Anura, Gardner & Redman & Cifelli, 2016

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 : 93-95

Anura indeterminate morph 3

( Text-fig. 10 )

M a t e r i a l a n d o c c u r r e n c e s: Maxillae from Dinosaur Park Formation and Oldman Formation, Alberta, Canada; maxillae from Judith River Formation, Montana, USA; maxillae from Kaiparowits Formation, Utah, USA (Appendix 2).

D e s c r i p t i o n: An assortment of fragmentary, toothed maxillae from various localities are notable for having labial surfaces that range from smooth to weakly ornamented. As shown by the six examples depicted in Text-fig. 10 , these specimens preserve various portions of the maxilla and represent a size range of individuals.

AMNH FARB 8462 ( Text-fig. 10a, b ) is the anterior portion of a moderate-sized, left maxilla that is broken posteriorly in front of the processus palatinus and is missing the dorsal part of the lamina anterior. Despite being incomplete, the preorbital region clearly was at least moderately tall and the anterior edge of its lamina anterior is bluntly rounded in lingual or labial outline, without any indication of a distinct, anteriorly-directed rostellum (cf. Text-figs 5g, h and 8a, b ). The preserved portion of the lamina horizontalis, which probably lies below where the processus palatinus would have been located, is a shallow and lingually expanded shelf. In contrast to the dorsal curvature typical for maxillae of our unnamed genus and species II (cf. Text-fig. 7 ), the lingual margin of the lamina horizontalis in AMNH FARB 8462 curls ventrally. The preserved tooth bases demonstrate that the teeth were relatively large and moderately spaced. In contrast to the other five figured examples, the labial surface of FARB AMNH FARB 8462 is smooth. The distinctiveness of this specimen was recognized over 40 years ago, when Sahni (1972b: 347 and fig. 7N, O) erected it as the exemplar for his “Discoglossid B”, which he characterized as “large frog with smooth maxilla”.

A second maxilla, AMNH FARB 33040 ( Text-fig. 10c, d ) from the same locality (Clambank Hollow, Judith River Formation), exhibits a more roughened labial texture. This right maxilla is from a larger individual and it is more robustly built. It preserves the area bearing the processus pterygoideus and adjacent portions of the bone. Despite the fragmentary nature of this specimen, it is evident that the margo orbitalis (anteriorly incomplete) is deeply concave, the processus zygomatico-maxillaris (broken posteriorly) is considerably higher than the suborbital region (i.e., preserved height of process at least twice the vertical depth of the bone below the lowest point along the margo orbitalis), the processus pterygoideus (broken lingually) is prominent and projected lingually, the lamina horizontalis is relatively deep, moderately wide lingually, and has a shallowly convex lingual face, and the tooth row (broken posteriorly) extended posteriorly well past the level of the processus pterygoideus.

Examples of micro pitted labial texture are seen in two fragmentary, left maxillae from different localities: TMP 1987.029.0085 ( Text-fig. 10e, f ), from Dinosaur Provincial Park (Oldman Formation), preserves the portion bearing the processus palatinus and is from a moderate-sized individual, whereas AMNH FARB 33046 ( Text-fig. 10g, h ), from Clambank Hollow (Judith River Formation), is from a much larger individual and preserves the region bearing the broken base of a large processus pterygoideus. The labial surface in both specimens has a roughened texture similar to the above-described AMNH FARB 33040, but additionally is perforated by tiny pits and a few narrow, short, and shallow grooves. Pits are sparsely scattered and mostly limited to the more dorsal portion of TMP 1987.029.0085, but are more densely packed and broadly distributed across the pars facialis portion on AMNH FARB 33046 (cf. Text-fig. 10e versus g). In neither specimen are the pits enclosed by distinct ridges; instead, they are perforations in the surface of the bone.

