Herrerasaurus

*Herrerasaurus ischigualastensis*

***Herrerasaurus*** (meaning "Herrera's lizard", after the name of the rancher who discovered the first fossil of the animal) was one of the earliest dinosaurs. All known specimens of this carnivore have been discovered in rocks of early Carnian age (late Triassic, around 228 million years ago) in northwestern Argentina. The type species, *Herrerasaurus ischigualastensis*, was described by Osvaldo Reig in 1963 and is the only species assigned to the genus. The names *Ischisaurus* and *Frenguellisaurus* are synonymous with *Herrerasaurus*.

For many years, the classification of *Herrerasaurus* was unclear, as the animal was initially known from very fragmentary remains; it has been hypothesized to be a basal theropod, a basal sauropodomorph, a basal saurischian, or not a dinosaur at all. However, with the discovery of a mostly complete skeleton and skull in 1988, *Herrerasaurus* has been classified as either an early theropod or an early saurischian in at least five recent reviews of theropod evolution. *Herrerasaurus* is a medium-sized bipedal member of the Herrerasauridae, a group of similar animals which were among the earliest of the dinosaurian evolutionary radiation.

## Description

*Herrerasaurus* was a lightly-built bipedal carnivore with a long tail and a relatively small head. Its length is estimated at 3 to 6 meters (10 to 20 ft), and its hip height at more than 1.1 meters (3.3 ft). It may have weighed around 210–350 kilograms (463–772 lb). In a large specimen at first thought to belong to a separate genus, *Frenguellisaurus*, the skull measured 56 centimeters (1.8 ft) in length. Smaller specimens had skulls which measured around 30 centimeters (1 ft) in length.

### Skull

*Herrerasaurus* had a long, narrow skull that lacked nearly all the specializations that characterized later dinosaurs, and more closely resembled those of more primitive archosaurs such as *Euparkeria*. It had five pairs of fenestrae (skull openings) in its skull, two pairs of which were for the eyes and nostrils. Between the eyes and the nostrils were two antorbital fenestrae and a pair of tiny, 1-centimeter-long (0.4 in) slit-like holes called promaxillary fenestrae. Behind the eyes were large infratemporal fenestrae. These holes helped to reduce the weight of the skull.

*Herrerasaurus* had a flexible joint in the lower jaw, allowing it to slide back and forth to deliver a grasping bite. This cranial specialization is unusual among the dinosaurs but has evolved independently in some lizards. The rear of the lower jaw also had fenestrae. The jaws were equipped with large serrated teeth for biting and eating flesh, and the neck was slender and flexible.

### Limbs

*Herrerasaurus* had relatively short forelimbs, which were less than half the length of its hind limbs. The upper arm and forearm were rather short, while the manus was elongated. The first two fingers and the thumb bore curved, sharp claws for grasping prey. Its fourth and fifth digits were small stubs without claws.*Herrerasaurus* was bipedal. It had strong hind limbs with short thighs and rather long feet, indicating this animal was most likely a swift runner. The balancing tail, partially stiffened by overlapping vertebral processes, also indicates an adaptation for speed.

Unlike most reptiles of its era, *Herrerasaurus* was fully bipedal. It had strong hind limbs with short thighs and rather long feet, indicating that it was most likely a swift runner. The foot had five toes, but only the middle three (digits II, III, and IV) bore weight. The outer toes (I and V) were small; the first toe had a small claw. The tail, partially stiffened by overlapping vertebral projections, balanced the body and was also an adaptation for speed.

### Derived and basal characteristics

*Herrerasaurus* is something of an enigma in that it displays traits that are found in different groups of dinosaurs, and several traits found in non-dinosaurian archosaurs. Although it shared most of the characteristics of dinosaurs, there were a few differences, particularly in regard to the shape of its hip and leg bones. Its pelvis was similar to that of saurischian dinosaurs, but it had a bony acetabulum (where the femur meets the pelvis) that was only partially open. The ilium, the main hip bone, was supported only by two sacrals, a basal trait, but the pubis pointed backwards, a derived trait that parallels what is seen in dromaeosaurids and birds. Additionally, the end of the pubis had a booted shape, similar to what is present in avetheropods, and the vertebral centra had an *Allosaurus*-like hourglass shape.

