[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: [Feathers are not magical things...]



"Thomas R. Holtz, Jr." <tholtz@geol.umd.edu> wrote:

> On the matter of preservation, Jura writes:
> >By exact same location I mean that _Beipiaosaurus_ _Sinornithosaurus_ &
> >_Sinosauropteryx_ all come from the exact same location. Each one's
> location
> >description reads like a carbon copy of the other. That all of a sudden we
> >would find so many "fuzzy" theropods from so many different clades and all
> >coming from the same locality (outside Beipiao city seemed to be the
> popular
> >description) comes off, to me as rather suspicious. I wouldnt' mind it if
> it
> >were only a few dinosaurs from the same genera or so, but to have a
> >theriznosaur, dromaeosaur & compsognathid all from the same place,
>
> This is not at all uncommon (actually, it's kind of Vert Taphonomy 101
> stuff): some localities result in the accumulation of a sizable
> representative of the local fauna.  And these are all relatively little
> guys: how about places like the Felch Quarry 1 where a single bedding plane
> contained excellent (some nearly complete) fossils of _Stegosaurus_,
> _Allosaurus_, _Ceratosaurus_, _Diplodocus_, and smaller or more fragmentary
> specimens of mammals, fish, _Brachiosaurus_, and _Camarasaurus_?  This site
> (see Evenoff & Carpenter, 1998. Modern Geology 22: 145-169 for more
details)
> is probably a non-catastrophic mass mortality site, which results in many
> different members of the ecosystem being preserved together in very close
> proximity.
+++++++++++++++++++++++++++

Yes, but none of them was found with new and controversial (i.e. first time
ever) "dino-fuzz." If they were, I'd be just as suspicious (if not more). We
never found this type of integument before and now all of a sudden we have 3
rather distantly related animals with the same integument. That's what made me
think contamination first, integument second.

__________________________


> >with the
> >same covering (not placed anatomically;
>
> Don't know what you mean "not placed anatomically": the integuement for most
of these specimens is clearly in position relative to the body (pointed side
pointing towards the bone, frayed or broad side towards the outside).
>
+++++++++++++++++++++++++++++

If you read the papers on _Sinosauropteryx_ _Beipiaosaurus_ or
_Sinornithosaurus_ they all state how the "fuzz" is not placed in an
anatomical position on the body. The stuff is either pointing away from the
body or at an awkward angle or even not articulated with the body. Falling on
some Mesozoic plant during death (or floating into it) could preserve just
such a formation.

Note: This is not to say that I think "fuzz" needs to be placed in the
position that it was in real life. Only that if this was contamination we
wouldn't expect to find it placed in a "natural" position, but rather strewn
about; which these three had.

______________________________


> >mind you) seems a little dubious.
>
> Actually, the similar preservation isn't that weird: that's why we call
such
> sites Konservat-Lagersta:tten.  Given a particular rare set of depositional
> and sedimentological circumstances, it is possible to preserve some
features
> that otherwise might be lost in fossilization.  The fact that only the
> theropods (including birds) show the feather structures, while other taxa
> from the exact same quarries and bedding planes do not (and instead show
> either nothing or show impressions and carbonizations of integument
> consistent with the known condition in those clades (scales on fish, scales
> on non-theropod reptiles, fur on mammals, etc.)) is wholly consistent with
> the hypothesis that the Yixian Fm. is preserving records of integument
> rather than some non-integumentary growth.

++++++++++++++++++++++++

I can agree with that; though I'd still be more comfortable reading on some of
these other finds.

What journal was the Liaoning _Psittacosaurus_ published in?

________________________

> TYPOLOGY:
> Something that seems to come out in "Jura"'s posts, and as well in
> discussions with Ruben and others, is a sort of Platonic typology or
> idealism: that is, that there is a dinosaur "kind" and an avian "kind" and
that never the twain shall meet.  Thus, since we have lots of dinosaurs with
scales, there for it is an aspect of the dinosaur "type" to have scales.

+++++++++++++++++++++

I can see the slight implication this appears to be making and I can't say I
find it all that "fun.."

I won't lie; classification comes before cladistics in my book and Aves &
Dinosauria will always remain separate. It doesn't mean that I don't think
birds evolved from dinosaurs. I just don't think we should call them
dinosaurs. I'm no different with eusuchians and rauisuchians or mammals and
therapsids.

Anyway I'll stop there before this becomes another "non-serpentean lacertids"
thread.

I do think that scales are the default condition for all dinosaurs, and even
all reptiles (or at least up until rhynchosaurs, which we have scale
impressions from). I'd almost go so far to say that scales are a synapomorphy
of Reptilia, if I could find enough fossil scale impressions to prove one way
or the other. We have dinosaurs without scales (or rather with replacements
for scales) and we even have scale-less snakes (bred that way). Neither makes
them any less reptilian, but both are small compared to the rest and are the
exceptions rather than the "rule."

______________________________

>
> However, a certain British publication back in 1859 (okay, and some before
and a lot since)

+++++++++++++++++++++

Heh, another "fun" reference >:)

_____________________


 have long ago put paid to the Platonic concept of "kinds" or "types" or
"ideals".  Evolution happens, and one type changes into another, until the
boundaries (from a morphological standpoint) are blurred into non-existence.
Saying that most dinosaurs are scaled, so that we should treat all dinosaurs
as scaled, ignores the paleontological evidence and the fact of evolution.

+++++++++++++++++++++++

Did I ever say that? Am I that bad at getting my point across?

All I said was that I consider all dinosaurs to be scaly by default (i.e.
dinosaurs, in all likelihood, started off with scales and didn't start off
naked skinned or furry) and that positive evidence to the contrary (such as
naked skin patches or feathers) is needed to make dinosaurs anything other
than scaly. I didn't say that all dinosaurs were scaly; only that this is the
safest assumption to make with the evidence we have, except for (perhaps)
drawing skeletons of the animals only.

_________________________


> Jura is quite correct, however, in pointing out that saying birds are
> dinosaurs, therefore all dinosaurs had avian traits, is equally
> inappropriate.  This ALSO ignores evolution.  Extrapolations of traits >
known in birds but not other reptiles down into taxa outside of        >
Neornithes is inappropriate without some other evidentiary support (i.e.,
maniraptorans preserved in brooding position).  Not all neornithine traits are
ancestral, and evolution continued after birds split from other theropods.
Making all dinosaurs into birds is no more appropriate than (and analagous to)
extrapolating characters of Ceratopsidae or Ankylosauridae to the base of
Dinosauria.

+++++++++++++++++++

True enough (though I'm not so sure that brooding is found only in birds &
dinos) and I certainly don't deny that _Caudipteryx_ & _Protarchaeopteryx_ had
feathers and are still dinos (well, not anymore with _P.robusta_ :). I'm
certainly wary, though, of placing feathers on any dino that hasn't been found
with them (IOW keep your feathery allosaurs) and still think scales are a
safer assumption (or skeletons for the very cautious :).


Jura - who doesn't consider feathers, or scales, to be magical, but is
indecisive about turtles :)

P.S. all "Fun" references in this post were purely the result of my cynical
humour and shouldn't be considered anything more than that.

The Reptipage: A site devoted to the study of and education on, the reptilia:

http://reptilis.net