Brachiopods Identification Guide for Common Fossils from the Cincinnatian of Ohio To start, click on...

Brachiopods Identification Guide for Common Fossils from the Cincinnatian of Ohio

To start, click on A fossil type or click here for information on how to use this

program

©2001, John H. Whitmore

Assistant Professor of Geology

Cedarville University Cedarville, Ohio

Drawings by Alison Warren

Main Menu Trilobites Brachiopods Cephalopods Tentaculitoids Bryozoans Gastropods PelecypodsCrinoids Corals Exit

Crinoids

Pelecypods

Gastropods

Trilobites

Tentaculitoids

Corals

Bryozoans

Cephalopods

Brachiopods Click here for brachiopod species

Main Menu Trilobites Brachiopods Cephalopods Tentaculitoids Bryozoans Gastropods PelecypodsCrinoids Corals

Kingdom AnimaliaPhylum Brachiopoda

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Brachiopods are solitary marine organisms that live between two valves or “shells.” They are very common in the Cincinnatian rocks of Ohio. They are externally different from the pelecypods (clams) in that the left and right halves of the brachiopod shells are usually mirror images of each other (see picture below). Internally, brachiopods are completely different from the pelecypods. Brachiopods feed with a special filtering organ called the lophophore which is located between the valves and attached to the brachial valve. The pedicle extends through a small opening or hole in the pedicle valve and is used as an anchoring device. The interior of the brachial valve is important in taxonomic differences between various species.

Dorsal View

(brachial valve)

Posterior view Anterior view

sulcus

fold

beak

hinge

AnteriorPosterior

brachial valve (dorsal valve)

pedicle valve (ventral valve)

pedicle opening

lophophore

beak

growth lines

ribs (plications)

A biconvex brachiopod

A concavo-convex brachiopod

A convexi-concave brachiopod Symmetry differences between brachiopods and pelecypods

The symmetry in brachiopod valves is usually perpendicular to the hinge line.

If pelecypod valves are symmetrical (and often they aren’t), the symmetry is usually parallel to the hinge.

pedicle

Dalmanella meeki

Glyptorthis insculpta

Hebertella

Hisobeccus capax

Holtedahlina sulcata

Lepidocyclus perlamellosus

Leptaena richmondensis

Petrocrania scabiosa

Plaesiomys subquadrata

Platystrophia

Plectorthis fissicosta

Plectorthis plicatella

Rafinesquina ponderosa

Rhynchotrema dentatum

Sowerbyella rugosa

Sowerbyella sp.

Strophomena

Tetraphalerella neglecta

Zygospira modesta


Dalmanella meeki


A

B

CD

FE

A small brachiopod, usually 1.5 to 1.8 cm wide. Gently biconvex in profile. The brachial valve has a shallow sulcus. The ribs are finer than Plaesiomys and Glyptorthis. Dalmanella also tends to be smaller than these genera in the Cincinnatian.B– interior of brachial valveC– pedicle view (opposite side of D)D– brachial view (opposite side of C)E– pedicle view (opposite side of F)F– brachial view (opposite side of E)

Glyptorthis insculpta


AB

C

DE

A medium sized brachiopod averaging about 2.5 cm in width. Biconvex profile, brachial valve more inflated and it has a sulcus. The intersection of the radiating ribs and the concentric growth lines produces a reticulate ornamentation on the exterior of the valves (see B). Plaesiomys is similar in external morphology but lacks the reticulate pattern.

B– exterior brachial view showing sulcus

C– exterior pedicle view

D, E– interior brachial view

Hebertella


A

B

E

DC

F

Large biconvex brachiopod ranging from 2.5-4.5 cm in width. The pedicle valve is usually flatter than the brachial valve. The brachial valve has a large distinctive fold. The pedicle valve has a slight sulcus. Two species: Hebertella alveata and Hebertella occidentalis .

B– posterior view

C, F– brachial view

D– pedicle view

E– interior of pedicle valve

Hebertella alveata


This species of Hebertella lacks the deep fold and sulcus of H. occidentalis. This species is usually smaller in size and has a shallower sulcus on the pedicle valve. The pedicle valve is almost flat. There is a large fold on the brachial valve, but within the fold is a shallow sulcus that extends to the anterior margin, shown well in Fig. D.

