The Big Dinosaur Podcast

Episode 378 is all about Pinacosaurus, One of the best known ankylosaurs with dozens of known specimens including juveniles.

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In this episode, we discuss:

News:

• A new spinosaurid, Iberospinus, was described after a new excavation uncovered additional fossils source
• A large group of Tethyshadros dinosaurs were found in Italy source
• The Mill Canyon Dinosaur Tracksite in Utah was badly damaged recently source
• A man allegedly stole a $25,000 dinosaur claw from the Tucson Gem and Mineral Show source
• The Long Island Children’s Museum in New York has a new exhibit called “The Age of Dinosaurs” source
• Antarctic Dinosaurs: The Exhibition has moved to the Buffalo Museum of Science in New York source
• We got more details about the characters of Marvel’s Moon Girl and Devil Dinosaur source
• A new miniseries called Jurassic League, will feature Justice League characters as anthropomorphic dinosaurs source
• The official Jurassic World Dominion trailer was released including some feathered dinosaurs source

The dinosaur of the day: Pinacosaurus

• Ankylosaur that lived in the Late Cretaceous in what is now Mongolia and China (Bayan Mandahu Formation and ?Djadokhta Formation)
• Looked kind of like Ankylosaurus, with a body covered in armor (less spiky) and a club tail
• Estimated to be 16.4 ft (5 m) long and weigh up to 2 tonnes
• Medium-sized
• Not as robust as other ankylosaurs
• Had a flat body
• Had robust arms and legs
• Had five digits on each hand and three digits on each foot
• Had hoof-shaped claws
• Adults have skulls that are longer than they are wide
• Armor on the upper snout consists of a fused mass
• Had bone tiles on its head
• Had nostrils that formed a depression and had between three and five smaller holes (unclear why)
• Had cheek horns
• Had a smooth beak
• Had rows of small teeth
• Had osteoderms on the neck, back, and tail (juveniles didn’t have osteoderms on the tail)
• Had two cervical halfrings protecting the neck
• Had long, flat, triangular spikes on the body and tail
• Had smaller oval osteoderms in parallel rows on the back
• Had a relatively small tail club
• Pinacosaurus was the earliest specimen Phil Currie and Victoria Arbour studied in 2011, that had a complete tail club
• They compared the tails of ankylosaurs, and said it was most likely that ankylosaur tails stiffened before the knob or club at the end of the tail formed to maximize its effectiveness as a weapon
• Type species is Pinacosaurus grangeri
• Fossils first found in 1923 by Walter Granger
• Named in 1933 by Charles W. Gilmore
• Genus name means “plank lizard”
• Genus name refers to the plank scutes that covered the head
• Species name is in honor of Granger
• A second species, Pinacosaurus mephistocephalus, named in 1999 by Pascal Godefroit, based on a specimen found in 1996 in Bayan Mandahu during a Belgian-Chinese expedition
• Species name refers to the “devilish” squamosal horns and means “Mephistopheles’s head”
• Pinacosaurus mephistocephalus fossils include a well-preserved skull, lower jaws, a lot of the postcranial, including cervical armor and tail club
• Second species specimen found during the second excavation campaign of the Sino-Belgian Dinosaur Expedition in 1996
• The left arm, part of the pelvic girdle, and hindlimb are missing
• Wrote that the “skeleton was not deformed by pressure after burial and there is no evidence of post-mortem transportation”
• Probably a subadult
• Second species is about 10 ft or 3 m long (had a smaller skull than the holotype)
• Differences in the nostril region from the type species
• “The nasal is by far the largest bone of the skull roof, forming more than half of the length of the skull”
• Similar skull shape to the juvenile Pinacosaurus grangeri specimen
• Premaxilla not completely covered by nasal and accessory dermal plates, like in Pinacosaurus grangeri
• In 2010, Gregory Paul suggested Pinacosaurus mephistocephalus was a junior synonym of Pinacosaurus grangeri, but in 2012 Robert Hill said it was valid and Victoria Arbour and Michael Burns confirmed
• In 2014 Victoria Arbour wrote about the systematics, evolution, and biogeography of ankylosaurs
• Young in 1935 referred a third species, Pinacosaurus ninghsiensis based on similarities in the teeth and jaws. Now it’s considered to be Pinacosaurus grangeri
• In 1971 Maryanska said Pinacosaurus ninghsiensis was a junior synonym of Pinacosaurus grangeri, and other paleontologists have since agreed
• Maryanska also synonymized another dinosaur, Syrmosaurus viminicaudus, named by Maleev in 1952, with Pinacosaurus grangeri
• Gilmore first described the right ilium and tail vertebra without naming the dinosaur, then later in the year officially named it Pinacosaurus grangeri
