Staurikosaurus

*Staurikosaurus pricei*

***Staurikosaurus*** (store-EE-koh-SORE-us) (Southern Cross Lizard) was a small, Herrerasaurid theropod dinosaur that lived in Brazil during the Late Triassic Period (225 MYA).

## Discovery

*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.

The first known specimen of *Staurikosaurus* was recovered from the Paleontological Site Jazigo Cinco of the Santa Maria Formation in the geopark of paleorrota, Rio Grande do Sul, southern Brazil. *Staurikosaurus* was found in Early Carnian sediments. The genus name refers to the star constellation "The Southern Cross", pictured in the coat of arms of Brazil 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 honors the Brazilian paleontologist Llewellyn Ivor Price, who discovered it in 1936. It was described by Edwin Harris Colbert, working at the American Museum of Natural History. 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.

In 1936, a Brazilian paleontologist named Llewellyn Ivor Prince discovered a small, early species of theropod while digging in the baldands of the Santa Maria Formation in southern Brazil. However, it wasn't until 1970 when a team of scientists revisited the site that this early species of dinosaur was rediscovered and officially named. It was named *Staurikosaurus princei*, meaning "Prince's Southern Cross Lizard", referring to the constellation "The Southern Cross", which can only be seen in the Southern Hemisphere, and Llewellyn Ivor Prince, than man who discovered this dinosaur. Based on it being an early theropod, living in the same area, and having similar construction to *Herrerasaurus*, in 1973 Benedetto dubbed *Staurikosaurus* to be in the genus Herrerasauridae, which also includes other small, early dinosaurs like *Eoraptor*.

## Description

Colbert (1970) described *Staurikosaurus* as a small and agile, bipedal predator. *Staurikosaurus* lived during the late-Carnian and early-Norian stage, of the late Triassic Period, 225 million years ago - which makes it one of the earliest dinosaurs known. At just 2.25 m ft long, 80 centimetres tall (31 in), and weighing just 30 kilograms (66 lb), *Staurikosaurus* was tiny 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 un-specialized 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 to the spine, a distinctly primitive condition.

*Staurikosaurus* was 7 ft (2.25 meters) and 31 inches (80 centimeters) tall

*Staurikosaurus* shared many features with its much larger cousin, *Herrerasaurus*, such as a long, rather slender head with several sharp teeth and powerful jaws to tear through the meat that it ate.

    Although it likely could see well, *Staurikosaurus* didn't have forward-facing eyes, so it wasn't capable of seeing its surroundings in-depth very well. Like most other early dinosaurs, it also had a relatively long, slender neck and body, which was designed to help it move streamlined fast and either catch up with the small, fast-moving animals it preyed on or stay ahead of larger, more dangerous predators like the menacing prestosuchus. It had long arms with gripping hands with five fingers and hook-like claws to grasp hold of small prey. Staurikosaurus' legs were also relatively long and had three toes with sharp talons at the end of each one. Its tail was also extended and would've helped balanced this sleek theropod while running and it had a long tail with more than 40 vertibrae.

### Teeth

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). This dentition suggests that *Staurikosaurus* could catch and hold prey, as well as slice and tear flesh to aid in mechanical digestion.

### Tail

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.

## Classification

Newer research by Sues et al. (2011) supports that *Staurikosaurus* and the related genus *Herrerasaurus* 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 23 cm vs. 47 cm). Sereno et al. (1993) concluded that *Staurikosaurus* was not a theropod and considered it a basal saurischian outside Theropoda and Sauropodamorpha.*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. 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 ischigualastensis* and *Eoraptor lunesis*, both small predatory animals that were either dinosaurs or precursors to dinosaurs. These three dinosaurs lived during the Carnian stage of the Triassic period. Some phylogenetic analyses excluded Eoraptor from the Herrerasauridae Phylogenetic analysis by Sues, Nesbitt, Berman and Henrici, in 2011, exclude Eoraptor, and include Chindesaurus along with Herrerasaurus as more derived than Staurikosaurus. Sanjuansaurus was assigned to Herrerasauridae by Alcober and Martínez (2010). Sues (1990) assigned Ischisaurus to Herrerasauridae. Other proposed members of the clade have included *Sanjuansaurus* from the same Ischigualasto Formation of Argentina as *Herrerasaurus*, and possibly *Caseosaurus* from the Dockum Formation 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 similarities in their pubis and tibia.

### Distinguishing anatomical features

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 a the femur, suggesting a proportionately large head; (ii) a fairly deep but thin dentary with 13-14 teeth and with a well-developed retroarticular process; (iii) a vertebral column with 9-10 cervical, 15 dorsal, 2 sacral, 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 featuring a prominent deltopectoral crest (represents a primitive condition)as well having distinctly expanded articular ends; (x) an ilium with an extensively developed medial wall of a semiperforate acetabulum (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.

## Paleobiology

### Feeding

*Staurikosaurus* was a small but active bipedal predator, that preyed on small and medium-sized terrestrial vertebrates such as cynodonts, 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. Smaller prey could be worked backwards towards Staurikosaurus' 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 archosaurs like Saurosuchus, which were the top carnivores in their ecosystem *Staurikosaurus'*s paleocommunity included medium to large-sized herbivorous rhynchosaurs and dicynodonts. Medium-sized omnivorous aetosaurs and cynodonts were also present. Dinosaurs were represented by the Herrerasaurids, which include *Staurikosaurus*, and the basal sauropodomorph Saturnalia. 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.

