Tikisuchus
Encyclopedia
Tikisuchus is an extinct genus
of rauisuchid rauisuchian. It is known from the Late Triassic
Tiki Formation
in the Shahdol District
of central India
and was the first rauisuchid to have been found in Asia. The horizon
from which remains have been found is Carnian
in age. The type species
is T. romeri, named in honor of American paleontologist Alfred Romer
. Romer was present at the Tiki locality during the excavation of the fossil, but died before the description of the genus in 1987. Tikisuchus is known only from one specimen, called ISI
R 305, which consists of the skull and some postcranial elements of a young individual.
. The skull is deep, being wide at the back with a narrow rostrum. The teeth are large, recurved and serrated. Like other rauisuchids, it has rows of osteoderm
s, or bony scute
s, along its back. There are two rows of osteoderms. Each osteoderm is rectangular in shape and imbricates, or articulates tightly, with the ones around it. In other rauisuchids, the osteoderms are leaf-shaped rather than rectangular.
, a phytosaur
, Metoposaurus
, a temnospondyl, and Paradapedon, a rhynchosaur
. The Tiki fauna is similar to that of the German
Keuper
.
Theropod dinosaur
s were also present in the Tiki Formation. Both Tikisuchus and the theropods were large terrestrial predators, and, having been found at the same locality, likely came in close contact with one another. The similar lifestyles of the two carnivores may have resulted in competition for the same food sources. Possible prey would have included rhynchosaur
s, trilophosaur
s, dicynodont
s, and aetosaur
s. The authors of the original description of Tikisuchus, Sankar Chatterjee
and Pranab Majumdar, suggested that competition between Tikisuchus and theropods was low because of abundant food resources and stabilized ecological interactions. Chatterjee and Majumdar thought that there was an "ecological balance" during the Carnian stage on the basis of little change in the paleofauna of the time. They considered the paleoclimate to have been warm with seasonal wet and dry seasons conducive to the growth of tropical forests. At the end of the Carnian, however, the authors claimed that many prey resources went extinct and the forest environment was replaced by a more open environment. The limited resources would have heightened competition between theropods and rauisuchians like Tikisuchus. Chatterjee and Majumdar considered theropods to be agile pursuit predators while rauisuchians were considered slow ambush predators. Therefore, they suggested that theropods, which were more suited to living in an open environment, outcompeted rauisuchids at the end of the Triassic to become the dominant large land carnivores by the beginning of the Jurassic. However, more recent studies suggest that dinosaurs gained dominance only after the Triassic-Jurassic extinction event
in a case of opportunism with no other large archosaurs such as rauisuchids to compete with.
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 rauisuchid rauisuchian. It is known from 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...
Tiki Formation
Tiki Formation
The Tiki Formation is a Mesozoic geologic formation. Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.-See also:* List of dinosaur-bearing rock formations...
in the Shahdol District
Shahdol District
Shahdol District is a district of Madhya Pradesh state in central India. With a total area of 5,671 square kilometers and a population of 908,148. Shahdol is an important district of Madhya Pradesh. The town of Shahdol is the district headquarters. The district is also a Division...
of central India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
and was the first rauisuchid to have been found in Asia. The horizon
Soil horizon
A soil horizon is a specific layer in the land area that is parallel to the soil surface and possesses physical characteristics which differ from the layers above and beneath. Horizon formation is a function of a range of geological, chemical, and biological processes and occurs over long time...
from which remains have been found is 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...
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. romeri, named in honor of American paleontologist Alfred Romer
Alfred Romer
Alfred Sherwood Romer was an American paleontologist and comparative anatomist and a specialist in vertebrate evolution.-Biography:...
. Romer was present at the Tiki locality during the excavation of the fossil, but died before the description of the genus in 1987. Tikisuchus is known only from one specimen, called ISI
Indian Statistical Institute
Indian Statistical Institute is a public research institute and university in Kolkata's northern outskirt of Baranagar, India founded by Prasanta Chandra Mahalanobis in 1931...
R 305, which consists of the skull and some postcranial elements of a young individual.
Description
Compared to other rausuchids, the skull of Tikisuchus was very large. The skull's length is around 40% of the length of the presacral area between the head and the sacrumSacrum
In vertebrate anatomy the sacrum is a large, triangular bone at the base of the spine and at the upper and back part of the pelvic cavity, where it is inserted like a wedge between the two hip bones. Its upper part connects with the last lumbar vertebra, and bottom part with the coccyx...
. The skull is deep, being wide at the back with a narrow rostrum. The teeth are large, recurved and serrated. Like other rauisuchids, it has rows of 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, or bony scute
Scute
A scute or scutum is a bony external plate or scale, as on the shell of a turtle, the skin of crocodilians, the feet of some birds or the anterior portion of the mesonotum in insects.-Properties:...
s, along its back. There are two rows of osteoderms. Each osteoderm is rectangular in shape and imbricates, or articulates tightly, with the ones around it. In other rauisuchids, the osteoderms are leaf-shaped rather than rectangular.
