aH

| . * pa aX Postilla Number 229 30 January 2004

Phylogenetic revision of Leptodesma (Leiopteria) (Devonian: Bivalvia)

Alycia L. Rode

CIRRARIES

Peabody Museum of Natural History - Yale University - New Haven, Connecticut

Postilla

Curatorial Editor-in-Chief Jacques Gauthier

Executive Editor Lawrence F. Gall

Publications Editor Rosemary Volpe

Publications Assistant Joyce Gherlone

Published at irregular but frequent intervals since 1950, Postilla presents short papers based on orig- inal scientific research by Museum staff and research associates, and their colleagues, in the natural science disciplines represented by the collections of the Yale Peabody Museum’s curatorial divisions.

All manuscript submissions are sent out for external peer review by one or more referees, as well as being reviewed internally at the Yale Peabody Museum by the Executive Editor in consultation with the Curatorial Editor-in-Chief and one or more members of the appropriate curatorial divi- sion. Interested authors should contact the Executive Editor at the address below before submit- ting manuscripts.

Other series published by the Yale Peabody Museum are the Bulletin of the Peabody Museum of Nat- ural History and the Yale University Publications in Anthropology. A complete list of titles, availability and ordering information, along with submission guidelines for contributors, can be obtained from the Yale Peabody Museum website at http://www.peabody.yale.edu/ or requested from the Publica- tions Office at the address below.

Address correspondence to:

Publications Office Peabody Museum of Natural History Yale University

170 Whitney Avenue Phone: (203) 432-3786 P.O. Box 208118 Fax: (203) 432-5872 New Haven, CT 06520-8118 USA E-mail: peabody.publications@yale.edu

No part of this book, except brief quotations by reviewers, may be used or reproduced in any form or media, electronic or mechanical (including photocopying, recording, or by any information storage and retrieval system), without the written permission of the Peabody Museum of Natural History, Yale University, New Haven, Connecticut, U.S.A.

ISSN 0079-4295 ISBN 0-912532-65-3

Printed in the U.S.A.

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

Phylogenetic revision of Leptodesma (Leiopteria) (Devonian: Bivalvia)

Alycia L. Rode University of Kansas

(Received 3 February 2003; revised and accepted 2 July 2003)

Abstract

The phylogenetic relationships of Middle and Late Devonian species of the sub- genus Leptodesma (Leiopteria) Hall 1883 are examined cladistically and a taxonomic revision of the subgenus is proposed. Six taxa previously afforded species rank are synonymized with Lep- todesma (Leiopteria) laevis (Hall 1843). One new species, Leptodesma (Leiopteria) accranus, is described from the Lower to Middle Devonian of Ghana. Biogeo- graphic analysis of the subgenus reveals less vicariant speciation than speciation associated with range expansion and dispersal. This pattern has been observed in trilobites and phyllocarid crustaceans and may represent a general pattern dur- ing the Middle and Late Devonian. Exten- sive range expansion may have played a role in governing biodiversity dynamics before and during the Late Devonian biodiversity crisis.

Postilla 229 - 30 January 2004

Keywords

Phylogeny, biogeography, Devonian, North America, pterinoid, bivalve, specia- tion, extinction.

Abbreviations

AMNH American Museum of Natural History

MPM _ Milwaukee Public Museum

NYSM_ New York State Museum

PRI Paleontological Research Institution

USNM_ Smithsonian Institution

UMMP University of Michigan

Museum of Paleontology YPM Yale Peabody Museum Introduction

Leptodesma (Leiopteria) Hall 1883 is a species-rich and cosmopolitan subgenus that occurs from the Middle Silurian through the Permian. Its maximal diver- sity was during the Middle and Late De- vonian and the number of species de-

2 Postilla 229

Phylogenetic revision of Leptodesma

Figure 1

Location of morphological measurements illustrated on Leptodesma (Leiopteria) ausablensis (UMMP 38114). Abbreviations: aw, length of anterior wing; d, distance from hingeline to inflection of pos- terior embayment; e, angle of posterior wing extension; h, shell height measured perpendicular to hingeline; hl, length of hingeline; md, maximum shell dimension or greatest oblique length;

o, angle of obliquity; pw, length of posterior wing; u, posterior umbonal angle.

scribed from strata of this age exceeds the total subsequent late Paleozoic diversity of the subgenus. While several studies have revised aspects of its taxonomy (for exam- ple, Ehlers and Wright 1959; McAlester 1962), no comprehensive taxonomic revi- sion of Devonian Leptodesma (Leiopteria) has been undertaken previously. This paper presents a phylogenetic analysis of Middle and Late Devonian Leptodesma (Leiopteria), primarily from North Amer- ica, to assess species validity, taxonomy,

and evolution of this subgenus.

Although Hall (1883) assigned species to L. (Letopteria) in his Paleontology of New York, a detailed diagnosis of the genus was published in the First Annual Report of the New York State Geologist, and included bivalves with oblique, aviculoid shells, an auriculate anterior extremity, a large posterior wing, and a lack of radial ornament (Hall 1884a). This description was later revised by Spriesterbach (in Spriesterbach and Fuchs 1909) to include

Phylogenetic revision of Leptodesma

details of the musculature and hinge teeth, morphological features not observ- able on Hall’s specimens. Spriesterbach also rejected the inclusion of many Euro- pean species previously placed within L. (Leiopteria) by Frech (1891) and other authors, and supported assignment of those species to other pterioid genera. Williams and Breger (1916) provided a comprehensive review of the status of the genus and included North American and European species.

Newell and La Rocque (1969) revised the taxonomic position of L. (Leiopteria) by placing it as a subgenus within the genus Leptodesma, as the sister to L. (Lep- todesma). The primary distinguishing feature between the subgenera was con- sidered to be whether the anterior auricle was rounded, as in L. (Leiopteria), or acuminate, as in L. (Leptodesma). Recent analyses by Pojeta and others (1986), Bradshaw (1999), and Boyd and Newell (2001) have continued the subgeneric designation of L. (Leiopteria) as a valid taxon, and it is used that way in this paper. McAlester (1962) published a com- prehensive revision of the Chemung bi- valves of New York State and expressed doubts about the validity of Hall’s (1883, 1884a, 1884b) species of L. (Leiopteria). McAlester (1962) suggested that many of the Middle Devonian species were merely subjective synonyms, a result confirmed to some extent here.

This paper presents the first phyloge- netic revision of L. (Leiopteria), although various authors have indicated the need for such a revision (McAlester 1962; Po- jeta and others 1986; Boyd and Newell 2001). The phylogeny derived here is also used to examine biogeographic patterns

Postilla 229 3

of North American L. (Leiopteria) during the Middle and Late Devonian.

Phylogenetic Analysis

Taxa analyzed

Specimens representing 22 Devonian species of Leptodesma, mostly L. (Leiopte- ria), were analyzed. All species known from the Middle and Upper Devonian and several Lower Devonian species from North America (those for which sufficient morphological information exists) were included in the phylogenetic analysis. Because the focus of the analysis was determination of evolutionary and biogeographic patterns during the Middle and Upper Devonian, most species of L. (Leiopteria) from older and younger strata were excluded. L. (Leiopteria) marylandica Clarke and Schwartz 1913 was removed from the analysis due to lack of character information for many character states. Leptodesma (Leptodesma) spinerigum (Conrad 1842) was used as the outgroup for character polarization. This taxon was chosen because it is a well-characterized member of L. (Leptodesma), the presumed sister taxon to L. (Letopteria).

Specimens from the collections of the American Museum of Natural History, Milwaukee Public Museum, New York State Museum, Paleontological Research Institution, Smithsonian Institution, University of Michigan Museum of Pale- ontology and Yale Peabody Museum were examined.

Characters and character states

Parsimony analysis was conducted using 27 external characters (see Table 1). Al- though internal characters, such as muscle

4 Postilla 229 Phylogenetic revision of Leptodesma

Table 1

Characters and character states used in the phylogenetic analysis; (0) represents the presumed primitive state. Morphological terminology follows Cox and others (1969) and Boyd and Newell (2001). Location of morphological measurements are illustrated in Figure 1.

General characters: 1. Angle between hingeline and line of demarcation separating posterior wing from body: (0) small (< 26°); (1) large (= 29°). This is comparable to the posterior umbonal angle of Rau (1955).

