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Feathered dilophosaur - not from the tracks!

Brian Choo wrote:

>The specimen referred to as AC 1/7 from the Lily Pond Quarry (Portland
>Formation) in Massachusetts (part of the Hitchcock collection).
>It is a resting imprint of a bipedal dinosaur consisting of the imprint of
>the belly, ischiadic callosity and feet. Impressions from the belly print
>suggest a furry integument, similar to that found on ducklings. (Gierlinski
>1997 in Morales M. (ed), The Continental Jurassic. Museum of Northern
>Arizona Bulletin 60: 179-184)

Having examined this and many other trackways in the Hitchcock footprint
collection, Paul Olsen and I disagree with Gierlinski's interpretation.
Rather, from the extent of these "feather" impressions and their position
adjacent to BOTH feet, they are more likely to be a drag mark of gooey mud
as the feet were emplaced on the substrate and slid forward to their final
positions. Similar impressions are also seen on surfaces that are clearly
undertracks (i.e. slabs that have been split along multiple bedding planes
showing the track on several surfaces, with only deformation of sediment
layers rather than penetration of these layers by the foot). Thus, these
features are most likely an artifact of the mechanics of locomotion on a
slippery substrate.

(BTW the tracks (excluding metatarsal impression) of specimen AC 1/7 are
about 16 cm long...)

Emma C. Rainforth
Geosciences Rm. 206E
Lamont-Doherty Earth Observatory
Box 1000
Palisades, NY 10964
ph. (914) 365-8621
fax (914) 365-8154