Contrasting developmental trajectories in the earliest known tetrapod forelimbs

• Ichthyostega and Acanthostega are the earliest tetrapods known from multiple near-complete skeletons, with Acanthostega generally considered the more primitive. New material indicates differing ontogenetic trajectories for their forelimbs: In Ichthyostega, the   pattern of muscle attachment processes on small humeri (upper armbones) resembles that in "fish" members of the tetrapod stem group such as Tiktaalik, whereas large humeri approach (but fail to attain) the tetrapod crown-group condition; in Acanthostega, both small and large humeri exhibit the crown-group pattern. We infer that Ichthyostega   underwent greater locomotory terrestrialization during ontogeny. The newly recognized primitive characteristics also suggest that Ichthyostega could be phylogenetically more basal than Acanthostega.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

Biology

Biologi

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)