Re: The Two Principal Dinosaur Clades Defined

[Dinogeorge@aol.com]

In a message dated 96-01-20 03:22:57 EST, jpoling@infinet.com (Jeff Poling)
writes:

>  So the problem we have here is one of semantics?  The first dinosaurs
>were small and arboreal that became large and cursorial in your theory,
>rather than the mainstream theory of the first dinosaurs being large and
>cursorial that evolved small and arboreal forms?

Right. But it's not _just_ semantics. BADD theory says dinosaurs evolved from
bipedal cursorial non-dinosaurian archosaurs, and the forelimbs later turned
into wings. BCF theory says dinosaurs evolved _as_ scansorial arboreal (or at
least acronomic) archosaurs, some of whose descendants became cursorial
bipeds while others remained acronomic and evolved into birds.

>   If that is true, then BADD and BCF are not that far apart.  If I read you
>correctly, the first dinosaurs weren't birds we would recognize today, they
>were animals that people would recognize as dinosaurs (bipedal, erect
>posture, S shaped neck, long tail, 2 - 3 fingered hand, three toed foot plus
>hallux) if they saw them.  You're simply defining them as birds.

Definitely not a 2-3-fingered hand. The first dinosaurs had all five fingers
and all five toes. They were small, lightly built animals the size of
canaries or crows (at their largest). Their posture would not necessarily
have been fully erect, but it would have been close. The forelimbs would have
been long, with large manus eminently useful for grasping and climbing,
almost as long as the hind limbs. I'm not sure about an S-shaped neck, but
the cervicals would have been well differentiated from the dorsals, as seen
also in pterosaurs and _Megalancosaurus_. In fact, although _Megalancosaurus_
and its relatives were highly derived arboreal climbers, they possessed
certain skeletal features very much like what I would expect in a dinosaurian
precursor.

>   I submit that may be a mistake.  The idea of "birds came first" doesn't
>jive with me because I like the idea of birds descending from theropod
>dinosaurs.  As far as I can tell, your BCF theory has birds evolving from
>animals we would recognize as dinosaurs ... you've simply changed the names
>to confuse the innocent.

The dinosaur groups presently called theropods are related to the dino-birds
in exactly the same way that the large Cenozoic cursorial predatory birds are
related to modern (or avialan) birds. I'm not trying to confuse anybody; I'm
trying to clarify the relationships. Even if you restrict your concept of
birds to just the avialan birds, however, _still_ they did not descend from
any of the known birdlike theropods.

>   Perhaps if you used an acronym such as DDAB (Dinosaurs Descended from
>Arboreal Beginnings, an acronym that is BADD backwards and appropriate
>since, as stated in my first paragraph, the order of descent is backward
>from that of BADD) might engender less hostility, and might actually be
>clearer in describing your theories.

The acronyms aren't that important. But it may ultimately do the mainstream
paleontologists and especially the more evangelistic cladists some good to
have someone calling their ideas BADD for a change.