Vertebrate Fossils

From Ohio History Central

Fossil vertebrates (Phylum Chordata) are relatively rare fossils, although diligent searching can turn up highly prized specimens. Many fossil vertebrate remains are so rare, and scientifically important, that it is recommended that collectors contact the nearest university geology department, museum, or the Ohio History Connection. Ohio has an important record of fossil vertebrates that in some cases has characterized life in that particular point in geologic history.

FOSSIL FISHES

Agnathans

The earliest known fish-like animals appeared in the Cambrian Period. By the Ordovician Period, a diverse fauna of jawless, bottom-feeding, armored fishes were present in nearshore marine environments. These fishes belonged to a group known as Agnatha (jawless). Although remains of agnathans have been found in many areas of the world in Ordovician rocks, none have been in Ohio rocks representing this time period. Perhaps Ohio was too far offshore for these fishes at that time. Agnathan remains are unknown from Ohio Silurian rocks as well.

However, remains of Agnathan fishes are known from a unique deposit of Early Devonian age that was discovered in a quarry in northwestern Ohio in the 1920’s. Numerous specimens of agnathan fishes were found in a thin, laterally discontinuous bed of shale that represented a small, brackish-water embayment of the sea. No similar deposits have been discovered in Ohio . Microscopic turbercles that may have been from agnathan fishes have been found in the Middle Devonian Columbus Limestone. The group became extinct in the Devonian.

Acanthodians

Acanthodians were among the earliest fishes with jaws and are found in Silurian through Permian rocks. Their fragmentary remains are found in Devonian, Mississippian, and Pennsylvanian rocks in Ohio . These remains consist of shiny, rhomboid-shaped scales and fin spines. Fin spines of a comparatively large acanthodian, Machaeracanthus, are found in the Columbus Limestone.

Placoderms

Placoderms were armored fishes and among the early jawed fishes. They were a diverse group and some reached very large sizes, perhaps nearly 20 feet in length. They first appeared in the Silurian and were extinct by the end of the Devonian. Remains of placoderms are well known from some Devonian rocks in Ohio .

Placoderms had a series of thick, interlocking, bony plates that protected the head and thorax. The remainder of the skeleton was cartilaginous and rarely preserved. The bony jaws did not have teeth but the jawbones were modified to function like teeth with sharp spikes, shearing blades, or crushing surfaces. Many placoderms were active predators. One of the largest, Dunkleosteus terrelli, is estimated to have a bite force greater than any fossil or living fish and among the most powerful of any animal.

Placoderm remains consisting of head shields of Macropetalithys, are found in Middle Devonian rocks in Ohio . However, the greatest abundance and diversity of placoderm remains are known from the Upper Devonian Ohio Shale and particularly the Cleveland Shale Member of this unit in the Cleveland area. Most of these placoderm remains are found in large carbonate concretions but some bones are found in the shale. The Cleveland Museum of Natural History has a large collection of these specimens and many are on display.

Sharks

Sharks are fishes with cartilaginous skeletons and are only rarely are they completely preserved. Most often, their teeth, fin spines, and microscopic scales are found. Shark remains are present in Devonian, Mississippian, and Pennsylvanian marine rocks, and remains of freshwater sharks are found in Pennsylvanian and Permian rocks. They were a diverse group in the Late Paleozoic and adapted not only for feeding on other fishes but many species had crushing teeth adapted to feeding on shelled invertebrates. These teeth are moderately abundant in some Pennsylvanian marine rocks in eastern Ohio .

Teeth and scales of sharks are found in the Columbus Limestone. The Upper Devonian Cleveland Shale Member of the Ohio Shale, in the Cleveland area, has produced concretions that yield exquisitely preserved remains of one of the earliest sharks, Cladoselache. Soft parts of the sharks are preserved, including muscle tissues.

Bony Fishes

Bony fishes (Osteichthyes) include most of the fishes living today and are divided into the ray-finned fishes, lobe-finned fishes, and lungfishes. Remains of all three groups are represented by fossils in Ohio Paleozoic rocks.

The Columbus Limestone of Middle Devonian age yields fossils of a large lobe-finned fish, Onychodus sigmoides, which was up to six feet in length. Most of these fossils consist of large, sharp-pointed, recurved teeth that were positioned in the front of the jaws. Occasionally, entire jaws are found. The Cleveland Shale Member of the Ohio Shale produces complete remains of small bony fishes known as palaeoniscoids. They are covered by shiny, ornamented, rhomboid-shaped scales. Microscopic scales of palaeoniscoids are found in later Paleozoic marine and non-marine rocks in the state as well as complete specimens in a few unique localities, including the world-famous Pennsylvanian-age, nonmarine, cannel coal deposit known as Linton, in Jefferson County . Teeth of lungfish have been found in non-marine rocks of Pennsylvanian and Permian ages in eastern Ohio . Remains of bony fishes similar to or identical to living fishes are found in lake and pond deposits formed during the Pleistocene Ice Age.

