Phytosaur
Encyclopedia
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 crocodile
s in size, appearance, and lifestyle, an example of convergence
or parallel evolution
. The name "phytosaur" (plant reptile) is very misleading, and their snapping jaws clearly show that phytosaurs were predators. The person who first described them mistakenly thought the specimens he was working with were plant-eaters (Jaeger 1828).
Although phytosaurs were not true crocodilians themselves, they were more closely related to the crocodilians than to other modern reptiles, as phytosaurs are basal
members of the clade Crurotarsi
. Crocodiles did not become superficially 'phytosaur'-like until the Early Jurassic
.
Phytosaurs had a nearly global distribution during the Triassic. Fossils have been recovered from Europe
, North America
, India
, Morocco
, Thailand
, and Madagascar
. Fossils attributed to phytosaurs have been found in Early Jurassic rocks, possibly extending their temporal range beyond the Triassic-Jurassic boundary.
The phytosaur skull was characterized by three distinct morphotypes, which relate to feeding and habits and not (as was once thought) evolutionary relationships. These skull patterns are linked to characteristics of the dentition; specifically the differentiation or similarity of the teeth along the jaws.
Dolichorostral ("long snouted") types have a long, slender snout and a large number of conical teeth that are the same throughout. These were most likely piscivorous
, able to capture fast slippery prey, but not so good at tackling a land animal. Some examples are Paleorhinus
, Rutiodon carolinensis, and Mystriosuchus
. At one time it was believed that Paleorhinus and Mystriosuchus belonged to a distinct group of phytosaurs (subfamily of family Mystriosuchinae/Mystriosuchidae Huene, 1915) characterised by this adaptation, but it is now known that Mystriosuchus is actually more closely related to Pseudopalatus
, an "altirostral" form (Hungerbühler, 2002).
Brachyrostral ("short snouted") forms are the opposite, they have a massive, broad snout, and a very strong skull and jaws, with the front teeth like fangs for holding the prey, and the rear teeth blade-like for slicing the meat into chunks that can easily be swallowed (an animal with different types of teeth like this is called heterodont
). These were powerful animals specialised for feeding on strong struggling prey, such as terrestrial animals that come to the water to drink. Examples of this type are Nicrosaurus
and Smilosuchus
Altirostral ("high snouted") animals are intermediate between the two. They had heterodont dentition but not as extremely developed as the brachyrostral type. Angistorhinus
and Pseudopalatus are typical examples here. These were most likely generalist feeders.
Modern crocodilians exhibit a similar morphological diversity, for example the broad snouted altirostral alligator
and the long snouted dolichorostral gavial.
Phytosaurs were even better armoured than crocodiles, protected by heavy bony scute
s (often found as fossils), and the belly reinforced with a dense arrangement of gastralia
(abdominal ribs).
structure is much more primitive than that of any crocodile. Also, phytosaurs lack the bony secondary palate
that crocodiles have that enables them to breathe even when the mouth is full of water. It is possible however that phytosaurs had a fleshy palate, as many Mesozoic crocodiles are presumed to have had. Finally, and most noticeably, phytosaurs had nostrils placed near or above the level of the eyes, in contrast to crocodiles where the nostrils are near the end of the snout. This adaptation may have developed to allow them to breathe while the rest of the body was submerged.
' s teeth, William L. Abler also examined a phytosaur's teeth, finding that it had had serrations so fine that they resembled a crack in the tooth. Albertosaurus
had similarly crack-like serrations, but, at the base of each serration Abler discovered a round void
which would have functioned to distribute force over a larger surface area
. This void, termed an ampulla, would hinder the ability of the "crack" formed by the serration to propagate through the tooth. The phytosaur was found to lack adaptation
s for preventing its dental "cracks" from propagating. Abler examined another sort of prehistoric predator, Dimetrodon
, and found that it lacked adaptations for guarding against crack propagation as well.
When the first phytosaur fossils were found, it was not immediately obvious what kind of animal/species they were. The first phytosaur species known to science was named Phytosaurus cylindricodon - "plant lizard with cylindrical teeth" - by G. Jaeger in 1828 because he mistakenly believed that petrified mud fillings in the jaw were herbivore teeth. The specimen is too poor to be diagnostic, and this species name is no longer valid. The name of the group - Phytosauria - was coined by the German paleontologist Hermann von Meyer in 1861, on the basis of this first species.
