Does Archae's ancestry stem from the Ornithopoda, Pseudosuchia, theropoda, or Sphenosuchidae groups? There is much discussion and debate on this, some circles feeling one or more of the groups have been scientifically eliminated long ago, while others still claim validity.
Although it's unlikely we will ever be absolutely sure, the generally held conclusion is that Archy descended from a theropod. From
Archaeopteryx's Ancestry:
quote:
Apart from the theropod ancestry, there have been three other suggested ancestral groups for Archae, the Ornithopoda, the Pseudosuchia and the Sphenosuchidae.
The Ornithopod ancestry theory was based on the tasus and pelvis in various dinosaurs which were supposed to approach the condition found in birds. However, most of the taxa used in the original theory in 1883-4 are now known to be saurischian rather than ornithischian. Whilst there was a tendency for the reduction of the hallux (big toe) in some ornithischians, it was never apparently opposable as it is in Archae. It was suggested that Archae had a pelvis which was very ornithischian, however, recent work has shown that this is an artifact of post mortem movement of elements of the pelvic region and there is very little similarity to the ornithischian pelvis. With this, the link between ornithischians and Archae disappears and so it is now thought that there is no link between them.
It was suggested that birds arose from an almost unknown Middle or Late Triassic reptile group, the Sphenosuchidae (Walker 1972, 1974), which also gave rise to the crocodiles. The theory is based on a single specimen of Sphenosuchus. However, in their general configurations, neither the skull and jaws, nor the scapulo-coracoid of Sphenosuchus is remotely suggestive of affinities with Archae (Ostrom 1976). More recently, the main proponent of the crocodile-bird hypothesis has stated that the hypothesis "has become so tenuous that it is very difficult to sustain." (Walker 1985, p. 133)
The pseudosuchian link was very much favoured earlier this century. However this was, by and large, based on Heilmann's reconstruction of the Berlin specimen, which has since proven to be inaccurate. According to Ostrom (1976 p. 159):
quote:
There are very few anatomical resemblances between Archaeopteryx and any pseudosuchian. In fact, only in one feature does any pseudosuchian resemble Archaeopteryx more closely than does any theropod, this being the tibia to femur ratio in Scleromochlus, Lagosuchus and Lagerpeton, where the tibia is from 20% to 30% longer than the femur. Amongst theropods, only in struthiomimids, Compsognathus, Microvenator and Deinonychus is the tibia longer than the femur but by only 10% to 15%. In all other features, the closest resemblance to the morphology preserved in Archaeopteryx is found in coelurosaurian theropods." [original emphasis]
This is hardly a "hot debate". I notice that you didn't actually present any references for your claim, you just wrote "The web is FULL (as you probably already know) of info about this topic" and a few more unsupported assertions. The Web is indeed full of info about this topic, but that proves nothing; only references to the scientific litreature or Web pages with sumamries and references to the scientific literature, such as I posted, are relevant to establishing the existence or nonexistance of "hot debate in scientific circles".
Shall I presume that you are abandoning your claim of a hot debate, since you have presented no evidence for it and have not attempted to present any evidence for it?
Your other questions are interesting, but I don't know the answers for them off the top of my head; start with the link I posted. Your questions about Archy are irrelevant to your claim that there is scientific debate.
But I must say that leaving out a creationist viewpoint is like the democratic party asking that the republican viewpoint be left out of senate debates
No, it's sort of like leaving the raccoon viewpoint out of Senate debates; it's just irrelevant. Creationists have abandoned science in their refusal to question all their preconceptions and their insistence on ignoring, distorting, and making up evidence to fit their preconceptions. Creationists have long since given up on trying to actually establish themselves as scientists; AIG and ICR and the like are, with a few rare exceptions, just making a good-looking storefront for the faithful. Creationists have failed in all their attempts to legislate themselves as science, and the courts have repeatedly found that what is proffered as "creation science" is not scientific by any definition.
Creationists can be scientists; let them start actually practising science and they will be welcome in thbe scientific comunity.
™ Version 4.2