Bottosaurus fustidens, Cossette, 2021

Cossette, Adam P., 2021, A new species of Bottosaurus (Alligatoroidea: Caimaninae) from the Black Peaks Formation (Palaeocene) of Texas indicates an early radiation of North American caimanines, Zoological Journal of the Linnean Society 191 : -

BOTTOSAURUS FUSTIDENS SP. NOV.

l s i d: u r n: l s i d: z o o b a n k. o r g: a c t: 9 F 6 E B 6 0 1 - 1913-4421-9562-1652A376A89A

H o l o t y p e: T M M 4 0 1 4 8 - 7, i n c o m p l e t e s k u l l, including the right posterior dorsal process of the premaxilla, mostly complete nasals, frontal, prefrontals, mostly complete postorbitals, anterior parietal, mostly complete squamosals, partial jugals, incomplete quadratojugals, an incomplete left quadrate, portions of the right and left exoccipitals, partial ectopterygoids and dorsal portions of the pterygoids. Nearly complete lower jaws are preserved. The right dentary is more complete than the left. Both splenials are preserved, and the right side is nearly complete. The anterior left angular and the posterior right angular are preserved; the right posterior surangular is present, and most of the left articular is preserved. Postcranial elements are preserved. Four cervical vertebrae, six dorsal vertebrae, six caudal vertebrae and four indeterminate vertebral fragments are preserved; all vertebrae are incomplete. Portions of dorsal ribs are poorly preserved. The left humerus is incomplete. The proximal right ischium is preserved. The left femur is complete. Numerous elements of the hand and foot are preserved ( Figs 4–6).

Referred specimens: TMM 41366-16, mostly complete upper jaw, fragment of lower jaw, and partial elements of the posterior skull ( Fig. 7).

Occurrence: Black Peaks Formation, Brewster County, TX, USA ( Fig. 8); Palaeocene, Tiffanian North American Land Mammal Age.

Etymology: From Latin fustis, club, and dens, tooth, to describe the robustly built, club-like mid-jaw and posterior teeth of the species.

Diagnosis: Bottosaurus fustidens shares features with Bottosaurus harlani but is differentiated by skull, mandibular and postcranial character states. A U-shaped depression similar to, but considerably shallower than that of B. harlani , is present on the frontal at the point of the greatest mediolateral constriction between the orbits ( Fig. 3). Unlike B. harlani , the splenial of B. fustidens does not contact the mandibular symphysis, but is separated by a distance of two alveoli; its anteriormost projection passes ventral to the Meckelian groove ( Fig. 9). The mandibular tooth row posterior to the fifth alveolus is linear, in opposition to B. harlani . Dorsal vertebrae bear an anteroposteriorly oriented indentation along the ventral side of the vertebral body ( Fig. 10).

Description: Morphology is described from two specimens, the holotype individual (TMM 40148-7) and a smaller referred individual (TMM 41366-16) from the same locality and horizon. Preservation of TMM 40148-7 is better than that of TMM 41366-16; the former is more complete and has clearer sutural contacts.