Misidentified fossils – Turtle edition

My initial title for this blog was “Things that people thought were interesting fossils but turned out to be turtles”. Of course, I don’t mean that, I just have had a particularly frustrating few months reading the same undergraduate projects on turtle evolution, so they are not my favourite at the moment…. However… in the last few years, their bones seem to be popping up as being identified as other animals, which is something I found a bit amusing.

Mistaken identity 1 – the Flying turtle

The first time I became aware of this was something that I was actually involved in, and a case known to pterosaur workers as the “flying turtle”. Last year, a new pterosaur was named from the Maastrichtian Transylvanian Basin of Romania, where I’ve had the opportunity to work. This pterosaur was heralded as being an “out of place, out of time” pterosaur [1]. Described as ‘Thalassodromeus sebesensis’, from the Oarda de Jos locality, near the town of Sebes, this was the first Thalassodromeus specimen found outside Gondwana, the southern supercontinent present during the Mesozoic after Pangaea broke up. This was described in the paper as an extremely important find – not only did it massively increase the geographic distribution of this genus (the only other specimens are known from South America), but it also more than doubled the temporal range of the group, giving it an additional 42 million years, where no thalassodromine fossils had been found. The discovery of this genus in Romania was thought to suggest it was a forest-dwelling animal, and gave evidence for the endemic island fauna of the Hateg Island during the Late Cretaceous. The authors also made some extraordinary claims about muscle attachments and soft tissue crests that could have been used as a rudder in flight, an idea that has always been contentious (and generally not accepted) by pterosaur workers and aerodynamicists alike. Therefore, this creature was exceptionally interesting.

The problems began when looking at the fossil itself. Known from just one small, thin, sheet-like bone, ‘Thalassodromeus sebesensis‘ is not the most convincing pterosaur fossil. It was described as being part of the crest, yet no pictures are provided showing how it would have sat in the animal. Looking at the pictures, I still can’t see how this is supposed to be any type of crest, and I can’t quite put it on a pterosaur skull. When the paper came out, it was immediately scrutinised by pterosaur workers from around the world, me included. No one was convinced (even non-pterosaur workers were suspicious) by the pterosaurian identity of the specimen, let alone the extraordinary claims of the Laurasian Thalassodromeus that used it’s head as a rudder. What did we think it was? A turtle. To be exact – part of the plastron of Kallokibotion, a Maastrichtian turtle commonly found in Romania. And this was agreed on by a number of turtle workers as well, not just pterosaurologists (as Mark Witton would say). We published this response not long after the initial paper came out [2], which was swiftly responded to in turn. The initial authors still disagree with us, but I don’t know anyone else who thinks it’s a pterosaur, so that’s ok. If you want to read more about this story, you can check out Mark Witton’s blog post, which he wrote when our paper came out, as well as his follow-up on the response to our paper, which was quite controversial…

Above: plastron of Kallokibotion, with outline showing where the ‘Thalassodromeus sebesensis’ (Below) specimen would fit from Dyke et al. 2015.

Mistaken identity 2 – Giant raptors!

Ok to be fair, this one isn’t the entire specimen, just a little bit of it, and it doesn’t change the story really. At the end of last year, a new species of giant dromeosaur was described from the Hell Creek Formation of Montana – Dakotaraptor steini [3]. This find was significant as it was the first giant raptor from the Hell Creek Formation during the Late Cretaceous, and it had clear evidence of feather quill knobs on the ulna, the first direct evidence of feathers on the forelimbs of large dromaeosaurids. The existence of feathers on the forelimbs of a giant obviously not-flying dinosaur further supports the thought that feathers did not evolve specifically for flight, which some people have argued in the past. The new species was described from a partial associated skeleton and some additional material, including much of the forelimb, some hindlimb elements, some vertebrae, and the furculae, AKA the wishbones.

Now the difference with this find is that it was named from a significant amount of material, and most of it is just fine. However, it’s now been shown (just a few days ago by Victoria Arbour and colleagues) that the so-called “wishbones” of Dakotaraptor steini are actually part of the entoplastron of a trionychid turtle [4]. To be fair, looking at both papers, I can see how these could have been confused, especially since I don’t work with turtles. Fortunately, in this case the initial authors appear to accept their mistake in an article written by Ed Yong. This is science at it’s best! Science works better when we can admit our mistakes and move on.

Figure 1 from Arbour et al. 2015 showing where the entoplastron is found in trionychid turtles (A-D), and the “furculae” in question of Dakotaraptor (E-G).

Of course there are lots of examples of fossils being misidentified. It’s bound to happen when you’re dealing with often fragmentary or distorted material, but these two examples of turtles mistaken for some extinct reptiles within the same year stuck with me. I’ve been asking for other examples, and apparently some other things like T. rex and ankylosaur bones have been misidentified as turtles in the past (thanks Dean Lomax for sharing that), and even lungfish tooth plates were thought to be turtle shell (thanks to Graeme Lloyd for that), but I wasn’t able to find any information about any of those. The interesting thing is that those are examples of people thinking they were turtles because they had never seen anatomy like that (these are from before dinosaurs and lungfish were properly understood), while the recent examples are actually turtles that are described as something else. The important thing to remember is that this is not uncommon. It happens to lots of people. The best way to avoid this is to avoid describing particularly fragmentary or poorly preserved material, and to avoid naming things if you aren’t sure, as that is much less likely to be a big deal. But we are palaeontologists who like name things…

Anyone have any other examples of things that are actually turtles? Or other amusing fossil mixups you want to share?

EDIT:
Since the original post, I’ve had a few other examples pointed out to me. David Evans showed me an example of some turtle phalanges originally described as troodontid pedal phalanges from Mexico, which were the only troodontid fossils known from the Cerro del Pueblo Formation, leaving no known troodontid material from this formation (see Evans et al. 2014). I was also reminded of one of the big examples of dinosaurs being mistakenly identified as turtles – Therizinosaurus cheloniformis (thanks to Logan Orlowski for pointing it out in the comments below). This bizarre dinosaur is known for it’s large claws (almost 1m long), which were originally thought to belong to a turtle-like reptile. With only the arms known, it was thought that the claws would have been just for something like harvesting seaweed in the oceans. However, we now know this is a dinosaur, and the species name cheloniformis comes from this misinterpretation, meaning ‘turtle-formed’.

References:
1. Grellet-Tinner, G. and Codrea, V.A. 2015. Thalassodromeus sebesensis, an out of place and out of time Gondwana tapejarid pterosaur. Gondwana Research 27: 1673-1679.
2. Dyke, G. et al. 2015. Thalassodromeus sebesensis – a new name for an old turtle. Comment on “Thalassodromeus sebesensis, an out of place and out of time Gondwana tapejarid pterosaur”, Grellet-Tinner and Codrea (online July 2014 DOI 10.1016/j.gr.2014.06..002). Gondwana Research 27: 1680-1682.
3. DePalma, R.A., et al. 2015. The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation. Paleontological Contributions 14: 1-16.
4. Arbour, V.M., et al. 2015. The furculae of the dromeosaurid dinosaur Dakotaraptor steini are trionychid turtle entoplastra. PeerJ 4:e1691.