Champsosaurus lindoei Gao & Fox, 1998

Dudgeon, Thomas W., Mallon, Jordan C. & Evans, David C., 2024, The first report of Champsosaurus lindoei (Choristodera: Champsosauridae) from the Campanian of the United States: anatomical, phylogenetic, and palaeoecological significance, Zoological Journal of the Linnean Society 200 (3), pp. 776-795 : 780

Champsosaurus lindoei Gao & Fox, 1998

Holotype: UALVP 931 , a nearly complete skeleton with skull and mandibles, vertebral series lacking the tail, limb girdles, and limbs.

Type locality and horizon: An outcrop in Dinosaur Provincial Park, in Section 17, Township 20, Range 12, W4, Alberta, Canada, from what is now recognized as the Dinosaur Park Formation (Middle Campanian; ~76.5 to 74.5 Ma; Ramezani et al. 2022).

Diagnosis: A relatively small and gracile Champsosaurus with: (1) snout significantly more slender in proportion to the skull size with a more expanded narial bulla; (2) pterygoid flange weakly developed with reduced number of teeth; (3) inferior temporal arch nearly straight and not swollen laterally; (4) inferior temporal fenestra rectangular ( Gao and Fox 1998).

Locality and horizon of ROM 50000: ROM 50000 was recovered from the locality north of Dupuyer, in either Section 29 or 30, Township 29N, Range 7W, Pondera County, Montana, by private collectors. This locality is in Cession 574, just south of the Blackfeet Nation (Cession 695). It was found in situ in a fine, grey/beige sandstone from the mid-upper TMF (Middle to Upper Campanian; ~82.5 to 74.6 Ma; Ramezani et al. 2022).

Comments: ROM 50000 is referred to C. lindoei based on its relatively small size (maximum skull length = 258 mm), slender snout, straight inferior temporal arch, and rectangular inferior temporal fenestra ( Gao and Fox 1998). The morphology of the pterygoid flange, number of pterygoid teeth, and proportions of the narial bulla cannot be commented on because the ventral surface of the skull is not exposed, and the narial bulla has fractured away post-mortem.