Staurikosaurus DB.jpg
   HOME

TheInfoList



OR:

''Staurikosaurus'' (Pronounced "STORE-ee-koh-SAWR-us", " Southern Cross lizard") is a genus of
herrerasaurid Herrerasauridae is a family of carnivorous dinosaurs, possibly basal to either theropods or even all of saurischians, or even their own branching from dracohors, separate from dinosauria altogether. They are among the oldest known dinosaurs, fi ...
dinosaur from the Late Triassic of Brazil, found in the Santa Maria Formation.


Description

Colbert (1970) described ''Staurikosaurus'' as a small and agile, bipedal predator.Colbert, E. H. (1970). A Saurischian dinosaur from the Triassic of Brazil. AM. MUS. NOVITATES 2405; 1-39 ''Staurikosaurus'' lived during the late- Carnian and early-
Norian The Norian is a division of the Triassic Period. It has the rank of an age (geochronology) or stage (chronostratigraphy). It lasted from ~227 to million years ago. It was preceded by the Carnian and succeeded by the Rhaetian. Stratigraphic defi ...
stage, of the Late Triassic, approximately 225 million years ago—which makes it one of the earliest dinosaurs known. Its length is measured at long,Grillo, O.N. and Azevedo, S.A.K. (2011). "Recovering missing data: estimating position and size of caudal vertebrae in ''Staurikosaurus pricei'' Colbert, 1970." ''Annals of the Brazilian Academy of Sciences'', but Gregory S. Paul presented a lower length estimate of and a body mass estimate of . ''Staurikosaurus'' was small in comparison to later theropods like '' Megalosaurus''. The type specimen has long but relatively slender limb bones. There exists a very incomplete fossil record of ''Staurikosaurus'', consisting of most of the spine, the legs and the large lower jaw. However, dating from such an early period in the dinosaurs' history and being otherwise so primitive, most of ''Staurikosaurus other features as being primitive also can be reconstructed. For example, ''Staurikosaurus'' is usually depicted with five toes and five fingers—very simple features of an unspecialized dinosaur. However, since the skeletal structure of the legs is known, it can be seen that ''Staurikosaurus'' was a quick runner for its size. It also had just two vertebrae joining the
pelvis The pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). The ...
to the
spine Spine or spinal may refer to: Science Biology * Vertebral column, also known as the backbone * Dendritic spine, a small membranous protrusion from a neuron's dendrite * Thorns, spines, and prickles, needle-like structures in plants * Spine (zoolog ...
, a distinctly primitive condition. The available teeth for ''Staurikosaurus'' bear a morphology that strongly suggests a carnivorous diet. The teeth are all serrated, laterally compressed, and caudally curved (i.e. the top of each tooth is curved back toward the throat).Bittencourt, J.S. & Kellner, A.W.A., 2009
The anatomy and phylogenetic position of the Triassic dinosaur Staurikosaurus pricei Colbert, 1970
Zootaxa 2079, 1–56.
This dentition suggests that ''Staurikosaurus'' could catch and hold prey, as well as slice and tear flesh to aid in mechanical digestion.Langer, M. C., 2004, Basal Saurischia, Chapter Two: In: The Dinosauria, Second Edition, edited by Weishampel, D.B., Dodson, P., and Osmolska, H., California University Press, p. 25-46. The tail of ''Staurikosaurus'' was relatively long (with more than 40 vertebrae) compared to the rest of its body and was held straight and off the ground as it ran. The rear part of ''Staurikosaurus''s tail is stiffened by features of the tail vertebrae. Ostrom (1969a) considered this adaptation to serve as a dynamic stabilizer facilitating the animal's leaping and running. A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. According to Sues (1990), ''Staurikosaurus'' can be distinguished based on the following 14 features: (i) a mandible almost as long as the femur, suggesting a proportionately large head; (ii) a fairly deep but thin dentary with 13 to 14 teeth and with a well-developed retroarticular process; (iii) a vertebral column with 9 to 10 cervical, 15 dorsal, 2
sacral Sacral may refer to: *Sacred, associated with divinity and considered worthy of spiritual respect or devotion *Of the sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spi ...
, and more than 40 caudal vertebrae. ''Staurikosaurus'' is considered to be more primitive than any other dinosaur because only two sacral vertebrae are present; (iv) an elongated 3rd, 4th, and 5th cervical vertebrae, which represents a primitive condition; (v) cranial cervical vertebrae that lack epipophyses; (vi) the absence of accessory intervertebral articulations; (vii) a slender scapular blade that is not expanded proximally; (viii) a large and plate-like coracoid; (ix) a
humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
featuring a prominent deltopectoral crest (represents a primitive condition) as well having distinctly expanded articular ends; (x) an
ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...
with an extensively developed medial wall of a semiperforate
acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) that c ...
(like ''Herrerasaurus'', but unlike any other dinosaur); (xi) a long pubis, two-thirds the length of the femur; (xii) hollow limb bones that feature fairly thick walls; (xiii) a robust femur with an S-shaped shaft: and (xiv) a tibia and fibula slightly longer than the femur. Novas (1993) added that ''Staurikosaurus'' is distinguished from other dinosaurs based on the presence of a distal bevel on anterior margin of its pubis. Langer and Benton (2006) noted that ''Staurikosaurus'' can be distinguished based on the anterior trochanter being reduced to a scar. Bittencourt and Kellner (2009) also noted that the proximal fibula has a medial sulcus, which is unique to ''Staurikosaurus pricei.''


