Aspects of the structure and functional anatomy of the Middle Triassic cynodont Luangwa

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Abstract

The study concerns an incomplete skull and postcranial skeleton of the traversodontid cynodont Luangwa drysdalli Brink, from the Middle Triassic Ntawere Formation of Zambia. The incisor teeth had cutting edges maintained by tooth abrasion, and the post-canines functioned more by a puncture-crushing mechanism than by shearing. The jaw muscles, in conjunction with the teeth, were arranged to avoid stresses at the jaw articulation.

Both the region of the orbit, and the braincase show certain tendencies towards mammalian structure.

The forelimb operated in a primitive, sprawling fashion. The equivalent of the therian supraspinatus muscle had evolved, but not the infraspinatus. The hindlimb was more or less erect, and the hip musculature was very close to mammalian. Expanded costal plates were still present on the posterior thoracic and lumbar ribs, and functioned to maintain the vertebral column virtually rigid.

Ancillary