The next species to be described was Belodon plieningeri by von Meyer in von Meyer and Plieninger 1844. The altogether more appropriate name Parasuchia ("alongside the crocodiles", as they resembled crocodiles to a great degree) was coined by Thomas Huxley
in 1875 along with his discovery and naming of the Indian species Parasuchus hislopi (Chatterjee, 1978), on the basis of a partial snout. The specimen also is usually considered non-diagnostic, and the name Parasuchus replaced by Paleorhinus
. Although the names Parasuchidae and Phytosauridae are variously still used by different specialists, "phytosaur" is the standard generic name for these animals, despite the fact that these animals have been clearly shown to be carnivorous
.
Phytosaurs first appear during the Carnian
age, evolving from an unspecified crurotarsan ancestor. There are no clear intermediate forms, as the first phytosaurs found were already fully formed and highly specialised.
The earliest phytosaurs belong to the primitive and comparatively unspecialised but very widely distributed genus Paleorhinus. A somewhat more advanced and larger form, Angistorhinus appears at the same time or soon after. Later in the Carnian, both these animals were replaced by more specialised forms like Rutiodon
, Leptosuchus
, and the huge Smilosuchus
(Lucas 1998). The Carnian-Norian extinction meant that these animals died off, and the Early Norian
sees new genera like Nicrosaurus
and Pseudopalatus, both of which belong to the most derived clade of phytosaurs, the Pseudopalatinae
. Later in the middle Norian the advanced and specialised fish-eater Mystriosuchus appears. Fossil remains of this widespread animal is known from Germany, northern Italy, and Thailand. Finally the large Redondasaurus
in south-west North America and the long-snouted (altirostral) Angistorhinopsis ruetimeyeri in Europe continued the group into the Rhaetian
. Phytosaur footprints (the ichnotaxon
Apatopus) are also known from the latest Rhaetian of the East Coast of USA (the Newark Supergroup) (Olsen et al. 2002). This indicates that phytosaurs continued as successful animals until the very end of the Triassic, when, along with many other large crurotarsan reptiles, they were killed off by the end Triassic extinction event
.
There have been reports of phytosaur remains found in lowermost Jurassic rocks. A fragment of a lower jaw from a longirostrine archosaur has been described from early Hettangian
strata in the town of Watchet
in Somerset
, England. While teleosaurid thalattosuchia
ns had similar longirostrine jaws to phytosaurs and were common in the Jurassic, they do not appear in earliest Jurassic rocks. The mandible is more similar to those of known phytosaurs than to thalattosuchians, and likely belongs to a phytosaur closely related to the genus Mystriosuchus. The presence of phytosaurs in the earliest Jurassic may have prevented thalattosuchians from occupying similar ecological niches until after their disappearance.
of archosaurs that includes crocodilians and their extinct relatives. Phytosaurs are often excluded from a clade called Suchia
, which usually encompasses all other crurotarsans, including aetosaur
s, rauisuchia
ns, and crocodylomorphs. Some studies have found polytomies
between phytosaurs and other groups like Ornithosuchidae
and Suchia. In these cases, it is unclear whether phytosaurs are the most basal crurotarsans. In one of the earliest studies of crurotarsan phylogeny, Sereno and Arcucci (1990) found Crurotarsi to be a monophyletic grouping consisting of phytosaurs, ornithosuchids, and the more derived
suchians, but produced a trichotomy between the three groups in their tree. In resolving this trichotomy, Parrish (1993) placed ornithosuchids, not phytosaurs, as the most basal crurotarsans. However, most other studies such as Sereno (1991) and Benton et al. (2010) recover phytosaurs in a basalmost position among crurotarsans. Below is a cladogram modified from Benton et al. (2010) showing the widely accepted phylogenetic relationships of phytosaurs:
A phylogenetic analysis of early archosaurs by Nesbitt (2011) found strong support for a sister taxon relationship between phytosaurs and Archosauria. If this is the case, phytosaurs would be placed outside Pseudosuchia in a more basal position among archosauriforms. Phytosaurs would be considered closely related to the ancestors of both crocodilians and dinosaur
s. Furthermore, the definition of the clade Crurotarsi would change, as it is often defined by the inclusion of phytosaurs. Thus, Crurotarsi would include phytosaurs and all other archosaurs —including dinosaurs— under this phylogeny. Below is a cladogram showing the placement of phytosaurs from Nesbitt (2011):
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...
