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Non-serpentine lacertids (was RE:WHAT'S GOING ON?)



tmk@dinosauricon.com writes:

> I agree with this up to a point. While, yes we should look at things >from
an evolutionary perspective, going around calling tyrannosaurs and
>ceratopians "non-avian dinosaurs" is both confusing and unwarranted.

You *could* just call them "dinosaurs".
 
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I'd love to do that, but if I were to ask Mark Norell what he thought
dinosaurs might sound like, I have a feeling that he would start giving me a
list of songbirds.


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> Now, cladistically snakes are lizards, just like birds are dinosaurs,

Not really -- "lizard" isn't a formal taxon, and even Lacertilia hasn't
been incorporated into phylogenetic taxonomy, TMK. (The equivalent would
be non-serpentean [or is it ophidian?] Lepidosauria.) No formal taxonomic
system has anything to say about what is a "lizard" and what isn't.


>Dinosauria, however, is a formal taxon, and as such has formal usage.

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But isn't _Sphenodon_ also a non-serpentean lepidosaur? That's why I tried to
keep it narrower.

As I mentioned in a previous post, Harry W. Greene did use lacertilia in a PT
scenario when explaining snake evolution. But then that was a book (a good
book) and not a technical paper.

Regardless, the point I'm making is that snakes evolved from lacertilian
(saurian) stock, but rather than calling them modified saurians or what not,
we have given them a separate name which makes distinguishing between them a
lot easier. 

Now admittedly these names came about in a more species static era, but even
in today's evolving world, it still is helpful to have names that distinguish
different groups of creatures. 

And yes it is pidgeon holing, but this part only comes in when trying to keep
up our arbitrary boundaries while explaining an evolutionary history, which of
course makes no sense to do.

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> To summarize,  a sauropod is a dinosaur, ankylosaurs are dinosaurs,

Certainly.

> psittaciformes are birds and so are falconiformes.

And they are also Dinosauria, using the phylogenetic definition.

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I'm not doubting their evolutionary roots, but I do have my reservations about
calling such obvious birds, dinosaurs (the same kind of reservations that I
would have when calling a python a saurian or mosasaur).

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> _Caudipteryx_ and _Rahonavis_ are non-avian and/or avian theropods (or
>better yet, non-avian/avian maniraptorans).

_Caudipteryx_ is probably related to Oviraptorosauria (non-avian) and
_Rahonavis_ is a basal avialan, possibly a basal avian, both within
Maniraptora.
 
> A varanid is a lizard, an iguana is a lizard. Viperids are snakes and so
>are colubrids. 

"Lizard" and "snake" are wholly vernacular terms.

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And "bird" isn't?

All pedantry aside, I hope you see my point. When there is no doubt as to what
category the animal belongs to, then use the name of said category. When the
animal can't be easily pidgeon holed, then use the non-whatever names for
them.

I mean does _Brachiosaurus_ really have to be called a non-avian dinosaur?

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Personally, I think the term "non-avian dinosaur" is overused, but for
other reasons. If traditional Dinosauria was not a desirable taxon (and I
don't consider that it was) why continue to refer to it all the time?

Indeed, most times I see the term, people are really referring to
"Mesozoic dinosaur" (in discussions of extinction) or "non-neornithean
dinosaur" (in discussions of extinction and of features that are only
observable in extant taxa). I went though my entire site about a year ago
and found this to be the case most of the time.

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Exactly, for the most part the term is just extra baggage.

Jura 

Jurassosaurus's Reptipage: A page devoted to the study of the reptilia:

http://reptilis.webjump.com

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