controversy Archives - The Big Dinosaur Podcast

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

You can listen to our free podcast, with all our episodes, on iTunes at:

Herrerasaurus, on display at the Royal Ontario Museum

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

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.

I Know Dino Podcast Show Notes: Herrerasaurus (Episode 27)