. Angle between edge of posterior wing and axis of greatest length (obliquity): (0) small (< 16°); (1) large (= 18°). This is comparable to the median umbonal angle of Rau (1955).

bo

3. Overall shape: (0) rectangular, length much longer than width; (1) square, length and width subequal.

4. Size of individual (height perpendicular to hingeline): (0) small (< 23 mm); (1) medium (25 to 38 mm); (2) large (= 42 mm).

5. Relative size of hingeline (length of hingeline/greatest oblique length, measured from beak to posteroventral margin of shell): (0) long (= 0.78); (1) short (< 0.72).

6. Location of maximum valve width: (0) hingeline; (1) lateral to hingeline. 7. Convexity of left valve (umbonal height/umbonal width): (0) high (2 0.25); (1) low (< 0.20).

8. Relative height of umbo: (0) greatly extended above main shell (as in Figure 6.3); (1) moder- ately extended above main shell (as in Figure 5.5).

Anterior features: 9. Shape of auricle: (0) acuminate; (1) rounded. 10. Form of auricle: (0) extended into point; (1) truncated.

11. Relative size of anterior auricle (anterior auricle width/width of entire hingeline): (0) small (< 0.19); (1) large (2 0.21).

12. Septum separating auricle from rest of shell: (0) absent; (1) present. 13. Development of byssal sinus: (0) weakly impressed; (1) deeply impressed.

14. Curve of anterior margin: (0) smooth; (1) undulating.

Posterior features:

15. Relative size of posterior wing (posterior wing width/width of entire hingeline): (0) large (= 0.63); (1) small (< 0.60).

16. Embayment of posterior wing: (0) pronounced; (1) weak.

17. Position of inflection on posterior margin (distance to inflection/valve height): (0) proximal (< 0.20); (1) distal (= 0.23).

18. Angle of posterior wing extension, measured from hingeline to lateral margin of posterior wing at the extremity: (0) small (< 45°) (as in Figure 5.6); (1) large (= 50°) (as in Figure 5.2).

19. Separation of posterior wing from body: (0) demarcated by distinct narrow groove; (1) weakly defined.

Continued.

Phylogenetic revision of Leptodesma

Table 1 continued

Characters of the comarginal ornamentation:

Postilla 229 5

20. Development of concentric growth lamellae: (0) constant over shell; (1) more strongly

developed on posterior portion of shell.

21. Width of growth iamellae: (0) all of equal width; (1) width increases posteriorly.

22. Relief of growth lamellae: (0) low; (1) prominent.

23. Sharpness of growth lamellae: (0) dull; (1) sharp.

24. Growth lamellae: (0) single, distinct rows; (1) lamellose bands; (2) crenulated.

25. Spacing of growth lamellae: (0) irregular; (1) regular.

26. Distribution of growth lamellae: (0) ungrouped; (1) grouped.

27. Radial ornament: (0) absent; (1) weakly developed on right valve; (2) weakly developed on both valves; (3) weakly developed on left valve.

scars, are occasionally useful in species level taxonomy of this group (see Brad- shaw 1999), such character information is only available for a handful of studied species. Location of morphological mea- surements are illustrated in Figure 1; see Table 2 for character coding of analyzed taxa.

Parsimony analysis

Phylogenetic analysis used PAUP* v. 4.0b10 (Swofford 2002). The data set was subjected to a heuristic search using a random addition sequence with 1000 random replications, with tree—bisec- tion—reconnection as the branch swap- ping algorithm. Taxa containing multiple states for a character were treated as poly- morphic for that state. All islands found within the analysis were exhaustively examined, suggesting that additional islands may not exist. All characters were treated as unordered. Characters were optimized with the accelerated transfor- mation (ACCTRAN) option.

Thirteen most-parsimonious trees with a length of 119 steps were recovered.

The strict consensus tree is presented in Figure 2. The consistency index is 0.49 for these trees, and the retention index is 0.56. This observed consistency index exceeds those derived from sets of simi- larly sized matrices constructed from random data (consistency index of 0.16) at the 0.05 level of significance (Klassen and others 1991).

The phylogenetic analysis was also performed following removal of the species synonymized with L. (Leiopteria) laevis (see “Systematic Paleontology” below). The character coding for the revised L. (Leiopteria) laevis analysis was taken from the character optimization of the node at the base of the L. (Leiopteria) laevis clade from the first analysis, using MacClade v. 3.04 (Maddison and Maddi- son 1992). Using the PAUP* branch and bound algorithm, two most-parsimonious trees were recovered. The strict consensus tree is presented in Figure 3. The tree length is 83 steps, consistency index is 0.470, and retention index is 0.488. The consistency index exceeds consistency indices constructed from random data of

6 Postilla 229 Phylogenetic revision of Leptodesma

Leptodesma spinerigum Leiopteria ausablensis Leiopteria peninsularis Leiopteria rafinesquii Leiopteria sayi Leiopteria linguiformis

Leiopteria oweni Leiopteria acutilaris

Leiopteria bigsbyi Leiopteria leai Leiopteria nitida Leiopteria dekayi Leiopteria troosti Leiopteria conradi Leiopteria greeni Leiopteria laevis Leiopteria mitchelli Leiopteria gabbi Leiopteria torreyi Leiopteria auriculata Leiopteria accranus Leiopteria cornelli

Figure 2

Strict consensus of 13 most-parsimonious trees produced from analysis of character data in Table 1, using PAUP* vy. 4.0b10 (Swofford 2002). Tree length is 119 steps. Note the agreement of all trees on the monophyly of the L. (Leiopteria) laevis clade.

similarly sized matrices (consistency index _ ter data is eliminated (Felsenstein 1985;

of 0.27) at the 0.05 level of significance (Klassen and others 1991).

Support for specific nodes within the recovered cladogram was characterized using jackknife analysis to provide infor- mation about the stability of the position of branches when a portion of the charac-

Sanderson 1989). The jackknife analysis was performed using a full heuristic search with 1000 replicates. Groups com- patible with the 50% majority rule con- sensus tree were retained. The confidence values for the nodes duplicated in the jackknife analysis are presented in

Phylogenetic revision of Leptodesma

Figure 3. The jackknife values show strong support for the cladogram recovered in the revised analysis, as all branches were replicated in the jackknife analysis with a high frequency.

Further support for the cladogram was found using the g, statistic, a measure of the skewness of tree length distribu- tions and phylogenetic signal (Hillis 1991; Hillis and Huelsenbeck 1992). The g, value from a distribution of 100,000 trees constructed from this data set is —0.216, markedly stronger than in random data and significant at the p = 0.05 level (Hillis and Huelsenbeck 1992), indicating con- siderable phylogenetic structure within the data.

Results and Taxonomic Implications

Recognition of clades within subgenus Since the reanalysis of the data using the synonymy of L. (Leiopteria) laevis pro- duced greater topological resolution with excellent support, the discussion below centers primarily on the results presented in Figure 3.

Several patterns are apparent from inspection of the strict consensus clado- grams in Figures 2 and 3. First, L. (Leiopte- ria) ausablensis Ehlers and Wright 1959 consistently occupies a basal position while the remaining ingroup species form a well- resolved monophyletic assemblage. Sec- ond, three well-resolved groups occur among the other L. (Leiopteria) species: (1) a clade composed of L. (Leiopteria) leat Hall 1884b, L. (Leiopteria) dekayi Hall 1883, and L. (Leiopteria) troosti Hall 1884b; (2) a clade of L. (Leiopteria) nitida Hall 1883 and L. (Leiopteria) laevis (Hall 1843) (which includes the formerly described

Postilla 229 7

species L. [Leiopteria] laevis, L. [Leiopteria] conradi Hall 1883, L. [Leiopteria] greeni Hall 1883, L. [Leiopteria] mitchelli Hall 1883, L. [Leiopteria] peninsularis La Rocque 1950, L. [Letopteria] rafinesquii Hall 1883, and L. [Leiopteria] sayi Hall 1884b); and (3) a clade comprising L. (Leiopteria) torreyi Hall 1884b, L. (Leiopte- ria) linguiformis Hall 1884b, L. (Leiopteria) owen Hall 1883, L. (Leiopteria) gabbi Hall 1884b, L. (Leiopteria) auriculata Clarke and Schwartz 1913, L. (Letopteria) accranus n. sp., L. (Leiopteria) acutilaris Pohl 1929, and L. (Leiopteria) cornelli Caster 1930. Addi- tionally, the relationship of L. (Leiopteria) bigsbyi to other subclades is uncertain.

