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Feathers are not magical things...



By which I mean, feathers should be treated as the derived anatomical
structures they are, and not some sort of privilaged special feature imbued
with some greater grandeur due to their association with a particular clade
of living creatures.

I bring this up as at least some people on this list (and elsewhere)
consider these features to be somehow "special" so that we treat the study
of their distribution in a different light than, say, cranial pneumaticity
or locomotor modules or what have you.

The simple current situation, whether "Jura" and company like it or not, is
that the current weight of the evidence requires us to assume that all
maniraptorans (minimally) had a feathery body covering.  Full stop.  That is
to say, assuming a) feathers evolved a single time in the history of
vertebrates (the simplest explanation) and b) the known presence of feathers
in birds and only in those theropods which independant phylogenetic analyses
place closer to birds than to other dinosaurian taxa and c) the lack of
evidence to the contrary (i.e., therizinosaur body impressions with scales)
means that as scientists we take the simplest explanation possible.  That
explanation is that feathers evolved in the common ancestor of all
maniraptorans and was passed on to all descendants.  Until such time that we
find direct positive evidence to the contrary, we must assume that
_Velociraptor_ and company were feathered.

This is precisely analogous to the assumption that _Dryptosaurus_ had both a
promaxillary and maxillary fenestra.  We don't have a _Dryptosaurus_ face at
present, but given its position in the phylogeny of theropods it is a member
of a clade which ancestrally possessed these structures.  The simplest
explanation is that it too had these structures.

Does this mean that NO maniraptoran was featherless?  Of course not.
However, in science we choose the simplest explanation, not the explanation
which happens to please us the most or conforms to particular preconceptions
or what have you.  There might well have been featherless maniraptorans.  To
use the example of maxillary fenestration from above, we do know that some
members of the clade which ancestrally possessed these structures
subsequently lost them: the therizinosauroid _Erlikosaurus_ and the
caenagnathid oviraptorosaur _Chirostenotes_, for example.  Had the skulls of
these guys never been found, we would have assumed that that had these
structures.  However, given new information we accept the evidence given.
(The tyrannosaurid integument may be one of the bits which modifies our
assumptions, as might the precise position of compsognathids).

PRESERVATION OF NON-FEATHERS IN LIAONING:
For those people who have access to this site, you can see how scales are
preserved in the Yixian Fm. on Fig. 3 of the Gao et al. paper (the first
paper in the issue) of JVP 20(3):
http://www.bioone.org/bioone/?request=get-toc&issn=0272-4634&volume=020&issu
e=03

Incidentally, I applaud Martin for providing a testable and falsifiable
alternative to the hypothesis that the apparent non-avian Yixian feathers
are feathers.  However, the fact that NONE of the hundreds (thousands) of
non-theropod vertebrates recovered from these quarries shows these elements,
and instead show either nothing or show elements which are integumentary
(hair for mammals, scales for reptiles) rather than some fungal or algal or
dendritic crystalline growth is consistent with the hypothesis that the
feathers are indeed feathers, and reflect the integument of the theropods.

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.

>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).

>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.


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.

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

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.

This highlights the importance of phylogenetics.  We reconstruct phylogenies
not primarily to bug traditional taxonomists, nor because we REALLY like
playing with PAUP*.  The reason reconstructing the historical pattern of
evolution is importance is because that background is necessary for a
testable and reciprocal study of the transformations and adaptations in
Life.

Hope this helps.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
http://www.geol.umd.edu/~tholtz/tholtz.htm
http://www.geol.umd.edu/~jmerck/eltsite
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796