Taphonomic history of a dinosaur skeleton from the upper Cretaceous Frenchman Formation, Canada: insights from ancient rhizoetchings and invertebrate bioerosion trace fossils

Bioerosion trace fossils are biogenic structures that record evidence of behaviour in hard substrates, including bone. While bioerosion trace fossils on bones produced by animals have been well documented globally throughout the Mesozoic and Cenozoic, studies on such structures created by ancient plants are less common. Herein, we document an incomplete Triceratops skeleton from the latest Maastrichtian Frenchman Formation in southwestern Saskatchewan, Canada, which features several bioerosion trace fossils. The quarry containing the specimen consists of a blocky white to pink organic-rich mudstone, with a dense system of fossil root structures surrounding the bone material. This mudstone is interpreted as a heavily vegetated floodplain paleosol. Fossilized plant material associated with the Triceratops bones is preserved as compressed, black carbonaceous root structures lying within shallow horizontal furrows penetrating the cortical surface of the bone (i.e. rhizoetchings). Additional trace fossils include Amphifaoichnus seilacheri and Cubiculum inornatus, which are thought to have been produced by insects. This study contributes to our understanding of the taphonomic processes that affect Cretaceous vertebrate deposits and may elucidate the previously unappreciated role ancient plants played in the preservation and taphonomy of dinosaur skeletons.