Each of these clades is supported by specific character evidence. The mono- phyly of all species of Leiopteria is sup- ported by the rounded and truncated shape of the anterior auricle (characters 9 and 10). L. (Leiopteria) species exclusive of L. (Leiopteria) ausablensis share several additional synapomorphies, including an enlarged angle between the hingeline and the line of demarcation separating the posterior wing from the body (posterior umbonal angle), shell of medium size (25 to 38 mm), a deeply impressed byssal sinus, and regularly distributed growth rings (characters 1, 4, 18 and 25).

The first major clade supported by the parsimony analysis includes L. (Leiopte- ria) laevis, L. (Leiopteria) mitchell, L. (Leiopteria) rafinesquu, L. (Leioptertia) conradi, L. (Leiopteria) greeni, and L. (Leiopteria) sayi and L. (Leiopteria) penin- sularis (Figure 5.4, 5.5 and 5.6). The strict consensus tree (Figure 2) shows the monophyly of this group, but does not provide resolution within the clade. Due to the instability of this group and the

8 Postilla 229 Phylogenetic revision of Leptodesma

i

Table 2

Character state distribution for taxa in the phylogenetic analysis. Missing data indicated by “?”. Char- acter states listed as X, Y and Z are polymorphic, where X=(0&1), Y=(1&2), and Z=(2&3). Character

numbers are listed across the top.

aa aa eo nesta R Ue 22222222

123456789 0123456789 01234567

L. (Letopteria) accranus 111000?11 1110111011 00110110 L. (Leiopteria) acutilaris 110011001 alpla lalallala (0) 00112100 L. (Leiopteria) auriculata 110000001 TTT OU 11000000 L. (Leiopteria) ausablensis | 010000001 1010100001 10000002 L. (Leiopteria) bigsbyt 11X10x001 10XXX0101X 00100100 L. (Leiopteria) conradi 11110X1X1 101110X10x 01X11110 L. (Leiopteria) cornellt 010001001 1000101111 00110100 L. (Leiopteria) dekay1 100101001 1010000?00 01110100 L. (Leiopteria) gabbi 110000001 1010011170 00001110 L. (Leiopteria) greent 111000101 101000011X 01X11110 L. (Leiopteria) laevis 1111001X1 1111110010 00010XxY L. (Leiopteria) leat 11X100001 1110100000 00100100 L. (Leiopteria) linguiformis 110211011 1110000110 10001100 L. (Leiopteria) mitchelli 111200101 1011?0xX010 01011110 L. (Leiopteria) nitida 11X100001 101Xx00010 00010100 L. (Leiopteria) owent 010211711 1000?000?1 00001112 L. (Leiopteria) peninsularis 111100101 1011110000 01011110 L. (Leiopteria) rafinesquit 10X100101 101Xx00000 010xX1x10 L. (Letopteria) say1 111100111 1010000101 00001110 L. (Leiopteria) torrey1 110010011 1010001110 00000100 L. (Leiopteria) troosti 100111001 1?10001000 10112102 L. (Leptodesma) spinerigum 000000000 0000000000 00000003

relative lack of characters that unambigu- __ places L. (Leiopteria) nitida as the sister

ously define species, I synonymize these taxon to L. (Leiopteria) laevis, and is sup- aforementioned six species with L. ported by the shared development of (Leiopteria) laevis (see “Systematic Pale- sharp growth rings (character 23) (Figure 5.3, 5.4, 5.5 and 5.6).

The clade of L. (Leiopteria) leat, L. (Leiopteria) dekayi and L. (Leiopteria)

troosti is supported by a sharp angle of

ontology” below). The synonymy of many of Hall’s species has been previously sup- ported by McAlester (1962). The mono- phyly of the revised L. (Leiopteria) laevis is supported unambiguously by reduced convexity of the shell (character 7). The revised strict consensus tree (Figure 3)

posterior wing extension and prominent growth ring relief (characters 18 and 22) (Figure 6.1 and 6.2). Within this clade, the

Phylogenetic revision of Leptodesma

Postilla 229 9

sister relationship of L. (Leiopteria) dekayi and L. (Leiopteria) troosti is supported by all most-parsimonious reconstructions (Figures 2 and 3) as well as by jackknife analysis (Figure 3). These two species share the synapomorphies of a small angle between the edge of the posterior wing to the axis of greatest length (median um- bonal angle), the widest dimension of the shell located lateral to the hingeline, and sharp concentric growth rings (characters 2,6 and 23) (Figure 6.2).

The third clade supported by all most- parsimonious reconstructions includes the species L. (Leiopteria) torreyi, L. (Letopteria) linguiformis, L. (Leiopteria) owen, L. (Leiopteria) gabbi, L. (Leiopteria) auriculata, L. (Leiopteria) accranus, L. (Leiopteria) acutilaris and L. (Leiopteria) cornelli. The monophyly of this clade is supported by a decrease in size from mod- erate to small and the movement of the posterior wing inflection from a proximal to distal position (characters 4 and 17) (Figure 6.3, 6.4, 6.5 and 6.6). Within this group there are two smaller clades. The first of these includes L. (Leiopteria) lin- guiformis and L. (Leiopteria) owent as sister taxa, with L. (Leiopteria) torreyi as the sister species of that group. The sister group relationship of L. (Leiopteria) lin- guiformis and L. (Leiopteria) owent is supported by three characters: their large size, Maximal shell width lateral to the hingeline, and lamellose comarginal orna- mentation (characters 4, 6 and 24). The relationship of L. (Leiopteria) torreyi to these species is supported by the synapo- morphies of a reduced hingeline and umbo (characters 5 and 8) (Figure 6.3). The second clade within this species group includes L. (Leiopteria) gabbi, L.

(Letopteria) auriculata, L. (Leiopteria) accranus, L. (Leiopteria) acutilaris and L. (Letopteria) cornelli. This grouping is supported by a synapomorphous enlarged posterior wing (character 15). The mono- phyly of the remainder of the group ex- clusive of L. (Leiopteria) gabbi is supported by the development of a large anterior auricle and a strong separation of the posterior wing (characters 11 and 19) (Figure 6.4, 6.5 and 6.6). The monophyly of L. (Leiopteria) accranus, L. (Leiopteria) acutilaris and L. (Leiopteria) cornelli is supported by growth lamellae, which are both sharp and prominent (characters 22 and 23), and the sister relationship of L. (Leiopteria) acutilaris and L. (Leiopteria) cornelli is supported by the maximal width of the valve developed lateral to the hingeline (character 6).

Evolutionary and ecological implications oO

Apparently, many of the features reflect- ing evolutionary changes and speciation within L. (Leiopteria) involve aspects of the overall shape and size of species, as well as the development of features of the anterior and posterior wings. Ornamenta- tion changes do not appear to be as im- portant. The relative development of the anterior and posterior wings may be re- lated to the paleoecology of different species. In general, Leptodesma and simi- lar members of the Pterineidae have been interpreted as endobyssate to epibyssate, or epiphytic—epizoic (Kauffman 1969; Pojeta 1971; Stanley 1972; Johnston 1993; Bradshaw 1999). The arguments favoring these different modes of life center on comparisons with modern pterineids, wear pattern of comarginal ornamenta- tion, and inferred musculature (see John-

10 Postilla 229 Phylogenetic revision of Leptodesma

Leptodesma spinerigum Leiopteria ausablensis Leiopteria linguiformis

Leiopteria bigsbyi Leiopteria laevis Leiopteria nitida Leiopteria leai Leiopteria dekayi Leiopteria troosti Leiopteria torreyi Leiopteria oweni Leiopteria gabbi Leiopteria auriculata Leiopteria accranus Leiopteria acutilaris Leiopteria cornelli

83 79 ©)

79

98

Figure 3

Strict consensus of two most-parsimonious trees produced from analysis of character data in Table | with PAUP* v. 4.0b10 (Swofford 2002) when the L. (Leiopteria) laevis is considered as a single species following the synonymy proposed in the text. Tree length is 83 steps; retention index is 0.49; consistency index is 0.47; g, statistic for tree is -0.216. Jackknife values are indicated next to the node that they support. Character states were placed at the nodes using MacClade v. 3.04 (Maddi- son and Maddison 1992) under ACCTRAN optimization. Node numbers are circled on the clado- gram. Apomorphic characters that change unambiguously below a node are listed in parentheses. Node 1, 9(1); 10(1); Node 2, 1(1), 4(1), 18(1), 25(1); Node 3, 23(1); Node 4, 18(0), 22(1); Node 5, 2(0), 6(1), 23(1); Node 6, 4(0), 17(1); Node 7, 5(1), 8(1); Node 8, 4(2), 6(1), 24(1); Node 9, 15(1); Node 10, 11(1), 19(1); Node 11, 22(1), 23(1); and Node 12, 6(1).

