jour-
nal of the Geological Society of London, vol. 123, pp.
215-249.

1976. The sequence of Silurian graptolite zones in the British

Isles. Geological Journal, vol. 11, pp. 153-188.
Rickards, R. B., Hutt, J. E., and Berry, W. B. N.

1977. Evolution of the Silurian and Devonian graptoloids. Bul-
letin of the British Museum (Natural History), Geology,
vol. 28, 120 pp.

Rickards, R. B., and Koren, T. N.

1974. Virgellar meshworks and sicular spinosity in Llandovery

graptolites. Geological Magazine, vol. 111, pp. 193-204.

Rigby, J.
1986. A critique of graptolite classification, and a revision of the
suborders Diplograptina and Monograptina, in Hughes, C.
P., and Rickards, R. B. [eds.] Palaeoecology and biostra-
tigraphy of graptolites. Geological Society, Special Publi-
cation No. 20, pp. 1-12.
Rigby, S., and Rickards, R. B.
1990. New evidence for the life habit of graptoloids from physical
modelling. Paleobiology, vol. 15, pp. 402-413.
Salter, J. W.

1852. Description of some graptolites from south of Scotland.
Quarterly Journal of the Geological Society of London,
vol. 8, pp. 388-391.
Sherwin, L.
1975. Silurian graptolites from the Forbes Group, New South
Wales. Records of the Geological Survey of New South
Wales, vol. 16, pp. 227-237.
Suess, E.
1851. Uber béhmische Graptoliten. Naturwissenschaftliche Ab-

handlungen von W. Haidinger, vol. 4, pp. 87-134.
Thorsteinsson, R.
1958. Cornwallis and Little Cornwallis Islands, District of Frank-
lin, Northwest Territories. Geological Survey of Canada,
Memoir 294.
Tornquist, S. L.
1887. Anteckningar om de aldre Paleozoiska Leden i Ostthurin-
gen och Vogtland. Geologiska Féreningens Forhandlingar,
vol. 9, pp. 471-492.
1910. Graptolitologiska bidrag. Tva Cyrtograptus arter fran Thu-
ringen. Geologiska Féreningens Férhandlingar, vol. 32,
pp. 1559-1575.
Tullberg, S. A.

1883. Skanes graptoliter II. Sveriges geologiska Undersokning
Afhandlingar, ser. C, vol. 55, pp. 1-43.
Urbanek, A.
1966. On the morphology and evolution of the Cucullograptinae
(Monograptidae, Graptolithina). Acta Palaeontologica Po-
lonica, vol. 11, pp. 291-544.
Wiman, C.
1896. Uber die Graptoliten. Bulletin of the Geological Institution

of the University of Uppsala, vol. 2, pp. 239-316.
Wood, E. M. R.
1900. The Lower Ludlow formation and its graptolite fauna.
Quarterly Journal of the Geological Society of London,
vol. 56, pp. 415-492.

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

PLATES

29

30 BULLETIN 342

EXPLANATION OF PLATE 1

Figure
1—5:, Plectograptus (Sokolovograptus?) Sp; 22. :icijs.c ecisise cec8) te sla wie ws oon Sw, VE Ae a RISIRVD SHEN BTSIOITO Lele TAPE Te oT ns Toto
Locality 1, sections SB E68 m.
1. Large mature specimen; GSC103976, x20.
2. Immature fragment with well preserved virgula; GSC103977, x31.
3. Mature specimen; GSC103978, x20.
4. Proximal end fragment; GSC103979, x31.
5. Immature specimen with ladder-like walls; GSC103980, x 23.
6=8. Plectograptus (Plectograptus) macilentus\(Tornquist). ........ 25... ccees- «snes sakes eee okies oe eee eee Eee
Locality 1, section SB E68 m.
6. Proximal region; GSC103981, x28.
7. Mid-region of rhabdosome; GSC103982, x 24.
8. Stereopair of proximal region; GSC103983, x28.

13

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE |

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104

PLATE 2

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Figure

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 2

1-8. Plectograptus (Sokolovograptus) textor Boucek and Miinch ....... 0.0.6... 60ers

ihe
. Complete specimen; locality 1, section SB E28 m; GSC103984, x23.

. Stereopair of proximal region; locality 4, section CP700; GSC103985, x35.

. Partial specimen showing thecal characteristics; locality 1, section SBC9, GSC103986, ~ 20.
. Stereopair of incomplete specimen; locality 4, section CP700; GSC103987, x 24.

Large specimen; locality 4, section CP390-400 (Early Wenlock); GSC78449, x40.

Enlargement of thecal walls of GSC103986, x 160.

. Proximal end of GSC103984, «69.
. Incomplete specimen showing thecal profile; locality 4, section CP600; GSC103988, x 20.

31

32 BULLETIN 342
|
EXPLANATION OF PLATE 3
Figure Page
1=9.. Apastograptus clathrospinosus (Eisenack) ~.. 22: <0 .005.00. 5 ce eeee eevee wae cere ee ied oe aie ermal eels lacie eerie oi. eee eee 15

ils

CRON AARYWN

Fragment of a specimen with very large spinoreticuli; locality 1, section SB E142; GSC103989, x24.

