Edmontosaurus regalis, Lambe, 1917

Surmik, Dawid, Słowiak-Morkovina, Justyna, Szczygielski, Tomasz, Wojtyniak, Marcin, Środek, Dorota, Dulski, Mateusz, Balin, Katarzyna, Krzykawski, Tomasz & Pawlicki, Roman, 2023, The first record of fossilized soft parts in ossified tendons and implications for the understanding of tendon mineralization, Zoological Journal of the Linnean Society 198 (3), pp. 747-766 : 751

Edmontosaurus regalis (UAMES 52615)

Both cross-sectioned tendons show a highly porous structure built of fibrous primary matrix ( Fig. 1A–C ). The general structure of the sectioned tendons is homogenous. The matrix is composed of coarse collagenous fibre bundles containing numerous bone cell lacunae ( Fig. 1A, C ). The vascular canals forming the porous structure of the tendons are young Haversian canals ( Fig. 1A–C ). The cross-sectioned larger tendon shows few scattered secondary osteons in the centre of the tendon surrounded by collagen-fibre bundles ( Fig. 1D ). The tendon of a slightly smaller cross-section (3.5 mm diameter; Fig. 1A, B ) is more porous than the larger one (6 mm; Fig. 1C, D ). The different structure between the sampled tendons may result from a different location in the body.

Figures

Figure 1. Light microscopy and SEM of petrographic thin sections and etched surfaces of fossilized ornithischian tendons of Edmontosaurus regalis: A, B, ground section (transverse) of the smaller tendon under transmitted normal light (A) and polarized light alpha-compensation mode (B) exhibiting primary organization of tissue; C, D, ground section (transverse) of the periphery (C) (under transmitted normal light) and centre (D) (under polarized light) of the larger tendon; E, circular backscatter detector (CBS-SEM) image of the etched surface of the tendon shows structures interpreted as vascular canals with vessel-like morphology and attached cell-like structures, well visible branched protrusions (red arrow) are also visible; F, CBS-SEM image longitudinal section of the vessel-like canals with cell-like structures attached to the wall (blue arrow). White arrows indicate young Haversian canals, green mark secondary osteons, and yellow point at bone cell lacunae.