IDI Zoology NEW SERIES, NO. 108 The Palatal Dentition in Squamate Reptiles: Morphology, Development, Attachment, and Replacement D. Luke Mahler iMaureen Kearney July 10,2006 Publication 1540 PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN BIOLOGY FIELDIANA Zoology NEW SERIES, NO. 108 The Palatal Dentition in Squamate Reptiles: Morphology, Development, Attachment, and Replacement D. Luke Mahler Department of Biology Washington University in St. Louis Campus Box 1229 One Brookings Drive St. Louis, Missouri 63130 U.S.A. Department of Zoology Field Museum of Natural History 1400 South Lake Shore Drive Chicago, Illinois 60605 U.S.A. Maureen Kearney Department of Zoology Field Museum of Natural History 1400 South Lake Shore Drive Chicago, Illinois 60605 U.S.A. Accepted December 29, 2005 Published July 10, 2006 Publication 1540 PUBLISHED BY FIELD MUSEUM OF NATURAL HISTORY BIOLOGY UBRARY 101 BURRILL HALL M 1 0 2007 © 2006 Field Museum of Natural History ISSN 0015-0754 PRINTED IN THE UNITED STATES OF AMERICA Contents Abstract 1 Introduction 2 Methods 4 Skull Preparation 4 Gross Morphology 4 Histology 4 CT Scanning 5 Materials 5 Specimens Examined 5 Abbreviations 5 Results 5 Iguanidae 8 Teiidae 8 Gymnophthalmidae 9 Lacertidae 9 Scincidae 10 Gerrhosauridae 11 Shinisauridae 11 Anguidae 11 Helodermatidae 12 Lanthanotidae 13 Alethinophidian Snakes 13 Uropeltidae 13 Cylindrophiidae 14 Aniliidae 14 Xenopeltidae 14 Boidae 15 Colubridae 15 Elapidae 16 Viperidae 16 Discussion 17 Morphology and Arrangement of Palatal Teeth 17 Development of Palatal Teeth 18 Attachment of Palatal Teeth 19 Replacement of Palatal Teeth 21 Functional Considerations 22 Phylogenetic Considerations 24 Acknowledgments 25 Literature Cited 26 Appendix. List of Specimens Examined 29 List of Illustrations 1. Distribution, arrangement, and morphology of palatal teeth in selected iguanids 36 2. Transverse sections through palatal teeth in Crotaphytus cottaris 37 3. Distribution, arrangement, and morphology of palatal teeth in selected teiids 38 4. Transverse sections through palatal teeth in Aspidoscehs tigris 39 5. Distribution, arrangement, and morphology of palatal teeth in selected gymnophthalmids 40 6. Transverse sections through palatal teeth in Gymnophthalmus speciosus 40 7. Distribution, arrangement, and morphology of palatal teeth in selected lacertids 41 8. Transverse sections through palatal teeth in Lacerta lepida 41 9. Distribution, arrangement, and morphology of palatal teeth in selected scincids 42 10. Transverse sections through palatal teeth in Eumeces fasciatus 42 11. Distribution, arrangement, and morphology of palatal teeth in selected gerrhosaurids 43 12. Transverse sections through palatal teeth in Gerrhosawus nigrolineatus 43 13. Distribution, arrangement, and morphology of palatal teeth in Shinisaurus crocodilurus 44 14. Distribution, arrangement, and morphology of palatal teeth in Ophisaurus apodas 46 15. Transverse sections through palatal teeth in Ophisaurus apodus 47 16. Distribution, arrangement, and morphology of palatal teeth in Heloderma suspectum 48 17. Distribution, arrangement, and morphology of palatal teeth in Lanthanotus borneensis 50 18. Transverse sections through palatal teeth in Lanthanotus borneensis 51 19. Distribution, arrangement, and morphology of palatal teeth in Cylindrophis ruffus 52 20. Transverse sections through palatal teeth in Cylindrophis ruffus 53 21. Distribution, arrangement, and morphology of palatal teeth in Anilius scytale 54 22. Transverse sections through palatal teeth in Anilius scytale 55 23. Distribution, arrangement, and morphology of palatal teeth in Xenopeltis unicolor 56 24. Transverse sections through palatal teeth in Xenopeltis unicolor 57 25. Distribution, arrangement, and morphology of palatal teeth in Boa constrictor 58 26. Distribution, arrangement, and morphology of palatal teeth in Coluber constrictor 59 27. Transverse section through palatal teeth in Coluber constrictor 59 28. Distribution, arrangement, and morphology of palatal teeth in selected elapids 60 29. Transverse sections through palatal teeth in Micrurus nigrocinctus 60 30. Distribution, arrangement, and morphology of palatal teeth in Agkistrodon contortrix 61 31. Transverse sections through palatal teeth in Agkistrodon contortrix 61 List of Tables 1. Occurrence and distribution of palatal teeth across extant squamate reptile groups 6 The Palatal Dentition in Squamate Reptiles: Morphology, Development, Attachment, and Replacement D. Luke Mahler Maureen Kearney Abstract The palatal dentition in squamate reptiles is poorly known compared to the marginal dentition. We surveyed species representing all squamate families for the occurrence of palatal teeth. For those exhibiting palatal teeth, we investigated palatal tooth arrangement, morphology, development, attachment, and replacement patterns using SEM, high-resolution X-ray computed tomography imaging, and histology. We found substantial variability in the presence of palatal teeth and in the arrangement and number of palatal tooth rows at familial, generic, and specific levels among nonophidian lizards. However, snakes exhibit much more uniformity in both these respects. These patterns of variability have implications for trade-offs between phylogenetic, functional, and developmental constraints. When numerous, palatal teeth in most nonophidian lizards are either arranged in fields or loosely organized rows near the back of the oral cavity. In contrast, palatal teeth in snakes and in the "lizards" Shinisaurus and Lanthanotus always occur in well-organized single rows; in snakes, these rows extend to the front of the oral cavity. Palatal teeth are usually morphologically similar to the marginal teeth, although in some cases they appear simpler. Replacement palatal teeth develop within a fold of the dental lamina that originates from the oral epithelium. In species with palatal teeth arranged in single rows, the dental lamina occurs along the labial edge of the tooth row. In others, various modifications of the dental lamina were observed that accommodate tooth replacement across multiple tooth rows or fields. Ankylosis of palatal teeth involves attachment either to the ventral surface of the tooth- bearing element or within a resorbed cavity or gutter within the element, except in some iguanids in which teeth attach to a raised ridge on the surface of the palatal bone. Tooth replacement patterns on the palate generally mirror those on the dentigerous marginal elements (i.e., labial replacement of palatal versus lingual replacement of marginal teeth), and traditionally recognized modes of tooth replacement for the marginal teeth are also observed for the palatal teeth. The strong correspondence in morphology and replacement patterns observed between marginal and palatal dentitions supports hypothesized developmental homology between them. The homology of dental tissues and tooth attachment patterns in snakes and other lizards is currently controversial. We observed plicidentine in both the marginal and the palatal teeth of varanoid lizards, but not in the teeth of snakes as has recently been proposed. In addition, snakes and the extinct mosasaurs have been suggested to share a thecodont mode of tooth FIELDIANA: ZOOLOGY, N.S., NO. 108, JULY 10, 2006, PP. 1-61 implantation. Relevant to this issue, we observed implantation of palatal teeth within resorbed cavities of varying depths in the attachment tissue or underlying bone of virtually all squamate groups. Also, an extensive buildup of attachment tissue that surrounds the teeth and prevents contact of tooth bases with each other occurs not just in snakes and mosasaurs, but also in Shinisaurus and Lanthanotus. Although palatal tooth ankylosis often occurs within a cavity, various attachment modes were observed within such cavities, generally corresponding to the attachment modes present in the marginal teeth. We conclude that tooth attachment geometry reflects, at least partially, constraints imposed by attachment to substrates of varying shapes. In other words, nearly all taxa observed exhibited some degree of "socketing" of the teeth on the palate regardless of actual attachment mode. It remains a matter for further study whether such a condition corresponds to the true thecodonty exhibited by archosaurs and mammals, which may differ fundamentally from squamate reptiles in their syndesmotic mode of tooth attachment. Certain patterns of variation in the squamate palatal dentition may be informative as potential phylogenetic characters in future studies, including patterns of tooth arrangement on the palate, varying lengths of tooth rows, tooth sizes on different palatal elements, and tooth orientation. Key Words: dentition; palatal teeth; lizards; snakes; tooth attachment; tooth development; tooth replacement. Introduction In addition to the dentigerous bones forming the margins of the jaws, some palatal bones also bear teeth in many species of squamate reptiles. Characteristics of the dentition in reptiles — including gross morphology, implantation mode, and replacement patterns — have been studied in detail (e.g., Owen, 1840-1845; Tomes, 1874, 1875; Edmund, 1960; Peyer, 1968) and have garnered renewed attention in recent years for their potential utility in inferring phylogenetic relationships among squamates (Lee, 1997a; Zaher & Rieppel, 1999; Scanlon & Lee, 2002; Caldwell et al., 2003). However, these investi- gations have focused almost exclusively on marginal teeth (but see Marx & Rabb [1972] for advanced snakes). As a result, a full un- derstanding of the squamate palatal dentition is lacking despite the fact that the palatal teeth may be informative in terms of patterns of tooth formation and development, attachment and replacement patterns, and form and function. The cursory treatment that squamate palatal teeth have received may be due to their perceived relative simplicity and obscured function com- pared to the marginal dentition (e.g., Edmund, 1969). This is not necessarily the case in other tetrapod groups. For example, Rieppel (2001) showed that crushing teeth on the palate and on some marginal bones of the primitive reptile Placodus gigas may differ in attachment and replacement pattern from other marginal teeth according to varying function. Evidence does exist for a significant role for palatal teeth across many extinct and extant groups. Palatal teeth have a history dating as far back as the origin of teeth, and have occupied a wide range of unique and independent functions and morphologies (Romer, 1956; Smith & Coates, 2000). Many fishes rely entirely on palatal teeth for dental functions (Scott & Symons, 1964). The majority of early amphibian groups possessed palatal teeth, and in the labyrinthodonts, the vomers and palatines bear highly derived tusks (Romer, 1956). Other groups, such as the champsosaurs, lacked highly specialized palatal teeth but possessed a shagreen of smaller teeth adorning the entire palatal surface (Romer, 1956). Smith and Coates (1998, 2000) decouple tooth evolu- tion and development from that of tooth-bearing elements, implying homology of pathways of tooth development regardless of where teeth occur. In light of this suggestion, it is of little surprise that palatal dentitions have been histori- cally diverse. Compared to the remarkable diversity of form and function in the palatal dentitions of fishes, amphibians, and some other tetrapods, the palatal dentition of squamate reptiles is FIELDIANA: ZOOLOGY relatively modest. However, it does exhibit morphological variability across groups and is therefore potentially informative (Marx & Rabb, 1970, 1972). Early general works on the dentition of reptiles (e.g., Owen's Odontography, 1840- 1845) depict palatal teeth for only a few squa- mate taxa. Edmund's (1969) review of reptilian dentition includes comments on the occurrence of palatal teeth in various squamate groups, but does not address arrangement or form. Likewise, Peyer (1968) mentions squamate palatal teeth only in subsidiary context to the marginal dentition, although he provides more detail for the palatal dentition of primitive reptiles. Romer (1956) summarized the occurrence of palatal teeth in reptilian groups, focusing primarily on family-level patterns of distribution. Evolutionary aspects of squamate palatal teeth have been considered by some authors (Marx & Rabb, 1970, 1972; de Queiroz, 1987; Estes et al., 1988; Lee, 1997a; Zaher & Rieppel, 1999), and features of the palatal dentition have also been used as phylogenetic characters in some studies (Etheridge & de Queiroz, 1988; Presch, 1988; Frost & Etheridge, 1989; Caldwell, 1996; Caldwell & Lee, 1997; Lee 1997b; Haller- mann, 1998; Lee, 1998; Caldwell, 1999; Lee & Caldwell, 2000; Scanlon & Lee, 2000; Lee & Scanlon, 2002). Marx and Rabb (1970, 1972) quantified variation in palatal tooth number in advanced snakes, and related trends in variation to ecological specialization and functional con- straint. The development of palatal teeth in squamates has received nominal treatment, with most researchers implicitly assuming developmental homology between palatal and marginal teeth. Indeed, tooth bud transplant experiments (Ten Cate & Mills, 1972; Ten Cate, 1976) show that tooth development relates solely to the properties of the tooth bud and that specific tooth-bearing elements play little role in the developmental process. Other researchers have implied develop- mental homology not only between marginal and palatal teeth, but also between palatal teeth occurring on different palatal bones. Estes et al. (1988) found high levels of homoplasy for characters describing the presence or absence of teeth on individual palatal bones, and concluded that palatal tooth development is highly plastic within squamates. This conclusion, combined with their observation that pterygoid teeth are present in all those squamates that have palatine teeth, and that both palatine and pterygoid teeth are present in the few squamates that have vomerine teeth, led Estes et al. (1988) to suggest that the presence of teeth on each palatal bone is the result of a single developmental field. The absence of teeth on the anterior palatal elements in many species is thus thought to result from an anterior truncation in the expression of this field. Few studies address the function of squamate palatal teeth; those that do deal mainly with higher snakes (e.g., Boltt & Ewer, 1964; Fraz- zetta, 1966; Marx & Rabb, 1970, 1972; Cundall & Deufel, 1999). These biomechanical and comparative studies describe the role of the palatal dentition in the evolution of trademark snake feeding strategies, such as lateromedial jaw transport in ophidians with moderate skull kinesis, and medial jaw transport (i.e., the "pterygoid walk") in the highly kinetic skulls of colubroids (reviewed in Cundall & Greene, 2000). Also, Marx and Rabb (1970, 1972) attribute variation in the number of palatal teeth to general cranial specializations for burrowing, capturing aquatic prey, or delivering venom. Beyond snakes, Montanucci (1968) described the palatal teeth of several iguanians in the context of their feeding modes, suggesting an important role in the oral manipulation of plant food items. The simpler palatal dentitions often found in insectivorous squamates have been suggested to aid in puncture crushing of hard prey items (Schwenk, 2000). Replacement patterns and attachment modes have been studied in some detail for the marginal teeth of squamate reptiles (e.g., Edmund, 1960, 1969). A classical distinction between varanid- type (replacement teeth developing distolin- gually, absence of resorption pits) and iguanid- type (replacement teeth developing mesiolin- gually within resorption pits) tooth replacement patterns has been recognized by many authors (McDowell & Bogert, 1954; Edmund, 1969). An intermediate-type mode for some taxa has also been proposed (Rieppel, 1978). Distinct attachment modes (e.g., pleurodonty, acrodonty) have also been extensively discussed (Romer, 1956; Edmund, 1969), yet controversy continues regarding the validity of these definitions (Os- born, 1984). Estes et al. (1988) suggested that these traditionally defined attachment modes are artificial categories, but considered most squamates to exhibit a pleurodont attachment mode. Lee (1997a) proposed that both snakes and mosasaurs (but not other lizards) exhibit a thecodont mode of tooth implantation in MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES both the marginal and the palatal elements. Zaher and Rieppel (1999) argued that the attachment mode is pleurodont in both these groups and. beyond that, is uniquely specialized in each. Caldwell et al. (2003) addressed this issue based on histology of attachment tissues, concluding that many squamate reptiles exhibit a thecodont mode of tooth attachment. These discussions have focused solely on the marginal dentitions. Replacement patterns and attach- ment modes for the palatal dentition in squa- mates are poorly known, and it is unclear whether previously described patterns (and debates about those patterns) apply equally to the palatal and marginal teeth. Here we examine the morphology, develop- ment, attachment, and replacement patterns of palatal teeth across squamates. We seek to answer the following questions: • Is the presence or absence of palatal teeth variable within currently recognized familial, generic, and specific groups? • How are palatal teeth arranged in different squamates? Are there patterns of occurrence that may be informative with respect to developmental control of tooth expression, function, or phylogenetic significance? • Does the morphology of palatal teeth closely mirror that of the marginal teeth? • Do palatal and marginal teeth show the same mode of attachment? • Are palatal teeth subject to the same re- placement patterns as marginal teeth within species? • Do patterns of the palatal dentition corre- spond closely with dietary habits and feeding behaviors? • Can the palatal dentition shed any light on current issues related to homology and phylogeny in certain groups of squamate reptiles? The study of dental morphology employs a terminology that varies over time, author, and study taxon. For simplicity and consistency, we adopt the terminology of Edmund (1969) as our primary source. Directional descriptors differ when applied to teeth versus tooth-bearing bones. The terms "medial." "lateral.** "anteri- or."" and "posterior." therefore, specify direction with respect to bones, while the terms "lingual.** "labial."" "mesial."* and "distal"" refer to corre- sponding directions on the teeth themselves. The homoloav and terminoloev of various mineral- ized tooth attachment tissues are the source of much disagreement (Osborn. 1984: Lee. 1997a: Zaher & Rieppel. 1999: Gaengler. 2000: Rieppel & Kearney. 