Thecachampsa
Encyclopedia
Thecachampsa is an extinct genus
of tomistomine
crocodilian. Fossils have been found from the eastern United States
in deposits that are late Oligocene
in age. The type species
is T. antiqua. Several other species have been erected. Those named in the 19th century were distinguished primarily by the shape of their teeth, and have since been combined with T. antiqua. More recently erected species were reassigned from other tomistomine genera, although their assignment to Thecachampsa has since been questioned. The holotype
of T. antiqua is an isolated tooth of little diagnostic value, making the assignment of any other body parts to the genus, including skulls and vertebrae, questionable.
s, it had a long, slender snout. The teeth were long and recurved. Unlike its living relatives, Thecachampsa was marine, inhabiting estuaries and shallow coastal waters. Other marine fossils such as sea snail
and bivalve shells, shark
teeth, and barnacle
s have been found alongside remains of Thecachampsa and similar tomistomines.
, who referred to it as Crocodylus antiquus in the Journal of the Academy of Natural Sciences of Philadelphia. The holotype, which served as the basis for Leidy's first description, was a tooth found in the Calvert Formation of Virginia
. Leidy also described additional material including several teeth and osteoderm
s, two vertebrae, a rib, and an ungual
phalanx or claw bone. On the basis of these specimens, the new genus Thecachampsa was erected by Edward Drinker Cope
in 1867.
Crocodilian material found from Miocene deposits in the eastern United States has often been attributed to Thecachampsa, even isolated teeth with few distinguishable features. In 1867, Cope named two new species of Thecachampsa: T. contusor (occasionally misspelled T. contusa) and T. sericodon. T. sericodon was distinguished from T. antiqua by its slender, curved teeth, each with a sharp edge near the base of the posterior margin (T. antiqua only possessed sharp edges along a small area near the tip of the posterior margin). In 1869, Cope named a fourth species, T. sicaria, from a jaw fragment and a dorsal vertebra. Unlike those of other species, the teeth of T. sicaria were lenticular (lens-shaped) in cross section with sharp cutting edges. That year, Othniel Charles Marsh
named another species of Thecachampsa, T. squankensis, after the place of its discovery, Squankum
, New Jersey
. Cope named a new species, T. fastigiata, in 1870 as a reassignment of Crocodylus fastigiatus, named by Leidy in 1852. American geologist William Bullock Clark
of the Maryland Geological Survey named a fifth species, T. marylandicus, in 1895. These species were distinguished from one another primarily by differences in the shape of the teeth, the most common material found. The genus was synonymized with Crocodylus
in 1973, but has since been regarded as valid.
In 2001, A.C. Myrick synonymized Gavialosuchus americanus, another tomistomine from the eastern United States, with T. antiqua. Myrick also synonymized Tomistoma lusitanica
, a tomistomine from Portugal
, with Thecachampsa. The genus name Thecachampsa had priority over the other two, as it was erected earlier. However, because the holotype tooth of T. antiqua has no clear diagnostic features to distinguish it from other tomistomines, later studies did not accept the synonymies. Piras et al. (2007) considered G. americanus to be a member of the genus Thecachampsa, but placed it as a distinct species, T. americanus, rather than a synonym of T. antiqua. The species was first described as Tomistoma americanus in 1915, with remains having been found from the Kirkwood Formation in New Jersey
, the Calvert Formation in Maryland
, the Chesapeake Group of Virginia
, and the Pungo River and Yorktown Formation
s of North Carolina
. Remains have also been found from Florida
, California
, Baja California
, and, more recently, Costa Rica
. Fossils of the species are present in deposits that range in age from the late Early Miocene
to the early Pliocene
. More recent studies such as that of Jouve et al. (2008) have kept the species within Gavialosuchus, leaving T. antiqua as the only species within Thecachampsa.
In addition to reassigning G. americanus and G. carolinensis to Thecachampsa, Myrick combined all previously named species of Thecachampsa with the type species T. antiqua. The different tooth shapes that distinguished the species were considered variation in the dentition of a single species. However, the variation in dentition could only be seen in complete tomistomine skulls, all of which had been referred to Gavialosuchus before the genus was synonymized with Thecachampsa.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of tomistomine
Tomistominae
Tomistominae is a subfamily of crocodylians that includes one living species, the False gharial. Many more extinct species are known, extending the range of the subfamily back to the Eocene epoch...
crocodilian. Fossils have been found from the eastern United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
in deposits that are late Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
in age. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
is T. antiqua. Several other species have been erected. Those named in the 19th century were distinguished primarily by the shape of their teeth, and have since been combined with T. antiqua. More recently erected species were reassigned from other tomistomine genera, although their assignment to Thecachampsa has since been questioned. The holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
of T. antiqua is an isolated tooth of little diagnostic value, making the assignment of any other body parts to the genus, including skulls and vertebrae, questionable.
Description
Thecachampsa, like other tomistomines of the Oligocene and Miocene, was considerably larger than living crocodilians. Like living gharialGharial
The gharial , , also called Indian gavial or gavial, is the only surviving member of the once well-represented family Gavialidae, a long-established group of crocodilians with long, slender snouts...
s, it had a long, slender snout. The teeth were long and recurved. Unlike its living relatives, Thecachampsa was marine, inhabiting estuaries and shallow coastal waters. Other marine fossils such as sea snail
Sea snail
Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....
and bivalve shells, shark
Shark
Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....
teeth, and barnacle
Barnacle
A barnacle is a type of arthropod belonging to infraclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosive settings. They are sessile suspension feeders, and have...
s have been found alongside remains of Thecachampsa and similar tomistomines.