Immature specimen with large spinoreticuli and well preserved virgula; locality 1, section SB E142; GSC103990, x21.
Proximal end fragment with large spinoreticuli; locality 1, section SB E68; GSC103991, x 18.

Enlargement of spinoreticulum of GSC103991, x 100.

Enlargement of spinoreticulum of GSC103989, x72.

Mid-region of rhabdosome showing distinct zig-zag nature of the primary clathria; locality 1, section SBC8E; GSC99152, x24.
Rhabdosome fragment with long spinoreticulum; locality 1, section SB E142; GSC103992, x19.

. Spinoreticuli of GSC99150; locality 6, section SJF145, x56.
. Enlargement of spinoreticulum of GSC99150, x 660.

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 3

SLI AVAG
aioe

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 38

EXPLANATION OF PLATE 4
Figure Page
1-7. Agastograptus clathrospinosus (Eisenack) .......... 0... +2 22200000 sees reer esse ster esses sess sss s esses sees ee eee sees 15

Ite

YAWERYWH

Stereopair of GSC99151; locality 6, section SJF145, x20.

Proximal end showing early spinoreticuli; locality 1, section SB E142; GSC103993, x33.

Incomplete specimen with well developed spinoreticuli; locality 1, section SB E142, GSC103994, x17.
Stereopair of immature specimen; locality 6, section SJF145; GSC99153, «35.

. Incomplete specimen; locality 1, section SB E142; GSC103995, x19.

Specimen with long virgula; locality 1, section SB E142; GSC103996, x 19.
Proximal portion of specimen; locality 1, section SB E142, GSC103997, «48.

34

Figure

BULLETIN 342

EXPLANATION OF PLATE 5

1=10:, Agastograptus. quadratus, NEW SPECIES) a6..6< 2 oss 5S cisiwis pie rovers wos enya we crmtoyeve S S)eyalee aac Musiserels @ iste reel eee
Locality 6, section SJF155 (except for #10).

Ile
. Enlargement of proximal end of holotype GSC99173, x40.
. Stereopair, GSC99171, x20.

—_

Holotype specimen, GSC99173, x 16.

Enlargement of spinoreticuli of holotype GSC99173, x 240.
Mid-region of rhabdosome with long virgula; GSC99172, x 18.
Enlargement of spinoreticuli of GSC99172, =x 560.

. Thecal walls and spinoreticuli of GSC99171, x50.

. Stereopair of thecal walls and spinoreticuli of GSC99172, x28.

. Partial specimen, GSC103998, x 16.

. Proximal end of incomplete specimen; locality 6, section SB E142, GSC103999, x48.

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 5

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BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 6

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SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 6

Figure
Se ae YEN Cy OL OPTCDILES MASS) (EA OTN) eee p test <5 ee oe es ees eee oe ese Tena SI eS OR fo MONS Fer eae els a) Peay rie elas atauceiees Pevonarelelteeveterals

1. Mature, broken specimen from Gotland showing well developed thecal hoods; RM67196, x45.

2,3,5. Flattened specimens on shale surfaces from Twilight Creek, Bathurst Island; GSC95976, 95978 and 95977, x14.
Eira COL MOSTUDLUS SP) MIN e tn ene Neo aer oye sss SES avec dae oa SFA ah ero) ONG POUETE. Ha Van'dee eye 'a SrehoN ea] alee tone land foroiokene es ahe ee layslore. 218) vee MeLel Ne Reyste lee Weta sys
Locality 1, section SBC1OB.

4. Stereopair of walls; GSC104000, x40.

6. Specimen showing walls and thecae; GSC99178, x40.

7. Stereopair of specimen with well preserved virgula; GSC99179, x30.

8. Stereopair showing loosely curved virgula; GSC99177, x40.

35

36

Figure

1-12. Gothograptus chainos, new species

BULLETIN 342

EXPLANATION OF PLATE 7

Locality 1, section SB E39.

—

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Proximal end of immature specimen; GSC104001, x38.
Mature specimen with “appendix”; GSC104002, x 18.
Enlargement of appendix of GSC104002, x61.
Enlargement of thecal apertures of GSC104003, x58.
Thecal view of incomplete specimen; GSC104003, x 16.

. Stereopair of holotype; GSC104004, x21.

. Thecal view of mid-region; GSC104005, x21.

. Proximal region; GSC104006, x 32.

. Stereopair of mature specimen; GSC104007, x21.

. Proximal region; GSC104008, x37.

. Proximal region of immature specimen; GSC104009, x 20.

. Enlargement of proximal region of holotype; GSC104004, x47.

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104

ras

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BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 8

Figure

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 8

1-9. Gothograptus eisenacki Obut and Sobolevskaya .....-..-.-- 0000200552 e seen erent

eC eIAwewne

. Stereopair of mature specimen; locality 2, section MRCOS5; GSC99148, x60.
_ Small, near-mature specimen; locality 1, section SBC10D; GSC104011, x 50.

Small immature specimen; locality 1, section SBC10D; GSC99147, x 56.
Distal end of GSC99148, x96.
Mature specimen; locality 1, section SB F68; GSC104012, x27.

. Enlargement of appendix of GSC104012, x93.

Medium-sized, mature specimen; locality 2, section MRCOS5,; GSC104013, x60.
Mature, longer than normal specimen; locality 1, section SB F68; GSC104014, x27.
Fragment of unusually long specimen; locality 2, section MRC05; GSC78440, x40.

