THE UNIVERSITY OF CALGARY Eric Snively A ... - Ohio University

The distal intermetatarsal articulation surfaces of MT III are not symmetrical
about the edge of the plantar constridian (Figure 2.8). The articular surface of
MT III with MT IV displays a wmpound cunrature. It is slightiy concave, and
twists from a nearly sagittal orientation distally to a more mediolaterally
transverse orientation proximally. Compared with the MT II facet, the surface of
MT III articulating with MT IV is relatively vertical.
In contrast, most of the faœt contacting MT II inclines proximolaterally
towards the midsagittal axis of the metatarsal. This is reflected in antenor view by
a high media1 curvature adjacent to MT II (Figure 2.7). The distal surface of MT III
that articulates with MT II consists mostly of a broad surface in one plane, which
twists slightly when the metatarsal approaches its narrowest width. The distal
surface adjacent to MT II is more rugose than that articulating with MT IV,
especially in Tyrannosaurus EX.
Proximal to these articular facets with MT II and MT IV, MT III narrows to a
uniforrn width in anterior view (Figure 2.7). This constitutes the gracile, proximally
constricted region of the metatarsal, and continues for about 30% of the
element's length. The third metatarsal continues to display plantar constriction
for most of this portion of the shaft (Figure 2.8).
c) Region of proximal articulation (Figures 2.7 and 2.8). The third metatarsal
expands again to articulate proximally with MT II and MT IV. As in AIlosaums
fragilis and Ornitholestes hemani, the proximal portion of the tyrannosaurid MT
III that articulates with MT Il and MT IV is hooked in cross section. From the
plantar to the flexor surfaces, the rnetatarsal is first sagittally oriented, and then