Discovery and occurrence

''Staurikosaurus'' means " Southern Cross" (after the star constellation visible from the Southern Hemisphere) and "Lizard" (from the Greek work "saurus" meaning lizard), thus "Southern Cross Lizard." The species name ''pricei'' is in the honor of Colbert's fellow paleontologist
Llewellyn Ivor Price Llewellyn Ivor Price (October 9, 1905 – June 9, 1980) was one of the first Brazilian paleontologists. His work contributed not only to the development of Brazilian but also to global paleontology. He collected '' Staurikosaurus'', the first ...
. The first known specimen of ''Staurikosaurus'' (MCZ 1669) was recovered from the
Paleontological Site Jazigo Cinco Paleontological Site Jazigo Cinco is located in the city of Santa Maria, Rio Grande do Sul, Brazil. And belongs to Santa Maria Formation. It is located in the neighborhood Kilometro 3 near Castelinho, is to 2.7 kilometers away from the Paleont ...
of the Santa Maria Formation,"Staurikosaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 45. .
Rio Grande do Sul Rio Grande do Sul (, , ; "Great River of the South") is a Federative units of Brazil, state in the South Region, Brazil, southern region of Brazil. It is the Federative_units_of_Brazil#List, fifth-most-populous state and the List of Brazilian st ...
, southern Brazil. ''Staurikosaurus'' was found in mid-Carnian sediments. The genus name refers to the
star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...
"The Southern Cross", pictured in the
coat of arms of Brazil The coat of arms of Brazil ( pt, Brasão de Armas do Brasil) was created on 19 November 1889, four days after Brazil became a republic. It consists of the central emblem surrounded by coffee ('' Coffea arabica'', at the left) and tobacco (''Nic ...
and only visible in the Southern Hemisphere—when ''Staurikosaurus'' was described in 1970, it was unusual to find dinosaurs in the Southern Hemisphere. The
specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
honors the Brazilian paleontologist
Llewellyn Ivor Price Llewellyn Ivor Price (October 9, 1905 – June 9, 1980) was one of the first Brazilian paleontologists. His work contributed not only to the development of Brazilian but also to global paleontology. He collected '' Staurikosaurus'', the first ...
, who discovered it in 1936. It was described by Edwin Harris Colbert, working at the
American Museum of Natural History The American Museum of Natural History (abbreviated as AMNH) is a natural history museum on the Upper West Side of Manhattan in New York City. In Theodore Roosevelt Park, across the street from Central Park, the museum complex comprises 26 inter ...
. The rarity of ''Staurikosaurus'' remains may be a result of it being uncommon while alive, or because it lived in an environment like a forest, where fossils rarely form. Nonetheless, Garcia et al. (2019) referred the holotype of ''Teyuwasu barberenai'' as a second specimen of ''Staurikosaurus pricei'' (see Classification).