Several specimens emphasize small grooves or striations over pits. Examples include the anterior end of a left maxilla ( UALVP 40218 : Text-fig. 10i, j ) from the Dinosaur Park Formation and two previously reported, fragmentary maxillae from the Kaiparowits Formation, one preserving a similar portion of the bone and one preserving the portion bearing the processus pterygoideus (see Roček et al. 2010: fig. 15Ao and n, respectively). These three specimens are from smaller-sized individuals. In each, the labial surface is indented by shallow, narrow grooves or striations of varying lengths typically arranged subparallel to one another. As with the micro pitted maxillae, the grooves are not bordered by raised ridges .

The final labial pattern is exhibited by AMNH FARB 33041 ( Text-fig. 10k ). This is a moderate-sized, right maxilla from Clambank Hollow (Judith River Formation) that preserves the portion bearing the processus palatinus. Its labial surface is shallowly indented by polygonal divots that are closely spaced, moderate in width, and have shallowly concave bottoms. As with the micro pitted and grooved examples reported above, these divots are simply indentations in the labial surface and are not bordered by raised ridges.

R e m a r k s: Maxillae assigned to our morph 3 are broadly similar only in bearing teeth and in having labial surfaces that range from smooth to weakly ornamented. Differences in their labial surfaces, combined with absolute sizes and details of lingual structures (especially the form of the lamina horizontalis) suggest that multiple species are represented. That possibility is difficult to substantiate, because the available specimens are few in number and fragmentary. Overlap in preserved portions among certain specimens is helpful for showing that differences in the labial surfaces do not necessarily reflect regional differences along the bone. In the two maxillae preserving the anterior portion, the labial surface is smooth in AMNH FARB 8462 versus indented by striations on UALVP 40218 (cf. Text-fig. 10a versus i); in the two maxillae preserving the portion bearing the processus palatinus, the labial surface is perforated with tiny pits in AMNH FARB 33040 versus indented by shallow polygonal divots in AMNH FARB 33041 (cf. Text-fig. 10e versus k); and in the two maxillae preserving the portion bearing the processus pterygoideus, the labial surface is roughened in AMNH FARB 33041 versus perforated with tiny pits in AMNH FARB 33046 (cf. Text-fig. 10c versus g). Based solely on similarities in their labial surfaces, certain of the specimens potentially could be from the same taxon. Specifically, the pair of micro pitted maxillae (TMP 1987.029.0085 from the Oldman Formation of Alberta and AMNH FARB 33046 from the Judith River Formation of Montana) might be from different-sized conspecifics, whereas maxillae indented with striations from the Dinosaur Park Formation of Alberta (UALVP 40218) and the two previously figured maxillae ( Roček et al. 2010: fig. 15An, o) from the Kaiparowits Formation of Utah might be from similarly-sized conspecifics. Alternatively, those resemblances might simply be convergences.

None of the morph 3 specimens resemble other Judithian maxillae that we assign to species or to the other two morphs recognized in our review. Some of those differences are obvious: the presence of teeth differentiates morph 3 maxillae from the edentulous species Tyrrellbatrachus brinkmani and Theatonius n. sp., whereas the unornamented to weakly ornamented labial surfaces of morph 3 maxillae differentiate them from the strongly ornamented maxillae of Scotiophryne pustulosa , Hensonbatrachus kermiti , our unnamed genus and species I, morph 1 maxillae, and one (UALVP 40191) of our morph 2 maxillae. As for the remainder, differences in absolute size and the curvature of the lingual edge of the lamina horizontalis serve to differentiate the toothed and smooth maxillae of our unnamed genus and species II (smaller size and lingual edge of lamina horizontalis curved dorsally) from AMNH FARB 8462 (larger size and lingual edge of lamina horizontalis curved ventrally). Although AMNH FARB 33041 and the second (UALVP 40192) of our morph 2 maxillae are similar in bearing teeth and having shallow polygonal depressions, differences in absolute size and relative depth of the suborbital region (AMNH FARB 33041 is bigger and has deeper suborbital region) seem to argue against those being from the same species. Looking outside the Judithian, some of the maxillae assigned to our morph 3 are reminiscent of indeterminate, toothed anuran maxillae with smooth, roughened, pitted, or striated labial surfaces reported from older and younger Cretaceous deposits in the Western Interior (e.g., Gardner 2008, Roček et al. 2010).

