Michelinia sp.
Class Tabulata (coral)

Previously identified as: Pleurodictyum eugeneae White

 

Top and Bottom views

General abundance:  Common

Michelinia is a tabulate coral in the family Favositidae.
The left view shows the numerous subcircular calices, and
the right view shows the underside of the coral where it
was possibly attached to a crinoid stem. I have specimens
that are attached to crinoid stems.

Michelinia sp. picture from the following URL
http://www.geocities.com/atrypa/ccorl.html

Pleurodictyum and the Michelinia appeared to
me to be the same coral.

I asked Alan Goldstein and Dr. Yancey for their comments.
_______________________

According to the Treatise (vol. F corals), Pleurodictyum ranges
from U. Silurian - M. Devonian. Michelinia ranges from L. Devonian -
Permian. Therefore if your coral is above the Devonian it can't be
Pleurodictyum. Incidentally, there are several unique michelinid
corals found in Missouri including Beaumontia, Conopoterium
(Louisiana Limestone) and ?Tabellaephyllum (Chouteau Limestone)

Alan Goldstein
_______________________

The corals you have are fairly common in Carboniferous mud-bottom
environments, but are largely undescribed. There are only a couple
people who have worked with these and the most knowledgeable
person moved to Australia and has not been able to complete any
studies on them. They have been collected by several workers and
there are a few publications which will could provide a reasonable
guide to identification. I will check on this when I get to my office.

On the matter of age ranges cited by the Treatise and by Index Fossils,
remember that those publications used literature reports available at
the time the work was collected, and that both are fairly old publications.
Concepts of identification have changed and more is known about the
fossils now, so the age range citations are only general guides, not good
indications of identification. The consequence is that you should use the
fossil names adopted by the latest worker to study the fossils, since that
reflects the latest evaluation. This way of finding identifications is
unsatisfying, but is inevitable in a profession where taxonomists are
rapidly retiring and dying, and not replaced by younger people.

As for the shape of the corals, that is a result of life in the same
environment. It is sort-of like homeomorphy, but with such plastic
organisms as corals and other colonial organisms, the concept of
homeomorphy does not really apply. For corals, the shape is
determined almost entirely by the immediate environment - this is
called eco-phenotypic growth form; in the case of the brachiopods,
the shape is controlled very much by genes in the animals genome,
only indirectly by the direct environment. The difference can be
understood by thinking of what each animal would do if it settled in
a different location on the seafloor than the one it is most common
in: if the coral settled on a rock outcrop or on a sand bar, the individual
animal would produce a shape different from that it produces if it settled
on a mud bottom; if the brachiopod settled on a sand, mud or rock bottom,
it would produce the same shape as if it had settled on the preferred
substrate - the shape is genetically determined. When we say a brachiopod
is homeomorphic, it means that the brachiopod species has acquired a
form suitable for a particular environment over many, many generations
of selective breeding. When we look at a coral, we see a strong tendency
for the environment to override the genetic control on colony form. The
same species of coral can occur as a branching form, an irregular form,
a rounded "coral-head" form, or a plate-like form, depending on the
site that the larvae settles on. This is seen in modern and ancient corals,
and is known to be the same for many bryozoans and is very common
among stromatoporoids.

Dr. Tom Yancey
_______________________

Thanks to Dr. Yancey for providing the
following Citation

Cocke, J. M., Boardman, D. R., II, and Mapes, R. H., 1989,
Stratigraphic distribution and facies control of late
Pennsylvanian coral assemblages in the North American
midcontinent, p. 249-278, in Boardman, D. R. et al., edis.,
Middle and Late Pennsylvanian chronostratigraphic boundaries
in north-central Texas: Glacial-eustatic events, biostratigraphy
and paleoecology, Part 2: Contributed Papers, Texas Tech
University Studies in Geology 2, 380 p.

The coral work is by J. Cocke, now deceased, and covers
assemblages collected from Kansas, Oklahoma and Texas.
This work discusses corals at the genus level, but is the only
comprehensive account available for the cyclic units.
_______________________

Previously identified as Pleurodictyum eugeneae White
Pennsylvanian Index Fossil
Reference:
Index Fossils of North America
Pleurodictyum eugeneae White
Page 111
Plate 39 fig. 20-21

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