Episode 527: Zofia Kielan-Jaworowska led several expeditions to Mongolia where her team discovered hundreds of mammals and dinosaurs including Deinocheirus and the Fighting Dinosaurs (a velociraptor and Protoceratops who appear to have fossilized in the middle of a fight to the death).

Two great books written by Zofia:

• In Pursuit of Early Mammals source
• Hunting for dinosaurs source

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The dinosaur of the day: Deinocheirus (revisited)

• Ornithomimosaur that lived in the Late Cretaceous in what is now Mongolia (Nemegt Formation)
• Lived about 70 million years ago
• Type species is Deinocheirus mirificus
• Named in 1970 by Halszka Osmólska and Ewa Roniewicz
• Genus name means “horrible hand”
• Genus name due to the size of the arms and strong claws
• Species name means “unusual” or “peculiar” because of the structure of the arms
• Holotype found on a small hill in poorly cemented sandstone
• Most of the skeleton seems to have eroded away
• From Zofia’s Hunting for Dinosaurs book, published in 1969 about how she found the holotype on July 9, 1965:
• “While I was walking in the rain along the southern part of the outcropping, I suddenly noticed some fairly large bones showing on a small hill. There were more than a dozen of them, and they were lying at a fairly shallow level. One protruding bone was about a yard long and rather thin. Nearby, a few large phalanges almost a foot long were sticking out of the sand. I began removing the sand from around the bones. Suddenly I saw there in the sand an excellently preserved, powerful, strongly arched claw twelve inches long. It was undoubtedly a forelimb claw, but larger than any ever found before. The predatory dinosaurs known to have roamed the Gobi, the tarbosaurs, had very short and shrunken forelimbs whose claws were never longer than two inches, even in the largest specimens. The longer claws on the tarbosaurs’ hind legs were never longer than four inches, in other words only a third the length of the claw I had just unearthed. The large herbivorous sauropods also had clawed limbs, but their claws were much smaller and quite differently shaped. The partly bare protruding bone looked like an arm bone; if this was actually the case it meant I had come across a long forelimb bearing claws bigger than any ever seen before.”
• “I looked around for someone to share my sensational discovery. Far away against the horizon I saw the bent silhouette of Wojtek Skarzynski. I called out to him, and we began to remove the sand together. It was time to go back for supper. We left all the bones in their original positions so as to be able to make an accurate sketch of their disposition, and started back to camp. There at supper I tried to tell the story, but my listeners were incredulous. A claw a foot long? There was no such animal!”
• Found the shoulder girdle and two forelimbs
• Found three claws for one limb but none for the other
• Found a few rib fragments
• Length of the shoulder bone was 5 ft (1.5 m)
• Estimated the forelimbs with the long sharp claws were 8.5 ft long (about 2.6 m)
• “Further digging unfortunately remained fruitless, the shoulder girdle and forelimbs were all that remained of this strange dinosaur, the remainder having disintegrated long ago.”
• Zofia looked through the literature and couldn’t assign it to any known family of dinosaurs
• Positioning of fingers were same as theropods
• “Undoubtedly we had found a representative of not merely a different species or genus, but of an altogether new family of theropods”
• Found the holotype to likely be an adult, fully grown
• In the paper that named Deinocheirus, mentioned the left hand looked like it had injuries, based on grooves and pits and injury scars with rounded edges, probably from damage to the joint
• Said “Deinocheirus seems to be a very peculiar theropod”
• Holotype includes both arms, minus the claws of the right hand, the complete shoulder girdle, parts of three back vertebrae, five ribs, belly ribs (gastralia)
• No more fossils found for almost 50 years, and Deinocheirus was a big enigma or mystery
• Two more specimens described in 2014, and they were repatriated to Mongolia
• One was a subadult and damaged by fossil poachers
• The other was a little larger than the holotype and had the same left arm as Deinocheirus, which helped identify it. Also had been excavated by poachers (took the skull, hands, and feet, but left a toe bone). Probably got poached after 2002, based on money left in the quarry
• Have about 95% of the skeleton, between the three specimens
• One new skeleton found in 2006, and the other in 2009, in the Korea-Mongolia International Dinosaur Expedition, but they were both missing parts (skull and feet)
• François Escuillié, director of a fossil dealership in France, saw the skull and feet in a private European collection, and in 2011 he asked Pascal Godefroit from the Royal Belgian Institute of Natural Science in Brussels to take a look
• Turns out the fossils had gone through Japan, China, France, and Germany
• Found the skull fit with the body that was found in 2006
• The toe bone fit perfectly into the foot, the bone and sediments around it were the same color and there was no overlap in any of the bones and they all belonged to an individual that was the same size