## JPInstitute.com Description

Staurikosaurus is one of the three earliest dinosaurs ever discovered. It may have evolved a little later than the Herrerasaurus, which it closely resembles. It was a sharp-toothed, meat-eating hunter that ate lizards, mammal-like reptiles and anything else it could catch. It was a fast runner on its large hind legs, probably the fastest land animal of its time.

Since it is one of the earliest dinosaurs ever discovered, Staurikosaurusis considered one of the first of the dinosauriforms, or true dinosaurs. It is known from a partial skeleton and is evidence of the success of the new design nature selected that would shape the course of land-dwelling creatures for the next 160 million years. During this period of Earth's history, dinosaurs still played a minor role in terrestrial life, but that was going to change.

## Appearance in other media

### *Jurassic Park*

* *Staurikosaurus* appears in the playstation game of The Lost World: Jurassic Park.

## Links

https://web.archive.org/web/20030405113432/http://www.jpinstitute.com/dinopedia/dinocards/dc\_staur.html

## References

1. ↑ 1.0 1.1 1.2 "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. ISBN 0-7853-0443-6.
2. ↑ Colbert, E. H. (1970). A Saurischian dinosaur from the Triassic of Brazil. AM. MUS. NOVITATES 2405; 1-39
3. ↑ 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*,
4. ↑ 4.0 4.1 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.
5. ↑ J. H. Ostrom. 1969. Osteology of Deinonychus antirrhopus, an unusual theropod from the Lower Cretaceous of Montana. Peabody Museum Bulletin 30:1-165 [M. Carrano/M. Carrano/M. Carrano]
6. ↑ 6.0 6.1 Hans-Dieter Sues, Sterling J. Nesbitt, David S. Berman and Amy C. Henrici (2011). "A late-surviving basal theropod dinosaur from the latest Triassic of North America". Proceedings of the Royal Society B 278 (1723): 3459–3464
7. ↑ Template:Cite web
8. ↑ Benedetto, 1973. Herrerasauridae, nueva familia de saurisquios triasicos. Ameghiniana. 10(1), 89-102.
9. ↑ Galton, 1985. The poposaurid thecodontian *Teratosaurus suevicus* v. Meyer, plus referred specimens mostly based on prosauropod dinosaurs, from the Middle Stubensandstein (Upper Triassic) of Nordwurttemberg. Stuttgart Beitrage zur Naturkunde (B). 116, 1-29.
10. ↑ Sereno, P. C., 1993, The pectoral girdle and forelimb of the basal Theropod Herrerasaurus ischigualastensis: Journal of Vertebrate Paleontology, v. 13, n. 4, p. 425-450.
11. ↑ 11.0 11.1 Novas, F.E. 1997. Herrerasauridae. In P.J. Currie and K. Padian (eds.). Encyclopedia of Dinosaurs. Academic Press.
12. ↑ Fernando E. Novas, Martin D. Ezcurra, Sankar Chatterjee and T. S. Kutty (2011). "New dinosaur species from the Upper Triassic Upper Maleri and Lower Dharmaram formations of central India". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 101 (3–4): 333–349.
13. ↑ Hans-Dieter Sues, Sterling J. Nesbitt, David S Berman and Amy C. Henrici (2011). "A late-surviving basal theropod dinosaur from the latest Triassic of North America". Proceedings of the Royal Society B 278 (1723): 3459
14. ↑ O. A. Alcober and R. N. Martínez. 2010. A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina. Zookeys 63:55-81 [M. Carrano/M. Carrano]
15. ↑ H.-D. Sues. 1990. Staurikosaurus and Herrerasauridae. In D. B. Weishampel, H. Osmólska, and P. Dodson (eds.), The Dinosauria. University of California Press, Berkeley 143-147 [M. Carrano/M. Carrano]
16. ↑ Template:Cite journal
17. ↑ Template:Cite journal
18. ↑ Alcober, Oscar A.; and Martinez, Ricardo N. (2010). "A new herrerasaurid (Dinosauria, Saurischia) from the Upper Triassic Ischigualasto Formation of northwestern Argentina". ZooKeys 63: 55–81.
19. ↑ Sues, 1990. Staurikosaurus and Herrerasauridae. in Weishampel, et al. (eds.). The Dinosauria. University of California Press, Berkeley, Los Angeles, Oxford. 143-147.
20. ↑ Novas, 1993. New information on the systematics and postcranial skeleton of Herrerasaurus ischigualastensis (Theropoda: Herrerasauridae) from the Ischigualasto Formation (Upper Triassic) of Argentina. Journal of Vertebrate Paleontology 13 p. 400-423.
21. ↑ Langer and Benton, 2006. Early dinosaurs: A phylogenetic study. Journal of Systematic Palaeontology. 4(4), 309-358.
22. ↑ J.F. Bonaparte, 1982, "Faunal Replacement in the Triassic of South America", Journal of Vertebrate Paleontology 2 (3): 362-371, December 1982.