Species
The type species of Thecachampsa, T. antiqua, was first described in 1852 by American paleontologist Joseph LeidyJoseph Leidy
Joseph Leidy was an American paleontologist.Leidy was professor of anatomy at the University of Pennsylvania, and later was a professor of natural history at Swarthmore College. His book Extinct Fauna of Dakota and Nebraska contained many species not previously described and many previously...
, who referred to it as Crocodylus antiquus in the Journal of the Academy of Natural Sciences of Philadelphia. The holotype, which served as the basis for Leidy's first description, was a tooth found in the Calvert Formation of Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
. Leidy also described additional material including several teeth and osteoderm
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
s, two vertebrae, a rib, and an ungual
Ungual
An ungual is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and other ungulates have ungual phalanges, as did the sauropods and horned dinosaurs. A claw is a highly modified ungual phalange.As an adjective, ungual means related to nail, as in periungual .-External...
phalanx or claw bone. On the basis of these specimens, the new genus Thecachampsa was erected by Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
in 1867.
Crocodilian material found from Miocene deposits in the eastern United States has often been attributed to Thecachampsa, even isolated teeth with few distinguishable features. In 1867, Cope named two new species of Thecachampsa: T. contusor (occasionally misspelled T. contusa) and T. sericodon. T. sericodon was distinguished from T. antiqua by its slender, curved teeth, each with a sharp edge near the base of the posterior margin (T. antiqua only possessed sharp edges along a small area near the tip of the posterior margin). In 1869, Cope named a fourth species, T. sicaria, from a jaw fragment and a dorsal vertebra. Unlike those of other species, the teeth of T. sicaria were lenticular (lens-shaped) in cross section with sharp cutting edges. That year, Othniel Charles Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
named another species of Thecachampsa, T. squankensis, after the place of its discovery, Squankum
Williamstown, New Jersey
Williamstown, home of brandon ciarlante, is a census-designated place and unincorporated area located within Monroe Township, in Gloucester County, New Jersey...
, New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
. Cope named a new species, T. fastigiata, in 1870 as a reassignment of Crocodylus fastigiatus, named by Leidy in 1852. American geologist William Bullock Clark
William Bullock Clark
William Bullock Clark, Ph. D., LL.D , was an American geologist.He was born at Brattleboro, Vermont, and educated at Amherst College and in Munich...
of the Maryland Geological Survey named a fifth species, T. marylandicus, in 1895. These species were distinguished from one another primarily by differences in the shape of the teeth, the most common material found. The genus was synonymized with Crocodylus
Crocodylus
Crocodylus is one of three genera from the Crocodylinae subfamily extending from the Crocodylidae family.Established species include three extinct species:* † Crocodylus acer - probably represents a distinct genus....
in 1973, but has since been regarded as valid.
In 2001, A.C. Myrick synonymized Gavialosuchus americanus, another tomistomine from the eastern United States, with T. antiqua. Myrick also synonymized Tomistoma lusitanica
Gavialosuchus
Gavialosuchus is an extinct tomistomine from the late Oligocene and Miocene of eastern North America and early Miocene of Europe. Three species have been named: the type species G. eggenburgensis from the early Miocene of Austria; G. americanus, from the late Miocene to early Pliocene of Florida;...
, a tomistomine from Portugal
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...
, with Thecachampsa. The genus name Thecachampsa had priority over the other two, as it was erected earlier. However, because the holotype tooth of T. antiqua has no clear diagnostic features to distinguish it from other tomistomines, later studies did not accept the synonymies. Piras et al. (2007) considered G. americanus to be a member of the genus Thecachampsa, but placed it as a distinct species, T. americanus, rather than a synonym of T. antiqua. The species was first described as Tomistoma americanus in 1915, with remains having been found from the Kirkwood Formation in New Jersey
New Jersey
New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...
, the Calvert Formation in Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, the Chesapeake Group of Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
, and the Pungo River and Yorktown Formation
Yorktown Formation
The Yorktown Formation is a mapped bedrock unit in the Coastal Plain of Maryland, Virginia, North Carolina and South Carolina. It is overconsolidated and highly fossiliferous.-Description:...
s of North Carolina
North Carolina
North Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
. Remains have also been found from Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
, California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
, Baja California
Baja California
Baja California officially Estado Libre y Soberano de Baja California is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is both the northernmost and westernmost state of Mexico. Before becoming a state in 1953, the area was known as the North...
, and, more recently, Costa Rica
Costa Rica
Costa Rica , officially the Republic of Costa Rica is a multilingual, multiethnic and multicultural country in Central America, bordered by Nicaragua to the north, Panama to the southeast, the Pacific Ocean to the west and the Caribbean Sea to the east....
. Fossils of the species are present in deposits that range in age from the late Early Miocene
Early Miocene
The Early Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Aquitanian and Burdigalian stages....
to the early Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
. More recent studies such as that of Jouve et al. (2008) have kept the species within Gavialosuchus, leaving T. antiqua as the only species within Thecachampsa.
In addition to reassigning G. americanus and G. carolinensis to Thecachampsa, Myrick combined all previously named species of Thecachampsa with the type species T. antiqua. The different tooth shapes that distinguished the species were considered variation in the dentition of a single species. However, the variation in dentition could only be seen in complete tomistomine skulls, all of which had been referred to Gavialosuchus before the genus was synonymized with Thecachampsa.