Abstract
AbstractTeleosauroidea was a clade of successful, morphologically diverse, ancient crocodylomorphs that were integral in coastal marine/lagoonal environments during the Jurassic. Within Teleosauroidea, the macrophagous/durophagous tribe Machimosaurini evolved specialized feeding strategies (e.g. hypertrophied jaw musculature and blunt, heavily ornamented dentition) and large body sizes (> 7 m), becoming an important component of Middle and Late Jurassic ecosystems. These ocean-dwelling giants are well known from the Callovian (Lemmysuchus) of Europe and the UK, and from the Kimmeridgian–Tithonian (Machimosaurus) of Europe and northern Africa. There are reports of fragmentary machimosaurin material from the Bathonian of Africa, but the overall Bathonian teleosauroid material is poorly understood. While multiple specimens were described during the 19th and 20th centuries, little research has been done since. Here we re-describe two historically important Bathonian species from near Oxford, UK. We demonstrate that both ‘Steneosaurus’ larteti and ‘Steneosaurus’ boutilieri are valid taxa and we establish neotypes for both species and two new genera, Deslongchampsina and Yvridiosuchus. Our cladistic analysis finds Yvridiosuchus boutilieri as a basal member of Machimosaurini and Deslongchampsina lartetito be closely related to Steneosaurus heberti. Interestingly, four distinct teleosauroid ecomorphotypes are present in the Bathonian of Europe and teleosauroid ecomorphological diversity continued throughout the Callovian and Kimmeridgian/Tithonian in Europe and England.
Highlights
Yvridiosuchus boutilieri is recovered in a polytomy with Lemmysuchus obtusidens and Machimosaurus taxa, but is clearly situated within the tribe Machimosaurini
Deslongchampsina larteti is recovered in an unresolved position with Steneosaurus heberti, and the clade containing Steneosaurus edwardsi and Machimosaurini
It is interesting to note that Steneosaurus gracilirostris, currently considered the basal-most teleosauroid, forms an unresolved polytomy with Steneosaurus bollensis, ‘Steneosaurus’ brevior and the Chinese teleosauroid (IVPP V 10098)
Summary
Teleosauroids (Thalattosuchia) were a unique group of distant extinct relatives of modern crocodiles that inhabited marine and brackish ecosystems throughout the Jurassic (Buffetaut, et al, 1981; Buffetaut, 1982; Andrews, 1913; Hua, 1999; Foffa et al, 2015, in press; Johnson et al, 2015, 2017, 2018; Martin et al, 2016) and Early Cretaceous (Fanti et al, 2016) This near-global group of ancient crocodylomorphs have often been regarded as the Jurassic marine equivalents of extant gavials, due to many species having an elongate and tubular snout, high tooth count and dorsally directed orbits, which is suggestive of a primarily piscivorous diet (Andrews, 1909, 1913; Buffetaut, 1982). By the end Kimmeridgian-earliest Tithonian, they had evolved into species adapted to living in highenergy environments (Machimosaurus mosae Sauvage & Liénard, 1879: Hua, 1999; Young et al, 2014a) and others suited to life in open seas (Machimosaurus hugii von Meyer, 1837: Krebs, 1967; Young et al, 2014a)
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