Phylogenetic revision of Leptodesma

Postilla 229 1]

ston 1993 for a detailed review). It is pos- sible that some synapomorphies of clades recovered in this analysis, such as relative wing size or embayment development, may have allowed the included species to inhabit slightly different environments, or inhabit similar environments in slightly different ways.

The possible link of clade differentia- tion to paleoenvironment is apparent in the first two clades discussed above. All species within the L. (Leiopteria) leai,

L. (Letopteria) dekayi and L. (Leiopteria) troosti clade are found preserved in a siltstone to sandstone matrix. This may indicate that this clade radiated and was subsequently confined to a high energy shallow marine environment. On the other hand, all specimens of the revised

L. (Leiopteria) laevis were collected from a matrix of dark shale to siltstone or fine- grained limestone, which may indicate a deeper water or lower energy environ- mental preference, or both. However, the third clade, which includes L. (Lezopteria) gabbi, does not have a definite pattern of lithologic association (presumed environ- mental preference), as included species are patchily found in sandy, silty, and muddy lithologies.

Another pattern apparent from Figure 3 concerns the stratigraphic ranges of the species and their positions on the clado- gram. Neither of the first two clades (L. (Leiopteria) dekayi and the others of this group, or L. (Leiopteria) laevis and L. (Leiopteria) nitida) have member species that range beyond the Frasnian. The third clade (L. (Leiopteria) gabbi and others), however, includes both a Famennian and Mississippian species (L. (Leiopteria) linguiformis and L. (Leiopteria) cornelli,

respectively). Therefore, this could be the only clade of L. (Leiopteria) species that survived the Late Devonian biodiversity crisis and may have been the ancestral stock for the Mississippian and younger species of L. (Leiopteria). To further ad- dress this issue, studies including addi- tional Mississippian taxa would be desirable.

Paleobiogeographic Analysis

Methods

Paleobiogeographic patterns in

L. (Leiopteria) were evaluated in conjunc- tion with the phylogeny presented in Figure 3. This involved first substituting species’ geographic distributions for species’ names. Geographic distributions were assigned to presumed areas of en- demism that existed in the Devonian. Large-scale geological features define the boundaries of these areas of endemism, supported by the presence of large num- bers of unique taxa across the entire fauna in each of the regions. The areas of endemism considered within this analysis were: the Northern Appalachian Basin, which includes the Devonian strata in modern New York; the southern Appalachian Basin, which includes De- vonian strata in modern southern Penn- sylvania, Maryland and Virginia; the Michigan Basin, which includes Devon- ian strata in modern Michigan, western Ohio and southwestern Ontario; central North America, which includes Devonian strata in modern Wisconsin and Mis- souri; western North America, which includes Devonian strata in modern Nevada; and West Africa, which includes Devonian strata in modern Ghana. Cer-

12 Postilla 229

Phylogenetic revision of Leptodesma

Figure 4

Phylogeny from Figure 2, with biogeographic states substituted for terminal taxa and mapped onto the ancestral nodes. Inferred episodes of speciation by vicariance (V) and dispersal (D) are indi- cated. Ancestral nodes calculated using a modified Fitch optimization (Lieberman and Eldredge 1996; Lieberman 2000). 1, Northern Appalachian Basin; 2, Southern Appalachian Basin; 3, Mid- continent; 4, Michigan Basin; 5, Western North America; 6, Northern Africa.

tainly, other areas of endemism existed, but Devonian L. (Leiopteria) species were either not present in those regions or could not be obtained from them for study. In addition, although some of these regions could potentially be more finely divided biogeographically, this would create several additional regions with only a single taxon. This was not pursued because areas with only a single taxon can lead to artifactual problems for phylogenetic biogeographic analysis (Fortey and Cocks 1992; Lieberman 1997, 2000). After geographic distributions were placed at the tips of the tree, they were optimized to the ancestral nodes using a modified version of the Fitch (1971) parsimony algorithm described by Lieberman and Eldredge (1996) and

Lieberman (2000). The Fitch algorithm, in this context, assumes unordered trans- formations between areas. The area cladogram is shown in Figure 4.

Results

Phylogenetic biogeography provides two related types of information: First, the ranges of ancestral nodes are reconstructed permitting discussion of which areas were inhabited the ancestors of species or clades. Second, the mode of speciation (vicariance or dispersal) can be inferred for some cladogenetic events. Examination of this area cladogram shows that the L. (Leiopteria) species included in this analysis are present ances- trally in the both the Appalachian and Michigan basins. Throughout most of the

Phylogenetic revision of Leptodesma

Postilla 229 ifs}

evolutionary history of this group, specia- tion events were related to dispersal events that originated from the northern Ap- palachian basin. It is only relatively late in the phylogenetic history of this clade (near the terminus of the L. (Leiopteria) auriculata through L. (Leiopteria) cornelli clade), that the Southern Appalachian basin also became a center for evolution. Species inhabiting additional basins en- tered these regions by subsequent range expansions, which may correspond to episodes of traditional dispersal (sensu Humphries and Parenti 1986) or geodis- persal (sensu Lieberman and Eldredge 1996). Episodes of range expansion seem frequent and can be identified by an ex- pansion or shift in the geographic distrib- ution of a descendant relative to its ancestor (indicated in Figure 4). By con- trast, another prominent biogeographic pattern within these species is the limited amount of vicariant differentiation, which can be identified by a contraction in the range of a descendant species relative to its ancestor (indicated in Figure 4). In fact, there is evidence for only two episodes of vicariance in the history of this clade, and both of these occurred early in the history of the clade, at the first cladogenetic event recorded within the ingroup.

Implications

The paucity of vicariance seems low com- pared to documented levels of vicariant speciation in extant taxa described by Brooks and McLennan (1991). Reduction in speciation and increased dispersal in Middle to Late Devonian bivalves has been noted by Bailey (1978, 1983), who documented increased dispersal between

Europe and the Appalachian Basin in other bivalve lineages during the Middle Devonian, as well as reduced vicariant speciation in the Middle Devonian of Europe compared to the Early Devonian, and Amler (1999), who observed low speciation levels in Late Devonian Euro- pean bivalve faunas. Lieberman (1999) also commented on the increased ten- dency for Middle Devonian trilobite taxa to disperse relative to Cambrian taxa. This was associated with a concomitant relative decline in vicariance. A relative reduction in vicariance with respect to dispersal was also observed in Middle and Late Devonian phyllocarids (Rode and Lieberman 2002). This relative lack of vicariance during the Middle to Late Devonian may be a cross-faunal phenom- enon, and if so should be examined within the context of the dramatic biotic changes during the Middle and Late De- vonian.

The Devonian was a time of intense biotic overturn that included a dramatic change from endemic Middle Devonian faunas to a cosmopolitan fauna during the Late Devonian (Boucot 1975; Oliver 1976, 1990; Bailey 1978, 1983; Klapper and Johnson 1980; McGhee 1981, 1996). The formation of this cosmopolitan biota can be attributed largely to sea level rise and the reduction of tectonic barriers to inter- basinal faunal exchange (Bailey 1978, 1983; McGhee 1996) These conditions would likely promote a decline in isola- tion of populations and hence vicariant speciation (Mayr 1942). Speciation rates can decline simply as a by-product of diminished opportunities for vicariance, and any clade that shows an extensive history of dispersal, along with minimal

14 Postilla 229

Phylogenetic revision of Leptodesma

vicariance, should show a tendency to- wards lowered speciation rates (Rode and Lieberman 2002).

Systematic Paleontology

SuBcLass Pteriomorpha Beurlen 1944 Orper Pterioida Newell 1965 SUPERFAMILY Pterioidea Gray 1847 FAMILY Pterineidae Miller 1877

Genus Leptodesma (Leiopteria) Hall 1883

Type species. Leiopteria dekayi Hall 1883, by subsequent designation (Miller 1889).