A

D

BC

E

B– brachial view

C– pedicle view of B

D– brachial view

E– pedicle view of E

Back to Hebertella page

Hebertella occidentalis


A

B

C

E

D

This species of Hebertella is characterized by a large fold on its brachial valve (Fig. B) and a deep sulcus on its pedicle valve (Fig C and D). Hebertella alveata does not have a deep sulcus on its pedicle valve and has a very slight sulcus on its brachial valve that extends from the beak to the anterior margin. The pedicle valve is much flatter in H. alveata.

B– brachial view

C, D– pedicle view

E– interior of pedicle valve showing characteristic heart shaped muscle scar and triangular pedicle opening

Back to Hebertella page

Hiscobeccus capax


Hiscobeccus capax is a small biconvex brachiopod ranging in size from 0.8 cm to 2.0 cm. This species is very difficult to distinguish from Lepidocyclus perlamellosus without looking at its internal morphology. The main difference is that Hiscobeccus is generally smaller and has less distinct growth lines crossing the plications. Smaller specimens of Hiscobeccus tend to be triangular in outline. There are three plications in the sulcus making it different from Rhynchotrema dentatum which only has one plication in its sulcus.

A

E

DC

B

B-- posterior view of beak

C– anterior view

D-- brachial view, fold

E– brachial and pedicle views

Holtedahlina sulcata


A small to medium sized biconvex brachiopod with a deep sulcus in the pedicle valve. Ranges from 1.5 to 2.0 cm in width. Some specimens may be flattened by depositional processes and do not clearly show the sulcus.

B– brachial view (fold)

C, D– pedicle view (fold)

E– anterior view

A

B

DC

E

Lepidocyclus perlamellosus


Lepidocyclus perlamellosus is a medium sized biconvex brachiopod ranging in size from 2.0 cm to 2.5 cm. This species is very difficult to distinguish from Hiscobeccus capax without looking at its internal morphology. The main difference is that Hiscobeccus capax is generally smaller and has less distinct growth lines crossing the plications. Lepidocyclus is slightly larger and has more distinct growth lines crossing the plications (Figs B and C). There are three plications in the sulcus making it different from Rhynchotrema dentatum which only has one plication in its sulcus.

A

BC

DE

B, C– pedicle view and sulcus showing strong reticulate pattern. Compare to Hiscobeccus capax , figure D.

D– anterior view showing three plications in the sulcus

E– posterior view

Leptaena richmondensis


A

B

C

DE

A small to medium sized concavo-convex brachiopod ranging from 2-3 cm in width. It is characterized by strong concentric growth lines, but does have fine radiating ribs.

B, E– pedicle view

C– interior of brachial valve

D– brachial view

Petrocrania scabiosa


A

B

C

D

A small inarticulate brachiopod with a circular outline ranging in size from 0.5 to 1.5 cm in diameter. It is usually found attached to other brachiopods, like Rafinesquina, as shown in the photos. The radial growth lines of Rafinesquina usually show through the shell of Petrocrania because its shell was so thin. This is illustrated in B, C, and D.

Plaesiomys subquadrata


A

B C

D E

F

A medium sized brachiopod ranging from 2.5 to 3.5 cm in width. It ranges in profile from convexi-concave to unequally biconvex. Subquadrate outline with straight hinge line, width is greater than length. Plaesiomys has a more rectangular outline than Glyptorthis and lacks the reticulate pattern present in Glyptorthis.

B, C– Brachial view

D--Interior pedicle view

E– Exterior pedicle view

F– anterior view, brachial valve on top.

Platystrophia


There are about 9 species of Platystrophia in the Cincinnatian. Each of the species has subtle differences between them. Important features to look for are the number of plications on each side of the fold or sulcus, the number of plications in the sulcus, size and overall shape. Look at these features carefully in order to differentiate the species in this genera. In the Waynesville area, P. clarksvillensis is probably the most common species.

