Boyer diss 2009 1046..

matches the opposing facet on the triquetrum described above. Furthermore, it is nearly
identical to the pisiform described for N. intermedius (Beard, 1989) although much larger
(Table 4.8). When articulated with the rest of the proximal carpal row, the pisiform
tubercle projects roughly parallel to the proximal radius articular surface of the other
carpals (Fig. 4.10) and at almost 90° to the scaphoid tubercle (i.e, if the pisiform is
considered to project ventrally, then the scaphoid tubercle can be described as projecting
distally). The triquetrum facet is reciprocally saddle-shaped compared to its
corresponding facet on the triquetrum. This facet is dorsally and slightly distally
oriented. The ulna facet is pyriform and gently concave. It is proximally and slightly
dorsally oriented. The pisiform has a distinct shaft that is narrower than the proximal
end. The distal end for attachment of the flexor carpi ulnaris, hypothenar muscles and
pisohamate ligament (Haines, 1955; George, 1977) is swollen proximodistally relative to
the shaft.
Function.—A pisiform that projects at 90° from the scaphoid tubercle suggests a
habitually dorsiflexed hand and possibly pronograde postures (Fig. 4.10). The large size
of the pisiform suggests a capacity for powerful ventriflexion (using flexor carpi ulnaris)
from an initially dorsiflexed posture, and is also suggestive of pronograde postures.
Comparison.—P. cookei is nearly identical to N. intermedius in its pisiform
morphology. The only notable difference is a shorter shaft relative to facet size and shaft
diameter in N. intermedius (Table 4.8: BSV and SSV). If these animals utilized similar
postures and behaviors in life, a larger pisiform might have been required to maintain
equivalent abilities in ventriflexion in the absolutely larger animal (P. cookei) because it
would have had a proportionally greater mass.
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