AMPHIBIAN FOSSILS

Amphibians, familiar to most people as frogs, toads, and salamanders, first appeared at the end of the Devonian Period. None have been found in Devonian or Mississippian rocks in Ohio , primarily because these rocks are marine. However, Pennsylvanian and Permian rocks have produced many fossil amphibians. Although these remains are very rare in most of these rocks, a few remarkable localities have yielded an abundant and diverse fauna that in many respects has served as the model for life of the coal swamps prevalent at this time.

Most notable is a locality known as Linton, in Jefferson County . Waste rock from a coal mine active in the 1800’s, represents sediment deposited in a coal-swamp lake, perhaps an oxbow lake, that teemed with fishes, including paleoniscoids, lungfishes, and freshwater sharks, and many species of amphibians and even early reptiles. At least 22 species of amphibians are known from Linton. Most were small, aquatic forms. One frog-like form, Amphibamus lyelli, probably was primarily terrestrial. A more recently discovered locality in a strip mine in Mahoning County has yielded 13 species of amphibians, most of which are known also from Linton. Pennsylvanian non-marine rocks have yielded occasional footprints and trackways of amphibians.

Permian rocks have produced rare amphibian remains, most of which are poorly preserved. Included in these remains is a large amphibian, Eryops that was up to three feet long. Specimens of a bizarre amphibian with a banana-like head, Diploceraspis, are known from two localities in southeastern Ohio .

REPTILE FOSSILS

Reptile remains in Ohio ’s Upper Paleozoic rocks are very rare and generally poorly preserved. The Linton locality (see Amphibians), despite more than a century and a half of collecting, has produced only three species of reptiles represented by a total of 10 specimens. A few fragmentary remains have been reported from Upper Pennsylvanian rocks in eastern Ohio .

Permian rocks have been a bit more productive for reptile remains but they are scattered and fragmentary. Perhaps the most characteristic reptile remains from these rocks are isolated skeletal elements of the sail-backed, mammal-like reptiles, Dimetrodon and Edaphosaurus. Both were comparatively large reptiles with large, fan-shaped sails on their backs. These structures are thought to have been used to control body temperature. Dimetrodon was carnivorous whereas Edaphosaurus was herbivorous. Remains of turtles and snakes have been found at a few Pleistocene sites in Ohio .

DINOSAUR FOSSILS

Without question, the best-known and most popular fossil organisms are the dinosaurs. Many people wonder if dinosaurs have been found in Ohio or lived in Ohio . During the Mesozoic Era, when dinosaurs and other reptiles were the dominant forms of life, Ohio was above sea level as an upland land mass. Undoubtedly, dinosaurs roamed the Ohio land but erosion, rather than deposition was the dominant geologic force. Dinosaur remains that may have been entombed in lake or river sediments were destroyed during the 300-million-year long interval of erosion that removed huge amounts of rock. Therefore, unless an isolated deposit of Mesozoic rocks is discovered in Ohio , no dinosaur remains will ever be found in the state.

BIRD FOSSILS

Birds first appeared during the Mesozoic and are derived from dinosaurs. However, as Ohio does not have rocks from the Mesozoic, nor from the Paleogene and Neogene Periods of the Cenozoic Era, fossils of birds are known in the state from sediments deposited during the latter part of the Pleistocene Ice Age. These are rare fossils with only a few specimens having been found. These include turkey, Meleagris gallopavo, the claw of a hawk, duck, and possibly Canada goose. Bird bones are very delicate and easily destroyed by weathering and easily overlooked except in excavations where sediments screened for small bones.

MAMMAL FOSSILS

Mammals first appeared during the Triassic Period and lived with dinosaurs during the Mesozoic Era. At the beginning of the Cenozoic Era, after extinction of the dinosaurs about 65 million years ago, mammals flourished and diversified. However, similar to the Mesozoic Era, Ohio was an upland land mass and erosion removed large quantities of rock. It is probable that mammals roamed Ohio just as had the dinosaurs but no rocks, and therefore no mammal remains from the Paleogene and Neogene Periods are preserved in the state. It was not until the Pleistocene Ice Age that remains of mammals were entombed and preserved in sediments.

Most, if not all, mammal remains from Pleistocene sediments in Ohio represent the last part of the Ice Age (Wisconsinan) and many sites yield radiocarbon dates that place them very near the end of the Ice Age (10,000 years ago) when glacial ice had been gone from the state for several thousand years. Most of the fossil-bearing deposits represent former glacial lakes and ponds that are now swampy areas. Excavation of these deposits sometimes yields large bones that are easily recognized as unusual. Isolated teeth, tusks, and bones are commonly picked up along streams and rivers in sand and gravel deposited as outwash of from melting glaciers. These specimens are commonly broken and water worn. The best specimens and the greatest faunal diversity are from deposits preserved in caves and sinkholes. Only one such deposit is known from Ohio , although they are abundant in other states with better development of caves.

