Dinosaur Wrists

[E.D.G.E. (PainterRex)]

So, we have been told that dinosaurs were clappers, not slappers. But why did people think they held their wrists in bunny position at all? We still see museum-level reconstructions with broken wrists, yet you'd think the scientists themselves would know that they held their arms locked in a specific position.

Can anyone explain it for me? or point me in a direction in which is has been answered already, thank you.

[Takama]

While i cant answer the qustion as to why people keep makeing them like slappers. I think the reason Museums do not correct ther amounts is because it cost Money to do so.

Someone correct me if im wrong

[tyrantqueen]

If we knew from the start that birds and dinosaurs were close relatives, maybe we wouldn't have given them broken wrists. The earliest Victorian reconstructions probably used lizards as reference (animals which can pronate their hands) and maybe mammals too.

[E.D.G.E. (PainterRex)]

I am aware of that part, but it is odd that museums make new mounts and still get that part of the anatomy incorrect, though I have been seeing that occur in museums from other countries, not sure how that would have anything to do with that though.

[Minmiminime]

It's probably one of these odd choices that was built on presumption before anyone bothered to actually examine the whole specimen, like Louis Dollo deliberately breaking the tail of his Iguanodon to make a point. It was reconstructed thus in museums thereafter, until Ostrom instigated a shift in thinking in the 60's following the discovery of Deinonychus, and this started a re-examination of everything we'd previously taken for granted (very basically)

It's an odd one, but it's not unprecedented for downright wrong interpretations to persist contrary to actual proofs. It's like the whole field seemed to fall out of fashion and was not taken seriously for about 50 years, and all the Victorian era enthusiasm and excitement and ideas fell by the wayside; after all, Huxley compared them to birds in the very early days, and Dollo reconstructed Iguanodon upright to emphasise that it was not a lizard. Charles Knight did a fabulous reconstruction of leaping Lealaps, but otherwise, sluggish reconstructions persisted despite all the evidence to the contrary.

And Jurassic Park, arguably hugely influential in restarting serious research, went to the lengths of Dr Grant describing the half-moon shaped wrist bone "just like a bird", then still proceeded to reconstruct its 'raptors with bunny hands

Basically, cultural norms in biological sciences are often form based only on assumptions, it takes a lot of time for cultural norms to be questioned, then even longer for them to be changed, even when they're totally wrong, and experts aren't immune to this either. A recent example is the furore over dinosaurian relationships, which have always been presumed to be related to their hip configuration, and this may be a red herring.

It's certainly an exciting time to be interested in the field..! But it is annoying that even people who should know better are producing lazy reconstructions, when there's both proof (itself rare in palaeontology) and a wealth of supporting information out there, and it's now reasonably common knowledge among amateurs!

[E.D.G.E. (PainterRex)]

It's probably one of these odd choices that was built on presumption before anyone bothered to actually examine the whole specimen, like Louis Dollo deliberately breaking the tail of his Iguanodon to make a point. It was reconstructed thus in museums thereafter, until Ostrom instigated a shift in thinking in the 60's following the discovery of Deinonychus, and this started a re-examination of everything we'd previously taken for granted (very basically)

It's an odd one, but it's not unprecedented for downright wrong interpretations to persist contrary to actual proofs. It's like the whole field seemed to fall out of fashion and was not taken seriously for about 50 years, and all the Victorian era enthusiasm and excitement and ideas fell by the wayside; after all, Huxley compared them to birds in the very early days, and Dollo reconstructed Iguanodon upright to emphasise that it was not a lizard. Charles Knight did a fabulous reconstruction of leaping Lealaps, but otherwise, sluggish reconstructions persisted despite all the evidence to the contrary.

And Jurassic Park, arguably hugely influential in restarting serious research, went to the lengths of Dr Grant describing the half-moon shaped wrist bone "just like a bird", then still proceeded to reconstruct its 'raptors with bunny hands

Basically, cultural norms in biological sciences are often form based only on assumptions, it takes a lot of time for cultural norms to be questioned, then even longer for them to be changed, even when they're totally wrong, and experts aren't immune to this either. A recent example is the furore over dinosaurian relationships, which have always been presumed to be related to their hip configuration, and this may be a red herring.

It's certainly an exciting time to be interested in the field..! But it is annoying that even people who should know better are producing lazy reconstructions, when there's both proof (itself rare in palaeontology) and a wealth of supporting information out there, and it's now reasonably common knowledge among amateurs!

Thank you for the reply! Are there any sources out there that explain how/why the wrists were the way they were? I have yet to find something quite like a proper explanation.

[Papi-Anon]

Piggybacking off this topic, I'm curious about manual dexterity of non-avian theropods. I know there's been depictions of dromeosaurs with 'mitten hands' (even David Peters drew a few of them in the 90s), but what of other theropods outside of the dromeosaurs? What sort of grasping capabilities did they have? I'm especially interests in Allosaurs with their hands having the larger yet stout 'thumbs' with the middle and outer fingers each with more joints. I don't think Allosaurs had opposable thumbs by any means, but just how well could their hands function for grasping or even manipulating things?

