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Re: "Dinosaurs Died Within Hours After Asteroid Hit Earth..."




David Marjanovic wrote:

This one... there are only 2 possibilities: either it's a loriid, means, it
belongs to a _part_ of the crown group of Psittaciformes, or it's not a
psittaciform.

Correct me if I'm wrong, but I do not believe that modern avian "orders" (e.g., Psittaciformes, Galliformes, Sphenisciformes) are restricted by definition to their respective crown groups. Fossil taxa (e.g., Gallinuloididae) have been referred to the Galliformes as stem taxa that do not belong to the crown group. Further, here's what Clarke et al. (2003) have to say for the penguin clade:


" ?Pansphenisciformes? is used here as a name for all taxa more closely related to extant penguins than to any other extant avian taxa. ?Sphenisciformes? is suggested as a name for all parts of this lineage with a loss of aerial flight homologous with that of extant penguins. These definitions are deliberately not formalized pending recommendation of the PhyloCode regarding the proposed use of ?pan? as a prefix in all stem clade names (Gauthier and de Queiroz, 2001 ) and to allow penguin specialists to debate appropriate definitions for these names prior to the start date of the PhyloCode (Cantino and de Queiroz, 2000 ). As all extant penguins have consistently been placed in the ?family? Spheniscidae, it is also recommended that the name ?Spheniscidae? be formally applied to the clade comprised of the most recent common ancestor of all extant penguins and all of its descendants. "

Thus, Clarke et al. (2003) propose a stem-based definition for Pansphenisciformes, an apomorphy-based definition for Sphenisciformes, and a node-based definition for Spheniscidae (= crown group).


Tim

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