Uatchitodon
Encyclopedia
Uatchitodon is an extinct genus
of Late Triassic
reptile
known only from isolated teeth. Based on the structure of the teeth, Uatchitodon was probably a carnivorous archosauromorph
. Folded grooves on the teeth indicate that the animal was likely venomous, with the grooves being channels for saliva
ry venom
. The teeth are similar to those of living venomous squamates such as Heloderma
and venomous snake
s. Uatchitodon is the earliest known venomous reptile.
in the journal Nature
in 1991. U. kroehleri is known from several teeth found from the early middle Carnian
Turkey Branch Formation of the Newark Supergroup in Virginia
, uncovered from the Tomahawk locality. The teeth average around 10 mm in length. The tooth crown is strongly labiolingually compressed, recurved, and serrated along both the anterior and posterior edges. The serrations are formed from individual denticles, each of which is further denticulated. On both the labial (outer) and lingual (inner) surfaces of the tooth, there is a deep central groove running longitudinally. The grooves form deep invagination
s that constrict the inner pulp cavity
of the tooth. The grooves do not reach the tip of the tooth.
A single tooth from the Petrified Forest Formation
of the Late Triassic
Chinle Group, found at the Placerias Quarry at St. Johns, Arizona
, has been identified as one of Uatchitodon. It is slightly younger than the teeth of U. kroehleri found in Virginia. Venom-conducting teeth were first noted from the Placerias Quarry in the 1980s, but they were not interpreted as belonging to Uatchitodon until 1992. The tooth, known as MNA
V3680, differs from those of U. kroehleri in that the grooves are fully enclosed and form tubes within the teeth. There are faint furrows at the sutures that enclose these tubes. The tubes, which are presumably venom canals, end at discharge orifices near the tip of the crown. MNA V3680 is the earliest example of a tetrapod
with completely enclosed tooth canals for the delivery of oral toxins, which are seen today in elapid snakes.
MNA V3680, along with several other teeth from the Cumnock Formation near Raleigh, North Carolina
, represent a second species of Uatchitodon, U. schneideri. This species, although recognized since 1996, remained unnamed until 2010. U. schneideri was named in honor of Vince Schneider of the North Carolina Museum of Natural Sciences
. The holotype tooth, known as NCSM
24753, was found from a locality referred to as NCPALEO 1906, along with many other teeth and uncatalogued fragments. NCPALEO 1906, better known as the Moncure microvertebrate locality, was discovered and excavated by Schneider.
The teeth from the Moncure locality are similar to MNA V3680 in that they all have enclosed venom canals that open at the ends of the teeth. The teeth of U. schneideri can be distinguished from those of U. kroehleri by enclosure of the canals as well as a lesser degree of labiolingual compression.
s. The teeth of U. kroehleri in the Tomahawk locality are older than those of U. schneideri in the Moncure locality and Placerias quarry, suggesting that the grooved teeth of U. kroehleri developed into the tubular fangs of U. schneideri. A similar transition is thought to have occurred in snakes. The earliest venomous snakes appeared in the Miocene
epoch with fully formed tubular fangs, but there is no fossil evidence of earlier snakes with grooved teeth. In the development of living venomous snakes, however, the fangs have open grooves before erupting. One they emerge from the gum line, the fangs have enclosed canals.
The grooves of U. kroehleri may indicate that it had a lifestyle similar to the living gila monster, chewing prey to pass venom into it. With enclosed canals, U. schneideri may have been able to inject venom in a similar way to venomous snakes. Like venomous snakes, it may have been able to pump venom into its prey through venom glands and compressor muscles. However, as the jaws of U. schneideri are not known, there is no evidence for such glands or muscles.
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 Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...
known only from isolated teeth. Based on the structure of the teeth, Uatchitodon was probably a carnivorous archosauromorph
Archosauromorpha
Archosauromorpha is an infraclass of diapsid reptiles that first appeared during the late Permian and became more common during the Triassic. Included in this infraclass are the groups Rhynchosauria, Trilophosauridae, Prolacertiformes, Archosauriformes, and, tentatively, Choristodera...
. Folded grooves on the teeth indicate that the animal was likely venomous, with the grooves being channels for saliva
Saliva
Saliva , referred to in various contexts as spit, spittle, drivel, drool, or slobber, is the watery substance produced in the mouths of humans and most other animals. Saliva is a component of oral fluid. In mammals, saliva is produced in and secreted from the three pairs of major salivary glands,...
ry venom
Venom
Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...
. The teeth are similar to those of living venomous squamates such as Heloderma
Heloderma
Heloderma, the only genus of the family Helodermatidae, consists of venomous lizards native to the southwestern United States, Mexico and as far south as Guatemala. It includes two separate species, with six subspecies...
and venomous snake
Snake
Snakes are elongate, legless, carnivorous reptiles of the suborder Serpentes that can be distinguished from legless lizards by their lack of eyelids and external ears. Like all squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales...
s. Uatchitodon is the earliest known venomous reptile.
Description and species
The genus was first named with the description of the type species U. kroehleri by Hans-Dieter SuesHans-Dieter Sues
Hans-Dieter Sues is a German-born paleontologist who is Senior Scientist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC. He received his education at Johannes Gutenberg-Universität Mainz , University of Alberta, and...
in the journal Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
in 1991. U. kroehleri is known from several teeth found from the early middle Carnian
Carnian
The Carnian is the lowermost stage of the Upper Triassic series . It lasted from about 228.7 till 216.5 million years ago . The Carnian is preceded by the Ladinian and is followed by the Norian...
Turkey Branch Formation of the Newark Supergroup in 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...