Discussion. Leptodesma (Leiopteria) was originally afforded a generic ranking by Hall (1883), but was transferred to Lep- todesma as a subgenus by Newell and La Rocque (1969). Thus, Leptodesma (sensu Newell and La Rocque 1969) includes

L. (Leptodesma) and L. (Leiopteria) Hall 1883, and these two subgenera are inter- preted as sister taxa. Newell and La Rocque (1969) distinguished the subgen- era based on the shape of the anterior auricle: rounded in L. (Leiopteria) and nasuate in L. (Leptodesma). Additional characters that have been proposed to separate the taxa include a more oblique shape, smaller size, and less pronounced byssal sinus in L. (Leptodesma) (Williams and Breger 1916; Pojeta and others 1986). Another character, which is likely a synapomorphy for L. (Leiopteria), is the presence of an anterior clavicle or septum (Williams and Breger 1916; Bradshaw 1999). The monophyly of L. (Leiopteria) is supported based on the stability of the previously proposed characters as ob- served in the specimens examined. Based on previous comments regarding the

phylogenetic validity of the two taxa (see Pojeta and others 1986; Amler 1995), additional analyses designed to examine the monophyly of L. (Leiopteria) would be worthwhile.

LEPTODESMA (LEIOPTERIA ) ACCRANUS RODE, NEW SPECIES Figure 6.4.

Leiopteria sp.; Saul in Saul and others 1963:1045, pl. 136, figs. 18-19.

Types. The holotype is YPM 22385 (Fig- ure 6.4), a left valve collected from the clay shale unit of the Accraian series of Early to Middle Devonian age. The speci- men was collected in a small quarry (now covered over) on the coast just east of the Ambassador Hotel Beach and just west of Black Star Square in Accra, Ghana (Saul and others 1963).

Diagnosis. Shell small (holotype height 16.2 mm), greatest width along hingeline, posterior umbonal angle large, obliquity high, convexity moderate; anterior auricle large (approximately one-fourth of hinge- line) with septum separating auricle from main body, byssal sinus weakly impressed; posterior wing small (approximately one- half of hingeline), embayment weak, wing tip not greatly extended, posterior wing weakly separated from main body; promi- nent, sharp comarginal lamellae constant on shell, forming distinct rows; lamellae group into sets of one prominent ring with several reduced rings.

Description. Small L. (Leiopteria) with subequal width and height. Angle of obliquity large (approximately 25°) result-

Phylogenetic revision of Leptodesma

Postilla 229 15

ing in a moderately recumbent posture. hingeline long relative to maximum length (approximately 90%). Ligament and lateral teeth not preserved. Anterior auricle large and rounded, separated from main body by septum. Anterior margin undulated with weakly impressed byssal notch. Posterior wing short. Separation of posterior wing from main body marked by inflection in ornamentation, but only weak change in convexity. Embayment of posterior wing apparent but not deep. Comarginal ornamentation well devel- oped throughout entire shell. Growth bands are distinct ridges, but not all of same relief or prominence. On main shell body, prominent rings occur regularly separated by one or two less prominent rings. On anterior and posterior wings, ridges are subequal. No evidence of radial ornamentation or internal musculature observed.

Discussion. Leptodesma (Leiopteria) ac- cranus is distinguished from other species of L. (Leiopteria) by the combination of a large anterior auricle, reduced posterior wing and embayment, and interspersed prominent and less prominent growth bands. This species is most closely related to L. (Leiopteria) acutilaris and L. (Leiopteria) cornelli. All three species share the synapomorphies of growth lamellae that are both sharp and prominent in relief. L. (Leiopteria) acutilaris and L. (Leiopteria) cornelli are distinguished by their maximum shell width located lateral to the hingeline.

Saul and others (1963) figured the holotype, but left the species in open nomenclature although they cited a posi- tive identification to L. (Leiopteria). The

reconstructed phylogenetic position of this taxon as a distinct lineage within a well-resolved clade (Figures 2 and 3) indicates that a new species designation is appropriate.

Etymology. Named to reflect both Accra, Ghana, the collection locality, and the stratigraphic unit, the Accraian Series.

Other material examined. YPM 22386 (paratype).

Occurrence. Lower to Middle Devonian Accraian Series in Accra, along the Atlantic coast of Ghana.

LEPTODESMA (LEIOPTERIA) ACUTILARIS POHL 1929 Figure 6.5.

Leiopteria acutilaris; Pohl 1929:40—41, pl. 5, figs. 9-12.

Types. When Pohl (1929) originally de- scribed this species, he did not designate a holotype, and a lectotype has not been subsequently assigned. Therefore, MPM 13740 is designated herein as the lecto- type. MPM 13740 is a left valve with ex- cellent preservation of the anterior auricle and comarginal ornamentation. The shell is entire with the exception of the poste- rior wing.

Emended diagnosis. Shell small (height up to 14.0 mm), hingeline short, greatest width lateral to hingeline, posterior um- bonal angle large, obliquity high, convexity high; anterior auricle large (approximately one-third of hingeline) with septum sepa- rating auricle from main body, byssal sinus

16 Postilla 229 Phylogenetic revision of Leptodesma

Figure 5

1, Leptodesma (Letopteria) ausablensis, UMMP 38114 (holotype), left valve, 1.6x; 2, L. (Leiopteria) bigsbyi, AMNH 5263 (lectotype), left valve, 1.4x; 3, L. (Letopteria) nitida, YPM 82914, left valve, 1.5x; 4, L. (Letopteria) laevis, left valve, 4.0x, AMNH 41903 (lectotype); 5, L. (Leiopteria) laevis, UMMP 24579 (formerly L. (Leiopteria) peninsularis [holotype]), left valve, 1.1x; 6, L. (Leiopteria) laevis, AMNH 5264 (formerly L. (Leiopteria) conradi [syntype]), left valve, 1.1x.

Phylogenetic revision of Leptodesma

Postilla 229 17

nr

strongly impressed; posterior wing small (approximately one-half of hingeline), posterior wing strongly separated from main body; prominent, sharp, crenulated comarginal lamellae constant on shell, forming distinct rows.

Other material examined. MPM 13739 (paralectotype).

Occurrence. Middle Devonian, Milwaukee Formation (Zone C), Milwaukee Co., Wisconsin.

LEPTODESMA (LEIOPTERIA) BIGSBYI HALL 1883 Figure 5.2.

Leiopteria bigsbyi; Hall 1883:pl. 20, figs. 3, 11, 13-15; Hall 1884b:165—166, pl. 20, figs. 3, 11, 13-15, pl. 88, fig. 23; Clarke and Schwartz 1913:634—635, pl. 62, figs. 10-11; McAlester 1962:29.

Liopteria bigsbyi Hall; Miller 1889:484.

Types. Hall (1883) did not designate a holotype in the original description, and a lectotype has not subsequently been des- ignated. Therefore, AMNH 5263 is herein designated as the lectotype. AMNH 5623 is a left valve with entire anterior and posterior extremities, as well as ornamen- tation preserved; part of the posterolateral margin is not preserved (Figure 6.1).

Emended diagnosis. Shell size medium (height 25 to 49 mm), hingeline long, posterior umbonal angle large, obliquity high, convexity high, umbo prominent; anterior auricle small (approximately one-fifth of hingeline); posterior wing large (approximately three-fourths of

hingeline), embayment weak, wing tip not greatly extended; prominent, dull comar- ginal lamellae constant on shell, forming distinct rows.

Other material examined. NYSM 2629-2632 (paralectotypes).

Occurrence. Middle Devonian, Hamilton Group, Pratts Falls, Onondaga Co., and Schoharie, Schoharie Co., New York.

LEPTODESMA (LEIOPTERIA) DEKAYI HALL 1883 Figure 6.2.

Leiopteria dekay1; Hall 1883:pl. 19, fig. 1, pl. 20, figs. 16-18 (19 in error); Hall 1884b:164-165, pl. 19, fig. 1, pl. 20, figs. 16-18, pl. 88, figs. 5-10; Shimer and Schrock 1944:385, pl. 149, fig. 5; Ehlers and Wright 1959:10, pl. 1, figs. 3—4; McAlester 1962:29-31; Pojeta and others 1986:94—95, fig. 16a—16d.

Liopteria dekayi Hall; Miller 1889:484, fig. 835.