3H

38 BULLETIN 342

EXPLANATION OF PLATE 9
Figure Page
1-9. Gorhograptus eisenacki Obut and Sobolevskaya <<... 2.500502 4..40).¢00+0 000s ose net sewoi’ dase casts Jeger 18

1.
. Enlargement of wall of GSC104015, x 139.
. Stereopair of small, immature, but complete specimen; locality 2, section MRCO5; GSC78446, x50.

CRI AH RwWN

Enlargement of clathrial (pustulose) and reticular (seams facing out) lists of GSC104016, x 800.
Mature specimen; locality 1, section SB F68; GSC104017, x 24.

Small, immature but complete specimen: locality 1, section SBC1O0D; GSC99149, x 40.

Small, mature specimen; locality 1, section LL7 (=SB F68); GSC104018, x 40.

. Small, mature specimen; locality 2, section MRCOS5; GSC104016, x80.

Moderately long, mature specimen; locality 1, section LL7 (=SB F68); GSC99146, x 48.

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104

PLATE 9

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SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 10

1-9. Gothograptus marsupium, new species ........--- 2-0. s eect e terete sete ene nese tenses esses esse

1.
. Immature specimen; locality 1, section SB E102; GSC104020, x28.
. Stereopair of mature specimen; locality 1, section SBC1O0D; GSC99175, x 25:

CaN anewWND

Stereopair of complete specimen; locality 1, section 10:3; GSC104019, x 16.

Enlargement of distal end of GSC104019, showing linkage of virgula and clathria, x 160.
Immature specimen (note radiolarian); locality 2, section MRC05; GSC99176, x 24.
Stereopair; locality 1, section SBC 10D; GSC99174, x30.

Stereopair of GSC99174, showing thecal apertures and inner connecting list, x 64.

. Immature specimen; locality 2, section MRC05; GSC104021, x 24.
. Stereopair of immature specimen; locality 1, section SBC10D; GSC104022, x 24.

39

40

Figure

BULLETIN 342

EXPLANATION OF PLATE 11

1=8:. Gothograptus.marsupium, MEW SPECIES « «. . o oo)e.c is: iors 20 cis iaisieis/0 12 a ido avonhe ne a es Blea eel Fie ee eee ke Oe

ile
. Holotype specimen; locality 1, section SB E41; GSC104024, x25.
. Complete specimen; locality 1, section SB E85; GSC104025, x22.
. Complete but immature specimen; locality 1, section SB E85; GSC104026, x22.
. Stereopair of immature specimen; locality 1, section SBC10C; GSC104027, x19.

SNAADMWHKWHN

Complete specimen with long nema; locality 1, section SB E102; GSC104023, x34.

Complete specimen; locality 1, section SBC10:3; GSC104028, x 16.

. Stereopair of small, but complete specimen; locality 1, section SB E85; GSC104029, x22.
. Complete specimen piercing (smaller) Gothograptus eisenacki; locality 1, section SBC10D; GSC104030, x 28.

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE | 1

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BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 12

Figure

1-12. Holoretiolites mancki (Minch)
. Long specimen; locality 1, section SBC4:7; GSC99167, x30.

. Enlargement of “appendix” of GSC99167, «175.

. Stereopair of distal end of GSC99167, x48.

. Specimen without appendix; locality 1, section SBC4:7,; GSC104031, x48.

Enlargement of thecal opening of GSC104031,; x 200 (note thread obscuring part of apertual lip).

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 12

Complete specimen; locality 3, section MCM90Y; GSC104032, x21.

. Incomplete specimen; locality 3, section MCM90Y; GSC104033, x 34.

. Stereopair of immature specimen; locality 1, section SBC4:7; GSC99170, x48.
. Large specimen; locality 1, section SBC4:7; GSC99168, x40.

. Enlargement of appendix of GSC99168, x 280.

. Enlargement of appendix of GSC99169, x 240.

. Complete specimen; locality 1, section SBC4:7; GSC99169, x 30.

4]

42 BULLETIN 342

EXPLANATION OF PLATE 13

Figure Page
1=4:. Paraplectograptus eiseli'(Manck)) ........ se: deseie.s)2je eves 5+ Wieiesehw 1m estcene e cicue! Sere ace cw soseiine lee Lederer HIST eA oes re Leer ove lee teen 21
1. Stereopair of proximal region of a long specimen; locality 1, section SBC1O0D; GSC104034, x35.
2. Specimen with only a weak reticulum; locality 1, section E 0m; GSC104035, x11.
3. Stereopair of well preserved specimen; locality 4, section MCP152.5; GSC 78450, x27.
4. Specimen with clathruim only; locality 1, section EOm; GSC104036, x17.
5-10. Paraplectograptus sp.
Isolated nodule near locality 3; age: probably Late Llandovery or Early Wenlock.
5. Prosicular enlargement from GSC104037, x 171.
Well preserved specimen; GSC104038, x34.
Complete, but immature specimen; GSC104039, x 34.
Proximal end fragment; GSC104037, x65.
. Prosicula of GSC104038, «211.
. Proximal end fragment with well preserved prosicular threads; GSC104040, x63.

