A new specimen ofPalvennia hoybergeti: implications for cranial and pectoral girdle anatomy in ophthalmosaurid ichthyosaurs

Abstract

The Late Jurassic Slottsmøya Member Lagerstätte on Spitsbergen preserves a diverse array of marine reptiles, including four named taxa of ophthalmosaurid ichthyosaurs. One of these, Palvennia hoybergeti, is based on the single holotype specimen (SVB 1451) with an incomplete skull. A newly discovered specimen (PMO 222.669) with a disarticulated but largely complete skull and anterior postcranium is described, which considerably expands our knowledge of this taxon. Two additional new ophthalmosaurid specimens with pectoral girdles from the same member are described. The taxonomic utility of the ophthalmosaurid pectoral girdle is contentious, and an assessment of seven pectoral girdles from the Slottsmøya Member provides a basis for addressing this question via a 2D landmark principal component analysis of baracromian coracoids. The analysis reveals a taxonomic signal in the coracoids but also highlights the degree of individual variation. Commonly used phylogenetic characters do not fully encapsulate the degree of variation seen in coracoids and in some cases combine analogous features.

A prevalence ofArthropterygius(Ichthyosauria: Ophthalmosauridae) in the Late Jurassic—earliest Cretaceous of the Boreal Realm

“…Thereby here we provide only some additional observations on the referred specimens, with special reference to new specimens from Franz Joseph Land. For more details on cranial morphology of A. chrisorum see the description of PMO 222.669 in Delsett et al (2018). Some additional observations and different interpretations of some sutures in PMO 222.669 could be found in sections with the description of the nasal, prefrontal, parietal, basioccipital, basisphenoid, opisthotic, and stapes.…”

“…v.2018 Palvennia hoybergeti Druckenmiller et al, 2012; Delsett, Druckenmiller, Roberts, Hurum: 8, figs. 5–13 [ pars .…”

“…Skull . The skull of A. chrisorum is now well-known due to a new find from Svalbard (PMO 222.669; Delsett et al, 2018). Thereby here we provide only some additional observations on the referred specimens, with special reference to new specimens from Franz Joseph Land.…”

“…In PMO 222.669 both nasals are preserved in articulation. To the description of these elements provided by Delsett et al (2018), we could add that the nasal bears a pronounced lateral “wings” over the external naris (Figs. 2L and 2M).…”

New marine reptile fossils from the Oxfordian (Late Jurassic) of Greenland

“…GEUS 590347-85, -88, -89 and -91) display an eight-shaped cross-section typical of many thunnosaurians (Sander, 2000;McGowan & Motani, 2003). Exceptions to this include ophthalmosaurid specimens from the Slottsmøya Member Lagerstätte on Spitsbergen (Delsett et al 2017(Delsett et al , 2018, the Russian Acamptonectes densus and the North American Platypterygius americanus (Maxwell & Kear, 2010;Fischer et al 2012). Two of the rib fragments, where the inner structure is visible in cross-section, appear to have trabeculae arranged into rings.…”