• They acquired the fossil and donated it to the Royal Belgian Institute, which has an agreement to repatriate stolen Mongolian fossils
• Fossils were repatriated to Mongolia on May 1, 2014, and went to the Central Museum of Mongolian Dinosaurs, along with a Tarbosaurus skeleton
• A Korean-Mongolian fossil hunting team found belly ribs in 2012
• There’s a rumor a Deinocheirus juvenile skull was poached and is out there somewhere
• One estimate that hundreds of partial or complete dinosaur skeletons have been poached from Mongolia, because there are so many bones and they’re fairly easy to find
• In the 2014 paper by Yuong-Nam Lee and others, said “The discovery of the original specimen almost half a century ago suggested that this was an unusual dinosaur, but did not prepare us for how distinctive Deinocheirus is—a true cautionary tale in predicting body forms from partial skeletons, even for animals in which the relationships are known”
• Tom Holtz said in an interview that Deinocheirus looked like the “product of a secret love affair between a hadrosaur and Gallimimus”
• Before the other specimens were found and only the arms were known, estimates ranged from 2 to 13 tons, and even larger sizes, based on comparing the arms to those of tyrannosaurs
• Now know that the largest known specimen is about 36 ft (11 m) long and estimated to weigh 7 tons (about 6.4 metric tonnes)
• About 16 ft (5 m) tall
• Body similar in size to Tyrannosaurus rex
• A 2015 study cut into bone samples and found Deinocheirus likely had a fast metabolism and grew quickly before reaching sexual maturity
• Had ten neck vertebrae, and an S-curved neck
• Bulky body, but had lots of hollow bones (air sacs, which kept it lighter)
• Had a narrow body, even though it was bulky
• Had a U-shaped wishbone
• Had a large belly
• Part of the pelvis (hips) were large compared to other ornithomimosaurs, and helped support its weight
• Not built for speed, even though it was an ornithomimosaur
• Probably moved slowly, based on the thick legs and wide hips
• Couldn’t run fast, but its large size may have been its best defense against predators
• Had a low narrow skull, with a long snout
• Skull was over 3 ft (1 m) long
• Had small eyes
• Had a good sense of smell, based on CT scans of its braincase
• Brain was proportionally small and compact
• Had a wide bill and deep lower jaw, like hadrosaurs
• No teeth, and jaws were down-turned
• Lower jaw size was closer to tyrannosaurids than other ornithomimosaurs
• Had a slender upper jaw
• Snout flares out to the sides
• Had a rounded, flattened keratinous beak
• Had some of the longest arms known of any two-legged dinosaurs
• Had very large arms, at almost 8 ft (2.4 m) long, with large, blunt claws
• Had three fingers on each hand, that were all about the same length
• Had a large bump on its back, supported by its back bones
• Could be a hump or sail or ridge on the back
• Had relatively short legs
• Had short, broad feet
• Last bone in the toes were flattened with a blunt tip, so somewhat hoof-like
• Foot claws may have helped it wade in water and not sink in mud
• Tail ended in a fan of feathers (had something like a pygostyle, with at least two fused bones)
• At first thought to be a predator that used its giant arms to tear apart prey
• But not long after, in 1970, Anatoly Konstantinovich Rozhdestvensky compared its arms to sloths, and suggested Deinocheirus climbed and ate plants and animals it found in trees
• In 1988 Gregory Paul suggested the claws were too blunt for a predator but could be used for defense
• Probably omnivorous, and ate plants and fish (plants and fish scales were found with one specimen and gastroliths also found)
• Because of the beak, probably foraged for food in the water or browsed near the ground
• Had a weak bite force
• Probably ate soft plants or water plants
• A 2017 study suggested Deinocheirus could pull lots of plants out of water with its claws
• Had a large tongue, which may have helped it suck in food from the bottom of water
• One specimen found with over 1,400 gastroliths among the ribs and belly ribs
• Probably helped it grind food
• A 2022 study found Deinocheirus to be a specialized feeder, based on the patterns of stress and strain on its jaws
• Bite marks found on Deinocheirus bones
• Bite marks on Deinocheirus match Tarbosaurus teeth, according to a 2012 study
• Bite marks found on two gastralia of the holotype, probably from punctures, gouges, and more from Tarbosaurus (could be why the holotype was scattered). Bite marks not found anywhere else on the body, so seems the Tarbosaurus focused on eating internal organs
• Lived in an area with lots of rivers
• Other animals that lived around the same time and place include mollusks, birds, and dinosaurs including the ankylosaur Tarchia, the pachycephalosaur Prenocephale, hadrosaurs like Saurolophus and Barsboldia, sauropods like Nemegtosaurus, tyrannosauroids like Tarbosaurus, and troodontids like Zanabazar

Fun Fact:

Zofia Kielan-Jaworowska discovered the “marsupial bone” in multituberculates (the epipubis, which may support the pouch in marsupials and are also in non-pouched mammals, like monotremes and eutherians)

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