The Big Dinosaur Podcast

Episode 27 is all about Herrerasaurus, one of the earliest known dinosaurs.

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In this episode, we discuss:

• The dinosaur of the day: Herrerasaurus ischigualastensis, whose name meas “Herrera’s lizard”, after the local rancher who discovered it
• Don Victorino Herrera, a local rancher, found the first Herrerasaurus fossil in 1958, in the schigualasto Formation of northwestern Argentina
• Researchers found three partial skeletons
• Osvaldo A. Reig named Herrerasaurus in 1963
• Harvard paleontologist Alfred Romer also found a partial Herrerasurus in the late 1950s, but local authorities impounded them in Buenos Aires for 2 years until Harvard claimed them
• Lived in Triassic, about 235-230 million years ago
• One of the earliest dinosaurs; early archosaur
• Although Herrerasaurus is one of the earliest dinosaurs, researchers may have discovered the earliest dinosaur in 2012 (Nyasaurus parringtoni, a dinosaur that lived 10 million years before Herrerasaurus, that was the size of a Labrador retriever, with a 5-foot long tail). The researchers are from UC Berkeley though they say they’re cautious about calling it the earliest dinosaur. Nysasaurus was excavated in the 1930s in Tanzania, and researchers recently found bone cells and blood vessels in the bones
• Controversy over what to classify Herrerasaurus: as sister to dinosaurs, as saurischian or as a theropod
• Redescribed in the Journal of Vertebrae Paleontology years later based on new fossils found by Paul Sereno of the University of Chicago (found the skull in 1988)
• Skull is similar to other Archosauriformes, like Euparkeria
• Didn’t find the first skull until 1988 (Sereno and his team thought the new material made Herrerasaurus a theropod, but others thought it was something else)
• Sometimes classified as basal theropod, sometimes as carnivorous saurischian, or sometimes even earlier in the evolutionary tree
• Herrerasaurus had an unusual pelvis (lacks a bone in the center of the hip socket, a key characteristic of dinosaurs
• Herrersaurus is now usually considered a basal theropod (meat eating)
• A new early theropod, Tawa, was discovered in 2009. Tawa put to rest debate about whether or not Herrerasaurus was actually an early theropod or some other type of animal (Herrerasaurus had large claws and teeth like theropods, but did not have airsac pockets in its vertebrae, which was unusual for a theropod
• Tawa was similar to Herrarsaurus (had similar pelvis) as well as airsac pockets in the backbone, as seen in other theropods. This showed that Herrerasaurus was a theropod because it’s unusual characteristics were not unique
• Categorizing Herrerasaurus as a theropod shows that dinosaurs quickly evolved into three lineages (sauropods, ornithischians, and theropods) and that all three were in South America, where Herrersaurus was found, as soon as dinosaurs appeared
• Synonyms for Herrerasaurus type species are Ischisaurus and Frenguellisaurus
• One large Herrersaurus specimen was first thought to be a new genus, Frenguellisaurus (named in 1986 by Fernando Novas). In 1992 Novas and Paul Sereno reclassified
• Herrerasaurus was 13 feet (3.9 m) long, 4 ft (1.1 m) tall at the hips, and weighed 460 pounds (210 kg)
• May have been cathemeral (active through day in short intervals)
• Bipedal, with long legs, long tail
• Was probably quick and agile (made it easy to catch animals scared out of hiding)
• Had a proportionately short femur and long lower leg bones, and walked on its toes to extend the length of its leg, and its pubis pointed backwards (seen in birds) so was probably agile and very fast
• Small head, long narrow skull
• Herrerasaurus‘ wrist and lower arm resembles modern birds (forelimbs could fold up like a pigeon’s) and may have had feathers
• Short arms and sharp claws, and sharp teeth
• Probably hunted small reptiles and smaller dinosaurs
• Blade shaped teeth with knife like serrations
• Found small bones in Herrersaurus corprolites, meaning they could digest bone
• Herrerasaurus has a sliding lower jaw (also seen in other reptiles); may have raked its teeth through prey or held small prey in its jaws
• Herrersaurus had a body shaped like large carnivores (such as Allosaurus) but lived in a time when dinosaurs were small and not at all dominant
• Although it was large, Herrerasaurus was probably not the top predator in its habitat
• Lived among bigger predators, like the giant crocodile relative Saurosuchus, and Fasolasuchus tenax, largest meat-eater in Argentina at the time
• Herrersaurus was probably the most common carnivore in the Ischigualasto Formation
• Ischigualasto Formation was a volcanically active floodplain with forests and strong seasonal rainfalls; moist, warm climate; vegetation includes ferms, horsetails, and giant conifers, which formed forests along the banks of rivers
• Herrersaurids are some of the oldest known dinosaurs (lived in Late Triassic; extinct by end of Triassic)
• They were small and carnivorous
• Fossils found in North and South America, and may have also lived on other continents
• Herrerasaurids have unusual anatomy with primitive and derived traits
• Herrerisauridae family has two other genera (Staurikosaurus from Brazil and Sanjuansaurus from Argentina)
• Fun fact: The word “dinosaur” means “terrible lizard.” However, the Greek word “dinos” also means “wondrous. So Sir Richard Owen, who named dinosaurs, may have meant they were wonderous, and not terrible, creatures.