Krzyzanowskisaurus
Encyclopedia
Krzyzanowskisaurus is the name given to a genus
of archosaur
from the Late Triassic
. The generic name honours Stan Krzyżanowski. It is a tooth taxon, based on fossils only of teeth. These teeth have been found in the U.S. states of Arizona
(including the type locality) and New Mexico
. The original report described it as a "probable ornithischia
n".
Heckert (2005) suggests that Krzyzanowskisaurus teeth have biostratigraphic utility as an index fossil
of the St. Johnsian sub-lvf (land-vertebrate faunachron).
The type species, Krzyzanowskisaurus hunti, was reevaluated by Heckert in 2005
, after previously being described by him as Revueltosaurus hunti in 2002
. The name was changed when it was discovered that the type species of Revueltosaurus
, R. callenderi, was a pseudosuchian
rather than an ornithischian dinosaur
(Parker et al. 2005). According to Heckert, "R." hunti displays an orithischian-like feature not present in R. callenderi (teeth possessing a cingulum), suggesting that it represents a new genus of early ornithischian. This was challenged by Irmis et al. (2006), who found that the cingulum differed from that in true early ornithischians, and noted that some teeth had been found with skull bones and osteoderm
s that matched those of Revueltosaurus. Thus, they found that it was not a dinosaur, and provisionally retained it in Revueltosaurus; it may once again be R. hunti.
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 archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
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...
. The generic name honours Stan Krzyżanowski. It is a tooth taxon, based on fossils only of teeth. These teeth have been found in the U.S. states of Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
(including the type locality) and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
. The original report described it as a "probable ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
n".
Heckert (2005) suggests that Krzyzanowskisaurus teeth have biostratigraphic utility as an index fossil
Index fossil
Index fossils are fossils used to define and identify geologic periods . They work on the premise that, although different sediments may look different depending on the conditions under which they were laid down, they may include the remains of the same species of fossil...
of the St. Johnsian sub-lvf (land-vertebrate faunachron).
The type species, Krzyzanowskisaurus hunti, was reevaluated by Heckert in 2005
2005 in science
The year 2005 in science and technology involved some significant events.-Astronomy:* April 8 – Total solar eclipse*February 23 – Astronomers announce the discovery of a galaxy, VIRGOHI21, that consists almost entirely of dark matter...
, after previously being described by him as Revueltosaurus hunti in 2002
2002 in science
The year 2002 in science and technology involved some significant events.-Astronomy and space exploration:* February 19 - NASA's Mars Odyssey space probe begins to map the surface of Mars using its thermal emission imaging system....
. The name was changed when it was discovered that the type species of Revueltosaurus
Revueltosaurus
Revueltosaurus is a genus of prehistoric crurotarsan from Late Triassic New Mexico and Arizona.According to William Parker, who discovered the partial skeleton, "we have pretty much erased the record of Triassic ornithischian dinosaurs from North America, Europe and worldwide, except for South...
, R. callenderi, was a pseudosuchian
Crurotarsi
The Crurotarsi are a group of archosauriformes, represented today by the crocodiles,...
rather than an ornithischian 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...
(Parker et al. 2005). According to Heckert, "R." hunti displays an orithischian-like feature not present in R. callenderi (teeth possessing a cingulum), suggesting that it represents a new genus of early ornithischian. This was challenged by Irmis et al. (2006), who found that the cingulum differed from that in true early ornithischians, and noted that some teeth had been found with skull bones 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 that matched those of Revueltosaurus. Thus, they found that it was not a dinosaur, and provisionally retained it in Revueltosaurus; it may once again be R. hunti.