In our 94th episode, we had the pleasure of speaking with Dr. Dave Varricchio from Montana State University.
Episode 94 is also about Raptorex, a tyrannosaurid that some think may be a juvenile Tarbosaurus.
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In this episode, we discuss:
- The dinosaur of the day: Raptorex
- Name means thief king
- Dubious tyrannosaurid genus
- Type species is Raptorex kriegsteini
- Species name is in honor of Roman Kriegstein, a Holocaust survivor (son Henry donate the specimen to the University of Chicago to be studied)
- Described in 2009 by Paul Sereno and others
- Tyrannosaurid Skeletal Design First Evolved at Small Body Size, published in 2009
- Reanalysis of “Raptorex kriegsteini”: A Juvenile Tyrannosaurid Dinosaur from Mongolia, published in 2011
- Considered by many to be a nomen dubium because tyrannosaurids tend to change a lot while growing, and there’s no adult skeleton to compare it to (it looks similar to juvenile Tarbosaurus); also originally it was thought to be from the Yixian Formation in China, and about 125 million years old, but now that’s thought to be unlikely
- Specimen was collected illegally and smuggled out of Asia
- Pete Larson, who tried to figure out the origins of the specimen, said an American businessman bought it from a Mongolian fossil dealer, and then sold it at the Tucson Gem, Mineral and Fossil Show. Dr. Henry Kriegstein, a fossil collector, bought it (at the time it was described as a juvenile Tarbosaurus) and he told paleontologist Paul Sereno about it, who said it was a subadult of a new species from the Yixian Formation. He published a description and arranged to send the fossil back to China, where he thought it had been smuggled from
- Sereno said it was about 6 years old and nearly an adult
- If this is true, it would mean that tyrannosaurs started as small animals with a large head, long legs, and two-fingered hands, instead of evolving into giants with those features. But previous evidence found that primitive tyrannosaurs had small skulls and long arms with three fingers on each hand
- In 2010 Pete Larson looked into the fossil and said it was probably a juvenile Tarbosaurus, and probably didn’t come from the Yixian Formation (which Sereno had concluded based on a fish fossil found alongside it). Larson said it may have come from Mongolia instead, from formations only 70 million years old, and said they needed “a more detailed analysis of the fossil matrix, including dating any pollen associated with the fossil.” Sereno said he still believed in his original analysis
- In June 2011, a detailed second study was published in PLOS ONE by Denver Fowler, Pete Larson, and others, and they found that the specimen was only 3 years old instead of 6, and found that the fossil Sereno used to date Raptorex, of a Lycoptera, was actually bigger than any known Lycoptera and was probably part of an ellimichthyiform fish, which lived during the entire Cretaceous period, so it’s unclear how old the Raptorex fossil is. Fowler and Larson and others said Raptorex was probably a juvenile tyrannosaurid, similar to Tarbosaurus, though it’s unclear what genera it belongs to exactly until more is known about tyrannosaurid growth patterns as well as more information about how old the Raptorex fossil actually is. If this conclusion is true, then Sereno’s hypothesis that tyrannosaurid features were in smaller versions of tyrannosaurs first would not be true
- In 2013, Newbrey and others said the fish fossil (formerly thought to be Lycoptera) found near Raptorex was actually a hiodontid, probably similar to the ones found in the Nemegt Formation in Mongolia (lived in the Late Cretaceous). This means Raptorex probably came from the Nemegt Formation and lived in the Late Cretaceous
- The hiodontid species found near Raptorex match with the species only known from the Nemegt Formation
- In 2011, Takanobu Tsuihiji wrote an in-depth description of a nearly complete juvenile Tarbosaurus, which helped to compare other juvenile tyrannosaurids, including Raptorex. They found that Raptorex and the juvenile Tarbosaurus had some differences, such as Raptorex not having a prominent crest on its upper hip
- This would mean Raptorex is its own genus, but Fowler, Larson and others don’t all agree on whether or not Raptorex has that crest on its hip (Larson wrote that there is a “subtle crest”).
- Still, the idea that tyrannosaurids evolved their traits at a smaller size seems to remain in doubt
- About 9.8 ft (3 m) long and weighed 143 lb (65 kg)
- Had a large skull, long legs (fast runner) and two-fingered forelimbs
- Had a large brain, and good sense of smell
- Fun fact: According to Dr. Ken Lacovara in the new VR video; Dreadnaughtus weighed less than a Boeing 737, despite weighing as much as 9 T-rex‘s and 12 full-grown male African elephants
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For those who may prefer reading, see below for the full transcript of our interview with Dr. Dave Varricchio:Continue Reading …