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Re: Feathers as fossilized behaviour (was:Re: Function Talks at Ostrom Sympos...
In a message dated 2/18/99 2:06:05 PM EST, firstname.lastname@example.org writes:
<< What no one seems to have commented on (except Alan Brush,
who briefly mentioned it at the symposium during discussion) is that this
represents a very clear case of fossilized behaviour... >>
This is a very ingenious observation. Run with it!
Robert Broom described the prosauropod _Aetonyx palustris_, back in 1911,
something like this (excerpted from my notes for a forthcoming Dinosaur
Aetonyx palustris is based on the smallest of three dinosaurian type
specimens collected by A. R. Walker from J. L. Harries's farm in the Orange
Free State, Republic of South Africa (the other two were the types of
Massospondylus harriesi and Gryponyx africanus). Robert Broom, the describer,
considered all three dinosaurs to have been carnivorous. We now know, however,
not only that they were herbivorous but that they were actually three
specimens of different sizes belonging to the same prosauropod species,
Massospondylus carinatus. Measurements of the Aetonyx palustris type specimen
indicate that it was an individual about two-thirds adult size.
Broom noted that the proportions of the bones of Aetonyx were slenderer
those of similar dinosaurs. He was also impressed by the shape of the second
forefoot claw, in which the vascular grooves did not meet at the tip but atop
the claw about two-thirds of the way to the tip. This gave the claw two
points, one above the other?almost certainly a growth abnormality, not a
difference requiring the creation of a new species.
In common with the other two species, the second hind foot claw of
had a sharp outer edge and a rounded inner edge, which indicated to Broom that
in life the dinosaur used that particular claw for grooming, much as many
birds do with their feet today. He suggested that the skin was covered by
elongated scales that needed to be cleaned periodically, "after the animals
had been hunting their prey on the muddy banks of lakes." In 1981, Michael
Cooper took this suggestion further and proposed that Massospondylus sported
true feathers, or "thermoplumes," to protect itself from the midday heat of
its desert (not marshy) habitat. Unfortunately, direct proof of these
suggestions, in the form of feather or skin impressions, is still lacking.
Just some early references to featherlike dermal structures among dinosaurs...