Leptodesma (Leiopteria) dekayi Hall; Newell and La Rocque 1969:N301, fig. €35,.6:

Types. Hall (1883) did not designate a holotype in the original description, and a lectotype has not subsequently been des- ignated. Several previously illustrated specimens have limitations as a potential lectotype. NYSM 2639 is well preserved, but it was figured by Hall (1883:pl. 19, fig. 1, 1884b: pl. 19, fig. 1) with a radial orna- ment, which is lacking in this species. NYSM 2640 was illustrated by both Shimer and Shrock (1944) and Ehlers and Wright (1959), but this specimen was

18 Postilla 229 Phylogenetic revision of Leptodesma

Figure 6

1, Leptodesma (Leiopteria) leai, NYSM 2658 (lectotype), left valve, 2.8x; 2, L. (Leiopteria) dekayi, NYSM 2641 (lectotype), left valve, 1.8x; 3, L. (Leiopteria) torreyi, NYSM 2671 (lectotype), left valve, 1.5x; 4, L. (Leiopteria) accranus, YPM 22385 (holotype), left valve, 3.3x; 5, L. (Leiopteria) acutilaris, MPM 13740 (lectotype), left valve, 3.7x; 6, L. (Leiopteria) cornelli, PRI 5242 (holotype), right valve, 1.3x.

Phylogenetic revision of Leptodesma

collected from drift and hence has re- duced stratigraphic control. It would be advantageous to choose the specimen figured in the Treatise (Newell and La Rocque 1969) for the lectotype specimen. However, this specimen is not a member of the syntype series and, therefore, ineli- gible for lectotype designation.

On the other hand, NYSM 2641 isa well-preserved left valve, with a complete anterior auricle that has the prominent anterior septum, an almost entirely pre- served posterior wing, and well-developed ornamentation (Figure 6.2). NYSM 2641 has been previously illustrated as an ex- emplar of the species (Hall 1884b:pl. 20, fig. 17; Pojeta and others 1986), and is thus an appropriate choice for the lecto- type; it is hereby so designated.

Emended diagnosis. Shell size medium (height range 19 to 36 mm), hingeline long, greatest width lateral to hingeline, posterior umbonal angle large, obliquity low, convex- ity high, umbo prominent; anterior auricle small (approximately one-fifth of hinge- line), septum separating auricle from main body, byssal sinus weakly impressed; poste- rior wing large (approximately seven-tenths of hingeline), embayment pronounced, wing tip greatly extended, posterior wing strongly separated from main body; promi- nent, sharp comarginal lamellae constant on shell, forming distinct rows that increase in width posteriorly.

Other material examined. NYSM 2639-2640 and 2642 (paralectotypes), 2643-2647 (hypotypes), E1088—E1089.

Occurrence. Middle Devonian, Hamilton Group, Lake Skaneateles and Lake

Postilla 229 19

Cayuga, Pratts Falls, Onondaga Co., Schoharie, Schoharie Co., New York.

LEPTODESMA (LEIOPTERIA) LAEVIS HALL 1843 Figures 5.4, 5.5 and 5.6.

Leiopteria laevis; Hall 1843:181; Miller 1877:202; Hall 1883:pl. 17, figs. 5-11; Hall 1884b:158-159, pl. 17, figs. 5-11, pl. 20, fig. 5; Kindle in Prosser and Kindle 1913:253—254, pl. 29, fig. 6; Shimer and Schrock 1944:385, pl. 149, figs. 2-3.

Liopteria laevis Hall; Miller 1889:484.

Leiopteria conradi; Hall 1883:pl. 20, figs. 1, 2,4 (5 in error); Hall 1884b:159—160, pl. 20, figs. 1, 2, 4, pl. 88, figs. 1-4.

Leiopteria cf. conradi Hall; Kindle in Prosser and Kindle 1913:252-253, pl. 28, fig. 13.

Liopteria conradi Hall; Miller 1889:484.

Leiopteria greeni; Hall 1883:pl. 20, figs. 9, 12; Hall 1884b:160, pl. 20, figs. 9,

12, pl. 88, figs. 21—22.

Liopteria greeni Hall; Miller 1889:484.

Leiopteria mitchelli; Hall 1883:pl. 20, fig. 8; Hall 1884b:166-167, pl. 20, fig. 8, pl. 88, fig. 26; McAlester 1962:29.

Liopteria mitchelli Hall; Miller 1889:484.

Leiopteria peninsularis; La Rocque 1950:283-284, pl. 4, figs. 1-2.

Leiopteria rafinesquii; Hall 1883:pl. 15, fig. 11, pl. 20, fig. 6-7; Hall 1884b:161- 162, pl. 15, fig. 11, pl. 20, figs. 6-7, pl. 88, figs. 27-28; Walcott 1884:166, pl. 5, figs. 10, 10a; Shimer and Schrock 1944:385 pl. 149, fig. 5; Ehlers and Wright 1959:6-7, pl. 1, figs. 1-2.

Liopteria rafinesquii Hall; Miller 1889:484, fig. 836.

Leiopteria sayi; Hall 1884b:162—163, pl.

20 Postilla 229

Phylogenetic revision of Leptodesma

88, figs. 15-20; McAlester 1962:29. Liopteria sayi Hall; Miller 1889:484.

Types. Hall (1843) did not designate a holotype in the original description, and a lectotype has not subsequently been des- ignated. AMNH 41903 is here designated as the lectotype. AMNH 41903 is a well- preserved entire left valve (Figure 5.4). The anterior auricle and posterior wings are preserved in detail, as is the comar- ginal ornamentation. This specimen was figured previously by Hall (1883:pl. 17, fig. 10, 1884b:pl. 17, fig. 10).

Emended diagnosis. Shell small to large, body obliquely ovate, hingeline long, convexity low, posterior umbonal angle large, umbo pronounced; anterior auricle small, septum present; posterior wing with pronounced embayment, often ex- tended into acuminate projection, typi- cally demarcated from body by distinct groove; sharp growth bands developed constantly over shell, width may increase posteriorly; lamellose growth bands ap- parent in larger specimens.

Discussion. The oversplitting of L. (Leiopteria) species of Hall (1883, 1884b) has long been recognized (Williams and Breger 1913; Rau 1955; McAlester 1962). The original species designations were often based on only a few specimens and frequently only from a single locality (for example, L. (Leiopteria) mitchelli and

L. (Leiopteria) greeni). Leptodesma (Leiopteria) laevis, L. (Leiopteria) conrad1, L. (Leiopteria) greent, L. (Letopteria) mitchelli and L. (Leiopteria) sayi are known only from dark shale facies of the Middle Devonian Hamilton Group of

New York. Of the two additional species, L. (Leiopteria) peninsularis is known only from the Middle Devonian Dundee Lime- stone of Michigan, while L. (Leiopteria) rafinesquii has been recorded from the Hamilton Group of New York and the Delaware Limestone of central Ohio and Early Devonian strata of Nevada. The lack of resolution within the phylogenetic analysis suggests that the other six species are not well established and morphologi- cal characters (at least those included within this analysis) do not distinguish them from L. (Leiopteria) laevis.

The morphologies of the six newly synonymized species are indistinguish- able. However, smaller specimens (those formerly referred to L. (Leiopteria) laevis under Hall’s description [1884b]) tend to have comarginal ornamentation of dis- tinct, sharp bands (Figure 5.4). Larger specimens, however, all have lamellose ornamentation in which each growth band is a platform rather than a narrow raised ridge (Figure 5.5 and 5.6). Addi- tionally, a gradation of relative amount of posterior wing projection can be observed within the revised species. In general, as size increases, the relative amount of pro- jection increases (compare Figure 5.4 and 5.6). More examples of such gradations may exist and further analysis could place such changes within an ontogenetic or environmental context.

Other material examined. Leptodesma (Leiopteria) laevis Hall: AMNH 41903-41904 (syntypes), NYSM 2652-2657 (hypotypes); L. (Leiopteria) conradi Hall: AMNH 5264 (syntype), NYSM 2634-2635 (syntypes), 2636-2638 (hypotypes); L. (Leiopteria) greent Hall:

Phylogenetic revision of Leptodesma

Postilla 229 21

AMNH 5265 (syntype), NYSM 2649 (syn- type), 2650-2651 (hypotypes); L. (Leiopte- ria) mitchelli Hall: AMNH 5266 (holotype); L. (Leiopteria) peninsularis La Rocque: UMMP 24579 (holotype), 24580 (paratype); L. (Leiopteria) rafinesquii Hall: NYSM 2663 (lectotype), 2661-2662 and 2664 (paratypes), AMNH 4208 (hypotype), USNM 13882 (6 specimens); L. (Leiopteria) sayi Hall: NYSM 2665-2670 (syntypes).

