Brachiopods (from the
Latin words brachium for arm and
poda for foot) are a small phylum of benthic marine invertebrates with an
external morphology superficially resembling bivalves, to which they
are not closely related. Over 12,000 species are recognized, grouped into
over 5,000 genera. Ninety-nine percent of these are known only from
the fossil record. At their peak in the Paleozoic the
brachiopods were among the most abundant filter-feeders and
reef-builders, and occupied a range of ecological niches, including
swimming in the style of scallops. However, after the end Permian
extinction event, brachiopods recovered only a third of their former diversity
and today are only a minor part of the benthic fauna.
Rhynchonellata Williams et al. 1996
Spiriferinida Ivanova 1972
Genus Cyrtina dalmani nana
Athyridida Boucot et al. 1964
Genus Coelospira virginiana
Atrypida Rzhonsnitskaya 1960
Genus Atrypina hami
Almost two dozen named species of brachiopods
are found regularly at Black Cat Mountain in excellent
condition. They can be picked directly from the surface and often
require little or no cleaning. For instance, below are three species of diminutive
brachiopod from the collection of Bill Rushlau who found them while collecting from surface deposits. In the upper left photograph are four
specimens of Cyrtina dalmani nana. The upper right photograph shows seven specimens of Coelospira virginiana, and in the middle-bottom are two specimens of Atrypina hami. (Photographs by G.P. Hansen)
animal has two valves made of calcium carbonate or calcium phosphate. The
brachial valve carries on its inner surface the brachia ("arms") from
which the phylum gets its name, and these support the lophophore, used
for filtering food and respiration. The pedicle valve bears the
stalk-like cartilaginous foot by which most brachiopods attach themselves to
surface. The phylum is split into two major groups based on the form of their
hinges. Articulate, or "jointed" brachiopods have teeth which fit into
sockets on the brachial valve locking the valves together. Inarticulate
brachiopods have no matching teeth and sockets, and their valves are held
together only by muscles.
Like bryozoans and phoronids,
brachiopods have a lophophore, a structure of tentacles whose hair-like cilia create
a water current that enables the animal to filter food particles from
the water. Unlike bryozoan or phoronid lophophores, which are crowns of
tentacles mounted on a single, retractable stalk, the brachiopod lophophore follows
the contour of its brachium, an internal scaffold from which the name of the
phylum was derived. Lophophores of larger species are folded in complex shapes,
loops and coils.
species avoid strong currents or waves, and typical sites include rocky
overhangs, crevices and caves, the slopes of continental shelves, and in
the abyssal depths. However, some articulate species attach to kelp fronds
and inhabit some intertidal zones when they can find a sheltered location,
such as within the cavities of gravel.
Pentamerida Schuchert and Cooper 1931
Gypidulidae Schuchert 1929
Genus Gypidula Hall
multicostata Dunbar 1920 (shown in collage directly above)
In some of the early descriptions of lower Devonian fossils
in the United States, the genus Gypidula was erected by Hall1
in 1867 and the species G. multicostata
was described by Dunbar in 1920.Dunbar's description was from specimens
found in the Birdsong member of the Lower Devonian Ross Formation in Benton and
Decatur counties in western Tennessee. Dunbar suggested G. multicostata is closely
related to G. coeymanensis from the Lower
Devonian Coeymans formation in New York, "but that species has fewer and
much coarser placations and reaches its greatest width nearer its mid-length".2 Though species of Gypidula range through the Silurian and Devonian and have been
found on most continents and many countries, a quick search led me to find only
a few references to species from Lochkovian deposits in North America and
Australia (if the reader knows of any other, a comment through the Contact Page
would be appreciated):
1.Tor Limestone Formation, ToquimaRange, Nevada3
2.Linden Group, Southern BentonCounty, Tennessee2
3.Mountain House, SiskiyouCounty, California3
4.Mt. Ida Formation, Heathcote
District, central Victoria, Australia4
5.Basal MandageryPark Formation, Manildra, New South Wales, Australia5
Citations for Gypidula:
1J. Hall. 1867. Account of some new
or little known species of fossils from rocks of the age of the Niagar Group.