Figures

Text-fig. 10. Maxillae of Anura indeterminate morph 3 from the middle – late Campanian (Judithian) of Alberta, Canada and Montana, 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, b – incomplete left maxilla, AMNH FARB 8462, example of maxilla with smooth labial surface, in labial (a) and lingual (b) views, from Judith River Formation, Clambank Hollow, Montana. c, d – incomplete right maxilla,AMNH FARB 33040, example of maxilla with slightly roughened labial surface, in labial (c) and lingual (d) views, from Judith River Formation, Clambank Hollow, Montana. e, f – incomplete left maxilla, TMP 1987.029.0085, example of maxilla with tiny, scattered pits and some narrow, short grooves across labial surface, in labial (e) and lingual (f) views, from Oldman Formation, TMP locality L0409, Dinosaur Provincial Park, Alberta. g, h – incomplete left maxilla, AMNH FARB 33046, example of maxilla with more dense arrangement of tiny pits across labial surface, in labial (g) and lingual (h) views, from Judith River Formation, Clambank Hollow, Montana. i, j – incomplete left maxilla, UALVP 40218, example of maxilla with narrow, shallow grooves across labial surface, in labial (i) and lingual (j) views, from Dinosaur Park Formation, Irvine locality, Alberta. k – incomplete right maxilla, AMNH FARB 33041, example of maxilla with shallow, somewhat polygonal divots across labial surface, in labial view, from Judith River Formation, Clambank Hollow, Montana.

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.

Text-fig. 8. Maxillae and squamosal of Anura indeterminate morph 1 from the middle – late Campanian (Judithian) ofAlberta, Canada and Montana, Utah, and Texas, 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, b – incomplete right maxilla, UALVP 40169, in labial (a) and lingual (b) views, from Dinosaur Park Formation, Irvine locality, Alberta. c, d – incomplete left maxilla, AMNH FARB 8461, in labial (c) and lingual (d) views, from Judith River Formation, Clambank Hollow, Montana. e, f – incomplete right maxilla, OMNH 23837, in labial (e) and lingual (f) views, from Kaiparowits Formation, OMNH locality V5, Utah. g, h – incomplete left maxilla, OMNH 67094, in labial (g) and lingual (h) views, from Kaiparowits Formation, OMNH locality V6, Utah. i, j – fragmentary?left maxilla, TMM 43057-256, in labial (i) and lingual (j) views, from Aguja Formation, OMNH locality V58/TMM locality 43057, Texas. k, l – fragmentary left maxilla, OMNH 25243, in labial (k) and lingual (l) views, from Aguja Formation, OMNH locality V58/TMM locality 43057, Texas. m, n – incomplete left squamosal, OMNH 23538, in lateral (m) and medial (n) views, from Kaiparowits Formation, OMNH locality V6, Utah.

Text-fig. 7. Maxillae ofAnura unnamed genus and species II from the middle – late Campanian (Judithian) of Utah, USA. All specimens are from OMNH locality V6 in the Kaiparowits Formation. Except where noted otherwise, 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–d – incomplete right maxilla, OMNH 67095, in labial (a, b) and lingual (c, d) views (images in b and d are scanning electron micrographs). e, f – incomplete left maxilla, OMNH 67098, in labial (e) and lingual (f) views. g–i – incomplete left maxilla, OMNH 67100, in labial (g) and lingual (h) views and, with anterior to right, in dorsal (i) view. j–l – incomplete right maxilla, OMNH 67099, in labial (j) and lingual (k) views and, with anterior to left, in dorsal (l) view. m–o – incomplete right maxilla, OMNH 67096, entire specimen in labial (m) and lingual (n) views and close up (o) of intact tooth in oblique lingual-anterior-ventral view (images in n and o are scanning electron micrographs).