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Triassic archosaur bipedality and cursoriality

From: Ben Creisler

New in Paleobiology:

Tai Kubo  and Mugino O. Kubo (2012)
Associated evolution of bipedality and cursoriality among Triassic
archosaurs: a phylogenetically controlled evaluation.
Paleobiology 38(3):474-485
doi: http://dx.doi.org/10.1666/11015.1

Supplementary materials deposited at Dryad: doi: 10.5061/dryad.t0d447t7

Bipedalism evolved more than twice among archosaurs, and it is a
characteristic of basal dinosaurs and a prerequisite for avian flight.
Nevertheless, the reasons for the evolution of bipedalism among
archosaurs have barely been investigated. Comparative analysis using
phylogenetically independent contrasts showed a significant
correlation between bipedality (relative length of forelimb) and
cursoriality (relative length of metatarsal III) among Triassic
archosaurs. This result indicates that, among Triassic archosaurs,
bipeds could run faster than quadrupeds. Bipedalism is probably an
adaptation for cursoriality among archosaurs, which may explain why
bipedalism evolved convergently in the crocodilian and bird lineages.
This result also indicates that the means of acquiring cursoriality
may differ between archosaurs and mammals.