weird hands – Nix Illustration

Manipulonyx

Manipulonyx reshetovi was an alvarezsaurid theropod dinosaur that lived during the Late Cretaceous, about 70 million years ago, in what is now Mongolia.

Although only known from a partial skeleton, based on its close relatives it would have been about 50cm long (~1’8″), with a narrow snout, a coat of fluffy down-like feathers, long slender legs, and short stout arms with massively enlarged thumb claws.

Notably the fossil specimen has the best preserved hands known from the parvicursorine subfamily of alvarezsaurs, revealing a surprising arrangement of three ossified conical spikes around the thumb. These hand spikes were positioned pointing forwards, backwards, and inwards, and may have improved the ability to grip with just one functional finger.

“Spike-like” hand bones were also previously reported in 2009 in another parvicursorine, Ceratonykus, suggesting that these structures weren’t unique to Manipulonyx.

The paper describing Manipulonyx proposes that alvarezsaurs were ovivores, using their hands to carry and then break open eggs, but I’m personally very skeptical of this idea. I think the myrmecophagy interpretation for these little dinosaurs is still much more likely – they probably did opportunistically raid eggs when they could get them, like many modern predators do, but being specialized for just egg-eating is a big claim that definitely needs more evidence.

Duonychus

Duonychus tsogtbaatari was a therizinosaurid dinosaur living in what is now the Gobi Desert in southern Mongolia during the Late Cretaceous, around 96-90 million years ago.

Like other therizinosaurids it would have been a chunky-bodied herbivore with a small beaked head atop a long neck, long rake-like claws on its hands, stout legs, and a rather short tail. But it was rather small compared to most of its close relatives, estimated at about 3m long (~9’10”), with its known fossil remains including several vertebrae, partial ribs and pelvis, and a set of nearly-complete arms and hands.

Its hands had only two well-developed fingers, with a small splint-like vestigial third finger, an anatomical condition convergently seen in some other theropod groups but previously unknown in therizinosaurids. One of its long curved claws also preserved a rare example of a thick keratinous sheath, showing that in life the claw was over 40% longer than its bony core.

Duonychus’ elbow and finger joints had a fairly limited range of motion – more similar to the forearms of Tyrannosaurus than other therizinosaurids – but its claws were able to flex almost 90° at the tips of its fingers, which may have given it the ability to reach out and grab onto foliage with a very strong and precise grip.

Mexidracon

Mexidracon longimanus was an ornithomimid dinosaur that lived during the late Cretaceous, about 72 million years ago, in what is now northern Mexico.

It was a fairly small ornithomimid at around 2.5-3m long (~8-10′), and its leg proportions suggest it was less specialized for fast running than some of its other relatives. But its most unique feature was its hands, with extremely elongated metacarpal bones – giving it palms that were longer than its upper arm!

It’s unclear what the function of these unusual limbs was. Possibly they gave Mexidracon extra reach to hook its claws onto foliage and pull it within reach of its head, in a similar manner to ground sloths, chalicotheres, and therizinosaurs.