.State of New York in Senate
2Dunbar, C. O. 1920. New Species of Devonian Fossils from Western Tennessee. Transactions of The ConnecticutAcademy of Arts and Sciences, Volume 23, pp
109-158. ConnecticutAcademy of Arts and Sciences, YaleUniversity, New Haven, CT.
3A. J. Boucot. 1999. Some
Wenlockian-Geddinian, chiefly brachiopod dominated communities of North America. In A. J. Boucot and J. D. Lawson
(eds.), Paleocommunities--a case study from the Silurian and Lower
4J. V. Neil. 1982. The Early Devonian
Fauna of the Mt.Ida Formation in the Heathcote
District. Victorian Naturalist 99(5):195-201.
5 N. M. Savage. 1974. The brachiopods
of the Lower Devonian Maradana Shale, New South Wales. Palaeontographica Abteilung
is extended to Bill Rushlau for finding and preparing the specimen and for
providing the photographs of Gypidula
multicostata shown in the collage above.
Subphylum Craniiformea Popov et al. 1993
Class Craniata William et al. 1996
Order Craniida Waagen 1885
Family Craniidae King 1844
Bill Rushlau recently found a specimen of this inarticulate brachiopod from the genus Philhedra
and provided the photographs in the collage below.Since it is only about 12 millimeters in
diameter, this may be the first reported occurrence of the genus from the
Lochkovian of Oklahoma.
Fay and Graffham1
listed a Philhedra species from the Middle
Ordovician, Blackriveran Mountain Lake Member of the Bromide Formation south of
Ardmore, Oklahoma.From Devonian rocks, Wiedman2
stewarti andPhilhedra crenistriata from the Givetian Silica Shale Member of the Traverse Formation near
Woodburn and New Haven in Indiana.This lithified mudstone and packstone formation represents an offshore
shelf environment.Kesling and Chilman3
crenistriatula from the Givetian Silica Formation near Sylvania, Ohio.This well-known formation is a marine deposit
of gray-blue calcareous shale and clay-filled limestone.
According to the website Paleos: Adult
individuals of this order cemented the exteriors of their pedicle valves to a "foreign
surface, generally another shell. Commonly,
the host is a brachiopod, but it may be a coral, bryozoan colony, crinoid stem,
or mollusk. Some species seem to choose a particular species of
articulate brachiopod as host. They attached to its host shell when the
latter was still alive, but it is never found extending onto adjoined valves,
as it might if the crainacean grew on an empty shell."Hoare
and Steller4 described how Philhedra crenistriatula tended to prefer attachment to larger brachiopods, particularly Paraspirifer bownockeri.Furthermore, according to Paleos: "A few members of this group (Petrocrania) have the
peculiarity of reflecting rather perfectly in the markings of their brachial
valve the surface of the host shell to which the craniacean is attached.
This may have served the purpose of camouflage, making the animal more
Citations for Philhedra:
1 R. O.
Fay and A. A. Graffham. 1982. Biostratigraphic and paleontological studies.
Echinoderm faunas from the Bromide Formation (Middle Ordovician) of Oklahoma: Lawrence, Kansas, University
of Kansas Paleontological Institute Monograph
2 L. A.
Wiedman. 1985. Community paleoecological study of the Silica Shale equivalent
of northeastern Indiana. Journal of Paleontology59(1):160-182.
3 R. V.
Kesling and R. B. Chilman. 1975. Strata and megafossils of the Middle Devonian
Silica Formation. University
of Michigan Papers on
Hoare and D.L. Steller. 1967. A Devonian Brachiopod with Epifauna. The Ohio
Journal of Science67(5): 291.
5zipcodezoo.com lists six species and subspecies in the Genus Philhedra: P. athenae, P.
crenistriata, P. frayi, P. laelia, P. megalophthalma, P.