Undetermined undetermined

O’Gorman, José Patricio & Otero, Rodrigo A., 2023, Revision of the short-necked Cretaceous plesiosaurians from New Zealand, Comptes Rendus Palevol 22 (6), pp. 77-90 : 82

Elasmosauridae indet.

( Fig. 3 A-D)

Polycotylidae indet. – Welles & Gregg 1971: 46.

MATERIAL. — CM Zfr 99 , proximal part of a very large propodial .

LOCALITY AND HORIZON. — Waipara River , South Island, New Zealand. Conway Formation, Maastrichtian ( Wilson et al. 2005; Fig. 1).

REMARKS

The presence of a distinctively prominent articular head and a dorsally elevated tuberosity is a feature commonly found in Weddellian elasmosaurids ( Wiffen & Moisley 1986: figs 58, 59; O’Gorman et al. 2015, 2019; Otero et al. 2015). Furthermore, the presence of a tuberosity displaced with respect to the shaft axis of the femur is a feature observed in the femora of several very large Weddellian elasmosaurids such as DM R1529 (holotype of Mauisaurus haasti ( Hector, 1874) , curently cosidered nomen dubium, Hiller et al. 2017) from New Zealand, cf. Aristonectes Cabrera, 1941 (MLP-89-III-3-1) from Antarctica ( O’Gorman et al. 2019), an isolated femur (SGO.PV.135) reffered to Aristonectes quiriquinensis Otero, Soto-Acuña, O’Keefe, O’Gorman, Stinnesbeck, Suárez, Rubilar-Rogers, Salazar & Quinzio, 2014 from Chile (Otero et al. 215: fig. 2) and in the holotype of Kaiwhekea katiki Cruickshank & Fordyce, 2002 ( Cruickshank & Fordyce 2002). The oval articular head/capitulum seen in CM Zfr 99 is probably consequence of taphonomic deformation. The tuberosity is partially eroded. As additional indirect evidence, the very large size of CM Zfr 99 is only comparable to the propodials of MLP-89-III-3-1, a giant elasmosaurid from the Maastrichtian of Antarctica, referred as cf. Aristonectes ( O’Gorman et al. 2019) . Thus, the presence of very large individuals such as CM Zfr 99 is so far documented among elasmosaurids of the Weddellian Province, but locally, CM Zfr 99 represents a novelty in terms of size among Late Cretaceous elasmosaurids from the Conway Formation.