2001: Caldwell et al., 2003). We do not attempt to resolve this disagreement here and simply refer to "attachment tissues'" as such. Methods Skull Preparation We prepared numerous skulls from alcohol- stored specimens in the collection of the Division of Amphibians and Reptiles of the Field Museum of Natural History (FMNH). Using a Leica MZ75 dissecting microscope, the skin of the head was peeled back from the underlying musculature. The hyolingual apparatus was freed from the cranium, and the latter was carefully separated from the body. Soft tissues were then removed from the cranium using fine- tipped forceps while leaving the dental lamina and developing replacement teeth intact. Skulls were then cleaned and dried. Gross Morphology Gross dental morphology was examined using different techniques according to availability, size, and preservation of specimens. We exam- ined larger specimens using a Leica MZ75 dissecting microscope with a Spot Insight digital camera attachment (model 3.2.0). For smaller specimens, we used AMR AY 1810 and Zeiss Evo60 scanning electron microscopes for exam- ination and image generation. These specimens were left uncoated and were viewed at low voltage (2 kV). For rare or precious species that were not available for preparation, we used high- resolution X-ray computed tomography (HRXCT) methods to obtain visualizations of the skull from alcohol specimens (see below). Histology We examined existing histological prepara- tions in the FMNH slide collection for some species. For most species, however, new histo- logical preparations were necessary. The heads of alcohol-stored specimens were first skinned and then removed from the bodies as described above. The heads were then decalcified, embed- FIELDIANA: ZOOLOGY ded in paraffin, and serially sectioned at 12 urn. Sections were stained with haematoxylin and eosin, mounted on slides, and then examined and photographed using a Leica DM LS2 compound microscope with a Spot Insight digital camera attachment (model 3.2.0). CT Scanning For some rare taxa, we used HRXCT studies of alcohol specimens scanned at the HRXCT Facility at the University of Texas at Austin. The resulting transverse data sets were digitally resliced along frontal and sagittal axes and rendered in three dimensions using either Vox- Blast (Vaytek, Fairfield, IA) or VGStudio Max (Volume Graphics, Heidelberg, Germany). Fur- ther scanning details and additional HRXCT imagery are available from the authors. Materials Specimens Examined We examined all squamate osteological speci- mens in the collection of the Division of Amphibians and Reptiles at FMNH. In addi- tion, we examined specimens from the osteologi- cal collections at the Museum of Comparative Zoology (MCZ) at Harvard University; the National Museum of Natural History (NMNH), Smithsonian Institution; and the Natural History Museum and Biodiversity Research Center, University of Kansas (KU). To add taxonomic scope, we hand-prepared skulls from alcohol- stored specimens at FMNH or CT-scanned them (described above). We examined hundreds of skeletal specimens representing over 900 species of snakes and other lizards. A complete list of specimens examined is given in the Appendix. Abbreviations The following abbreviations are used through- out the paper: FMNH Field Museum of Natural History KU Natural History Museum and Bio- diversity Research Center, University of Kansas MCZ Museum of Comparative Zoology, Harvard University TNHC Texas Memorial Museum, University of Texas UF Florida State Museum, University of Florida USNM National Museum of Natural History, Smithsonian Institution YPM Peabody Museum of Natural History, Yale University att attachment tissue dl dental lamina drt developing replacement tooth dt developing tooth lig attachment ligament mlg mesiolingual groove nt newer tooth ot older tooth pal palatine pic plicidentine pt pterygoid rp resorption tr tooth remnant Results All members of the following extant squamate groups have edentulous palates: Chamaeleoni- dae, Agamidae, Gekkonidae, Pygopodidae, Xan- tusiidae, Cordylidae, Anniellidae, Xenosauridae (but see character codings in Hallermann [1998] and Lee [1997b, 1998]), Varanidae, Dibamidae, Amphisbaenia, and Scolecophidia. Table 1 sum- marizes variability found for the presence or absence of palatal teeth in squamates, represent- ing our observations augmented with data from the literature. When a species is variable for the presence of palatal teeth, we indicate the nature of this variability parenthetically in the descriptions that follow, for example, (X/Y). The former number indicates the number of specimens we found that exhibited palatal teeth; the latter indicates the total number of specimens examined. We roughly follow the family level taxonomies of Cundall et al. (1993) for snakes and Estes et al. (1988) for all other squamates, with some deviations for recent updates (e.g., Lang [1991] and Frost et al. [2001] suggest separate familial treatment of cordylids and gerrhosaurids). MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES + — + +/- +/- +/- + - + — + +/- + + I) \r Gekkonidae Pygopodidae Teiidae Ameiva (n = 18 f +/- Table 1 . Occurrence and distribution of palatal teeth across extant squamate reptiles (/; = number of specimens examined: + = presence of teeth on element: - = absence of teeth on element: +/- = taxon variable for presence or absence of teeth on element). Pterygoid Palatine Vomer "LIZARDS*: Chamaeleonidae - - Agamidae - - - Iguanidae Amblvrhynchus (/; = 6) AnisolepisEDQ- FE Anolis (/; = 7)' Basiliscus (n = 16) BrachylophusEDQ FE Callisaurus (n = 5) ^ ChalarodonEDQ FE Chamaeleolis EDQ Chamaelinorops EDO Conolophus {n = 8) Cophosaurus (n - 2)EDQ Corytophanes (n = 6) Crotaphytus (n — 8)~ Ctenobl'epharusEDQ- FE Ctenosaura (n = 12) Cyclura (n = 6) Diplolaemus (n = 1)EDQ Dipsosaurus (n = 12) Envalioides (n = 9) EnyaliusEDQ- FE Gambelia (n = 7) Holbrookia (n = Hoplocercus EDQ Iguana (n — 14) Laemanctus (;/ = Leiocephalus (n = 11) Leiosaurus EXX) Liolaetmts (n = 7) Microlophus {n = 1) Morimasaurus EDQ Opiums (n = 2)4 Petrosaurus (n = 3)EDQ FE Phrvnosoma In = 13) PhvmaturusEbQ- FE P//V-a (« = 3)EDQ Pohchrus (n = \)~ PristuiactvIusEDQ FE So/or (« = 2)EDQ Sauromalus (n = 4) Sceloporus (n = 76) Stenocercus {n = 44) Tropidurus (n = 17) c>h<7(/i = 2/EDQ c>Q FE c'm (« = 7) Table 1. Continued. Pterygoid Palatine Vomer + + + + +/- +/- + + + + + + +/- + +/- + + + + +/- +/- + +/- +/- +/- +/- + +/- +/- +/- +/- +/- 47- +/- Aspidoscelis (n = 39) Callopistes (n = 1) Dicrodon Kentropyx (n = 4) 7V»« (« = 1) Tupinambis (n = 8) Gymnophthalmidae Alopoglossus (n = 2) Bachia (n = 2) Colobosaura (n = 1) Echinosaura (n — 1 ) Gymnophthalmus (n = 1 ) Neusticurus Plwlidobolus (n = 8) Proctoporus (n = 4) Tretioscincus (n = 1 ) Lacertidae Acanthodactylus (n = 1) AdolphusA AlgyroidesA GailotiaA Lacerta (n = 7)A Meroles (n = 1) Podarcis (n = 5]A Psammodromus Xantusiidae Scincidae Amphiglossus (n = 1) ApterygodonG Chalcides (n = 4) Conic ia (n = 3) Egernia (n = 2) Emoia {n — 10) Eumecia G ' Eumeces in = 20) EeyIiniaG] Gongylonwrphus ~ Isopachys (n = 6) Janetaescincus ~ La/nprolepis03, Lerista (n — 1) Lygosoma (n = 5) 3 Mabuya (n = 16) Macroscincus Melanoseps Ophiomorus (n — 2) Pamelaescincus ProscelotesG1 ScelotesGZ Scincella (n = 6) Sct>fefo.«7>sG2 Sepsina (n = 1 )G2 Sphenomorphus (n = 7) Tiliqua (n = 14) Tropidophorus (n = 10) Typhlacontias (n = 2) Typhlosaurus (n = 1)G1 + + + +/- + +/- + +/- + +/- +/- +/- +7- +/- FIELDIANA: ZOOLOGY Table 1. Continued. Table 1. Continued. Pterygoid Palatine Vomer Pterygoid Palatine Vomer Cordylidae Gerrhosauridae CordylosaurusL Gerrhosaurus (n — 5)L TetradactylusL TracheloptychusL Zonosaurus (n = 1)L Shinisauridae Shinisaurus (n — 3) Anniellidae Xenosauridae - - Anguidae Abronia (n = 1)GD - - AnguisR2 +/- - Barisia (n = 1) + - Celestus (n = 9) - - Diploglossus (n = 1)R2 - - Elgaria (n = 6) + — Gerrhonotus (n = 4)R2 +/- - MesaspisGD +/- - Ophiodes (n = 1)R2 - - Ophisaurus apodus (n — 3) + + Ophisaurus attenuatus + +/- (« = 4) Ophisaurus harti (n = 1 ) + + Ophisaurus ventralis + + (n = 1) Helodermatidae Heloderma (n = 12) +/- +/- Varanidae - - Lanthanotidae Lanthanotus (n = 2) + + Dibamidae - - AMPHISBAENIA — - SNAKES: Scolecophidia - - Uropeltidae MelanophidiumR l - + Platyplectrurus -? +? PlectrurusRi — — RhinophisRX - - Uropeltisin = 1)R1 — — Cylindrophiidae + + Aniliidae + + Xenopeltidae + + Boidae Calabar ia (n = 3) - - CharinaKL + +/- All other observed boids + + Colubridae Aparallactus (n = 2) Apostolepis3 +/- + - + +/- Atractaspis (n = 9)UK" MR Chilorhinophis (n = 2)MR Dasypeltis (n = 5)MR ElachistodonMR Lytorhynchus (n = 2)MR All other observed colubrids Elapidae Emydocephalus (n = 1)MR CalliophisMR All other observed elapids Viperidae Calloselasma (n = 1) Crotalus (n = 95) Echis (n = 8)MR Ophryacus (n — 1) Protobothrops (n = 3)MR All other observed viperids +/- +/- + — + + + + +/- + +/- + +/- + — + +/- + + A Data obtained from Arnold (1973). B Data obtained from Bell et al. (2003). EDQ Data obtained from Etheridge and de Queiroz (1988). FE Data obtained from Frost and Etheridge (1989). G1 Data obtained from Greer (1970a). G2 Data obtained from Greer (1970b). G3 Data obtained from Greer (1977). GD Data obtained from Good (1987). K Data obtained from Kardong (1990). KL Data obtained from Kluge (1993b). L Data obtained from Lang (1991). M Data obtained from MacLean (1974). MR Data obtained from Marx and Rabb (1970, 1972). R1 Data obtained from Rieppel (1977). R2 Data obtained from Rieppel (1980). UK Data obtained from Underwood and Kochva (1993). 1 We observed pterygoid teeth in five out of seven specimens of Anolis, corroborating Etheridge and de Queiroz (1988), who indicate variability in this genus. Frost and Etheridge (1989) report the presence of palatine teeth in Anolis, and Etheridge and de Queiroz report absence for the same character. In our survey, we find the character to be polymorphic at the genus level. 2 Etheridge and de Queiroz (1988) scored Crotaphytus as possessing palatine teeth uniformly. We observed this trait to be highly variable. 3 We observed palatine teeth in Laemanctus, but Etheridge and de Queiroz (1988) and Frost and Etheridge (1989) reported them to be absent in this genus. 4 We observed only pterygoid teeth in two specimens of this genus, but Etheridge and de Queiroz (1988) report the palatines to be variable as well. 5 We observed pterygoid teeth in a single specimen. Etheridge and de Queiroz (1988) observed pterygoid teeth to be variable in a larger sample. 6 Presch (1974) reports the presence of pterygoid teeth in Ameiva ameiva and A. bifrontatci. Based on different results in our survey, the genus Ameiva and the species A. ameiva are variable for pterygoid teeth. 7 Cundall and Greene (2000) report a simple palatal dentition in Platyplectrurus but do not indicate which bones in the palate possess teeth. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES Iguanidae Pterygoid teeth are very common in iguanids. whereas palatine teeth are less common and vomerine teeth are completely absent (Table 1). At the generic level. 12/36 taxa with palatal dentition are polymorphic for pterygoid teeth. We found variability at the specific level for the presence of pterygoid teeth in Anolis cristatellus (1/2), Conolophus saber ist at us (3/8). Cyclura cornuta (5/6), Dipsosaarus dorsalis (2/11). Leio- cephalus carinatus (1/4). Stenocercus chrysopygus (1/2), Stenocercus empetrus (2/3), and Stenocer- cus varius (1/4). Palatine teeth are found uni- formly in 1/12 iguanid genera that express them and variably in 1 1/12. Presence of palatine teeth varies intraspecifically in Crotaphytus collar is (1/ 8) and in Gambelia wislizenii (3/4). Iguanid palatal teeth are typically arranged in loosely organized rows (Fig. 1). In many speci- mens of Iguana, Basiliscus, Crotaphytus, Cteno- saura, and Cyclura, one row of pterygoid teeth is flanked by a second more medial row, which may be complete (Fig. 1C) or incomplete (Fig. ID) (see also Montanucci. 1968; de Queiroz. 1987). Orientation and shape of the tooth row vary. In Iguana, the straight tooth row is oriented diagonally relative to the long axis of the skull, and its anterior extent corresponds roughly to the posterior extent of the marginal tooth row. In other taxa, such as Brachylophus, Ctenosaura, Cyclura, and Sauromalus, the pos- teriormost section of the tooth row curves laterally to depart from the medial edge of the pterygoid (de Queiroz. 1987) (Fig. 1A, D). In some Ctenosaura, the laterally curving tooth row curves back toward the midline posteriorly, forming a medially open arc (Fig. IB). Except for those taxa in which the posteriormost section of the tooth row curves laterally, tooth rows are usually located along the extreme medial edge of the pterygoid body. Iguanid palatal teeth are generally conical and range from short and blunt (Basiliscus basiliscus, Plica plica) to elongate, pointed, and mildly curved (Ctenosaura similis). Although Edmund (1969. p. 154) described iguanian palatal teeth as "always small and never very numerous,'" the palatal teeth of some iguanids are numerous (>70 per pterygoid in some Iguana iguana) and may exhibit a complex morphology in some species. For example, the palatal teeth of Crotaphytus collaris are beveled, and those of Ctenosaura similis are flattened at the tips and multicuspate (Fig. IE), similar to the morphology seen in the marginal teeth (Fig. IF). This morphology is most evident in the immature, developing replacement teeth, whereas the mature palatal teeth tend to exhibit a slightly simpler shape. The palatal teeth of iguanids usually attach obliquely to the pterygoid or palatine. In Crotaphytus collaris, histological sections show the presence of a shallow channel in the ventral lamellar surface of the pterygoid bone, pre- sumably created through resorption (Fig. 2). The teeth are ankylosed within this channel, affixed with a substantial amount of attachment tissue. In other taxa. such as Iguana and Ctenosaura, attachment tissues play a bigger role in de- termining the geometry of the attachment site, with a large buildup of attachment tissue occurring on the pterygoid, that creates a pro- nounced ridge to which side of the tooth attaches. In contrast to the pleurodonty seen in the marginal dentition for all iguanians. the geometry of palatal tooth attachment varies. In some species, the palatal teeth within the resorbed cavity attach lingually to the medial wall of that cavity in a reclined position. In others, the side of the palatal tooth attaches to a ridge composed of attachment tissue, resulting in a more upright orientation. In all iguanids. the palatal teeth are replaced in the same manner as the marginal teeth (i.e.. the "iguanid replacement mode" of Edmund. 1960). Tooth germs develop in a dental lamina that extends the length of each tooth row along the bases of the functional teeth. In those taxa with a single pterygoid tooth row (e.g.. Basiliscus). the replacement teeth develop labially (the mirror image of replacement of the marginal teeth). In those with a double pterygoid tooth row (e.g.. Ctenosaura. Iguana), the re- placement teeth develop along the lingual side of the medial row and along the labial side of the lateral row. From these positions, the replace- ment teeth migrate into resorption cavities in the bases of the functional teeth at an early stage (Figs. ID. E: 2C. D). Teiidae Our survey of teiids revealed pterygoid teeth to be present (but neither numerous nor well developed) in Callopistes, Aspidoscelis. and Teius (Table 1). MacLean (1974) additionally reports pterygoid teeth in Dicrodon. We found the presence of pterygoid teeth to be variable in Ameiva (1/18) and Kentropyx (3/4) and absent in FIELDIANA: ZOOLOGY all eight observed specimens of Tupinambis. We observed A. ameiva (1/4) and K. calcarata (3/4) to be intraspecifically variable for the presence of pterygoid teeth (Presch [1974] also reports the variable presence of pterygoid teeth in K. calcarata). No teiids were found to possess palatine or vomerine teeth. In teiids, pterygoid teeth typically form an extremely short row along the medial margin of the pterygoid (Fig. 3 A). In most species exam- ined, the pterygoid teeth are attached to the ventral surface of the pterygoid and point ventrally; however, in a few species, the teeth on each pterygoid point toward the midline of the skull because they are affixed to the inner edge, rather than the ventral surface, of the pterygoid. Unlike the condition in iguanids, the anterior extent of the pterygoid tooth row in teiids is well posterior to the posterior extent of the marginal tooth row. Pterygoid teeth in teiids are typically small and conical (Fig. 3B) and are generally morpholog- ically simpler than the often beveled or cusped marginal teeth. However, a few individuals of Aspidoscelis were found to exhibit a small cusp on the pterygoid teeth (Fig. 3D), similar to that seen in the marginal teeth (Fig. 3E). The pterygoid teeth in teiids attach within a shallow gutter resorbed in the ventral surface of the pterygoid (Fig. 3B, C). Attachment geometry varies. Usually, the teeth are attached along their basal and lingual surfaces with a minimum of attachment tissue (Fig. 4C, D), similar to the pleurodont attachment mode seen with the marginal teeth. Attachment may some- times be more symmetric, however (Fig. 3C). Replacement teeth develop inside resorption pits that lie mesiolabial or labial to the functional pterygoid teeth. Unlike in iguanids, immature replacement teeth are sometimes observed in the absence of the corresponding functional tooth, suggesting possible early loss of the functional tooth during the process of replacement (e.g., Kentropyx calcarata, Fig. 3C; Aspidoscelis tigris punctilineatus, Fig. 4A, B). Gymnophthalmidae Bell et al. (2003) recently described the absence of palatal teeth in a large survey of Neusticurus ecpleopus, a species they considered representa- tive of the family Gymnophthalmidae. In a larger work on teiids and gymnophthalmids, MacLean (1974) described pterygoid teeth only in Gym- nophthalmus speciosus, which also suggests that palatal teeth are uncommon in this family (Table 1). In the single dry skull available to us for observation for Gymnophthalmus speciosus, two to three very small teeth are present on each pterygoid. Two specimens of Bachia lack palatal teeth. Our observations of cleared-and-stained material and CT data for other taxa indicate that Alopoglossus angulatus, Colobosaura modesta, and Tretioscincus bifasciatus possess one to two teeth on each pterygoid, and that Ecbinosaura, Pholidobolus, and Proctoporus lack palatal teeth. Additional specimens were unavailable for assessing variability in this family comprising 36 genera (Pellegrino et al. 2001). In Gymnophtbalmus speciosus and Colobosaura modesta, two or three small teeth form a short transverse row on the central body of the triradiate pterygoid (Fig. 5). Unlike in iguanids or teiids, the pterygoid teeth in these gym- nophthalmids are not positioned along the medial margin of the ptergyoid; instead they occur at the base of the transverse process of the ptergyoid. These teeth are stout, conical, and slightly compressed, similar in form to the marginal teeth (Fig. 5C). The pterygoid teeth of Gymnophthalmus spe- ciosus are ankylosed within a wide depression in the ventral surface of the pterygoid (Figs. 5B; 6), and the teeth attach to the wall of this cavity via a small amount of attachment tissue (Fig. 6). Although replacement mode is not evident from histological sections, resorption cavities contain- ing immature teeth may be seen developing mesiolingual to functional teeth in a prepared skull (Fig. 5B, C), suggesting either an interme- diate-type (Rieppel, 1978) or an iguanid-type (Edmund, 1960) mode of replacement. Lacertidae As noted by Arnold (1973), palatal teeth are common in lacertids and occur solely on the pterygoids (Table 1). Arnold (1973) indicates that Gallotia possesses pterygoid teeth uniformly and that Algyroides, Lacerta, Podarcis, and Psammodromus are variable for this trait (the species reported to possess pterygoid teeth in these genera are Algyroides moreoticus, A. nigropunctatus, Lacerta agilis, L. lepida, L. princeps, L. brandtii, L. dugesii, L. jayakari, L. laevis, L. schreiberi, L. strigata, L. trilineata, L. viridis, Podarcis milensis, P. peloponnesiaca, P. taurica, and Psammodromus algirus). Our survey, MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES though taxonomically restricted, revealed uni- form presence of pterygoid teeth in all examined specimens of Lacerta (L. lepida and L. viridis) and a single specimen of Meroles (M. anchietae). It also indicated variable presence of pterygoid teeth in Podarcis. Within Podarcis, we observed pterygoid teeth in single specimens of P. lilfordi and P. taurica and found pterygoid teeth to be variable in P. sicula (1/3). In addition, Arnold (1973) reported the presence of pterygoid teeth to vary intraspecifically in Algyroides moreoticus and A. nigropunctatus. Lacerta exhibits an unusual palatal tooth arrangement. In Lacerta lepida, for example, an uneven row of teeth runs anteroposteriorly near the middle of the pterygoid. Medial and postero- medial to this row, smaller teeth are scattered in subparallel rows, extending all the way to the medial edge of the pterygoid (Fig. 7B). These rows are less prominent than the primary lateral row; the teeth are fewer, smaller, and appear to be heavily embedded in a large buildup of attachment tissue. The most postero- medial teeth appear nearly completely degraded (either through partial resorption or wear). The lateral row, on the other hand, is more continuous and consists of larger teeth that are generally fully intact. The pterygoid teeth in Lacerta are stout at their base and become constricted below the tip, terminating in a blunt knob with a chiseled edge (Fig. 7C). This morphology approximates the form of the marginal teeth. Both marginal and palatal teeth in Lacerta exhibit a mild curvature (labial curvative of palatal teeth, lingual curva- ture of marginal teeth). The teeth are affixed within a gutter in the ventral surface of the pterygoid (Figs. 7C; 8A), ankylosed with small amounts of attachment tissue (Fig. 8B). Both basal and lingual surfaces of the tooth attach to the pterygoid, creating a pleurodont appearance (Fig. 7C). Developing replacement teeth, embedded in the dental lamina, are observed labial to the functional teeth in histological sections (Fig. 8A), and migrate into resorption pits in the mesiolabial surface of the functional tooth base (Fig. 7C). The presence of additional degraded rows of pterygoid teeth medial to the primary lateral row in L. lepida suggests that older teeth may migrate medially across the pterygoid rather than being lost during the replacement process. Such a migration would involve a reworking of underlying bone and attachment tissues, as described by Ricqles and Bolt (1983) for the primitive reptile Captorhinus aguti. Scincidae Presence of pterygoid teeth (no scincid pos- sesses palatine or vomerine teeth) is variable among scincids (Table 1) and has been used as a key character