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re: pterosaurs and dinosaurs

David Peters (via Ekaterina A.) wrote:

> Pterosaurs are derived prolacertiforms, closest to
> Cosesaurus, Sharovipteryx and Longisquama, [snip]
> Also note that the caudofemoral anchors are all greatly reduced
> producing an attenuated tail with implications for complete elimination 
> of the retractor muscles of the femur and default replacement by the 
> rotator muscles of the pelvis. You won't find that in dinos. 

Not in basal dinos, anyway - which is Dr Peters' point.  However, caudal
attenuation and the decoupling of the base of tail from the femoral
musculature are regarded as maniraptoran characters (Gatesy, 1990 etc).
This 'liberated' the theropod tail from its ancestral role in stride
generation, allowing it take on new functions - including forming part of
the avian flight apparatus in coordination with the wings.  The implication
in Prolacertiformes is that a similar process occurred in the ancestors of

Exactly *why* the tail of maniraptorans became detached from the hindlinb
locomotor module is unclear.  Are there any proposed reasons why this might
have occurred in prolacertiforms?