Ngwevu intloko: a new early sauropodomorph dinosaur from the Lower Jurassic Elliot Formation of South Africa and comments on cranial ontogeny in Massospondylus carinatus.

Kimberley E.J Chapelle,Paul M Barrett,Jennifer Botha,Jonah N Choiniere

doi:10.7717/peerj.7240

Kimberley E.J Chapelle, Paul M Barrett + Show 2 more

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https://doi.org/10.7717/peerj.7240

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Abstract

Our knowledge of Early Jurassic palaeobiodiversity in the upper Elliot Formation of South Africa has increased markedly in recent years with the discovery of new fossils, re-assessments of previously collected material and a better understanding of Stormberg Group stratigraphy. Here, Ngwevu intloko, a new genus of upper Elliot basal sauropodomorph is named on the basis of a complete skull and partial skeleton (BP/1/4779) previously assigned to Massospondylus carinatus. It can be distinguished from all other basal sauropodomorphs by a combination of 16 cranial and six postcranial characters. The new species is compared to a small ontogenetic series of M. carinatus as well as to a range of closely related taxa. Taphonomic deformation, sexual dimorphism and ontogeny are rejected as possible explanations for the morphological differences present between BP/1/4779 and other taxa. Osteohistological examination reveals that BP/1/4779 had nearly reached adult size at the time of its death at a minimum age of 10 years.

Highlights

Massospondylus carinatus is an iconic basal sauropodomorph dinosaur from the Lower Jurassic upper Elliot and Clarens formations of South Africa, Lesotho and from temporally equivalent formations in Zimbabwe
BP/1/4779 is compared to the holotype of M. carinatus and two other specimens that can confidently be referred to that taxon on the basis of shared cranial and postcranial characters (BP/1/4934, BP/1/5241, BP/1/4376) (Gow, Kitching & Raath, 1990; Sues et al, 2004; Chapelle & Choiniere, 2018; Barrett et al, 2019)
One other specimen in the ESI collections was recovered from this locality, comprising of medium-sized postcranial remains of an unidentified sauropodomorph

Summary

Introduction

Massospondylus carinatus is an iconic basal sauropodomorph dinosaur from the Lower Jurassic upper Elliot and Clarens formations of South Africa, Lesotho and from temporally equivalent formations in Zimbabwe (e.g. the Forest Sandstone Formation). It is the most common dinosaur in these deposits, and for more than 30 years was considered the only valid sauropodomorph taxon across its stratigraphic range in southern Africa Massospondylus was established as the nominal taxon for the uppermost biozone in the Stormberg Supergroup, the Massospondylus Range Zone (Kitching & Raath, 1984)

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