Tyrrellbatrachus brinkmani GARDNER, 2015

Gardner, James D., Redman, Cory M. & Cifelli, Richard L., 2016, The Hopping Dead: Late Cretaceous Frogs From The Middle - Late Campanian (Judithian) Of Western North America, Fossil Imprint 72 (1 - 2), pp. 78-107 : 85

Tyrrellbatrachus brinkmani GARDNER, 2015

( Text-fig. 5a–f )

M a t e r i a l a n d o c c u r r e n c e s: Seven incomplete maxillae (holotype and six referred) from Dinosaur Park Formation , Alberta, Canada (Appendix 2) .

R e m a r k s: Tyrrellbatrachus brinkmani was established for seven incomplete maxillae, each preserving varying amounts of the posterior portion of the suborbital region and adjacent portion of the postorbital region. Although the complete structure of the maxilla is unknown, the available specimens are distinctive among known North American Cretaceous anuran maxillae and species in exhibiting a unique combination of features (see three examples in Text-fig. 5a–f ), including the moderate size and robustness of the bone, lack of teeth (i.e., edentulous), the margo orbitalis is shallowly concave, the crista dentalis is relatively shallow and its lingual surface is perforated by tiny foramina, the processus pterygoideus is prominently developed and triangular, the processus zygomatico-maxillaris is moderately tall and has a thin, smooth dorsal edge (suggesting no sutural contact with the squamosal), and the labial surface of the maxilla, especially in the suborbital region and in larger specimens, has a roughened texture. The described size series indicates that with growth maxillae lose much of the pitted labial texture seen in smaller maxillae and develop a groove that descends anteroventrally along the labial surface at the junction between the processus zygomatico-maxillaris and suborbital region.

The first examples of Tyrrellbatrachus brinkmani maxillae were collected in the mid-1980s by Donald Brinkman (one of the founding research scientists at the Royal Tyrrell Museum of Palaeontology) from vertebrate microfossil localities in the basal portion of the Dinosaur Park Formation, in the Dinosaur Provincial Park area. All seven reported maxillae are from that same restricted stratigraphic interval and region (Gardner 2015). No examples of maxillary specimens preserving the more anterior portion of the bone or other skull bones that potentially could be associated (e.g., on the basis of similar roughened external texture, complementary features, and provenance) with the described maxillary specimens of T. brinkmani have yet been recognized from localities in the Dinosaur Park Formation.

Tyrrellbatrachus brinkmani maxillae are superficially similar to those of Theatonius (see Text-fig. 5g, h and next account) in being edentulous, but the former differ in being relatively larger, in lacking the distinctive pustulate labial ornament of Theatonius , and in numerous details of the lingual surface and inferred pattern of squamosal contact.

Figures

Text-fig. 5. Edentulous anuran maxillae from the middle – late Campanian (Judithian) of Alberta, Canada and Utah, USA. All images are photographs and depict specimens lightly dusted with ammonium chloride to enhance details and texture. Images at different magnifications; see corresponding scale bars. a–f – Tyrrellbatrachus brinkmani GARDNER, 2015, all from basal part of Dinosaur Park Formation, Dinosaur Provincial Park,Alberta: a, b – incomplete right maxilla, TMP 1985.066.0035 (holotype), in labial (a) and lingual (b) views, from TMP locality L0404; c, d – incomplete right maxilla, TMP 1986.033.0033, in labial (c) and lingual (d) views, from TMP locality L0031; e, f – incomplete left maxilla, TMP 1986.214.0032, in labial (e) and lingual (f) views, from TMP locality L0051. g, h – Theatonius n. sp., nearly complete left maxilla, OMNH 67082, in labial (g) and lingual (h) views, from Kaiparowits Formation, OMNH locality V6, Utah.