Welcome Dearc, a giant rhamphorhynchine

Today sees the publication of a new and very cool British pterosaur – Dearc sgiathanach and as I got to see the paper a while back as a referee I thought I’d used that privileged advanced knowledge to write a post about it as it’s a really neat animal and British (and specifically Scottish) pterosaurs do not come around every day.

Photo of the skull and part of the body of Dearc, taken from Natalia Jagielska’s Twitter feed

First off, the basics on the name. It’s full name basically means ‘wing reptile from Skye’ and following s recent trend of using local languages for scientific names rather than Latin or ancient Greek, this is actually based on Gaelic. That’s really rather neat and I can’t think of any other Mesozoic animal so named in the UK and I hope it is not the last. Oh, and the authors (Natalia Jagielska and company) were also good enough to include a phonetic pronunciation in the paper (link below) as ‘jark ski-an-ach’ so hopefully people will be using that properly.

For a Middle Jurassic pterosaur, it has got a lot of good material and not only is it preserved in 3D (and there’s some great CT scan data of it) with most of the skull and wings, and a good amount of the vertebrae column etc. as well. You’d always want more of course, but it’s really a lot and in good condition too. The paper covers a lot of the anatomy in depth but I’m also sure there will be more to come on this in the future.

It’s clearly a non-monofenestratan pterosaur and actually one that is very close to Rhamphorhynchus, enough in fact to be found to be a member of the Rhamphorhynchinae in the phylogenetic analysis that they did. It actually comes out with the odd Chinese pterosaur Angustinaripterus which is known from a single large skull with exceptionally long teeth. In short, you’d expect this animal to be one of the larger and later version of these non-monofenestratans and a shoreline or even oceangoing predator of fish.

What’s really interesting about this animal is its size. The largest good specimen of any non-pterodactyloid pterosaur that we have is a really large Rhamphorhynchus that is held in the Natural History Museum in London and is right around 1.8 m in wingspan or perhaps is a touch more. That is already much larger than any other specimen (the next biggest is about 1.4 m) and while there are some odd large bones out there (like the Angustinaripterus skull) that has long been thought to be about as big as they get. On top of that, Rhamphorhynchus is from near the end of the Late Jurassic and so (anurognathids aside) is among the very last of the non-pterodactyloid pterosaurs. 

Although incomplete and impossible to measure or estimate perfectly accurately, Dearc is complete and robust enough to give it an estimate of over 2.5 m in wingspan. So that’s massively bigger than we have for even the largest Rhamphorhynchus (out of 150 specimens!) and being Middle Jurassic, it’s much older too. Add to that, it probably had more growing to do too.

So that pretty much blows out of the water two classic ideas about the size of non-pterodactyloids. They could get above 2 m in wingspan and indeed much bigger, and it didn’t take them till the very end of the Jurassic to even get up to 2 m in wingspan. That’s really quite an interesting shift in our perceptions of their evolution and in particular means they were getting into some biomechanical realms that we didn’t think they could achieve without a pterodactyloid bauplan. In short, this is a really cool find and it promises much more in the future for our understanding of the evolution and flight of these pterosaurs.

Jagielska, N., et al., 2022. An exquisite skeleton from the Middle Jurassic of Scotland illuminates an earlier origin of large pterosaurs. Current Biology.

4 Responses to “Welcome Dearc, a giant rhamphorhynchine”

  1. 1 Mike Taylor 22/02/2022 at 11:30 am

    “So that pretty much blows out of the water two classic ideas about the size of non-pterodactyloids. They could get above 2 m in wingspan and indeed much bigger, and it didn’t take them till the very end of the Jurassic to even get up to 2 m in wingspan.”

    I wonder what proportion of all our “taxon X did not evolve feature Y until time Z” are really just statements that we have yet to find an example of the thing we say didn’t exist.

    • 2 David Hone 22/02/2022 at 1:52 pm

      I’m sure there’s more than a few. But as with the Rhamporhynchus example, we’ve got a *lot* of them and plenty of other Jurassic pterosaurs and none close to this size so it’s a pretty big jump up after 250 years of pterosaur finds. So in this case I think we can justify the surprise.

  2. 3 daveunwin 22/02/2022 at 11:47 am

    Its great to see such a relatively complete specimen from the Middle Jurassic and it nicely complements the new darwinopteran also from Skye (https://www.biorxiv.org/content/10.1101/2022.02.14.480264v1). The size estimate of Dearc as having a 2.5 m wingspan is incorrect. There are multiple ways of estimating the wingspan of the new specimen and they all fall out at around 2.0m (indeed Jagielska et al. report some of these in their paper). Rhamphorhynchus is not an appropriate model as it is a relatively highly derived form with a relatively long forelimb and wing-finger. Jagielska et al. show, via phylogenetic analysis, that their new species is most closely related to Angustinaripterus and Sericipterus and direct comparison of the skulls and postcranial material of these taxa certainly seem to support this hypothesis. Sericipterus is sufficiently complete as to show that its proportions (and presumably those of Angustaripterini more generally) compare much more closely to those of typical non-monofenestratans than to Rhamphorhynchus. As an example, the humerus/wing-phalange one ratio in Sericipterus is 1.27 which is typical for basal pterosaurs (my best estimate for this ratio for Dearc, based on the published illustrations is 1.4-1.5). By contrast, in the largest examples of Rhamphorhynchus this ratio reaches between 2.5 and 3.0. Dearc is the same size as the bigger (isolated) bones in the Middle Jurassic assemblages from Oxfordshire and elsewhere. In reality few if any of these individuals reached wing-spans of over 2m. Jagielska et al. suggest that Dearc was still not full size. However, the fused scapulocoracoid, fusion of epiphyses including the extensor process on wing-phalange one, and the smooth, dense bone texture show that growth was all but over (the retention of some features of osteological immaturity is typical of mature pterosaurs – see for example Fabio Dalla Vecchia’s excellent 2018 analysis in Rivista Italiana di Paleontologia e Stratigrafia, 124. The significance of Dearc is that it will provide some very helpful and much needed insights into the many fragmentary remains of Middle Jurassic pterosaurs. Dearc itself fits very neatly into what we already know about the evolutionary history of Jurassic pterosaurs and interestingly hints at a distinct clade of Eurasian rhamphorhynchines in the Middle to earliest Late Jurassic.

  3. 4 Allen Hazen 27/02/2022 at 3:31 am

    RE: use of Gaelic in nomenclature.
    I guess this doesn’t quite qualify, but Borealestes cuillinensis (described 2021) has a specific name formed by adding the Latin ending -ensis to a Gaelic place name.
    (and the inclusion of a pronunciation hint in the Jagielska et al. paper was very helpful: I now remember from time spent in Ireland decades ago that it seemed like a good rule of thumb for an Anglophone attempting to guess the pronunciation of an Irish word from the spelling to assume that a consonant followed by an ‘h’ was probably silent, like the ‘th’ in ‘sgiathanach’, but rules of thumb are fallible.)

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