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RE: Tyrannosaurids, skippy, and sterna



Steve Brusatte wrote on 07/09/2002 regarding the influence of the juvenile status of Scipionyx in cladistic analysises:

> Ricqles, Mateus, Antunes, and Taquet have shown that bone-specific anatomical details are actually present
> in embryos that are most likely _Lourinhanosaurus_.
> Many characters are most definitely affected by ontogeny, but not all.

That's the problem I see with juveniles in cladistic analysises. Juveniles may show a mixture of already developed derived and basal characters. Some basal characters may be due to the fact, that they are being transformed into derived characters late(r) in ontogeny.

If I understand cladistics correctly this means that juveniles may find a more basal phylogenetic position due to the lack of some derived characters.

Of course there's even another possibility. Evolution works also by keeping juvenile characters in adults. This too would influence the phylogenetic position of juveniles found in cladistic analysises.

> we must not use immaturity as a sweeping "excuse."

Not "sweeping excuse" but reasonable doubts. We have to keep this in mind if we try to assess the validity of the phylogenetic position of Scipionyx found in a cladistic analysis.

Cheers


Heinz Peter Bredow