Cursorial Adaptations in the Forelimb of the Giant Short-Faced Bear, <em>Arctodus simus</em>, Revealed by Traditional and 3D Landmark Morphometrics

• Main Author: Lynch, Eric Randally
• Format: Others
• Published: Digital Commons @ East Tennessee State University 2012
• Subjects: Ursidae; Arctodus simus; geometric morphometrics; three-dimensional landmark; locomotion; posture; Earth Sciences; Paleobiology; Physical Sciences and Mathematics
• Online Access: https://dc.etsu.edu/etd/1477; https://dc.etsu.edu/cgi/viewcontent.cgi?article=2670&amp;context=etd

The paleobiology of the Pleistocene North American giant short-faced bear, Arctodus simus, has eluded paleontologists for decades. Its more gracile form has led past researchers to myriad intepretations of the locomotion and feeding ecology of this species. While earlier studies have focused on craniodental morphology and simple postcranial indices, it is forelimb morphology that represents a direct compromise between locomotor and foraging behavior. The study here uses traditional and 3D landmark morphometrics to more completely compare the 3-dimensional shape of the major forelimb elements and their muscle attachment sites between A. simus, extant ursids, and other carnivorans. Results herein agree well with previous studies and provide additional evidence for reduced abductor/adductor and supinator/pronator musculature, more restricted parasagittal motion, increased stride length, and lighter and more packed distal elements. Forelimb skeletal morphology therefore supports the hypothesis that A. simmus represents a bear in the early stages of cursorial evolution.