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Temnospondyl carpus and tarsus (free pdf)



Ben Creisler
bcreisler@gmail.com

A new paper in open access:


David Dilkes (2015)
Carpus and tarsus of temnospondyli.
Vertebrate Anatomy Morphology Palaeontology 1(1): 51-87
ISSN 2292-1389
https://ejournals.library.ualberta.ca/index.php/VAMP/article/view/25234

The carpus of Eryops megacephalus and tarsus of Acheloma cumminsi
known from complete and articulated individuals have provided the
standard anatomy of these skeletal regions for temnospondyls. Restudy
of the carpus of Eryops confirms the presence of only four digits, but
refutes evidence for a prepollex, postminimus, and distal carpal 5.
The supposed contact surface on centrale 1 for a prepollex is
reinterpreted as part of the articulation for metacarpal 1 that
includes distal carpal 1. Contrary to previous interpretations, a
notch on the intermedium does not fit against the lateral corner of
the radius. An articular surface on the distal end of the ulna thought
previously to contact an absent postminimus fits against the ulnare.
Preparation of the tarsus of the type specimen of Trematops milleri
(junior synonym of Acheloma cumminsi) and a previously undescribed
crus and pes of Eryops finds no evidence for a pretarsale in either
genus. Centrale 4 of the tarsus shares a similar rectangular shape
with a wide contact for the tibiale among several temnospondyls
whether terrestrial or aquatic. Limited flexibility of the carpus of
Eryops and a strong palmar arch are probably weight-bearing features.
A proximal-distal line of flexibility is present along the tibial side
of the tarsus between the tibiale and centrale 4 and between centrale
2 and centrale 1. A phylogenetic analysis of Temnospondyli including
new characters of the carpus and tarsus reveals considerable
instability, highlighting the significance of Dendrerpeton acadianum,
Balanerpeton woodi, Capetus palustris, and Iberospondylus schultzei.