Cincinnati Museum Center at Union Terminal is home to several institutions, including the Cincinnati History Museum, Duke Energy Children's Museum, the Museum of Natural History & Science, the Robert D. Lindner Family OMNIMAX Theater and the Cincinnati Historical Society Library.
This tree showcases only 3.6% of the total known fossil biodiversity of the Cincinnati Series. The amazing diversity of organisms preserved in our local rocks is the result of the “Great Ordovician Biodiversification Event”, one of the largest evolutionary events in the history of life on Earth. All of the major types of animals evolved by the end of the earlier Cambrian Period, represented by the major tree limbs in darker color. The Ordovician Period is significant as the time when the main branches of the tree sprouted a multitude of smaller branches in lighter color, representing the evolution of more specialized modifications of each major branch. All the major branches and many of the small branches exist today, but extinction has pruned many smaller branches, and renewed diversification has added branches to the ever-growing tree of life.
<i>Brachiospongia</i> is a highly distinctive fossil sponge. It is a glass sponge, which makes a skeleton consisting of a network of opaline siliceous spicules. Glass sponges occur in deep-water ocean environments today but occupied shallow water marine environments during the Paleozoic Era. All fossil and living hexactinellid sponges are sessile, benthic filter-feeding organisms. <i>Brachiospongia</i> is the largest and most striking sponge in the Cincinnatian Series. This sponge has a hollow central cavity from which radiate 6-12 straight or curved, finger-like projections.
Sponges are not common fossils in the Cincinnatian, although they are often overlooked because they can resemble bryozoans or corals. In the Cincinnatian Series, <i>Brachiospongia</i> occurs in the Kope, Waynesville, and Liberty formations.
Conulariids are a minor group and yet are among the most problematic fossils to be found in the Cincinnatian. They ranged from the Middle Ordovician to the Triassic periods. There are a few cases in which conulariid soft parts have been preserved. Nonetheless, exactly what types of animals they are is still not settled. Primarily on the basis of their four-part structure, conulariids have been classified with scyphozoan cindarians (jellyfish), which also have a four-fold (tetrameral) body plan. Although they are related to jellyfish, they are still unique within this group.
Conulariids had elongated, pyramidal exoskeletons, made up of rows of calcium phosphate rods, resembling an ice cream cone. Most were square or rectangular in cross section. They lived on the sea floor attached to hard objects by means of a stalk, and often lived in groups.
Even though conulariids occur in most strata of the Cincinnatian Series, mostly within Maysvillian and Richmondian strata, they are still quite rare to find.
<i>Orthoceras</i> is a nautiloid cephalopod, which had a straight, cone-like shell. Modern cephalopods include squids, octopuses, and cuttlefishes. These animals could get up to 15 feet in length. Nautiloids flourished during the early Paleozoic era, where they constituted the main predatory animals, and developed an extraordinary diversity of shell shapes and forms. All have shells with nacre and interconnected internal chambers, similar to what we see in the modern <i>Nautilus</i>. Some 2,500 species of fossil nautiloids are known, but only a handful of species survive to the present day.
In the Cincinnatian Sea, <i>Orthoceras</i> would have been the top predator, actively and quickly swimming in the water column with a beak capable of crushing most invertebrates. The soft body lived in the last open-ended segment at the large end of the conical shell. As the body grew and the housing segment became too small, a dividing wall, called the septa, grew to separate the old “home chamber” from the new one.
<i>Orthoceras</i> (now more commonly known as <i>Treptoceras</i>) is common throughout the strata of the Cincinnatian – from the lower Kope Formation up through the Liberty Formation.
Snails are probably one of the easiest fossils to recognize in the Cincinnatian Series. 450 million year old snails look very much like their modern counterparts. In fact, these ancient snails also have similar behaviors to modern snails. While some snails are herbivores and eat plants, other snails are predatory. The evidence of this predatory behavior can be found on the brachiopod shells and other shells that have a tidy, circular hole drilled into them. Predatory snails use their radula, which works like a rasp, to drill a hole in the shell of another animal thereby acquiring dinner.
Snails are very common throughout the Cincinnatian Series. They are generally preserved as molds, with the outer shell matter dissolved away during preservation. There have been 63 species of snails identified in the Cincinnatian.
