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Re: Land of the Lost review-spoiler?
2009/6/4, David Marjanovic <firstname.lastname@example.org>:
> In birds, the beak means that lips _cannot_ be present. Lip muscles are thus
> _not_ "absent", but _"inapplicable"_ in birds, means, _unknown_ for the
> purposes of phylogenetic bracketing. So, the EPB for nonavian dinosaurs
> consists of the crocodiles and the lepidosaurs; the birds must be ignored.
> Crocodiles lack lips.
May be as you say, unless lack of lip muscles in birds is not
correlated with bill (in case lip muscles were lost before the beak
appeared, which is a possibility).
One can hypothesize that beaks may be easier to appear in taxa where
the epidermis is more thighly bound to the supporting bone, and those
are the taxa with less mass of tissue between epidermis and bone (I
suppose less muscle).