What is Herrerasaurus
| Scientific Name (Genus) | Herrerasaurus |
| Meaning of Name |
Herrera's lizard
Herrera[person's name]-saurus(lizard)[Greek] |
| Classification |
Saurischia (Basal theropod or basal saurischian)
Herrerasauridae |
| Total Length | Approx. 3 - 6m |
| Diet | Carnivorous |
| Period | Late Triassic (approx. 231.4 - 228.9 million years ago) |
| Sub-classification / Species Name | Herrerasaurus ischigualastensis |
| Year of Paper Publication | 1963 |
| Genus Name Publication |
La presencia de dinosaurios saurisquios en los "Estratos de Ischigualasto" (Mesotriásico Superior) de las provincias de San Juan y La Rioja (República Argentina).
Ameghiniana. 3. by Reig, O.A. 1963. |
Herrerasaurus : Features
Herrerasaurus is one of the earliest and most completely known dinosaurs in the fossil record, appearing in Argentina, South America, during the Late Triassic (about 231.4 to 228.9 million years ago).
It was a bipedal predator reaching about 3 to 6 meters in total length and weighing about 200 to 350 kilograms.
The forelimbs (hands) of Herrerasaurus were less than half the length of its hindlimbs, but they were powerful weapons for catching prey. There were five fingers on the forelimbs, but the outer two were extremely reduced to mere bony bumps, and only three were functional. These three fingers were long, and at their tips were sharply curved claws for deeply piercing and tearing prey.
It also had forward-facing orbits (eye sockets) that allowed it to see objects stereoscopically with both eyes. The hind limbs were powerful and had a long structure from the shin to the tip of the foot, making it suitable for running bipedally.
Sliding Lower Jaw Joint
One of the amazing features of Herrerasaurus is that it had a joint in the middle of its lower jaw, allowing it to move its jaw back and forth in a sliding motion.
It is thought that the front half of the jaw, equipped with teeth, flexed in response to the movements of struggling prey, preventing the prey from escaping while at the same time reducing the strain on its own jaw. This indicates that Herrerasaurus was a carnivorous dinosaur that preyed on intensely moving animals.
Late Triassic Habitat and Diet
The "Ischigualasto Formation" in Argentina, where Herrerasaurus lived, is a stratum from a time when the climate changed dramatically from a relatively humid environment to a semi-arid climate.
It was also a time when medium-sized predators like Herrerasaurus and small herbivorous dinosaurs were diversifying.
The one in the back is a restored model.
Herrerasaurus was an apex predator in the ecosystem at the time, but it was by no means the dominant presence.
The overwhelming majority in the ecosystem at that time were herbivorous animals such as Hyperodapedon (rhynchosaurs) and Exaeretodon (cynodonts close to the ancestors of mammals). Also, the apex of the ecosystem was ruled by Saurosuchus (pseudosuchian), a giant quadrupedal carnivore that reached up to 7 meters in total length.
It is thought that Herrerasaurus established a niche (ecological niche) by preying on abundant small herbivores and other early small dinosaurs that lived at the same time, while avoiding direct conflict with the giant Saurosuchus.
Furthermore, studies scanning the brain cavity (endocast) of closely related species have confirmed that their brains had a specific region of the cerebellum that was greatly developed.
This is the part that controls the coordinated motor control of the head and eyeballs, indicating that they were able to agilely control their own bodies while visually and accurately tracking moving prey. Herrerasaurus was not an ambush predator, but a pursuit hunter boasting high athletic ability.
Intraspecific Combat and Ecology
Skull fossils of early carnivorous dinosaurs like Herrerasaurus are often found with healed head and facial injuries.
As a result of detailed research, it has become clear that these wounds are not post-mortem deformations, but "facial bite marks" caused by fierce combat between members of the same species.
Such facial biting behavior is consistent with behavioral patterns frequently observed in modern crocodilians during territorial disputes and male-to-male combat over mates.
While later dinosaurs (those closer to birds) came to avoid conflict through visual displays using feathers, it is speculated that Herrerasaurus had violent social behaviors similar to modern crocodilians.
Discovery and Classification
Between 1958 and 1959, Victorino Herrera, a rancher in the Andes Mountains of Argentina, discovered the first fossils at a dry excavation site around San Juan Province.
The genus name was given the meaning "Herrera's lizard" in honor of this discoverer, and it was described by paleontologist Osvaldo Reig in 1963.
Because the fossils were extremely fragmentary at the time of discovery, differences in shape due to the growth stage of individuals were misidentified as different species of dinosaurs, and fossils found from the same stratum were described as separate genera such as "Ischisaurus" and "Frenguellisaurus".
However, in 1988, a joint expedition led by Paul Sereno discovered a nearly complete skeleton, revealing that these were respectively a "juvenile individual" and a "mature large individual" of Herrerasaurus, and they were all integrated into Herrerasaurus.
Also, Herrerasaurus is in an important position in the early evolution of dinosaurs.
In the past, there was a time when it was thought to be an "ancestor just before the birth of dinosaurs (outgroup of dinosaurs)" based on features such as the pelvis. However, currently, because structures unique to dinosaurs, such as special joints in the spine (hyposphene-hypantrum articulation), have been confirmed, the mainstream view is that it is a "basal (early) theropod" that evolved as a dinosaur, or a "basal (early) saurischian" before theropods and sauropodomorphs split.
Herrerasaurus Stamp and Fossil Gallery
