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 domi-nated faunas, and few have been described in detail. Here, we describe a femur of ayoung diplodocoid sauropod in the Carnegie Quarry (Late Jurassic Morrison Forma-tion) at Dinosaur National Monument that shows extensive bite marks to the proxi-mal part of the bone. This is the only record of bite marks from this extensive quarryof over 1500 vertebrate elements, making this a most unusual find. Identification ofthe tracemaker is difficult as multiple large theropods are known from the quarry. Fur-thermore, we show that subtly different actions of feeding can potentially result in verydifferent spacing of bite marks making matches to tooth patterns in the jaws of poten-tial bite makers very uncertain. Although identification is uncertain, the tracemaker isclearly not a tyrannosaurid, but the selective scrape feeding pattern seen here is similarto the of tyrannosaurid theropods. This technique may be more widely distributedamong large carnivorous theropods than previously realized. □ Carnivore-consumed,dinosaur, predation, scavenging, trophic interaction.