to inform the phylogenetic relationships within this group (Greer, 1970a). Among scincids, all available specimens of Corucia, Eumeces, Ophiomorus, and Sepsina uniformly possess pterygoid teeth. In addition, Greer (1977) notes the uniform presence of ptergyoid teeth in Dasia and Eumecia. We found variability in the presence of pterygoid teeth in Mabuya and Tropidophorus. Greer (1977) reports variability in the presence of pterygoid teeth for Lygosoma based on examination of 19 species, reporting that 5 species possess them and 14 uniformly lack them. Tropidophorus brookei (2/4) was the only scincid examined in our survey that showed intraspecific variation in the expression of pterygoid teeth, although Greer (1977) notes a similar condition in Lygosoma punctata. Scincid palatal teeth are usually loosely ar- ranged in a short to moderate single row of longitudinal orientation on the pterygoid (Fig. 9A), although this row is transversely oriented in Sepsina (Greer, 1970b) and Lygosoma (Greer, 1977). Some specimens of Eumeces fasciatus exhibit additional teeth out of line with this primary row (Fig. 9B). The tooth row typically does not traverse the medial margin of the pterygoid but is located a short distance away from this edge (Fig. 9A). Palatal teeth in most scincids exhibit broad bases and conical tooth crowns (Fig. 9B), morphologically similar to the fairly simple marginal teeth seen in most species. In taxa where the marginal teeth exhibit more morpho- logical complexity, the palatal teeth roughly approximate this condition. For example, Cor- ucia zebrata, an herbivorous scincid with spatu- late marginal teeth (Fig. 9D), exhibits a similar flattening of the pterygoid tooth tips (Fig. 9C), although the resemblance is not exact. Histological sections of Eumeces fasciatus show pterygoid teeth implanted within a deeply resorbed cavity in the pterygoid (Fig. 10A; see also Fig. 9B). Attachment occurs through a sub- stantive deposition of attachment tissue at the base and side of the tooth. Tooth replacement occurs as in the iguanid mode: new teeth develop 10 FIELDIANA: ZOOLOGY within a dental lamina that is positioned along the labial side of the functional teeth (Fig. 10B) and migrate to occupy basal resorption pits within the bases of the functional teeth (Fig. 9B). Gerrhosauridae Although we were unable to perform extensive sampling within Gerrhosauridae ( 1 Gerrhosaurus flavigularis, 1 G. nigrolineatus, 3 G. validus, 1 Zonosaurus ornatus), Lang (1991) reports the presence of palatal teeth on the ptergyoids in all gerrhosaurid genera (Cordylosaurus, Gerrho- saurus, Tetradactylus, Tracheloptychus, and Zo- nosaurus) except the monotypic Angolosaurus (data unknown). Our observations indicate the presence of pterygoid teeth in all sampled taxa. The pterygoid teeth are arranged either in a single straight row that is oriented diagonally relative to the long axis of the skull (Fig. 1 1 A) or sometimes in a single curving row. Curving rows turn laterally and then return toward the midline to form a slight arc that is open medially (Fig. 11C). Tooth orientation may vary along the row, with several teeth pointing in different directions (Fig. 11C); this seeming disorganiza- tion within a tooth row is mirrored closely in the opposite row. In Gerrhosaurus, the pterygoid teeth are short and slightly curved at the tip. The tooth bases are broad, and the tips of the crowns are flattened to form wedges (Fig. 1 IB). Both of these conditions are similar to the conditions seen in the marginal teeth (Fig. HE). In the case of the marginal dentition, the bases are broad- ened and the tips flattened mesiolingually. However, the orientation of the pterygoid teeth differs from that of the marginal teeth, with the flattened tips and the broadened bases occurring in a diagonal plane. The flattened tips of the ptergyoid teeth also bear striations in some species (Fig. 11D) that mirror those seen in the marginal teeth (Fig. HE). One individual of G. validus (FMNH 22293) exhibited rudimentary cusps on the pterygoid teeth, though they were far less differentiated than those of the marginal teeth (Fig. 11D, E). The teeth of Gerrhosaurus are ankylosed within an excavation in the ventral surface of the pterygoid (Fig. 12). They are fastened at the base and sides via moderate to large amounts of attachment tissue. The tooth attachment site bears evidence of frequent and imprecise re- sorption and redeposition of attachment tissue. Some sections show new functional teeth affixed to partially eroded teeth and to masses of old attachment tissue. New teeth develop within basal resorption pits that receive tooth buds from the dental lamina. Histology indicates that this replacement may occur lingually (Fig. 12A) as well as labially (Fig. 12B), although only labially replacing teeth were observed on skeletal material, and this could be anomalous. Shinisauridae Palatal teeth are found only on the pterygoid in Shinisaurus crocodilurus (Conrad, 2004). The teeth are arranged in a well-organized, longitu- dinal row within a cavity that courses along the medial edge of the pterygoid (Fig. 13). The teeth are widely spaced throughout this row (Fig. 13B, C) in contrast to the crowded palatal tooth rows seen in most nonophidian lizards. The pterygoid teeth of Shinisaurus are conical, pointed, slightly recurved, and fairly tall, similar to the morphol- ogy of the marginal teeth. Each pterygoid tooth has an expanded base that is affixed perpendicularly to the pterygoid via a buildup of attachment tissue (Fig. 13B). The walls of the pterygoid cavity are higher medially than laterally (Fig. 13C), but the sides of the teeth nonetheless do not attach to this wall. They are instead ankylosed solely at their bases with attachment tissues completely surrounding the base of each tooth (Fig. 13B, C), precluding direct contact of the tooth bases with each other or with the walls of the cavity. Histological preparations of Shinisaurus were unavailable. The replacement mode of the pterygoid teeth in Shinisaurus is somewhat obscure. None of the specimens we observed exhibited resorption cavities in the pterygoid teeth; however, these are visible in the marginal teeth and indicate an intermediate-type mode of tooth replacement. In addition, we observed some instances of imma- ture teeth occupying several tooth positions along the ptergyoid tooth row. Anguidae The Anguidae contains species that possess teeth on the pterygoids, palatines, and vomers (Table 1). Pterygoid teeth were observed in all specimens of Elgaria, Ophisaurus, and the single available specimen of Barisia (Good [1987] describes this genus as uniformly possessing pterygoid teeth). Also, pterygoid teeth were MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 11 found variably in the genus Gerrhonotus, and Rieppel (1980) has described variability in the pterygoid teeth of Anguis. We found variable presence of palatine teeth in Ophisaurus and intraspecific variability in O. attenuatus (3/4). Vomerine teeth were observed only in O. apodus (2/3). In every specimen exhibiting palatine teeth, pterygoid teeth are also present: likewise, speci- mens with vomerine teeth always possess both palatine and pterygoid teeth. The palatal teeth are either arranged in a single row (e.g.. Ophisaurus attenuatus and O. harti) or in multiple uneven rows (subparallel rows of Ed- mund. 1969) on each palatal element (e.g.. Elgaria. O. ventralis, and O. apodus) (Fig. 14). We observed a single row of teeth on each pterygoid in Gerrhonotus. but Good (1987) illustrates a speci- men of G liocephalus that possesses multiple rows. In some specimens of O. apodus. numerous palatal teeth appear to form a long but disjunct secondary tooth row extending from the middle of the vomer anteriorly to the posterior region of the pterygoid body: in others, the teeth are poorly developed or absent on the vomer. Even in those species with well-developed teeth on all three elements, how- ever, a continuous (uninterrupted) row such as that seen in higher snakes is not present. Typically, the vomer bears a single uneven row. the palatine may bear an incomplete second row. and the pterygoid may bear multiple uneven rows. Anguid palatal teeth are short, blunt cones with broad bases (Fig. 14C). They closely resemble the marginal teeth in shape but are comparatively diminutive. Size and shape of the teeth are often inconsistent along the palatal tooth row. On the pterygoid of Ophisaurus apodus. for example, larger teeth in the lateral position are bordered medially by a somewhat random scattering of smaller teeth that point in different directions (Fig. 14D). Likewise, some anterior teeth on the palatine of a specimen of O. apodus appear as large, stout cones, while those more posterior appear somewhat smaller and distorted in shape (Fig. 14C). Palatal teeth are attached within fairly deep cavities in the palatal elements of anguids (Fig. 15). The role of attachment tissues varies: at some attachment sites, old tooth remnants and attachment tissues have undergone incomplete resorption and seemingly comprise the founda- tion for new teeth (Fig. 15D). Edmund (1969) stated that tooth replacement in anguids pro- ceeds without tooth resorption, that is. with replacement teeth developing distolingual to the functional teeth but with no resorption pits observed. However. Cooper (1966) and Rieppel (1978) describe tooth replacement in anguids as involving resorption of the tooth base around the alveolar foramen to house the growing replace- ment tooth (Rieppefs "intermediate mode" of tooth replacement). These studies were restricted to the marginal dentition. For the palatal dentition, replacement teeth develop within an infolding of dental lamina that originates from oral epithelium along the ventrolateral surface of the palatal bone and extends across the tooth rows (Fig. 15B-D). Developing teeth were found to cause incomplete resorption of old teeth (Fig. 15D). similar to the process described by Cooper (1966) and Rieppel (1978) for the marginal dentition. Once the functional tooth has been shed, the replacement tooth migrates dorsally from the dental lamina to achieve ankylosis. Helodermatidae Teeth are uniformly present on the pterygoids of Heloderma horridwn and variably present in H. suspeetum (contra McDowell and Bogert [1954]. who report absence in H. suspeetum). Teeth are also present on the palatines of H. horridwn but not H. suspeetum. In H. suspeetum. teeth are typically found in a short longitudinal row centered on the body of the pterygoid, just posterior to the palatine-pterygoid suture (Fig. 16A. B). In H. horridwn. this row continues anteriorly onto the palatine, where one to a few teeth are present. Tooth orientation varies markedly along the row. with teeth pointing in several different directions (Fig. 16B). The palatal teeth of helodermatids are conical and distinctly curved, with stout bases (Fig. 16B). As with the marginal teeth (Fig. 16D). the pterygoid teeth exhibit strong dentine infoldings at the base of the crown (Fig. 16C): however, unlike the marginal teeth, they lack venom grooves. The pterygoid teeth in Heloderma attach directly to the flat ventral pterygoid surface. Although individual teeth create a shallow cavity in the pterygoid bone at the site of attachment, the tooth row in Heloderma does not sit within a continuous depression or gutter (Fig. 16B. C) as it does in teiids and Shinisaurus. for example. Although histological preparations were not available for Heloderma. some observations re- garding replacement pattern were possible from skeletal specimens and CT scans. Palatal teeth i: FIELDIANA: ZOOLOGY develop mesial or mesiolabial to their corre- sponding functional teeth; this is in contrast to the distolingual position of the replacement teeth in the marginal bones. Replacement palatal teeth in Heloderma do not develop within resorption cavities, but rather migrate into position once an older functional tooth has been shed (Fig. 16B, second tooth from right). Lanthanotidae Our observations of Lanthanotus borneensis confirm the presence of palatal teeth on the pterygoid and palatine bones (McDowell & Bogert, 1954). The palatal teeth are arranged in an evenly spaced, mildly curved row along the medial edge of the pterygoid and extend anteri- orly onto the palatine for a short distance (Fig. 17A, B). This row is continuous from the posterior portion of the palatine to the posterior extent of the pterygoid body, interrupted only by a short diastema at the suture of these elements. The shape of the pterygoid-palatine tooth row as a whole is a shallow arc that opens medially; the tooth row follows the curve of the medial aspect of the pterygoid and palatine bones. The palatal tooth row does not overlap the marginal tooth row but occurs more posteriorly on the palatal surface. CT data for Lanthanotus indicate that the palatal teeth in this species are small, conical, and slightly recurved. Palatal teeth were largely missing in the skeletal specimens we observed, but some tooth bases were present for observa- tion (Fig. 17B, C). The base of each tooth is cylindrical, and a large alveolar foramen pierces the attachment tissue and the base of the tooth mesiolingually, where the tooth meets the ptery- goid (Fig. 17C). Dentine infoldings were not observed externally at the tooth bases, although these would be difficult to detect given the quality of the teeth present on these specimens. Histological sections indicate the presence of plicidentine at the bases of the palatal teeth in Lanthanotus (Fig. 18B, C). Palatal teeth in Lanthanotus are ankylosed within a longitudinal depression in the ventral surface of the ptergyoid. Within this depression, copious amounts of attachment tissue anchor the teeth and fill the remaining spaces around the teeth (Figs. 17C; 18C). This differs from the attachment of the marginal teeth, which exhibit a typical varanoid type of specialized attachment (Kearney & Rieppel, in press). When teeth are shed, the attachment tissue exhibits a superficially "socketed" appearance, with interdental ridges formed of attachment tissue occurring between tooth attachment sites (Fig. 17D). Zaher and Rieppel (1999) report labial re- placement of the palatal teeth in Lanthanotus. Through histology, we confirm labial replace- ment in the pterygoid teeth of Lanthanotus (Fig. 18B, C), but also observed lingual re- placement in the palatine teeth of the same specimen (Fig. 18A). Alethinophidian Snakes Among alethinophidian snakes (no scoleco- phidians have palatal teeth), the morphology of palatal teeth generally mirrors that seen in the marginal teeth. The arrangement and replace- ment patterns are far more conservative than those seen in lizards, being much the same throughout the entire group, and we therefore discuss these as a whole here. Typically, teeth are arranged in a single, straight row that extends posteriorly from the anterior portion of the palatine, across the palatine-pterygoid suture, and sometimes along the quadrate ramus of the pterygoid (Table 1). While nearly all alethinophi- dians exhibit continuous palatal tooth rows, the number of teeth found on the palatine and pterygoid elements of advanced snakes (colub- roids) is quite variable (discussed in detail in Marx and Rabb, 1972). Teeth are generally attached to the palatal bones perpendicularly via a large buildup of attachment tissue and are always replaced labially, mirroring the lingually replaced teeth of the marginal tooth-bearing bones (Lee, 1997a). As with the marginal dentition, replace- ment palatal teeth always develop in a recumbent position and rotate into an upright position when fully developed, migrating into position once the functional tooth is shed. Very few snakes deviate significantly from these patterns; thus, while palatal tooth morphology and attachment will be described for all alethinophidian snake groups, arrangement and replacement will be described only when exceptional. Uropeltidae Skeletal material for most uropeltid snakes was unavailable. However, CT imagery of Uropeltis melanogaster indicates the absence of palatal teeth. Rieppel (1977) describes three small teeth in each palatine in Melanophidium MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 13 punctatum but reports teeth to be absent in M. wynaudense as well as in Uropeltis brevis, U. ocellatus, Rhinophis, and Plectrurus. Cundall and Greene (2000) also report a simple palatal dentition in Platyplectrurus, citing Smith (1943). Complete absence of palatal teeth is extremely rare in alethinophidian snakes but occurs with unusual frequency in uropeltids. Cylindrophiidae The palatal teeth of cylindrophiids are very similar morphologically to their marginal coun- terparts. They are stout, recurved, and conical, with heavily built bases (Fig. 19). Tooth size changes from anterior to posterior in the palate: the anteriormost teeth are moderate in size, giving way to smaller teeth more posteriorly (Fig. 19 A). This is not the case with the marginal teeth, which are of uniform size. The palatal teeth are ankylosed with an extensive buildup of attachment tissue lining a deep excavation running the length of the ventral surface of the palatal elements. The walls of this excavation are uneven in height, with the lingual wall being higher than the labial (Figs. 19 A: 20B). The palatal teeth attach to the walls of this excavation by the base and both sides (Fig. 20 A). The bases of the palatine teeth, but not the pterygoid teeth, incline slightly medially (Figs. 19A; 20). Aniliidae The palatal teeth of Anilius are very similar in shape to the marginal teeth but are comparatively smaller ( Fig. 2 1 ). The palatine teeth are larger, less numerous, and more widely spaced from each other than are those on the pterygoid. These changes in size and spacing are not gradual, occurring abruptly at the junction of the two elements (Fig. 21 A). The palatal teeth are fairly short, strongly recurved, and have a well-de- veloped carina on lingual and labial edges (Fig. 21C). On some palatal teeth, weak striations are apparent at the base (Figs. 21C; 22): these are more pronounced in the marginal teeth and seem to reflect impressions of overlying bone of attachment (Kearney & Rieppel. in press). The palatal teeth of Anilius are ankylosed within a gutter nearly as wide as the narrow palatal elements themselves. This gutter is lined with attachment tissue, which serves as a foun- dation into which the palatal teeth attach (Figs. 21C; 22). The tooth bases are separated from each other by extensively developed attach- ment tissue. Shed teeth reveal the extent to which the teeth are implanted within the attachment tissue (Fig. 2 IB). Attachment tissues cover the very base of the tooth externally and also invade the tooth cavity to cover the internal surface of the tooth base (Figs. 21C: 22B). Xenopeltidae Xenopeltids have a unique dentition (Figs. 23; 24). The shape of the palatal teeth mirrors the spatulate morphology seen in the marginal teeth — the teeth are anteroposterior^' compressed, pro- viding flat mesial surfaces (Figs. 23B; 24A). Our observations indicate that the palatal teeth in xenopeltids are larger than the marginal teeth, a unique condition among squamates. In some specimens, the palatal teeth appear to be at least twice as large as those on the marginal bones. This condition may bear further scrutiny within a func- tional context. The palatal teeth are not uniform in size but gradually decrease in size posteriorly (Fig. 23A). Tooth attachment in Xenopehis employs a unique ligamentous structure that allows the teeth to fold posteriorly under pressure during feeding. This condition has been described explicitly for the marginal dentition (Savitzky. 1981: Cundall & Greene. 2000), and our results show that the same type of attachment also occurs with the palatal teeth (Fig. 24C). The palatal bones are deeply excavated at the sites of tooth attachment (Fig. 24). The walls of the resultant cavity are tall and of roughly even height. Ligaments extend from the tooth base to the insides of these walls but not to the floor of the cavity, anchoring the tooth to the palatal bone in a manner that allows folding. Replacement teeth lie in a recumbent position within the dental lamina occurring labial to the bases of the functional teeth, and extending the length of the tooth row (Figs. 23C: 24B). Savitzky (1981) reported that all functional tooth positions in Xenopehis are occupied simulta- neously by teeth of the same size and suggested a unique, fully synchronous replacement scheme for this taxon. However, examination of our CT data (Fig. 23A) and some dried skulls (Fig. 23C) contradicts this. In both marginal and palatal dentitions, we observed several empty tooth positions along the tooth rows as well as replacement teeth in various stages of develop- ment and of various sizes. 