Occurrence. Lower Devonian of the Eu- reka District, Nevada. Delaware Lime- stone, Delaware, Ohio. Marcellus Shale at Littleville, Livingston Co., Alden, Erie Co., and East Bloomfield, Ontario Co., New York. Hamilton Shales at Lake Cayuga, Lake Skaneateles and Lake Canandaigua; Bellona, Yates Co., Leonardsville, Madison Co., Norton’s Landing, Cayuga Co., and Ontario Co., New York. Coarse grits in Schoharie Co., New York. Romney Forma- tion, Onondaga Member, near Old Town and Cumberland, Maryland.

LEPTODESMA (LEIOPTERIA) LEAI HALL 1884 Figure 6.1.

Leiopteria leai; Hall 1884b:168—169. pl. 88, figs. 24-25; McAlester 1962:29. Liopteria leai Hall; Miller 1889:484.

Types. Hall (1884b) did not designate a holotype in the original description, and a lectotype has not subsequently been des- ignated. Therefore, NYSM 2658 is here designated as the lectotype. NYSM 2658 is a left valve in which the anterior auricle is entire. The tip of the posterior wing is absent and part of the posterolateral mar- gin is not preserved (Figure 6.1). NYSM

2658 is a better choice for the lectotype than NYSM 2659 because the latter lacks in the anterior auricle, umbo and poste- rior wing tip (Hall 1884b:pl. 88, fig. 25).

Emended diagnosis. Shell small (height ranges from 14 to 23 mm), hingeline long, greatest width along hingeline, posterior umbonal angle large, obliquity high, con- vexity high, umbo moderate; anterior auricle large (approximately one-fourth of hingeline) with septum separating auricle from main body, byssal sinus weakly im- pressed; posterior wing large (up to three- fourths of hingeline), embayment pronounced, wing tip greatly extended, posterior wing strongly separated from main body; prominent, dull comarginal lamellae constant on shell, forming dis- tinct rows.

Other material examined. NYSM 2659 (paralectotype).

Occurrence. Middle Devonian, Hamilton Group, southern Schoharie Co., New York.

LEPTODESMA (LEIOPTERIA) TORREYI HALL 1884 Figure 6.3.

Leiopteria torreyi; Hall 1884b:174. pl. 22, figs. 6—7, pl. 88, fig. 11; McAlester 1962229"

Liopteria torreyi Hall; Miller 1889:484.

Types. Hall (1884b) did not designate a holotype in the original description, and a lectotype has not subsequently been des- ignated. Therefore, NYSM 2671 is here designated as the lectotype. NYSM 2671 is

22 Postilla 229

Phylogenetic revision of Leptodesma

i

a complete left valve in which the anterior auricle, posterior wing and ornamenta- tion are all well preserved.

Emended diagnosis. Shell small (height ranges from 21 to 22 mm), hingeline short, greatest width along hingeline, posterior umbonal angle large, obliquity high, con- vexity high, umbo moderate; anterior auri- cle small (approximately one- sixth of hingeline) with septum separating auricle from main body, byssal sinus weakly im- pressed; posterior wing large (approxi- mately five-sixths of hingeline), embayment weak, wing tip not greatly extended, poste- rior wing strongly separated from main body; dull comarginal lamellae constant on shell, forming distinct rows.

Other material examined. NYSM 2672 (paralectotype).

Occurrence. Late Devonian, Chemung Group, near Panama, New York.

Notes on Material Examined

The following taxa and material examined do not require synonymy, lectotype desig- nation, or detailed discussion: Leptodesma (Leiopteria) auriculata Clarke and Schwartz 1913: USNM 178306 (holotype); L. (Leiopteria) ausablensis Ehlers and Wright 1959: UMMP 38114 (holotype), and 38111-38113, 38115-38119 (paratypes); L. (Letopteria) cornelli Caster 1930: PRI 5242 (holotype); L. (Leiopteria) gabbi Hall 1884b: NYSM 2648 (holotype); L. (Leiopteria) linguiformis Hall 1884b: NYSM 8870 (holotype); L. (Letopteria) marylandica Clarke and Schwartz 1913: USNM 178288-—178289 (syntypes);

L. (Leiopteria) nitida Hall 1883: YPM 21378, 21380, 21382, 21384A, 22655-22656, 82914, NYSM 2633 (holo- type); L. (Leiopteria) owent Hall 1883: NYSM 2660 (holotype); L. (Leiopteria) troosti Hall 1884b: NYSM 2673 (holo- type); L. (Leptodesma) spinerigum (Con- rad 1842) [type lost]: YPM 21414, 21450 (hypotypes), AMNH 6094 (hypotype).

Acknowledgments

The following people graciously arranged the loan of specimens in their care: T. White (YPM); G. Gunnell (UMMP); B. Hussaini (AMNH)); P. Mayer (MPM); E. Landing,

L. Hernick and S. Mannolini (NYSM);

J. Pojeta and M. Florence (USNM); R. Ross and P. Krohn (PRI). The author thanks B. S. Lieberman for discussions and comments on an earlier version of this manuscript, and R. A. Robison for assistance with pho- tography. Reviews by J. Pojeta, H. Rollins and J. B. Bailey also improved the manu- script. This research was supported by: the Department of Geology, University of Kansas; an NSF graduate student fellow- ship; a Self Graduate Fellowship; and grants NSF EAR-0106885 and OPP-9909302 to

B. S. Lieberman.

About the Author

Alycia L. Rode

Department of Geology University of Kansas

1475 Jayhawk Blvd. Lawrence, Kansas 66045 USA arode@ku.edu

Phylogenetic revision of Leptodesma Postilla 229 23

Literature Cited

Amler, M. R. W. 1995. Die Bivalvenfauna des Oberen Famenniums West-Europas. 1. Einfurung, Lithostratigraphie, Faunen Ubersicht, Systematik 1. Pteriomorphia. Geol. Paleontol. 29:29-143.

— 1999. Extinction and radiation of bivalves in the Late Devonian. In: L. Harper, J. Taylor and A. Crame, ed. Paper and Poster Abstracts, Biology and Evolution of the Bivalvia; 1999 September 14-17; Cambridge, UK. Cambridge: Malacological Society, London, pp. 2-3.

Bailey, J. B. 1978. Provincialism and migration in Lower and Middle Devonian pelecypods. Palaeogeog., Palaeoclimatol., Palaeoecol. 23:119—-130.

—1983. Middle Devonian Bivalvia from the Solsville Member (Marcellus Formation), central New York State. Bull. Am. Mus. Nat. Hist. 174:193-—326.

Boucot, A. J. 1975. Evolution and extinction rate controls. Amsterdam: Elsevier. 427 pp.

Boyd, D. W. and N. D. Newell. 2001. Silicified Leptodesma (Bivalvia: Pteriomorphia) from the Texas Permian. Am. Mus. Novit. 3347:1—10.

Bradshaw, M. A. 1999. Lower Devonian bivalves from the Reefton Group, New Zealand. Mem. Assoc. Australas. Palaeontol. 20:1—171.

Brooks, D. R. and D. A. McLennan. 1991. Phylogeny, ecology, and behavior. Chicago: Univ. Chicago Pr. 434 pp.

Buerlen, K. 1944. Beitrage zur Stammesgeschichte der Muscheln. Bayer. Akad. Wiss., Sitz. 1—-2:133-145.

Caster, K. E. 1930. Higher fossil faunas of the Upper Allegheny. Bull. Am. Paleontol. 15:1-174.

Clarke, J. M. and C. K. Schwartz. 1913. Systematic paleontology of the Upper Devonian deposits of Maryland. Md. Geol. Surv., Middle and Upper Devonian: pp. 539-699.

Conrad, T.A. 1842. Observations on the Silurian and Devonian systems in the United States, with descriptions of new organic remains. Acad. Nat. Sci. Phila. J. 8:228-280.

Cox, L. R., N. D. Newell, D. W. Boyd, C. C. Branson, R. Casey, A. Chavan, A. H. Coogan, C. Dechaseaux, C. A. Fleming, F. Haas, and others. 1969. Bivalvia. In: R. C. Moore, ed. Treatise on invertebrate paleontology, part N, Mollusca 6(1). Lawrence, KS: Geol. Soc. Am. and Univ. Kans. Pr. 489 pp.