## Classification

The upper cladogram presented here follows one proposed analysis by Max Langer in 2004. In this review, *Herrerasaurus* and *Staurikosaurus* are primitive saurischians, but not theropods. The lower cladogram is based on an analysis by Michael J. Benton, also in 2004. This review indicated *Herrerasaurus* was a basal theropod.
*Herrerasaurus* gives its name to its family, Herrerasauridae, of the mid- to late Triassic, although where it and its close relatives lie on the early dinosaur evolutionary tree is unclear. They are possibly basal theropods or basal saurischians but may in fact predate the saurischian-ornithischian split. The situation is further complicated by uncertainties in correlating the ages of late Triassic beds bearing land animals. Other members of the clade may include *Eoraptor* from the same Ischigualasto Formation of Argentina as *Herrerasaurus*, *Staurikosaurus* from the Santa Maria Formation of southern Brazil, *Chindesaurus* from the Upper Petrified Forest (Chinle Formation) of Arizona, and possibly *Caseosaurus* from the Dockum Formation of Texas, although the relationships of these animals are not fully understood, and not all paleontologists agree. Other possible basal theropods, *Alwalkeria* from the Late Triassic Maleri Formation of India, and *Teyuwasu*, known from very fragmentary remains from the Late Triassic of Brazil, might be related. Novas (1992) defined Herrerasauridae as *Herrerasaurus*, *Staurikosaurus*, and their most recent common ancestor. Sereno (1998) defined the group as the most inclusive clade including *H. ischigualastensis* but not *Passer domesticus*. Langer (2004) created a higher level taxon, infraorder Herrerasauria.

## History

*Herrerasaurus* was named by paleontologist Osvaldo Reig after Victorino Herrera, an Andean goatherd who first noticed its fossils in outcrops near the city of San Juan in 1959. These rocks, which later yielded *Eoraptor*, are part of the Ischigualasto Formation and date from the late Ladinian to early Carnian stages of the Late Triassic period. Reig named a second dinosaur from these rocks in the same publication as *Herrerasaurus*; this dinosaur, *Ischisaurus cattoi*, is now considered a junior synonym and a juvenile of *Herrerasaurus*. Two other partial skeletons, with skull material, were named *Frenguellisaurus ischigualastensis* by Fernando Novas in 1986, but this species too is now thought to be a synonym.

Reig believed *Herrerasaurus* was an early example of a carnosaur, but this was the subject of much debate over the next 30 years, and the genus was variously classified during that time. In 1970, Steel classified *Herrerasaurus* as a prosauropod. In 1972, Peter Galton classified the genus as not diagnosable beyond Saurischia. Later, using cladistic analysis, some researchers put *Herrerasaurus* and *Staurikosaurus* at the base of the dinosaur tree before the separation between ornithischians and saurischians. Several researchers classified the remains as non-dinosaurian.

A complete *Herrerasaurus* skull was not found until 1988, by a team of paleontologists led by Paul Sereno. Based on the new fossils, authors such as Thomas Holtz and Jose Bonaparte classified *Herrerasaurus* at the base of the saurischian tree before the divergence between prosauropods and theropods. However, Sereno favored classifying *Herrerasaurus* (and the Herrerasauridae) as primitive theropods. These two classifications have become the most persistent, with Rauhut (2003) and Bittencourt and Kellner (2004) favoring the early theropod hypothesis, and Max Langer (2004), Langer and Benton (2006), and Randall Irmis and his coauthors (2007) favoring the basal saurischian hypothesis. If *Herrerasaurus* were indeed a theropod, it would indicate that theropods, sauropodomorphs, and ornithischians diverged even earlier than herrerasaurids, before the middle Carnian, and that "all three lineages independently evolved several dinosaurian features, such as a more advanced ankle joint or an open acetabulum". This view is further supported by ichnological records showing large tridactyl (three-toed) footprints that can be attributed only to a theropod dinosaur. These footprints date from the Ladinian (Middle Triassic) of the Los Rastros Formation in Argentina and predate *Herrerasaurus* by 3 to 5 million years.