Platystrophia acutilirata

Platystrophia clarksvillensis

Platystrophia cypha

Platystrophia laticosta

Platystrophia moritura

Platystrophia ponderosa auburnensis

Platystrophia ponderosa ponderosa

Platystrophia acutilirata


A large biconvex brachiopod whose width is significantly greater than its length and has strong radiating ribs. This species is characterized by three nearly equal plications in the sulcus, and a low rounded fold. It has 10 or more plications on each side of the fold and sulcus. About 2.5 cm in width.

A– brachial view, showing fold

B– pedicle view, showing sulcus

C– posterior view

D– anterior view

A B

C

D

Back to Platystrophia page

Platystrophia clarksvillensis


A large biconvex brachiopod whose width is significantly greater than its length and has strong radiating ribs. This species has almost 3 equal plications in the sinus, and has 8 or 9 plications on each side of the sinus. Both valves are convex to the outer edge. 2.0 to 4.0 cm in width.

A

B

C

D

E

B– pedicle view, showing sulcus

C– brachial view, showing fold

D– posterior view

E– anterior view


Platystrophia cypha


A large biconvex brachiopod whose width is significantly greater than its length and has strong radiating ribs. This species is distinguished by a strong medial rib in the sulcus, the sides of the pedicle valve are flattened and hollowed out, and there are more than nine plications on each side of the fold. About 3 cm in width.

A

B

C

D


B– pedicle view, showing sulcus and strong medial rib

C– posterior view

D– anterior view showing strong medial rib in sulcus


Platystrophia laticosta


B

D

C

A

A medium sized biconvex brachiopod whose width is significantly greater than its length and has strong radiating ribs. This species has seven ribs on each side of the sulcus and fold and three plications in the sinus, with the medial plication being the strongest. 2.0 to 3.0 cm in width.

B– brachial view, showing fold

C– posterior view

D– anterior viewBack to Platystrophia page

Platystrophia moritura


A

B

C

D

A medium sized biconvex brachiopod whose width is significantly greater than its length and has strong radiating ribs. This species has equally developed plications in the sulcus and more than ten ribs on each side of the fold or sulcus. The pedicle valve is convex to the outer edge and is not flattened. 3.0 to 4.0 cm in width.

B– posterior view

C– brachial view

D– anterior view showing ribs in sulcus


Platystrophia ponderosa auburnensis


A large biconvex brachiopod with an extremely thick shell and strong radiating ribs. 3.5-4.5 cm in width. Only slightly wider than long. This subspecies has a short hinge line and great depth to the shell. It is limited to the Mt. Auburn unit.


B– posterior view

C– pedicle view, showing sulcus

A

B

C


Platystrophia ponderosa ponderosa


A B

A large biconvex brachiopod with an extremely thick shell and strong radiating ribs. 3.5-4.5 cm in width. Only slightly wider than long. This subspecies has along hinge line compared to P. ponderosa auburnensis.


B– pedicle view of another specimen, showing sulcus


Plectorthis fissicosta


A small biconvex brachiopod ranging in size from 1.2 to 1.8 cm in width. Notice that the plications in this species are numerous and split, unlike Plectorthis plicatella which are less numerous and do not split. P. fissicosta is also slightly larger.

B– pedicle view showing splitting of plications

A

B

Plectorthis plicatella


A small biconvex brachiopod ranging in size from 0.8 to 1.1 cm in width. Notice that the plications do not split as in Plectorthis fissicosta. P. fissicosta is also larger.

B-- posterior view

C– pedicle view (fold)

D– brachial view (slight sulcus)

A

B

C

D

Rafinesquina ponderosa


A

D

B

C

E

A large concavo-convex brachiopod, 4.0-5.0 cm in width. Semicircular outline, with straight hinge line. Width and length are approximately equal. Fine numerous radiating ribs on the exterior of both valves. The brachial valve is concave and the pedicle valve is convex in contrast with Strophomena.

B– posterior view

C, E– pedicle view

D– brachial view

Rhynchotrema dentatum


A small biconvex brachiopod which is distinct from Hisobeccus capax and Lepidocyclus perlamellosus by having only one plication in its sulcus. It ranges from 1.0 to 1.5 cm in width.

