Fossil of Repenomamus attacking Psittacosaurus found

[Thialfi]

"In the fossil, Psittacosaurus is on its side, its skeleton curled in a semicircle. Tucked up against the dinosaur is a mammal called Repenomamus, which Mallon calls "maybe a badger-sized animal."

Repenomamus was among the largest mammals of its day. But it's only a third the size of Psittacosaurus.

Mallon points to the way that one of the mammal's paws is clutching the dino's lower jaw, while another grips a hind leg. "And the lower jaw of the mammal is biting onto some of the dinosaur's ribcage," he says."



https://www.npr.org/2023/07/18/1188275701/this-fossil-of-a-mammal-biting-a-dinosaur-captures-a-death-battles-final-moments

[Faelrin]

I think this is something that's been thought about before (or at least I'm sure I've seen something about Repenomamus potentially preying on Pstittacosaurus, if not other small dinosaurs, including babies, before), but to such have fossil evidence, and of this well preserved caliber is insane. By far one of the best finds this year, if not in general. Like this is honestly up there with the Fighting Dinosaurs and Dueling Dinosaurs, on how much of an important and well preserved find this, let alone yet another pair of animals that died in combat or the like together. The article suggests volcanic activity is why these were preserved like this, so I'm guessing something like a pyroclastic flow? But they are shockingly intact, still preserved in the midst of battle.

Edit: Turns out I was right in thinking there was stuff regarding Repenomammus hunting Psittacosaurus before, as checking out the wikipedia page for it shows a specimen that ate a juvenile Psittacosaurus. So the precedence was there all along, but just no evidence yet of this caliber.

Edit 2: Link to the paper itself (not paywalled thankfully): https://www.nature.com/articles/s41598-023-37545-8

[Bread]

If anyone is now wanting a model of this, it is available on shapeways https://www.shapeways.com/product/Y7TXTRN2M/early-cretaceous-stand-off?optionId=187963229

[edu]

It's so well preserved and so unusual that it looks fake. I am not saying it is, but it's shocking.

[ceratopsian]

Theropoda Blog has posted that he thinks the fossil is too good to be true and suspects it is a fake of two fossils glued together.  I guess the only thing to resolve such doubts is a CT scan or similar application of technology.  I don't have the technical palaeontological expertise to cast an opinion either way.

[edu]

In the paper they say that it can look fake, but the way the two fossils intertwine is too difficult to achieve, so they are inclined to consider it real. Time will tell.

[Faelrin]

@Bread Man was ahead of the game with those two. Just wish there was a painted version offered.

I didn't read the paper last night cause it was late when I shared it, but did it say anything about when/where the specimen was found, including supplement material? I'll take a look at it later today. Would be disappointed to find out this was a fake that was reported on. It being another fossil from China wouldn't help the already damaged reputation they have for fossil fakes (like Archaeoraptor, a chimaera of legit fossil material). It's also a shame as China does have some of best preserved fossils in the world, with things like Psittacosaurus, Sinosauropteryx, Yutyrannus, and many many others.

Like I know with Yutyrannus, I think it was in the supplement material that broke it down that the remains were still legit, even though they didn't know the exact location of where they were found.

[Libraraptor]

Honestly my first thought on this was "fake". It is too good to be true. Maybe the world has been needing a "couple" like this a little too desperately...
If it should turn out to be real, however, this find plays in the same league as the Velociraptor vs. Protoceratops fossil in my opinion.

[Jose S.M.]

I've read that I could also be that the mammal was scavenging on an already dead Psittacosaurus so it doesn't necessarily involved a confrontation.

[ceratopsian]

Indeed.  Theropoda Blog remained unconvinced by their discussion thereof.

In the paper they say that it can look fake, but the way the two fossils intertwine is too difficult to achieve, so they are inclined to consider it real. Time will tell.

[Lynx]

The only reason I'm questionable about this is how perfect the circumstances are and how well preserved it is

[Faelrin]

From the paper's introduction:

The new fossil (Weihai Ziguang Shi Yan School Museum WZSSM] specimen VF000011) was discovered on May 16, 2012 west of Lujiatun Village in Liaoning Province, near coordinates N41°36′24″, E120°54′40″ (Supplementary Fig. S1). It was acquired by the first author and donated to the WZSSM in 2020. The fossil originates from the Lujiatun Member of the Yixian Formation, the latter being 212 m thick locally. The Lujiatun Member is famous for its abundance of vertebrate fossils, especially the fossils of Psittacosaurus lujiatunensis, whose uncorrected relative abundance reaches nearly 90%, locally⁵. The sediments there are volcanically derived, and although depositional age estimates have varied^6,7, the latest U–Pb dating of tuffaceous zircons indicates an age between 125.755 ± 0.061 and 125.684 ± 0.060 Ma⁸.

