Odonterpeton triangulare, MOODIE, 1909

Mann, Arjan, Pardo, Jason D & Sues, Hans-Dieter, 2023, Osteology and phylogenetic position of the diminutive ‘ microsaur’ Odonterpeton triangulare from the Pennsylvanian of Linton, Ohio, and major features of recumbirostran phylogeny, Zoological Journal of the Linnean Society 197 (3), pp. 641-655 : 643

ODONTERPETON TRIANGULARE MOODIE, 1909

Holotype: USNM PAL 4465 + 4467, part and counterpart cannel coal blocks containing the anterior portion of a skeleton exposed in dorsal view ( USNM PAL 4465) and ventral view ( USNM PAL 4467) ( Figs 1 , 2 ).

Type locality and horizon: Abandoned coal mine operated originally by the Ohio Diamond Coal Company at Linton, Saline Township, Jefferson County, OH, USA (for details, see Hook & Baird, 1986). Local cannel coal is immediately below the Upper Freeport coal of the Allegheny Group. This horizon is dated as Middle Pennsylvanian (Moscovian).

ReƲised diagnosis: Diminutive recumbirostran with the following distinctive combination of characters: 19 maxillary tooth positions; posterior maxillary teeth enlarged; lateral surface of maxilla bearing series of pits; undulating midline sutures between frontals and parietals; nasals small; short forelimbs; and autopodium with three digits and phalangeal count of 2-4-3. Shares the field of palatal teeth with pantylids and gymnarthrids. Shares with Joermungandr Mann et al., 2021 and brachystelechids large parietals. Shares with Joermungandr and at least Diabloroter Mann & Maddin, 2019 among brachystelechids the anterior position of the pineal foramen. Shares with Joermungandr oval, ornamented dermal scales, a short snout and the presence of a single splenial. Differs from Joermungandr in the absence of an anteriorly restricted tooth row, the greater number of teeth in the upper and lower dental arcade, the presence of a tabular, proportionally shorter nasals and the presence of a well-ossified forelimb and pectoral girdle.

Figures

Figure 1. Photographs of the part (USNM PAL 4465) and counterpart (USNM PAL 4467) of the holotype of Odonterpeton triangulare. A, C, skeleton exposed in dorsal view (A) and ventral view (C). B, D, resin casts of the skeleton exposed in dorsal view (B) and ventral view (D).

Figure 2. Line drawings based on the resin casts of the holotype of Odonterpeton triangulare exposed in dorsal view (A; USNM PAL 4465) and ventral view (B; USNM PAL 4467). See Material and Methods for anatomical abbreviations.