The phylogenetics of Teleosauroidea (Crocodylomorpha, Thalattosuchia) and implications for their ecology and evolution.

Michela M Johnson,Stephen L Brusatte,Mark T Young

doi:10.7717/peerj.9808

Abstract

Teleosauroidea was a clade of ancient crocodylomorphs that were a key element of coastal marine environments during the Jurassic. Despite a 300-year research history and a recent renaissance in the study of their morphology and taxonomy, macroevolutionary studies of teleosauroids are currently limited by our poor understanding of their phylogenetic interrelationships. One major problem is the genus Steneosaurus, a wastebasket taxon recovered as paraphyletic or polyphyletic in phylogenetic analyses. We constructed a newly updated phylogenetic data matrix containing 153 taxa (27 teleosauroids, eight of which were newly added) and 502 characters, which we analysed under maximum parsimony using TNT 1.5 (weighted and unweighted analyses) and Bayesian inference using MrBayes v3.2.6 (standard, gamma and variation). The resulting topologies were then analysed to generate comprehensive higher-level phylogenetic hypotheses of teleosauroids and shed light on species-level interrelationships within the clade. The results from our parsimony and Bayesian analyses are largely consistent. Two large subclades within Teleosauroidea are recovered, and they are morphologically, ecologically and biogeographically distinct from one another. Based on comparative anatomical and phylogenetic results, we propose the following major taxonomic revisions to Teleosauroidea: (1) redefining Teleosauridae; (2) introducing one new family and three new subfamilies; (3) the resurrection of three historical genera; and (4) erecting seven new generic names and one new species name. The phylogeny infers that the Laurasian subclade was more phenotypically plastic overall than the Sub-Boreal-Gondwanan subclade. The proposed phylogeny shows that teleosauroids were more diverse than previously thought, in terms of morphology, ecology, dispersal and abundance, and that they represented some of the most successful crocodylomorphs during the Jurassic.

Highlights

Teleosauroid crocodylomorphs—distant extinct relatives of extant crocodylians—were a near-globally distributed cladeHow to cite this article Johnson MM, Young MT, Brusatte SL. 2020
The results showed that Machimosaurus and Lemmysuchus occupied the crunch guild, which is specialized for handling hard prey; the remaining taxa (Mycterosuchus, Charitomenosuchus, Neosteneosaurus and Proexochokefalos) fit into the pierce guild, hypothesized to prefer softer prey such as smaller fishes and squid
We firstly proposed the following changes to teleosauroid nomenclature, as a direct result of the invalidity of Steneosaurus: seven new generic names (Plagiophthalmosuchus, Clovesuurdameredeor, Seldsienean, Charitomenosuchus, Proexochokefalos, Andrianavoay and Neosteneosaurus) and one new species (Indosinosuchus kalasinensis); and the resurrection of three historical genera (Macrospondylus, Aeolodon and Sericodon)

Summary

Introduction

Teleosauroid crocodylomorphs—distant extinct relatives of extant crocodylians (which include alligators, crocodiles, caimans and gavials)—were a near-globally distributed cladeHow to cite this article Johnson MM, Young MT, Brusatte SL. 2020. The validity of Steneosaurus has recently been called into question (Jouve et al, 2017; Johnson, Young & Brusatte, 2020) as the type specimen of the type species, Steneosaurus rostromajor Geoffroy Saint-Hilaire, 1825 (MNHN.RJN 134c-d), has rarely been referenced or figured in the literature since its preliminary descriptions by Cuvier (1800, 1808, 1812, 1824) and Geoffroy Saint-Hilaire (1825, 1831) Another problematic issue reinforced during the 20th Century (Andrews, 1909, 1913) is the contention that while there are noticeable differences between the skulls of teleosauroid species, the postcranial skeleton only shows superficial differences. Recent studies (Young et al, 2014; Johnson et al, 2017; Foffa et al, 2019; Martin et al, 2016, 2019; Wilberg, Turner & Brochu, 2019) have begun to dispute this notion, showing, in terms of postcranial anatomy and palaeoenvironment, that teleosauroids were more diverse than originally thought

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