Chemistry supports the identification of gender-specific reproductive tissue in Tyrannosaurus rex

Abstract

Medullary bone (MB), an estrogen-dependent reproductive tissue present in extant gravid birds, is texturally, histologically and compositionally distinct from other bone types. Phylogenetic proximity led to the proposal that MB would be present in non-avian dinosaurs, and recent studies have used microscopic, morphological, and regional homologies to identify this reproductive tissue in both theropod and ornithischian dinosaurs. Here, we capitalize on the unique chemical and histological fingerprint of MB in birds to characterize, at the molecular level, MB in the non-avian theropod Tyrannosaurus rex (MOR 1125), and show that the retention of original molecular components in fossils allows deeper physiological and evolutionary questions to be addressed.

Life Inside a Dinosaur Bone: a Thriving Microbiome

“…We detected no evidence of endogenous proteins in the bone studied here and are therefore unable to replicate the claims of protein survival deep into the fossil record, such as the Mesozoic (Pawlicki et al 1966;Schweitzer et al 2005aSchweitzer et al , 2007aSchweitzer et al , 2007bSchweitzer et al , 2008Schweitzer et al , 2009Schweitzer et al , 2013Schweitzer et al , 2014Schweitzer et al , 2016Asara et al 2007;Organ et al 2008;Schweitzer 2011;Bertazzo et al 2015;Cleland et al 2015;Schroeter et al 2017). In contrast, recent Pleistocene-Holocene material can exhibit clear evidence along multiple lines of investigation for endogenous, ancient collagen, even when the fossil (dentine/enamel in this case) is stained black, indicating taphonomic alteration, and the sample is found exhumed in a warm climate and not treated with aseptic techniques.…”

“…Dinosaur bone has been reported to contain endogenous organics such as collagen, osteocytes, and blood vessels. These reports, if verified, could radically change the study of macroevolution and the physiology of extinct organisms given the immense potential of protein sequence data to shed light on the biology and systematics of extinct organisms (Pawlicki et al 1966;Schweitzer et al 2005aSchweitzer et al , 2005bSchweitzer et al , 2007aSchweitzer et al , 2007bSchweitzer et al , 2008Schweitzer et al , 2009Schweitzer et al , 2013Schweitzer et al , 2014Schweitzer et al , 2016Asara et al 2007;Organ et al 2008;Schweitzer 2011;Bertazzo et al 2015;Cleland et al 2015;Schroeter et al 2017). Most of these reports rely on structural observations, mass spectrometry, and immunohistochemistry.…”

Paleoproteomics of Mesozoic Dinosaurs and Other Mesozoic Fossils

“…Histochemical stains have also been employed to suggest the presence of DNA and other compounds in well‐preserved dinosaur bone, because these indicate the presence of biochemicals within fossil tissues still capable of uptaking stains. These techniques are not as specific as other methods, because many histochemical stains react to rather general chemical properties within tissues (e.g., acidic, basic, or amine‐containing groups).…”

“…Dinosaurs saw the origination of many evolutionary novelties, including feathers, gigantism, and endothermy; how these changes accumulated in this lineage is a molecular question. Dinosaurs biologically addressed osteoporosis during lay, adapted to an obligate vegetarian diet from a carnivorous ancestry, and faced other issues that have also arisen in the human lineage, and they responded at the molecular level. To close off these avenues of investigation because conventional wisdom disallows protein preservation across deep time closes the door on a potential source of information that may benefit humans.…”

Evolução morfológica de Ceratosauria e Tyrannosauroidea (Dinosauria: Theropoda)

“…Parte do interesse e do número de estudos para com Tyrannosauroidea se deve ao fato de diversos espécimes estarem disponíveis, inclusive espécimes com filamentos homólogos às penas Xu et al, 2004Xu et al, , 2012, além do grande interesse popular pelo grupo (Brochu, 2003;Brusatte et al, 2010b;Hone, 2016). O número de espécimes preservados permitiu a descrição qualitativa dos caracteres ontogenéticos em Tyrannosauridae (Carr, 1999;Carr & Williamson, 2004); observação da variação sexual em Tyrannosaurus por meio de comparações morfológicas (Larson, P., 2008) e químicas (Schweitzer et al, 2016), além do entendimento mais amplo dentre todos os grupos de Theropoda (Hone, 2016). Dessa forma, apesar de numeroso o registro e da variedade morfológica de Ceratosauria, Tyrannosauroidea tem recebido mais atenção da comunidade científica e popular.…”