A

B

FE

D

C

B– anterior view

C– pedicle view showing single plication in sulcus

E– posterior view

F– brachial view showing fold

Sowerbyella rugosa


Small brachiopod with a semi-circular outline and a concavo-convex profile. Wide, straight hinge line. Numerous, very fine ribs. 1.0-2.0 cm in width. Distinguished from Sowerbyella sp. by concentric wrinkles along the front margin.

A

B

C

B– pedicle view showing concentric wrinkles along front margin

C– brachial view

Sowerbyella sp.


Small brachiopod with a semi-circular outline and a concavo-convex profile. Wide, straight hinge line. Numerous, very fine ribs. 1.0-2.0 cm in width. Distinguished from Sowerbyella rugosa by a smooth front margin, without wrinkles.

A– mass mortality horizon of Sowerbyella sp.

C– pedicle view (convex)

D– interior of brachial valve

E– exterior of brachial valve (concave)

AB

C

D

E

Strophomena


Strophomena concordensis

Strophomena nutans

Strophomena planoconvexa

Strophomena planumbona

Strophomena vetusta

Strophomena is a relatively common medium sized concavo- convex species of brachiopod in the Cincinnatian. The species have subtle differences between them and unless you have a pristine specimen, it might be difficult to distinguish between the species. Read the descriptions carefully to distinguish between species.

Strophomena concordensis


A

B

D

C

E

Medium sized brachiopod with semicircular outline and relatively straight hinge line. The brachial valve is convex and the pedicle valve concave. Relatively large size compared to other species of Strophomena, 2.5-3.5 cm wide. This species also has a somewhat triangular outline, delicate striations, and absence of a sulcus and fold.

B, C– pedicle view

D– brachial view

E– interior of pedicle valve

Back to Strophomena page

Strophomena nutans


A

B

C

D E

This differs from similar species of Strophomena by its strongly triangular outline, delicate striations and a thickening of the anterior margin. 2.5-3.0 cm in width. Concavo-convex profile.

B– brachial view

C– interior of pedicle valve

D, E– pedicle view


Strophomena planoconvexa


A

BC

D E

Medium sized brachiopod with semicircular outline and relatively straight hinge line. This differs from other species of Strophomena by having irregular coarse striations and a characteristic muscle scar on the interior of the pedicle valve. 2.5-3.0 cm in width. Concavo-convex profile.

B– pedicle view

C– brachial view

D– interior of pedicle valve

E– pedicle view showing irregular coarse striations


Strophomena planumbona


A

B C

D E

Medium sized brachiopod with semicircular outline and relatively straight hinge line. Differs from similar species of Strophomena by having a relatively small size, rectangular form, and lacking a fold and sulcus. 1.5-3.0 cm in width. Concavo-convex profile.

B– brachial view

C– pedicle view

D, E– interior of pedicle valve


Strophomena vetusta


A D

C

B

Medium sized brachiopod with semicircular outline and relatively straight hinge line. Differs from similar species of Strophomena by having four parallel ridges on the inside of the brachial valve (shown in A and D) and wrinkles on the shell near the hinge line (shown in C). Concavo-convex profile, ranges from 2.5 to 3.5 cm in width.

A– mass mortality horizon of S. vetusta

B– pedicle view

C– brachial view, showing wrinkles along hinge line

D– interior of brachial valve showing four parallel ridges, distinctive of this species.


Tetraphalerella neglecta


This species is very similar to Strophomena, but is different in that it is not strongly triangular, has finer striations, and the impressions on the inside of the brachial valve are very different. It does not have a well defined sulcus or fold. Specimens range from 2.5 to 3.0 cm in width and are concavo-convex. Note the thickness in figure B.

B– posterior view

C, D– brachial view

E– pedicle view B

ED

C

A

Zygospira modesta


A

B

C

D

A very small biconvex brachiopod with nearly equal length and width. 3-7 mm in width. Circular to sub circular outline with coarse plications.

