Paleoecology of the Waynesville Formation (Cincinnatian, Upper Ordovician) of Southeastern Indiana

College of Wooster Invertebrate Paleontology Class Investigation, Fall 2000

The Waynesville Formation exposed at Stop #3 of the September 2000 Invertebrate Paleontology field trip. Such a grey, rainy day for such a grey, muddy outcrop. Note that compared to the other outcrops in this project, the Waynesville is not very resistant to erosion. This is because it has a low limestone to claystone ratio. See the project pages for the overlying Liberty and Whitewater Formations.

The Waynesville Formation Student Team

Jerome Hall is a junior geology major from Louisville, Kentucky. He is studying the Waynesville strophomenid brachiopods.

Rich Poole is a sophomore from Estes Park, Colorado. His responsibilities include the Waynesville trilobites, gastropods and bivalves.

Laura Long is a junior geology major from Brockport, New York. She is assessing the Waynesville bryozoans.

Daniele Davies is a junior geology major from Centreville, Virginia. Her duties include the Waynesville orthid brachiopods.

The Waynesville Trilobites, Gastropods and Bivalves
(by Rich Poole)

This is an excellent internal mold of one of our many gastropod specimens. The spiral coiling is very well preserved and the detail is very good; however, because it is a mold, we're not looking at the actual shell of this organism.

The distribution of bivalves in our fauna, Waynesville formation, was generally rare. Bivalves are typically epifaunal and infaunal filter feeders. One feature that separates bivalves from other similar organisms like brachiopods is their innate ability to dig and become infaunal, but this is not terribly important until the Mesozoic time period because of the Mesozoic Marine Revolution. Bivalves posses a two-valved shell that is an aragonitic concretion and bilaterally symmetrical. Bivalves are dorsally hinged with a hatchet shaped foot and lack a head and radula. Bivalves are much less abundant than many other organisms in the fauna we collected, particularly brachiopods.

It was difficult to classify this specimen beyond the large classification Class Bivavlvia. This was due to the mode of preservation of the specimen, which, was an internal mold. The internal mold preserved the detail of the shell ridges well, but does not show the dentition which would be a powerful tool for proper identification. This internal mold only shows one of the valves so it is hard to determine if the valves were equilateral or not. This bivalve is representative of bivalves in this period because at this point bivalves hadn't flourished and are primarily rare to common in abundance.

Trilobites in the Waynesville formation were represented by fragments, and were fairly abundant. Trilobites are primarily vagrant benthic deposit feeders; however, there is some evidence that they may have been predatory digging through the sediment in search of live food not just innate organic material. Trilobite morphology is distinguished by their three lobes. Trilobites have two pleural lobes and an axial lobe in the center. Trilobites are arthropods which means "joint foot," and have an interesting evolutionary trend: going from agnostids which had no eyes, to redlichiids that had a huge cephalon and small thorax, and then phacopids which had a large proportional body even in relation to the thorax. All of the trilobites we found were represented by fragments that had been scattered in the assemblages. The representative fragments we found demonstrate primarily phacopid trilobites. The fragments were all unaltered hard parts and easy to identify with their rusted earth brown color still intact. The abundance's were actually extremely abundant fragments, they were just all over the place, but it would have been nice to find a nice mold of a whole trilobite, they were found in other formations of the Ordovician. Overall we found abundant fragments of the Order Phacopida in the Waynesville formation.

This is an unaltered hard part remain of trilobite, probably from the pygidium and merely demonstrates that trilobites did exist in this assemblage.

With this gastropod test, unaltered hard parts, note the exceptional detail seen in this specimen and the wholeness of the preservation providing a very good look at the casing of this mollusk.

The distribution of gastropods in the Waynesville formation was actually fairly abundant. We primarily found Archeogastropods and Mesogastropods, because Neogastropods didn't arise until the Cretaceous and Waynesville is in the Ordovician. These gastropods are generally herbivorous, deposit feeders, but some Mesogastropods were carnivorous. Gastropods had many different variations of radula: ptennoglossate the "comb teeth" used for grazing substrate, rachiglossate the "drill teeth" used for drilling into hard substrate like shells and such. Gastropods moved about with a large dorsal muscle called the "foot."

Many types of preservation were exhibited in our specimens. We have many internal molds, and a few unaltered hard parts that were cemented to the solidified sediments. We found specimens of Order Archeogastropoda and Order Mesogastropoda under the Subclass Prosobranchia. These gastropods generally have a spirally coiled, asymmetrical shell. They usually have a twisted "torted" body, a distinct head, a mouth and radula "teeth", and one or two pairs of tentacles. Gastropods were more abundant than bivalves, but less abundant than brachiopods. They weren't the dominant organisms in this formation, but they were definitely successful and enjoyed plentiful numbers in population. Overall the gastropods in our formation could be seen as common or even nearly abundant.

 

The Waynesville Bryozoans
(by Laura Long)

Parvohallopora subnodosa; notice the pronounced maculae.
 Bryozoans are often superficially mistaken for corals, because they are also colonial organisms. However, there are several distinctions. The bryozoans, while they also live in colonies, have much tinier holes for the zooids (individual bryozoan animal) than a coral would. The zooid holes are pin sized, while in a coral they would be easily visible. Bryozoans require clear water, since they are filter feeders easily disturbed by turbidity with their small size. They are most abundantly found on rocky bottoms, sheltered crevices and inside the shells of other invertebrates. At times during the Paleozoic they were the second or third most abundant fossil group.