, uncovered from the Tomahawk locality. The teeth average around 10 mm in length. The tooth crown is strongly labiolingually compressed, recurved, and serrated along both the anterior and posterior edges. The serrations are formed from individual denticles, each of which is further denticulated. On both the labial (outer) and lingual (inner) surfaces of the tooth, there is a deep central groove running longitudinally. The grooves form deep invagination
Invagination
Invagination means to fold inward or to sheath. In biology, this can refer to a number of processes.* Invagination is the morphogenetic processes by which an embryo takes form, and is the initial step of gastrulation, the massive reorganization of the embryo from a simple spherical ball of cells,...
s that constrict the inner pulp cavity
Pulp (tooth)
The dental pulp is the part in the center of a tooth made up of living connective tissue and cells called odontoblasts.- Anatomy :Each person can have a total of up to 52 pulp organs, 32 in the permanent and 20 in the primary teeth....
of the tooth. The grooves do not reach the tip of the tooth.
A single tooth from the Petrified Forest Formation
Petrified Forest National Park
Petrified Forest National Park is a United States national park in Navajo and Apache counties in northeastern Arizona. The park's headquarters are about east of Holbrook along Interstate 40 , which parallels a railroad line, the Puerco River, and historic U.S. Route 66, all crossing the park...
of the Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
Chinle Group, found at the Placerias Quarry at St. Johns, Arizona
St. Johns, Arizona
St. Johns is the county seat of Apache County, Arizona, United States. It is located along U.S. Route 180, mostly west of where that highway intersects with U.S. Route 191. According to 2006 Census Bureau estimates, the population of the city was 3,538....
, has been identified as one of Uatchitodon. It is slightly younger than the teeth of U. kroehleri found in Virginia. Venom-conducting teeth were first noted from the Placerias Quarry in the 1980s, but they were not interpreted as belonging to Uatchitodon until 1992. The tooth, known as MNA
Museum of Northern Arizona
The Museum of Northern Arizona is a museum in Flagstaff, Arizona, USA, that was established as a repository for Native American artifacts and natural history specimens from the Colorado Plateau.The museum was founded in 1928 by zoologist Dr. Harold S...
V3680, differs from those of U. kroehleri in that the grooves are fully enclosed and form tubes within the teeth. There are faint furrows at the sutures that enclose these tubes. The tubes, which are presumably venom canals, end at discharge orifices near the tip of the crown. MNA V3680 is the earliest example of a tetrapod
Tetrapod
Tetrapods are vertebrate animals having four limbs. Amphibians, reptiles, birds and mammals are all tetrapods; even snakes and other limbless reptiles and amphibians are tetrapods by descent. The earliest tetrapods evolved from the lobe-finned fishes in the Devonian...
with completely enclosed tooth canals for the delivery of oral toxins, which are seen today in elapid snakes.
MNA V3680, along with several other teeth from the Cumnock Formation near Raleigh, North Carolina
Raleigh, North Carolina
Raleigh is the capital and the second largest city in the state of North Carolina as well as the seat of Wake County. Raleigh is known as the "City of Oaks" for its many oak trees. According to the U.S. Census Bureau, the city's 2010 population was 403,892, over an area of , making Raleigh...
, represent a second species of Uatchitodon, U. schneideri. This species, although recognized since 1996, remained unnamed until 2010. U. schneideri was named in honor of Vince Schneider of the North Carolina Museum of Natural Sciences
North Carolina Museum of Natural Sciences
The North Carolina Museum of Natural Sciences is located in Raleigh, North Carolina. This museum is the oldest established museum in North Carolina and the largest museum of its kind in the Southeast...
. The holotype tooth, known as NCSM
North Carolina Museum of Natural Sciences
The North Carolina Museum of Natural Sciences is located in Raleigh, North Carolina. This museum is the oldest established museum in North Carolina and the largest museum of its kind in the Southeast...
24753, was found from a locality referred to as NCPALEO 1906, along with many other teeth and uncatalogued fragments. NCPALEO 1906, better known as the Moncure microvertebrate locality, was discovered and excavated by Schneider.
The teeth from the Moncure locality are similar to MNA V3680 in that they all have enclosed venom canals that open at the ends of the teeth. The teeth of U. schneideri can be distinguished from those of U. kroehleri by enclosure of the canals as well as a lesser degree of labiolingual compression.
Paleobiology
The tubular venom canals of U. schneideri are similar to those found in the teeth of venomous snakes, while the grooved teeth of U. kroehleri are similar to those of living gila monsterGila monster
The Gila monster is a species of venomous lizard native to the southwestern United States and northwestern Mexican state of Sonora...
s. The teeth of U. kroehleri in the Tomahawk locality are older than those of U. schneideri in the Moncure locality and Placerias quarry, suggesting that the grooved teeth of U. kroehleri developed into the tubular fangs of U. schneideri. A similar transition is thought to have occurred in snakes. The earliest venomous snakes appeared in the Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
epoch with fully formed tubular fangs, but there is no fossil evidence of earlier snakes with grooved teeth. In the development of living venomous snakes, however, the fangs have open grooves before erupting. One they emerge from the gum line, the fangs have enclosed canals.
The grooves of U. kroehleri may indicate that it had a lifestyle similar to the living gila monster, chewing prey to pass venom into it. With enclosed canals, U. schneideri may have been able to inject venom in a similar way to venomous snakes. Like venomous snakes, it may have been able to pump venom into its prey through venom glands and compressor muscles. However, as the jaws of U. schneideri are not known, there is no evidence for such glands or muscles.
External links
- Uatchitodon in the Paleobiology DatabasePaleobiology Database' is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms.-History:The Paleobiology Database was founded in 2000. It has been funded by the National Science Foundation and the Australian Research Council...