A– pedicle view

C– brachial view (sulcus)

D– mass mortality zone of Zygospira

Bryozoans Batostoma

Bythopora

Constellaria

Dekayia

Escharopora

Homotrypella

Parvohallopora ramosa

Parvohallopora subnodosa

Peronopora


Kingdom AnimaliaPhylum Bryozoa

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Bryozoans are tiny colonial organisms, often mistaken for corals. The individual bryozoan is usually less than 1 mm in size. Bryozoan colonies can be branching, twig-like, fan-like, or encrusting. The entire colony is referred to as a zoarium. Some bryozoan colonies are smooth and others have monticules or bumps covering them. Each small opening or aperture was the home for an individual bryozoan or zooecium. The small animal seals the hole with a “door” or vestibule. They are difficult to identify without microscopic study. Sometimes the pattern of the apertures, size, or shape is characteristic and can be used for generic identification.

A living bryozoan (zooecium) inside its coffin-like home.

aperture openingmonticule

lophophore

A colony of individual bryozoans or a

zoarium.

Cross section showing arrangement of individual zooecia.

Batostoma


A

C D

E

Forms branching colonies. Apertures are elongate and irregularly shaped. Monticules are sparse and when they occur, are not uniformly spaced. Branches range from 2 to 6 mm in size.

B– detail of the zooecia apertures

B

Forms colonies of very thin stick-like branches. Apertures are elongate and oval. Branches 1-2 mm in diameter.

B– detail of apertures

Bythopora


A

C

B

Constellaria


A B

Forms branching or fan-like colonies. The monticules are strongly star-shaped, making the form unique and easy to identify.

A– a sheet-like colony

C– detail of star-like monticule showing individual zooecia

D– a branch-like colony

C

D

Dekayia


A

C

Forms very large branching colonies. The branch diameters are often up to 1 cm in diameter. Apertures are sub polygonal. Monticules are not prominent.

B– detail of individual zooecia

B

Escharopora


This bryozoan has a characteristic blade shape with diamond shaped apertures. This specimen is 5.0 cm long.

B– detail of individual zooecia. Edge of penny for scale

A

B

Homotrypella


A

C

D

Forms hemispherical gum-drop shaped colonies. Apertures are rounded. They usually are found growing on a small broken brachiopod shell. About 1.5 cm in width and height.


C, D-- views from above and from the side of the same two colonies.

B

Parvohallopora ramosa


B

C

D

E

Forms branching colonies with prominent, regularly spaced and sharp monticules. Monticules can sometimes occur in ridges as in Figure D. Apertures are smoothly oval, regularly spaced, and very uniform in shape. This differs from P. subnodosa by having sharp monticules instead of rounded ones.

A– detail of individual zooecia (blurry spots are sharp monticules protruding out of the picture).

A

Parvohallopora subnodosa


A C

D

Forms branching colonies with prominent, regularly spaced and rounded monticules. Apertures are smoothly oval, regularly spaced, and very uniform in shape. This differs from P. ramosa by having rounded monticules instead of sharp ones.


B

Peronopora


A

C

Forms colonies of flat, bifoliate sheets. Zooecial apertures are rounded.


B

CephalopodsCameroceras inaequabile

Treptoceras duseri


Kingdom AnimaliaPhylum MolluscaClass Cephalopoda

Exit

Cephalopods are members of the phylum Mollusca and include squid, octopi and the pearly nautilus. Cincinnatian cephalopods were straight shelled squids. The siphuncle connects the cameras (chambers) together. The squid could pass air to the chambers via the siphuncle to make it float higher in the water or sink as it swam.phragmacone

living chamber

A living shelled cephalopod. Modern cephalopods, with the exception of one species lack shells.

siphuncle

septum

camera (chamber), often containing cameral deposits

sutureaperture

apex

Cameroceras inaequabile


A

B

C

Individual shells can exceed 210 cm in length and 20 cm in diameter! The siphuncle is large and may comprise up to ½ of the shell. The siphuncle may not be preserved in many specimens giving the shell a “D” shape or making it flat, if compressed.

Treptoceras duseri


A

B

D

C

This is the most common cephalopod in the Cincinnatian of Ohio. It can reach a maximum length of 60 cm. The siphuncle is small and tends to be located near the center of the shell. When the siphuncle is preserved alone, it often appears as a string of beads (as in B).

B– siphuncle

D– x-section showing siphuncle

Corals•Favistina stellata

•Grewingkia canadensis

•Protaraea richmondensis

•Tetradium approximatum

•Unidentified coral (?)


