Family Fossil Day - 2007
Family Fossil Day - 2006
Jon A.
Baskin - Texas A&M University-Kingsville
Family Fossil Day - 2007
Family Fossil Day - 2006
John Aguilar: Design for a mural at the John E. Conner Museum
This web page is mainly about fossil mammals from the Pleistocene of South Texas. Some early Pliocene fossils, including the terror bird Titanis are noted below. If you want to learn about the dinosaurs of Texas, try this link.
The Quaternary Period is subdivided into the Pleistocene and Holocene. The Pleistocene or "Ice Age" includes the events from 1.8 million to about 10,000 years ago. The Holocene (or Recent) includes the past 10,000 years. Vertebrate paleontologists designate the late Pleistocene (the past 250,000 years) in North America as the Rancholabrean Land Mammal Age. The type fauna for this age is at Rancho La Brea in California. Learn more about this locality and it fossils from the Museum of Paleontology at UC Berkeley or go directly to the tar pits at the George C. Page Museum and learn more about its fossils and more; or try Ice Age Mammals from the Smithsonian.
The last 100,000 years or so of the Pleistocene are the Wisconsinan glacial age, the last and most extensive episode of Pleistocene glaciation. Wisconsinan glaciers reached their maximum extent 18,000 years ago, a time when continental glaciers extended to central Illinois, Indiana, and Ohio. Although glacial ice was several 1000 kilometers north, the advances and retreats of glaciers during the Pleistocene had dramatic effects on the biota, climate, and geomorphology of South Texas.
During glacial episodes, when sea level fell as much as 120 meters, rivers carved out their valleys and carried sediment to the shoreline which was at the edge of the continental shelf. During interglacials, sea level rose and river and coastal deposition occurred on the continental shelf. Glacial episodes were not times of uniformly falling sea level and erosion of river valleys. During interstadials, relatively warmer intervals, there were minor rises in sea level and the rivers filled in their valleys with terrace deposits. The Beaumont Formation, which underlies the coastal region of Texas, is late Pleistocene in age (approximately 120,000 to perhaps 50,000 years ago). Some authorities believe that the Beaumont was deposited during the last highstand of sea level, the Sangamonian Interglacial (or perhaps the Peorian Interstadial). During the Wisconsinan, the Nueces River carved out its present valley, which is over 30 meters deep and 10 kilometers wide. During the late Wisconsinan interstadials, the five alluvial units that fill the Nueces River Valley formed at progressively lower elevations. These incised terrace and valley fill deposits range in age from perhaps 50,000 to 12,000 years ago. They are capped by Holocene stream deposits of the Holocene flood plain.
South Texas has an excellent record of late Pleistocene fossils. Fossils occur mainly in the river channel and floodplain deposits of the Beaumont Formation and in the terrace deposits cut into the Beaumont Formation. Rancholabrean fossils from South Texas were first described by E. D. Cope over 100 years ago. The majority of fossil mammals from South Texas are grazers, such as horses and mammoths. Grazers live in savannas and grasslands and feed mainly on grasses. They often have high-crowned cheek teeth, in which the enamel extends below the gum line and the roots are frequently open. Browsers are less common. Browsers are typically forest-dwelling animals that feed mainly on stems, twigs, and leaves. Browsers can be recognized by their low-crowned cheek teeth in which the enamel extends to the gum line and the roots are closed. During the Pleistocene, South Texas was a mosaic of grassland and woodland environments which supported a much greater diversity of mammals than at present. There were probably extensive woodlands along the rivers. Time travelers to the Pleistocene of this region might at first glance think they were on the Serengeti Plain of Africa. Extinct fossil species identified from South Texas are listed below.
The Pleistocene was a time of extensive migration between North America and Eurasia and between North and South America. The Isthmus of Panama formed and connected North and South America in the late Pliocene, approximately 2.5 million years ago. During Pleistocene glacial episodes when sea level fell over 100 meters a land bridge formed in what today is the Bering Sea. The Pleistocene fauna of North America is distinct in containing South American immigrants (ground sloths, armadillos, glyptodonts, porcupines, capybaras, and opossums) and Old World immigrants (lions, hyenas, elephants, bison). Some mammals that evolved in North America became extinct on this continent, but survived in South America (llamas and tapirs) and the Old World (cheetahs, camels, horses [including zebras and wild asses], and tapirs).
The extinction of large animals (the
megafauna) in North America at the end of the Pleistocene has been related to climatic
changes and human influences. Lundelius implicates a reduction in habitat diversity caused
by a general warming and drying trend, as well as more seasonal conditions (warmer
summers, colder winters). Martin attributes the extinction to the arrival of big game
hunters (the Clovis and Folsom cultures) across the Bering land bridge 11,500 years ago.
