MOSASAURIDAE GERVAIS, 1852

Kiernan, Caitlin R. & Ebersole, Jun A., 2023, Two new plioplatecarpine mosasaurs (Mosasauridae; Plioplatecarpinae) of the genus Ectenosaurus from the Upper Cretaceous of North America, PaleoBios 40 (1894), pp. 1-28 : 4-5

MOSASAURIDAE GERVAIS, 1852

RUSSELLOSAURINA POLCYN AND BELL, 2005 PLIOPLATECARPINAE DOLLO, 1884

Diagnosis (after Konishi and Caldwell 2011)― Russellosaurines generally of medium size, mandible length rarely reaching 100 cm; quadrate ala laterally expanded with uniformly curved border, thin in the center; distinct alar concavity present immediately dorsal to mandibular condyle;surprastapedial process elongate, at least reaching mid-height of quadrate; process often ending with blunt terminus; canal(s) for basilar artery through basisphenoid and basioccipital exiting as large opening(s) on medullary floor; jaws slender; a large foramina on lateroventral/ventral face of retroarticular process; marginal tooth crowns slender, distally tapering and posteromedially recurved from mid-height; middle and posterior tooth crowns typically bicarinate, two carinae aligned in anteroposterior orientation and dividing crown surface semi-equally; marginal tooth crown medially finely striated, laterally faceted or fluted to various extent;tooth crown with sub-circular basal cross-section; intermediate and terminal caudal centra horizontally short, centrum length not exceeding centrum height more than 1.5 times.

Included Genera— Platecarpus Cope (1869) , Plioplatecarpus Dollo (1882) , Goronyosaurus Azzaroli et al. (1972) , Angolasaurus Antunes (1964) , Ectenosaurus Russell (1967) ; Selmasauru s Wright and Shannon (1988), Russellosaurus Polcyn and Bell (2005) , Latoplatecarpus Konishi and Caldwell (2011) , Plesioplatecarpus Konishi and Caldwell (2011) , Gavialimimus Strong et al. (2020) , and Sarabosaurus dahli Polcyn et al. (2023).

ECTENOSAURUS Russell, 1967

Generic Type― Ectenosaurus clidastoides ( Merriam, 1894) .

Generic Holotype ― Formerly at Bayerishe Staatssammlung für Paläontologie ( Munich , Germany), probably destroyed in Second World War , included "posterior portion of the skull and several vertebrae" collected from the Niobrara Chalk of Logan County, Kansas, USA ( Russell 1967:158).

Generic Neotype ― FHSM VP- 401, designated the neotype by Willman et al. (2021), includes an essentially complete, articulated skull with both mandibles, articulated vertebral column to the 29th prepygal, ribs (with fragments of calcified costal cartilage), sternum, both scapulo-coracoids, and the majority of both forelimbs. It should be stressed that portions of the neotype have been heavily restored with plaster. Specimen was collected from the Smoky Hill Member of the Niobrara Chalk (upper Santonian-lower Campanian) at "Garret Ranch, seven or eight miles northwest of Wakeeney, Trego County, Kansas " ( Russell 1967:158, Schumacher 1993).

Generic Diagnosis (modified from Willman at al. 2021)― Plioplatecarpine possessing the following apomorphies: premaxilla-maxilla suture extending posteriorly beyond posterior end of third maxillary tooth; maxillary and dentary tooth count each exceeding 12; prefrontal excluded from posterolateral margin of external nares by wing of maxilla; frontal emarginate above orbits; prefrontal and postorbitofrontal not in contact; parietal table wider than long; posteroventral process on jugal present; anterior border of jugal vertical ramus convex near jugal corner; 9–11 teeth in pterygoid; pterygoid tooth row anterior to ectopterygoid process straight; pterygoid teeth subequal in size; suprastapedial process medially excavated; posterolateral infrastapedial process of quadrate overlapping posteriorly onto distal terminus of surprastapedial process; stapedial pit narrowly rectangular; medial parapet of dentary higher than lateral wall; coronoid dorsal process extending posteriorly over free dorsal border of surangular, terminating acutely in profile; post-glenoid notch on dorsal rim of articular; at least 29 presacral, five pygal, and 28 intermediate caudal vertebrae; hypapophysis laterally compressed; anteroventral ridge extending from hypapophysis distinct, almost reaching cotyle; articular surface of pygal square in outline, not triangular; up to seven well ossified carpals. See Russell (1967:157–158) for additional diagnostic postcranial characters, based on the neotype specimen

( FHSM VP- 401, Ectenosaurus clidastoides ).