archosaurs. Phytosaurs belong to the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Phytosauridae and the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Phytosauria. They were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodile
Crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...
s in size, appearance, and lifestyle, an example of convergence
Convergent evolution
Convergent evolution describes the acquisition of the same biological trait in unrelated lineages.The wing is a classic example of convergent evolution in action. Although their last common ancestor did not have wings, both birds and bats do, and are capable of powered flight. The wings are...
or parallel evolution
Parallel evolution
Parallel evolution is the development of a similar trait in related, but distinct, species descending from the same ancestor, but from different clades.-Parallel vs...
. The name "phytosaur" (plant reptile) is very misleading, and their snapping jaws clearly show that phytosaurs were predators. The person who first described them mistakenly thought the specimens he was working with were plant-eaters (Jaeger 1828).
Although phytosaurs were not true crocodilians themselves, they were more closely related to the crocodilians than to other modern reptiles, as phytosaurs are basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
members of the clade Crurotarsi
Crurotarsi
The Crurotarsi are a group of archosauriformes, represented today by the crocodiles,...
. Crocodiles did not become superficially 'phytosaur'-like until the Early Jurassic
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
.
Phytosaurs had a nearly global distribution during the Triassic. Fossils have been recovered from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, 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...
, Morocco
Morocco
Morocco , officially the Kingdom of Morocco , is a country located in North Africa. It has a population of more than 32 million and an area of 710,850 km², and also primarily administers the disputed region of the Western Sahara...
, Thailand
Thailand
Thailand , officially the Kingdom of Thailand , formerly known as Siam , is a country located at the centre of the Indochina peninsula and Southeast Asia. It is bordered to the north by Burma and Laos, to the east by Laos and Cambodia, to the south by the Gulf of Thailand and Malaysia, and to the...
, and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. Fossils attributed to phytosaurs have been found in Early Jurassic rocks, possibly extending their temporal range beyond the Triassic-Jurassic boundary.
Morphotypes
Dolichorostral ("long snouted") types have a long, slender snout and a large number of conical teeth that are the same throughout. These were most likely piscivorous
Piscivore
A piscivore is a carnivorous animal which eats primarily fish. Piscivory was the diet of early tetrapods , insectivory came next, then in time reptiles added herbivory....
, able to capture fast slippery prey, but not so good at tackling a land animal. Some examples are Paleorhinus
Paleorhinus
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...
, Rutiodon carolinensis, and Mystriosuchus
Mystriosuchus
Mystriosuchus is an extinct genus of phytosaur that lived in the Late Triassic in Europe. It was first named by Eberhard Fraas in 1896, and includes two species: M. westphali and the type species, M. planirostris...
. At one time it was believed that Paleorhinus and Mystriosuchus belonged to a distinct group of phytosaurs (subfamily of family Mystriosuchinae/Mystriosuchidae Huene, 1915) characterised by this adaptation, but it is now known that Mystriosuchus is actually more closely related to Pseudopalatus
Pseudopalatus
Pseudopalatus is an extinct genus of pseudopalatine phytosaur. It was assigned to Parasuchia in 2005. Specimens have been found from Arizona and New Mexico and are of Norian age...
, an "altirostral" form (Hungerbühler, 2002).
Brachyrostral ("short snouted") forms are the opposite, they have a massive, broad snout, and a very strong skull and jaws, with the front teeth like fangs for holding the prey, and the rear teeth blade-like for slicing the meat into chunks that can easily be swallowed (an animal with different types of teeth like this is called heterodont
Heterodont
The anatomical term heterodont refers to animals which possess more than a single tooth morphology. For example, members of the Synapsida generally possess incisors, canines , premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding/hunting specialization...
). These were powerful animals specialised for feeding on strong struggling prey, such as terrestrial animals that come to the water to drink. Examples of this type are Nicrosaurus
Nicrosaurus
Nicrosaurus is an extinct genus of phytosaur reptile. Although it looked and probably lived like a crocodile, it was not closely related to these creatures, instead being a good example of parallel evolution...
and Smilosuchus
Smilosuchus
Smilosuchus meaning "deadly-knife crocodile" is an extinct genus of phytosaur from the Late Triassic of North America. It was first described in 1995 as a replacement generic name for Leptosuchus gregorii...