• Holotype of Pinacosaurus grangeri found in the second Central Asiatic Expedition of the American Museum in the Flaming Cliffs
• Holotype includes a crushed skull, first two neck vertebrae, and osteoderms
• In Gilmore’s second description, published December 1933:
• Specimen is “so badly crushed and broken that much of its detailed structure is obscured, but in view of its unique occurrence, it seems worthy of description, although I am fully aware of the meagerness of its characterization”
• Badly crushed skull and jaws and a few scattered dermal bones
• Skull covered in scutes
• Teeth extremely small
• “Although badly crushed and checked in all directions, practically all parts of the skull and lower jaws are present”
• Viewed from above, skull has sub-triangular shape
• “It is evident that, as in other members of this family, the entire top of the skull is covered with ossified dermal scutes which completely obscure the underlying cranial elements”
• Other specimens, skull and skeleton of a juvenile, found in 1964 in a Polish-Mongolian Expedition, and in other localities of the Mongolian Gobi Basin by the Soviet-Mongolian Expeditions
• Robert Hill and others described a new juvenile specimen of Pinacosaurus grangeri in 2003, found in Mongolia (Ukhaa Tolgod); consists of a nearly complete skull
• Pinacosaurus grangeri was the second most common dinosaur found at Bayan Mandahu, after Protoceratops andrewsi
• Pinacosaurus mostly known from juveniles and sub-adults
• More than 30 skeletons found in 1969 to 1970 as part of Soviet-Mongolian expeditions
• Another 30 specimens found between 1993 and 1998 during Mongolian-Japanese expeditions
• Canadian expeditions found another 40 specimens between 2001 and 2006
• Teresa Maryanska described a well-preserved juvenile skull in 1971 and 1977
• There’s also more, not yet described, fossils found
• Eric Buffetaut referred ankylosaur fossils found in Shandong, China to Pinacosaurus sp. in 1995
• A juvenile specimen was described in 2015 as having a complex hyoid bone (tongue bone apparatus), which may mean it had a powerful tongue, to go with the small teeth that were replaced relatively slowly. Some extant salamanders have similar tongue bones and prehensile tongues. Possible Pinacosaurus ate some insects, or maybe tough leaves and pulpy fruits
• A paper in 2011 analyzed the quarry diagram of juvenile Pinacosaurus found in China, and said all were upright with their limbs positioned under their bodies
• In 2011 Michael Burns and others analyzed juvenile Pinacosaurus grangeri specimens found in China
• All of them had preserved skulls
• Found Pinacosaurus to be the most basal member of Ankylosaurinae
• Four specimens collected by the Canada-China Dinosaur Project at Bayan Mandahu and were prepared
• A fifth specimen found at an unknown site at Bayan Mandahu by the Silk Road Expedition
• The best specimens of the bunch were on display as part of a traveling exhibit called “The Greatest Show Unearthed”
• Most of the died in situ and were buried either during sandstorms or rainstorms
• Twelve more juveniles found in the Sino-Canadian Dinosaur Project
• All had the post-mortem insect borings
• In 2021, Gábor and others studied whether ankylosaurs from the Cretaceous lived alone or moved in herds
• Adult ankylosaurs often thought to be solitary because most skeletons found as isolated individuals
• But some MDAs found
• More than 30 juvenile Pinacosaurus skeletons collected between 1995 and 1996 by the Mongolian-Japanese Expedition in the Alag Teeg beds (though possible some of them were discovered before but left behind in the 1969 Soviet-Mongolian expedition)
• Possible Pinacosaurus was gregarious as juveniles (for protection), since MDAs had juveniles of similar sizes
• Possible they came together during a drought
• They were found in different localities which could mean this was “true gregarious behavior”
• But, still hard to know their social structure
• Lived in an arid to semi-arid environment with large open areas of low and sparse vegetation (good for multiple individuals gathering)
• Lived in a semi-desert
• Other dinosaurs that lived around the same time and place included ankylosaur Minotaurasaurus, alvarezsaurs Kol and Shuvuuia, oviraptorosaurs Citipati and Khaan, ornithomimosaurs, troodontids Almas and Byronosaurus, titanosaurs, ceratopsians
• Other animals that lived around the same time and place included amphibians, crocodylomorphs, lizards, mammals, pterosaurs, and turtles

Fun Fact: Baby penguins have been freezing to death in Antarctica due to rising temperatures and increased rainfall. But adult penguins have special adaptations that keep them warm in many extreme conditions.

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