This is known as the overkill hypothesis. Learn more about late Pleistocene
extinctions from the Illinois State Museum. The American Museum of
Natural History has a website devoted to Pleistocene
extinctions world wide. Included is a bestiary
featuring many of the large vertebrates that became extinct, including some from
North America.
Fish
Swift (1968) reported catfishes, freshwater drum, gars, and sunfish from Ingleside (2)
Turtles and tortoises.
†††Hesperotestudo crassiscutata
(1, 2, 3)
The giant Pleistocene tortoise. Presence of this and other large tortoises indicates relatively mild winters. Although considered closely related to the giant Galapagos tortoises, a recent study suggests Hesperotestudo is most closely related to gopher tortoises.
††Gopherus cf. hexagonatus (1, 2)
Gopher tortoises today live in dry areas of the southeastern and southwestern United States. This large, extinct species probably burrowed (Westgate, 1989).
†Trachemys scripta bisornata (1, 2, 3, 4)
The common slider, a wide-spread turtle species that lives in ponds and slow moving streams. This extinct subspecies is considerably larger than recent forms.
Terrapene carolina (1, 2, 4)
The common box turtle.
Kinosternum flavescens (4)
The yellow mud turtle.
Apalone spinifera (1, 2)
The spiny softshell turtle.
Order CROCODILIA
Alligator mississippiensis (1, 2)
The American alligator.
Haliaeetus leucocephalus (1)
Robert Chandler identified a left distal tarsometatarsus as best fitting a large female bald eagle, or possibly a small male golden eagle (Aquila chrysactos).
Fedducia (1973) identified the following birds from the Ingleside Fauna (2)
Podilymbus podiceps. Pied-billed Grebe.
Ciconia maltha. Asphalt Stork.††
Branta canadensis. Canada Goose.
Duck (Genus and species ?)
Anas sp. Teal.
Meleagris gallopavo. Turkey.
Colinus virginianus. Bobwhite.
Limnodromus sp. ?. Dowitcher.
Corvus brachyrhynchos. Common Crow.
The xenarthrans, also known as edentates, are South American mammals that emigrated to North America in the late Cenozoic, especially after the completion of the Panamanian land bridge, approximately 2.5 million years ago.
Sloths are browsers. There are two species of living sloths. Both are relatively small, and spend most of their lives hanging upside down from trees. Most of the extinct sloths were large ground-dwellers. Learn more about ground sloths from the Illinois State Museum. Charles Darwin discovered the remains of ground sloths and other late Pleistocene mammals in Argentina during his sail around the world on the HMS Beagle.
†††Eremotherium laurillardi (?1, 3)
The megatheres include the largest of all the ground sloths. This genus, which ranged from Brazil to South Carolina, was the size of an elephant, with adult males over 6 meters long and weighing more than 3 tons. This species has been associated with savanna habitats. Megatherium from the BBC's Walking with Beasts
†††Paramylodon harlani (1, 2)
This giant ground sloth (sometimes referred to the genus Glossotherium) was a large browser the size an ox and weighed at least one ton.
†††Megalonyx jeffersonii (1, 2)
This ground sloth is the size of a large bear. This species is associated with forest and woodland habitats. The genus was named in 1796 by our third president Thomas Jefferson who thought its "great claw" (megalo- onyx) indicated the fossil was from a giant lion.
Megalonyx skull. Picture by Ronny Thomas.
The cingulates are the armored xenarthrans. They are represented by one extant family, the Dasypodidae (armadillos), and two extinct families (Pampatheriidae and Glyptodontidae). They are represented most frequently in the fossil record by their distinctive osteoderms, the bony plates that form their armor.
†††Holmesina septrionalis (1, 2, 3, 4)
Although pampatheres are sometimes referred to as giant armadillos, it is unclear whether they are more closely related to armadillos or to glyptodonts. A nearly complete specimen, approximately 2 meters long, that was collected in Houston is on display at the Houston Museum of Natural History. More on pampatheres from the American Museum of Natural History.
Holmesina skull. Picture by Ronny Thomas.
†††Glyptotherium arizonae (1, 2, 3, 4)
Glyptodonts were large, slow moving browsers that grew to over 2 meters in length and weighed about a ton. They had a huge turtlelike carapace made up of thick polygonal plates. Although glyptodonts superficially resemble giant armadillos, they are very distinctive, have a long separate fossil record, and belong in their own, distinct family.
