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| Gordodon kraineri
Lucas, Rinehart & Celeskey, 2018
DOI: 10.26879/899
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ABSTRACT
Gordodon kraineri is a new genus and species of edaphosaurid eupelycosaur known from an associated skull, lower jaw and incomplete postcranium found in the early Permian Bursum Formation of Otero County, New Mexico, USA. It has a specialized dental apparatus consisting of large, chisel-like incisors in the front of the jaws separated by a long diastema from relatively short rows of peg-like maxillary and dentary cheek teeth. The dorsal vertebrae of Gordodon have long neural spines that bear numerous, randomly arranged, small, thorn-like tubercles. The tubercles on long neural spines place Gordodon in the Edaphosauridae, and the dental apparatus and distinctive tubercles on the neural spines distinguish it from the other edaphosaurid genera—Edaphosaurus, Glaucosaurus, Lupeosaurus and Ianthasaurus. Gordodon is the oldest known tetrapod herbivore with a dentary diastema, extending the temporal range of that anatomical feature back 95 million years from the Late Triassic. The dental apparatus of Gordodon indicates significantly different modes of ingestion and intraoral transport of vegetable matter than took place in Edaphosaurus and thus represents a marked increase in disparity among edaphosaurids. There were two very early pathways to tetrapod herbivory in edaphosaurid evolution, one toward generalized browsing on high-fiber plant items (Edaphosaurus) and the other (Gordodon) toward more specialized browsing, at least some of it likely on higher nutrient, low fiber plant items. Gordodon shows a surprisingly early specialization of the dental apparatus and indicates how incomplete our knowledge is of edaphosaurid evolution, disparity and diversity.
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| FIGURE 2. Holotype skull, lower jaw and incomplete postcranium of Gordodon kraineri, NMMNH P-70796, photograph (1) and bone map (2). Scale equals 10 cm. |
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FIGURE 3. The skull and lower jaw, as preserved, of the holotype of Gordodon kraineri, NMMNH P-70796, in right lateral view, photograph (1) and line drawing (2).
Anatomical abbreviations are: an = angular; ar = articular; d = dentary; ep = epipterygoid; f = frontal; l = lacrimal; m = maxilla; mtp = mandibular tooth plate; n = nasal; p = parietal; pf = postfrontal; pm = premaxilla; pr = prearticular; prf = prefrontal; pt = pterygoid; q = quadrate; qj = quadratojugal; sa = surangular; sm = septomaxilla; spl = splenial; sq = squamosal; st = supratemporal; t = tabular; v = vomer. Scale equals 1 cm.
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SYSTEMATIC PALEONTOLOGY
SYNAPSIDA Osborn, 1903
EUPELYCOSAURIA Kemp, 1982
EDAPHOSAURIDAE Cope, 1882
Gordodon gen. nov.
Etymology. Gordo, Spanish for “fat,” and Greek odon, “tooth,” in reference to the large (“fat”) teeth at the anterior end of the snout of the holotype. Gordo also is a reference to the city of Alamogordo, near the type locality.
Diagnosis. Gordodon is a medium-sized edaphosaur (presacral length ~1 m) distinguished from the other edaphosaurid genera by: an unique dental apparatus consisting of large chisel-like incisors in the premaxilla and dentary (dentary incisors inferred from empty alveolus) separated by a long diastema from a relatively short row of peg-like maxillary and dentary cheek teeth and tooth plates with small (<1 mm) teeth on the interior surface of the mandible; preorbital skull length subequal to postorbital skull length; a relatively short nasal-maxilla suture; cervical and anterior dorsal vertebrae with relatively gracile centra that are double-keeled ventrally; and cervical and dorsal vertebrae have long neural spines that bear up to 12 small, thorn-like lateral tubercles randomly distributed on each side.
Gordodon kraineri sp. nov.
Etymology. To honor Karl Krainer for his many contributions to our knowledge of the late Paleozoic geology and paleontology of New Mexico.
Holotype. NMMNH P-70796, incomplete skeleton consisting of the skull, lower jaws, all or parts of 21 vertebrae (five cervical vertebrae, four complete dorsal vertebrae, the neural spines in varying states of completeness of 12 additional dorsal vertebrae), parts of five cervical and five dorsal rib pairs, parts of the right and left clavicles and scapulae and parts of two digits of the manus(?) (Figure 2).
Holotype locality. NMMNH locality 8967, Otero County, New Mexico, USA (Figure 1).
Stratigraphic horizon and age. Lower part of Bursum Formation, early Wolfcampian (early Permian).
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| Life restoration of Gordodon kraineri. |
Spencer G. Lucas, Larry F. Rinehart and Matthew D. Celeskey. 2018. The Oldest Specialized Tetrapod Herbivore: A New Eupelycosaur from the Permian of New Mexico, USA. Palaeontologia Electronica. 21.3.39A; 1-42. DOI: 10.26879/899
Plain Language Abstract: Gordodon kraineri is a new kind of sail-backed reptile based on an incomplete skeleton found in ~300 million year old rocks in southeastern New Mexico. Gordodon belongs to a family of early herbivorous reptiles, the Edaphosauridae, and has a surprisingly specialized skull and dentition. These skeletal specializations indicate it was a selective browser on plants.
