Episode 576: A Dinosaur that Choked on Rocks. Plus a hatchling Allosaurus that was partially digested before fossilizing, T. rex tooth marks on Edmontosaurus, reviews of Netflix’s The Dinosaurs & The End of Oak Street, and more.

News:

• There’s a new enantiornithean bird, Chromeornis funkyi, and it choked to death on rocks source
• The shape of gastroliths can help us figure out how dinosaurs digested their food source
• Paleontologists found evidence of a poor hatchling Allosaurus being eaten source
• Tooth marks on Edmontosaurus bones likely show a T. rex was feeding or scavenging on it source
• Review of “The King and the Dragon” By S. Hunter Allred source
• Review of Netflix’s “The Dinosaurs” (link in show notes has behind the scenes clips) source
• Review of “The End of Oak Street” starring Anne Hathaway and Ewan McGregor source

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The dinosaur of the day: Stygivenator

• Maybe dubious tyrannosaur that lived in the Late Cretaceous in Montana, U.S. (Hell Creek Formation)
• On the small side
• Walked on two legs, had a long tail, a long, low skull
• Had sharp teeth
• Type species is Stygivenator molnari
• Considered for a while to be a species of Aublysodon (another dubious genus)
• Also considered to be a juvenile Tyrannosaurus
• Know from fragments, so hard to know for sure
• Part of the skull found near Jordan, Montana in 1966, by Harley Garbani (Hell Creek)
• Found alongside a Triceratops skull
• Specimen number is LACM 28471 (it’s in the Natural History Museum of Los Angeles County)
• Found part of the snout including the upper jaw, teeth, and also parts of the skull roof
• Ralph Molnar described the fossil in 1978, and said it had similarities to tyrannosaurs and dromaeosaurs, and considered it likely to be a big dromaeosaur
• Called it the “Jordan theropod” (too fragmentary to give it a name)
• In 1988, Gregory Paul considered it to belong to Aublysodon (named in 1868), a dubious carnivorous dinosaur known from Montana (Judith River Formation)
• Considered it a new species, so named it Aublysodon molnaris, after Ralph Molnar. Named based on one of the teeth. Molnar later agreed they were similar, but considered it to be the same as the type species of Aublysodon (Aublysodon mirandus)
• Aublysodon considered dubious, because its teeth are similar to many tyrannosaurs
• Aublysodon was named from one tooth
• Part of the confusion was the tooth was thought to be a premaxillary tooth (front of the jaw) but turned out to be a maxillary tooth (further back in the upper jaw), and Aublysodon was named from a premaxillary tooth
• George Olshevsky, Tracy Ford, and Seiji Yamamoto renamed Stygivenator in 1995, since Aublysodon was dubious
• Genus name means “Styx hunter”
• Name refers to the Hell Creek Formation, so kind of means “Hell Creek hunter” (In Greek mythology, River Styx is a mythical boundary river that separates the world of the living from the underworld)
• Species name is for Ralph Molnar
• For a while, Stygivenator had multiple species, but those are considered to be dubious juvenile tyrannosaurs
• Pete Larson argued in 2013 that Stygivenator may be a young Nanotyrannus, instead of a juvenile T. rex
• In 2024, Nicholas Longrich and Evan Saitta found Stygivenator to be its own distinct taxon
• Found it had similarities to Nanotyrannus, but also differences in the shape of the teeth and jaws (maxillae and dentaries)
• Also said there was a lot of variation in Nanotyrannus specimens
• On his blog, Nicholas Longrich wrote about Stygivenator’s long, low snout, that reminded him of the Nanotyrannus holotype
• Suggested that the Dueling Dinosaurs specimen (“Bloody Mary”) was not Nanotyrannus but rather Stygivenator
• Lindsay Zanno and James Napoli in 2025 said they consider Stygivenator to be a nomen dubium (too hard to definitively identify based it being fragmentary and poorly preserved) and that “Bloody Mary” had enough similarities with another Nanotyrannus lancensis specimen that they were both Nanotyrannus
• Gregory Paul in 2025 considered Stygivenator to be valid, and said it lived alongside Nanotyrannosaurus
• Likely they competed
• Though in Nicholas’s blog post, mentioned there was presumable niche partitioning
• Maybe Nanotyrannus could take down larger prey than Stygivenator
• Lived in the Hell Creek Formation, so lots of other dinosaurs around when Stygivenator lived, including Tyrannosaurus, Nanotyrannus, Triceratops, Edmontosaurus, Ankylosaurus (lots of the famous ones)

Fun Fact:

Paleontologists found an Iguanodon with a bacterial infection that led to an open lesion on its skin. source

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