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Re: Are dinosaurs really reptiles? (2.1)



re: discussions of sister taxa versus linear ancestors.

Yes, of course, those are all uncles. But given the opportunity to
provide closer relatives, why were distant uncles provided?

There was, in most cases (the absence of lepospondyls being the most glaring exception), no opportunity to provide closer relatives.


re: the absence of fossils.

That's one world view. The other is that a good cladistic analysis
will clear things up because enough fossils are known to see the
puzzle for what it is. That's my world view.

Enough are known to provide most of the topology of the tree, yes. But not enough are known that we could watch the evolution of every character.


You are entitled to your own opinion, but not to your own facts. (Sen. Patrick Moynihan)

re: scales and synapsids.

Given that ichthyostegids were scaled like other osteolepids, scales
may have been present on the earliest amniotes, which go back almost
as far. Not the same sort of scales, but then, what the hey.

Nope. These scales are bone plates in the dermis (and present not just in *Ichthyostega* -- there are probably no other "ichthyostegids" --, but also present all over the body in almost all tetrapods except lissamphibians, diadectomorphs and amniotes; I'm not sure about seymouriamorphs); amniotes plesiomorphically retain the ventral scales -- that's what the gastralia are. Sauropsid scales are thickenings of the epidermis, consisting of nothing but keratin. Calling both "scales" is highly misleading.


Westlothiana is in the ingroup. Nests with Paleothyris which has
similar supratemporals and tabulars and lots of other synapomorphies.

Nope (Vallin & Laurin 2004, Ruta & Coates 2007).

re: Diadectomorphs as stem-reptiles.

Way too derived. Way too different from any known pre-amniote.

So they are too derived to be a sister-group?

Don't take it personal, but you have once again confused "ancestor" and "sister-group". NOTHING is too derived to be the sister-group of ANYTHING. That's because everything has the right to accumulate autapomorphies. Diadectomorpha is a branch of its own, it has its own history, during which THINGS HAPPENED.

Hey, you're in good company. People tell me Carroll thinks like you. Nobody else does anymore, though.

re: Spinoaequalis

Excellent! Now you're getting somewhere!  Find more like this one and
you've got your lineage. Credit where credit is due.

What lineage?

re:     Next question: What were the five to ten sister genera
leading up to Herrerrasaurus? No suprageneric taxa please.  DM wrote:
Translation: if we tell you that the fossil record isn't complete
enough for that, you will simply refuse to accept that answer.
Methinks you haven't thought things through.

So, you're telling me out of hundreds of known taxa, you can't find
sister taxa for the most basal dino/dinomorph? Where do dinos come from?
You can start with Euparkeria. Then what?

We can arrange all these taxa in a tree. It just so happens that some of the side branches have diversified on their own, forming a suprageneric taxon. They are there, dude. You can't deny them.


If our sampling of the fossil record were 10 times denser, we'd probably have a few individual species branching off along the internode between Saurischia and Herrerasauridae, which seems to be what you were asking for (it's always difficult to figure out what you mean). But we don't.