14 FIELDIANA: ZOOLOGY Boidae We observed palatal teeth on both the pterygoids and palatines of all boids examined, except for the erycine Calabaria reinhardtii, which uniformly lacks palatal dentition, and Charina bottae, which occasionally lacks palatine teeth (Kluge, 1993b). The palatal teeth of boids are morphologically similar to the marginal teeth; they are long, recurved, sharp cones similar in size to those occurring on the marginal bones (Fig. 25). In most boids, the more anterior palatal and maxillary teeth exhibit "reverse curvature," where the tooth is S-shaped, facili- tating penetration during prey snaring (Cundall & Deufel, 1999; Deufel & Cundall, 1999). Tooth size may vary within the palatal tooth row. As reported by Kluge (1993a), in many pythonines, the anteriormost teeth of the palatine are significantly larger than teeth on the remainder of the palatine and on the pterygoid. We observed this difference in size to be most pronounced in Chondropython viridis and Mor- elia amethistina and found the transition in tooth size to be more gradual in other boids. The posterior reduction in tooth size is concordant between the palatal and marginal tooth rows. In addition, the pterygoid teeth tend to point posteromedially, whereas the palatine teeth point posteriorly (Fig. 25A). The line of demarcation between posteriorly oriented teeth and postero- medially oriented teeth on the palate again corresponds to a similar transition in orientation for the marginal teeth. The bases of the palatal teeth are slightly ovoid and attached within a deep palatal groove lined with attachment tissue (Fig. 25B, C). The tooth bases are not in contact, separated by interdental ridges com- posed of attachment tissue. No histological preparations were available for boids. Colubridae Colubrids typically possess teeth on the palatine and pterygoid, but the egg-eating Dasypeltis and Elachistodon lack pterygoid teeth (Gans, 1952; Marx & Rabb, 1970, 1972), as do some atractaspids (e.g., Aparallactus werneri, Atractaspis bibroni, A. dahomeyensis, A. irregu- laris, A. microlepidota, and Xenocalamus bicolor), Apostolepis ambiniger (Underwood & Kochva, 1993), and Lytorhynchus paradoxus (Marx & Rabb, 1972). Underwood and Kochva (1993) also note a lack of pterygoid teeth in Chilorhi- nophis, but we observed them to be present in C. carpenteri. No colubrids were observed to lack palatine teeth, although observations were in- conclusive for some Atractaspis specimens. In contrast to other alethinophidian snakes (Figs. 19A; 21 A; 23 A; 25 A), the palatal tooth rows in colubrids are typically greatly elongated, often twice as long as the marginal tooth rows (see Marx and Rabb [1972] for discussion of exceptions). In Coluber constrictor, for example, the palatal tooth row extends posteriorly almost the entire length of the quadrate ramus of the ptergyoid (Fig. 26A). In the anterior portion of the palatal tooth row, the teeth point posteriorly; more posteriorly along the row, they point posteromedially. This transition is similar to the condition we observed in boids. Palatal teeth in colubrid snakes are generally elongate, conical, and sharply recurved (Fig. 26). Some, such as those of Coluber constrictor, show a pronounced carina on the lingual and labial edges leading to the tip of the crown (Fig. 26B), a condition also seen in the marginal teeth. Vaeth et al. (1985) describe accessory longitudinal fluting mainly on the posterior surface of both the marginal and the palatal teeth of many piscivorous colubrids (variably present in the genera Afronatrix, Amphiesma, Cereberus, Dip- sas, Erpeton, Homalopsis, Enhydris, Heurnia, Helicops, Macropisthodon, Natrix, Nerodia, Par- eas, Sibon, Sibynomorphus, Sinonatrix, Tetranor- hinus, and Thamnophis). In specimens of these taxa observed in our survey, the degree of fluting on the marginal and palatal teeth was very similar. Differences between the marginal and palatal dentitions exist, however, in the hetero- dontous colubrids (taxa that exhibit variation in size, shape, and continuity in the marginal tooth row) and in the monospecific genera Pythono- dipsas and Bitia. In heterodontous colubrids, the palatal tooth row consists of teeth of uniform shape, continuous arrangement, and consistency of size, even when the maxillary and dentary teeth exhibit multiple tooth shapes, diastemas along the tooth row, and pronounced size heterogeneity (e.g., Heterodon, Xenodon, and Lycodon). Although palatal teeth were often seen to decrease in size posteriorly in these taxa, this transition was observed to be gradual rather than abrupt (contra the condition seen in many boids and elapids). As exceptions to this pattern, the enigmatic colubrids Bitia hydroides and Pytho- nodipsas carinata exhibit pronounced heteroge- neity in tooth size and spacing within the palatal MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 15 tooth rows. In Bitia, the third palatine tooth is markedly larger than others in the tooth row. The viper-like Pythonodipsas possesses a large, ungrooved fang on the anterior palatine, sepa- rated from the remaining palatine teeth by a short diastema (Marx & Rabb, 1970; Marx et al.. 1982). This morphology is relatively unique among snakes, although the pythons Chondropy- thon viridis and Morelia amethistina also possess distinctly enlarged anterior palatine teeth. In most colubrids we examined, the palatal teeth are somewhat smaller than the marginal teeth despite an overall similarity in form and ar- rangement (Fig. 26A). Palatal tooth attachment in Coluber constric- tor (and also in some elapids and viperids — see below) differs from that seen in more primitive snakes. Rather than implanting within a gutter, the teeth attach directly to the surface of the palatal bones — this is likely a result of the highly modified orientation of these elements. In many higher snakes, the palatal elements are deflected such that they are no longer oriented in the mediolateral plane but lie instead in the dorso- ventral plane; thus, the palatal teeth attach along a flange that projects from the medial edge of the palatal bones (Fig. 27). The teeth attach via a mass of attachment tissue deposited on the surface of this flange and ankylose directly perpendicular to the surface (Figs. 26B; 27). Elapidae Nearly all elapids possess teeth on both the pterygoid and the palatine bones, including three specimens of Homoroselaps lacteus (contra Un- derwood & Kochva, 1993). Palatine teeth are absent in the hydrophiid Emydocephalus, a group specialized to feed entirely on fish eggs (Voris, 1966; Marx & Rabb, 1970, 1972). and CaMophis bivirgatus is reported to lack teeth on the pterygoid bones (Marx & Rabb, 1972). As in colubrids, the palatal tooth row is much longer than the marginal tooth row. In some species, this is largely due to the extreme shortening and specialization of the marginal tooth row rather than to a posterior elongation of the palatal tooth row per se (e.g., Micrurus fulvius. Fig. 28A). In many other elapids, however, pterygoid teeth do extend posteriorly onto the quadrate ramus of the ptergyoid, as observed in most colubrids. Generally, elapid teeth are elongate, recurved cones (Fig. 28). Differences in tooth size within palatal tooth rows are common. The pterygoid teeth may be shorter and stockier than the elongate palatine teeth (e.g., Micrurus fulvius. Fig. 28A). Many species exhibit modest carinae on the lingual and labial edges (e.g., M. nigrocinctus, Fig. 28B. C), and some have flat mesial surfaces (e.g., Aspidonwrphus muelleri). The majority of elapids surveyed exhibit a very shallow longitudinal groove (most likely a de- velopmental correspondence to the venom tube in the anterior maxillary teeth) along the mesiolingual side of the palatal teeth (similar grooves are found on the mesiolabial side of the dentary and posterior maxillary teeth) (Figs. 28C; 29). These grooves (described by Van Denburgh & Thompson, 1908) are sometimes very faint and difficult to detect but are nonetheless widely distributed among elapids. They are generally more pronounced on the anterior palatine teeth and become less well developed on the posterior pterygoid teeth. The grooves develop early in the ontogeny of the replacement teeth (Fig. 29) and are found on the side of the tooth opposite the dental lamina in both palatal and marginal teeth. The attachment of palatal teeth in Micrurus nigrocinctus occurs within a resorbed cavity in the fairly narrow palatal bones (Fig. 29). The palatal teeth are attached within this cavity primarily at the sides of the tooth base (Fig. 29B). Attachment tissue extends far up the sides of the tooth, and, in sections, the distinction between attachment tissue and tooth is difficult to discern. Instead, the junction of attachment tissue and dentine is blurred, and the two tissue types appear somewhat interwoven (Fig. 29 A). This phenomenon is also evident in the palatal teeth of Naja nigricollis and TV. nivea. Viperidae We found palatal teeth to be present on both the palatines and the pterygoids of most viperids. although the number of teeth on the palatine is few compared to many colubrids (Marx & Rabb. 1970. 1972). Several species appear to have independently lost palatine teeth (e.g., Crotalus basiliscus, Echis coloratus [variable — palatine teeth were present in our single observed specimen but were reported as absent in Marx & Rabb, 1970, 1972], Calloselasma rhodostoma [variable according to Kardong. 1990], Ophryd- cus undulatus, Protobothrops flavoviridis [Marx & Rabb. 1970. 1972]. and Protobothrops mucros- quamatus). Viperid palatal teeth are elongate, smoothly recurving cones that point toward the FIELDIANA: ZOOLOGY midline (Fig. 30A). Unlike in elapids, in which the venom groove of the marginal teeth is mirrored in the palatal teeth, viperid palatal teeth do not exhibit any of the morphological features related to the venom delivery system that are seen in the marginal teeth. The number of marginal teeth in viperids is typically highly reduced; the palatal teeth constitute the primary tooth row in these species. Palatal teeth do not differ substantially in size along this row. Tooth attachment in Agkistrodon contortrix is similar to that in Coluber. The palatine and pterygoid bones in Agkistrodon are unusually narrow, and the teeth attach directly to the ventral edge of the bone rather than being set within a cavity (Fig. 31). Although the palatal bone may sometimes exhibit a ventral concavity, the palatal teeth do not sit within it. Rather, the tooth base abuts and fuses to the walls of this cavity via a substantial deposition of attachment tissue (Fig. 3 IB). Discussion Morphology and Arrangement of Palatal Teeth The presence or absence of palatal teeth in nonophidian squamates varies extensively from family to species level; snakes, however, are more uniform in these patterns (Table 1). In non- ophidian squamates, variability occurs within the families Iguanidae, Teiidae, Gymnophthalmidae, Lacertidae, Scincidae, Anguidae, and Heloder- matidae; within the genera Algyroides, Ameiva, Anguis, Anisolepis, Anolis, Chalarodon, Conolo- phus, Crotaphytus, Cyclura, Dipsosaurus, Enya- lius, Gambelia, Gerrhonotus, Heloderma, Kentro- pyx, Laemanctus, Leiocephalus, Leiosaurus, Liolaemus, Lygosoma, Mabuya, Mesaspis, Ophi- saurus, Opiums, Plica, Podarcis, Polychrus, Pristidactylus, Sauromalus, Stenocercus, Tropi- dophorus, Tropidurus, Uroscanodon, and Uros- trophus; and within the species Ameiva ameiva, Anolis cristatellus, Conolophus subcristatus, Cro- taphytus collaris, Cyclura cornuta, Dipsosaurus dorsalis, Gambelia wislizenii, Heloderma suspec- tum, Kentropyx calcaratus, Leiocephalus carina- tus, Lygosoma punctata, Ophisaurus apodus, O. attenuatus, Podarcis sicula, Stenocercus chryso- pygus, Stenocercus empetrus, Stenocercus varius, and Tropidophorus brookei. Beyond presence/ absence, variability was also found in the number of rows of teeth on the palate for nonophidian taxa. For example, individuals of Iguana, Basiliscus, Crotaphytus, Ctenosaura, Cy- clura, Lacerta, Gerrhonotus, and Ophisaurus differ in whether teeth are arranged in single or multiple rows. Among snakes, variability in palatal tooth presence (variability on palatines, pterygoids, or both) occurs within the families Uropeltidae, Boidae, Colubridae, Elapidae, and Viperidae; within the genera Aparallactus, Atractaspis, Calliophis, Calloselasma, Charina, Chilorhinophis, Crotalus, Echis, Lytorhynchus, and Protobothrops; and within the species Calloselasma rhodostoma, Charina bottae, and Echis coloratus. While some uropeltid species and the boid Calabaria lack palatal teeth altogether, nearly all colubroids possess at least some teeth on either the palatines or the pterygoids. Higher taxa exhibiting the uniform absence of palatal teeth include Chamaeleonidae, Agami- dae, Gekkonidae, Pygopodidae, Xantusiidae, Cordylidae, Aniellidae, Xenosauridae, Varani- dae, Dibamidae, Amphisbaenia, and Scolecophi- dia. Those exhibiting the uniform presence of palatal teeth (teeth on one or more palatal elements) include Gerrhosauridae and the alethi- nophidian families Aniliidae, Cylindrophiidae, Xenopeltidae, Colubridae, Elapidae, and Viper- idae. Potential explanations for the uniform absence and uniform presence of palatal teeth in such taxa are discussed below under "Func- tional Considerations." Among those species that exhibit palatal teeth, the number, extent, and arrangement of teeth across the palate varies. Generally, higher snakes exhibit a complete secondary tooth row on the palate that extends from the anterior portion of the oral cavity for a length that is roughly equivalent to the marginal tooth row in basal alethinophidians, and sometimes much longer than the marginal tooth row in colubroids. This row is always single. Palatal tooth rows in nonophidian squamates may be single, double, or multiple. In most "lizards" with palatal teeth, expression is limited to discrete regions of the palatal surface, and these are usually located posteriorly on the palate. Ophisaurus is some- what of an exception to this pattern, expressing teeth in more regions of the palate. However, these teeth occur in discrete patches unlike the uninterrupted, single tooth row typically seen in snakes. The only nonophidian squamates exhi- MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 17 biting a "snake-like," single, well-organized tooth row are Shinisaurus and Lanthanotus. In most nonophidian lizards, palatal teeth occur only on the pterygoids (occasionally also on the palatines). In Ophisaurus uniquely, palatal teeth may occur on ptergyoids, palatines, and vomers. In snakes, teeth occur on both the ptergyoid and the palatine in almost all species. As noted by Estes et al. (1988), vomerine teeth occur only in those individuals that exhibit palatine teeth, and palatine teeth occur only in those individuals that exhibit pterygoid teeth. In snakes, both marginal and palatal tooth rows are linear, well organized, and longitudinally oriented, and individual tooth orientation is nearly always posteriorly recurved. The only exception is seen in boids, colubrids, and viperids. where some palatal teeth may be oriented postero- medially; when this condition occurs, it is consistent between the marginal and palatal dentitions. In contrast, the palatal tooth rows of lizards may differ in orientation from the mar- ginal tooth rows, and are not constrained in linear rows. Examples of transverse orientation, di- agonal orientation, curving tooth rows, and linear tooth rows are seen. Also, in contrast to snakes, orientation of individual palatal teeth in lizards ranges from quite variable (e.g., Heloderma) to highly consistent (e.g., Shinisaurus). In both cases, these do not necessarily mirror what is seen in the marginal dentition. In the case of Shinisaurus, for example, the palatal teeth are recurved poste- riorly, whereas the marginal teeth are not. In almost all squamates, palatal teeth are smaller than marginal teeth. In all nonophidian lizards, this size disparity is large and, in some cases, extreme (e.g., Iguana). In most snakes, however, the palatal teeth are only slightly smaller than the marginal teeth. In one species with highly specialized dentition (Xenopeltis unicolor), the palatal teeth exceed the marginal teeth in size. In addition, differences in tooth size on different palatal elements are evident in snakes. Two distinct patterns can be seen. In some species, there is an abrupt change in tooth size between tooth groups occurring on different palatal elements, but the teeth on any given element are roughly the same size (e.g., elapids and boids; see also Kluge, 1993a). In other species, a gradual decrease in tooth size occurs along the palatal tooth row from anterior to posterior (e.g., colubrids and xenopeltids). In general, palatal teeth in squamates are either very similar in form, or simpler than the marginal teeth. There are no cases where the palatal teeth are morphologically more complex than the marginal teeth. In many species, de- tailed morphological correspondence is seen between the dentitions: the palatal teeth of varanoids exhibit plicidentine just as the mar- ginal teeth do; in some Corucia and Ctenosaura, the pattern of cusps seen on the marginal teeth is also present on the palatal teeth; the spatulate tooth crowns of Xenopeltis and the fluting of the teeth in Cerberus are found in both dentitions. In snakes, morphological correspondence between palatal and marginal dentitions is nearly uni- form, with the exception of those species in which the marginal dentition exhibits extreme specializations (i.e., for envenomenation). For example, the blade-like posteriormost maxillary tooth in Heterodon nasicus has no palatal analog. Interestingly, although the highly specialized hypodermic marginal tooth form of elapids is not seen in the palatal teeth, an early corre- sponding stage of development is evident in the mesiolingual groove (e.g., Fig. 28C). These observations support the general idea of de- velopmental homology at some level between marginal and palatal dentitions. Development of Palatal Teeth Tooth development in squamate reptiles oc- curs within the dental lamina, an infolding of oral epithelium that possesses the potential to produce teeth. On the marginal dentigerous bones, the dental lamina extends along the lingual base of the tooth row. Tooth germs develop on the labial side of this fold and migrate apically during development to eventually re- place older teeth (Edmund, 1969). With respect to the development of palatal teeth, a dental lamina occurs labially in most species that exhibit well-organized single tooth rows, with modifications of this arrangement observed in those species exhibiting multiple rows (see below under "Replacement of Palatal Teeth"). Some researchers have proposed the existence of developmental modules corresponding to different functional regions in the dentition. According to Stock (2001), modularity of tooth expression may explain how some taxa lose entire regions of a dentition despite the un- modified persistence of tooth groups in other regions. A question of central relevance to the topic of modularity in tooth development is whether the presence of palatal teeth can be 18 FIELDIANA: ZOOLOGY "switched off" for periods of evolutionary time and then reexpressed in a descendant organism. The condition in some groups such as anguids, in which only Ophisaurus apodus possesses vomer- ine teeth, could be explained by modularity, where tooth expression is switched on after a period of absence, as has been suggested for some teleost fishes (Stock, 2001). Researchers have yet to explore patterns of palatal tooth expression in the early development of squamates. Greven and Clemen (1980) report that the giant salamandrid Andrias japonicus develops tooth rows and dental laminae on the palatine bones early in ontogeny, but these structures are then quickly resorbed (adults lack palatine teeth). If such processes occur in squamates, they might aid in understanding the variation and distribution of palatal teeth across groups. Despite the level of variability observed in the palatal dentition of squamates, the expression of teeth along the palate also indicates some level of constraint. Palatal teeth are most consistently present in the posterior region of the palate (the pterygoids); when suppression occurs, it appar- ently follows a directional bias (vomers, then palatines, then pterygoids) (see Estes et al., 1988). Most taxa that bear teeth on more than one palatal element (e.g., iguanids, varanoids, anguids, and some viperids) follow this pattern. However, colubroids demonstrate variability in the posterior rather than anterior extent of the palatal tooth row, and a few taxa lack ptergyoid teeth while retaining palatine teeth (e.g., Mela- nophidium, Atractaspis, Dasypeltis). Constraint could also be a factor in those squamate groups that uniformly lack palatal teeth (e.g., Agamidae, Gekkonidae, Varanidae), given the variability observed in other family groups. Also, higher snakes (Alethinophidia) and gerrhosaurids uniformly possess palatal teeth, save a