SP OND

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 13

PLATE 14

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SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 14

1-6. Paraplectograptus praemacilentus (Boucek ATG ATI Ny saeeae eo nego eneen or OsebalcosupEoe aso comnonupos DoS oD cibopicamnnoDEote

1.

Large, well preserved specimen; locality 2, section MRCO05; GSC78441, x40.
Mature specimen; locality 4, section CP600; GSC104041, x32.
Distal end view of specimen; locality 4, section CP600; GSC104042, x48.

. Stereopair of immature specimen; locality 4, section CP850; GSC104043, x32.
. Stereopair; locality 4, section CP850; GSC104044, x 40.
_ Stereopair of proximal end of immature specimen; locality 1, section SBC10C; GSC104045, x35.

43

44 BULLETIN 342

EXPLANATION OF PLATE 15 |

Figure Page

1=9:. Paraplectograptus sagenus, MEW SPECIES) ~ <.-0)<.25 <0: ss sjete aise in bis wise woe nS Sis 4 sini noes BI Stein eI oie oe oe eles ke ec ie oe ee 225
1. Large, mature specimen; locality 1, section SBC10D; GSC104046, x24. |

. GSC99158; locality 1, section SBCIOA, x 16. |

. GSC99155; locality 1, section SBCIOA, x 16.

. Stereopair; locality 1, section SBC1OA; GSC104047, x25.

Enlargement of lists of GSC99155, x30.

Stereopair of GSC99155, showing details of thecal walls, x 48.

. Stereopair enlargement of proximal end of holotype; locality 1, section SBC10B; GSC104048, x20.

. Stereopair; locality 1, section SBC1OB; GSC99157, x28.

. Stereopair of holotype; GSC104048, = 12.

CSANDNSWN

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 15

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 16

Figure

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 16

1=8) Paraplectograptus sagenus, NEW SPECIES... 2. 6 ee tee et ee mene rete teenie tne teen eens eee ee eeee

Ih
. Stereopair; locality 1, section SBC1OB; GSC99154, x 24.

. Stereopair of immature specimen; locality 1, section SBC10A; GSC104050, x 28.
. Stereopair of mature specimen; locality 1, section SBC10B; GSC104051, x 20.

oN AKaRwWH

Stereopair of immature specimen; locality 1, section SBC10A; GSC104049, x35.

Stereopair of mature specimen; locality 1, section SBC10B; GSC104052, x 22.
Proximal end of immature specimen; locality 1, section SBC10B; GSC104053, x 22.
Thecal wall lists of GSC104050, x 200.

Stereopair of immature specimen; locality 1, section SBC10A; GSC104054, x27.

45

46

Figure

1-7. Spinograptus apoxys, new species
1.

. Enlargement of thecal wall and inner connecting list of holotype; GSC104055, x88.

. Stereopair; locality 1, section SBC1OD; GSC99165, x 15.

. Distal region of fragment showing attachment of virgula to clathrium; locality 1, section SBC10D; GSC104056, x40.

. Stereopair enlargement of thecal walls and inner connecting lists of GSC99165, 80.

. Stereopair enlargement of stomata of holotype; GSC104055, x80.

. Stereopair of GSC99164; locality 1, section SBC10D, x 20.

ND BW tO

BULLETIN 342

EXPLANATION OF PLATE 17

Holotype specimen; locality 1, section SBC1O0C; GSC104055, x 18.

PLATE 17

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BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 18

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SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ 47

EXPLANATION OF PLATE 18

1-7. Spinograptus apoxys, new SPECi€S ....... 2.2... eee eee nner e ene e eee reenter eee ees 23

ie
. Enlargement of distal end of GSC104057, showing attachment of virgula to clathrium, x 38.

YAN ewN

Large specimen; locality 1, section SB F3; GSC104057, = 12.

Nearly complete specimen; locality 1, section SB F3; GSC104058, x11.
Stereopair enlargement of thecal region of GSC99166, showing inner connecting list and sigmoidal processes, x55.
Stereopair enlargement of GSC104057, showing sigmoidal processes, = 100.

. Enlargement of aperture of GSC99166, showing sigmoidal processes and inner connecting list, x 55.
. Mature specimen; locality 1, section SBC10D; GSC99166, x15.

48

Figure

BULLETIN 342

EXPLANATION OF PLATE 19

1-6. Spinograptus nevadensis|(Berry and) Murphy). .-2+---4-4-2.. 2.2 soe eee eee ee eee 23

IE
. Stereopair of mid-region of rhabdosome; locality 1, section SBC3; GSC104059, x 18.

DAnkwn

Stereopair of well preserved specimen with long virgula; locality 1, section SBC10E; GSC99161, x22.

Stereopair enlargement of thecal wall of GSC99161, x40.

. Stereopair of mid-region of rhabdosome; locality 1, section SBC3; GSC104060, x20.
. Stereopair of immature specimen; locality 1, section SBC1OE; GSC99159, x25.
. Enlargement of thecal list and spine of GSC104060, x56.

PLATE 19

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104

BULLETINS OF AMERICAN PALEONTOLOGY, VOLUME 104 PLATE 20

Figure

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ

EXPLANATION OF PLATE 20

1-7. Spinograptus nevadensis (Berry and Murphy) .........--- +--+ --- 22-2000 serene ec se esses eet ee tees ness s ests nesses eens

Stereopair of mid-region with well preserved thecal walls and spines; locality 1, section SBC1OE; GSC99162, x 18.
Enlargement of thecal wall and apertures of GSC99162, x56.

