Difficulties in assigning trace makers from theropodan bite marks: an example from a young diplodocoid sauropod

Bite marks on the bones of dinosaurs are relatively rare for non‐tyrannosaur dominated faunas, and few have been described in detail. Here, we describe a femur of a young diplodocoid sauropod in the Carnegie Quarry (Late Jurassic Morrison Formation) at Dinosaur National Monument that shows extensive bite marks to the proximal part of the bone. This is the only record of bite marks from this extensive quarry of over 1500 vertebrate elements, making this a most unusual find. Identification of the tracemaker is difficult as multiple large theropods are known from the quarry. Furthermore, we show that subtly different actions of feeding can potentially result in very different spacing of bite marks making matches to tooth patterns in the jaws of potential bite makers very uncertain. Although identification is uncertain, the tracemaker is clearly not a tyrannosaurid, but the selective scrape feeding pattern seen here is similar to the of tyrannosaurid theropods. This technique may be more widely distributed among large carnivorous theropods than previously realized.