Specimens of <i>Cyclonema</i> are sometimes found attached to the calyx or body of crinoids. This association between snails and crinoids is one of the best-known cases of interaction between species in the fossil record. In most cases, the snail is positioned over the anal opening of the crinoid, so most paleontologists have concluded that the snail fed upon the digested feces of the crinoid. This association is known as coprophagy.
Specimens of <i>Cyclonema</i> are by far the best-preserved snails of the Cincinnatian because their shells were made of calcite and therefore not dissolved during preservation. Specimens of <i>Cyclonema</i> are found in every formation of the Cincinnatian.
Bivalves are very familiar to us today – clams, mussels, oysters, etc. These animals often find themselves on our dinner plates! Bivalves and brachiopods are often mistaken for the same animals – they both have two valves, and hence, are bivalved. However, the soft tissue anatomy of these animals is remarkably different from each other, resulting in only a superficial similarity. Bivalves are molluscs, related to gastropods and cephalopods, which are united by the presence of a mantle that secretes the shell. Brachiopods do not have mantle tissue. Bivalves acquire food with the use of their gills, while brachiopods have a specialized structure called a lophophore. The symmetry of the valves are also distinct from each other, in brachiopods the plane of symmetry runs across each valve perpendicular to the hinge; in bivalves, the plane of symmetry is between the valves. These, and many other differences, separate these two superficially similar groups into distinct phyla.
A considerable diversity of bivalves has been identified in the Cincinnatian Series, with 164 species identified in the Ordovician rocks of the Cincinnati region. These bivalves are mostly preserved as molds due to the dissolution of their aragonitic shell during preservation. One exception is Caritodens, which has a calcitic shell that is well preserved and easy to identify.
<i>Caritodens</i> can be found throughout most formations in the Cincinnatian Series.
Trace fossils are evidence of the activities of ancient organisms preserved in sedimentary rocks in the form of tracks, trails, burrows, and borings. Trace fossils are also known as ichnofossils, and their study is a branch of paleontology called ichnology. Cincinnatian trace fossils are quite exceptional, and their exquisite preservation has long fascinated scientists. There is a lot that can be learned from these types of fossils, even though the actual animal that made the trace fossil is not preserved. Trace fossils greatly enhance the ability of paleontologists to reconstruct the life and environments of the past.
<i>Diplocraterion</i> is a type of trace fossil known as a domichnia – a permanent dwelling trace formed by a benthic animal. The “U-tube” <i>Diplocraterion</i> is the most common domichnial trace fossil of the Cincinnatian Series. On the upper surface of a rock, this trace appears as a “dumbbell” shape, with two holes connected by a central line. In cross-section, however, the characteristic U-tube shape can be easily recognized. The trace-making organism was probably some type of worm that used the U-tube as its dwelling structure while suspension feeding near the sediment-water interface.
<i>Diplocraterion</i> can be found throughout the Cincinnatian Series, but is most common in the Kope, McMillan, and Waynesville formations. These trace fossils are typically found in siltstones.
Trilobites are an extinct class of arthropod, most closely related to the chelicerate arthropods that today include the horseshoe crabs, spiders, scorpions, tick and mites, amongst others. The name trilobite means “three lobes” and which is often mistakenly assigned to the cephalon (head), thorax, and pygidial (tail regions). Instead, these three lobes refer to the lengthwise subdivisions of the exoskeleton into an axial lobe with a pleural lobe on either side. Although not preserved in the Cincinnatian rocks, paleontologist know from trilobite fossils with exceptional preservation that each of the segments of the animal would house a biramous (two-branched) appendage that consisted of an upper gill branch and a lower walking leg. Over 20,000 species of trilobites have been described, and they existed on Earth for over 200 million years. As a result, trilobites came to occupy most latitudes on Earth, most environments within the ocean, and many different lifestyles – from eating mud to predation on worms, from living in burrows to active swimmers in the water column. Although they all share a basic body plan, their diversity of habit is reflected in their diverse shapes and sizes. At least 16 genera of trilobites are known from the Cincinnatian Series, but most are quite rare.
One of the most sought after fossils in the Cincinnatian Series is a complete <i>Flexicalymene</i> trilobite. These are one of the most well known trilobites in the world, partly because of their abundance in the rocks of this region. Pieces of them are ubiquitous throughout the column of rock, but finding a complete, enrolled specimen, is more challenging even though they occur in almost every formation in the Cincinnatian Series.