Stereopair of mid-region; locality 1, section SBC3, GSC99160, x 20.

Enlargement of thecal “hood” and spine base of GSC99162, x 380.

. Enlargement of thecal wall of GSC104059, x80.
. Stereopair of thecal walls of GSC104061, 45.
. Mid-region of rhabdosome; locality 1, section SBC10C; GSC104061, x 24.

49

50 BULLETIN 342

INDEX
Agastograptus Obut and Zaslavskaya, 1983 ............0....... 7,8,11 eisenacki
clathrospinosus .... 8,15,25,26,32,33 Gothograptusre tcc ee ee 18
QUAATALUS Soren te aoc ged 16,26,34 Eisenack; 93'S 25 .fec soise nck scoccer eee 7,20,27
Agastograptus balticus (Eisenack, 1951) .........00..cc0ccccc0eeceeeeee 16 Eisenackas195ilieeeeeee: ~ 8511125155116: 20;21625=27)
Agastograptus munchi Obut and Zaslavskaya, 1983 .............. 19 Elles; F90Qcetes once oviee ses ode ee 8,27
Agastograptus nevadensis (Berry and Murphy, 1975), Obut and Zas- Ellesiand: Wood'1908)exeessceene eee 17,24,27
lavskayas N98 Grea: waco cree sc-cee-2cs tenons eee Ce eae 23
ARASLORTADLUS | QUAGKALUSIDASD) . 2-0. <csteec eee 16,26,34 Frech,. 189 7igcstterc haces sees 2d ee 12,16,18,19,27
Agastograptus robustus Obut and Zaslavskaya, 1983 ......... 15,16
AN COLA Gr renc career asec tee ate neeetasee ives se cee ee ee 10,14-16 SEINUZIANUS, WRELIONILES pee acncseceenee eae ce nee ee ee 6
apoxys, Germany: «5.55. gersensicersaco.esesisseestaoeien eee 7,20
SDINOGTADEUS Sac ace een nee a so RRC 23 Gortant, 1922)... novi eect eee 8,27
Gothograptus Frech, 1897 .. .... 12,16,19,20
BailliesyHamiltonsisland pees cece eee 24,26 CRAINOS Soca hoes oe eee 8,17,36
Bail yqillS Gita oeere eae eee... > ee nee 8,25,26 eisenacki 6-8,12,18,19,25,26,37,38
Balticograptus Boucek and Miinch, 1952 ................06c...0002. 8,11 QTSUDIUM sec concazers cee ee 8,18,19,25,26,39,40
BarranGe sil 8S irncscvsc tecece reeves sek ncced eee eee 7,12,26 nassa 7,8,16,17,19,26,35,37,38
Bates: and gairks W918 ieee neces eens sae scans snc ee eee eee seeceee ee 6,26 SDs seacates cos cewesegeesausenecb eas scecwenenesceeto: eee ae eee eee 19
Batesjandikirksil\9 S4mesee ee. ee see 051026 Gothograptus intermedius Boucek and Miinch, 1952 ............. 19
BatestandakarksallO8 Gy seer eaten. ae eee 6,26 Gothograptus kozlowskii Kozlowska-Dawidziuk, 1990 ........... 19
Bathurstelsland gece are eee 2 ee re 15 Gothograptus pseudospinosus (Eisenack, 1951) ............206...--- 19
Berry and Murphy, 1975 6,15-17,23,25,26 Gothograptus tenuis Obut and Sobolevskaya, 1965 ............... 21
Bohemograptus bohemicus bohemicus (Barrande, 1850) .. 8,25,26 Gothograptus?: Spi. tessesetcseicieesos coe ee 19,35
Bohemograptus bohemicus tenuis (Boucek, 1936) .............. 25,26 Gotland: ‘Sweden 5.2.22 :-se5 ccsccsseee ees 16,17
Bohemograptus bohemicus tenuis ZONE ..........60000000000ee0eeeeeeeee 8 Gotland) .22.32cs3.8224 sie seioes Biss Soe 7
‘Bohemozraptus)Pribyll9 Ginette cee ee ee 8 Great Britain ..c.2 1: so<cccsecceecsoves een ke Reston ne 8
Boucek:yill9/3ilete ot one seestwonsc cons teses oreo sce nett s soar ces ene 22,26
BOucekwli9 3 Gyteccc nesters ne ened ee occ eee eee ee 8,25,26 Holm, 1890) 223-322. ee eee 7,16,17,19,26,27
Boucekgand Miinch'y1'944 passe... eee ee 7211222327 Holoretiolites (Holoretiolites) Eisenack, 1951 ......... 8,11,12,20,21
Boucek and Miinch, 1952 .............0...... 8,10-15,17,19-23,25,27 INGNEKE saa.e cree uceheee ne eee ee 8,20,25,26,41
BrOmM ali 835 poses ce ece ce ste score eens os <tact e eeeet eee ee 3 Holoretiolites (Holoretiolites) simplex (Eisenack, 1935) .......... 20
Bulman, 1938 ... Hopkinsoniand!apworthil/875icsesesee cee ee 13,27
Bulman, 1970 Fiundt,. 1924). oc.2:...vsecesaas svasseoeeseven: eo ee D127,
Cape Manning inner connecting lists E2223)
GapelPhillipspersccccsce osccrces neo eere nee ace 5,6,14,21,24,26 inter pleural lists: :..5....c0s.. secs 12223)
CaperSinsJobne bran kines ese serre eee eee re, 24,26
chainos, Jackson;\Lenziand Pedder; 1978s eee 6,14,27
GOLROSTADLUS Aone Moe esa ee eet as cee oe ee ee 17 Jaeger, 1986
Clathriayerr tre cetccnccsescce cc teverr eet eeies 11,13,14,16-18,20,22-24 Jaeger, 1990
clathrospinosus,
A SASLOSTADLUS iecncascaen ne trea see secencceeieeeee eee 8,15,25,26,32,33 Kirk, 1973
Colonograptus colonus (Barrande, 1850) ............6...000cec0000000 26 Kirk, 1990