[amargasaurus cazaui]

It's probably one of these odd choices that was built on presumption before anyone bothered to actually examine the whole specimen, like Louis Dollo deliberately breaking the tail of his Iguanodon to make a point. It was reconstructed thus in museums thereafter, until Ostrom instigated a shift in thinking in the 60's following the discovery of Deinonychus, and this started a re-examination of everything we'd previously taken for granted (very basically)

It's an odd one, but it's not unprecedented for downright wrong interpretations to persist contrary to actual proofs. It's like the whole field seemed to fall out of fashion and was not taken seriously for about 50 years, and all the Victorian era enthusiasm and excitement and ideas fell by the wayside; after all, Huxley compared them to birds in the very early days, and Dollo reconstructed Iguanodon upright to emphasise that it was not a lizard. Charles Knight did a fabulous reconstruction of leaping Lealaps, but otherwise, sluggish reconstructions persisted despite all the evidence to the contrary.

And Jurassic Park, arguably hugely influential in restarting serious research, went to the lengths of Dr Grant describing the half-moon shaped wrist bone "just like a bird", then still proceeded to reconstruct its 'raptors with bunny hands

Basically, cultural norms in biological sciences are often form based only on assumptions, it takes a lot of time for cultural norms to be questioned, then even longer for them to be changed, even when they're totally wrong, and experts aren't immune to this either. A recent example is the furore over dinosaurian relationships, which have always been presumed to be related to their hip configuration, and this may be a red herring.

It's certainly an exciting time to be interested in the field..! But it is annoying that even people who should know better are producing lazy reconstructions, when there's both proof (itself rare in palaeontology) and a wealth of supporting information out there, and it's now reasonably common knowledge among amateurs!

Thank you for the reply! Are there any sources out there that explain how/why the wrists were the way they were? I have yet to find something quite like a proper explanation.

Dinosaurs did not have the highly evolved elbow and wrist joints we do, which allow the radius to cross back and forth as the arm is rotated...their arms bones were basically stacked and held the wrists, and with them the hands in the neutral to semi supinated position in most cases. There were exceptions..for instance hadrosaur arms seem to naturally form a twisted orientation which held their hands in place, regardless of the arm bones, and this has been noticed in some specimens of psittacosaur as well.

[Dinoguy2]

Piggybacking off this topic, I'm curious about manual dexterity of non-avian theropods. I know there's been depictions of dromeosaurs with 'mitten hands' (even David Peters drew a few of them in the 90s), but what of other theropods outside of the dromeosaurs? What sort of grasping capabilities did they have? I'm especially interests in Allosaurs with their hands having the larger yet stout 'thumbs' with the middle and outer fingers each with more joints. I don't think Allosaurs had opposable thumbs by any means, but just how well could their hands function for grasping or even manipulating things?

A recent study on theropod soft tissue found direct evidence of "mitten hands" in Anchiornis, and by correlating finger shape and arrangement, concluded they were present in oviraptorosaurs too (specifically Anzu). Whether or not they might have been present outside Pennaraptora, or are correlated with "wings", I think is an open question, but I guess if the same bony correlates found in Anzu were found in say Allosaurus the authors would have mentioned it.

Mitten hands would severely limit grasping ability though not necessarily opposability of the alular digit. I think it's generally accepted they'd be used more like hooks, as in baby hoatzin.

[WarrenJB]

Piggybacking off this topic, I'm curious about manual dexterity of non-avian theropods. I know there's been depictions of dromeosaurs with 'mitten hands' (even David Peters drew a few of them in the 90s), but what of other theropods outside of the dromeosaurs? What sort of grasping capabilities did they have? I'm especially interests in Allosaurs with their hands having the larger yet stout 'thumbs' with the middle and outer fingers each with more joints. I don't think Allosaurs had opposable thumbs by any means, but just how well could their hands function for grasping or even manipulating things?

Predatory Dinosaurs of the World, page 110:

Palaeodinosaur and theropod fingers were supple so they could flex far back and grasp tightly. The most interesting finger was the thumb. It was the stoutest, and had a base joint that twisted inward. As Figure 4-12 shows, this forced the thumb to turn inward and away from the other digits as it extended forward from the palm.¹⁸

The references at 18 are Bakker, 1986; Bakker and Galton 1974; Paul 1987a.

Figure 4-12 on page 109, and figure 9-7 on page 220, show the skeletal hands of Coelophysis, Allosaurus, Velociraptor and Archaeopteryx held in a neutral pose, with the claws on the three fingers shown fairly parallel. With the fingers extended, Coelophysis' thumb twists sideways a little, but Allosaurus' thumb seems to rotate at least 30°, with the 'edge plane' (dorsoventral?) of the thumb claw almost perpendicular to the other two claws. Velociraptor and Archaeopteryx' thumb claws rotate even further. The effect is somewhere between a deinonychosaur's hyperextended toe claw, and an iguanodont's thumb claw, and GSP's emphasis is on the big claw's use as a weapon.

But a picture paints a thousand words.

I thought I had seen something about Allosaurus' thumb claw converging with the others as the fingers flexed, which seems logical considering the outward twist of extension, but I can't find it just now. I might be misremembering that PDW piece, but I don't think so.

I've no idea how thinking on this has changed, if at all, since 1988. It needs a further search.

[UtahraptorFan]

Just outside of the bookstore at Western Wyoming Comm. College in Rock Springs, there's a Camptosaurus mount with its right hand in a palm-out position. I don't have an answer to the OP's question about why some places still do it. It can be frustrating to see such out-of-date mounts.

[Papi-Anon]

Sorry if this is considered necro-posting ('paleo-posting'?), but I have another theropod limb articulation question:

What sort of articulation did dromeosaur legs have as a whole? I'd read that dinosaur ankles were only hinged and couldn't rotate, is that even true?