Episode 455: The Fastest Dinosaurs. Plus two new dinosaurs: A new iguanodontian Oblitosaurus, the largest known ornithopod from the Late Jurassic in all of Europe; and Furcatoceratops, a close relative of Nasutoceratops.

News:

• A new iguanodontian dinosaur, Oblitosaurus, whose name means “obsolete” or “forgotten” lizard; But its an important find source
• There’s a new ceratopsid, Furcatoceratops elucidans, a close relative of Nasutoceratops that was already 10ft long at only 2 to 3 years old source

Listener Question:

What was the fastest dinosaur?

The dinosaur of the day: Sinornithomimus

• Fastest dinos are ornithomimosaurs, and we’ve covered a bunch of them
• From a 2015 paper by James Farlow and others on theropod locomotion: Cursoriality is something we’re not sure what it is, but we think we know it when we see it
• Hard to know exactly how fast dinosaurs could run
• Ornithomimid that lived in the Late Cretaceous in what is now Inner Mongolia Autonomous Region, China (Ulansuhai Formation)
• Lived about 90 million years ago
• Looked somewhat ostrich like, but with a shorter neck and a longer head and longer tail
• Ornithomimids had toothless jaws with beaks and long necks, and long arms and legs
• Had a relatively short neck and head, for an ornithomimosaur
• Estimated to be 8.2 ft (2.5 m) long and weighed about 201 lb (91 kg)
• Had slender arms
• Type species is Sinornithomimus dongi
• Described in 2003 by Yoshitsugu Kobayashi and Lü Junchang
• Genus name means “Chinese bird mimic”
• Species name is in honor of Zhiming Dong, who found the fossils
• Most completely known ornithomimid
• At least 25 individuals found, ranging in age from one to seven
• Fossils first excavated in 1997, as part of the Mongol Highland International Dinosaur Project (first spotted in 1978)
• Found in a bonebed, of at least 14 skeletons (each one had gastroliths), 3 sub-adults to adults and 11 juveniles (9 were nearly complete and mostly uncrushed)
• Holotype is a subadult
• In the first expedition, they ran out of time, but managed to collect multiple skeletons
• In 2001, a second expedition found more skeletons
• Bonebed has been compared to Pompeii (that’s how well preserved they are—one article said they even knew the size of the dinosaur’s eyeballs)
• Expedition team had to deal with lots of dust storms in the Gobi Desert
• Team in the second round had some help digging (had to treat the area carefully—need to look at the surroundings to know what happened to the dinosaurs, not just dig out the skeletons)
• Paul Sereno wrote about the experience in 2011, and said toward the end of their expedition, they had a day off and played a game of basketball at the Chinese army outpost. They noticed the heavy equipment and ask officials at the base if they could help excavate the dinosaurs. They had many rounds of baijiu, and a few days later, the team got a bulldozer
• Bulldozer removed the hill for them, so the team could excavate the last 13 individuals. Also found the skull of an unknown predator
• A 2008 paper studied the graveyard
• No evidence the bones moved after the dinosaurs died, and the bones were unweathered and in siltstone and layers of clay, so it’s likely they all died in a catastrophic event
• Crab-like animals found around them, which shows the dinosaurs were covered in water shortly after they died (they’re very well preserved)
• Found they were trapped in the mud
• Modern animals rarely die stuck in mud, so wasn’t clear at first that’s what happened to the dinosaurs
• Has to be just the right conditions, with low water levels, and those conditions may only last a few days
• When stuck in mud, usually die from dehydration, starvation, and/or predation
• Some hip bones missing, which may have been from a scavenger eating meat around the hips after they died
• No signs of weathering or tooth marks
• No shed theropod teeth found around the skeletons
• But skeletons were mostly facing the same direction
• Most of the individuals legs were stuck in the mud, with their bodies lying flat
• Some of the tails stuck/plunged in mud
• One skeleton had fallen on top of another
• Probably were walking around looking for water at the edge of a drying lake, and fell into the mud
• Marks in the mud around the skeletons shows they tried to get out of the mud
• Would have died a slow death, stuck in the mud (and flailing would attract predators and scavengers)
• Since bonebed/graveyard found with mostly juveniles (no adults, no hatchlings), seems the juveniles spent their time together and then maybe joined the adults once they were grown up
• Safety in numbers from predators
• Possible the adults focused on nests or brooding, and so juveniles lived together
• Got better at running as it grew up (adults had relatively longer lower legs)
• Took about 10 years to reach maturity
• Holotype had a 12.5 in (32 cm) long femur
• As it grew, the ratio of the tibia to femur (leg bones) of Sinornithomimus increases
• Similar to tyrannosaurids
• Seems ornithomimids and juvenile tyrannosaurids were similarly good at running
• Fossils found with gastroliths in the stomach areas, so likely it was herbivorous, or at least more herbivorous than omnivorous
• Gastroliths are stones they swallowed to help grind food in their stomachs
• Larger individuals had larger gastrolith masses
• Ornithomimids often thought to be omnivorous because of their beaks
• Another ornithomimosaur found with what’s probably gastroliths (pebbles found in the abdomen) was Shenzhousaurus, which lived in the Early Cretaceous in what is now China
• Not only found gastroliths, but also a thin film of black carbon coating on the sides of the gizzard (the plants the dinosaur ate)
• Lived in an arid to semi-arid environment
• Other dinosaurs that lived around the same time and place include the theropods Chilantaisaurus and Shaochilong, the ankylosaur Gobisaurus, and the pachycephalosaur Sinocephale, and iguanodonts

Fun Fact:

Some dinosaurs like Megalosaurus and Iguanodon weren’t given species names at first.

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