Retro vs Modern #20: Deinocheirus mirificus

Discovered in Mongolia in the mid-1960s, and named in 1970, Deinocheirus mirificus was a famous paleontological mystery for over 40 years.


1970-2000s

For a long time all that was known of this dinosaur was a few fragments and an enormous pair of arms – some of the largest of any known theropod at 2.4m long (7’10”) – inspiring its name meaning “wonderful terrible hands”.

Initially it was classified as a new type of carnosaur (which was something of a wastebasket group at the time), but similarities with the “ostrich-mimic” ornithomimosaurs were soon noted in the early 1970s. And despite some paleontologists trying to link Deinocheirus to the similarly big-armed therizinosaurs over the decades, the ornithomimosaur interpretation seemed to have won out by the early 2000s.

Depictions of Deinocheirus during this time period were highly speculative and reflected the uncertainty over its evolutionary relationships, varying from giant carnosaurs to therizinosaur-like forms to “Gallimimus but bigger” – or sometimes simply showing a hilarious pair of monster-arms reaching in from out-of-frame. Many popular dinosaur books just gave up entirely and only illustrated the known fossil material unreconstructed, and an iconic photograph of Mongolian paleontologist Altangerel Perle standing between the arms was commonly used to emphasize the sheer scale of the bones.


2020s

In the early 2000s attempts to find more fossil material at the original discovery site had only turned up a few additional fragments, including some belly ribs with evidence of having been bitten by a Tarbosaurus – suggesting that the specimen represented the scattered dismembered bits left behind by a feeding carnivore, and that the rest of the carcass might not even have fossilized.

But then between 2006 and 2009 a team of international paleontologists working in Mongolia found a couple of unusual partial skeletons at sites that had been looted by fossil poachers. While parts like the skulls and feet had been taken, the two specimens were still fairly complete and one still had enough arm material left to clearly identify it as Deinocheirus.

When the discovery was announced at the 2013 Society of Vertebrate Paleontology conference it was massive surprise to most of the paleontological community, confirming that Deinocheirus was indeed an ornithomimosaur, and that it was an incredibly weird one. Heavily-built, it was a much chunkier animal than its other relatives, and most surprising of all it had a humped “sailback” formed by long neural spines on its back vertebrae.

Then things got even better.

And stranger.

A “weird skull” had been spotted in the private fossil trade in Europe in 2011, along with some hand and foot material that perfectly matched the missing pieces of one of the new Deinocheirus specimens. The fossils were acquired and donated to a Belgian museum, and then finally were repatriated to Mongolia in 2014, filling in the rest of Deinocheirus’ appearance with a suitably surprising head to go with the rest of its body.

We now know Deinocheirus lived about 70 million years ago during the Late Cretaceous, in what is now the Gobi Desert but at the time was a river-delta-like environment with numerous river channels, shallow lakes, and mudflats.

It grew up to about 11-12m long (~36-39′) and had a long narrow skull with a wide beak and a deep lower jaw – resembling a hadrosaur more than an ornithomimosaur – and it had a rather small brain for a theropod of its size, proportionally closer to that of a sauropod. Its fairly weak jaw muscles suggest it mainly fed on soft vegetation, possibly foraging for aquatic plants in bodies of water like an enormous duck. Gastroliths in its gut helped to grind up its food, and the remains of fish in its stomach suggest that it was also somewhat omnivorous.

Its characteristic huge arms were actually one of the least strange things about it, and were actually proportionally smaller compared to its body size than other ornithomimosaurs. They were heavily muscled, though, with large curved claws, and may have been used to dig up food from mud and soft soil or to pull clumps of vegetation closer.

Its skeleton was highly pneumatized, full of lightening air sacs, but it was still a very big and bulky animal with relatively short legs that suggest it was rather slow-moving. Its feet resembled those of both hadrosaurs and tyrannosaurs, with blunt claws and adaptations for heavy weight-bearing in a bipedal stance.

The large sailback may have been a display structure, and the tip of its tail resembled a pygostyle and so may have sported a fan of feathers. The rest of its body was probably feathered similar to what’s known from other ornithomimosaurs, although potentially more sparsely due to its huge size.

Weird Heads Month #29: Giant Saw-Toothed Birds

The pelagornithids, or “pseudotooth birds”, were a group of large seabirds that were found around the world for almost the entire Cenozoic, existing for at least 60 million years and only going completely extinct just 2.5 million years ago.

Their evolutionary relationships are uncertain and in the past they’ve been considered as relatives of pelicaniformes, albatrosses and petrels, or storks, but more recently they’ve been proposed to have been closer related to ducks and geese instead.

Whatever they were, they were some of the largest birds to ever fly, and many of the “smaller” species still had wingspans comparable to the largest modern flying birds.

But their most notable feature was their beaks. Although at first glance they look like they were lined with pointy teeth, these structures were actually outgrowths of their jaw bones covered with keratinous beak tissue. While these bony spikes would have been useful for holding onto slippery aquatic animals like fish and squid, they were actually hollow and relatively fragile so pelagornithids must have mainly caught smaller prey that couldn’t thrash around hard enough to break anything.

The serrations also only developed towards full maturity, and the “toothless” juveniles may have had a completely different ecology to adults.

Pelagornis chilensis here was one of the larger species of pelagornithid, with a wingspan of 5-6m (16’4″-19’8″), known from the western and northern coasts of South America during the late Miocene about 11-5 million years ago.

Like other pelagornithids it was highly adapted for albatross-like dynamic soaring, with long narrow wings that allowed it to travel huge distances while expending very little energy – but with its proportionally short legs it would have been clumsy on the ground and probably spent the vast majority of its life on the wing, only returning to land to breed.

Island Weirdness #41 — Talpanas lippa

The big herbivorous moa-nalo weren’t the only unusual waterfowl on the ancient Hawaiian islands — and the island of Kauaʻi had a very odd duck indeed.

The Kauaʻi mole duck (Talpanas lippa) was fairly small, about 50cm long (1’8″), and although it lived alongside one of the moa-nalo species they don’t seem to have been closely related at all. It instead appears to have come from a different duck lineage entirely, with it’s closest living relatives potentially being the stiff-tailed ducks.

It had short chunky legs and an especially weird skull, with eyes so tiny and underdeveloped that it must have been near-blind and flightless. But the areas of its brain associated with the sense of touch were proportionally huge, and although the exact shape of its beak currently isn’t known it seems to have been very wide and flat.

It was probably a nocturnal bird that used an incredibly sensitive bill to grub around in the undergrowth for invertebrates, sort of an equivalent of the modern kiwi but with a face more like a platypus.

The only known Talpanas remains come from mid-Holocene deposits about 6000 years old, but since Kauaʻi is the geologically oldest of the main Hawaiian islands it may have existed there for several million years prior.

Like the moa-nalo it was likely driven to extinction due to human influences on its environment once Polynesian settlers reached the island, sometime between 300 CE and 1200 CE.