As far as trilobites go, <i>Isotelus</i> is special – it is the Ohio State fossil! Pieces of <i>Isotelus</i> can be found quite commonly throughout every formation within the Cincinnatian. It is rare to find a complete <i>Isotelus</i> though– its exoskeleton breaks like an eggshell under compaction of sediments, so even when a complete one is found, it usually needs to have all the pieces put back together again like a complex jigsaw puzzle. <i>Isotelus</i> is also known for its large size. Specimens in this region can reach almost 40 cm in length and a specimen of <i>Isotelus</i> from Churchill, Manitoba, Canada holds the current world record as the largest trilobite at a length of over 70 cm. Based on partial specimens, however, it has been estimated that <i>Isotelus</i> could reach lengths of 80 – 90 cm.
<i>Isotelus</i> was one of the largest known animals in the Cincinnatian Sea – rivaled only by the less common eurypterid <i>Megalograptus</i> and the nautiloid cephalopods. Features of its morphology and ecology point to active predation as the lifestyle of these animals. A large burrow of <i>Rusophycus</i> was discovered and interpreted to have been made by <i>Isotelus</i> based on its large size and morphology – it may preserve the intersection of a worm burrow with the mouth region of the trilobite. The jury is still out in the interpretation – but if this holds true as predation caught in the act, it would be one of the oldest examples of this behavior in trilobites preserved in the fossil record!
One of the most intriguing fossils known from the Cincinnatian is the eurypterid <i>Megalograptus</i>. Eurypterids (also known as sea scorpions) are chelicerate arthropods, distinguished by having the first pair of appendages (chelicerae) equipped with small pinchers. Modern chelicerates include horseshoe crabs, spiders, scorpions, mites and ticks.
<i>Megalograptus ohioensis</i> was one of the largest creatures in the Cincinnatian Sea, reaching a length of over 50 cm. While rare to collect, pieces of <i>Megalograptus</i> can be found in the Waynesville, Liberty, and Elkhorn formations.
Eurypterids first appeared in the Early Ordovician Period and attained their maximum diversity in the Silurian Period, but <i>Megalograptus</i> is significant for being one of the oldest and most unusual. The third appendage is unique in that it is very large and has long spines directed toward the midline. Exactly how the eurypterid used this appendage is uncertain, but it has been hypothesized to have been used as a “basket”, raking up worms and other organisms in the mud that would then be manipulated by the other appendages toward the mouth. Another strange feature is the pair of expanded, hook-like cercal blades at the end of the tail. It is hypothesized that these blades could move in a scissor-like fashion, possibly serving to grasp in either defense or mating.
If you pick up a rock in this region, the most common type of fossil you will find in the Cincinnatian Series is most likely a bryozoan. Bryozoans come in all shapes and sizes – lumps, gumdrops, thin crusts - but the twig-like morphology is most commonly found. They are often mistaken for bones or coral, but they are neither.
Modern bryozoans exist, and their features help paleontologists understand the structure of their fossil counterparts. Bryozoan colonies are covered in tiny holes called zooecia, and within each hole lived a minute animal called a zooid. A characteristic feature of zooids is the lophophore, a ring of tentacles that surrounds the mouth and serves as a food gathering structure. Another phylum within the Cincinnatian bears the same structure – the Phylum Brachiopoda. Sometimes the preserved remains of an animal can be very deceiving. Although very different in shape from the outside, the fact that both bryozoans and brachiopods share this feature – which unites them into a group called the lophophorates – means that they share a close evolutionary relationship.
Bryozoans are active filter feeders. They spread their tentacles of their lophophore into a funnel or bowl-like configuration to catch tiny bits of organic matter suspended in the water. They can generate their own feeding currents for the entire colony – to bring food matter toward them and carry waste away from the colony.
<i>Constellaria</i> is named for the constellations of star-shaped bunches of monticules. Monticules are regularly spaced bumps on the outer surface of the colony and were the places where currents that moved away from the colony were generated.
Within the Cincinnatian Series, <i>Constellaria</i> is most commonly found with the Fairview, Waynesville, Liberty, Whitewater, and Elkhorn formations.
