New theropod remains and implications for megaraptorid diversity in the Winton Formation (lower Upper Cretaceous), Queensland, Australia.

Matt A White,David A Elliott,Adele H Pentland,Alex G Cook,Stephen F Poropat,Phil R Bell,Samantha L Rigby,Trish Sloan

doi:10.1098/rsos.191462

Matt A White, David A Elliott + Show 6 more

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https://doi.org/10.1098/rsos.191462

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Abstract

The holotype specimen of the megaraptorid Australovenator wintonensis, from the Upper Cretaceous Winton Formation (Rolling Downs Group, Eromanga Basin) of central Queensland, is the most complete non-avian theropod found in Australia to date. In fact, the holotype of A. wintonensis and isolated megaraptorid teeth (possibly referable to Australovenator) constitute the only theropod body fossils reported from the Winton Formation. Herein, we describe a new fragmentary megaraptorid specimen from the Winton Formation, found near the type locality of A. wintonensis. The new specimen comprises parts of two vertebrae, two metatarsals, a pedal phalanx and multiple unidentifiable bone fragments. Although the new megaraptorid specimen is poorly preserved, it includes the only megaraptorid vertebrae known from Queensland. The presence of pleurocoels and highly pneumatic caudal centra with camerate and camellate internal structures permit the assignment of these remains to Megaraptora gen. et sp. indet. A morphological comparison revealed that the distal end of metatarsal II and the partial pedal phalanx II-1 of the new specimen are morphologically divergent from Australovenator. This might indicate the presence of a second megaraptorid taxon in the Winton Formation, or possibly intraspecific variation.

Highlights

Theropod discoveries in Australia are extremely rare and often constitute fragmentary and/or isolated bones
The likely positions of Age of Dinosaurs Fossil (AODF) and AODF within the vertebral series were estimated by comparisons with other megaraptorids [29,32,33,37,40,42]
AODF 968 would likely have been longer than it is wide or tall with a nearly flat endplate and no indication of paraphophyses. This combination of features is typical of caudal centra but unlike the anteroposteriorly short dorsal vertebrae and opisthocoleous cervical vertebrae of megaraptorans [29,32,40]

Summary

Introduction

Theropod discoveries in Australia are extremely rare and often constitute fragmentary and/or isolated bones Their precise phylogenetic affinities have often proven difficult to determine with any certainty [1]. At least six Australian non-avian theropod taxa have been named, most of these are represented by only a single element and are regarded— not always universally— as nomina dubia. Numerous fragmentary specimens have been reported from South America (see supplementary table 7 in [1]), which include the oldest (Albian [43]) and the youngest (Campanian [44])

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