Ehlers, G. M. and E. P. Wright. 1959. Leiopteria rafinesquii Hall and a new species of the genus from the Thedford—Arkona region of southwestern Ontario. Contrib. Mus. Paleontol. Univ. Mich. 15:1—13.

Felsenstein, J. 1985. Confidence limits on phylogenies: an approach using the bootstrap. Evolution 39:783-791.

Fitch, W. M. 1971. Toward defining the course of evolution: minimum change for a specific tree topology. Syst. Zool. 20:406—416.

24 Postilla 229 Phylogenetic revision of Leptodesma

Fortey, R. A. and L. R. M. Cocks. 1992. The early Palaeozoic of the North Atlantic region as a test case for the use of fossils in continental reconstruction. Tectonophysics 206:147-158.

Frech, F. 1891. Die devonischen Aviculiden Deutschlands: Ein Beitrag zur Systematik und Stammesgeschichte der Zweischaler. Abh. Geol. Spec. Preuss. Thiiring. Statten 9:1—253.

Gray, J. E. 1847. A list of the genera of Recent Mollusca, their synonyms and types. Proc. Zool. Soc. Lond. 15:129-219.

Hall, J. 1843. Report of the Fourth District. Albany: Geol. Surv. N. Y. 181 pp.

——1883. Lamellibranchiata, plates and explanations: Nat. Hist. N. Y., Geol. Surv. N. Y., Palaeontol. 5(1):20 pp.

——1884a. Classification of the Lamellibranchiata. First Annual Report of the State Geologist. New York Assembly [1882] doc. 32, 15 pp., 11 pls.

—1884b. Descriptions and figures of the Monomyaria of the Upper Helderberg, Hamilton, and Chemung Groups: Nat. Hist. N. Y., Geol. Surv. N. Y., Palaeontol. 5(1) Lamellibranchiata 1: 268 pp.

Hillis, D. M. 1991. Discriminating between phylogenetic signal and random noise in DNA sequences. In: M. M. Miyamoto and J. Cracraft, eds. Phylogenetic analysis of DNA sequences. New York: Oxford Univ. Pr. pp. 278-294.

Hillis, D. M. and J. P. Huelsenbeck. 1992. Signal, noise, and reliability in molecular phylogenetic analyses. J. Hered. 83:189-195.

Humphries, C. J. and L. Parenti. 1986. Cladistic biogeography. Oxford Biogeogr. Ser. 2:1—98.

Johnston, P. A. 1993. Lower Devonian pelecypods from southeastern Australia. Mem.

Assoc. Australas. Palaeontol. 14:1—134.

Kauffman, E.G. 1969. Form, function, and evolution. In: R. C. Moore, ed. Treatise on invertebrate paleontology, part N, Mollusca 6(1). Lawrence, KS: Geol. Soc. Am. and Univ. Kans. Pr. pp. N129-205.

Klapper, G. and J. G. Johnson. 1980. Endemism and dispersal of Devonian conodonts. J. Paleontol. 54:400—455.

Klassen, G. J., R. D. Mooi and A. Locke. 1991. Consistency indices and random data. Syst. Zool. 40:446—457.

La Rocque, A. 1950. Pre-Traverse Devonian pelecypods of Michigan. Contrib. Mus. Paleontol. Univ. Mich. 7:271—366.

Lieberman, B. S. 1997. Early Cambrian paleogeography and tectonic history: a biogeographic approach. Geology 25:1039—1042.

——1999. Testing the Darwinian legacy of the Cambrian radiation using trilobite phylogeny and biogeography. J. Paleontol. 73:176-181.

Phylogenetic revision of Leptodesma Postilla 229 25

——2000. Paleobiogeography: using fossils to study global change, plate tectonics, and evolution. New York: Kluwer Acad. Pr. 208 pp.

Lieberman, B. S. and N. Eldredge. 1996. Trilobite biogeography in the Middle Devonian: geological processes and analytical methods. Paleobiology 22:66-79. Maddison, W. P. and D. R. Maddison. 1992. MacClade: Analysis of phylogeny and character evolution [computer program]. Version 3.04. Sunderland, MA: Sinauer. Mayr, E. 1942. Systematics and the origin of species. New York: Columbia Univ. Pr. 334 Pp:

McAlester, A. L. 1962. Upper Devonian pelecypods of the New York Chemung Stage. Bull. Peabody Mus. Nat. Hist. 16:1-88.

McGhee, G. R., Jr. 1981. Evolutionary replacement of ecological equivalents in Late Devonian benthic marine communities. Palaeogeog., Palaeoclimatol., Palaeoecol.

34:267-283.

— 1996. The Late Devonian mass extinction: the Frasnian/Famennian crisis. New York: Columbia Univ. Pr. 303 pp.

Miller, S. A. 1877. The American Paleozoic fossils. Cincinnati, OH: Western Methodist Book Concern Pr. 245 pp.

— 1889. North American geology and paleontology for the use of amateurs, students, and scientists. Cincinnati, OH: Western Methodist Book Concern Pr. 718 pp.

Newell, N. D. 1965. Classification of the Bivalvia. Am. Mus. Novit. 2206:1—25.

Newell, N. D. and A. La Rocque. 1969. Family Pterineidae Miller, 1877. In: R. C. Moore, ed. Treatise on invertebrate paleontology, part N, Mollusca 6(1). Lawrence, KS: Geol. Soc. Am. and Univ. Kans. Pr. pp. N298—302.

Oliver, W. A., Jr. 1976. Biogeography of the Devonian rugose corals. J. Paleontol. 50:365—373.

——]990. Extinctions and migrations of Devonian rugose corals in the Eastern Americas realm. Lethaia 23:167—178.

Pohl, E. R. 1929. The Devonian of Wisconsin: part 1, Lamellibranchiata. Bull. Public Mus. Milwaukee 11:1—100.

Pojeta, J., Jr. 1971. Review of Ordovician pelecypods. U.S. Geol. Surv., Prof. Pap. 695:1—46.

Pojeta, J., Jr., R. Zhang and Z. Yang. 1986. Systematic paleontology of Devonian pelecypods of Guangxi and Michigan. In: J. Pojeta, Jr., ed. Devonian rocks and Lower and Middle Devonian pelecypods of Guangxi, China, and the Traverse Group of Michigan. U.S. Geol. Surv., Prof. Pap. 1394:57—108.

Prosser, C. S. and E. M. Kindle. 1913. Pelecypoda. In: C. S. Prosser, E. M. Kindle and C. K. Schwartz. The Middle Devonian deposits of Maryland. Baltimore: Md. Geol. Surv. pp. 214-279.

26 Postilla 229 Phylogenetic revision of Leptodesma

Rau, J. L. 1955. Upper Devonian and Lower Mississippian Leptodesma from Southwestern Pennsylvania [master’s thesis]. Cincinnati, OH: University of Cincinnati. 96 pp.

Rode, A. L. and B. S. Lieberman. 2002. Phylogenetic and biogeographic analysis of Devonian phyllocarid crustaceans. J. Paleontol. 76:27 1—286.

Sanderson, M. J. 1989. Confidence limits of phylogenies: the bootstrap revisited. Cladistics 5:113-129.

Saul, J. M., A. J. Boucot and R. M. Finks. 1963. Fauna of the Accraian Series (Devonian of Ghana) including a revision of the gastropod Plectonotus. J. Paleontol. 37:1042—1053. Shimer, H. V. and R. B. Shrock. 1944. Index fossils of North America. Cambridge, MA: Mass. Inst. Tech. Pr. 837 pp.

Spriesterbach, J. and A. Fuchs. 1909. Die Fauna der Remscheider Schichten. Abh. Konig. Preuss. Geol. Landesanst., Neue Folge 58:1—81.

Stanley, S. M. 1972. Functional morphology and evolution of byssally attached bivalve mollusks. J. Paleontol. 46:165—212.

Swofford, D. L. 2002. PAUP* (Phylogenetic analysis using parsimony) [computer program]. Version 4.0b10. Sunderland, MA: Sinauer.

Walcott, C. D. 1884. Paleontology of the Eureka District. U. S. Geol. Surv. Monogr. 8:1-298.

Williams, H. S. and C. L. Breger. 1916. The fauna of the Chapman Sandstone of Maine including descriptions of some related species from the Moose River Sandstone. U. S. Geol. Surv., Prof. Pap. 89:1-339.

in 3 9088 01206 5348