It is challenging to pick up a rock in this region and not find a brachiopod in it. This is because brachiopods are one of the most common, and diverse, fossils in the Cincinnatian Series. There are even some rock layers that are made up of exclusively brachiopod shells. Even though they have been around for over 500 million years, we don’t think of brachiopods much today because they are no longer a large component of modern marine ecosystems. Back during the Ordovician Period however, they were one of the dominant groups. They are often confused with clams (bivalves) because they share the two-valved body plan. But that is where the resemblance ends.
Brachiopods are lophophorates – they share a feeding structure, called a lophophore, with another abundant group in the Cincinnatian – the bryozoans. It has been estimated that brachiopods and bryozoans constitute approximately 60% of the fossils in our limestones. Even though brachiopods and bryozoans look very different in overall appearance, this shared feature highlights their shared evolutionary history.
Brachiopods are benthic animals. They can either lie on the seafloor or attach to the substrate by means of a fleshy stalk called a pedicle. When they feed, they open their valves and extract small particles of organic matter from the seawater with their lophophore – a ciliated structure with a pair of tubular “arms” that occupy most of the interior cavity of the animal. The beating of the cilia brings water into the inside of the shell, where particles are trapped and transported along a food groove, and then back out again.
<i>Rafinesquina</i> is perhaps the most common, and one of the largest, brachiopods in the Cincinnatian Series. Recent research suggests that these brachiopods were capable of snapping their shells together, much like a modern scallop, in order to escape burial beneath sediments on the seafloor.
<i>Rafinesquina</i> is found in nearly every formation of the Cincinnatian Series.
<i>Platystrophia</i> is one of the more sought after brachiopods for collectors. It has many different shapes depending on the environment it lived – from more delicate smaller forms with “wings” at the end of the shell, characteristic of deeper quieter environments, to more robust and large forms with strong ribs that are found in shallower environments with high wave energy. <i>Platystrophia</i> is also one of the more diverse genera of brachiopods, with 24 different species found throughout the Cincinnatian Series.
<i>Lingula</i>, now called <i>Pseudolingula</i>, is often referred to as a “living fossil”. Despite the 450 million years that separates them, the modern representative <i>Lingula</i> is very similar to the Ordovician <i>Pseudolingula</i>, implying that these organisms occupy a life habit that is very stable over long periods of time. Based upon modern examples, the life habits of <i>Pseudolingula</i> can be easily inferred. These animals live in burrows in the sea floor, with the opening of the shell at or near the sea floor and the pedicle pointing down into the sediment.
<i>Pseudolingula</i> is an inarticulate brachiopod. Articulate brachiopods, like <i>Rafinesquina</i> and <i>Platystrophia</i> for example, have interlocking teeth and sockets on the inside of the hinge that create a locking mechanism to articulate the two valves together (hence the name “articulate” brachiopod). Unlike articulate brachiopods, inarticulate brachiopods do not have a structural shell mechanism to keep the two valves together. Only muscles serve this function. Interestingly, inarticulate brachiopods have no anus. Instead of a one-way digestive tract found in articulate brachiopods, it is more of a cul-de-sac. Waste material, in the form of small pellets, has to be sent back out through the mouth. Inarticulate brachiopod shells are also typically made of calcium phosphate, a different material from calcium carbonate found in articulate brachiopods.
<i>Pseudolingula</i> can be found in the Kope, Fairview, Arnheim, and Waynesville formations of the Cincinnatian Series.
Graptolites are among the most distinctive fossils in the Cincinnatian, and are also uniquely significant. They first appear in the Middle Cambrian and became extinct in the Pennsylvanian Period. During their time in the Paleozoic, they are used the basis of relative age dating and correlation of rocks worldwide. They are commonly preserved in mudstones as “black pencil marks”.
Graptolite fossils are the preserved skeletal sheaths of a colonial, soft-bodied marine organism whose soft parts are not preserved. The soft part structure of these animals remains unknown. The skeleton housed many graptolite animals, called zooids, within each cup-like theca. Graptolite colonies existed as free-floating plankton or as branching, benthic colonies. The sheath consists of the protein collagen, the same material that makes our hair and nails! The identification of this protein in graptolites indicates an affinity with chordates in which collagen forms the connective tissue. Therefore, within the Cincinnatian sea, our closest evolutionary relatives are the graptolites!
Within the Cincinnatian Series, <i>Geniculograptus</i> can be found in the Kope and Fairview formations.