Altirostral ("high snouted") animals are intermediate between the two. They had heterodont dentition but not as extremely developed as the brachyrostral type. Angistorhinus
Angistorhinus
Angistorhinus is an extinct genus of phytosaur known from the Late Triassic period of Texas and Wyoming, USA. It was first named by Mehl in 1913 and the type species is Angistorhinus grandis. Other species from Texas and Wyoming, A. alticephalus , A. gracilis and A...
and Pseudopalatus are typical examples here. These were most likely generalist feeders.
Modern crocodilians exhibit a similar morphological diversity, for example the broad snouted altirostral alligator
Alligator
An alligator is a crocodilian in the genus Alligator of the family Alligatoridae. There are two extant alligator species: the American alligator and the Chinese alligator ....
and the long snouted dolichorostral gavial.
Phytosaurs were even better armoured than crocodiles, protected by heavy 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 (often found as fossils), and the belly reinforced with a dense arrangement of gastralia
Gastralium
Gastralia are dermal bones found in the ventral body wall of crocodilian and Sphenodon species. They are found between the sternum and pelvis, and do not articulate with the vertebrae...
(abdominal ribs).
Differences from crocodiles
Despite their great similarities in appearance and lifestyle, there are still a number of minor differences that distinguish phytosaurs from true crocodiles. For one thing, the phytosaur ankleTarsus (skeleton)
In tetrapods, the tarsus is a cluster of articulating bones in each foot situated between the lower end of tibia and fibula of the lower leg and the metatarsus. In the foot the tarsus articulates with the bones of the metatarsus, which in turn articulate with the bones of the individual toes...
structure is much more primitive than that of any crocodile. Also, phytosaurs lack the bony secondary palate
Secondary palate
The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates.In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves medially and their mutual fusion in the midline...
that crocodiles have that enables them to breathe even when the mouth is full of water. It is possible however that phytosaurs had a fleshy palate, as many Mesozoic crocodiles are presumed to have had. Finally, and most noticeably, phytosaurs had nostrils placed near or above the level of the eyes, in contrast to crocodiles where the nostrils are near the end of the snout. This adaptation may have developed to allow them to breathe while the rest of the body was submerged.
Teeth
In a 2001 study of the biomechanics of the dinosaur AlbertosaurusAlbertosaurus
Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
Albertosaurus
Albertosaurus is a genus of tyrannosaurid theropod dinosaur that lived in western North America during the Late Cretaceous Period, more than 70 million years ago. The type species, A. sarcophagus, was apparently restricted in range to the modern-day Canadian province of Alberta, after which...
had similarly crack-like serrations, but, at the base of each serration Abler discovered a round void
Void
-In science and engineering:*Void , the empty spaces between galaxy filaments*Lack of matter, or vacuum*Void, in boiling heat transfer, formed where there is a departure from nucleate boiling, causing a critical heat flux...
which would have functioned to distribute force over a larger surface area
Surface area
Surface area is the measure of how much exposed area a solid object has, expressed in square units. Mathematical description of the surface area is considerably more involved than the definition of arc length of a curve. For polyhedra the surface area is the sum of the areas of its faces...
. This void, termed an ampulla, would hinder the ability of the "crack" formed by the serration to propagate through the tooth. The phytosaur was found to lack adaptation
Adaptation
An adaptation in biology is a trait with a current functional role in the life history of an organism that is maintained and evolved by means of natural selection. An adaptation refers to both the current state of being adapted and to the dynamic evolutionary process that leads to the adaptation....
s for preventing its dental "cracks" from propagating. Abler examined another sort of prehistoric predator, Dimetrodon
Dimetrodon
Dimetrodon was a predatory synapsid genus that flourished during the Permian period, living between 280–265 million years ago ....
, and found that it lacked adaptations for guarding against crack propagation as well.
History
The next species to be described was Belodon plieningeri by von Meyer in von Meyer and Plieninger 1844. The altogether more appropriate name Parasuchia ("alongside the crocodiles", as they resembled crocodiles to a great degree) was coined by Thomas Huxley
Thomas Huxley
Thomas Henry Huxley PC FRS was an English biologist, known as "Darwin's Bulldog" for his advocacy of Charles Darwin's theory of evolution....
in 1875 along with his discovery and naming of the Indian species Parasuchus hislopi (Chatterjee, 1978), on the basis of a partial snout. The specimen also is usually considered non-diagnostic, and the name Parasuchus replaced by Paleorhinus
Paleorhinus
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...