Kingdom AnimaliaPhylum Cnidaria

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Phylum Cnidaria contains the corals, jellyfish, and anemones. Corals can be solitary or colonial. Corals have a rich fossil record because they excreted a hard calcium carbonate exoskeleton that preserves well. The Cincinnatian solitary corals are quite large, and are “horn” or “tooth” shaped. Individuals in the colonial corals are usually quite small, coralites being 1-3 mm in diameter.

A solitary horn coral.

septum

growth line

septal furrow

A colonial tabulate coral.

tabulae

corallum

corallite

corallite

Favistina stellata


A

B

A colonial rugose coral forming hemispherical masses up to 10 cm in diameter. The individual corallites are polygonal in cross section.

Grewingkia canadensis


A

B

C

D

A solitary rugose coral that has an elongate and slightly curved corallum. Septa are numerous. Specimens can reach up to 13 cm in length.

D– the top of the coral showing the many septa.

Protaraea richmondensis


A

B

C

An encrusting colonial coral. The short septa give each corallite a crenulated appearance.

B– Protaraea encrusting a gastropod

C– detail of individual corallites

Tetradium approximatum


A

B

C

Colonies form very large hemispherical masses.

A– view from above (top view of colony)

B– cross section showing long narrow corallites

C– cross section showing hemispherical cross sectional shape

Unidentified coral (?)


A

B

Unidentified coral. Possibly Streptelasma which when small, forms small encrusting colonies. These may not be coral at all but annelid worm tubes. See Davis, p. 44-45, Figure 16.

Crinoids•Cincinnaticrinus pentagonus

•Cupulocrinus polydactylus

•Iocrinus subcrassus

•Plicodendrocrinus casei


Crinoids are echinoderms that live on a long stalk, or column. Their crown is similar to an upside down starfish. Cross sections of the column usually have a tiny star within them. Columns and columnals are the most common parts found, although occasionally a crown or calyx can be found. It is rare to find the entire crinoid preserved. Crinoids are classified taxonomically by the characteristics of their crown, which makes identification of individual columns and columnals difficult unless the crown is attached.

Kingdom AnimaliaPhylum EchinodermataClass Crinoidea

root

column or stalk

columnals

calyx

arms

pinnules

crow

n

Click here for a website on additional Cincinnatian crinoids.

Cincinnaticrinus pentagonus


A

C

B

The columns are circular and have highly rounded edges.

B– cross section of columnal

C– a column made of many columnals

Cupulocrinus polydactylus


A

B

C

A, B, C– the top of the calyx and the lower parts of the arms.

Iocrinus subcrassus


A B

The column is characterized by pentalobate (five lobed) shape.

C, D– cross section of various columnals.

Plicodendrocrinus casei


The aboral cup (calyx) is characterized by having distinctive stellate (star-shaped) pattern of ridges.

A– cross section of columnal

B-- calyx

A

B

Gastropods •Clathrospira subconica

•Cyclonema

•Cyclonema bilix lata

•Cyrtolites ornatus

•Liospira vitruvia

•Loxoplocus bowdeni

•Sinuites cancellatus

•Unidentified #1


Kingdom AnimaliaPhylum MolluscaClass Gastropoda

Exit

The gastropods, or snails, are extremely diverse inhabiting marine, fresh water and terrestrial environments. Their shell can coil in a conical (conispiral) or in in single plane (planispiral).

conch

aperture

apex

conispiral shell

planispiral shell pseudoplanispira

l shell

body whorl

spir

e suture

Clathrospira subconica


A

B

C D

Medium sized and broadly turreted. The largest specimens illustrated here are about 3 cm in width. Conispirally coiled.

Cyclonema


A

B

C

D

E

A gastropod characterized by its fine costae that coil around the shell. 0.5 to 2.5 cm in width. 1 to 2.5 cm in height. Conispirally coiled.

B– view showing aperture (opening in shell)

C– detail showing characteristic fine costae

Cyclonema bilix lata


A BC

This can be distinguished from other species of Cyclonema by its large size, height, and additional whorls. It also has a medial groove in the largest whorl. These two specimens are about 2.5 cm in height. Conispirally coiled.