very few exceptions (e.g., Calabar id). While the feeding mode of nearly all higher snakes imposes a strong functional constraint for the retention of palatal teeth, the role of developmental constraint is less certain. In instances where functional constraint is purport- edly absent (e.g., Emydocephalus) and where palatal teeth may be a functional hindrance (e.g., Dasypeltis, various viperids), the palatal denti- tion is lost or reduced. In addition, a majority of colubroids with reduced or no palatal teeth exhibit extensive cranial modifications associated with a fossorial existence, and some venomous colubroids may exhibit low palatine tooth counts because of contraints associated with venom delivery (Marx & Rabb, 1970, 1972). It thus seems that functional considerations may drive the patterns observed in higher snakes. In gerrhosaurids, however, the uniform presence of palatal teeth is not tied to a particular feeding mode, and tooth shape and arrangement are also highly variable within this group. It seems more likely that this group exhibits uniform presence of palatal teeth because of either developmental or phylogenetic constraint. Attachment of Palatal Teeth Mechanisms of tooth attachment, long recog- nized to differ among vertebrate groups (Tomes, 1874; Romer, 1956; Edmund, 1960, 1969) have been a recurrent source of controversy (Smith, 1958; Osborn, 1984; Gaengler, 2000). Squamate reptiles are no exception, and recent studies have come to very different conclusions regarding modes of tooth attachment across different squamate groups and potential homologies between them (Lee, 1997a; Zaher & Rieppel, 1999; Caldwell et al., 2003). Traditionally, three basic modes of tooth attachment (pleurodonty, acrodonty, and theco- donty) are recognized (Edmund, 1969), although the validity of these discrete categories has been questioned (Estes et al., 1988), and numerous authors recognize the existence of subcategories of these modes for some taxa (Osborn, 1984; Zaher & Rieppel, 1999; Gaengler, 2000). Theco- donty is a mode of attachment long considered to occur only in archosaurs and mammals, entailing the attachment of teeth within a discrete bony alveolus (socket) via a periodontal ligament (i.e., a syndesmotic attachment). Replacement teeth develop within alveoli in thecodont ani- mals; the dental lamina therefore is not contin- uous along the tooth row but instead is divided among sockets. In contrast, pleurodonty and acrodonty, both normally considered to occur in lepidosaurs, traditionally describe a synostotic type of attachment. Most squamate reptiles exhibit a pleurodont attachment mode wherein the tooth is ankylosed to the lingual surface of the pleura of the jaw via the deposition of mineralized attachment tissue (usually called bone of attachment; but see Osborn, 1984; Gaengler, 2000; Caldwell et al., 2003). Tooth replacement is continuous throughout life in these species, and the dental lamina extends MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 19 without interruption along the base of the marginal tooth row. A few taxa (e.g., trogono- phid amphisbaenians, agamids, and chamaeleo- nids) exhibit an acrodont attachment mode where the teeth are attached apically to the jaw within a shallow alveolar groove whose walls are composed of labial and lingual flanges of the tooth-bearing element. The teeth are ankylosed to the margins of this groove on both sides, and the bases of the teeth are typically in contact and fused to each other. Acrodont teeth are not replaced in adults, and resorption pits are absent. Histological sections of Chamaeleo and Agamo- don indicate the absence of a dental lamina in adults of these taxa (pers. obs.), although Rose (1893) reports the dental lamina to be present but inactive in adult agamids. Recently, several authors have suggested a thecodont attachment mode in snakes and in the extinct mosasaurs (Lee, 1997a) or in most squamates (Caldwell et al., 2003). This is based on the observation that teeth in some taxa are ankylosed within a cavity in the bony tooth base (but see Zaher & Rieppel, 1999) and on histological similarities in attachment tissues (Caldwell et al., 2003). The primary questions here are the nature (homology) of "sockets" and of the attachment tissues. For example, is the bony alveolus seen in mammals and archosaurs homologous to the "socket" seen in snakes and mosasaurs, or is the latter a resorbed cavity within the attachment tissue that creates the superficial impression of a socket once the tooth is shed? Additionally, is such "socketing" seen only in snakes and mosasaurs? Our results indicate that most squamate taxa generally exhibit the same attachment mode in the palatal teeth as they do in the marginal teeth, but these correspondences are tempered some- what by differences in the attachment substrates. In taxa exhibiting labial pleurodonty of the marginal teeth, the palatal teeth are often seen to attach with a "pleurodont" geometry as well. The details of this pleurodonty, however, may differ due to attachment to the flat palatal surface. In many cases, teeth are implanted in a slightly reclined position such that attachment to the flat pterygoid surface occurs via the base and side of the tooth (Figs. IE; 3B; 9B, C). In others, such as Gymnophthalmus, teeth ankylose within a cavity in the ventral pterygoid surface, attaching to the bottom and posterior wall of this cavity much as the marginal teeth in this taxon affix to the pleura of the maxilla or dentary (Fig. 5B, C). In Iguana and Ctenosaura, palatal teeth attach primarily by their sides to a buildup of mineralized tissues on the palatal surface (Fig. IB, C). The "pleurodont" attachment mode in this case is facilitated by the accretion of these tissues on the palatal substrate to form a vertical surface for attachment. Despite these examples, some squamates with pleurodont teeth along the margins demonstrate nonpleurodont palatal tooth attachment. In anguids such as Ophisaurus (Fig. 14B-D), many specimens exhibit symmetric attachment of tooth bases to the palatal bones rather than an inclined implantation incorporating the side of the tooth. Attachment of the palatal teeth in Shinisaums crocodilurus also differs from the attachment observed in the marginal teeth. In this species, the palatal teeth ankylose within a longitudinal gutter on the pterygoid (Fig. 13C). Although the lingual wall of this gutter is taller than the labial wall, the teeth nonetheless attach solely by the base via large amounts of attachment tissue, and the side of the tooth does not play a role in attachment. Histology of the palatal dentition in nearly all observed nonophidian squamates reveals anoth- er important distinction from the marginal teeth. On palatal surfaces, tooth attachment nearly always involves implantation within a resorbed cavity or groove in the ventral surface of the palatal element. Even in Heloderma, in which the palatal teeth appear to attach very superficially, a shallow resorbed cavity within the palatal bone is revealed by open tooth positions in some specimens. In this sense, nearly all taxa observed exhibit some level of "socketing" of the palatal teeth due to the constraints of attachment to a flat surface, regardless of the attachment mode. The role of attachment tissues may also differ between the margin and the palate, perhaps again reflecting differences in the shape of the underlying bone. Lanthanotus borneensis, for example, possesses a copious amount of attach- ment tissue ankylosing the palatal teeth (Fig. 17C), but not the marginal teeth. The extent of this attachment tissue covering is such that the tooth bases are completely separated from each other; a pterygoid with the teeth stripped from it shows a "socketed" pattern (Fig. 17D) reminiscent of that seen in some snakes and mosasaurs. Variability in tooth attachment geometry is seen on the palatal elements of many squamate species. For example, among iguanids, depend- 20 FIELDIANA: ZOOLOGY ing on the shape of the ventral surface of the palatal element, teeth may attach within an excavated cavity in the element or to the side of a ridge created by attachment tissue. Attach- ment geometry therefore may represent a com- plex combination of phylogeny, constraints of tooth development, and constraints imposed by attachment to substrates of varying shapes. One implication of these results is that "thecodonty" cannot be inferred solely from the presence of implantation within a resorbed cavity. The implantation of teeth within cavities is seen to vary according to qualities of the underlying bone and may even vary across the dental elements of a single organism (e.g., Lanthanotus). Further, snakes and mosasaurs are not unique among squamates in exhibiting tooth attachment within resorbed cavities. Still, the attachment of teeth within deep cavities filled by attachment tissues is indeed an interesting characteristic of snakes and mosa- saurs (Lee, 1997a; Caldwell et al., 2003), and this condition is now shown to extend to Lanthanotus and Shinisaurus as well. The composition of tissues involved in ankylosis of teeth to un- derlying bone may better indicate attachment homologies (Gaengler, 2000; Caldwell et al., 2003). Potential homologies of the attachment tissues in snakes and mosasaurs have been proposed (Caldwell et al., 2003). Such tissues in other squamate taxa have not yet been examined in comparable detail, and these similarities will doubtless bear further scrutiny. Replacement of Palatal Teeth Our results indicate that traditionally recog- nized modes of tooth replacement in squamates for the marginal dentition are mirrored in the palatal dentition. However, the position of the dental lamina may differ between the palatal and marginal dentitions, resulting primarily from differences in the arrangement and distribution of teeth on different elements. Also, in some taxa, tooth replacement is imprecise on the palatal elements, and incomplete resorption may contribute to accumulation of palatal teeth in loosely organized rows. Edmund (1960, 1969) described two modes of replacement to account for the variability found in squamates. Iguanid-type replacement entails the development of replacement teeth in an upright position within a lingual resorption cavity in the base of the functional tooth and loss of the functional tooth through such resorption. Var- anid-type replacement entails distolingual devel- opment of replacement teeth in an upright position and loss of older teeth through erosion of attachment tissues rather than the formation of a resorption pit. Higher snakes (alethinophidians) exhibit a modification of the varanid-type re- placement, but are unique in the recumbent orientation of the developing replacement teeth (Zaher & Rieppel, 1999). Rieppel (1978) intro- duced an additional mode of tooth replacement, the intermediate mode, to describe replacement patterns in some anguinomorph lizards. With this mode, replacement occurs distolingually, but involves the development of a resorption pit around or above the alveolar foramen, which is implicated in the shedding of the functional tooth. Intermediate replacement thus differs from the iguanid mode in the distolingual rather than lingual origin of the replacement tooth (although this varies), and differs from the varanid mode in the development of resorption cavities during the replacement process. Generally in squamates, replacement of the palatal teeth closely approximates the type of replacement mode observed in the marginal teeth, and the location of the replacement teeth relative to the functional teeth is exactly mir- rored (Lee, 1997a). There are some exceptions to this mirroring phenomenon, such as Lanthanotus (in which we observed both lingual replacement on the small number of palatine teeth and labial replacement throughout the longer pterygoid tooth row); Gerrhosaurus (in which we observed one instance of lingual replacement in the otherwise labially replacing pterygoid tooth row); and Iguana (in which lingual and labial replacement occurs in different rows). Despite the wide variety of arrangements we observed in the palatal dentition of iguanids, developing replacement teeth always occupy basal resorption cavities, just as with the marginal teeth. Likewise, the palatal teeth of Heloderma exhibit the varanid mode of replace- ment observed in the marginal teeth. Also, the palatal teeth of alethinophidian snakes develop labially in a recumbent position, mirroring the lingual recumbent replacement teeth of the maxillae. This consistency of replacement mode corroborates other sources of evidence for a homology relationship between the dentitions of the marginal and palatal elements. The marginal dentition in squamates occurs without exception in a single row. The dental MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 21 lamina uniformly exists as a strip of infolded epithelial tissue that extends along the lingual base of this row. In some squamates, the palatal dentition is also arranged in a single row (e.g., alethinophidian snakes, Shinisaurus, Lanthanotus, and many teiids). In such cases, replacement teeth develop within a dental lamina located labial to this tooth row. In the case of Iguana, in which teeth are organized into two parallel rows on each pterygoid, a dental lamina is present on each side of the pterygoid tooth rows. In taxa with more than two closely spaced palatal tooth rows, we observed two different replacement mechanisms. In Ophisaurus apodus, the pterygoid typically exhibits multiple tooth rows. Histological sections of the pterygoid reveal a single infolding of dental lamina extending across all tooth rows from which replacement teeth develop (Fig. 15B, C). The multiple pterygoid tooth rows in O. apodus are concurrently deciduous; replacement is seen to occur across multiple adjacent rows (Fig. 15B). In Lacerta lepida, older teeth remain affixed to the pterygoid posteromedially, and newer teeth become ankylosed to the ptergyoid anterolater- al^, to contribute to an overall patch-like distribution of teeth in various stages of wear (Fig. 7B). As replacement is observed only along the anterolateral margin of these tooth patches (Fig. 7C), the presence of the more postero- medial tooth rows must be explained via a mechanism other than the simultaneous re- placement described above for Ophisaurus. In a study of the Permian reptile Captorhinus aguti, Ricqles and Bolt (1983) describe a possible mechanism for the replacement of multiple adjacent marginal tooth rows: upon attachment of a new, medial row of teeth, the older tooth rows migrate laterally across the dental element via a reworking of the underlying bone and attachment tissues. Through such processes of growth and resorption, multiple rows of teeth from a single point of origin "travel" across the surface of the tooth-bearing element. The oldest, most lateral teeth are eventually shed via an unknown mechanism. This model for the de- velopment and replacement of the marginal teeth in Captorhinus could describe the development and replacement of the palatal teeth in Lacerta. The only other explanation would be that the dental lamina retreats anterolateral^ over time, leaving incompletely resorbed teeth in more posteromedial rows. Functional Considerations The well-developed palatal dentition in higher snakes has received considerable attention within a functional context (Boltt & Ewer, 1964; Frazzetta, 1966; Cundall & Gans, 1979; Cundall & Deufel, 1999; Deufel & Cundall, 1999), commonly explained in terms of the unique feeding mechanisms involved in prey striking and in the swallowing of large prey (e.g., "prey- snaring" or the "ptergyoid walk"). In contrast, the palatal dentition in nonophidian squamates, although arising frequently in phylogenetic con- texts, is rarely discussed in terms of function. Indeed, it is implicit in the work of many researchers that palatal teeth in many non-snake squamates are vestigial remnants of an ancestral condition. This view seems especially tempting in taxa such as Aspidoscelis and Heloderma, in which the palatal teeth are very few in number compared to the marginal teeth and extremely small relative to the size of the mouth. Moreover, high variability in presence, arrangement, and morphology of palatal teeth within many taxa (e.g., Cyclura and Tropido- phorus) suggests an absence of functional con- straint on these traits. Nonetheless, some researchers have postulated specific functions for the palatal dentitions in some "lizards." In a comparative study of diet and dentition in several iguanids, Montanucci (1968) proposed two functional explanations for the different shapes and arrangements of the palatal teeth. First, taxa with a modest number and a simple arrangement of palatal teeth were proposed to use them to supplement the mar- ginal dentition in subduing and processing live prey. Such taxa tend to be insectivorous or carnivorous and generally kill their prey by piercing and crushing with teeth. This "punc- ture-crushing" falls short of mammalian masti- cation (which involves transverse movement of the mandible), but helps soften prey items for swallowing and digestion (see also Schwenk, 2000). Indeed, in numerous primarily insectivor- ous taxa (e.g., many scincids and teiids), we found a generally small number of palatal teeth disrupting the otherwise flat palatal surface in the rear of the mouth. Second, some taxa with numerous palatal teeth arranged in longer rows were proposed to use these teeth to enhance prey grip. Montanucci (1968) notes that all those iguanid species exhibiting long rows of palatal teeth are herbiv- 22 FIELDIANA: ZOOLOGY orous and possess a specialized marginal denti- tion that serves to shear plant matter. He proposes that the simpler palatal teeth compen- sate by providing the gripping function that is not possible with the shearing marginal teeth. The doubling of the tooth row (especially evident in Iguana and Ctenosaura) serves to increase the area and the purchase of this gripping surface (Montanucci, 1968). Throckmorton (1976) sim- ilarly suggests that the arrangement of small, sharp teeth on the pterygoid of /. iguana stabilizes food matter during feeding. This functional dichotomy is consistent with ontogenetic changes observed in the pterygoid tooth number in iguanids (Montanucci, 1968; de Queiroz, 1987). In iguanids that exhibit palatal teeth, the number of pterygoid teeth is strongly correlated with skull size (Montanucci, 1968). Herbivorous iguanids may also undergo an ontogenetic shift in diet. Juveniles of Ctenosaura and some Iguana are reported to feed largely on live prey (e.g., insects) and transition to herbivory as they reach a larger body size (Montanucci, 1968). The transition from relatively few pterygoid teeth to a long row may thus correspond to an increasing dependence on plant matter in the diet. In higher snakes, most taxa exhibit a function- ally conserved feeding mode that actively uses the palatal tooth rows. In boids, the palatal and maxillary dentitions operate in unison to snare and secure prey during a strike, the recurved and reverse-curved teeth working like a rachet as the jaws move over the prey item (Cundall & Deufel, 1999; Deufel & Cundall, 1999). Also, as detailed by Boltt and Ewer (1964) and Frazzetta (1966), higher snakes use modes of medial jaw transport (the "pterygoid walk") and lateromedial jaw transport that involve the specialized use of both palatal and marginal tooth rows to draw the head and jaws over large prey items during ingestion. In elapids and viperids, the palatal tooth rows must perform this function alone, as the maxillary dentitions in these snakes are highly specialized for envenomation (Cundall & Greene, 2000). These clear roles of the palatal dentition in snake feeding help explain the relative consistency in tooth arrangement and morphology across alethi- nophidian groups. Moreover, when the palatal dentition in higher snakes deviates from this typical arrangement (which is rare), it is usually in taxa with highly specialized diets or cranial modifications. In the egg-eating snake Dasypeltis, for example, teeth are absent on the pterygoids and reduced on the palatines (Gans, 1952). In the sea snake Emydocephalus, an exclusive diet of small, soft fish eggs may be related to the absence of palatine teeth (Voris, 1966). Likewise, in viperids and atractaspids, reduction of the palatal dentition may be tied to functional trade-offs involving venom delivery and fossorial existence, respectively (Marx & Rabb, 1970). In vipers with few or no palatine teeth, the palatine bone is small in size and forms a mobile joint with the pterygoid, allowing greater kinesis during a strike. In the fossorial colubrid Atractaspis, the loss of pterygoid teeth may be associated with the shortening of the cranium for increased burrowing capability. In addition to these examples from higher snakes, it is likely that the lack of palatal teeth in basal snakes (scolecophidians) is due to extreme specializations in feeding mode. Scolecophidian snakes are gape-limited and are restricted in diet to prey that can pass through the diminutive buccal cavity (Cundall & Greene, 2000). Kley (2001) reports that leptotyplophids ingest prey through raking movements of the mandibles and that typhlopids perform this function via maxil- lary raking (the feeding mechanism of anomale- pidids is unknown). Both of these highly specialized feeding mechanisms use the marginal dentition to accomplish intraoral transport. In addition, these taxa feed mainly on insect larvae and pupae, obviating any putative role for palatal teeth. The patterns observed in the palatal dentitions of nonophidian squamates do not appear to be as closely tied to functional constraints as they are in snakes. While the correlations between lizard diet and palatal teeth described above are indeed plausible for some groups, these patterns are not sustained across groups. For example, while certain specializations of the palatal dentition (i.e., long, doubled rows of small teeth) may aid in an herbivorous diet, this trend seems to be restricted to iguanids. Largely herbivorous lizard taxa from other families often have simple palatal teeth or none at all. A recent survey of levels of herbivory across nonophidian squamates by Cooper and Vitt (2002) reveals high levels of plant consumption in numerous species with few or no palatal teeth. Examples of such taxa whose diet consists of more than 50% plant matter include the agamid Uromastyx aegyptius, the iguanid Uma inornata, the lacertid Podarcis lilfordi, the teiid Aspidoscelis murinus, the scincid Tiliqua rugosus, and the cordylid Platysaurus guttatus. Many of these taxa feed largely on flowers and fruits rather than leaves (Cooper & Vitt, 2002); Uromastyx, MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 23 however, is highly folivorous yet exhibits no palatal dentition. Moreover, we observed a wide range of palatal tooth morphologies and arrange- ments in iguanines. most of which feed nearly entirely on plant material. For example, palatal teeth are rarely found in Dipsosaurus and Conolophus (de Queiroz. 