. Although the names Parasuchidae and Phytosauridae are variously still used by different specialists, "phytosaur" is the standard generic name for these animals, despite the fact that these animals have been clearly shown to be carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
.
Evolutionary history
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...
age, evolving from an unspecified crurotarsan ancestor. There are no clear intermediate forms, as the first phytosaurs found were already fully formed and highly specialised.
The earliest phytosaurs belong to the primitive and comparatively unspecialised but very widely distributed genus Paleorhinus. A somewhat more advanced and larger form, Angistorhinus appears at the same time or soon after. Later in the Carnian, both these animals were replaced by more specialised forms like Rutiodon
Rutiodon
Rutiodon is an extinct genus of archosaur belonging to the family Phytosauridae. It lived during the Late Triassic period, and was about 10 to 25 feet in length...
, Leptosuchus
Leptosuchus
Leptosuchus is an extinct genus of phytosaur with a complex taxonomical history. Fossils have been found from the Dockum Group and lower Chinle Formation outcropping in Texas, New Mexico, and Arizona and date back to the Carnian stage of the Late Triassic.Currently there are believed to be four...
, and the huge Smilosuchus
Smilosuchus
Smilosuchus meaning "deadly-knife crocodile" is an extinct genus of phytosaur from the Late Triassic of North America. It was first described in 1995 as a replacement generic name for Leptosuchus gregorii...
(Lucas 1998). The Carnian-Norian extinction meant that these animals died off, and the Early Norian
Norian
The Norian is a division of the Triassic geological period. It has the rank of an age or stage . The Norian lasted from 216.5 ± 2.0 to 203.6 ± 1.5 million years ago. It was preceded by the Carnian and succeeded by the Rhaetian.-Stratigraphic definitions:The Norian was named after the Noric Alps in...
sees new genera like Nicrosaurus
Nicrosaurus
Nicrosaurus is an extinct genus of phytosaur reptile. Although it looked and probably lived like a crocodile, it was not closely related to these creatures, instead being a good example of parallel evolution...
and Pseudopalatus, both of which belong to the most derived clade of phytosaurs, the Pseudopalatinae
Pseudopalatinae
Pseudopalatinae was a subfamily of crocodile-like archosaurs called phytosaurs. As with all other phytosaurs, pseudopalatines lived during Late Triassic. The name is derived from the genus Pseudopalatus....
. Later in the middle Norian the advanced and specialised fish-eater Mystriosuchus appears. Fossil remains of this widespread animal is known from Germany, northern Italy, and Thailand. Finally the large Redondasaurus
Redondasaurus
Redondasaurus is a genus of phytosaur from the Late Triassic of North America. Translated, the name Redondasaurus means "Redonda lizard," referring to the Redonda Formation of east-central New Mexico, USA. It was first named by Hunt & Lucas in 1993, and contains one species, R. gregorii...
in south-west North America and the long-snouted (altirostral) Angistorhinopsis ruetimeyeri in Europe continued the group into the Rhaetian
Rhaetian
The Rhaetian is in geochronology the latest age of the Triassic period or in chronostratigraphy the uppermost stage of the Triassic system. It lasted from 203.6 ± 1.5 to 199.6 ± 0.6 million years ago...
. Phytosaur footprints (the ichnotaxon
Ichnotaxon
An ichnotaxon is defined by the International Code of Zoological Nomenclature as "a taxon based on the fossilized work of an organism", that is, the non-human equivalent of an artifact. Ichnotaxa are names used to identify and distinguish morphologically distinctive ichnofossils, more commonly...
Apatopus) are also known from the latest Rhaetian of the East Coast of USA (the Newark Supergroup) (Olsen et al. 2002). This indicates that phytosaurs continued as successful animals until the very end of the Triassic, when, along with many other large crurotarsan reptiles, they were killed off by the end Triassic 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...
.
