Histology and Geochemistry of Allosaurus (Dinosauria: Theropoda) From the Cleveland-Lloyd Dinosaur Quarry (Late Jurassic, Utah): Paleobiological Implications

Christophe Ferrante,Lionel Cavin,Rossana Martini,Torsten Vennemann

doi:10.3389/feart.2021.641060

Christophe Ferrante, Lionel Cavin + Show 2 more

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https://doi.org/10.3389/feart.2021.641060

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Abstract

The Late JurassicAllosaurusis one of the better-studied dinosaurs. A histological and geochemical study of a tibia and a femur ofA. fragilisrecovered in the Upper Jurassic Cleveland-Lloyd Dinosaur Quarry, Utah, United States has been done in order to address growth characteristics of this species. The two bones, probably belonging to separate individuals, are among the largest known for this species, which make them suitable to address such issues. The inclusion of our data on femur growth markings in the previously published data reflects a range of growth variability rather than two distinct growth strategies. The tibia has a well-developed external fundamental system indicating somatic maturity achievement. Using a quantitative method of superimposition to retrocalculate missing lines of arrested growth, the tibia appears to correspond to an individual that reached its skeletal maturity at 22 years and died at approximately 26 years. In the tibia, the concentration of zinc, a potential biomarker associated with bone formation, displays a higher concentration in zones of rapid growth compared to annuli. There is no direct relationship between the values of δ18Opand the lines of arrested growth distribution. The absence of relations between the histological organization and an enrichment in REE of the bone, indicates that the variations of δ18Oplikely represent a diagenetic process rather than a primordial, biologic composition. However, the geochemical composition of the bones is not homogeneous along the sections, indicating that the signal variations have not been completely erased by diagenesis.

Highlights

Bone paleohistology, in particular skeletochronology, is a predominant method for reconstructing the life history of extinct vertebrates (e.g., Prondvai, 2017)
The primary tissue of both bones are formed by fibrolamellar bone and were deposited as zonal bone tissue with cyclical growth marks (CGMs)
Prondvai (2017), suggested, on the basis of a dataset published by Lee and Werning (2008), that the growth trajectories of A. fragilis have a high range of intraspecific variations

Summary

Introduction

In particular skeletochronology, is a predominant method for reconstructing the life history of extinct vertebrates (e.g., Prondvai, 2017). To assess the growth strategy of Allosaurus, Bybee et al (2006) estimated, on the basis of histological analyses of the largest individuals of the CLDQ, that skeletal maturity is reached between 13 and 19 years with a maximum growth rate at 15 ± 2 years. They did not find evidence of an External Fundamental System (EFS), indicating stabilization of growth, an incipient EFS has been reported from an isolated and fragmentary Allosaurus fibula (UUVP 6346). By counting lines of arrested growth (LAGs) and performing growth curve reconstructions, Lee and Werning (2008) estimated that Allosaurus was reproductively mature at 10 years. Bybee et al (2006) and Prondvai (2017) showed a wide range of intraspecific variation in growth strategies in Allosaurus fragilis

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