A new leptonectid ichthyosaur from the Lower Jurassic (Hettangian) of Nottinghamshire, England, UK, and the taxonomic usefulness of the ichthyosaurian coracoid

Abstract

Thousands of ichthyosaurs have been discovered from the rich Lower Jurassic deposits of the UK, with the majority collected from along the Lyme Regis-Charmouth area of the Dorset coast. Here, I describe a new leptonectid ichthyosaur, Wahlisaurus massarae gen. et sp. nov., based on a partial skull and an incomplete skeleton collected from the Lower Jurassic (Hettangian) of Nottinghamshire, England. Wahlisaurus can be referred to the Leptonectidae through the possession of an extremely slender and delicate snout, and a mandible shorter than the snout which produces an overbite. This referral is supported by a phylogenetic analysis. The new taxon is distinguished from other ichthyosaurs through a unique combination of characters and autapomorphies of the pectoral girdle including the presence of both a scapularcoracoid foramen and a large and roughly ovoid coracoid foramen. A coracoid foramen has only previously been reported in the Triassic ichthyosaur Cymbospondylus. The peculiar coracoid morphology further highlights the taxonomic utility of coracoids in ichthyosaurs. The aforementioned features demonstrate that W. massarae cannot be referred to any currently recognized leptonectid. Wahlisaurus is the ninth Lower Jurassic ichthyosaur genus to be recognized worldwide, and the fifth documented in the Lower Lias Group.http://zoobank.org/urn:lsid:zoobank.org:pub:EE500E11-66AB-43C8-BB59-F21654763241

First report of Leptonectes (Ichthyosauria: Leptonectidae) from the Lower Jurassic (Pliensbachian) of Asturias, northern Spain

“…In the case of Ichthyosaurus communis and I. intermedius, historically differentiated on the basis of tooth morphology, Massare and Lomax (2017) recognized different morphologies, although they pointed out that tooth features were not reliable to distinguish these two species. Nevertheless, the dentition pattern of MUJA 4095 is consistent with that of Leptonectidae, particularly with MUJA 3687 and differs from that of Wahlisaurus massarae characterized by recurved crowns and large, bulbous infolded roots (Lomax, 2016). On the other hand, teeth of MUJA 4095 are inconsistent with tooth morphology of the other Lower Jurassic ichthyosaurs such as Temnodontosaurus, Ichthyosaurus and Stenopterygius, even considering ontogenetic change (Dick and Maxwell, 2015).…”

“…This prog-ress is mainly triggered by re-examinations of British collections (e.g., Lomax andMassare, 2012, 2015;Lomax and Gibson, 2015;Martin et al, 2012;Massare and Lomax, 2016a, 2016b, and demonstrated that alpha taxonomy of iconic species represented by complete and, in most of the cases, well-preserved, specimens were in need of revision. It also highlights the need of increasing character sampling, but also the importance of systematic revisions of historical collections.…”

“…Within the genus Leptonectes, besides the type species L. tenuirostris Conybeare, 1822, there are two other valid species: L. solei McGowan, 1993and L. moorei McGowan and Milner, 1999(McGowan and Motani, 2003Lomax, 2016). Leptonectes tenuirostris is well known by several specimens (McGowan, 1989), and it has the longest stratigraphic range (probably from the Rhaetian up to the late Pliensbachian, Maisch and Reisdorf, 2006), and the widest geographic occurrence among leptonectids, including records from England (McGowan, 1996), Belgium (Godefroit, 1992), Germany (Maisch, 1999) and Switzerland (Maisch and Reisdorf, 2006).…”

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

“…Individual or intrageneric variation is known from taxa with many specimens such as Stenopterygius and Ichthyosaurus, for instance in the shape and size of the anterior notch (Johnson, 1979;Lomax, Massare & Mistry, 2017). However, the PCA, discriminant analysis and the MANOVA test show that there is a phylogenetic signal in the coracoid shape, as argued by Lomax (2017;Lomax, Evans & Carpenter, 2018). The phylogenetic character presently in use to cover the phylogenetic variation in coracoids is the relationship between length and width (Fischer et al, 2016).…”

“…Ichthyopterygia was one of the major secondarily aquatic vertebrate clades that existed during The taxonomic utility of the post-Triassic ichthyosaurian pectoral girdle has been challenged (Maxwell & Druckenmiller, 2011;Lomax, 2017). Because seven SML specimens with relatively well-preserved pectoral girdles have now been recovered, it provides an opportunity to test the assertion that there is little taxonomic signal in the pectoral girdles.…”