Digital 3D models of theropods for approaching body-mass distribution and volume

Matías Reolid,Jesús Reolid,Francisco J Cardenal

doi:10.1007/s41513-021-00172-1

Abstract

The aim of this work is to obtain diverse morphometric data from digitized 3D models of scientifically accurate palaeoreconstructions of theropods from eight representative families. The analysed polyvinyl chloride (PVC) models belong to the genera Coelophysis, Dilophosaurus, Ceratosaurus, Allosaurus, Baryonyx, Carnotaurus, Giganotosaurus, and Tyrannosaurus. The scanned 3D models were scaled considering different body-size estimations of the literature. The 3D analysis of these genera provides information on the skull length and body length that allows for recognition of major evolutionary trends. The skull length/body length in the studied genera increases according with the size of the body from the smallest Coelophysis with a ratio of 0.093 to ratios of 0.119–0.120 for Tyrannosaurus and Giganotosaurus, the largest study theropods. The study of photogrammetric 3D models also provides morphometric information that cannot be obtained from the study of bones alone, but knowing that all reconstructions begin from the fossil bones, such as the surface/volume ratio (S/V). For the studied theropod genera surface/volume ratio ranges from 35.21 for Coelophysis to 5.55 for Tyrannosaurus. This parameter, closely related to the heat dissipation, help in the characterization of the metabolism of extinct taxa. Accordingly, slender primitive forms of the Early Jurassic (i.e. Coelophysis and Dilophosaurus) had relatively smaller skulls and higher mass-specific metabolic rates than the robust large theropods of the Cretaceous (i.e. Giganotosaurus and Tyrannosaurus). This work presents a technique that, when applied to proper dinosaur models, provides extent and accurate data that may help in diverse study areas within the dinosaur palaeontology and palaeobiology.

Highlights

The Suborder Theropoda is a monophyletic group traditionally included within the Order Saurischia (e.g. Seeley, 1888; Ferigolo and Langer, 2006)
With the exception of Coelophysis, the figures were selected without feather entanglement even if some similar taxa have been proposed to have it from different kinds of theropods included small-sized relatives of Tyrannosaurus rex (Xu et al, 2004; Xu and Norell, 2005; Brusatte et al, 2010b)
The surface estimated according to the scaled model is 1.44 m2 for a volume of 0.041 m3. When applying this approach to other specimens described in the literature (Table 5), the Coelophysis bodymass ranges from 21 kg to 33 kg ((UCMP 129,618, 2.75 m; Molina-Pérez and Larramendi, 2019)

Summary

Introduction

The Suborder Theropoda is a monophyletic group traditionally included within the Order Saurischia (e.g. Seeley, 1888; Ferigolo and Langer, 2006). The Suborder Theropoda is a monophyletic group traditionally included within the Order Saurischia Recently Theropoda was included in the clade Ornithoscelida (Baron et al, 2017) that comprises the Order Ornithischia, but there is a controversy about this proposal (Langer et al, 2017). All theropods were clawed biped with sharp, sometimes serrated teeth. Hollow bones, in both vertebrae and limbs, are a common feature of theropods. The increasing head size, mainly in large theropods of Ceratosauria, Carnosauria, and Tyrannosauroidea, among others, required downsizing of other parts of the front half of the body to remain balanced with the back half at the hip, some groups had notoriously short arms.

Objectives

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Conclusion