Cornwallis Island
COLON Asc ceseerceseeon
Crowther, 1981 6,27
Cyrtograptus centrifugus- Cyrtograptus insectus Zone .............. 8
Cyrtograptus cf. gracilis Boucek, 1931 ..............ceeccccsececeeeee
Cyrtograptus hamatus (Baily, 1861) .......0.....00.c.ccecceceeeeeeeee
Cyrtograptus kolobus Lenz and Melchin, 1991 ...
Cyrtograptus lundgreni Tullberg, 1883 .........0........000ccccccee0-
Cyrtograptus lundgreni- Monograptus testis Zone
Cyrtograptus multiramis Tornquist, 1910 .............0ecc cc eeec cece eee
Cyrtograptus perneri- Monograptus opimus Zone
Cyrtograptus preclarus Lenz, 1988D ...............c00ceceeeceeee eS:
Cyrtograptus pseudomancki Lenz and Melchin, 1991 .............. 8
Cyrtograptus radians Térnquist, 1887
GYrtORTADIUS SD ssee tesa ee eeeee
Czechoslovakia

6,24

eiseli
PATADICCLORTADLUS Reenter eee ce eee 21

Mapworth) 1873 sccscdscshece ses wocteestecceec vee eee 13,27
Lenz, 1978
Lenz, 1998a

8,25-27

aadeeaee 8,27
8,9,27
RenziandiMelchiny l9Siaie....ces-cc seen ee 5,6,10, 13,18,23,27
Menz;andyMelichin 9 8i//be--.cssceneeeee eee 5,6,12,17,20,27
enz,andiMelchinsli99 0. -seerere see eee eee ee 8,24,26,27
enziangyMel chins) 9.9 lie... sesso ese eee eee one 8,9,25-27
TEODOR ADLUSTISD sh Rateesec se ocwssee oer e ee 26
Lobograptus progenitor Urbanek, 1966 ...........0c.....c.-00eeee 25,26
Lobograptus progenitor Zone’ eeceee eee ee 8
macilentus,
Plectograptus|(Plectograptus) en ee 13
mancki,

Holoretiolites|(Holoretiolites) 20 ee 20

SILURIAN PLECTOGRAPTINE GRAPTOLITES: LENZ Sil

marsupium,

GOtROBTAPLUS ..2..:--2---50-0snevesvasesesccscnncecectecsnecncnsesenessesescs 18
Manck, 1917 12,20,21,26,27
INGE, TORO) Se ss sGencaoosdeecosa anon ausasoacDacDonondoaspocenasEacoahob3 24,27
Melchin and Mitchell, 1991 .............--...seecesceecereeceeeeeees 10,27
II TCHE LIMO Slim sseseceacecsnseescses esse ectunsaseceseseosseesqss=ssasceas 10,27
Moberg and Térnquist, 1909 ..............::eeeeeeeeees W1=13315:20527
Monograptus ceratus Lenz, 19888 ...........220000ereeerererees 8,25,26
Monograptus cf. flexilis (Elles, 1900) .............:2:222seeeeeessseeeees 8
Monograptus firmus festinolatus Lenz and Melchin, HOON! meee. 26
Monograptus flemingii (Salter, 1852) ...........::::sceeeeeeeeeeeeeeeeees 8
Monograptus instrenuus Lenz and Melchin, MOOG seeieaccs 8,25,26
Monograptus instrenuus- Cyrtograptus kolobus Zone ........--+.++. 8
Monograptus opimus Lenz and Melchin, 1991 .................+++ 26
Monograptus priodon (Bronn, 1835) ..........::::seeeeeeeeeeeeeeee tees 25

Monograptus testis Tullberg, 1883
Mtn GHSpOS Mice ssstserceterssscoersasetesseasece sence

nassa,

(GOTROPTADEUS mes eerersee ev secwecececeasescccsenr= sweressesecesontcentnaese== 17
NASSA, GOtHOZrAPtUS .......62.c0eeeseveeee ees 7,8,16,17,19,26,35,37,38
Neodiversograptus nilssoni ZONE ..........:::0.0ceeeeeeeeeeeeeesee eens ees iL}
Neolobograptus? SDP. .......:.::sscccccecccceceeeneneenneeseeeeeeseeeseeeeneees 25
nevadensis,

Spinograptus
Nevada *:..22-..:.-.-.

