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I've spent a few hours in the special
libraries of the university institutes for biology and geosciences. There I've
dug up 2 interesting papers which probably aren't news to many list members,
but they are important for my own article, the discussion on which I'll try
to open tomorrow*:
Gerard Gierlinski (with an
accent on the n, like Maryanska): Feather-like Impressions in a Theropod
Resting Trace from the Lower Jurassic of Massachusetts, 179 -- 184,
in
Michael Morales (ed.):
The Continental Jurassic, Museum of Northern Arizona Bulletin
60, 1996
"ABSTRACT: Restudy
of a well known [since 1858!!!] example of a dinosaur resting trace, the famous
Hitchcock collection trophy catalogued as AC 1/7, led to a significant, hitherto
unreported observation. The trace of the Early Jurassic squatting theropod from
Massachusetts contains the pubic-abdominal imprint with the hair- or
feather-like impressions. These structures strongly resemble those left by the
hairy or feathered body parts of recent mammals or birds, especially their
so-called furry feathers."
The specimen is classified as
Eubrontes minusculus. It consists of the impression of both whole feet
(with very short 1st toes), the deep heart-shaped impression of the ischiadic
foot (so coelurosaurs are ruled out as the trackmaker, AFAIK) well behind the
footprints, and those interesting impressions next to the right foot that were
made by the belly. The trackmaker was sitting asymmetrically, with the pubic
foot maybe resting on the right foot, as there is no impression of
it.
Gierlinski organized "Figure 3. [...]
b, footprints and the feathered chest impression of Andaean [sic] condor
Vultur gyphus, obtained experimentally at the Warsaw Zoo". The only
differences to the fossil are: 1. the size; 2. the feather impressions of the
condor are in front of the feet, because in Neornithes the breastbone is
usually the part of the trunk that extends farthest toward the ground (a faint
impression of the keel is present), whereas in more basal theropods these were
the pubes and the gastralia just in front of them (as well as the ischia in
ceratosaurs and basal tetanurans); 3. there is no ischiadic foot; 4. the condor
sat more symmetrically. Figure 3. a is a Chirotherium track with drag
marks, provided just in case someone may doubt the integumentary nature of the
impressions.
A few more quotes:
"Pubic-abdominal Imprint with
Feather-like Impressions (Figs. 1b, 2)
[...] The anterior right
fragment of [the] abdominal imprint is overprinted by a [sic] second digit of
[the] right foot. In other words, it looks like the belly partially overlapped
that digit. The pubic-abdominal imprint is rotated outwardly from the trackway
midline by 11°. The trackmaker sat irregularly, turning its body slightly to the
right side, and leaning the belly partially on the right foot.
Consequently, the belly did not bear the same weight as the feet and the
ischiadic callosity did while in the resting posture. Probably this is
responsible for the good preservation of the feather-like impressions.
Otherwise, if the belly had been[ ]more heavily imprinted, such delicate traces
might have simply disappeared.
The feather-like impressions are usually more than 1 cm long and mostly grouped
near the left margin of the pubic imprint."
"In my opinion, feather-like
impressions discussed herein are clearly unlike those produced by invertebrates,
nor do they resemble drag-marks left by rough skin (Fig. 3a). The drag-marks
occur rather outwardly of the impressions of the object which left them. In
contrast, these discussed impressions are located inside the pubic-abdominal
imprint. In the specimen AC 1/7, a good example of drag-marks occurs beside the
left outline of the left metapodium.
The feather-like impression[s] in the pubic-abdominal imprint strongly
resemb[l]e those which have been left by thesoft body covering of mammals and
birds (Fig. 3b). They seem to have been made by structures more flexible than
scales, thinner than flight feathers, and broader than mammalian hairs.
[PROTOFEATHERS!!!!!!] Probably they were similar to the furry feathers of
flightless birds, but guessing their exact anatomical nature on the basis of the
presented ichnological material would be hazardous. [Indeed, but a few months
later Sinosauropteryx was discovered...]
Some researchers have supposed that some non-avian theropods could be
feathered (Bakker, 1975, 1986; Feduccia, 1970; Olson, 1985; Paul, 1988).
However, those authors expected that such insulation should be present in small
forms, but the resting trace AC 1/7 was not left by a small creature. The values
of its pes osteometric ratios II3/II2 and III2/IV1 lie between those of
Liliensternus and Dilophosaurus (Farlow and Lockley, 1993,
Fig. 2). Applying the Liliensternus and Dilophosaurus
proportions of whole body length to foot length, to AC 1/7 footprint size, the
trackmaker's length can be estimated as approximately 5 m."
So the fossil record of protofeathers
extends back to the Early Jurassic, doesn't
it?
The other paper is a preliminary note
on Nomingia gobiensis from a year ago:
Rinchen Barsbold, Philip J.
Currie, Nathan P. Myhrvold, Halszka Osmólska,
Khishigjaw [what a transcription... :-( :-( ] Tsogtbaatar,
Mahito Watabe: A pygostyle from a non-avian theropod. The
independent evolution of a bird-like tail has been discovered in an
oviraptorosaur. Nature 403, 155 (the references extend to the next
page) (13 January 2000).
Contains a wonderful blue and white
drawing by Michael Skrepnick.
I won't write much about this, as
Nomingia has been named and described in the meantime and has also been
discussed onlist. I'll just quote a few things and comment them:
"Although the terminal vertebrae of
Caudipteryx are not fused, they seem to form a stiffened
rod."
"Most non-avian theropods have long
tails with elongate (relative length to width) caudal centra, whereas
oviraptorosaurs have short tails with short, broad vertebral centra. The minimum
counts are 32 for Conchoraptor (GIN 110/19), 27 for
Ingenia and 27 for "Oviraptor" mongoliensis. GIN 940824 [ =
Nomingia] has only 24 caudals, fewer than any non-avian theropod except
Caudipteryx, which has 22."
I have a guess why this is so: Caudals 23 and 24 are tiny, and 22, 23 and 24 are
together just as large as 21. If in Caudipteryx only the last 3
vertebrae are fused, the suture lines may have been overlooked...
*It's 22:55 over here, so I may
mean today, depending on where you are. :-)
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