Rileyasuchus
Encyclopedia
Rileyasuchus is a genus
of phytosaur
from the Rhaetian
(Late Triassic
) of England
. It has a confusing history, being associated with the taxonomy of Palaeosaurus
and Thecodontosaurus
, and being a replacement name for a preoccupied genus (Rileya, which had already been used by Howard (or Ashmead; it's unclear which one has priority, but they apparently are the same animal) in 1888 for a hymenopteran).
named the new genus for two vertebrae and a humerus
from deposits in Bristol
. He had recognized it as a phytosaur
by 1908 (by which point a few Palaeosaurus species had been added to the genus).
It seems to have sat unrecognized for most of the 20th century, except for 1961 when Oskar Kuhn
renamed it from Rileya to Rileyasuchus. Adrian Hunt in 1994 (doctoral dissertation) first suggested that it was a herrerasaurid
, although this was never published. Benton et al. (2000) indicated that the type specimen
was actually a chimera
composed of a phytosaur humerus and Thecodontosaurus
vertebrae. It is best regarded as a nomen dubium
.
crocodile
-like predator.
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 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...
from 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...
(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...
) of England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
. It has a confusing history, being associated with the taxonomy of Palaeosaurus
Palaeosaurus
Several very different genera of prehistoric animals have been named Palaeosaurus or Paleosaurus since the 1830s. Further confusing the matter, all of the species are poorly known or poorly preserved and both spellings have been used interchangeably, even by the same authors.The repeated recurrence...
and Thecodontosaurus
Thecodontosaurus
Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur which lived during the late Triassic period ....
, and being a replacement name for a preoccupied genus (Rileya, which had already been used by Howard (or Ashmead; it's unclear which one has priority, but they apparently are the same animal) in 1888 for a hymenopteran).
History and Taxonomy
Friedrich von HueneFriedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...
named the new genus for two vertebrae and a humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
from deposits in Bristol
Bristol
Bristol is a city, unitary authority area and ceremonial county in South West England, with an estimated population of 433,100 for the unitary authority in 2009, and a surrounding Larger Urban Zone with an estimated 1,070,000 residents in 2007...
. He had recognized it as 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...
by 1908 (by which point a few Palaeosaurus species had been added to the genus).
It seems to have sat unrecognized for most of the 20th century, except for 1961 when Oskar Kuhn
Oskar Kuhn
Oskar Kuhn was a German palaeontologist.-Life and career:Kuhn was educated in Dinkelsbühl and Bamberg and then studied natural science, specialising in geology and paleontology, at the University of Munich, from which he received his D. Phil...
renamed it from Rileya to Rileyasuchus. Adrian Hunt in 1994 (doctoral dissertation) first suggested that it was a herrerasaurid
Herrerasauridae
Herrerasaurids are among the oldest known dinosaurs, appearing in the fossil record 231.4 million years ago . They became extinct by the end of the Triassic period. Herrerasaurids were small-sized carnivorous theropods or basal saurischians...
, although this was never published. Benton et al. (2000) indicated that the type specimen
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...
was actually a chimera
Chimera (paleontology)
In paleontology, a chimera is a fossil which was reconstructed with elements coming from more than a single species of animal. A now classic example of chimera is Protoavis.-List of paleontological chimeras:*Brontosaurus*Lametasaurus...
composed of a phytosaur humerus and Thecodontosaurus
Thecodontosaurus
Thecodontosaurus is a genus of herbivorous basal sauropodomorph dinosaur which lived during the late Triassic period ....
vertebrae. It is best regarded as a nomen dubium
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
.
Paleobiology
As a phytosaur, it would have been a semi-aquaticAquatic animal
An aquatic animal is an animal, either vertebrate or invertebrate, which lives in water for most or all of its life. It may breathe air or extract its oxygen from that dissolved in water through specialised organs called gills, or directly through its skin. Natural environments and the animals that...
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...
-like predator.