Guaibasauridae
Encyclopedia
Guaibasauridae is a family
of primitive saurischia
n dinosaur
s, known from fossil
remains of late Triassic
period formations in Brazil
(Paleorrota
) and Argentina
.
The exact makeup and classification of the Guaibasauridae remains uncertain. The family was originally named by Jose Bonaparte
and colleagues in 1999 to contain a single genus
and species
, Guaibasaurus candelariensis
. When a second specimen of Guaibasaurus was described from better remains in 2007, it became easier to compare it to other enigmatic early saurischians, which are often difficult to classify because they combine characteristics of the two major saurischian groups, Theropoda
and Sauropodomorpha
. Bonaparte and colleagues, in light of the information gained from this second specimen, found that the genus Saturnalia
(which is anatomically very similar to Guaibasaurus) could also be assigned to the Guaibasauridae, though they did not conduct a phylogenetic analysis or define Guaibasauridae as a clade
. The researchers also tentatively assigned the poorly understood genus Agnosphitys
to this family.
Bonaparte and colleagues (2007) found that guaibasaurids have more characteristics in common with theropods than they do with early sauropodomorphs (or "prosauropods"). Because of this, according to Bonaparte, they are most likely either a very basal group on the stem leading toward sauropodomorphs, or a group ancestral to both sauropodomorphs and theropods. Furthermore, the authors interpret this as evidence that the common ancestor of both saurischian lineages was more theropod-like than prosauropod-like.
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...
of primitive saurischia
Saurischia
Saurischia meaning 'lizard' and ischion meaning 'hip joint') is one of the two orders, or basic divisions, of dinosaurs. In 1888, Harry Seeley classified dinosaurs into two orders, based on their hip structure...
n 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, known from fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains of late Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...
period formations in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
(Paleorrota
Paleorrota
Paleorrota , is a geopark located in the center of the Brazilian state of Rio Grande do Sul. The rocks and fossils found along the route date back to the times when there was only one supercontinent Pangaea....
) and Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
The exact makeup and classification of the Guaibasauridae remains uncertain. The family was originally named by Jose Bonaparte
José Bonaparte
José Fernando Bonaparte, Ph.D. , is an Argentine paleontologist who discovered a plethora of South American dinosaurs and mentored a new generation of Argentine paleontologists like Rodolfo Coria...
and colleagues in 1999 to contain a single genus
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...
and species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, Guaibasaurus candelariensis
Guaibasaurus
Guaibasaurus is an extinct genus of basal dinosaur known from the Triassic of Rio Grande do Sul, southern Brazil.-Discovery:Guaibasaurus was originally named on the basis of the holotype, MCN PV2355, a well-preserved partial postcranial skeleton and the paratype, MCN PV2356, an...
. When a second specimen of Guaibasaurus was described from better remains in 2007, it became easier to compare it to other enigmatic early saurischians, which are often difficult to classify because they combine characteristics of the two major saurischian groups, Theropoda
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
and Sauropodomorpha
Sauropodomorpha
Sauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs which includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The...
. Bonaparte and colleagues, in light of the information gained from this second specimen, found that the genus Saturnalia
Saturnalia (dinosaur)
Saturnalia is an extinct genus of basal sauropodomorph dinosaur known from the Triassic of Rio Grande do Sul, southern Brazil.-Discovery:Saturnalia was originally named on the basis of three partial skeletons...
(which is anatomically very similar to Guaibasaurus) could also be assigned to the Guaibasauridae, though they did not conduct a phylogenetic analysis or define Guaibasauridae as a clade
Clade
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...
. The researchers also tentatively assigned the poorly understood genus Agnosphitys
Agnosphitys
Agnosphitys is a disputed genus of dinosaur. It contains only one species, the type species A. cromhallensis. Its remains include an ilium, maxilla, astragalus and humerus, which date variously from the Norian and Rhaetian stages of the Late Triassic...
to this family.
Bonaparte and colleagues (2007) found that guaibasaurids have more characteristics in common with theropods than they do with early sauropodomorphs (or "prosauropods"). Because of this, according to Bonaparte, they are most likely either a very basal group on the stem leading toward sauropodomorphs, or a group ancestral to both sauropodomorphs and theropods. Furthermore, the authors interpret this as evidence that the common ancestor of both saurischian lineages was more theropod-like than prosauropod-like.
Taxonomy
After Ezcurra (2010):- Suborder SauropodomorphaSauropodomorphaSauropodomorpha is an extinct clade of long-necked, herbivorous, saurischian dinosaurs which includes the sauropods and their ancestral relatives. Sauropods generally grew to very large sizes, had long necks and tails, were quadrupedal, and became the largest animals to ever walk the Earth. The...
- Family Guaibasauridae
- AgnosphitysAgnosphitysAgnosphitys is a disputed genus of dinosaur. It contains only one species, the type species A. cromhallensis. Its remains include an ilium, maxilla, astragalus and humerus, which date variously from the Norian and Rhaetian stages of the Late Triassic...
- GuaibasaurusGuaibasaurusGuaibasaurus is an extinct genus of basal dinosaur known from the Triassic of Rio Grande do Sul, southern Brazil.-Discovery:Guaibasaurus was originally named on the basis of the holotype, MCN PV2355, a well-preserved partial postcranial skeleton and the paratype, MCN PV2356, an...
- PanphagiaPanphagiaPanphagia is a genus of sauropodomorph dinosaur described in 2009. It lived 231 million years ago, during the late Ladinian age of the mid Triassic period , in what is now northwestern Argentina...
- Subfamily Saturnaliinae
- ChromogisaurusChromogisaurusChromogisaurus is a sauropodomorph which existed in Argentina during the late Triassic period.Chromogisaurus was first named by Martín Daniel Ezcurra in 2010, and the type species is Chromogisaurus novasi. The generic name is derived from Greek chroma, "colour", and gè, "earth", a reference to the...
- SaturnaliaSaturnalia (dinosaur)Saturnalia is an extinct genus of basal sauropodomorph dinosaur known from the Triassic of Rio Grande do Sul, southern Brazil.-Discovery:Saturnalia was originally named on the basis of three partial skeletons...
- Chromogisaurus
- Agnosphitys
- Family Guaibasauridae