Hi all

If anyone has seen something similar to this beastie, please let me know!

Avril has kindly put up  my reconstruction of a fossil shell I
collected a few years ago; this worm-eater can be viewed at:

http://www.manandmollusc.net/Mystery_shell_pages/andrew2.html

Sorry it's not a live link, but gmail doesn't seem to be able to
reproduce live links.

The shell is a couple of pieces of natural mold in a tuff of latest
Eocene age. I had to make silicone casts from these fragments to fix
in my mind what the shell looked like. The external pieces of the mold
looked so peculiar that until weeks ago I was unsure that it was even
molluscan, and Alan Beu, looking at the molds, didn't seem any more
certain. However another examination convinced me that the plaits are
gastropod. It took me a while just to figure out which end of the
external mold was posterior and which anterior (you'd understand if
you saw the pieces). The surface of the decalcified shell is covered
with bryozoa; the anterior and posterior ends were broken off before
burial, leaving only about 1 whorl, with the posterior end full of
matrix which I removed to show the plaits in 3D negative.

It is is a really weird turbinellid. Its length is estimated at about 10cm,
though it is reconstructed from a couple of fragments of internal &
external mold. Measured from a single whorl of a cast, the spire angle
appears to be about 26 degrees, though I can't make the reconstruction
reflect this without screwing up the
whorl-profiles... might need to redraw it with more whorls (they
increase in size very slowly, so this is likely the problem with my
drawing... gave it too few). The shell wall is extremely thick, and
despite the rounded upper whorl-profile, the aperture is a narrow and
strongly-inclined parallelogram. Sutures are set in a deep wide
channel which has a narrow flat "floor". Axial ribs are collabral and
are strongest where they cross the basal constriction; they show
through the very thin parietal shield. There is no spiral sculpture on
the midwhorl or posterior parts of whorls. The plaits are sharp and
clear and are wrapped posterior of the columella, as is common in
turbinellids but not volutids. The posteriormost is a fine but
distinct thread. Not shown on the drawing are secondary plaitlets, one
between each pair of primary plaits. The plaits appear to have been
visible when the aperture was complete (some turbinellids eg Exilia
often have plaits that end out of sight inside the shell). The
protoconch and anterior end abapical of the plaits are
conjectural but logical. The bodywhorl-profile is correct. It's from
near Dunedin, NZ and is the only specimen known.

If I had to place it in a subfamily, I think I'd have to choose
Turbinellinae, though Ptychatractinae is always possible.

Perhaps I should send Avril images of the molds and casts to post...

--
Regards
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
Mollusc, Toyota & VW van fan

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