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. 2017 Jan;230(1):47-65.
doi: 10.1111/joa.12534. Epub 2016 Aug 19.

The palatal dentition of tetrapods and its functional significance

Ryoko Matsumoto  1 , Susan E Evans  2
Affiliations

The palatal dentition of tetrapods and its functional significance

Ryoko Matsumoto et al. J Anat. 2017 Jan.

Abstract

The presence of a palatal dentition is generally considered to be the primitive condition in amniotes, with each major lineage showing a tendency toward reduction. This study highlights the variation in palatal tooth arrangements and reveals clear trends within the evolutionary history of tetrapods. Major changes occurred in the transition between early tetrapods and amphibians on the one hand, and stem amniotes on the other. These changes reflect the function of the palatal dentition, which can play an important role in holding and manipulating food during feeding. Differences in the arrangement of palatal teeth, and in their pattern of loss, likely reflect differences in feeding strategy but also changes in the arrangement of cranial soft tissues, as the palatal dentition works best with a well-developed mobile tongue. It is difficult to explain the loss of palatal teeth in terms of any single factor, but palatal tooth patterns have the potential to provide new information on diet and feeding strategy in extinct taxa.

Keywords: amniota; cranial soft anatomy; evolution; feeding behavior; function; palatal dentition; tetrapoda.