It would be surprising to many people to learn that of the 40 species of mammals known from Ohio ’s Pleistocene deposits, 29 species still survive in North America Of these, 21 species still live in the state. A significant extinction event at the end of the Ice Age selectively removed large mammals, collectively known as the megafauna.

Without question the most significant and well-known extinct Ice Age animal found in Ohio was the American mastodon, Mammut americanum. Although most specimens consist of isolated teeth or tusks, a number of nearly complete specimens have been found. Several are on display at museums in the state, including the famous Conway mastodon displayed at the Ohio History Connection. Mastodons were elephant-like animals that were sturdily built browsers of open spruce forests. Adults stood about nine feet high at the shoulder and they weighed between four and five tons. Their cone-shaped teeth are distinctive. Most complete specimens have been found in the sediments of former glacial lakes where they broke through the ice in winter or became bogged down in mud. Some specimens show evidence of having been butchered by Paleoindians.

Mammoths were elephants that are related to the modern Indian elephant. They were more slimly built than mastodons and were primarily grazing animals more common to grasslands. Although mammoth remains are not uncommon in Ohio , they are decidedly less common than are the remains of mastodons. Two species of mammoth have been recognized in Ohio : Mammuthus primigenius, the northern mammoth, and Mammuthus columbi, a more southerly species. Both mastodons and mammoths became extinct about 10,000 years ago.

A large and bizarre animal that inhabited Ohio during the Pleistocene and became extinct at the end was the ground sloth. These ox-sized animals migrated northward from South America during the Ice Age and are occasionally found in bog deposits in Ohio . They had large, strong front legs with claws that were used to obtain vegetation.

Remains of horses, mostly isolated teeth and jaws, that lived in Ohio during the Pleistocene have been found occasionally. Remains of a tapir, another southern migrant, have also been found.

Bones of an extinct, pig-like peccary species, Platyogonus compressus, have been reported from several sites in Ohio , including nearly complete specimens. Excavations at Indian Trail Caverns in Wyandot County, produced remains of at least 39 individual peccaries.

Cervalces scotti, sometimes called the stag-moose or elk-moose, is known from several specimens from Ohio . A nearly complete specimen was collected in Stark County and is on display at the Ohio History Connection. These animals were similar in size and characteristics to the modern moose but their antlers differed.

Two species of musk ox lived in Ohio during the Ice Age, although fossils of either species are uncommon. Bootherium bombifrons is an extinct species. Ovibos moschatus still survives in northern climates.

One specimen of the giant-horned bison, Bison latifrons, is known from southwestern Ohio . The horns of this specimen measure about six feet from tip to tip. Specimens of modern bison, Bison bison, have been reported from presumed Pleistocene deposits.

Specimens of deer (Odocoileus virginianus), caribou (Rangifer tarandus), and elk (Cervus elaphus). Have been found in deposits that are late Pleistocene or early Holocene. Two fairly complete elk skeletons from Ohio have been radiocarbon dated to about 9,000 years old, suggesting that elk, which survived in Ohio until historic times, may have been an early migrant into the state after extinction of the megafauna.

Fossil remains of large carnivores are generally less common than remains of herbivores because of lesser abundance of the predators. Fragmentary remains of the short-faced bear, Arctodus simus, were found at Indian Trail Caverns and a skull of a grizzly bear, Ursus arctos, was found in Butler County . So far, fossils of the saber-toothed cat, Smilodon fatalis, and dire wolf, Canis dirus, have not been found in Ohio but it is likely that both species lived here because their remains have been found in nearby states. The small number of Pleistocene cave sites in Ohio probably accounts for lack of a fossil record of these animals in Ohio .

The giant beaver, Castoroides ohioensis, is comparatively well known from Ohio ’s Pleistocene sediments, with 15 specimens recorded. This black-bear sized rodent looked similar to modern beaver, Castor canadensis, but was much larger. It has been suggested that giant beaver did not build dams or gnaw on trees, but fed on aquatic vegetation. The first known and described specimen of giant beaver (type specimen) was found near Nashport, Muskingum County, and was illustrated in 1838 by the first Geological Survey of Ohio. Specimens of giant beaver fossils are displayed at the Ohio History Connection.

In addition to modern beaver, Pleistocene sediments in Ohio have produced remains of small mammals such as shrews, bats, red squirrel, tree squirrel, voles, and field mice. Medium-sized mammals include woodchuck, porcupine, muskrat, weasel, pine marten, fisher, mink, skunk, red fox, raccoon, and river otter. Most of these remains have come from cave or bog sites that have been systematically excavated.

See Also

References

  1. Hansen, M. C., 1996. "Phylum Chordata--Vertebrate Fossils," in Fossils of Ohio, edited by R. M. Feldmann and Merrianne Hackathorn. Ohio Division of Geological Survey Bulletin 70, p. 288-369.