There have been reports of phytosaur remains found in lowermost Jurassic rocks. A fragment of a lower jaw from a longirostrine archosaur has been described from early Hettangian
Hettangian
The Hettangian is the earliest age or lowest stage of the Jurassic period of the geologic timescale. It spans the time between 199.6 ± 0.6 Ma and 196.5 ± 1 Ma . The Hettangian follows the Rhaetian and is followed by the Sinemurian.In Europe stratigraphy the Hettangian is a part of the time span in...
strata in the town of Watchet
Watchet
Watchet is a harbour town and civil parish in the English county of Somerset, with an approximate population of 4,400. It is situated west of Bridgwater, north-west of Taunton, and east of Minehead. The parish includes the hamlet of Beggearn Huish...
in Somerset
Somerset
The ceremonial and non-metropolitan county of Somerset in South West England borders Bristol and Gloucestershire to the north, Wiltshire to the east, Dorset to the south-east, and Devon to the south-west. It is partly bounded to the north and west by the Bristol Channel and the estuary of the...
, England. While teleosaurid thalattosuchia
Thalattosuchia
Thalattosuchia is the name given to a clade of marine crocodylomorphs from the Early Jurassic to the Early Cretaceous that had a cosmopolitan distribution. They are sometimes colloquially referred to as marine crocodiles or sea crocodiles, though they are not actually members of Crocodilia.The term...
ns had similar longirostrine jaws to phytosaurs and were common in the Jurassic, they do not appear in earliest Jurassic rocks. The mandible is more similar to those of known phytosaurs than to thalattosuchians, and likely belongs to a phytosaur closely related to the genus Mystriosuchus. The presence of phytosaurs in the earliest Jurassic may have prevented thalattosuchians from occupying similar ecological niches until after their disappearance.
Genera
| Genus | Status | Age | Location | Unit | Notes | Images |
|---|---|---|---|---|---|---|
Angistorhinopsis Angistorhinopsis Angistorhinopsis is an extinct genus of altirostral pseudopalatine phytosaur. It was named for its supposed resemblance to Angistorhinus by Friedrich von Huene in 1922... |
Junior synonym | Junior synonym of Nicrosaurus Nicrosaurus Nicrosaurus is an extinct genus of phytosaur reptile. Although it looked and probably lived like a crocodile, it was not closely related to these creatures, instead being a good example of parallel evolution... |
||||
Angistorhinus Angistorhinus Angistorhinus is an extinct genus of phytosaur known from the Late Triassic period of Texas and Wyoming, USA. It was first named by Mehl in 1913 and the type species is Angistorhinus grandis. Other species from Texas and Wyoming, A. alticephalus , A. gracilis and A... |
Valid | Late 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... |
 Morocco United States |
Dockum Group Dockum Group The Dockum is a Late Triassic geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern Colorado, and Oklahoma panhandle. The Dockum reaches a maximum thickness of slightly over 650 m but is usually much... Popo Agie Formation Popo Agie Formation The Popo Agie 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... |
 |
|
Arribasuchus |
Junior synonym | Junior synonym of Pseudopalatus Pseudopalatus Pseudopalatus is an extinct genus of pseudopalatine phytosaur. It was assigned to Parasuchia in 2005. Specimens have been found from Arizona and New Mexico and are of Norian age... |
||||
Belodon Belodon Belodon is a genus of phytosaur, a crocodile-like reptile that lived during the Triassic. Its fossils have been found in Europe and elsewhere... |
Nomen dubium Nomen dubium In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application... |
Middle Norian |  Germany United States |
Stubensandstein Chinle Formation Chinle Formation The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the... |
Many remains have since been attributed to other animals or given their own genera |  |
Brachysuchus Brachysuchus Brachysuchus is an extinct genus of phytosaur known from the late Triassic period of Dockum Group in Texas, USA. It is known from the holotype UMMP 10336 is composed of a skull, lower jaws and partial postcranium and from the associated paratype UMMP 14366, nearly complete skull, recovered from... |
Junior synonym | Junior synonym of Angistorhinus Angistorhinus Angistorhinus is an extinct genus of phytosaur known from the Late Triassic period of Texas and Wyoming, USA. It was first named by Mehl in 1913 and the type species is Angistorhinus grandis. Other species from Texas and Wyoming, A. alticephalus , A. gracilis and A... |
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Centemodon Centemodon Centemodon is an extinct genus of phytosaur from the Late Triassic Period. It lived in what is now present-day North America. It is classified as a nomen dubium.-References:* in the Dinosaur On-Line Omnipedia... |
Nomen dubium | Norian | United States |
Cumnock Formation |
Named from several teeth in 1856 | |
Coburgosuchus Coburgosuchus Coburgosuchus is an extinct genus of pseudopalatine phytosaur. The genus was named for Coburg, Germany, the type locality where specimens have been found dating back to the Late Triassic... |
Junior synonym | Junior synonym of Nicrosaurus Nicrosaurus Nicrosaurus is an extinct genus of phytosaur reptile. Although it looked and probably lived like a crocodile, it was not closely related to these creatures, instead being a good example of parallel evolution... |
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Ebrachosuchus Ebrachosuchus Ebrachosuchus is an extinct genus of basal phytosaurid phytosaur. Fossils were first discovered from the Blasensandstein Formation near Ebrach, Germany, which dates back to the Carnian stage of the Late Triassic.... |