1987; pers. obs.). but Cooper and Vitt (2002) describe species of these genera as 97.39?- and 999£ herbivorous, respec- tively. Although the presence of highly specialized palatal tooth rows in Iguana may indeed contrib- ute to an herbivorous feeding mode, the absence of palatal teeth in the herbivorous species mentioned above challenges a simple functional correlation. Another similar challenge to such explanations is our observation of high variability in palatal tooth presence across squamate taxa that are largely insectivorous. Functional correlations between diet and patterns of palatal dentition may be somewhat weak in lizards in part because the diets of most lizards are fairly broad (Schwenk. 2000; Cooper & Vitt. 2002). Highly specialized feeders are uncommon among lizards; most can be regarded as opportunistic generalists (Hotton. 1955; Greene. 1982; Schwenk. 2000). A similar argu- ment has been proposed by Greene (1982) to explain the absence of other feeding-related phenotypic specializations in lizards. In higher snakes, on the other hand, nearly all types of feeding specifically involve use of the palatal teeth for intraoral transport. The absence of palatal teeth in snakes can in most instances be attributed to functional correlations stemming from dietary or life history specialization (e.g.. Scolecophidia. Emydocephalus, Dasypeltis). In summary, palatal teeth are present in squamate taxa that exhibit a wide range of feeding habits. Except for higher snakes, which are committed to a highly specialized feeding strategy, no particular feeding mode is associated with the uniform absence or presence of palatal teeth. Arrangement and morphology of palatal teeth do offer some correlations with dietary habits (e.g.. Iguana iguana), but more general patterns of correlation are tempered by variabil- ity in lizard diet and by evidence of phylogenetic constraint on the development of palatal teeth in some lizard families. Phylogenetic Considerations The presence or absence of palatal teeth and characteristics of palatal teeth have implications for phylogenetic studies of squamate reptiles. One basic question regarding the use of palatal tooth characters in phylogenetic studies is polarity — are squamate palatal teeth primitive or derived? Conventional wisdom holds that palatal teeth were fairly ubiquitous in early tetrapods and that multiple independent losses of palatal teeth have occurred during the evolution of this clade (e.g.. Evans. 2003). However, for some squamate groups (e.g.. gymnophthalmids). palatal teeth appear to be rare and occur in distantly related taxa within the clade (Pellegrino et al.. 2001). potentially implying multiple origins. Likewise, the presence of vomerine teeth in Ophisaurus apodus indicates a probable reacquisition (see also Estes et al.. 1988). It has also been suggested that the palatal teeth in snakes might be neomorphic. that is. not homologous to the generally simpler teeth of nonophidian squa- mates (Cundall & Greene. 2000). Clearly, the ability to re-evolve teeth will affect interpreta- tions of the polarity and homology of palatal teeth across groups. Another phylogenetic issue concerns the puta- tive independent occurrence of teeth on different palatal elements. Some researchers have coded the presence or absence of teeth on each palatal element as independent characters in phyloge- netic studies. However. Estes et al. (1988) have questioned the independence of teeth distributed on different palatal bones, and our survey supports their interpretation. This is consistent with the idea of a continuous developmental field generating tooth development. According to this model, tooth development would then be re- pressed from anterior to posterior in those taxa that lack a full palatal dentition. Within higher snakes, most basal taxa appear to exhibit a fairly uniform distribution of teeth on the palatal elements, but colubroids exhibit variability in the posterior extent of the palatal dentition (Fig. 26) rather than the anterior extent, as is seen in lizards. Thus, variability in palatal tooth distribution does appear to be related to directional constraints in tooth ex- pression, but the direction differs between non- ophidian and ophidian groups. Several features of the palatal dentition may be important to the specific phylogenetic issue of snake origins within Squamata. First, one general distinction between the palatal dentitions of ophidians and most nonophidian squamates is the uniformity of the tooth arrangement in the 24 FIELDIANA: ZOOLOGY former. Even in taxa with a highly developed palatal dentition, such as Iguana, the palatal teeth are arranged in a less orderly fashion than the marginal teeth (Fig. 1C). In contrast, the palatal dentition of higher snakes is virtually identical in organization to the marginal denti- tion. This degree of organization has an obvious functional basis in the palate's role during ingestion of large prey items by alethinophidian snakes (Boltt & Ewer, 1964; Frazzetta, 1966; Cundall & Gans, 1979); however, phylogenetic correlations have also been suggested. The linear, highly organized palatal dentition of Lanthano- tus borneensis, in addition to its recurved teeth, led McDowell and Bogert (1954) to infer either a functional or an evolutionary relationship between Lanthanotus and snakes. In both groups, the marginal teeth are pointed and recurved, possess a small medullary foramen, vertical striations at the base (we find this only rarely in snakes), and replace alternately. Fur- thermore, they note that Lanthanotus is the only extant "lizard" with a snake-like arrangement of palatal teeth (although the extinct Saniwa ensidens and mosasaurs are also similar in this regard). We observed that this arrangement, at least on the pterygoid bones, is also shared to a degree by Shinisaurus crocodilurus. Estes et al. (1970) noted that both Lanthanotus and the fossil snake Dinilysia possess palatal dentitions similar to those of extant snakes but also emphasized key differences. Compared to most snakes (including relatively basal taxa such as Cylindrophis), the palatal teeth in these taxa are comparatively smaller than the marginal teeth, are arranged in a more curvilinear row, and do not extend to the anterior portion of the palatines. Cundall and Greene (2000) suggested that the absence of palatal teeth is plesiomorphic for snakes based on the lack of palatal teeth in scolecophidians. In addition, they note morpho- logical dissimilarity between lizard and snake palatal teeth, and disparity between marginal and palatal teeth in nonophidian lizards as opposed to the more uniform condition seen in snakes. In the absence of any scleroglossan lizard showing detailed similarity to snakes in these respects, they raise the possibility that palatal teeth in snakes may be neomorphic. Although there is some dissimilarity between the palatal and marginal teeth in some non- ophidian lizards, we also observed numerous examples of detailed morphological similarity in palatal and marginal teeth, indicating a level of homology between these structures (e.g., Figs. 3D, E; 9C, D; 1 ID, E; 16C, D). In addition, both Lanthanotus and Shinisaurus possess moderately long, well-organized rows of recurved palatal teeth that bear some resem- blance to the palatal tooth rows seen in snakes. As in higher snakes, palatal teeth in both Lanthanotus and Shinisaurus are attached within deep, longitudinal grooves and rely on sub- stantive deposition of attachment tissue to achieve ankylosis. These teeth are smaller than their marginal counterparts, but the fossil snake Dinilysia exhibits a similar size disparity (Estes et al., 1970). Lanthanotus is also similar to snakes in having teeth separated by interdental ridges (at least on the palatal bones) and in the possession of a large alveolar foramen. While we do not propose either Lanthanotus or Shinisaurus as the sister group to snakes, we believe these similari- ties should be considered when evaluating the hypothesis of a neomorphic origin for the palatal teeth of snakes. As discussed above, our study of the squamate palatal dentition is also relevant to the proposed homologous condition of thecodonty in support of a snake-mosasaur clade (Lee, 1997a) or pertaining to squamates more generally (Caldwell et al., 2003). Specifically, our results indicate the widespread occurrence of tooth implantation within resorbed bony cavities, and this is not a condition unique to snakes and mosasaurs. Whether such modes of attachment are broadly interpreted as thecodonty will de- pend on future detailed histological studies of attachment tissues and implantation in many more taxa. Finally, this survey has revealed some patterns of variability that could be considered as potential characters in future phylogenetic stud- ies of squamates. These include the occurrence of palatal teeth in single rows versus clusters versus multiple rows, varying posterior extent of the palatal tooth row in snakes, varying palatal tooth size in snakes (relative to the marginal teeth and within the palatal tooth row itself), and orientation of the palatal teeth in snakes. Acknowledgments We thank Jose Rosado for loan of skeletal specimens; Emma Dahl, Angela Marion, and Beth Bastiaans for laboratory assistance; Betty MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 25 Strack for assistance with SEM; Jessie Maisano for CT image processing; Jim Schulte and Omar Torres-Carvajal for checks on remote specimens; Kurt Schwenk for Lanthanotus histology; Alan Resetar and Jamie Ladonski for help with specimen access, selection and facilities; and Olivier Rieppel and Eric Hilton for discussions about squamate dentition. David Cundall, Harry Greene, and Janet Voight provided helpful criticisms that improved the manuscript. This research was supported by NSF grants DEB- 0235628 and EF-0334961 to MK. Literature Cited Arnold, E. N. 1973. Relationships of the Palaearctic lizards assigned to the genera Lacerta, Algyroides and Psammodromus (Reptilia: Lacertidae). Bulletin of the British Museum of Natural History, 25(8): 289-366. Bell, C. J., S. E. Evans, and J. 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Ameiva ameiva FMNH 22294, NMNH 257529, 292416, 292425; A. chrysolaema NMNH 225056, 259531; A. chrysolaema chrysolaema FMNH 51622; A. corax NMNH 236837; A. deseclwnsis NMNH 221738; A. dorsalis FMNH 22326; A. festiva NMNH 319265; A. griswoldi NMNH 218349; A. lineolata NMNH 259533; A. fuscata NMNH 158908; A. pleei NMNH 236375; A. pluvianotata NMNH 236524; A. quadrilineata NMNH 313852; A. taeniura NMNH 225058. Amphibolous barbatus FMNH 211265, 22451, 51647, 51648, 229937; A. muricatus FMNH 97700; A. sp. FMNH 232739. Amphiglossus splendidus FMNH 72806. Anniella pulchra nigra FMNH 213666. Anolis carolinensis FMNH 229897, 229898; A. cristatellus FMNH 130108, 1301 1 1; A. equestris FMNH 31312, 229922; A. sp. FMNH 98636. Aspidoscelis deppei FMNH 98486-98492; A. exsanguis FMNH 223698; A. gularis FMNH 98493- 98497; A. motaguae FMNH 207870; A. ocellifer FMNH 44150, 44151; A. perplexus FMNH 98504; A. sexlineatus FMNH 98505-98507, 222222; A. tigris gracilis FMNH 98498-98503, 115480, 161622; A. sp. FMNH 98470- 98472, 98474-98482. Bachia heteropa FMNH 49880; B. trisanale FMNH 2061 14. Barisia imbricata NMNH 32166. Basiliscus basiliscus FMNH 16489, 22290; B. plumifrons FMNH 228376, 231609, 257162; B. vittatus FMNH 4500, 31277, 98362, 98363, 207871, 211919, 228396; B. sp. FMNH 98360, 98939, 211858, 217638. Brachylophus fasciatus FMNH 210158. Bradypodion flscheri FMNH 229598, 229961. Bronchocela cristatella FMNH 52391, 52397, 63747. Callisaurus draconoides inusitanus FMNH 98364-98367; C. draconoides ventralis FMNH 1936. C. JJavipimctatus FMNH 8452; C. maculatus FMNH 223689. Cables emma FMNH 196208; C versicolor FMNH 229471-229474, 196115, 229475, 229476; C. sp. FMNH 236133. Celestus barbouri KU 225857; C. costatus FMNH 13254, NMNH 259470; C crusculus NMNH 244580; C. curtissi KU 226038; C darlingtoni KU 226519; C. hewardi KU 226529; C. sternus NMNH 259471, 259472. Chalcides ocellatus NMNH 313452; C. ocellatus ocellatus FMNH 154619, 164674, 167941, 22385, 31294. Chamaeleo gracilis FMNH 22192, 25407, 31369, 31370; C jacksonii FMNH 22040, 206753, 22961 1, 229968, 257482, 257483; C melleri FMNH 98769, 98770, 98878; C oweni FMNH 25408; C. sp. FMNH 22008, 22391, 257102. Chlamydosaurus kingii FMNH 51709. Coleonyx brevis FMNH 209432; C. mitratus FMNH 5053; C. variegatus FMNH 98353, 98354, 209433, 209434, 216543, 216544. Colobosaura modesta USNM 341978. Conolophus subcristatus FMNH 15071, 22009, 22203, 22206, 22208, 22406, 37317, 98859. Cophosaurus texanus FMNH 98383, 98384. Cordylus giganteus FMNH 31283, 211837, 257130; C. trepidoster- num FMNH 251836; C. sp. FMNH 204662, 213252. Corucia zebrata FMNH 257163, 258800, NMNH 306212. Corytophanes cristatus FMNH 206165, 211939, 229589, 229601, NMNH 319262, 319226, 559596; C pericarinatus KU 93456, 190773. Cosymbotus platyurus FMNH 209452, 209453. Crotaphytus collaris FMNH 8543, 8950, 22236, 22301-22303, 98368, 98369, 210169. Ctenosaura acanthura FMNH 31298; C. similis FMNH 6175, 31323, 196144, 211849; C. sp. FMNH 22103, 98371, 98373, 198379, 211835, 213330; Ctenosaura/ Iguana sp. FMNH 98370. Cyclura cornuta FMNH 14801, 22383, 216626, 218645, 250424; C cornuta stejnegeri FMNH 213069. Cyrtodacty- lus cavernicolis FMNH 131508; C. malayanus FMNH 188211; C pulchellus FMNH 209435; C. scaber FMNH 236232. Diplodactylus elderi FMNH 213418. Diploglossus millepunctatus FMNH 19348. Diplolaemus bibronii FMNH 7947. Dipsosaurus dorsalis FMNH 98374-98376, 206188, 249738, 249783, 249785, 249786, 257011; D. dorsalis sonoriensis FMNH 98377, 98378; D. sp. FMNH 229599. Draco bimaculatus FMNH 52212; D. cornutus FMNH 150616; D. haematopogon FMNH 150628; D. lineatus FMNH 142246; D. maculatus FMNH 180834; D. melanopogon FMNH 184776, 184868; D. obscurus FMNH 150698; D. quinquefasciatus FMNH 159679, 213405; D. volans FMNH 52204, 77665, 143024. Echinosaura horrida FMNH 177475. Egernia cunninghami FMNH 31041, 75329; E. stokesii FMNH 51707. Elgaria coerulea NMNH 8626, 11584; E. kingii NMNH 292554; E. multicarinata NMNH 13783, 313412; E. sp. FMNH 213397. Emoia atracostatum KU 20605, NMNH 534092; E. caeruleo- cauda NMNH 323705; E. cyanura NMNH249754; E. jakati NMNH 512285; E. kuekenthali notomoluccense FMNH 134594; E. nigromarginata NMNH 334059; E. trossula NMNH 249744, 249745; E. sp. FMNH 236132. Enyalioides laticeps FMNH 31354; E. palpebralis FMNH 40008. Eumeces algeriensis FMNH 229652; E. brerirostris FMNH 111614; E. brevirostris indubitus FMNH 114201; E. copei FMNH 98509, 98510; E. fasciatus FMNH 9851 1- 98513, 118853; YPM 12689; E. laticeps FMNH 98514, 218437; E. latiscutatus FMNH 5551 1; E. obsoletus FMNH 98515-98521, 196127; E. ochoterenae FMNH 114493. Furcifer pardalis FMNH 250433; F. verrucosus FMNH 72789, 76096. G. sp. FMNH 211251. Gehyra mutilata FMNH 209436, 209437. Gekko gecko FMNH 14448, 31008, 31013, 209438, 213417, 216495; G. sp. FMNH 216516. Gerrhonotus liocephalus FMNH 22452, NMNH 25085; G. monticolus KU 125410; G sp. FMNH 22105. Gerrhosaurus Jlavigularis (personal collection of Kevin de Queiroz 134); G nigrolineatus 15373, 15375; G validus FMNH 22293, 215858, 228400. Gonocephalus grandis FMNH 188196; G liogaster FMNH 151542, 188172, 63709, 210099. Gymnophlhalmus speciosus FMNH 165771, 176990. Heloderma horridum FMNH 22038, 31366, 98776, 250611; H. suspectum FMNH 22232, MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 29 98468, 98469, 98774, 98775, 218077, 229925, TNHC 62767; H. sp. FMNH 22102. Hemidactylus brookii FMNH 209442. 209443; H. fremitus FMNH 98356, 209444- 209447; H. garnotii FMNH 206754; H. leschenaultii FMNH 98355, 196101. Hemitheconyx caudicinctus FMNH 209441. Heteronotia binoei FMNH 195572, 195573. Holbrookia maculata FMNH 98380, 98381; H. macuhitcP. FMNH 98385; H. maculata elegans FMNH 98386-98390; H. sp. FMNH 98379, 98382, 98391. Iguana iguana FMNH 2694, 22041, 22085, 22291, 22492, 51646, 51679, 51680, 128431. 196847, 207655, 211878, 211937, 222373. Isopachys roulei FMNH 196171-196172, 196197- 196200. Japalura swinhonis FMNH 207644, 195575, 207672. Kentropyx calcarata FMNH 31352. 42523. NMNH 292411. 292412. Lacerta lepida FMNH 22098, 22267, 83665. 229612 NMNH 279861; L. viridis YPM 12858, KU 47164, NMNH 258747, 284452. Laemanctus longipes FMNH 213398. Lanihanotus bomeensis FMNH 134711, 148589, 151714, MCZ 8305. Leiocephalus carina- tus armouri FMNH 22754. Leiolepis belliana FMNH 229469. 229470. Lepidophyma flavomaculatum FMNH 22299; L. gaigae FMNH 98560. Lerista elegans FMNH 11319. Lialis burtonis FMNH 22109. Liolaemus chiliensis FMNH 24023. Lygosoma bowringii FMNH 35409, 3541 1, 196173, NMNH 72277; L. fernandi FMNH 12763. Mabuya cumingi NMNH 498999; M. elegans NMNH 336438; M. gravenhorsti NMNH 336440; M. mabouia KU 113519; M. multicarinata NMNH 509420; M. multi- fasciata FMNH 120304, 171520, 229938-229940; M. rudis FMNH 120270, 150823; M. seychellensis NMNH 297506; M. sp. FMNH 22193, 98525, 98526. Meroles anchietae FMNH 82558. Moloch horridus FMNH 233214. O. sp. FMNH 9270. Ophiomorus brevipes FMNH 141550; O. persicus FMNH 141557. Ophisaurus apodus FMNH 22088, 22359, 161121, 216745, YPM 12870; O. attenuates FMNH 98466, 98467, 98911, 207671; O. harti FMNH 24298; O. ventralis FMNH 31006. Pachydactylus bibronii FMNH 209448-209451. Petrosaurus mearnsi FMNH 216151; P. thalassinus FMNH 216154, 229972. Plwlido- holus montium KU 141610-141617. Phrynosoma asio FMNH 31315; P. cornutum FMNH 31311, 98392, 98393; P. coronation blainvilli FMNH 22394, 98954; P. hernandesi FMNH 98394; P. mcallii FMNH 216162; P. platyrhinos FMNH 31289; P. platyrhinos platyrhinos FMNH 216163; P. solare FMNH 22415, 98395, 98396. Phyllodactylus homolepidurus FMNH 98357, 98358; P. lanei FMNH 98359; P. platurus FMNH 252870. Phy- signathus cocincinus FMNH 255017, 98914; P. lesueurii FMNH 22093. 22246. 22245. Plica plica FMNH 31355; P. umbra KU 135267, NMNH 204266. Podarcis lilfordi FMNH 22295; P. sicula FMNH 800212; P. sicula cazzae FMNH 66902; P. sicula cetti FMNH 21645; P. taurica FMNH 213390. Pogona vitticeps FMNH 257083. Poly- chrus femoralis FMNH 81405. Proctoporus bolivianus FMNH 204231; P. meleagris FMNH 28049; P. pachyurus FMNH 134388; P. striatus FMNH 177078. Ptychozoon lionotum FMNH 217383. Ptyodactylus hasselquisti FMNH 210095. Sator angustus FMNH 216166; S. grand- aevus FMNH 216152. Sauromalus ater or obesus FMNH 31015; S. obesus FMNH 22248, 229860; S. obesus town- sendi FMNH 98397. Sceloporus acanthinus FMNH 20156; S. aeneus FMNH 98398, 98399. 98401; S. asper FMNH 32041; S. clarkii FMNH 98402-98414; S. grammicus microlepidotus FMNH 98418, 98425-98431; S. horridus albiventris FMNH 98422; S. lunaei FMNH 64687, 68623, 68627; S. lundelli FMNH 49225, 49226; 5. magister FMNH; S. magister magister FMNH 216159; S. mal- ichiticus FMNH 31039, 210648-210650; S. melanorhinus FMNH 33348, 98424; 5. merriami merriami FMNH 216153; S. nelsoni FMNH 98433, 98434; S. ochoterenae FMNH 102118; S. olivaceus FMNH 216160; S. orcutti orcutti FMNH 216158; S. poinsettii macrolepis FMNH 216157; 5. pyrhocephalus FMNH 98435; S. scalaris FMNH 98436. 