††Canis dirus (2, 4)
The dire wolf, a very large Pleistocene wolf.
Canis cf. lupus (1)
The extant grey wolf, not known historically from South Texas.
Canis latrans (2, 5)
The coyote.
Family Mustelidae
Mephitis mephitis (2)
The striped skunk.
††Tremarctos floridanus (?1, 2)
The extinct Florida cave bear is a relative of the South American spectacled bear.
†††Arctodus simus (?1)
The giant short-faced bear, a bear up to twice the size of the brown bear, is tentatively represented by a distal humerus. Information from the Yukon/Beringia interpretive center.
†††Smilodon fatalis (1, 2, 4)
The well-known Pleistocene saber-toothed cat. Both it and the dire wolf are extremely abundant in the tar pits of Rancho la Brea. They are both extremely rare in South Texas. Learn more about Smilodon and other sabertooths from the Illinois State Museum or the Museum of Paleontology at Berkeley. Smilodon from the BBC Walking with beasts.
The root of a Smilodon canine (the light-colored, left half of the photograph) from South Texas superimposed on a picture of a Smilodon canine from Rancho La Brea (the darker, right half). Picture by Ronny Thomas.
The American lion is a large subspecies that grew up to 2.5 m long.
Puma concolor (1, ?2)
The mountain lion or puma has been found in numerous Rancholabrean localities.
Lynx rufus (2)
The bobcat.
Cynomys ludovicianus (1, 2, 5)
The black-tailed prairie dog is no longer present in South Texas.
Family Geomyidae
Geomys sp. (2, 5)
Two gophers, G. cf. attwateri and G. cf. personatus are recognized from Petronila Creek.
Family Hydrochoeridae
†††Neochoerus pinckneyi (3)
This species is 40% larger than the living capybaras, the largest living rodents (which weigh up to 50 kg). This genus, a South American immigrant, was named in a paper describing material discovered on the Aransas River (Hay, 1926).
Elephants and their close relatives.
Occlusal views of a gomphothere, mastodon and mammoth teeth. Click on
image to enlarge.
†††Mammut americanum (1, 2, 3)
The American Mastodont, a browsing form with low crowned teeth, distantly related to elephants is relatively rare in South Texas. The mastodont stood about 2.7 m high at the shoulders. Learn more about the mastodon from the Illinois State Museum. Jacketing a mastodon skull--
--at the Nueces River gravel pit. Click on image to enlarge. Image courtesy of TAMUK News Service
Mastodon molar, side view. Enamel is on the crown only. Click on image to enlarge.
†††Cuvieronius sp. (1, 2, 3)
Gomphotheres are browsing forms, related to elephants. These are also very rare in South Texas.
†††Mammuthus columbi (1, 2, 3, 4)
The Columbian Mammoth is closely related to the Indian elephant. Mammoths are grazers and they are among the most common fossils in South Texas. A full grown, male Columbian mammoth stood 4 meters tall at the shoulder, larger than the 9-11 feet tall wooly mammoth (Mammuthus primigenius). Learn more about mammoths from the Illinois State Museum.
Identifying Pleistocene artiodactyl teeth by David Thulman of the Florida Museum of Natural History.
Although closely related to the Old World swine (Family Suidae), peccaries (or javelina) are easily distinguished from pigs by anyone who cares to tell the difference. More information about living and fossil peccaries including Platygonus can be found at the Florida Museum of Natural History.
†††Platygonus compressus (1, 2, 4)
Platygonus jaw fragment. Picture by Ronny Thomas.The flat-headed peccary was much larger than its living relatives, such as the collared peccary (Pecari tajacu), the official mascot of Texas A&M-Kingsville.
Palaeolama, Hemiauchenia, Camelops. Photograph by Ronny Thomas.
Camels and llamas initially evolved in North America in the late Eocene. In the Pleistocene they emigrated to Asia and Africa (camels) and to South America (llamas) and went extinct in North America.
†††Camelops hesternus (1)
Camelops jaw collected by Jonathan Reichel. Tooth row length is 168 mm. Picture by Ronny Thomas.
This large camel is a giant llama that is known from many Rancholabrean localities including Rancho La Brea. As indicated by its high crowned, but rooted, teeth, it was mainly a grazer, although it probably browsed occasionally. Information from the Yukon/Beringia Interpretive Centre. More information from the La Brea tarpits.
†††Camelops sp. (2, 3, 4)
The Camelops from Ingleside may represent a new species. The material from the other localities is too incomplete to identify to species.