Classification

Later research by Sues et al. (2011) supports that ''Staurikosaurus'' and the related genus ''
Herrerasaurus ''Herrerasaurus'' is a genus of saurischian dinosaur from the Late Triassic period. This genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the rancher who discovered the first specimen in ...
'' are theropods and evolved after the sauropod line had split from the Theropoda. Mortimer points out that Benedetto (1973) and Galton (1985) were the first to recognize that ''Staurikosaurus'' and ''Herrerasaurus ''were more closely related to each other than to sauropodomorphs or avepods, placing them both in the Herrerasauridae and Herrerasauria. ''Staurikosaurus'' differs from ''Herrerasaurus'' because of its considerably smaller size (femur length of vs. ). Sereno et al. (1993) concluded that ''Staurikosaurus'' was not a theropod and considered it a basal saurischian outside Theropoda and Sauropodomorpha.''Staurikosaurus'' was originally incorrectly assigned by Colbert to Palaeosauriscidae, a defunct family based largely on '' Efraasia'', a prosauropod dinosaur. All major phylogenetic analyses since 1994 have assigned ''Staurikosaurus'' to the clade Herrerasauridae, which is the current scientific consensus on classification of this genus. Bittencourt and Kellner (2009) stated that the phylogenetic position of ''Staurikosaurus'' is constrained by its close relationship with ''Herrerasaurus ischigualastensis'', which is more complete and well known. Below is a cladogram based on the phylogenetic analysis conducted by Sues et al. in 2011, showing the relationships of ''Staurikosaurus'':


Related genera

''Staurikosaurus'' was placed in the clade Herrerasauridae by Benedetto in 1973. Herrerasauridae also includes ''
Herrerasaurus ''Herrerasaurus'' is a genus of saurischian dinosaur from the Late Triassic period. This genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the rancher who discovered the first specimen in ...
ischigualastensis'', both small predatory animals that were either dinosaurs or precursors to dinosaurs.Novas, F.E. 1997. Herrerasauridae. In P.J. Currie and K. Padian (eds.). Encyclopedia of Dinosaurs. Academic Press. These three dinosaurs lived during the Carnian stage of the Triassic period. Most phylogenetic analyses excluded ''
Eoraptor ''Eoraptor'' () is a genus of small, lightly built, basal sauropodomorph. One of the earliest-known dinosaurs, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwest ...
'' from the Herrerasauridae. Phylogenetic analysis by Sues, Nesbitt, Berman and Henrici, in 2011, exclude ''
Eoraptor ''Eoraptor'' () is a genus of small, lightly built, basal sauropodomorph. One of the earliest-known dinosaurs, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwest ...
'', and include '' Chindesaurus'' along with ''
Herrerasaurus ''Herrerasaurus'' is a genus of saurischian dinosaur from the Late Triassic period. This genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the rancher who discovered the first specimen in ...
'' as more derived than ''Staurikosaurus''. ''
Sanjuansaurus ''Sanjuansaurus'' (" San Juan Province lizard") is a genus of herrerasaurid dinosaur from the Late Triassic (Carnian) Cancha de Bochas and La Peña Members of the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Ar ...
'' was assigned to Herrerasauridae by Alcober and Martínez (2010). Sues (1990) assigned Ischisaurus to Herrerasauridae. Other proposed members of the
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
have included ''
Sanjuansaurus ''Sanjuansaurus'' (" San Juan Province lizard") is a genus of herrerasaurid dinosaur from the Late Triassic (Carnian) Cancha de Bochas and La Peña Members of the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Ar ...
'' from the same
Ischigualasto Formation The Ischigualasto Formation is a Late Triassic fossiliferous formation and Lagerstätte in the Ischigualasto-Villa Unión Basin of the southwestern La Rioja Province and northeastern San Juan Province in northwestern Argentina. The formation da ...
of Argentina as ''Herrerasaurus'', and possibly ''
Caseosaurus ''Caseosaurus'' ( ) is a dubious genus of saurischian dinosaur that lived approximately 221.5 to 212 million years ago during the latter part of the Triassic Period in what is now Texas, in North America. It was a small, lightly-built, bipedal, ...
'' from the
Dockum Formation The Dockum is a Late Triassic (approximately late Carnian through Rhaetian, or 223–200 Ma) geologic group found primarily on the Llano Estacado of western Texas and eastern New Mexico with minor exposures in southwestern Kansas, eastern Color ...
of Texas, although the relationships of these animals are not fully understood, and not all paleontologists agree. Alcober and Martinez (2010) concluded that ''Staurikosaurus'' and ''Sanjuansaurus'' are closely related based on similarities in their pubis and tibia.