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Figures

Figure 1
Figure 1
Phylogenetic tree for early tetrapods and amphibians showing arrangement of palatal dentition. Color coding of the palatal figures is consistent in all figures (tree modified from Ruta & Coates, 2007). Palatal figures as follows: 1, Eusthenopteron; 2, Acanthostega; 3, Pederpes; 4, Crassigyrinus; 5, Greerepeton; 6, Edops; 7, Balanerpeton (original image reflected); 8, Phonerpeton; 9, Doleserpeton; 10, Dermophis mexicanus, Gymnophiona; 11, Stereochilus marginatum, Caudata; 12, Gastrotheca walker, Anura; 13, Silvanerpeton; 14, Proterogyrinus; 15, Seymouria; 16, Odonterpeton; 17, Rhynchonkos; 18, Cardiocephalus (original image reflected); 19, Pantylus; 20, Brachydectes; 21, Batrachiderpeton; 22, Ptyonius; 23, Diadectes. Image sources: 1, 2, 4, Clack, 2012; 3, Clack & Finney, 2005; 5, Smithson, 1982; 6, Romer & Witter, 1942; 7, Holmes, 2000; 8, Dilkes, 1990; 9, Sigurdsen & Bolt, 2010; 10–12, Duellman & Trueb, 1994; 13, Ruta & Clack, 2006; 14, Holmes, 1984; 15, Klembara et al. 2005; 16–22, Carroll et al. 1998; 23, Reisz & Sues, 2000; 1, 10–13, 20 original without scale. Abbreviations: ANTH, Anthracosauria; LISS, Lissamphibia; SEY, Seymouriamorpha.
Figure 2
Figure 2
Photographs of the palatal tooth arrangement in various linages: (A) Andrias japonicas (Lisamphibia; NSM‐PO‐H‐447); (B) Dimetrodon limbatus (Synapsida; AMNH FR 4001); (C) Ikechosaurus sunailinae (Choristodera, Diapsida; IVPP V9611‐3), gray‐colored area marks nasopalatal trough, and blue‐colored area marks the distribution of the palatal dentition. Institutional abbreviations: American Museum Natural History (AMNH); IVPP Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China (IVPP); National Museum of Nature and Science, Tokyo (NSM). Anatomical abbreviations: d, dentary; ept, ectopterygoid; hy, hyoid; pal, palatine; psh, parasphenoid; pt, pterygoid; pt fl, pterygoid flange; v, vomer.
Figure 3
Figure 3
Skulls of synapsids in palatal view (phylogeny based on Sidor, 2001): 1 Cotylorhynchus; 2, Ennatosaurus; 3, Mesenosaurus; 4, Varanosaurus; 5, Edaphosaurus; 6, Haptodus; 7, Secodontosaurus; 8, Tetraceratops; 9, Biarmosuchus; 10, Lycaenodon; 11, Herpetoskylax; 12, Titanophoneus; 13, Syodon; 14, Styracocephalus (original without scale); 15, Estemmenosuchus; 16, Struthiocephalus. Image sources: 1, Reisz & Sues, 2000; 2, Maddin et al. 2008; 3, Reisz & Berman, 2001; 4, Berman et al. 1995; 5, Modesto, 1995; 6, Laurin, 1993; 7, Reisz et al. 1992; 8, Laurin & Reisz, 1996; 9; Ivakhnenko, 1999; 10–11; Sigogneau‐Russell, 1989; 12–13, 15, King, 1988; 14; Rubidge & Heever, 1997; 16, Rubidge, 1991. Abbreviations: BIAR, Biarmosuchia; CASE, Caseasauria; DINO, Dinocephalia; OPHI, Ophiacodontidae; SPHE, Sphenacodontidae; VARA, Varanopidae.
Figure 4
Figure 4
Skulls of synapsids in palatal view (phylogeny based on Sidor, 2001), continued from Fig. 3: 1, Aelurosaurus; 2, Arctognathus; 3, Leontocephalus; 4, Scylacops; 5, Aloposaurus; 6, Gorgonops; 7, Arctops; 8, Prorubidgea; 9, Dinogorgon; 10, Rubidgea (original without scale); 11, Theriognathus; 12 Viatkosuchus (original without scale); 13 Regisaurus. Image sources: 1–10, Sigogneau‐Russell, 1989; 11, 13, Kemp, 1982; 12, Tatarinov, 1995.
Figure 5
Figure 5
Skulls of parareptiles in palatal view (phylogeny based on Tsuji et al. 2012). 1, Mesosaurus; 2, Millerosaurus; 3, Acleistorhinus; 4, Nyctiphruretus; 5, Procolophon (original without scale); 6, Owenetta; 7, Scutosaurus; 8, Pareiasuchus; 9, Macroleter; 10, Nycteroleter; 11, Bashkyroleter mesensis. Image sources: 1, Modesto, 2006; 2, 4,7, Carroll, 1988; 3, DeBraga & Reisz, 1996; 5, Carroll & Lindsay, 1985; 6, Reisz & Scott, 2002; 8, Lee et al. 1997; 9, Tsuji, 2006; 10, Tverdokhlebova & Ivakhnenko, 1984; 11, Ivakhnenko, 1997. Abbreviations: LANT, Lanthanosuchidae; BOL, Bolosauridae; PROCOL, Procolophonoidea; PAREIA, Pareiasauria.
Figure 6
Figure 6
Skulls of Eureptilia and Diapsida, Sauropterygia, Ichthyopterygia and Lepidosauromorpha in palatal view (phylogeny based on DeBraga & Rieppel, 1997; Rieppel & Reisz, 1999; Wiens et al. 2010; Pyron et al., 2013) 1, Captorhinus; 2, Paleothyris; 3, Petrolacosaurus; 4, Araeoscelis; 5, Claudiosaurus; 6, Youngina; 7, Placodus; 8, Kuehneosaurus; 9, Marmoretta; 10, Gephyrosaurus; 11, Clevosaurus; 12, Sphenodon; 13, Lacerta; 14, Ctenosaura (original without scale); 15, Ophisaurus; 16, Heloderma; 17, Shinisaurus; 18, Platecarpus (original without scale); 19, Anilius. Image sources: 1, Reisz & Sues, 2000; 2; Benton, 2000; 3; Reisz, 1981; 4; Vaughn, 1955; 5–7, Carroll, 1988; 8; Robinson, 1962; 9; Evans, 1991; 10–11, Jones, 2006; 12,18; Romer, 1956; 13–17, Evans, 2008; 19; Cundall & Irish, 2008. Abbreviation: Rhyncho, Rhynchocephalia.
Figure 7
Figure 7
Skulls of Archosauromorph in palatal view (phylogeny based on Brusatte et al. 2010; Borsuk‐Białynicka & Evans, 2009a; Dilkes & Sues, 2009): 1, Czatkowiella; 2, Cteniogenys; 3, Proganochelys; 4, Mesosuchus; 5, Tanystropheus; 6, Proterosuchus; 7, Osmolskina; 8, Euparkeria; 9, Doswellia; 10, Proterochampsa. Image sources: 1, Borsuk–Białynicka & Evans, 2009a; 2, Evans, 1990; 3,6, Carroll, 1988; 4; Dilkes, 1998; 5; Wild, 1987; 7, Borsuk‐Białynicka & Evans, 2009b; 8; Ewer, 1965; 9; Weems, 1980; 10, Sill, 1967.
Figure 8
Figure 8
Summary of evolutionary patterns in the palatal dentition of tetrapods.
Figure 9
Figure 9
Summary of evolutionary history of soft tissues related to feeding through tetrapod evolution (see text for detail and references).
Figure 10
Figure 10
Keratinized oral epithelium in extant taxa: A, Anas platyrhynchos [Mallard; KPM‐NF 2002622, floor of mouth (left) and palate (right)]; B, Spheniscus demersus (African Penguin; KPM‐NF 2002403), dissection photographs and CT image of a sagittal section; C, Osteolaemus tetraspis (Dwarf Crocodile; Ueno Zoo, Tokyo Japan, no number), palatal surface; D, Chelonia agassizii (Galápagos Green Turtle; KPM‐NFR 389), palatal surface with keratinized keels and serrations. Institutional abbreviation: Kanegawa Prefectural Museum of Natural History (KPM‐NF).
See this image and copyright information in PMC

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