Cyrtolites ornatus


A

B

C

D

This species may belong to the Monoplacophoran class of mollusks instead of the Gastropoda. Cyrtolites is characterized by its large size, and distinct shell ornamentation. Planispirally coiled.

Liospira vitruvia


A

B

C

A small gastropod, about 1 cm in diameter and 0.3 cm in height. Conispirally coiled, but not in a tall cone.

Loxoplocus bowdeni


A

BC

D

Medium sized, high turreted form with a keel running around the shell. The internal molds of this species is common and usually do not show the keel. D shows the best example of the keel. Conispirally coiled.


Sinuites cancellatus

A

B

C

D

A planispiral gastropod 1-4 cm in diameter. This species may belong to the class Monoplacophora instead of Gastropoda.

Unidentified #1


A B

A small pseudoplanispiral gastropod with distinct ornamentation on its shell (shown in B).

Pelecypods•Ambonychia robusta

•Anomalodonta gigantea

•Caritodens demissa

•Crytodontula umbonata

•Cycloconcha milleri

•Cymatonota typicalis

•Ischyrodonta elongata

•Modiolopsis


Kingdom AnimaliaPhylum MolluscaClass Bivalvia

Exit

This class includes the clams, scallops, mussels and oysters. Pelecypods have a right and left valve which usually separate after death unless the organism is buried alive. The valves are joined together via a hinge and held together by muscles inside the shell. If the valves are symmetrical (and usually they are not) they symmetry will be parallel to the hinge line and not perpendicular to it as in the brachiopods.

posterior adductor muscle scar

anterior adductor muscle scar

right exterior

right interior

pallial line

umbo

right valve left valve

hinge

anterior

posterior

growth line

post

erio

r

ante

rior

Dorsal view

Ambonychia robusta


A

B

C

D

E

One of the most common pelecypods in the Cincinnatian ranging from 3-7 cm in length. This genus is distinguished from Anomalodonta by having much finer radiating costae.

B– molds

Anomalodonta gigantea


A

This is a large pelecypod (as its species name implies) and is characterized by its very coarse costae. Size 7-9 cm in length.

B– internal mold

B

C

Caritodens demissa


A

C

B

D

E

The distinctive characteristics of this pelecypod are its prominent concentric growth lines. This pelecypod is common and can be quite large ranging up to 7 cm in length.

Crytodontula umbonata


A

B

C

A medium to large pelecypod, 3-7 cm in length. Broad prominent beaks.

Cymatonota typicalis


B

A

This pelecypod is characterized by its straight hinge line and lack of any muscle impressions. The shell is very thin and it is rarely seen. This specimen about 9 cm long.

Cycloconcha milleri


AB

A very small pelecypod, about 1 cm in length.

Ischyrodonta elongata


A

B

This species resembles Modiolopsis, but differs from it in the presence of a diagonal ridge (a groove in internal molds) that runs from the beak to the lower margin (shown nicely in Figure B).

Modiolopsis (?)


A

B

C

A medium to large pelecypod. This specimen is about 5 cm in length.

Tentaculitoids


Uncertain taxonomic affinity

Tentaculitoids are a group of extinct marine invertebrates whose taxonomic affinity is uncertain. They are usually small, and conical shaped. Sometimes their shells disarticulate and are found as small rings. Sometimes numerous shells can be found on the same bedding plane, suggesting mass mortalities of the animals.

adul

t (di

stal

) p

art

juve

nile

(pr

oxim

al)

part

apex

ring

annulet

aperture

Tentaculites richmondensis (25 to 30 mm long)

Tentaculites sterlingensis (10 to 15 mm long)

Tentaculites richmondensis


A

Adult specimens are usually 25-30 mm long and 2 to 3 mm wide at the aperture. The shell is often slightly curved. There are 20 to 30 rings in the adult. The rings are not as densely spaced as in Tentaculites sterlingensis.


Tentaculites sterlingensis

The adult specimen is 10 to 15 mm long. The rings are more densely packed than in Tentaculites richmondensis at 20 to 25 rings per 10 mm.

A

B

C

TrilobitesKingdom AnimaliaPhylum ArthropodaClass Trilobita

Trilobites were a bottom dwelling marine arthropod (like crabs), only known from fossils. They often molted as they grew, so their heads and “tails” are often found preserved rather than their entire body.