Paleobiology
Many other tetrapods were found in association with Tikisuchus representing a diverse Carnian paleofauna. Tetrapods from the Tiki site include PaleorhinusPaleorhinus
Paleorhinus was a genus of small phytosaur, a large order of semi-aquatic, crocodile-like animals that lived in the Late Triassic, specifically the earlier Late Carnian period. The reptiles lived throughout Europe, North America, and North Africa. This genus usually also includes the more...
, a phytosaur
Phytosaur
Phytosaurs are an extinct group of large semi-aquatic Late Triassic archosaurs. Phytosaurs belong to the family Phytosauridae and the order Phytosauria. They were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodiles in size, appearance, and lifestyle, an example...
, Metoposaurus
Metoposaurus
Metoposaurus is an extinct genus of temnospondyl amphibian, known from the Late Triassic of Europe. This mostly aquatic animal possessed small, weak limbs, had sharp teeth and a large flat head. The main diet of this highly flattened creature was fish which it captured with its wide jaws lined with...
, a temnospondyl, and Paradapedon, a rhynchosaur
Rhynchosaur
Rhynchosaurs were a group of Triassic diapsid reptiles related to the archosaurs.-Description:Rhynchosaurs were herbivores, and at times abundant , with stocky bodies and a powerful beak...
. The Tiki fauna is similar to that of the German
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
Keuper
Keuper
The Keuper is a lithostratigraphic unit in the subsurface of large parts of west and central Europe. The Keuper consists of dolostone, shales or claystones and evaporites that were deposited during the Middle and Late Triassic epochs...
.
Theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s were also present in the Tiki Formation. Both Tikisuchus and the theropods were large terrestrial predators, and, having been found at the same locality, likely came in close contact with one another. The similar lifestyles of the two carnivores may have resulted in competition for the same food sources. Possible prey would have included rhynchosaur
Rhynchosaur
Rhynchosaurs were a group of Triassic diapsid reptiles related to the archosaurs.-Description:Rhynchosaurs were herbivores, and at times abundant , with stocky bodies and a powerful beak...
s, trilophosaur
Trilophosaur
Trilophosaurs were lizard-like Triassic diapsid reptiles related to the archosaurs. The best known genus is Trilophosaurus, a herbivore up to 2.5 meters long. It had a short, unusually heavily-built skull, equipped with massive, broad flattened cheek teeth with sharp shearing surfaces for cutting...
s, dicynodont
Dicynodont
Dicynodontia is a taxon of anomodont therapsids or mammal-like reptiles. Dicynodonts were small to large herbivorous animals with two tusks, hence their name, which means 'two dog tooth'...
s, and aetosaur
Aetosaur
Aetosaurs are an extinct order of heavily armoured, medium- to large-sized Late Triassic herbivorous archosaurs. They have small heads, upturned snouts, erect limbs, and a body covered by plate-like scutes. All aetosaurs belong to the family Stagonolepididae...
s. The authors of the original description of Tikisuchus, Sankar Chatterjee
Sankar Chatterjee
Sankar Chatterjee is a paleontologist, and is the Paul W. Horn Professor of Geosciences at Texas Tech University and Curator of Paleontology at the Museum of Texas Tech University. He earned his Ph. D. from the University of Calcutta in 1970 and was a Post-doctoral Fellow at the Smithsonian...
and Pranab Majumdar, suggested that competition between Tikisuchus and theropods was low because of abundant food resources and stabilized ecological interactions. Chatterjee and Majumdar thought that there was an "ecological balance" during the Carnian stage on the basis of little change in the paleofauna of the time. They considered the paleoclimate to have been warm with seasonal wet and dry seasons conducive to the growth of tropical forests. At the end of the Carnian, however, the authors claimed that many prey resources went extinct and the forest environment was replaced by a more open environment. The limited resources would have heightened competition between theropods and rauisuchians like Tikisuchus. Chatterjee and Majumdar considered theropods to be agile pursuit predators while rauisuchians were considered slow ambush predators. Therefore, they suggested that theropods, which were more suited to living in an open environment, outcompeted rauisuchids at the end of the Triassic to become the dominant large land carnivores by the beginning of the Jurassic. However, more recent studies suggest that dinosaurs gained dominance only after the Triassic-Jurassic extinction event
Triassic-Jurassic extinction event
The Triassic–Jurassic extinction event marks the boundary between the Triassic and Jurassic periods, , and is one of the major extinction events of the Phanerozoic eon, profoundly affecting life on land and in the oceans. In the seas a whole class and twenty percent of all marine families...
in a case of opportunism with no other large archosaurs such as rauisuchids to compete with.