Edrioasteroids are one of the most common echinoderm fossils in Cincinnatian strata, and they are unique in form among the group. They first appear during the Cambrian Period and become extinct in the Permian Period. At first glance, an edrioasteroid resembles a sea star with a ring around it (the name means “seated star”). The sea star resemblance comes from the five curving food grooves on the upper surface. Most Cincinnatian edrioasteroids have a low dome shape, although some can be cylindrical.
Because edrioasteroids are extinct, their mode of life must be inferred by analogy to living echinoderms. Edrioasteroids are always found attached to a hard surface – often a brachiopod shell, a bivalve shell, or a hardground. Living on the back of somebody else may have helped raise the low profiled edrioasteroid above the muddy sea bottom for feeding. Some cemented to this hard surface permanently, while others may have adhered by means of a basal membrane, and therefore may have been capable of limited movement. In either case, the mouth and food grooves were directed upwards in order to filter feed small particles from the water column.
The “Official City of Cincinnati” fossil is an edrioasteroid – <i>Isorophus cincinnatiensis</i>! Declared in 2002 by Mayor Charles Luken after a selection vote by the public at Cincinnati Museum Center’s Nature’s Trading Post. The fact that we have an official city fossil is a testament to the significance of our local rocks and fossils to the natural history of this region.
Although edrioasteroids are often considered rare fossils, when they are found they can occasionally occur as populations of hundreds or thousands. Within the Cincinnatian Series, <i>Carneyella</i> can be found in the Kope, Fairview, McMillan, Arnheim, Waynesville, Liberty, and Whitewater formations.
Crinoids are the most abundant and diverse of all the echinoderms in the Cincinnatian Series. Like modern echinoderms, such as starfish and echinoids (sand dollars), crinoids possess five-fold (pentameral) symmetry, have skeletons made up of numerous plates, and the lack of a blood circulatory and respiratory system. Crinoids are often confused with plants – they look like plants in overall shape, and many of the terms used to describe their morphology are plant-like terms – roots, stems, etc. Even their generic name, the sea lily, belies their animal affinities. But they are indeed animals!
Stemmed crinoids are attached to the sea floor by a holdfast, or root, structure and elevated above the sea floor by a stem made up of many “donut-shaped” columnals. The body is enclosed within a plated calyx. The arms arise from this calyx and contain many smaller pinnules, giving the arms a feather-like appearance. The arms and pinnules function in food gathering, capturing and transporting many tiny particles to the mouth of the animal situated on the upper surface of the calyx. Living crinoids are passive suspension feeders. They put their arms out into currents that supply food particles and wait for them to filter through. Tiny tube feet grab the particles and pass them to a food groove for transport to the mouth. The close similarity of Ordovician forms and modern forms suggests that ancient crinoids used a similar feeding method.
Because crinoid bodies are made up of many plates, upon death and the decay of soft tissue that once held these plates together, crinoids become disarticulated and their individual plates are often scattered. Crinoid columnals, the plates that make up the stem, are among the most common fossil in the Cincinnatian. Twenty-eight species of crinoids are known from the Cincinnatian Series.
<i>Ectenocrinus</i> is one of the most common crinoids in the Cincinnatian Series. Disarticulated columnals from the stem can form entire limestone beds. Sometimes articulated stems are packed together tightly in “logjams” which probably formed during ancient storms that disrupted the sea floor and concentrated these remains.
<i>Ectenocrinus</i> is found in the Kope and Fairview formations of the Cincinnatian Series.
Starfish (also known as sea stars) are quite rare as fossils in the Cincinnatian Series. The oldest known fossil starfish is from the Early Ordovician Period, extending into the modern as an important predator in today’s marine communities. They are one of the most recognizable echinoderms – having the characteristic 5-fold symmetry – yet they are often preserved fragmentary or distorted in the Cincinnatian so they are not that easy to find.
An extraordinary specimen of a Promopalaeaster wrapped around a bivalve provides a rare example of predation caught in the act! It also shows that sea stars in the Ordovician had the ability to pry open bivalve valves, just as modern sea stars do. The prey is then digested within its own shell by the sea star’s everted stomach.
<i>Promopalaeaster</i> is the best-known Cincinnatian sea star, and although rare, is found throughout Cincinnatian strata.