In the Waynesville formation, there were several different species found. These included:

Batotomata gracilis - abundant
Batotomata varians - abundant
Homotrypella hospitalis - common
Rhombotrypa quadrata - rare
Parvohallapora subnodosa - common

Batostomella gracilis with the short angle between branches and small apertures typical of the species, producing a smooth, tree-like look.

Batostomata varians, the diaphragms that divided the zooids can be seen clearly in the broken branches.
 There were also two fossil specimens from the Order Fenestrata, although their specific species type remains unknown. The bryozoans in the Waynesville formation had filled the filter feeding niche of the area. The colonial substrate building species were quite common, while the encrusters were few. There was plenty of shelf or bottom space that was in low turbidity for the colonies to build upon.

 

The Waynesville Strophomenid Brachiopods
(by Jerome Hall)

An excellent example of a Rafinesquina brachiopod. Its shape and structure are typical of the Strophomenid group. Notice the distinct cardinal dentition, as well as the cancavo-convex shape of the shell.
 The Strophomenid brachiopods group are very common within the Waynesville Formation. Very common as far as the entire brachiopods group is concerned, the Strophomenids are found as only two species with this formation, Rafinesquina and Strophomena planumbona. Both are sessile benthic filter-feeding brachiopods, attached to a substrate and filtering the water flow for nutrients. Though both are within the Strophomenid brachiopods group, each has unique morphological features and form. The formation is dominated by the common Rafinesquina, while Strophomena planumbona is relatively uncommon within the unit.

Strophomena planumbona is a brachiopod which is characterized by its convexo-concave morphological form. Within this form, the dorsal valve of the brachiopod overides the slightly-less angled concave ventral valve. With a highly strophic hinge line and costae ("weak-ribbed") commissure, this brachiopod is typical of the Strophomenid group.

Strophomena planumbona is seen here. Though uncommon in this unit, this particular example is very well preserved. Notice the cancavo-convex form, as well as the lack of cardinal dentition or internal features found on Rafinesquina. Also, notice the encrusting bryozoan located on the shell.

Another well-preserved Rafinesquina brachiopod. The cardinal dentition stands out on this sample, as well as the internal features of the brachiopod. The size of the sample is typical of the strophominids found at this site.
 Rafinesquina brachiopods generally look very similar to the previous species. Both have highly strophic hinge lines and costae commissure. The main morphological differences come from Rafinesquina's internal features as well as its differing concavo-convex form. The internal features are the easiest guide to identifying the Rafinesquina from its brethern. Distinct cardinal dentition at the joint of the hinge line are characteristic of this group.

 

The Waynesville Orthid Brachiopods
(by Daniele Davies)

Figure 1
Phylum Brachiopoda
Class Articulata
Order Orthida
Hebertella occidentalis
 Brachiopods are solitary animals that secrete a dorsal valve and a ventral valve around their soft bodies and lophophores. The ventral valve is characterized by the pedicle openning, teeth, adductor muscle scars, and diductor muscle scars; the dorsal valve is characterized by sockets (holes for the teeth at the posterior of the valve), cardinal process (knob where diductor muscles attached behind hinge), brachidium, and adductor muscle scars. Articulate brachiopods have calcitic shells, a hinge system, no anus, and simple musculature (adductors and diductors).

Orthid brachiopods are considered to be the most primitive of the articulate brachiopods. They lived from the Lower Cambrian and nearly went extinct during the Late Ordovician, but managed to survive until the Permian. Orthid brachiopods were epifaunal sessile benthic organisms with biconvex shells that are strophic (have a long hinge line) and usually plicate with a distinct interarea. They required a hard substrate onto which they would attach their large pedicle in order to position themselves in the current to maximize the flow through their lophophore for feeding and to remove wastes.

Figure 2
Phylum Brachiopoda
Class Articulata
Order Orthida
Platystrophia clarksvillensis

Figure 3
Phylum Brachiopoda
Class Articulata
Order Orthida
Onniella meeki
 Hebertella occidentalis was among the most common of the articulate brachipods during the Ordovician. Their distinguishing feature is a triangular pedicle openning and a relatively flat ventral valve (see Figure 1). Platystrophia clarksvillensis is characterized by three equally strong plications in the median sinus and by having only eight or nine plications on either side of the sulcus (see Figure 2). Figure 3 shows Onniella meeki, which is characterized for its rectangular outline, greater size, and greater thickness. Also shown in this photo is a tentaculid (to the upper right of the orthid), which is an extinct group of conical tube-shaped molluscs that lived during the same time as the orthid brachiopods.

 

The Waynesville Formation Paleoecology
(by the Waynesville Team)

The ancient paleoenvironment of the Waynesville Formation is characterized by its large populations of bryozoans and brachiopods. The dominant feeding strategy of the location was epifaunal filter-feeding. This mode of feeding was especially successful in the clear and shallow waters below wave base. The paleofacies is evident due to the concentration of fauna requiring shallow waters and low turbidity, such as brachiopods and bryozoans. The Waynesville Formation had remarkably few corals, implying that the environment was not necessarily in the photic zone. The substrate was a mixture of both hard and soft sediments, as the bryozoans required a hard substrate (possibly brachiopod shells) and soft sediment for the large populations of strophomenids. The fauna was dominated by bryozoan and brachiopod communities, with a significant lack of corals and other organisms. Scattered throughout our fauna were fairly common abundances of gastropods and plentiful trilobite remains, but with no full specimens. This leads to the conclusion that gastropods and trilobites were present in the environment, but were not dominant. In conclusion, the Waynesville Formation was defined as a shallow, low-turbidity marine environment located below the wave base, that was dominated by epifaunal filter-feeders.

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