MOCUIES eeeeeseesorectscstes se acc tenes

Obut and Sobolevskaya, 1965 ...................- TAZAS-19321-25:27
Obut and Zaslavskaya, 1976 ................5 7,10,11,13-15,20,23,28
Obut and Zaslavskaya, 1983 ..............c:seceeeeeeeee tees 16,21,24,28
Obut and Zaslavskaya, 1986 .................00seseeeeeee ees 16,23,24,28
“Orthograptus”’ obuti Rickards and Koren, 1974 ...............-+- 10
Paraplectograptus Pribyl, 1948, ..............:::05 8,10-13,16,21,42

CEG ED ecb SoBe SEE RSPR SoCo e EE SEER HOR CoE OCE EEE ECE 12,21,22,25,26

PDRGCINGCHEMIUS eecctna ts stectean soesee ene tnnee cases tere 12,21,22,25,43

Sagenus 12,21,22,25,26,44,45

SDA eter n set ceccsseetocceeedesccecoecasececnenesseecteicuserscnn= sesrenene 22
Paraplectograptus eiseli (Manck, 1917) ..............- 12,21,22,25,26
Paraplectograptus praemacilentus Boucek and Minch, 1952 ........

OSCE SHEE SEPOL HERE Ince CEECOEETE CERT BE ee oan sacnes 12,21,22,25,43
Paraplectograptus Sagenus N. SP. ........--++6+++ 12,21,22,25,26,44,45
Paraplectograptus sp. A ...

Paskevicius, 1974 ........... Me

PetalOgraptids: <cececc--222:.-ccccsnanaceeesereceereccnsessesscessosseoccesreres=

Plectograptinae Boucek and Miinch, 1952 .................2:::02 13
Plectograptus Moberg and Toérnquist, 1909 ... 11-13,20,22
Plectograptus lejskoviensis Boucek, 1931 ..........::::.:2:sesseseees 22
Plectograptus (Plectograptus) Moberg and Térnquist, 1909 .... 13
PPLCIGLICTILUS Pretec occa de cos vas seas tue ae oe Se a Oe ass ogen st sous tees 8,13,16,26,30
Plectograptus (Plectograptus) macilentus (T6rnquist, 1887) ..........
SEA OR GO EEA SHE RBA E ROS DOREO DEE RDC ERLE Cee EDO TDARO DORR EROS 8,13,16,26,30
Plectograptus (Sokolovograptus) Obut and Zaslavskaya, NO TGs. o23
bist aH RE CELT COE ESTEE SEED TEP AERPET EO oe 8,10,15,25

WB TP cba BOCEERB DEEPER HEE SEO CDEC Cd CE ee Oe EEE OONOEEES 14,15,25,26,31

Gye, auasakeescepeocn’ beononcdadaagd0000 sBEAR ao sgaHo pS odEoacaacoa pO enaRgpCoochdEe 14
Plectograptus (Sokolovograptus) parens (Obut and Zaslavskaya, 1976)

Seca cS OTB CS ESTADE ODS EB LEE EAE SSSBe-D ACCRUED Rac cone Cr EO Tico ESTECEL 13
Plectograptus (Sokolovograptus) SP. ........:+00.0000000sssseeeeees 14,30
Plectograptus (Sokolovograptus) textor Boucek and Minch, 1952

Pe eee eae esa can eee aee Sack Soc tdacnssceetereesssestoceesses 14,15,25,26,31
Plectograptus? bouceki Rickards, 1967 ...........:-..:10s1eee 10,14
pleiralilistsiesccce-oseseesscessevesccenss=s<s.cancasecerecnctscecrass-sssess-0-e= 11
ROMAN pecs ne oor eore re aeanes cos acer eee te ne erases sseciss de ceavere daceaseeiencss: 18

Post-coronalOrifices 2:.:.cc-cverseceee see oeecasrace 10,12,13,15,18,21-23
praemacilentus,

IRAN ApleClORTADUUS cpcascesscessecscnesstesnee ens coesiansace cecesseeoen dnc 21
Pribyl, 1948 8,10-12,23,28
Pribyl, 1967 8,28
Pribyl, 1983 8,9,28
Pristiograptus dubius (Suess, 1851) .........-...2--00eee0eeee neces 25,26
Pristiograptus meneghini (Gortani, 1922) ...............:00eceeeeseeeee 8
“Pristiograptus”’ ludensis (Murchison [sensu Wood, 1900]) ..........

eed sac ou seadlea outs dt ste oe ds SUSE es gOCa Suse psaeesaUs cess os 8,25,26
MPTISHOPTADIUS a LUACNSIS) LODE ce. ..c0.soc-eocece eee avecessceneesseoeeere 8
“Pristiograptus”’ praedeubeli (Jaeger, 1990) ..............00eeeeeee tees 8
“Pristiograptus”’ sherrardae (Sherwin, 1975) ..........-....0+ 8,25,26
prosicula 21
Pseudomonoclimacis dalejensis (Boucek, 1936) ...............--+- 8,25
Pseudoplectograptus Obut and Zaslavskaya, 1983 ................. 21
Pseudoplegmatograptus Pribyl, 1948 ................:6ese000ee 12513523
Pseudoretiolites Boucek and Miinch, 19944 ..................0..5- 7,23
quadratus,