Junior synonym | Junior synonym of Paleorhinus Paleorhinus 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... |
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Francosuchus |
Junior synonym | Junior synonym of Paleorhinus Paleorhinus 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... |
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Leptosuchus Leptosuchus Leptosuchus is an extinct genus of phytosaur with a complex taxonomical history. Fossils have been found from the Dockum Group and lower Chinle Formation outcropping in Texas, New Mexico, and Arizona and date back to the Carnian stage of the Late Triassic.Currently there are believed to be four... |
Valid | Carnian | United States |
Chinle Formation Chinle Formation The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the... |
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Mesorhinus |
Junior synonym | Junior synonym of Paleorhinus Paleorhinus 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... |
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Mesorhinosuchus |
Junior synonym | Junior synonym of Paleorhinus Paleorhinus 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... |
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Mystriosuchus Mystriosuchus Mystriosuchus is an extinct genus of phytosaur that lived in the Late Triassic in Europe. It was first named by Eberhard Fraas in 1896, and includes two species: M. westphali and the type species, M. planirostris... |
Valid | Middle Norian | Germany |
Stubensandstein |
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| Nicrosaurus Nicrosaurus Nicrosaurus is an extinct genus of phytosaur reptile. Although it looked and probably lived like a crocodile, it was not closely related to these creatures, instead being a good example of parallel evolution... |
Valid | Late Norian - Rhaetian |  Early Modern France Germany |
Arnstadt Formation Upper 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... |
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Paleorhinus Paleorhinus 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... |
Valid | Late Carnian | Germany Poland Morocco United States |
Blasensandstein Formation Middle 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... Argana Formation Argana Formation The Argana Formation is a geological formation in Africa. It dates back to the Late Triassic.-Vertebrate fauna:Ornithischian tracks geographically located in the Province de Marrakech. Indeterminate theropod remains and tracks geographically located in the Province de Marrakech.... Chinle Formation Chinle Formation The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the... Popo Agie Formation Popo Agie Formation The Popo Agie 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... Tecovas Formation Tecovas Formation -Vertebrate fauna:... |
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Parasuchus |
Junior synonym | Junior synonym of Paleorhinus Paleorhinus 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... |
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Pravusuchus Pravusuchus Pravusuchus is an extinct genus of phytosaur known from the late Triassic of Chinle Formation in Arizona. It was first named by Michelle R. Stocker in 2010 and the type species is Pravusuchus hortus.... |
Valid | Norian | United States |
Chinle Formation Chinle Formation The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the... |
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Promystriosuchus |
Junior synonym | Junior synonym of Paleorhinus Paleorhinus 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... |
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Pseudopalatus Pseudopalatus Pseudopalatus is an extinct genus of pseudopalatine phytosaur. It was assigned to Parasuchia in 2005. Specimens have been found from Arizona and New Mexico and are of Norian age... |
Valid | Norian | United States |
Chinle Formation Chinle Formation The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the... |
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Redondasaurus Redondasaurus Redondasaurus is a genus of phytosaur from the Late Triassic of North America. Translated, the name Redondasaurus means "Redonda lizard," referring to the Redonda Formation of east-central New Mexico, USA. It was first named by Hunt & Lucas in 1993, and contains one species, R. gregorii... |
Valid | Norian - Rhaetian | United States |
Redonda Formation Travesser Formation |
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Rutiodon Rutiodon Rutiodon is an extinct genus of archosaur belonging to the family Phytosauridae. It lived during the Late Triassic period, and was about 10 to 25 feet in length... |
Valid | Carnian | United States |
Cumnock Formation Chinle Formation Chinle Formation The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the... |
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Smilosuchus Smilosuchus Smilosuchus meaning "deadly-knife crocodile" is an extinct genus of phytosaur from the Late Triassic of North America. It was first described in 1995 as a replacement generic name for Leptosuchus gregorii... |
Valid | Carnian | United States |
Chinle Formation Chinle Formation The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the... |
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Phylogeny
Phytosaurs are generally regarded as the most basal group of Crurotarsi, a cladeClade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of archosaurs that includes crocodilians and their extinct relatives. Phytosaurs are often excluded from a clade called Suchia
Suchia
Suchia is a clade of archosaurs that includes all pseudosuchians except ornithosuchids. It includes crocodilians and their extinct relatives. Paul Sereno defined Suchia as the least inclusive clade containing Aetosaurus ferratus, Rauisuchus tiradentes, Prestosuchus chiniquensis, Gracilisuchus...
