Molecular tests support the viability of rare earth elements as proxies for fossil biomolecule preservation

Abstract

The rare earth element (REE) composition of a fossil bone reflects its chemical alteration during diagenesis. Consequently, fossils presenting low REE concentrations and/or REE profiles indicative of simple diffusion, signifying minimal alteration, have been proposed as ideal candidates for paleomolecular investigation. We directly tested this prediction by conducting multiple biomolecular assays on a well-preserved fibula of the dinosaur Edmontosaurus from the Cretaceous Hell Creek Formation previously found to exhibit low REE concentrations and steeply-declining REE profiles. Gel electrophoresis identified the presence of organic material in this specimen, and subsequent immunofluorescence and enzyme-linked immunosorbant assays identified preservation of epitopes of the structural protein collagen I. Our results thereby support the utility of REE profiles as proxies for soft tissue and biomolecular preservation in fossil bones. Based on considerations of trace element taphonomy, we also draw predictions as to the biomolecular recovery potential of additional REE profile types exhibited by fossil bones.

Taphonomic and Diagenetic Pathways to Protein Preservation, Part I: The Case of Tyrannosaurus rex Specimen MOR 1125

“…and R.D.A.) on the Standing Rock Hadrosaur Site (SRHS) [21,46]. Despite the somewhat contrasting taphonomic and diagenetic histories of T. rex MOR 1125 and Edmontosaurus bones from SRHS [46,51], both have been shown to retain endogenous cells, soft tissues [50,51], and collagen I protein [21,22,52].…”

“…on the Standing Rock Hadrosaur Site (SRHS) [21,46]. Despite the somewhat contrasting taphonomic and diagenetic histories of T. rex MOR 1125 and Edmontosaurus bones from SRHS [46,51], both have been shown to retain endogenous cells, soft tissues [50,51], and collagen I protein [21,22,52]. More importantly, these specimens still share certain geochemical similarities indicative of diagenetic circumstances in common between these two sites that have evidently permitted long-term biomolecular preservation in fossil bones.…”

“…Yet, as discussed in detail by several recent reviews [2][3][4][5][6][7], innovative adaptations of molecular biology techniques toward analyzing fossil samples and significant advances in analytical resolution have proven that recognizable biomolecules persist in many, diverse fossils. Ancient DNA and even entire nuclear and mitochondrial genomes are now being recovered from Pleistocene fossils [8][9][10][11][12], some of which are older than 1 My [13], and proteins such as collagen I, hemoglobin, and β-keratin have been identified within vertebrate fossils dating back to the Jurassic [14][15][16][17][18][19][20][21]. Collagen I peptides have even been recovered from two Cretaceous non-avian dinosaur bones [18,22,23], and cladistic analyses found those peptides to place non-avian dinosaurs in their expected phylogenetic context within Archosauria [18,24], thus corroborating their authenticity.…”

Combining elemental and immunochemical analyses to characterize diagenetic alteration patterns in ancient skeletal remains

“…Some essential trace elements, abundant during life, decrease after burial while others, such as rare earth elements (REE) and uranium (U), are incorporated during diagenesis. Moreover, hydrolysis may induce the breakage of the peptide bonds, leading to the decomposition of proteinaceous materials 9 , 21 – 26 . These phenomena could result in a heterogeneous preservation of the organic fraction within the same specimen.…”

Geology and taphonomy of a unique tyrannosaurid bonebed from the upper Campanian Kaiparowits Formation of southern Utah: implications for tyrannosaurid gregariousness

“…This is corroborated by the HREE-depleted signature of RUQ fossils, which is typical of high suspension load or colloid-rich fluvial environments like floodplains ( Herwartz et al, 2013 ; Rousseau et al, 2015 ), indicating REE infusion of fossils and peds was essentially complete prior to incorporation into the channel setting of units 4 and 5, which would have enriched the bones with HREEs ( Trueman, 1999 ). The overall lower abundance of REE in the bones also suggests very little diagenetic alteration and rapid fossilization ( Ullmann et al, 2020 ).…”