Contrasting Developmental Trajectories in the Earliest Known Tetrapod Forelimbs

@article{Callier2009ContrastingDT,
  title={Contrasting Developmental Trajectories in the Earliest Known Tetrapod Forelimbs},
  author={Viviane Callier and Jennifer Alice Clack and Per Erik Ahlberg},
  journal={Science},
  year={2009},
  volume={324},
  pages={364 - 367}
}
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 arm bones) 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… 

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