, which usually encompasses all other crurotarsans, including 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, rauisuchia
Rauisuchia
Rauisuchia is a group of predatory and mostly large Triassic archosaurs. As a clade, Rauisuchia includes these Triassic forms and all crocodylomorphs, which are descendants of Triassic rauisuchians. The group in its traditional sense is paraphyletic, because it does not include crocodylomorph...
ns, and crocodylomorphs. Some studies have found polytomies
Polytomy
A polytomy , meaning many temporal based branches, is a section of a phylogeny in which the evolutionary relationships can not be fully resolved to dichotomies. In a phylogenetic tree, a polytomy is represented as a node which has more than two immediate descending branches...
between phytosaurs and other groups like Ornithosuchidae
Ornithosuchidae
Ornithosuchidae is an extinct family of reptiles from the Triassic period that were distantly related to crocodilians. They are classified as crurotarsan archosaurs. Ornithosuchids were quadrupedal and facultatively bipedal, meaning they had the ability to walk on two legs for short periods of time...
and Suchia. In these cases, it is unclear whether phytosaurs are the most basal crurotarsans. In one of the earliest studies of crurotarsan phylogeny, Sereno and Arcucci (1990) found Crurotarsi to be a monophyletic grouping consisting of phytosaurs, ornithosuchids, and the more derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
suchians, but produced a trichotomy between the three groups in their tree. In resolving this trichotomy, Parrish (1993) placed ornithosuchids, not phytosaurs, as the most basal crurotarsans. However, most other studies such as Sereno (1991) and Benton et al. (2010) recover phytosaurs in a basalmost position among crurotarsans. Below is a cladogram modified from Benton et al. (2010) showing the widely accepted phylogenetic relationships of phytosaurs:
A phylogenetic analysis of early archosaurs by Nesbitt (2011) found strong support for a sister taxon relationship between phytosaurs and Archosauria. If this is the case, phytosaurs would be placed outside Pseudosuchia in a more basal position among archosauriforms. Phytosaurs would be considered closely related to the ancestors of both crocodilians and 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. Furthermore, the definition of the clade Crurotarsi would change, as it is often defined by the inclusion of phytosaurs. Thus, Crurotarsi would include phytosaurs and all other archosaurs —including dinosaurs— under this phylogeny. Below is a cladogram showing the placement of phytosaurs from Nesbitt (2011):
Further reading
- Ballew, K.L. (1989). A phylogenetic analysis of Phytosauria from the Late Triassic of the Western United States. Dawn of the age of dinosaurs in the American Southwest: Pp. 309-339.
- Gregory, J.T. (1962). Genera of phytosaurs. American Journal of Science, 260: 652-690.
- Long, R.A. & Murry, P.A. (1995). Late Triassic (Carnian and Norian) tetrapods from the southwestern United States. New Mexico Museum of Natural History and Science Bulletin, 4: 1-254.
External links
- Translation and Pronunciation Guide
- A Preliminary Biomechanical Analysis of Phytosaur Life Habits
- Phytosauria - Palaeos
- Mikko's Phylogeny - cladistic tree
- Great Triassic Assemblages Pt 1 - The Chinle and Newark - some material on phytosaurs