•Acidaspis cincinnatiensis

•Ceraurinus icarus

•Flexicalymene meeki

•Isotelus gigas

•Isotelus maximus

•Tricopelta breviceps

•Rusophycus pudicum


pygidium (tail)

thorax

cephalon (head)

eye

glabella

genal spine

axial lobe

pleural lobe

Click here for a website on additional Cincinnatian trilobites.

Acidaspis cincinnatiensis


A

A small spiny trilobite which is covered with numerous tubercles. The photo shown is the part of the pygidium (tail) of a small specimen.

Ceraurinus icarus


A

The pygidium of a small Ceraurinus.

Flexicalymene meeki


Flexicalymene is the most common trilobite found in the Cincinnatian. Usually “heads” and “tails” are found because the trilobite molted, shedding its exoskeleton to grow larger in size. Complete specimens can be flat or enrolled. Size ranges from 2 mm up to 6 cm in length. Small enrolled specimens are common and usually “pea” sized as shown in figure B.

B, D, F, G– enrolled specimens

C– flat specimen

E– cephalons or “heads”

A

G

EB

F

C

D

Isotelus gigas


B

A

C

D

Isotelus is one of the largest genera of trilobites known. I. gigas has a sub-triangular shaped cephalon and pygidium and lacks the large genal spines of I. maximus. Specimens can be flat, or enrolled, as shown.

A– the cephalon of an enrolled specimen

B, C, D– views of the cephalon, thorax and pygidium of the same two specimens.

Isotelus maximus


A

D

E

F

B

C

This is the state fossil of Ohio and the most common species of Isotelus. It reached sizes in excess of 50 cm! The pygidium and cephalon are more rounded than that of I. gigas. This trilobite possesses large genal spines which can often be found as broken pieces (E).

A– pygidium of complete enrolled specimen

B– complete specimen (on display at Caesar’s Creek State Park)

C– cephalon of A, note short genal spine

E– a broken genal spine

Tricopelta breviceps


A

B

C

D

A small trilobite, u to 3 cm in length. The eyes are large and the head is covered with numerous tubercles.

A-D– various views of the same enrolled specimen.

Rusophycus pudicum


This is a trace fossil made by a trilobite. These are found on the underside of limestone layers. They were formed from the trilobite digging a hollow in mud which was later filled and covered by calcareous mud that turned into limestone.

A– view from what was the bottom of the burrow.

B– view from what would have been the side of the upside down burrow

A B

Mud with “hollow” dug by trilobite.

Hollow filled with carbonate mud that becomes limestone. This is the part of the rock that is found.

This is a PowerPoint program which can be run by clicking the forward () and backward () arrows on the keyboard. However, it may be more useful to click on the menu links at the top of each page or click on the many photo links to navigate your way through the program. A hand will appear above an active link as you drag the cursor across it. By clicking on you will go back to the last slide viewed. Clicking on will take you to the next slide in the sequence. You can also click anywhere on the page where there is not a link to get to the next slide. Genus and species names are always in italics. The first letter of the genus name will be capitalized. All the letters of a species name will be in lower case. For example, Flexicalymene meeki, a trilobite. To identify a fossil, look at each photo in the category carefully and compare the size of you specimen with those pictured. Look at the notes for helpful hints on distinguishing similar species from each other.

Instructions, Notes, and References• This is not meant to be a comprehensive

guide to all of the fossils found in the Cincinnatian of Ohio. Most of the specimens were collected by the author or his students in the Waynesville, Ohio area. The scale in all of the pictures is in millimeters. All photos are by John Whitmore using a Sony MVC FD73 Mavica.

• Two sources were used to identify the specimens:

– Cincinnati Fossils, edited by R.A. Davis, Cincinnati Museum Center, 1998.

– Fossils of Ohio, edited by Rodney M. Feldmann, Ohio Division of Geological Survey, Bulletin 70, 1996.

• It is not guaranteed that all specimens have been identified correctly, but every attempt was made to do so using the sources above.


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Brachiopods Identification Guide for Common Fossils from the Cincinnatian of Ohio To start, click on...

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