The study of early dinosaurs such as *Herrerasaurus* and *Eoraptor* therefore has important implications for the concept of dinosaurs as a monophyletic group (a group descended from a common ancestor). The monophyly of dinosaurs was explicitly proposed in the 1970s by Galton and Robert T. Bakker, who compiled a list of cranial and postcranial synapomorphies (common anatomical traits derived from the common ancestor). Later authors proposed additional synapomorphies. An extensive study of *Herrerasaurus* by Sereno in 1992 suggested that of these proposed synapomorphies, only one cranial and seven postcranial features were actually derived from a common ancestor, and that the others were attributable to convergent evolution. Sereno's analysis of *Herrerasaurus* also led him to propose several new dinosaurian synapomorphies.

## Paleoecology

Although *Herrerasaurus* shared the body shape of the large carnivorous dinosaurs, it lived about 230 million years ago, a time when dinosaurs were small and insignificant. It was the time of non-dinosaurian reptiles, not dinosaurs, and a major turning point in the Earth's ecology. The vertebrate fauna of the Ischigualasto Formation and the slightly later Los Colorados Formation consisted mainly of a variety of crurotarsal archosaurs and synapsids. For instance, in the Ischigualasto Formation, dinosaurs constituted only about 6% of the total number of fossils. By the end of the Triassic Period, dinosaurs were becoming the dominant large land animals, and the other archosaurs and synapsids declined in variety and number.

Studies suggest that the paleoenvironment of the Ischigualasto Formation was a volcanically active floodplain covered by forests and subject to strong seasonal rainfalls. The climate was moist and warm, though subject to seasonal variations. Vegetation consisted of ferns (*Cladophlebis*), horsetails, and giant conifers (*Protojuniperoxylon*). These plants formed highland forests along the banks of rivers. *Herrerasaurus* remains appear to have been the most common among the carnivores of the Ischigualasto Formation. It lived in the jungles of Late Triassic South America alongside another early dinosaur, the one metre long *Eoraptor*, as well as *Saurosuchus*, a giant land-living rauisuchian (a quadrupedal meat eater with a theropod-like skull); the broadly similar but smaller *Venaticosuchus*, an ornithosuchid; and the predatory chiniquodontids. Herbivores were much more abundant than carnivores and were represented by rhynchosaurs such as *Hyperodapedon* (a beaked reptile); aetosaurs (spiny armored reptiles); kannemeyeriid dicynodonts (stocky, front-heavy beaked quadrupedal animals) such as *Ischigualastia*; and traversodontids (somewhat similar in overall form to dicynodonts, but lacking beaks) such as *Exaeretodon*. These non-dinosaurian herbivores were much more abundant than early ornithischian dinosaurs like *Pisanosaurus*.

## Paleobiology

The teeth of *Herrerasaurus* indicate that it was a carnivore; its size indicates it would have preyed upon small and medium-sized plant eaters. These might have included other dinosaurs, such as *Pisanosaurus*, as well as the more plentiful rhynchosaurs and synapsids. *Herrerasaurus* itself may have been preyed upon by giant rauisuchids like *Saurosuchus*; puncture wounds were found in one skull.

Coprolites (fossilized dung) containing small bones but no trace of plant fragments, discovered in the Ischigualasto Formation, have been assigned to *Herrerasaurus* based on fossil abundance. Mineralogical and chemical analysis of these coprolites indicates that this carnivore could digest bone.Template:- Similar studies made on coprolites assigned to a large Cretaceous theropod (most probably *Tyrannosaurus*) and concluding to the ability of dinosaurs to dissolve ingested bones, further strengthen the assertion. Karen's paper said the opposite, that they were passing the bones quickly without digestion.

## JPInstitute.com Description

Discovered in 1963, Herrerasaurus is one of the oldest dinosaurs ever found. It is close to 230 million years old! It is one of three dinosaurs found in South America that represent the earliest form of meat-eating dinosaurs. In fact, Herrerasaurus may be the oldest of the three. It was a fast, ferocious hunter and it set the stage for large predatory dinosaurs to become the most dominant animals on earth for more than 150 million years.