Synonyms

The controversial
dinosauriform Dinosauromorpha is a clade of avemetatarsalian archosaurs (reptiles closer to birds than to crocodilians) that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lager ...
''"Teyuwasu barberenai"'' was recently considered a
synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...
of ''Staurikosaurus pricei''. Both taxa are known from single incomplete and somewhat poorly preserved specimens, therefore the former holotype specimen of "''Teyuwasu"'' would be the second specimen ascribed to ''Staurikosaurus'' within almost 50 years of its naming. The synonymy was based on a combination of five osteological features that are only present in both specimens among Triassic early dinosauriforms: (i) femur without a trochanteric shelf; (ii) symmetric fourth trochanter of the femur; (iii) crista tibiofibularis poorly separated from the lateral condyle at the distal end of the femur; (iv) posterolateral flange of the distal end of the tibia does not exceeds the lateral margin of the bone; (v) and rounded distal end of the tibia. The synonymy is commented in two subsequent papers, which cast doubt in the association of "Teyuwasu" with ''Staurikosaurus''. In the first paper, the authors only mention that the holotype of "''Teyuwasu"'' is not well preserved, and thus cannot be attributed to ''Staurikosaurus''. In the second, the authors argue that several of the five character states cited to unite the taxa are present in immature specimens of other dinosauriforms. However, the combination (that is, the simultaneous presence) of the five characters listed by Garcia et al. is not present in any of the aforementioned dinosauriforms, and therefore remains unique between "''Teyuwasu''" and ''Staurikosaurus''. Therefore, further investigations are needed in order to whether confirm or not the synonymy between "''Teyuwasu barberenai''" and ''Staurikosaurus pricei''.


Paleobiology


Feeding

''Staurikosaurus'' was a small but active bipedal predator, that preyed on small and medium-sized terrestrial vertebrates such as
cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...
s, rhynchosaurs, and herbivorous synapsids. The mandible of ''Staurikosaurus'' suggests that a sliding joint in the jaw allowed it to move backwards and forwards, as well as up and down. However, some authors questioned the presence of an intramandibular joint in ''Staurikosaurus'', due to the poor preservation of the holotype. Smaller prey could be worked backwards towards ''Staurikosaurus''s throat, aided along by its small, backwards-curving teeth. This feature was common in theropods of its time, but would disappear in later theropods.


Paleoecology

During the Late Triassic dinosaurs played only a minor role in terrestrial life; a fact that would change by the Early Jurassic. ''Staurikosaurus'' coexisted with large rauisuchian
archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...
s like ''
Rauisuchus ''Rauisuchus'' (meaning "Wilhelm Rau's crocodile") is a genus of extinct archosaurs which lived in what is now the Geopark of Paleorrota (Santa María Formation), Brazil, during the Late Triassic period (235–228 million years ago). It conta ...
'', which were the top carnivores in their ecosystemJ.F. Bonaparte, 1982, "Faunal Replacement in the Triassic of South America", Journal of Vertebrate Paleontology 2 (3): 362-371, December 1982. ''Staurikosaurus''s paleocommunity included medium- to large-sized herbivorous rhynchosaurs and dicynodonts. Medium-sized omnivorous aetosaurs and
cynodont The cynodonts () (clade Cynodontia) are a clade of eutheriodont therapsids that first appeared in the Late Permian (approximately 260 mya), and extensively diversified after the Permian–Triassic extinction event. Cynodonts had a wide variety ...
s were also present. Dinosaurs were represented by the Herrerasaurids, which include ''Staurikosaurus'', and the basal sauropodomorph ''
Saturnalia Saturnalia is an ancient Roman festival and holiday in honour of the god Saturn, held on 17 December of the Julian calendar and later expanded with festivities through to 23 December. The holiday was celebrated with a sacrifice at the Temple ...
''. The contemporaneous occurrence of basal theropods ''Staurikosaurus'', ''Herrerasaurus'', and ''Eoraptor'' with the ornithischian ''Pisanosaurus'' suggests that the main carnivorous and herbivorous lineages were established during the middle part of the Carnian stage. A U-Pb ( uranium decay) dating found that the Santa Maria Formation dated around 233.23 million years ago, putting it 1.5 million years older than the
Ischigualasto Formation The Ischigualasto Formation is a Late Triassic fossiliferous formation and Lagerstätte in the Ischigualasto-Villa Unión Basin of the southwestern La Rioja Province and northeastern San Juan Province in northwestern Argentina. The formation da ...
, and making the two formations approximately equal as the earliest dinosaur localities.


References


External links

* *
Dinosaurs of Rio Grande do Sul
{{Taxonbar, from=Q131145 Prehistoric saurischians Dinosaur genera Late Triassic dinosaurs of South America Triassic Brazil Fossils of Brazil Paleontology in Rio Grande do Sul Fossil taxa described in 1970 Taxa named by Edwin H. Colbert