Episode 550: Herrerasaur Hurrah!. Herrerasaurs are some of the earliest known dinosaurs and these Triassic carnivores have been found all over the world. They’re a confusing group, but thanks to pathologies and fossilized poop we know a bit about how they behaved.

News:

• There’s a new herrerasaur dinosaur, Maleriraptor kuttyi source
• Herrerasaurs probably bit each other on the face source
• Herrerasaurs were a successful, complicated group source

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The dinosaur of the day: Sanjuansaurus

• Herrerasaurid dinosaur that lived in the Late Triassic in what is now Argentina (Ischigualasto Formation)
• Looked similar to Herrerasaurus but had some slightly more basal features
• Walked on two legs, had long arms, had a long(ish) head, and a long tail
• Had sharp teeth
• Similar in size to a medium-sized Herrerasaurus
• Herrerasaurus could grow to 6 m (20 ft) long and weigh around 350 kg (770 lb)
• Slightly larger than Staurikosaurus
• Staurikosaurus estimated to be at least 2.1 metres (6 ft 11 in) long and weigh 12 kilograms (26 lb)
• Thighbone was about 15.6 in (39.5 cm) long
• Type and only species is Sanjuansaurus gordilloi
• Named in 2010 by Oscar Alcober and Ricardo Martinez
• Genus name means “San Juan Province lizard”
• Genus name refers to San Juan Province, Argentina, where it was found
• Species name in honor of Raul Gordillo, head fossil preparator and artist at the San Juan Museum
• Fossils found in 1994 in gray-green sandstone
• Found a partial skeleton, including jaw fragments, most of the spine and tail bones, shoulder blades, part of the arm(ulna), part of the hips, parts of the legs
• Overall well preserved
• Skeleton incomplete because some of the bones were lost before it was buried
• Part of the back bones were lost though while the specimen was being prepared (3rd, 4th, and part of the 4th back bone)
• All the bones were found close together and there are no duplicate bones so they probably came from a single individual
• Lots of similarities in the skull, neck and back bones, hips, and shoulders to Herrerasaurus
• Details in the neck bones and neural spines, as well as the hips, make it unique (things like the pubis being relatively short, and neck bones having some shelf-like features)
• Pubis bone (part of the hips) is different (points toward the skull instead)
• Pubis was 63% the length of the femur (thighbone)
• Compared to 91% in Herrerasaurus and 70% in Staurikosaurus, 90% in Tawa, and 80% in Eoraptor
• Had a rough scar on the femur (thigh bone)
• In other dinosaurs like Herrerasaurus, Eoraptor, Panphagia, Tawa, Guaibasaurus, and Saturnalia, the scar is relatively small and smooth
• Arm bone was more gracile than Herrerasaurus but similar in shape
• Had 9 neck bones
• Had three vertebrae in the sacrum
• Discovery helps show there were lots of different types of dinosaurs around (so it wasn’t like dinosaurs gradually dominated)
• Lived in an area with active volcanoes, forests, and lots of seasonal rain
• Climate was warm and humid
• Other dinosaurs that lived around the same time and place include Herrerasaurus, Eoraptor, Chromogisaurus, Panphagia
• Other animals that lived around the same time and place include rauisuchians (carnivores with theropod-like skulls), rhynchosaurs (beaked reptiles), aetosaurs (spiny armored reptiles) and dicynodonts

Fun Fact:

The oldest known dinosaurs only left behind traces of their existence.

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