Unlike later dinosaurs, Herrerasaurus had a wide variety of non-dinosaur creatures from which to chose for its menu. In the Triassic there were many types of creatures still roaming the land that would later disappear in an extinction event at the end of the Triassic, which the dinosaurs survived. One of the main types of creatures upon which Herrerasaurus would have fed were the mammal-like reptiles. For many millions of years the mammal-like reptiles were the dominant land creatures until dinosaurs appeared on the scene. They were slower and less adaptable than the dinosaurs and could not survive the competition. Herrerasaurus would have also eaten lizards, amphibians and possibly some of the large insects that lived in the Triassic.

Herrerasaurus, being an early dinosaur, seems to have had some characteristics that confuse scientists trying to find its place in dinosaur evolution. It shows traits that show up in much later Jurassic dinosaurs and traits that are found in different classifications of dinosaurs, making it difficult to fit it into a specific family tree. Its teeth are more conical in shape than later or contemporary dinosaurs, and they have serrations like most of the later carnivorous dinosaurs. It also appears that the Herrerasaurus jaw was somewhat flexible in order to fit more firmly around its prey and prevent it from escaping. Its arms show proportions more similar to later predatory dinosaurs in that they were much shorter than its hind limbs and clearly designed for prey capture.

It is estimated that Herrerasaurus could have reached lengths of up to 15 feet (4.5 m), making it as large as dinosaurs that did not come along until well into the Jurassic.

## Dinosaur Field Guide Description

Herrerasaurus ("[Victorino] Herrera's lizard") was one of the oldest and most primitive theropods, or meat-eating dinosaurs. And its body displayed many of the same features of the later theropods. It walked on its two hind legs, and its arms ended in powerful clawed hands for grasping prey. Its teeth-like those of most theropods--were shaped like blades and had knife-like serrations running up the front and down the back. Its
lower jaw had a special hinge about halfway along its length. This joint would have helped Herrerasaurus to better hold on to struggling victims. Many later theropods also had this hinge. Although Herrerasaurus shared the basic body design of future rulers of the Earth (like Allosaurus, Giganotosaurus, and Tyrannosaurus), it lived at a time when dinosaurs were not the most powerful predators. Herrerasaurus would
have had to run away from the much larger Saurosuchus, a giant land-dwelling crocodile relative, which was the largest meat-eater in Argentina during the beginning of the Age of Dinosaurs.

### Fun Facts

One of the most complete mounted skeletons of Herreresaurus can be seen at the Field Museum of Natural History in Chicago.

### Trivia

Before the first skull was discovered in 1988, Herrerasaurus was thought to be a prosauropod, an early form of the giant long necked plant eaters, like Plateosaurus.

## Appearance in other media

### *Jurassic Park*

* A *Herrerasaurus*‘ icon was located on a map of the Jurassic Park brochure, but the animal was never seen on-screen. On the map, *Herrerasaurus*‘ enclosure is located at the far northwestern end of the island where the tourist route does not connect. However, it is unknown if this enclosure was ever constructed.

* *Herrerasaurus* also appeared in *Jurassic Park: The Game*.

* *Herrerasaurus* apparently went into Cruelly after the Isla Nublar Incident of 2015 before *Jurassic World: Fallen Kingdom* it is unknown if there are any surviving populations.

* *Herrerasaurus* can be created in *Jurassic Park III: Park Builder*.

* *Herrerasaurus* is listed on the Isla Sorna map seen in *LEGO Jurassic World*, but does not physically appear.

* A *Herrerasaurus* figure will be featured in a toy-line for *Jurassic World: Fallen Kingdom*. This has been the first time *Herrerasaurus* has ever physically appeared in a toy set. The toy varsity resemblance to the JP:TG Video Game version.

* *Herrerasaurus* was added to Jurassic World: Evolution on April 17 in the Carnivore Dinosaur Pack. It accurately have the dual dew claws, but only have 3 fingers instead of 5 and pronated wrists.

## Links

http://web.archive.org/web/20040214161614fw\_/http://www.jpinstitute.com/dinopedia/dinocards/dc\_herre.html#

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