ABASLOSTAPLUS! vincawseseoeccosssessarasesaceceserseeceaeesececns>ssseasmsr= 15
TELICUIUM eae cece serene ean eae ee oe eaeeeeneeseoease 13,15-18,20,21
Retiolites (Gothograptus) spinosus Wood, 1900 ......-.---....000 22
Retiolites'Barrande; 1850! ..--.-2:...-.c<c.<--c-s0-esesereeee eases 6,7,10,13
IREtiolitesveiseli Manck-wl OlU/m. sseesesscersccesseeceeneessaseemnerecescr= 20
Retiolites mancki Miinch, 1931 ..............0.0.ceceeceeseesesceceeenees 20
Retiolites nevadensis Berry and Murphy, 1975 ................. 15,23
Retiolites tenuis Eisenack, 1951 ..............2:se0ececeeeeeeeeee seers 21,22
Retiolites wimani Eisenack, 1951 ..........2..2:ccceeceeeeeeeeeeee tenes 16
Ruackards L9G) cokccss. cece cseccrcceece tavoc sce erscctneescsecaesesscees 10,14,28
Rickards lO Gie.cecwssseacecssee sees eeecee. cecnesecscccaceseeeree eee 8,9,28
Rickards, Hutt and Berry, 1977 ...........5...0...sscssseoeeeoeeeees 10,28
Rickards and Koren, 1974
Rigby, OS Girecse: -seeec cece aceneees crate sceeeeseanensna- see nwanmesmcnessces
Rigby and Rickards, 1990
Rookery (Creek: (iecccc.csesesscsoessccccensssecrrmers-c-eascssernnemess
Saetograptus cf. chimaera (Barrande, 1850) ..........-....:.60.088 26
Saetograptus fritschi linearis (Boucek, 1936) ...............-+ 8,25,26
Saetograptus fritschi linearis ZONE ..........-..::.000eeeeeeeeeeeeeeeeeeees 8
Saetograptus roemeri (Barrande, 1850) ..............::::::sseeeeeseeee 26
sagenus,

IParaplectOorapiusimee ware eececcecees cece tenet esscnarcescontee sacar mera 22
Salterwli8S20cc-cceccccsstcecscr snc sec er oreseteee se eesestenessencrsces aes 8,28
Sherwin, 1975
Siberia fe
SigMOidalistruCture) noc... ec-cs seco ess can sceansecoesssecuetenacenseesan= 11523:
Snowblindi@reekyccccessccvee-ce see oancconcnscesucssocsceteoseee 6,7,17,24,25
Sokolovograptus Obut and Zaslavskaya, 1976 ........... 7,13,14,20
SDINICS ceases seis cc cescaece eres ston sccasesssacscuusesssersnensscssecrscwosconoress 23
Spinograptus Boucek and Miinch, 1952 ..............-... 8,11,15,22

apoxys 12,23-26,46,47

nevadensis 15,24,25,48,49
SPiNOQraPtUS ADOXYS MT. SP. .......ceecceeceeeceeeceneeees 12,23-26,46,47
Spinograptus cf. SpinOSUS WOO .........000.ccesscecnesernescecnesecnees 16
Spinograptus nevadensis (Berry and Murphy, 1975) ..............0.00

Ee PERE aa ee ECROrtE C Coe ner EOCECE 15,24,25,48,49
Spinograptus spinosus (Wood, 1900) .............-....++ 8,16,23,24,26
SPINOLEtICULieeesceeseeces once eee seeeecSasens sesecesesccuseerccssrece ene 11,15,16
Storm ataye cents reece ites encens comton sconce nace raccraserennamecsencecnsessee 23
Stomatograptus Tullberg, 1883. ...............-.eec0eeeeeeee es 7,12,13,23

Sta|ess 1S Sie ee eee crear eee re Der eee connec ereesssse DOS LO320

52 BULLETIN 342

PAINT PRUSSIA A Pee ce = secelassntstatoeeesisecsnoucchiacienccegmert eee some cemetone 18
textor,

Plectograptus (Sokolovograptus) .............csecceseceeeceneeeeeeees 14
Mh orsteinsson el 95 Sie eee ecece ences §,21,24,28
Toérnquist, 1887 ..... 8,13,16,25,26,28
MOM Quist ol! 9! Oss sceceacceesee cco seeee: Soe se ee ee eee coee te eeeee 8,28
Mullberg.1'883) sessci foe. oe ee 7,12,23,25,26,28
Mwilight: Creek: .-. sbscetese ss soece se see scostee cess sascsaoneet soos sveceseeeees 26
Wnited’ Kingdoms =. .: cetera... 3 s.c.cenocenes sp secce cee eess seers cacasc ver 22

Wrbaneksyl'9 6 Oi <sasseesea ne. dac5.< co seocten tenes aeeaneeee tees 8,26,28

Var gulal..co Sct bsecieseecnsscmensectdeseeweteeeh eee eomeere ste 11,13,16,17-22
Wimlans 1189.6) boos te vcswossjocteauwsneettesstaneeser ce: cASree eee aon 7,28
Wood A900 neocon ee ohaeec oscars ce seen Pace eee 8,24-26,28
ZONA NAMES wee seeder sees cee soso e See wees e ee 8

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