†††Palaeolama mirifica (?1, 2)
This short-legged llama was a browser.
†††Hemiauchenia macrocephala (1)
This gracile llama had very elongate, slender legs and was a cursorial grazer. Learn more about this species from the Florida Museum of Natural History.
Odocoileus virginianus
The white-tailed deer is the only species of large mammal known from the Pleistocene that is still extant in South Texas. It is a browser.
The pronghorn "antelopes" belong to a family that is only known from North America.
†††Capromeryx minor (1, 2)
A diminutive species that weighed about 10 kg, with paired horn cores, a small anterior; one a larger posterior. More information from Rancho la brea.
†††Tetrameryx shuleri (1, 2)
Right horncore. Click on image to enlarge.
This genus includes large four-horned antilocaprids, which have a long posterior horn-core and a shorter anterior horn-core.
†††Stockoceras onusrosagris (1)
A genus the size of the living pronghorn, but with 4 equal sized horns, two above each eye.
Bovids such as the bison (popularly referred to as buffalo - a name that is properly applied to Asian water buffalo) are mainly grazers. This site now requires a password: Laura Cunningham (Volunteer at Death Valley National Park) has a web page developed as part of a Conservation Biology course from Dr. Dick Richardson at the University of Texas, Austin, discussing and illustrating fossil bison.
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A modern female bison skull is at the center for comparison. Behind it are the horn cores of a male Bison antiquus. At the left front is the right skull roof and horn core of a female Bison antiquus. To the left of the skull between the male and female horn cores are pieces of horn cores from Bison latifrons. |
††Bison latifrons (1)
The giant bison had horn cores that spanned up to 2.1 meters.
††Bison antiquus (1, 2, 5)
These bison have horn cores that are larger than the extant B. bison, and can span almost 0.9 meters in an adult male.
Bison sp. (3, 4)
Known only from dentitions. Horn cores are necessary to identify the different species of Bison.
††Tapirus veroensis (1, 2)
Tapirus jaw. Click on image to enlarge.
Tapirs are primitive browsers that occur today in the tropical and subtropical forests of South and Central America (as well as the East Indies), after emigrating from North America during the Pleistocene. They are poorly represented in South Texas.
††Equus spp. (1, 2, 3, 4)
Equus jaw. Click on image to enlarge.
At least three species of Equus (which includes horses, zebras, asses) are present in South Texas in the late Pleistocene (Baskin and Mosqueda, 2002) and are perhaps the most common fossil present.
These grazers are well adapted for living in open country. It is probably impossible to identify species of Equus without relatively complete skulls and skeletons. Laura Cunningham (Volunteer at Death Valley National Park) has a web page developed as part of a class on Conservation Biology from Dr. Dick Richardson at the University of Texas, Austin discussing and illustrating Pleistocene equids.
Baskin (1991) described early Pliocene (about 5 million years old) horses from the Nueces River gravel pits. These horses are reworked from older deposits, presumed to be the upper Goliad Formation. The nearest exposures of the Goliad are approximately 10 km upriver from the sand and gravel pits near Bluntzer, Texas and 25 km from the gravel pit near Odem. Pliocene horses from the gravel pits are Dinohippus mexicanus, Astrohippus stockii, Nannippus aztecus, Pseudhipparion simpsoni, and Neohipparion eurystyle. Other evidence of a latest Hemphillian age of the reworked specimens are rhinoceros tooth fragments and a parts of an edentuluous Rhyncotherium mandible and palate. Rhynchotherium is a four-tusked gomphothere known from the late Clarendonian (late Miocene) through the late Blancan (late Pliocene). The terror bird Titanis is also part of this reworked, early Pliocene fauna.
†††Titanis walleri (1)
A two meter tall, cursorial, flightless, predator. It is distantly related to cranes. A Pliocene immigrant from South America. Titanis is fairly-well known from the late Pliocene (about two million years ago) of Florida. Titanis from Texas is known from a single proximal phalanx. Baskin (1995) considered that it might be late Pleistocene in age, since there is no evidence of two million year old mammals in the fauna and five million years is well before the main pulse of faunal interchange between the Americas. However, Rare Earth Element dating shows that the Texas Titanis is an early Pliocene migrant (MacFadden and others, 2006; 2007).
Titanis toe. Actual length is 90 mm. Click on image to enlarge.
The BBC's Walking with Beasts television program featured the South American ancestor Phorusrhacos. I prefer this restoration over others I have seen. It is even better in the animations on the tv show or on the BBC web page. Here is a more muscular reconstruction from Mineo Shiraishi. More information is available from the FMNH.
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