Boyer diss 2009 1046..

457) and hallux, suggested to Beard that plesiadapids were arborealists. He contrasted
some of their forearm and phalangeal characters with those of extant dermopterans and
extinct paromomyid plesiadapiforms, inferring that plesiadapids “spent most of their time
in above branch arboreal postures” (p. 458).
Beard later published some of his dissertation findings. Figure 1 in Beard (1990)
shows the articulated metacarpals of digits I-III of N. intermedius USNM 442229.
Godinot and Beard (1991) presented extensive descriptions and comparisons of fossil
primate hands. In it they figured (p. 311, fig. 1; p. 313, fig. 2) a composite digit ray of P.
tricuspidens using MNHN R 5305 (MC II or MC V – the authors appear to have
disagreed on the designation), MNHN R 5303 (proximal phalanx), MNHN R 5341
(intermediate phalanx) and MNHN R 5361 (distal phalanx). They interpreted the
metacarpophalangeal joint as having a capacity for extreme dorsiflexion, the proximal
interphalangeal joint as having greater capacity in palmarflexion and limited dorsiflexion,
and the distal interphalangeal joint as having a neutral range of flexibility. They
suggested that the large flexor tubercle on the distal phalanx indicates a robust tendon of
flexor digitorum profundus. Godinot and Beard also noted that relatively dorsoventrally
deep phalanges would have resisted forces imposed by powerful contraction of this
muscle. Thus they concluded that P. tricuspidens could have forcefully driven its claws
into substrates such as tree branches and clung to them. They compared the morphology
of P. tricuspidens to that of Daubentonia, and they compared what they viewed as likely
habitual digital postures for P. tricuspidens to those used by lorisines in pronograde and
orthograde postures on various substrates.
270