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Re: Archaeopteryx teeth, claws and their TV viewing habits



In a message dated 95-12-16 23:52:25 EST, jpoling@infinet.com (Jeff Poling)
writes:

>   I'm curious about some statments:
>
>>1. Archaeopteryx had feathers identical to those of modern birds, whereas
>>theropods had none
>
>   I thought I read/saw somewhere that Archaeopteryx feathers lacked a
>feature in modern birds that allows the feathers to lock with each of its
>neighbors.  Anybody know if this is true?  (We need not address whether
>theropods in general had feathers.  I know what to say about that.)

The feathers look very birdlike to me. I don't know about interlocking,
however--and whether you could even tell from the traces as preserved.

>>2. Archaeopteryx had a hypertrophied furcula (fused clavicles);theropods do
>>not have one
>
>   The modifier "hypertrophied" throws me a bit.  Is this modifier
>necessary, or would all furculae be considered "hypertrophied?"  I'm curious
>if the use of the word "hypertrophied" would cause problems in trying to use
>the furculae of Oviraptors and Allosaurs as a rebuttal.

The _Archaeopteryx_ furcula is very similar in shape and relative proportions
to those of _Longisquama_, _Oviraptor_, _Allosaurus_, and the unnamed gracile
Morrison theropod. It is much thicker and more robust than furculae in modern
birds, and probably was nowhere near as springy. Also, in all theropods in
which it is known, it lacks the hypocleidium (the "tab" on the wishbone)
present in modern birds--although the _Oviraptor_ furcula seems to have a
trace of one. The evident robustness is probably the source of the
description "hypertrophied."

>>3. Manus claws of Archaeopteryx differ markedly from those of predatory
>>dinosaurs (Feduccia, 1993)
>
>   Anybody know if this is true?  If so, does it really matter?  I thought
>there were all sorts of different claws in the Dinosauria.  I'm also curious
>as to how similar the claws are to Dromaeosaurid claws.

Not particularly. The manus of _Archaeopteryx_ is practically
indistinguishable from the manus of dromaeosaurids in terms of the relative
proportions of its bones. Most remarkable are phalanges 3 and 4 of digit
3--the two short ones at the base of that digit--which show up in all kinds
of maniraptoran theropods, especially dromaeosaurids. This is such a telling
character that several birds-are-not-even-close-to-dinosaurs types have tried
to argue that there was really only one phalanx, but it is broken in half in
all known specimens of _Archaeopteryx_(!).

>>4. Archaeopteryx had a fully reversed hallux, the large rear toe, with a
>>strongly curved claw on the ungual phalanx, which is typical of modern
>>perching birds and unlike any known theropod dinosaur (Feduccia, 1993)

In cursorial theropods, the retroverted hallux was vestigial (BCF theory
here), although it always articulated toward the back of metatarsal II. As a
vestigial digit, it is pretty much irrelevant to the discussion, since it can
assume any position in the foot that is useful to the animal. In BADD theory,
the hallux is considered "partly retroverted" in most theropods, sort of "on
the way" to becoming fully retroverted. (And how would the hallux know that
it was going to be useful fully retroverted? This is a great big hole in BADD
theory that the birds-are-not-even-close-to-dinosaurs types keep trying to
climb through.)

>   I don't think we need to rehash all of this, but I would like to know
>what "ungual phalanx" means, and whether other dinosaurs had them.

The ungual phalanx is the first phalanx of any digit, manual or pedal. Some
workers don't consider it an ungual unless it is claw-shaped (e.g, not a
hoof), but I'm not sure whether this usage is universal.

>>5. Although Archaeopteryx had teeth, the crowns of its teeth were
>>unserrated, the waist present, the root expanded, and the tooth replacement
>>resorption pit oval to circular. On the other hand, in the reptiles
>>Pseudosuchia and Coelurosauria, the crowns were serrated, the waist absent,
>>the root straight and unexpended, and tooth replacement resorption pit
>>elongate (Brown 1987, p. 78)
>
>   I have no bloody idea what any of this means.  Comments?  Did all
>dinosaurs have the same kind of tooth replacement mechanism, thus making
>this important/unimportant?

All this says is that _Archaeopteryx_ teeth were differently shaped from the
usual theropod teeth, with a slightly differently shaped tooth replacement
resorption pit, etc. Big deal. Tooth shape is quite variable among animals
that make their living with their teeth. Don't forget that _Archaeopteryx_
teeth are teeny--only a few mm tall--and a lot of tooth-shape evolution must
take place when you go from small animals to large animals (BCF theory) or
from large animals to small animals (BADD theory).

Tooth replacement among _most_ theropods was pretty much the same; but then
there were those toothless forms and those forms with little tiny teeth like
_Pelecanimimus_, in which the pattern must have been different. Among
dinosaurs in general, the phytodinosaurs exhibit considerable variation in
their tooth replacement patterns, from very little or none (in
heterodontosaurids) to multi-tiered tooth batteries (in ceratopians and
duckbilled dinosaurs).