216135; S. sceloporus FMNH 98415; S. serrifer cyanogenys FMNH 98416, 98417; 5. siniferus FMNH 98437, 98438, 106501, 1 16292; S. spinosus FMNH 98439, 98440; S. spinosus spinosus FMNH 216156; 5. torquatus torquatus FMNH 216165; 5. undulatus FMNH 98442, 98444; S. undulatus hyacinthinus FMNH 98443; 5. undulatus tristichus FMNH 98441; S. utiformis FMNH 98445-98451; S. variabilis variabilis FMNH 98452. Scin- cella forbesora FMNH 98522; 5. lateralis KU 13932, 16437, NMNH 332758, 451674; S. melanosticta FMNH 180970. Sepsina angolensis FMNH 142793. Shinisaurus crocodilurus FMNH 215541, UF 62497, 62536. Spheno- morphus cyanolaemus FMNH 120244, 239877; S. hallieri FMNH 243813; S. multisquamatus FMNH 138537, 239895; S. nigrolabris FMNH 14255; S. sabanus FMNH 239825. Stenocercus aculeatus KU 121093; S. apurimacus KU 134278, 134284; S. arenarius FMNH 40589; 5. boettgeri KU 134014, NMNH 299613; S. chrysopygus KU 133895, 133906; S. crassieaudatus KU 133859, 163602; 5. empetrus KU 134401, 134403, 134404; S.festae KU 134595, 134603; S. formosus 134110; S. guentheri KU 147319, 147326, NMNH 222584; S. humeralis KU 134001, 134004; S. iridescens KU 142695, NMNH 200912, 222585; S. ochoai KU 133878, 133884; 5. omatus KU 121128, 134128; S. pectinatus KU 187794. 187798; S. praeomatus KU 134229; S. rhodomelas KU 152184, 152186, NMNH 222586, 222587; S. scapularis FMNH 40612; S. trachyce- phalus NMNH 313935-313940; S. varius 121135, 134563, 142704, NMNH 201321. Teius teyou FMNH 170853. Thecadactylus rapicaudus FMNH 13006, 22212, 209454- 209456. Tiliqua nigrolutea FMNH 22498, 23149; T. scincoides FMNH 22091, 22092, 22779, 51702, 51710. 73343, 229975; T. rugosus FMNH 22361, 22470, 22490, 31353, 195570. Trapelus mutabilis FMNH 620, 58293, 58691, 58692, 62589, 63037-63041, 63958, 66131, 66132, 66136, 67207-67209, 67213, 67222, 72588. 72590-72594. Tretiosaurus bifasciatus FMNH 165837. Tropidophorus berdmorei FMNH 106976. 196201; T. brookei FMNH 16584, 129526, 145910, 167971; T. gran FMNH 152399; T. micropus FMNH 151530; T. misaminius FMNH 68926; T. perplexus FMNH 7950. Tropidurus atacamensis KU 161986; T. bogerti NMNH 300598; T. etheridgei KU 186102; T. hoodensis FMNH 22099; T. hygomi NMNH 209644; T. itambere NMNH 148776; T. melanopleurus KU 136370; T. montanus NMNH 218210; T. occipitalis 30 FIELDIANA: ZOOLOGY NMNH 222582; T. peruvianas FMNH 34191, KU 134695; T. spimdosus KU 97856; T. theresoides KU 162012; T. tkoracicus KU 163721; T. tigris KU 163753; T. torquatus NMNH 208276, 208278. Tupinambis teguixin FMNH 18, 22393, 31279, 98759, 161555, 217382, 218521; T. sp. FMNH 31027. Typhlacontias gracilis NMNH 159338. T. ngamiensis FMNH 142787. Typhlosaurus lineatus FMNH 142756. Uma notata notata FMNH 26183, 26228. Uromasty.x accmthinura FMNH 229935, 229959; U. aegyptia FMNH 31030, 31031, 63961, 22247, 22214; U. hardwickii FMNH 98934. U. sp. FMNH 250684. Uro- saurus bicarinutus FMNH 98455; U. omatus FMNH 98456. Uroscanodon supercUiosa NMNH 290895. Uro- saurus omatus lateralis FMNH 98458-98460. Uta stans- buriana FMNH 98461; U. stansburiana taylori FMNH 98462-98465; U. sp. FMNH 98453, 98454. Varanus acanthwus FMNH 218083; V. albigularis FMNH 17143; V. dumerilii FMNH 223194, 228151; V. exanthematicus FMNH 51683, 212985, 228398, 229530; V. gouldii FMNH 31340, 250434; V. griseus FMNH 31308; V. komodoensis FMNH 22199, 22200; V. nebulosus FMNH 22495; V. niloticus FMNH 12300, 17144-17146, 22084; V. olivaceus FMNH 223181; V. omatus FMNH 45087, 58935; V. prasimts FMNH 229907, 229966, 250848; V. rudicollis FMNH 98943, 98946, 98949, 131538; V. sahator FMNH 22204, 31358, 98944, 121145, 211938, 229928, 236130; V. timorensis FMNH 250436; V. sp. FMNH 195576, 218834, 235516. Xantusia vigilis FMNH 22329; X. sp. FMNH 22101. Xenosaurus grandis FMNH 211833. Zonosaurus omatus YPM 12671. Snakes: Acalyptophis peronii FMNH 201920, 215543. Acanthophis antarcticus FMNH 20769, 213076. Achalinus meiguensis FMNH 18777; A. spinalis FMNH 24896. Acrantophis dumerili FMNH 228340, 238160. Acrochordus arafurae FMNH 250808; A. granulatus FMNH 213148- 213151, 213182, 221397, 221398, 231720, 231730, 232777, 232780, 232787, 232789, 232793-232795, 232797-232800, 233200, 233202, 234129, 234131, 234135, 234138, 234139, 234142, 234233, 234234, 234235, 242163, 242177, 242178, 242186, 242187, 242477-242490, 244291-244296, 11081, 51711, 51712, 98780; A. sp. FMNH 98957. Adenorhinos barbouri FMNH 142636. Afronatrix anoscopus FMNH 58135; A. anoscopus FMNH 58138. Agkistrodon bilineatus FMNH 98906-98909, 154775, 204658, 229689; A. bilinea- tus taylori FMNH 250435; A. contortrix FMNH 22268, 22365, 23408, 62059, 166644, 167413; A. contortrix phaeogaster FMNH 98623-98631; A. piscivorus FMNH 21636, 22312, 22325, 98897, 98898, 229910. Ahaetulla mycterizans FMNH 98554, 98555; A. nasuta FMNH 51713, 98877, 229592; A. prasina FMNH 1605, 15067, 148953, 188517, 252115; A. sp. FMNH 250104. Aipysurus nvfoi/.vi/'FMNH 236522, 245557-245638, 251450, 251452- 251469, 251471-251484, unnumbered specimen from series 251450-251484. Alsophis sanctaecrucis FMNH 235. Amblyodipsas unicolor FMNH 74822. Amphiesma craspedogaster FMNH 24788; A. stolatum FMNH 6722, 169407. Anilius scytale FMNH 11175, 35683, 35687, 35688, USNM 204078. Aparallactus lunulatus FMNH 62227; A. wemeri FMNH 81061. Arizona elegans elegans FMNH 6201. Aspidelaps lubricus FMNH 77630; A. lubricus lubricus FMNH 204897. Aspidomorphus muelleri FMNH 13889. Aspidura trachyprocta FMNH 98767, 121479, 131369. Athens chlorechis FMNH 44413; A. hispida FMNH 164740; A. nitschei FMNH 8984, 8987; A. squamigera FMNH 22423, 22424, 98928, 98929, 154890. Atractaspis bibronii FMNH 81140; A. corpulenta FMNH 58069; A. dahomeyensis FMNH 74786; A. irregularis FMNH 58409, 62204, 142994; A. microlepidota FMNH 51682, 58397, 62192. Atractus elaps FMNH 23485; A. erythromelas FMNH 3993; A. latifrons FMNH 11190; A. ventrinuiculatus FMNH 3995. Atropoides nummifer FMNH 22454, 27125, 31042. Azemiops feae FMNH 218628. Bitia hydroides FMNH 229792, 229794. Bitis arietans FMNH 11006, 22258, 22277, 22387, 31316, 98919, 154895, 167057, 196152; B. atropos FMNH 143000; B. caudalis FMNH 17198, 17200, 165150, 187154; B. gabonica FMNH 22254, 51634, 51635, 51698, 166640, 167433; B. heraldica FMNH 166959; B. nasicomis FMNH 3996, 19457, 31003, 98875, 98876, 154776, 229895, 229896; B. peringueyi FMNH 82544, 82545; B. sp. FMNH 167437. Boa constrictor FMNH 22407, 22427, 22438, 22439, 22458, 31182, 211860, 211926, 216950; B. constrictor constrictor FMNH 1 1 163, 22362, 22372, 22435, 22444, 22453; B. constrictor imperator FMNH 22256, 22323, 22353, 22363, 31188, 166520. Bogertophis subocu- laris FMNH 75860. Boiga blandingii FMNH 19449, 121974; B. ceylonensis FMNH 123475; B. cyanea FMNH 180046; B. cynodon FMNH 131814, 145840, 158653, 168006; B. dendrophila FMNH 11128, 31282, 31305, 31347, 145847, 210098, 211908, 211941; B. drapiezii FMNH 131805, 145684, 178613; B. forsteni FMNH 165052; B. irregularis FMNH 98931, 121869, 142119; B jaspidia FMNH 129437, 148822; B. kraepelini FMNH 127971; B. multomaculata FMNH 6674; B. nigriceps FMNH 128150; B pulverulenta FMNH 44417; B. trigonata FMNH 83087, 83089; B. sp. FMNH 212401. Bothriechis marchi FMNH 31291, 31292, 31304; B. schlegelii FMNH 2524, 51688. Bothriopsis pulchra FMNH 165593; B. punctata FMNH 55888. Bothrochilus boa FMNH 13882, 21729. Bothrophthalmus lineatus FMNH 44406. Bothrops altematus FMNH 51663; B. amniody- toides FMNH 10831; B. asper FMNH 3480, 20641, 23796, 31167, 51689, 197882; B. atrox FMNH 51658; B burnetii FMNH 9788; B. brazili FMNH 165563; B. cotiara FMNH 51662; B. itapetiningae FMNH 10815; B. jararaca FMNH 69951; B. jararacussu FMNH 51659, 51660; B. micro- phthalmus FMNH 63740; B. moojeni FMNH 171278; B. neuwiedi FMNH 35743, 51661; B. sp. FMNH 9742. Boulengerina annulata FMNH 214756. Bungarus caeruleus FMNH 1651 15; B. candidus FMNH 180054; B. ceylonicus FMNH 178377; B. fasciatus FMNH 11542; B. flaviceps FMNH 145854; B. multicinctus FMNH 167970, 213121- 213127, 213137-213141; B. sp. FMNH 98953. Cacophis haniettae FMNH 97006. Calabaria reinhardtii FMNH 19478, 31372. 191123. Calamaria gervaisii FMNH 15025; C. leucogaster FMNH 71598; C. linnaei FMNH 100870; C. pavimentata FMNH 1 1528; C. schlegelii FMNH 69977; C. septentrionalis FMNH 7139. Calloselasma rhodostoma MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 31 FMNH 11522. Candoia aspera FMNH 13915, 21731; C. bibroni australis FMNH 22997; C carinata FMNH 217065, 249734, 249736, 250097; C. sp. FMNH 250845. Cantoria violacea FMNH 250115. Carphophis amoenus FMNH 98527, 98528, 196133, 196140; Carphophis vermis FMNH 8766, 22478, 22479, 98529-98532, 98534. Causus defllippii FMNH 81133, 81134; C. resimus FMNH 62182, 62183; C rhombeatus FMNH 2268, 51693, 58066, 164744. Cemophora coccinea FMNH 427. Cerastes cerastes FMNH 142986, 142990, 142991, 142993-143996, 153114; C. vipera FMNH 22379, 79181, 82300, 154893, 154894, 195969. Cerberus rynchops FMNH 219845- 219848, 219850, 219851, 242148, 250103, 250109. 251509-251516. Cerrophidion barbouri FMNH 38503; C godmani FMNH 20264. Charina bottae FMNH 1218, 22348, 31300. Chilomeniscus stramineus FMNH 1125, 130286. Chilorhinophis carpenteri FMNH 81022, 81032. Chironius carinatus FMNH 21997, 51690, 201009; C. exoletus FMNH 61662; C. fuscus FMNH 21998, 98758. Chrysopelea omata FMNH 11566, 23426, 180063, 252867-252869; C. paradisi FMNH 67300; C pelias FMNH 98749, 98750; C sp. FMNH 229593. Clelia clelia FMNH 4448. Clonophis kirtlandii FMNH 16126. Coluber constrictor FMNH 98536, 135284, 191781, 196109, 196187, 196188, 216633; C constrictor flaviventris FMNH 3275, 22251, 22261, 22347, 23390, 98537. 211857; C florulentus FMNH 153054; C gemonensis FMNH 21451; C. hippocrepis FMNH 15747; C jugalaris FMNH 19623, 26383; C ravergieri FMNH 19617; C. rhodorhachis FMNH 31649; C rogersi FMNH 19588, 69262; C rubriceps FMNH 22811; C. 5p/nfl/is FMNH 67129; C. ventromaeulatus FMNH 19506, 26357; C. viridiflavus FMNH 51694; C sp. FMNH 229927. Coniophanes fissidens fissidens FMNH 2291 1 . Conophis lineatus FMNH 10999; C lineatus'? FMNH 98542, 98543; C sp. FMNH 98540. Conopsis lineata lineala FMNH 987; C. nasus FMNH 39053; Conopsis? FMNH 98539, 98541; C sp. FMNH 98538. Corallus caninus FMNH 223192, 223193, 229856; C. cooki FMNH 212337; C hortulanus enhydris FMNH 229903-229905. Coronella austriaca FMNH 51623; C. austriaca austriaca FMNH 22810. Crotalus adamanteus FMNH 22205, 22381, 31050, 31051, 51640, 98757, 218079; C atrox FMNH 8484, 15236, 22243, 22244, 22331, 31010, 98632, 98892-98896, 98918, 167407, 167410, 167411, 167417-167421, 167425-167427, 167429, 167434, 167668, 238179-238193, 251262; C basilicas FMNH 31299; C. cerastes FMNH 1243, 26122, 98904, 167431, 167432; C durissus terrificus FMNH 1731, 20160, 51664; C horridus FMNH 3502, 22271, 22335, 98633- 98635, 98901-98903, 98927, 98932, 98933, 223670; C lepidus FMNH 22317; C lepidus klauberi FMNH 900; C, lepidus lepidus FMNH 23787; C. mitehelli pyrrhus FMNH 1159; C. molossus FMNH 167435; C. molossus molossus FMNH 4770; C. ruber FMNH 5997, 8050, 31290; C. scutulatus FMNH 223668, 231611; C viridis FMNH 22272, 22282, 22283, 22316, 98888, 98890, 98891, 167416, 167428; C viridis helleri FMNH 5993; C viridis oreganus FMNH 207914. Crotaphopeltis hotamboeia FMNH 4036. Cyclophiops major FMNH 18746, 23443, 127952, 127953, 127955, 127966-127968. Daboia russelii FMNH 22456, 31007, 31363, 154896, 166638. 167121, 167405, 167436. Cylindrophis maculatus FMNH 142395; C. ruffus FMNH 13100, 60958, 69980, 69981, 131778. 179033. Dasypeltis faseiata FMNH 19455; D. scabra FMNH 17677, 51695, 62212, 142635. Deinagkistrodon acutus FMNH 25177. Dendrelaphis pictus FMNH 41100. Dendroaspis angusticeps FMNH 17653, 51699, 74069, 251189; D. jamesoni FMNH 75076; D. viridis FMNH 31325, 31346; D. sp. FMNH 98921. Dendrophidion hrunneus FMNH 232577, 232578, 232580-232582. Diado- phis punctatus FMNH 3513, 11821, 98546, 98547, 196142, 196153; D. punctatus arnyi FMNH 98548-98552; D. punctatus edwardsii FMNH 207629, FMNH 207630. Dinodon rufozonatum FMNH 11429, 18733; D. rufozona- tum rufozonatum FMNH 7091. Dipsadoboa unicolor FMNH 44415. Dipsas latifrontalis FMNH 23532. Dis- pholidus typus FMNH 17679, 74263, 251190. Dromico- dryas bernieri FMNH 75596. Dromophis lineatus FMNH 12876. Drymarchon corais couperi FMNH 22228, 22305, 22367; D. corais erebennus FMNH 98553; D. melanurus FMNH 31706. Drymobius margaritiferus FMNH 1310. Dryophiops rubescens FMNH 183765. Drysdalia coro- noides FMNH 29116. Echis carinatus FMNH 65914, 65918, 73543, 121567, 154889, 154891, 154892; E. color- atus FMNH 143999. Eirenis rothii FMNH 21910. Elaphe carinata FMNH 21971, 24901; E. dione FMNH 7119, 7121; E. flavirufa FMNH 1452; E. guttata FMNH 8623, 22484, 22489, 257100; E. mandarina FMNH 18695; E. obsoleta FMNH 22179, 22343, 98556, 196093, 257061; E. obsoleta obsoleta FMNH 22196, 22371, FMNH 98557- 98559; E. obsoleta quadrivittata FMNH 212336, 223699; E. porphyracea FMNH 7102, 11794; E. quatuorlineata sauromates FMNH 249735; E. radiata FMNH 15824; E. rufodorsata FMNH 22341, 212395-212397, 212851; E. schrenckii FMNH 7066, 216547; E. taeniura yunnanensis FMNH 16804; E. vulpina FMNH 22250, 211940, 251143, 251519, 256996, 257009, 257481. Elapsoidea semiannulata FMNH 78220. Emydocephalus ijimae FMNH 120880. Enhydrina schistosa FMNH 199036, 199137, 199555, 199601, 201769, 203065, 203066, 203074. 203076, 203082, 203091, 203123, 206707, 234226, 306697. Enhydris bocourti FMNH 11549; E. chinensis FMNH 167439, 207645; E. doriae FMNH 129420; E. enhydris FMNH 252598-252608, 252686-252688; E. plumbea FMNH 98768, 120575-120579, 251282, 251283, 251572-251588. Ephalophis greyae FMNH 212365. Epicrates angulifer FMNH 250425; E. cenchria FMNH 22292, 22443, 22486; E. cenchria mounts FMNH 22848; E. stria tus FMNH 13272, 130984; E. sp. FMNH 223197. Eristicophis macmahoni FMNH 140280, 165151. Erpeton tentaculatum FMNH 210072. Erythrolamprus aesculapii FMNH 2621, 10800. Eryx jaculus FMNH 19624; E. johnii FMNH 23534, 31319. Eunectes murinus FMNH 8546, 22776, 39465, 45700, 212710, 232745; E. murinus gigas FMNH 31665; E. notaeus FMNH 229918, 9084, 229857-229859, 229919, 229921. Farancia abacura FMNH 8570, 22320, 22364, 257099; F. abacura abacura FMNH 31327; F. erytrogramma FMNH 5731. Ficimia publia FMNH 20635. 32 FIELDIANA: ZOOLOGY Fimbrios klossi FMNH 71698. Geophis semidoliatus FMNH 98561. Gloydius saxatalis FMNH 11484; G straucbi FMNH 15134. Gongylophis colubrinas FMNH 223196; G colubrinus colubrinus FMNH 75214. Gonyo- soma frenatwn FMNH 22345. Grayia smythii FMNH 20820. 51701. 214761, 214763, 214770. Hapsidophrys lineatus FMNH 4021; H. smaragdina FMNH 4023. HeUcops angulatus FMNH 5691, FMNH 217108; H. curinicaudus FMNH 11500. Heterodon nasicus FMNH 15993, 15994, 22455. 25418, 251 144; H. platirbinos FMNH 3387, 4136, 22259, 22270, 22314, 22315, 22324, 22332, 22447-22449, 31306, 210651, 210652, 251261, 257008; H. simus FMNH 4765, 25964. Homalopsis buccata FMNH 1929, 117860, 252680-252685, 252689, 252690. Homoro- selaps lacteus FMNH 187420, 187421, 204893, 206416. Hoplocephalus bitorquatus FMNH 97311. Hydrodyiutstes bicinctus FMNH 131629; H. gigas FMNH 31318, 31356, 229936. Hydrophis bekheri FMNH 13612, 22994; H. brooki FMNH 178861. 178866, 178868; H. coggeri FMNH 13611; H. cyanocinctus FMNH 23421, 171752. 171753, 213154-213158, 215840, 231639-231644, 231712, 231713. 231716, 231717, 232747, 232748, 232757, 232763- 232766, 232770, 233205. 234182, 234200-234217, 234219, 234220, 234222-234224, 242169, 245525-245539, 245540- 245551, 249396, 249397, 249400, 249401, 249406, 249408- 249410; H. elegans FMNH 216270; H. fascial us FMNH 141143, 249348-249351, 249353-249357, 249468- 249473, 249475-249477, 249547, 249549, 249618- 249628; H. klossi FMNH 165003, 165006; H. lapemoides FMNH 73996, 242175, 242176, 242220-242224, 249187- 249191, 249440, 249446-249448, 249450-249453; H. mela- nosoma FMNH 171754, 201 1 14, 201 1 16, 201 1 18, 201 120, 201121, 201124, 202169, 202170, 206714, 206716; H. omatus FMNH 201132, 202926, 234172, 249311-249316, 249318-249344; H. spiralis FMNH 242172, 242173, 242180-242184, 242226, 248799, 249306-249310, 249454, 249551-249553, 249615-249617, 249654; H. torquatus FMNH 201133, 201168; H. sp. FMNH 231708, 234185, 248826. Hypnale hypnale FMNH 122513; H. nepa FMNH 121450. Imantodes cenchoa FMNH 22223, 31035, 221400; /. tennissimus FMNH 20612. Kerilia jerdonii FMNH 133059, 178775, 242188, 249655. Lachesis mula FMNH 31748, 31749, 98753. Lanwro- peltis alterna FMNH 257010; L. geiula californiae FMNH 22313, 22321, 22483, 23234; L. getula holbrooki FMNH 22445, 31280, 31296, 212393; L. getula splendita FMNH 31310; L. triangulum elapsoides FMNH 19312; L. triangulum hondurensis FMNH 250685; L. triangulum polyzona FMNH 4200; L. triangulum triangulum FMNH 22269, 98566, 207626, 252408; Lampropbis fuliginosus FMNH 214776, 214777; L. lineatus FMNH 9916, 17698, 17702, 51684, 51697, 81103, 81105; L. olivaceus FMNH 19473. Lapemis curtus FMNH 122529, 141158. 141159, 141161, 142063, 198402, 198410, 198442, 198443, 198466, 198918, 210065- 210070, 210090, 210165, 213159, 213160, 213162-213164, 213168, 213169, 213171, 213173, 213175-213179, 213229, 215262, 215264, 215276, 230014, 230019, 230021, 230022, 230028, 230032, 230051-230058, 231376, 231731-231748, 234118, 234121, 234128, 234169, 234228-234232, 235469, 235474, 235476-235478, 235480-235483, 235490, 235493, 235496-235504, 235506-235509, 235511-235515, 242126, 242128, 242146, 249192. Laticauda colubrina FMNH 13820, 210061-210064, 234147-234166, 235388-235395, 235398- 235425, 236238, 236245, 236251, 236279, 236285-236292, 236294-236301, 236303-236314, 236318, 236320, 236322- 236325, 236327-236329, 236341, 236345, 236347-236349, 236354, 236357-236374, 236523, 244183-244202, 248797, 248798; L. laticaudata FMNH 154782, 202812, 202813, 242185; L semifasciata FMNH 106060, 120644, 120650, 120651. Leiapytbon albertisi FMNH 218609. Leptodeira maculata FMNH 98622; L. septentrionalus polysticta FMNH 4815, 4816, 8934, 31343. Leptomicrurus nar- duccii FMNH 5700, 62127. Leptophis ahaetulla FMNH 5292, 5294, 54974; L. mexicanus FMNH 193, 22257. Lepturoplus borneensis FMNH 148896. Lichanura tri- virgata roseofusca FMNH 8043, 31365. Limnopbis bieolor FMNH 18523. Liobeterodon madagascariensis FMNH 75591. Liopbis epinephelus FMNH 232562, 232563; L. miliaris FMNH 15420; L. poecilogyrus FMNH 35699. Lioplwlidopbis lateralis FMNH 75615. Lycodon aulicus FMNH 15060; L. striatus FMNH 121510. Lyeopbidion eapense vermieulatum FMNH 81086. Lystropbis dorbignyi FMNH 9508, 10199; L. semicinctus FMNH 10863. Lytorbyncbus diadema FMNH 164704; L. maynardi FMNH 167666. Macro- calamus lateralis FMNH 109943. Macropisthodon rudis FMNH 24952. Macrovipera lebetina FMNH 19601, 65218. Malpolon moilensis FMNH 72083; M. monspes- sulanus FMNH 19615. Masticophis flagellum FMNH 22344, 22461, 98568, 257101, 258769; M. jlagellum flagellum FMNH 21922, 22229, 22377; M. flavigularis flavigularis FMNH 213416; M. schotti FMNH 6801; M. sp. FMNH 98567. Mastigodryas bifossatus FMNH 9243, 51669; M. beathii FMNH 232583. Mebelya capensis FMNH 13129; M. poensis FMNH 19467. Microcephalophis gracilis FMNH 171755, 249464. Mi- cruroides euryxantbus FMNH 41952. Micrurus fulvius FMNH 6804, 39479, 229600; M. fulvius fulvius FMNH 34982; M. nigrocinctus FMNH 16119, 31101, 31104, 31109, 210092-210094; M. spixii princeps FMNH 22592; M. sp. FMNH 200569. Montatberis hindii FMNH 154720. Morelia ametbistina FMNH 212271. 218599, 232744, 257051; M. spilota FMNH 21714, 22234, 22380, 22420, 218598; M. viridis FMNH 21733, 207854, 211850, 213403. Naja atra FMNH 6635; N. kaouthia FMNH 15823; N. naja FMNH 22044, 22408, 22421, 31361, 212312, 212313, 212333-212335, 212398-212400, 212526, 212527, 212529-212532, 212581- 212583,212585-212587; N. nigricollis FMNH 222374; N. nivca FMNH 17656, 31359; N. sp. FMNH 98920. Natrix natrix FMNH 51620; N. tessellata FMNH 19604. Nerodia eyelopion FMNH 22274, 95326; N. erythrogaster FMNH 22309, 22310; N. erytbrogaster transversa FMNH 98574-98576; N. fasciata FMNH 22390, 217640; N. fasciata pietiventris FMNH 211920; N. floridana FMNH 95329; N. rhombifer FMNH 2664, 22306-22308, 22319, 98955; N. sipedon FMNH 22047, MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 33 22262, 22284, 98569-98572, 216226; N. sipedon sipedon FMNH 98573; N. taxispilota FMNH 8220, 31295; N. sp. FMNH 250849. Neusterophis variegatus FMNH 179356. Ninia sebae FMNH 20359. Notechis scutatus FMNH 11123. 11127. 20770. Oligodon albocinctus FMNH 11795; O. cyclurus FMNH 14434; O. fasciola- tus FMNH 169437; O. formosanus FMNH 6691, 24961; O. octolineatus FMNH 100901. 129423; O. laeniatus FMNH 119662; O. violaceus FMNH 6700, 6703. Opheodrys aestivus FMNH 8603, 21259. 21260, 211917; O. vernalis FMNH 16149, 22227, 22304, 98578-98581. 217395. Ophiophagus hannah FMNH 22275, 22276, 22409, 22482, 98765. Ophryacus undulatus FMNH 38505. Opisthotropis latouchi FMNH 24865. Orophis monticola FMNH 18760. 