Plesiosauria indet

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 : 84

Plesiosauria indet .

( Fig. 4 F-G)

Pliosauridae gen. et sp. indet . – Wiffen & Moisley 1986: 243.

MATERIAL. — NPC CD 457 : an isolated, incomplete adult plesiosaurian pubis .

LOCALITY AND HORIZON. — Mangahouanga Stream , a northern tributary of Te Hoe River , inland Hawke’s Bay, North Island, New Zealand. Maungataniwha Sandstone Member of the Tahora Formation. Upper Campanian-lower Maastrichtian ( Vajda & Raine 2010; Fig. 1).

REMARKS

This specimen was interpreted as a coracoid by Wiffen & Moisley 1986. These authors considered the symphysis as the posterior extension of a coracoid. Under that interpretation, the specimen indeed resembled a “pliosaurid or polycotylid” coracoid. However, the bone is much eroded. The side opposed to the symphysis (i.e., the external side) shows rough edges, indicating that the bone is broken. This is visible in the “two lateral prominences”, which are an artifact of the medial erosion of the tabular bone. In lateral view, the specimen lacks a transverse thickening typically present in plesiosaurian coracoids. The presence of a short medial anterior process in such a large (likely adult) specimen suggests the lack of a girdle bar (in this reinterpretation, a pelvic bar). In addition, typical features present in polycotylid coracoids, such as the perforations on the symphyseal margin ( Sato 2005; Albright et al. 2007; Schmeisser-McKean et al. 2012), although absent in Plesiopleurodon wellesi Carpenter, 1996 and Mauriciosaurus fernandezi Frey, Mulder, Stinnesbeck, Rivera-Sylva, Padilla-Gutiérrez & González-González, 2017 ( Frey et al. 2017; Fischer et al. 2018), are not present. Therefore, the specimen CD 457 is considered a plesiosaur pubis. The large size and the lack of a pelvic bar suggest affinities to Elasmosauridae , but this cannot be assured. However, it is possible to discard CD 457 as the coracoid of a “pliosaur” sensu lato, or else, of a polycotylid.