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RE: Polyphyletic or Paraphyletic?

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Posted by: CKing at Thu Oct 2 15:00:18 2008  [ Report Abuse ] [ Email Message ] [ Show All Posts by CKing ]  
   

>>I recognize reptiles and I use the word all the time. It's an adjective... The word "reptile" means "all amniotes that did not evolve feathers or fur". That's a meaningful definition in certain contexts (like in a pet shop), but it is phylogenetically meaningless and it's subjective.>>

Reptilia is a monophyletic taxon. Reptile is not just "an adjective." It is a noun. It is a basal group, what cladists call a paraphyletic group. The cladists do not like paraphyletic groups because of their dogma. But that is their problem, not ours. They have a problem, but the rest of us don't.

Reptile is not meaningless. It is useful. One can discuss reptilian physiology quite easily because this basal group has more in common with each other physiologically than they do with birds, which some cladists include in their "Reptilia." The cladists' Reptilia is also a taxon, but it is a mess because of the inclusion of birds and the exclusion of such reptilian groups as the synapsids and therapsids. If birds and mammals never evolved, Reptilia would have been a perfectly homogeneous taxon, just like Mammalia or Aves. You are letting cladistic dogma color your views.

>>Do non-venomous snakes comprise a clade?>>

Probably not. That is because some coral snakes may have undergone reversal and become non-venomous.

>>The term is ubiquitous and useful... but it's utter nonsense in the phylogenetic sense. >>

The term non-venomous snakes is not nonsense. Invertebrates is another term that makes sense, not nonsense. If no venomous snake has descendants that have undergone a reversal, then it is possible to have a clade that comprises of all non-venomous snakes. Whether non-venomous snakes form a clade or not is irrelevant. Scientists need to communicate with each other, and they have to refer to groups that are not holophyletic. In fact, they often have to refer to paraphyletic groups. They use terms like non-avian reptiles, but that is less useful than the term reptiles. Even after Romer proposed that Dinosauria is an invalid polyphyletic taxon, he still uses the term dinosaur. So, not every name that systematists use has to refer to a holophyletic group.

>>What does "reptile" mean to you?>>

Reptiles is a clade, a monophyletic group. A clade does not have to include all of the descendants of its common ancestor. Reptile is very meaningful to me. And it is a useful taxon, far more useful than the cladists' reptile. Besides, even the cladists find the name Reptilia indispensable, but their redefined "Reptilia" is not very useful because it excludes some reptiles like the synapsids and therapsids, and it includes some endothermic, highly derived species known collectively as the birds.


   

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