Hi Art,

Some authours used to extend the Hormotoma superfamily (pleurotomariacea)
into the the Devonian and Carboniferous (genera such as Rhineoderma, Baylea,
etc.)...others saw no connection other than outward morphology. Raymond
Moore had this family extending to modern genera but later reduced it to
lower paleozoic... cutting the line to the upper paleozoic...others cut the
line from upper paleozoic to the Mesozoic...gets complicated!!
Paleozoic gastropods are a very understudied group. They need attention. A
good chunk of paleozoic paleontology is based on biostratigraphy and
gastropods have not been very useful in this respect. Much more useful
macrofossils for this purpose are rugose and tabulate corals and
brachiopods. I had the opportunity to work with a couple of 'doctor
emeritus' (old fossils themselves) and they never had any time or
inclination to look at gastropods....we spent our time thin sectioning
corals to determine rock ages, etc.   An aside to all this: most of the
preeminent paleozoic coral researchers(Sando, Pedder, Bamber,
Federosky,etc.) do not believe that modern corals (the scleractinians) are
in anyway related to paleozoic corals. They see Mesozoic corals arising from
some unknown group in the Triassic..but that is another story.
----- Original Message -----
From: "Art Weil" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, November 15, 2000 8:41 PM
Subject: Re: Hormotoma/ no modern descendents?


> Dear Joe;-
>     I understand the dieing out of Hormatoma----but did it do so without
> branches, descendants, etc.? It appears nothing like  a "Slit-Shell", but
very
> much like slim coiled families----Terebra, Epitoniidae, Miters, etc.
>         Art
>
> Joe and Nora wrote:
>
> > Hello Art,
> >
> > Joe here. I sifted through my collection and literature. All of our
> > 'Hormotoma' specimens are Ordovician or Silurian in age. This is mostly
a
> > North American fossil (although also found 'rarely' in Europe). It was
> > usually placed (despite its outward appearance) until the 1940's  in the
> > superfamily Pleurotomariacea by some authors. Its kin, Mourlonia,
somewhat
> > resembles descendents through to the Pleurotmaria.
> > Subsequesnt authors do not place it in this superfamily but place it  in
> > agroup archaeogastropods with no further lineage. It is thought to die
out
> > in the Silurian. It is thought by most to have no relationship with the
> > modern pleurotomaria.
> > Most authors ( some exceptions) do not accept any known antecedents of
the
> > modern Pleurotomaria until the Mesozoic age.
> > Your species 'gracilis' was first placed in the genus  Murchisonia
(Hall,
> > 1847) and subsequently changed by the author to Hormotoma sometime in
the
> > 1850's (I 'think').
> >     Nora and I just obtained a scanner and it is surprising how well it
> > scans small fossils. Sometime in the not too distant furue we'll scan
some
> > paleozoic gastropods, mesozoic pleurotomaria, etc. and make them
accessible
> > to Conch-L subscribers to view.
> >
> > Original Message -----
> > From: "Art Weil" <[log in to unmask]>
> > To: <[log in to unmask]>
> > Sent: Tuesday, November 14, 2000 7:34 PM
> > Subject: Hormotoma
> >
> > > Dear (probably Old Seashells and Andy);-
> > >         What I have here is a Hormotoma gracilis (maybe Homotoma?). It
> > > measures 13.48mm long and is about 400 million years old. Since a
> > > fleeting glance makes it look like an Epitonium (or Cerith or other
> > > coiled critter) I wondered if there is some descendency from the
fossil
> > > that I have. Inquiring minds want to know.
> > >             Art