In our 157th episode, we got to chat with Dr. Michael Habib, Assistant Professor in the Keck School of Medicine of USC and a Research Associate in the Dinosaur Institute at the Los Angeles County Museum of Natural History. He is a paleontologist and biomechanist, who studies prehistoric animals and how they moved. He’s known for his work on pterosaurs, feathered dinosaurs, and the origin of flight in birds. Follow him on Twitter @aeroevo.

Episode 157 is also about Amargasaurus, a sauropod with spines on its neck and back.

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In this episode, we discuss:

News:

The dinosaur of the day: Amargasaurus

Sauropod that lived in the Early Cretaceous in what is now Argentina (La Amarga Formation)

Name means “La Amarga lizard”, or “bitter lizard”

In Spanish, the word amarga means “bitter”

La Amarga is the name of a nearby town and the formation where it was found

Guillermo Rougier found Amargasaurus in 1984, during an expedition led by José Bonaparte (it was the 8th expedition of the “Jurassic and Cretaceous Terrestrial Vertebrates of South America” project)

Only one skeleton was found, and it’s mostly complete (includes a fragmentary skull)

Described in 1991 by Leonardo Salgado‭ and ‬José Bonaparte

Only species is Amargasaurus cazaui

Species name is in honor of Luis Cazau, a geologist at the YPF oil company, which was state-owned at the time (Cazau told Bonaparte and his team about the formation in 1983, which led to the discovery)

First unofficially mentioned in 1984 in the Italian book Sulle Orme dei Dinosauria, by Bonaparte (called Amargasaurus groeberi, though the species name changed)

Small for a sauropod (30-33 ft, or 9-10m long)

Weighed about 3 short tons

Had a short neck, compared to other sauropods

Part of the family Dicraeosauridae, which includes Dicraeosaurus, Brachytrachelopan, Suuwassea (had shorter necks and were smaller than other sauropods); Dicraeosauridae is part of Diplodocoidea

Had two rows of tall spines on its neck and back

Spines from the second to last dorsal vertebra to the first tail vertebrae were really long, but were in a single row and paddle-shaped

Salgado and Bonaparte first suggested that the spines were used for defense; in 1999 Salgado said the spines may have supported a keratinous sheath; Gregory Paul said in 2000 that if the spines had a keratinous sheath, they could have been used to fight against predators and other Amargasaurus, and it may have been able to point its spines forward by bending its neck, and Amargasaurus could shake its neck to make sounds with the spines; Mark Hallett and Mathew Wedel said in 2016 that the spines that were backward-directed may have been able to skewer predators, when the neck is abruptly pulled back in an attack (similar to what a giant sable antelope and Arabian oryx can do to defend themselves against lions)

Jack Bailey said in 1997 that Amargasaurus may have had a sail, since the spines were similar to Dimetrodon, which had a sail. Since there were two rows of spines, it doesn’t seem likely it had two parallel sails. Bailey said the spine may have been like a scaffold that was covered in skin

Not everyone agrees, and Gregory Paul said the sails could reduce neck flexibility, and that the spines were circular in cross-section and not flattened, like in other animals with sails

In 2007, Daniela Schwarz and others said that the spines on diplodocids and dicraeosaurids enclosed an air sac, which would be connected to the lungs and part of the respiratory system. But in Amargasaurus, the upper two-thirds of the spines would have been covered by keratin, which would mean the air sac could only be in the lower one-third of the spines

Bailey said the paddle-shaped spines at the tail end were like modern humped ungulates like bison, which may mean Amargasaurus had a fleshy hump above its hips (Bailey has also said other dinosaurs may have had humps, like Spinosaurus and Ouranosaurus)

Spines may also have been used for display, or to show dominance

Spines meant Amargasaurus couldn’t raise its neck vertically

Salgado said in 1999 that Amargasaurus may have had its head in a nearly vertical orientation

May not have had a great sense of hearing (based on a 2014 study by Carbajal and others who CT-scanned the skull)

Carbajal and others said that, based on their 3D model of the inner ear (the orientation of the semicircuar canal which helps with balance), Amargasaurus snout faced downward, and the neck was gently sloping downwards, and it may not have been able to raise its neck more than 9 ft (3m)

Probably had a broad snout and pencil-like teeth

Quadrupedal, but probably couldn’t rear up on its hind legs

Amargasaurus probably ate food at mid-level height

Other sauropods that lived around the same time and place included Zapalasaurus, Amargatitanis, and unnamed basal titanosauriforms

Amargasaurus probably ate food at 9 ft high, while Zapalasaurus, a rebbachisaurid, ate at ground level, and Amargatitanis, a titanosaur, ate at higher levels

Other dinosaurs, in addition to sauropods, included the stegosaur Amargasetgos, the ceratosaur Ligabueino, and some sort of large tetanuran

Other animals included the mammal Vincelestes and the crocodylomorph Amargasuchus

Forelimbs were shorter than hindlimbs

Had a wide pelvic region

Had five digits on its hands and feet

Salgado and Bonaparte said in 1991 that Amargasaurus was a slow walker, because it had proportionally short forearms and hindlegs, but in 1999 Gerardo Mazzetta and Richard Fariña said that Amargasaurus could do rapid locomotion (legs were more sturdy than a rhinoceros, which can gallop)

Skeleton is stored in the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires

Amargasaurus was considered for Disney’s Dinosaur movie in 2000 (Ricardo Delgado made a concept design with giraffe-like spots), but it was cut

Can see an Amargasaurus replica, named Margie, at the Melbourne Museum

Can also see an Amargasaurus replica at the Mind Museum in the Philippines as part of “Dinosaurs Around the World – Passport to Pangea,” which runs until March 2 of next year

Fun Fact:

Volcanoes can cause large expulsions of sulfur similar to the Chicxulub impact. Krakatoa released about 20 Megatons of sulfur and dropped global temperatures by about 1.2 °C (2.2 °F) for 5 years.

Sponsor:

This episode is brought to you in part by TRX Dinosaurs, which makes beautiful and realistic dinosaur sculptures, puppets, and exhibits. You can see some amazing examples and works in progress on Instagram @trxdinosaurs