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Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

A #PrehistoricPlanet

Deinocheirus thread. For a lot of the viewers, this may have been your introduction to the duckbilled moose-camel ostrich dinosaur Deinocheirus. This guy: 1/

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12:59 PM · May 25, 2022Twitter Web App

Replying to

@TomHoltzPaleo

Back in 1965 the Polish-Mongolian Expedition found remains of a bizarre long-armed theropod (carnivorous) dinosaur unlike any known before: 2/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

Based on the huge arms and claws, in 1970 Halszka Osmólska and Ewa Roniewicz named it Deinocheirus mirificus ("the unusual terrible hand"). They were uncertain where it fit among the theropods. 3/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

When mounted, the arms were found to be about 2.4 m (nearly 8') long: the longest of any bipedal dinosaur. 4/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

As mentioned earlier, the position of Deinocheirus in the dinosaur family tree was uncertain. The default was that it was some weird long-armed predatory form, as shown in this speculative illustration by Varshamov in 1977. 5/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

However, anatomical similarities of the forelimbs of Deinocheirus to the ornithomimids (ostrich dinosaurs) led John Ostrom to speculate it was related to the these (much smaller) dinosaurs. Shown here is me with an Ornithomimus

For instance, like ornithomimids, but unlike nearly all other theropods, Deinocheirus had all three bones of the palm of the hand (the metacarpals) at almost the same length. Here is an ornithomimid hand. 7/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

But still, with only shoulder blades and forelimbs (and few vertebrae, ribs, and gastralia) this relationship was uncertain. Through the rest of the 20th Century and into the 2010s Deinocheirus remained mysterious. Here is the original specimen back in the 1990s. 8/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

In 2013 there was a spectacular announcement at the

@SVP_vertpaleo

meeting that was the talk of the conference: new Deinocheirus material had been found!! (Okay, the rumor mill had been talking about it for a few years.) 9/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

As it turned out, in 2006 and in 2009 additional specimens had been found by the Korea-Mongolian International Dinosaur Expedition and (sadly) by poachers collecting in the Nemegt. The poached specimens had been sold on the black market and wound up in Europe. 10/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

This included the skull and feet of Deinocheirus, neither of which had been known before. 11/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

Through the efforts of fossil trader Françoise Escuillé and paleontologist Pascal Godefroit, the poached specimens were reunited with the legally-collected material. It turned out they belonged to the same individual! In some cases, two ends of the same bone were rejoined. 12/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

Now, the full appearance of Deinocheirus began to take shape. 13/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

The skull was bizarre: deep jawed, ridiculously reduced jaw muscle openings, duckbilled. When I first saw it, I told reporter

@jeffhecht

it looked like "the product of a secret love affair between a hadrosaur and Gallimimus" 14/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

While it did indeed prove to be part of the Ornithomimosauria, it was a different branch of that group. Unlike the swift, agile ornithomimids (like Ornithomimus and Gallimimus), it was a beer-bellied, relatively short-legged form. 15/

102

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

Found with over 1400 gastroliths (stomach stones) and the remains of fish in its belly, it appears to have been an omnivore with at least some ties to freshwater (as show in #PrehistoricPlanet

(art by Michael Skrepnick) 16/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

It was a huge dinosaur, one of the largest in its environment.

@WScottPersons

and colleagues found it massed around 6.2 tonnes, bigger than nearly all theropods other than Tyrannosaurus rex, Spinosaurus, and a few of the carcharodontosaurs 17/

Thomas R. Holtz, Jr.

(he/him)

@TomHoltzPaleo

For a personal connection, I was lucky enough to be one of the reviewers for the initial paper on the new discoveries. It was the fastest turnaround of a review I have ever done: less than 24 hours. (Maybe I shouldn't have admitted that...) 18/

nature.com

Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificus

Nature - For almost 50 years, the strange theropod dinosaur Deinocheirus mirificus has been regarded as one of the most intriguing puzzles in palaeontology. Known only from two gigantic forelimbs...

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