Episode 417: Thescelosaurus had spikes coming out of its forearms. Plus more news from SVP including why tyrannosaurs had small arms; how raptors were like cheetahs; and potential theropod embryos with palatal teeth, osteoderms, and skin.
News:
- Presentations from the Dinosaur Macroevolution/Macroecology session of SVP 2022 source
- The Soft Tissues and Taphonomy talks from SVP 2022 source
Sponsors:

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The dinosaur of the day: Caenagnathus
- Caenagnathid oviraptorosaur that lived in the Late Cretaceous in what is now Alberta, Canada (Dinosaur Park Formation)
- Large, and may have been about as big as Anzu
- Looked similar to Anzu
- Looked bird like, with feathers and long legs
- Also had a long tail, and s-shaped neck, and probably had a crest on its head
- Thought to be around the same size as Anzu because of the known specimens of Anzu and Caenagnathus, the pubes are about the same size
- Anzu was about 11 ft (3.5 m) long
- Anzu may still have been larger (known specimens may not represent its max body size, and the specimens found may have still been growing)
- Estimated to weigh up to 212 lb (96 kg)
- Had a long, flattened, toothless lower jaw
- Had a shallow jaw, which is different from other oviraptorosaurs that are more like an upturned beak. May mean it ate more plants
- Caenagnathids probably were generalist feeders that ate plants, small animals, and maybe eggs
- Fossils found include lower jaws, tail vertebra, bones from the hand and limbs
- Type species is Caenagnathus collinsi
- Genus name means “recent jaw”
- Species name “in honor of the late Dr. W. H. Collins, for many years director of the Geological Survey of Canada”
- Described by R. M. Sternberg in 1940
- At first thought to be a toothless bird
- Jaws were found in 1936 and it was named Caenagnathus
- Sternberg wrote that “The holotype is an admirably preserved lower jaw, complete except for the ventral border of the right ramus”
- Holotype was found in the summer of 1936, a field party from the National Museum of Canada, under the direction of C.M. Sternberg
- In 1988, a different specimen that had been in storage since 1923 was rediscovered and studied, and it helped link several fragments of an oviraptorosaur into one dinosaur: Chirostenotes (covered in episode 404)
- Lots of debate and subsequent studies finding Chirostenotes and Caenagnathus to be separate
- In 2010, Phil Senter did a phylogenetic analysis of Coelurosauria and found Caenagnathus and Chirostenotes to be separate, “casting doubt on their synonymy”
- More complete caenagnathid specimens found in 2014 and 2015, like the discovery of Anzu, helped show more differences in the fragmentary specimens
- In 2015, Funston and others re-examined caenagnathid fossils from Dinosaur Park Formation, and found more Caenagnathus collinsi fossils, including a tail vertebra, femur, and parts of the feet
- Funston and Currie in 2020 described another Chirostenotes specimen with a lower jaw, that supported Chirostenotes and Caenagnathus being separate
- Differences in the feet and toes, between Caenagnathus and Chirostenotes
- In 2020, Gregory Funston re-examined caegnagthid material and redescribed Caegnathus collinsi (some disagreement over the diversity of caenagnathids)
- One of the specimens was at least 12 years old and nearly done growing
- Probably grew quickly at first, then slowed down
- In 1993, Phil Currie and others named “Caenagnathus” sternbergi, based on new specimens found in the Judith River Formation, but in a 2014 analysis it was found to be a sister taxon
- Other dinosaurs that lived around the same time and place include ankylosaurs, ceratopsians, ornithopods, pachycephalosaurs, ornithomimids, oviraptorosaurs, paravians, tyrannosaurs
- Other animals that lived around the same time and place include amphibians, crocodylians, lizards, plesiosaurs, pterosaurs, turtles, mammals, fish
Fun Fact:
Sometimes you can find growth marks in ribs to calculate a dinosaur’s age when the legs don’t have growth marks.
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