Further down they claim:

The intimate and intertwined nature of the skeletons is remarkable, and suggests that this fossil association is authentic, not forged. Although fossil forgeries have been reported from the Jehol Group of China before, these typically involve the simple juxtaposition of two or more independent fossils^20,21, and do not replicate the tangled nature of the skeletons documented here. It might be argued that the broken and slightly displaced anterior ribs of the dinosaur indicate tampering, given the otherwise mostly intact nature of the skeletons. However, there has been postdepositional displacement of some other bones, including the lower jaw of the dinosaur (Supplementary Fig. S6B), and the distal manual and pedal phalanges (Fig. 1, Supplementary Fig. S9A,C) and distal tail vertebrae of the mammal (Fig. 1); similar displacement of the ribs is therefore possible, particularly if they had fractured prior to burial. To convince ourselves of the authenticity of the fossil, we prepared and exposed the left dentary of the mammal, which had not yet been revealed at the time of acquisition, and found that it, too, plunges into the matrix to clasp the dinosaur's ribs (Supplementary Fig. S10).

Later in the paper they mostly go on about if the Repenomammus was actively hunting it, versus scavenging, and other material, including geological information, age of the animals, and body size. The supplementary information #1 provided breaks down the geological material from the area. It also provides another image with a different view of the fossils. Supplementary information #2 is a zip file containing excel sheets, etc with some other data.

The geological material, location, etc they provided does suggest it might be a legit find. However, am I correct in thinking the fossils, after being discovered in 2012, presumably sat inside the first author's private collection before being donated to a museum of sorts in 2020? That is certainly problematic, if true, and I can certainly see why some would be skeptical when taking it into account, as the first author was the one who collected it, and we are relying on the information provided that they did not forge it, since they were claimed to be the one to have discovered it like this. Yet if this was ultimately forged, a fake, it would do irreparable harm to the first author, and all others that have helped review and publish the material within.

That said, I have also taken a look at the Theropoda Blog (with English translation on) post on this find, and there is a disclaimer that as he has not viewed the fossil, to take what he says with a grain of salt in a way, but I do think he raises some good points as well. For starters the fossil does not appear to show any instances of minor damages, and that even many other exceptional preserved fossils still have record of this in some way. He also goes on about the posture of the two fossils, and it was this exact thing I questioned yesterday in my initial post on this thread. Like we know from Pompeii, and other examples I think, that with humans at least, that when hit with a pyroclastic flow, their posture is distorted from the way the super heat cooks the flesh and organs. Wouldn't something of that nature distort animals that were either in such a fighting, if not scavenging posture? He also claims the fighting posture the two were reported to be found in unlikely and unnatural as well. It doesn't help there are only a few images of this find provided (in the paper and supplemental material). Something of this extraordinary nature should have had more images from more angles provided, to get a better look at what is going on.

Honestly after reviewing the information from the paper, and from the blog, I'm not quite sure what to think. This could be legit, based on the information provided within, but at the same time, some elements does lead one question if this was faked in some way. I hope more paleontologists can speak out about what they think on this reported find, and rather they think it is legit or not.

[ceratopsian]

I think it will take time to come for palaeontologists to assess the evidence and come to a scientific conclusion either way.

[Samrukia]

just a small observation from someone who has just minimal knowledge of paleontology : doesn't the way the Repenomamus holds lower jaw of Psittacosaurus suggest the latter didnt have cheeks?

[Halichoeres]

Well, regardless of the authenticity of the tableau, I think it ever-so-slightly increases the chance that someone will make a Repenomamus figure, which would be a positive outcome.

[stargatedalek]

just a small observation from someone who has just minimal knowledge of paleontology : doesn't the way the Repenomamus holds lower jaw of Psittacosaurus suggest the latter didnt have cheeks?

Not at all. If they were really fighting here, why did Psittacosaurus not crush that hand entirely? Clearly Psittacosaurus at least, if not both, were already dead before ending up like this.