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Re: Four-toed theropods
George Olshevsky wrote:
> If the well-known theropod groups are indeed descendants of groups of small,
> arboreal, narrow-metatarsal dino-birds in which the hallux was large and
> retroverted (as I imagine), then the tetradactyl theropod foot could easily
> be an intermediate evolutionary stage between the large-retroverted-hallux
> foot and the typical theropod foot, in which the reduced hallux points
> medially inward and no longer contacts the substrate. The rarity of
> tetradactyl theropods may indicate the rapidity of this evolutionary trend.
Wouln't what you are describing be a Triassic form? The footprints
in question come from the Jurassic and Cretaceous. The existence of such
a form that late would be unlikely if such a hypothetical for was really
rare due to rapid evolution into true theropods.