[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: birds and/or/with dino's

Mike Keesey <keesey@gmail.com> wrote:

> On the other hand, there's a long list of names formerly
> used for
> paraphyletic taxa which are now, at least sometimes, used
> for clades,
> including Synapsida, Therapsida, Cynodontia, Dictyoptera,
> Blattodea,
> Mecoptera, Osteichthyes, Sarcopterygii, Saurischia,
> Theropoda,
> Coelurosauria, etc. Should we have renamed all of those?

In the cases of Cynodontia, Therapsida, Synapsida, Sarcopterygii, and 
Osteichthyes, there was already universal recognition that mammals evolved from 
within these increasingly inclusive groups.  So, converting these traditional 
paraphyletic groups into clades was simply part of the process by which a 
pre-existing Linnaean classification was carried over into phylogenetic 

In the case of Cetartiodactyla, however, the name denotes a novel phylogenetic 
hypothesis: that whales (Cetacea) evolved within the Artiodactyla.  So I think 
that might have been the intent behind the name Cetartiodactyla: to highlight a 
novel phylogenetic position for whales w.r.t "traditional" artiodactyls.

Having said that, not all paraphyletic groups survived the changeover: 
Protozoa, Apterygota, Labyrinthodontia, Proteutheria, Thecodontia (though 
somebody once tried), Condylarthra, etc.  But these tended to be used as 
wastebasket groups, so they're probably best left behind.

As with Cetartiodactyla, coming up with a new name for a traditional dinosaur + 
bird clade (like "Dinoaves") would also have given recognition to this being a 
paradigm shift - in the sense that it overturned a widespread (and erroneous) 
belief that birds and dinosaurs had separate origins.  

> Personally, I find the name "Cetartiodactyla" unnecessary,
> unless
> pan-cetaceans are the sister group to pan-artiodactyls. Why
> not just
> say cetaceans are (or aren't) artiodactyls?

I also think Cetartiodactyla is unnecessary - especially given that recent 
morphology-based phylogenetic analyses (e.g., Thewissen et al., 2007) recover 
whales (Cetacea) outside crown-clade Artiodactyla.

By contrast, molecule-based analyses often recover Cetacea inside Artiodactyla. 
 Personally, I'm skeptical of the entire "Whippomorpha" thing (= whale + hippo 
clade); but that's an entire other issue.