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New Struthionid?

  Remember the good ol' days when people named footprints and tried to use them
to argue priority when people named body fossils they believed made the prints?
Or when people named what they thought were fragments of skin, and used that to
establish the existence of a body, rather than trace, taxon? Now, they've done
it for eggs. I was given a draft preprint, and because of this, the taxon given
won't be listed until the paper is out, but it's a new species of _Struthio_
found in the fossil beds of Laetoli.

  Harrison, T. and C. P. Msuya. in press. Fossil struthionid eggshells from
Laetoli, Tanzania: Taxonomic and biostratigraphic significance. _Journal of
African Earth Sciences_ [to be determined]

  I won't post the abstract because doing so would describe the taxon I am
trying to avoid, here ;).

  The holotype will be a fragment of eggshell, and no body fossils are
referred. What is difficult for me, while their grounding is solid in
distinguishing this species from others on the basis of eggshell thickness,
pore density, and pore diameter, is why they chose to discard precedent in
naming the taxon as a body fossil and a species of _Struthio_ rather than name
ootaxa and apply the ootaxa to the species. This is, of course, rather
excessive, but serves the point of referring a fossil egg to a body taxon that
you cannot now demonstrate relevant without finding an adult in proximity or in
fact whether you can determinately indicate the likelihood of bone to egg
adherence. Not so here. The eggshell occurs in the Upper Laetoli beds below the
Tuff 3, and eggshell determined to belong to *Struthio camelus* occurs above
that, but also intermingles in part of Tuff 3 with the new taxon. This allows
them to show sympatric struthionids occured. An hypothesis I would suggest
would be that environmental factors can lead to eggshell variation in a single
species without altering skeletal anatomy, a response to different humidity,
laying conditions, or the health of the layer (i.e., the one who lays the egg,
not the stratigraphic level), and this would lead to questioning fossil
association of eggshell to body fossils without clear associative evidence
("Big Momma" associative evidence, for example).


Jaime A. Headden

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)

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