SimbirskiasaurusandPervushovisaurusreassessed: implications for the taxonomy and cranial osteology of Cretaceous platypterygiine ichthyosaurs

Abstract

The ichthyosaur fossil record is interspersed by several hiatuses, notably during the Cretaceous. This hampers our understanding of the evolution and extinction of this group of marine reptiles during the last 50 million years of its history. Several Cretaceous ichthyosaur taxa named in the past have subsequently been dismissed and referred to the highly inclusive taxon Platypterygius, a trend that has created the impression of low Cretaceous ichthyosaur diversity. Here, we describe the cranial osteology, reassess the stratigraphic age, and evaluate the taxonomy and phylogenetic relationships of two Cretaceous ichthyosaurs from western Russia: Simbirskiasaurus birjukovi from the early Barremian and Pervushovisaurus bannovkensis from the middle Cenomanian, both formerly regarded as nomina dubia, and allocated to Platypterygius sp. and Platypterygius campylodon, respectively. We show that Simbirskiasaurus birjukovi and Pervushovisaurus bannovkensis are valid platypterygiine ophthalmosaurids, notably characterized by a peculiar narial aperture. The cranial anatomy and phylogenetic relationships of these taxa illuminate the evolution of narial aperture anatomy in Cretaceous ichthyosaurs, clarify the phylogenetic relationships among platypterygiines, and provide further arguments for a thorough revision of Platypterygius.

The evolution and extinction of the ichthyosaurs from the perspective of quantitative ecospace modelling

“…Our results suggest that despite recent discoveries increasing the taxonomic diversity of the Cretaceous ichthyosaurs [15], their ecospace and niche diversity had failed to increase since collapsing in the Middle Jurassic. Where the ichthyosaurs lost a particular ecospace, they appear to have been unable to recolonize it (figures 1 and 2).…”

Peer Review #2 of "A new specimen of Palvennia hoybergeti: implications for cranial and pectoral girdle anatomy in ophthalmosaurid ichthyosaurs (v0.1)"

“…It is similar to that in the holotype (SVB1451) (Druckenmiller et al, 2012), but because it is disarticulated, additional details can be added. The dorsalmost portion of the dorsal projection shows an interdigitating structure with the prefrontal as in Platypterygius australis, Ophthalmosaurus icenicus and Simbirskiasaurus birjukovi (Kear, 2005;Fischer et al, 2014a;Moon & Kirton, 2016), and some of the projections of the prefrontal are preserved. The dorsal projection and middle part of the element are PeerJ reviewing PDF | (2018:05:28469:1:1:NEW 28 Aug 2018)…”

“…obs.) (Arkhangelsky, 1997) and Simbirskiasaurus birjukovi (Fischer et al, 2014a). On the lateral surface, fine striations radiate from the dorsal end of the narrow margin and in all directions.…”

Restos apendiculares de un ictiosaurio oftalmosáurido del Barremiano inferior de Villa de Leiva, Colombia

“…P. ochevi y P. campylodon son considerados como species inquirenda por Fischer et al (2016). (Maxwell y Caldwell, 2006a;Maxwell y Caldwell, 2006b;Maxwell, 2010;Druckenmiller y Maxwell, 2010;Fischer et al, 2011a;Fernández y Maxwell, 2012;Druckenmiller et al, 2012;Fischer, 2012;Fischer et al, 2012;Roberts et al, 2014;Fischer et al, 2014a;Fischer et al, 2014b;Ji et al, 2016;Paparella et al, 2017;Maxwell et al, 2016;Fischer et al, 2016). Un panorama de estos aportes, con sus respectivas referencias, se expone sintéticamente en la revisión de las ocurrencias de especímenes de oftalmosáuridos presentada por Fernández y Campos (2015).…”

“…En el trabajo de Fischer et al (2012) (Fischer et al, 2013a;Fischer et al, 2014a;Fischer et al, 2014b;Roberts et al, 2014;Druckenmiller y Maxwell, 2014;Zverkov et al, 2015). Sin embargo, en algunos análisis filogenéticos no se reconocen subgrupos dentro de Ophthalmosauridae (Fernández y Talevi, 2014;Maxwell et al, 2015;Ji et al, 2016).…”