Abstract
Direct evidence of paleoecological processes is often rare when the fossil record is poor, as in the case of the Cretaceous of eastern North America. Here, I describe a femur and partial tibia shaft assignable to theropods from two Late Cretaceous sites in New Jersey. The former, identifiable as the femur of a large ornithomimosaur, bears several scores interpreted as shark feeding traces. The tibia shaft has punctures and flaked bone from the bites of mid-sized crocodyliforms, the first documented occurrence of crocodyliform traces on dinosaur bone from the Maastrichtian of the Atlantic Coastal Plain. The surface of the partial tibia is also littered with indentations interpreted as the traces of invertebrates, revealing a microcosm of biological interaction on the coastal seafloor of the Cretaceous Atlantic Ocean. Massive crocodyliforms, such as Deinosuchus rugosus and the slightly smaller Deltasuchus motherali, maintained the role of terrestrial vertebrate taphonomic process drivers in eastern North America during the Cretaceous. The report of crocodyliform bite marks on the ornithomimosaur tibia shaft in this manuscript reinforces the importance of the role of crocodyliforms in the modification of terrestrial vertebrate remains during the Cretaceous in North America. The preserved invertebrate traces add to the sparse record of the presence of barnacles and other marine invertebrates on dinosaur bone, and the evidence of shark feeding on the ornithomimosaur femur support the “bloat-and-float” model of terrestrial vertebrate fossil deposition in marine deposits from the Cretaceous of eastern North America.
Highlights
Despite a poor fossil record, one pattern that has emerged in the study of the paleoecology of eastern North America during the Cretaceous is the frequency of vertebrate remains—especially those of turtles and dinosaurs—that show evidence of feeding by
In the Campanian, evidence of crocodyliform feeding on dinosaurs and turtles from multiple geological units in the southeastern United States and from the Marshalltown Formation of New Jersey have been attributed to the massive crocodylian Deinosuchus rugosus, a species populous along the eastern North American coastline during that time (e.g., Schwimmer et al, 1993; Gallagher, 1995; Schwimmer, 1997; Schwimmer, 2002; Schwimmer, 2010; Schwimmer et al, 2015)
No record of large crocodyliform bite marks on dinosaur material has been reported from the Maastrichtian of eastern North America, when Deinosuchus disappears from the fossil record (Schwimmer, 2002)
Summary
Crocodyliform bite marks on vertebrate remains are well-represented throughout the Mesozoic and Cenozoic and have been extensively described (e.g., Carpenter & Lindsey, 1980; Binford, 1981; Erickson, 1984; Davidson & Soloman, 1990; Schwimmer, 2002; Forrest, 2003; Fuentes, 2003; Cisneros, 2005; Milukas et al, 2006; Njau & Blumenschine, 2006; Schwimmer, 2010; Noto, Main & Drumheller, 2012; Boyd, Drumheller & Gates, 2013; Martin, 2013; Drumheller & Brochu, 2014; Drumheller & Brochu, 2016; Njau & Gilbert, 2016). Such marks have been documented in fossils from the Cenomanian Woodbine Formation of Texas and attributed to the bites of individuals of the taxon Deltasuchus motherali (Noto, Main & Drumheller, 2012; Adams, Noto & Drumheller, 2017). In the Campanian, evidence of crocodyliform feeding on dinosaurs and turtles from multiple geological units in the southeastern United States and from the Marshalltown Formation of New Jersey have been attributed to the massive crocodylian Deinosuchus rugosus, a species populous along the eastern North American coastline during that time (e.g., Schwimmer et al, 1993; Gallagher, 1995; Schwimmer, 1997; Schwimmer, 2002; Schwimmer, 2010; Schwimmer et al, 2015). Borealosuchus threeensis and Thoracosaurus neocesariensis seem to have grown the largest; individuals of the both taxa achieved sizes of 5 or more meters, and one Thoracosaurus specimen may have reached 7–8 m in length (e.g., Schwimmer, 2002; Brochu et al, 2012)
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