25187; O. okinavensis FMNH 45074. Oxybelis aeneus FMNH 10998, 22231, 22355, 31037. 98913; O. argenteus FMNH 16789; O. fulgidus FMNH 4207, 5301. 5302, 22369, 22376, 25250. Oxyrhabdium modeslum FMNH 96532, 98858. Oxyrho- pus petola digitalis FMNH 11193; O. petola sebae FMNH 20094. Pareas margaritophorus FMNH 6661. Pelamis platurus FMNH 51637-51639. 154882, 171581, 171613, 171628. 171632. 171644. 171652. 171671, 171680, 171690, 171701. 216510, 216517, 216518, 216519, 216538-216542, 217156-217158, 217397, 218435, 218439. Philodryas chamissonis FMNH 6401, 209130, 210381, 210382. 210386; P. elegans FMNH 34281, 34313, 39372; P. elegans rufidorsatus FMNH 41595; P. patagoniensis FMNH 19395, 51667; P. simonsii FMNH 232579. Philothamnus irregularis FMNH 12967. Phimophis guianensis FMNH 22579. Phyllorhynchus decurtatus FMNH 22419, 31284; P. decurtatus perkinsi FMNH 18419. Pituophis catenifer FMNH 3417. 22221, 22487, 98582-98584, 191778, 191779, 196100. 229894, 250590, 251141, 251142. 251260, 256997; P. deppei FMNH 1497; P. melanoleu- cus FMNH 22342. 22356, 211907, 212394. 217641. 258730. Plagiopholis styani FMNH 24873. Polemon collaris FMNH 58999. Porthidium dunni FMNH 104676; P. yucatanicwn FMNH 36181. Protobothrops jerdonii FMNH 28199; P. mucrosquamatus FMNH 16255, FMNH 140101. Psammodynastes pictus FMNH 148905, 148907; P. pulverulentus FMNH 24997, 53485. 53501. Psammophis phillipsi FMNH 12976; P. schokari FMNH 129758, 129760, 129762; P. sibilans sibilans FMNH 72044, 72050, 72070; P. subtaeniatus sudanensis FMNH 51687. Pseudaspis carta FMNH 16044, 51628, 51696. Pseudechis australis FMNH 166929; Pseudechis porphyriacus FMNH 11119, 11120, 20797, 22318. Pseudocerastes persicus FMNH 207656. Pseudoeryx plicatilis FMNH 26638. Pseudonaja textilis FMNH 11122, 169700. Pseudorabdion collaris FMNH 120377; P. longiceps FMNH 71596. Pseudoxenodon macrops sinensis FMNH 7757. Pseustes poecilonotus FMNH 16755, 98771, 217107; P. sulfurens sulfurens FMNH 22327. Ptyas dhumnades FMNH 22340; P. fuscus FMNH 145833; P. korros FMNH 24851; P. mucosus FMNH 22045, 24857, 31026, 31029; P. nigromarginatus FMNH 18728. Python curtus FMNH 22472, 212308. 222372; P. molurus FMNH 207647, 218576; P. molurus bivittatus FMNH 223198; P. regius FMNH 31033. 223195; P. reticulatus FMNH 15678. 31281. 31324, 211852; P. sebae FMNH 8545. 11162, 11170. 13121, 22366. 196592; P. sp. FMNH 218979. Pythonodipsas carinata FMNH 170024. Regina septemvittata FMNH 16132. Rhabdophis tigrinus FMNH 16839. Rliamnophis aethiopissa FMNH 19476, 19477. Rlwmphiophis oxy- rhynchus rostratus FMNH 16143, 51686. Rhinobothrywn bovallii FMNH 55883. Rhinocheilus lecontei FMNH 22418. 22488. Sahadora grahamiae FMNH 98585, 98586; S. grahamiae grahamiae FMNH 22370; S. grahamiae lineata FMNH 41688. Sanzinia madagascar- iensis FMNH 109899. Scaphiophis albopunctatus FMNH 27350; S. albopunctatus albopunctatus FMNH 51685. Siby?wi7iorphus ventrimaculatus FMNH 9259. Siby?wphis bivittatus FMNH 53368; S. geminatus FMNH 131202; 5. Sagittarius FMNH 131411. Simose- laps bertholdi FMNH 152149; S. semifasciatus FMNH 152144. Sinomicrurus japonicus FMNH 48797. Sinona- trix aequifasciata FMNH 24762; S. annularis FMNH 24766: S. percarinata FMNH 18751: S. trianguligerus FMNH 98942, 128409. 210104. Siphlophis cervinus FMNH 31196. Sistrurus catenatus FMNH 432. 11034, 22230, 22273, 22311, 22346, 216239: 5. miliarius FMNH 21761. 22388. 98899. 98900. 98930: 5. miliarius barbouri FMNH 484553; 5. ravus FMNH 113016. Sonora semiannulata FMNH 46496. 98587. Spaleroso- phis diadema FMNH 22777. 63128, 75241. 153046; S. diadema schiraziana FMNH 20894. Spilotes pullatus FMNH 51668. 218436. 257007; 5. pullatus mexicanus FMNH 4205. 5291. Stenorrhina degenhardtii FMNH 232576; S. fremimillei FMNH 36018. Stilosoma ex- tenuatum FMNH 48441. Storeria dekayi FMNH 22235. 98588-98590: S. occipitomaculata FMNH 98591-98594. 207632. 207633. Symphimus mayae FMNH 36385. 36387. Tantilla gracilis FMNH 18597, 30048, 30123, 30135. 98595, 98596. 98746. Telescopus fallax iberus FMNH 19499; T. semiannulatus semiannulatus FMNH 57656. Thalassephina viperina FMNH 198480, 215559. 215561. Thamnophis butleri FMNH 15562, 21567; T. eques FMNH 2037, 98598: T. marcianus FMNH 565, 98602-98604; T. proximus FMNH 23693, 98605. 98606; T. radix FMNH 22050-22052, 98599-98601, 217214; T. sirtalis FMNH 22357, 22358, 217155, 217396, 217639. 258770; T. sirtalis parietalis FMNH 98607, 98608. 98618, 196148; T. sirtalis sirtalis FMNH 98609-98617, 207627, 207628; T. valida FMNH 98577. Thelotomis capensis capensis FMNH 17676; T. kirtlandii FMNH 98748. Thrasops flavigularis FMNH 19470. Toluca lineata FMNH 98856. 98857; T. lineata varians FMNH 98544, 98545. Tomodon degener FMNH 9370, 12358. Tretanorhinus mocquardi FMNH 16752. Trimeresurus albolabris FMNH 6710, 6713; T. flavomaculatus FMNH 53562; T. popeiorum FMNH 67273; T. puniceus FMNH 131847; T. stejnegeri FMNH 14430, 25195, 127229, 127233, 127238; T. sumatranus FMNH 71644, 216567. Trimorphodon biscutatus FMNH 223666, 223667; T. biscutatus lambda FMNH 98621. Tripanurgos compres- 34 FIELDIANA: ZOOLOGY sus FMNH 221399. Tropidoclonium lineatum FMNH 98619, 98620. Tropidodipsas fischeri fischeri FMNH 20257. Tropidolaemus wagleri FMNH 71640, 129468. Tropidophis partialis FMNH 233. Typhlops punctatusl lineolatus FMNH 31371. Uromacer catesbyi FMNH 18357; U. oxyrhynchus FMNH 5986. Uropeltis melano- gaster FMNH 167048. Vermicella annulata FMNH 24103, 97926. Vipera ammodytes FMNH 21762, 98912, 142997; V. aspis FMNH 23438; V. berus FMNH 166671, 167120; V. palaestinae FMNH 48522; V. renardi FMNH 134381. Virginia striatula FMNH 98562-98564; V. valeriae elegans FMNH 11050, 98565. Waglerophis merremii FMNH 51665, 51666. Walterin- nesia aegyptia FMNH 69240. Xenelaphis hexagonotus FMNH 128269. Xenochrophis piscator FMNH 7060. Xenodermus javanicus FMNH 67427. Xenodon merremi FMNH 195870, 195884, 195896; X. rabdocephalus FMNH 21775; X. rabdocephalus mexicanus FMNH 49349; X. severus FMNH 11198. Xenopeltis tricolor FMNH 122000, 138682, 148900, 178975, 246193. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 35 Fig. 1. (A) CT scan showing ventral view of the skull in Brachylophus fasciatus (FMNH 210158). (B) Ventral view of pterygoids of Ctenosaura sp. (FMNH 6175). (C) Ventrolingual view of right pterygoid tooth row oflguana iguana (FMNH 51679). (D) SEM micrograph showing ventral view of pterygoids of Ctenosaura sp. (FMNH 98370). (E) SEM micrograph showing ventrolabial view of right pterygoid teeth of C. similis (FMNH 21 1849). (F) SEM micrograph showing lingual view of left maxillary teeth of C. similis (FMNH 21 1849), for comparison to E. Anterior toward top in A B and D. Anterior to right in C. Anterior to left in E -F. Scale bar equals 1 cm in A, 1 mm in B-F. 36 FIELDIANA: ZOOLOGY Fig. 2. (A, B) Transverse sections through right pterygoid of Crotaphytus collaris (FMNH 210169), seen in posterior aspect. (C, D) Transverse sections through right pterygoid of C. collaris (FMNH 210169), seen in posterior aspect, showing tooth replacement. Medial to left in all. Scale bar equals 0.1 mm in all. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 37 Fig. 3. (A) CT scan showing ventral view of the skull in Aspidoscelis tigris (FMNH 161622). (B) SEM micrograph showing ventrolabial view of left pterygoid teeth in A. deppei (FMNH 98492). Anterior to right. (C) SEM micrograph showing labial view of right pterygoid teeth in Kentropyx cakarata (FMNH 31352). Anterior to left. (D) SEM micrograph depicting ventrolabial view of right pterygoid teeth in Aspidoscelis sp. (FMNH 98470), showing cusps. Anterior to left. (E) SEM micrograph depicting lingual view of left maxillary teeth in Aspidoscelis sp. (FMNH 98470). for comparison to D. Anterior to left. Scale bar equals 1 mm in A. 0.1 mm in B-D, 1 mm in E. 38 FIELDIANA: ZOOLOGY Fig. 4. (A) Transverse section through left pterygoid of Aspidoscelis tigris (FMNH 1 1 5480), seen in posterior aspect, showing early tooth germ formation in pterygoid cavity. (B) Transverse section through left pterygoid of A. tigris (FMNH 1 15480), seen in posterior aspect, showing developing tooth germ in pterygoid cavity. (C) Transverse section through left pterygoid of A. tigris (FMNH 115480), seen in posterior aspect, showing developing tooth attachment. (D) Transverse section through left pterygoid of A. tigris (FMNH 115480), seen in posterior aspect, showing a fully ankylosed tooth. Medial to right in all. Scale bar equals 0.1 mm in all. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 39 Fig. 5. (A) CT scan showing ventral view of the skull in Colobosaura modesta (USNM 341978). (B) SEM micrograph showing anteroventral view of right pterygoid teeth in G. speciosus (FMNH 165771). (C) SEM micrograph showing mesiolabial view of left pterygoid teeth of G. speciosus (FMNH 165771). Anterior toward top in A and toward bottom in B, C. Scale bar equals 1 mm in A, 0.1 mm in B~C. Fig. 6. (A. B) Transverse section through right pterygoid of Gymnophthalmus speciosus (FMNH 176990). seen from posterior aspect, showing developing tooth germ. Medial to left in both. Scale bar equals 0.1 mm in both. Medial to left in both. 40 FIELDIANA: ZOOLOGY Fig. 7. (A) CT scan showing ventral view of the skull in Lacerta viridis (YPM 12858). (B) SEM micrograph depicting ventral view of left pterygoid teeth in L. lepida (FMNH 22098), showing older, more worn teeth medial to actively replacing teeth. Anterior toward left. (C) SEM micrograph depicting ventrolabial view of right pterygoid teeth in L. lepida (FMNH 22098), showing active replacement. Anterior toward left. Scale bar equals 1 mm in all. Fig. 8. (A, B) Transverse section of right pterygoid of Lacerta lepida (FMNH 83665), seen in posterior aspect, showing developing replacement tooth labial to ankylosed tooth. Medial to left in all. Scale bar equals 0.1 mm in all. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 41 Fig. 9. (A) CT scan depicting ventral view of the skull in Eumeces fasciatus (YPM 12689). (B) SEM micrograph showing labial view of right pterygoid teeth of E. fasciatus (FMNH 98513). Anterior to left. (C) SEM micrograph depicting mesiolabial view of left pterygoid teeth in Corucia zebrata (FMNH 257163), showing crown form. Anterior to right. (D) SEM micrograph depicting lingual view of right maxillary teeth in C. zebrata (FMNH 257163), for comparison to C. Anterior to right. Scale bar equals 1 mm in A, 0.1 mm in B. 1 mm in C-D. V* ^Bfil*ii*Ir -*W^^~|^j /,~ ^| , > ^MxSHy' gutter - "St pt tooth h~. - € jM Fig. 10. (A) Transverse section through right pterygoid of Eumeces fasciatus (FMNH 118853), seen from posterior aspect. (B) Transverse section through right pterygoid of E. fasciatus (FMNH 118853), seen from posterior aspect, showing detail of tooth undergoing labial replacement. Medial to left in both. Scale bar equals 0.1 mm in both. 42 FIELDIANA: ZOOLOGY Fig. 11. (A) CT scan showing ventral view of the skull in Zonosaurus ornatus (YPM 12671). (B) SEM micrograph showing ventrolabial view of right pterygoid of Gerrhosaurus nigrolineatus (FMNH 15375), demonstrating replacement. Anterior to left. (C) SEM micrograph showing ventral view of pterygoid tooth rows in G. validus (FMNH 215858). Anterior toward top. (D) SEM micrograph showing mesiolabial view of left pterygoid teeth in G. validus (FMNH 22293). Anterior to right. (E) SEM micrograph showing lingual view of right maxillary teeth in G. validus (FMNH 22293). Anterior to right. Scale bars equal 1 mm. pt tooth Fig. 12. (A) Transverse section through right pterygoid of Gerrhosaurus nigrolineatus (FMNH 15373), seen from posterior aspect, showing tooth undergoing lingual replacement. Medial to left. (B) Transverse section through left pterygoid of G nigrolineatus (FMNH 15373), seen from posterior aspect, showing tooth undergoing labial replacement. Medial to right. Scale bar equals 0.1 mm in both. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 43 Fig. 13. (A) CT scan showing ventral view of the skull in Shinisaurus crocodilurus (FMNH 215541). (B) Labial view of right pterygoid tooth row in 5. crocodilurus (UF 62536), showing tooth bases surrounded by attachment tissue. Anterior to left. (C) SEM micrograph depicting ventrolabial view of right pterygoid teeth in S. crocodilurus (UF 62536). showing implantation within a longitudinal gutter in the pterygoid. Anterior to left. Scale bar equals 1 mm in all. 44 FIELDIANA: ZOOLOGY This page was intentionally left blank. Fig. 14. (A) CT scan showing ventral view of the skull in Ophisaurus apodus (YPM 12870). (B) SEM micrograph showing ventral view of the left vomer in O. apodus (FMNH 22359). (C) SEM micrograph showing ventrolabial view of the right palatine in O. apodus (FMNH 22359). (D) SEM micrograph showing ventral view of the right pterygoid in O. apodus (FMNH 22359). Anterior toward top in A. Anterior to left in B-D. Scale bar equals 1 cm in A, 0.1 mm in B, 1 mm in C-D. 46 FIELDIANA: ZOOLOGY Fig. 15. (A) Transverse section of right pterygoid of Ophisaurus apodus (FMNH 161 121), seen in posterior aspect, showing replacement tooth germ in fold of dental lamina. (B) Transverse section of right pterygoid of O. apodus (FMNH 161121), seen in posterior aspect, showing several tooth germs developing within a single fold of dental lamina; note the incompletely resorbed pterygoid tooth bases dorsal to the developing teeth. (C) Transverse section of right pterygoid of O. apodus (FMNH 161121), showing two ankylosed teeth (left) and one developing tooth bud (right). (D) Transverse section of right pterygoid of O. apodus (FMNH 161 121), seen in posterior aspect, showing a functional tooth ankylosed adjacent a partially resorbed, more medial tooth. Medial to left in all. Scale bar equals 0.1 mm in all. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 47 Fig. 16. (A) CT scan showing ventral view of the skull of a juvenile Heloderma suspectum (TNHC 62767). (B) SEM micrograph showing mesiolingual view of right pterygoid tooth row in H. suspectum (FMNH 98469). Anterior toward right. (C) SEM micrograph depicting ventral view of right pterygoid tooth in H. suspectum (FMNH 218077). showing plicidentine at tooth base. Anterior toward left. (D) SEM micrograph depicting distolingual view of right maxillary teeth in H. suspectum (FMNH 98469). Anterior toward right. Scale bar equals 1 mm in A. 0.1 mm in B^C. 1 mm in D. 48 FIELDIANA: ZOOLOGY This page was intentionally left blank. Fig. 17. (A) CT scan showing ventral view of the skull of Lanthanotus borneensis (FMNH 148589). (B) SEM micrograph showing ventral view of left pterygoid and palatine in L. borneensis (MCZ 8305). Anterior toward left. (C) SEM micrograph showing ventrolingual view of left pterygoid tooth bases in L. borneensis (MCZ 8305). Anterior toward left. (D) SEM micrograph showing ventrolabial view of right pterygoid in L. borneensis (FMNH 134711), depicting empty tooth row with "sockets" formed by interdental ridges. Anterior toward left. Scale bar equals 1 mm in A-B, 0.1 mm in C, 1 mm in D. 50 FIELDIANA: ZOOLOGY Fig. 18. (A) Transverse section of right palatine of Lanthanotus bomeensis (FMNH 151714), seen in posterior aspect, showing developing replacement tooth medial to functional tooth. (B, C) Transverse section of right pterygoid of L. bomeensis (FMNH 151714), seen in posterior aspect, showing detail of tooth attachment and developing plicidentine at tooth base. Medial to left in all. Scale bar equals 0.1 mm in all. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 51 Fig. 19. (A) CT scan showing ventral view of the skull in Cylindrophis ruffus (FMNH 60958). (B) SEM micrograph depicting ventrolabial view of right pterygoid teeth in C. ruffus (FMNH 179033). Anterior to left. (C) Photograph depicting labial view of right palatine teeth in C. ruffus (FMNH 179033). Anterior to left. Scale bar equals 1 mm in all. 52 FIELDIANA: ZOOLOGY Fig. 20. (A) Transverse section of right palatine of Cylindrophis ruffus (FMNH 131778), seen in posterior aspect. (B) Transverse section of right palatine of C. ruffus (FMNH 131778), seen in posterior aspect, showing recumbent replacement teeth on labial side of affixed tooth. (C) Transverse section of right pterygoid of C. ruffus (FMNH 131778), seen in posterior aspect, showing recumbent replacement teeth on labial side of affixed tooth. Medial to left in all. Scale bar equals 0.1 mm in all. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 53 Fig. 21. (A) CT scan showing ventral view of the skull of Anilius scytale (USNM 204078). (B) SEM micrograph depicting ventrolabial view of the right palatine tooth row of A. scytale (FMNH 35688). Anterior toward left. (C) SEM micrograph depicting lingual view of a right palatine tooth in A. scytale (FMNH 35683), showing tooth base and attachment tissues. Anterior to right. Scale bar equals 1 mm in A-B. 0.1 mm in C. 54 FIELDIANA: ZOOLOGY Fig. 22. (A, B) Transverse section of right pterygoid of Anilius scytale (FMNH 35687), seen in posterior aspect, showing a replacement tooth developing labial to a functional tooth. Medial to left in both. Scale bar equals 0.1 mm in both. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 55 Fig. 23. (A) CT scan showing ventral view of the skull in Xenopeltis unicolor (FMNH 148900). (B) SEM micrograph showing labial view of left pterygoid teeth of X. unicolor (FMNH 178975). Anterior to right. (C) Photograph depicting labial view of right pterygoid teeth of X. unicolor (FMNH 178975), showing recumbent replacement teeth. Anterior to left. Scale bar equals 1 mm in A B. 0.1 mm in C. 56 FIELDIANA: ZOOLOGY 4 ©'.. Fig. 24. (A) Transverse section of left palatine of Xenopeltis unicolor (FMNH 246193), seen in posterior aspect. (B, C) Transverse section of left pterygoid of X. unicolor (FMNH 246193), seen in posterior aspect, showing ligamentous attachment of pterygoid tooth. Medial to right in all. Scale bar equals 0.1 mm in all. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 57 Fig. 25. (A) CT scan showing ventral view of the skull of Boa constrictor (FMNH 31 182). (B) Labial view of right pterygoid teeth in B. constrictor (FMNH 22438), showing replacement teeth. Anterior to left. (C) Photograph depicting labial view of right pterygoid tooth row in B. constrictor (FMNH 22438), showing replacement teeth. Anterior to left. Scale bar equals 1 cm in A, 1 mm in B-C. 58 FIELDIANA: ZOOLOGY Fig. 26. (A) CT scan showing ventral view of the skull in Coluber constrictor (FMNH 135284). (B) SEM micrograph showing ventrolabial view of right palatine teeth in C. constrictor (FMNH 22347), demonstrating carinae and labial replacement. Anterior toward left. (C) SEM micrograph showing ventrolabial view of right palatine tooth row in C. constrictor (FMNH 22347). Anterior toward left. (D) SEM micrograph showing ventrolabial view of right pterygoid tooth row in C. constrictor (FMNH 22347), depicting recumbent replacement teeth within dental lamina at base of tooth row. Anterior toward left. Scale bar equals 1 mm in all. Fig. 27. Transverse section of right pterygoid of C. constrictor (personal collection of Carl Gans), seen in posterior aspect, showing affixed tooth and recumbent replacement teeth. Medial to left. Scale bar equals 0.1 mm. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 59 Fig. 28. (A) CT scan showing ventral view of the skull in Micrurus fulvius (FMNH 39479). (B) SEM micrograph showing ventrolabial view of right palatine tooth row of M. nigrocinctus (FMNH 31109), demonstrating recumbent replacement teeth. Anterior toward left. (C) SEM micrograph showing ventrolingual view of left palatine teeth of M. nigrocinctus (FMNH 31 101), depicting mesiolingual grooves. Anterior toward left. Scale bar equals 1 mm in A-B, 0.1 mm in C. Fig. 29. (A) Transverse section of left pterygoid of Micrurus nigrocinctus (FMNH 31 104), seen in posterior aspect; note mesiolingual groove evident in recumbent replacement tooth. (B) Cross section of left palatine of M. nigrocinctus (FMNH 31 104), seen in posterior aspect, showing tooth undergoing ankylosis. Medial to right in both. Scale bar equals 0.1 mm in both. 60 FIELDIANA: ZOOLOGY Fig. 30. (A) CT scan showing ventral view of the skull in Agkistrodon contortrix (FMNH 166644). (B) SEM micrograph showing labial view of left palatine and pterygoid tooth rows in A. contortrix (FMNH 98623). Anterior toward right. (C) SEM micrograph showing ventrolabial view of left palatine tooth row in A. contortrix (FMNH 98623). Anterior toward right. Scale bar equals 1 mm in all. Fig. 31. (A) Transverse section of left palatine tooth of Agkistrodon contortrix (FMNH 62059), seen in posterior aspect, showing replacement teeth in dental lamina on labial side of tooth. (B) Transverse section of left palatine tooth of A. contortrix (FMNH 62059), seen in posterior aspect, showing attachment. Medial to right in both. Scale bar equals 0.1 mm in both. MAHLER AND KEARNEY: PALATAL DENTITION IN SQUAMATE REPTILES 61 Field Museum of Natural History 1400 South Lake Shore Drive Chicago, Illinois 60605-2496 Telephone: (312) 665-7055