Archive for February, 2019

The problem with floating pterosaurs

A few years ago I published a neat little paper with Don Henderson on the possible posture pterosaur might adopt in water. This was done to try and see if they might have issues if they became stranded on the surface and especially if the head was left at or even under the surface (you can read about this in some more detail here). However, what I want to talk about in this post is how badly and how often this simple paper seems to have been misinterpreted. I’ve been thinking about this for a while but Heinrich Mallison has just linked to an old post on his blog making the same general point about accuracy of citations. Like him, I’m sure I’m not blameless and we all make mistakes occasionally and cite the wrong paper or misattribute a source or get some details wrong. It happens and while obviously not ideal, such is life. However, some papers more than others seem to suffer from this and the floating pterosaur paper is one of them.

It is only a short paper, under 10 pages long and there’s lots of figures and references in that too and the subject itself is fairly simple so one would hope to minimise confusion. Unfortunately, this seems not to be the case and it’s already acquired a number of citations and comments that at best miss the point and at worst say the direct opposite of a point we made. Below are some direct quotes from papers and then points or quotes from the original paper to show how these are quite incorrect. I won’t directly name and shame the perpetrators as the point here is intended to be illustrative of the problem rather than go after colleagues when I can’t rule out having made the same mistake myself somewhere.

First off our study was apparently carried out in order to ‘imitate the swimming strokes of pterosaurs’. In the title and throughout the paper we refer to the floating posture and talk about static posture in water, not swimming per se. While in the discussion we did refer to the posture some pterosaurs took in water and pointed to how it matches putative swimming tracks, this was clearly not the aim of the paper. That makes this point a bit wide of the mark, but not bad and a rejig of the phrasing would clear this up.

Next up, we apparently show that ‘pterosaurs would not have been able to float without tipping over’. That’s clearly not correct as can be seen from the figures (see below). We do discuss the issue of tipping forwards in pterodactyloids in some postures, and the heads are indeed low, but that’s not the same as saying that all pterosaurs did this all the time and indeed the pterosaurs were generally stable.

Hypothesised floating postures fo various pterosaurs

Moving onto some greater issues, we apparently state that the ‘hairlike pycno-fibers covering their body would likely not trap a layer of air, as feathers of birds, and could become water-logged’. That’s very clearly not what we say at all as we make the very clear statement that ‘the effect of such a coat may have been positive (trapped air increasing buoyancy) or negative (waterlogged).’. Yes it may have been an issue, but we don’t know and are equally open to the possibility it could assist buoyancy and we point to the fur on aquatic mammals as a possible analogy, so this quote clearly is not in line with our position on what effect pycnofibers might have had.

We also are cited for the point that pterosaurs were ‘unable to take off from the surface’. This is not a point we really address (since it’s not directly related to floating posture’ but even in the abstract we say that pterosaurs ‘if immersed would need to take off again rapidly’ which clearly implies we are happy with the idea of water launched and later on we cite Habib and Cunningham and saying ‘A recent study suggests that even the biggest pterosaurs might be capable of taking off from the surface of the water’. In short we’re clearly happy with the idea they could take off from water and while we discuss the possibility that some pterosaurs might not have been able to, at no point do we say that they could not.

Then we have this very problematic statement that ‘simulations of the buoyancy of pterosaurs made using computers indicate that these reptiles had no ability to float well in water’. We clearly do not say this and point multiple times to the high pneumaticity of ptersoaurs any say things including ‘it is not surprising that the pterosaur model floats on water’ and ‘We show that in general pterosaurs adopted a position that was high on the waterline’ which make it very clear they floated and floated well.

These five statements are varying degrees of problematic, but given that this paper has only less than 20 citations from peer-reviewed papers (and several of them are by me which I don’t think I’ve miss-cited) that points to a pretty high percentage of erroneous citations on this one piece of work. When several of them are clearly flat wrong, and even information in the abstract points to them being in error it suggests that it’s really not been taken on board. Hopefully this paper is simply unlucky in keeping getting such erroneous takes but it’s a shame that a paper that I’m really quite proud of seems to be repeatedly cited for things it doesn’t say or imply. It’s probably only a matter of time before it is used to contend that pterosaurs could not swim (something the paper also clearly does not say) and I’ve seen our paper referenced in this context in popular writing so it may yet go that way in the literature.

In short, read papers properly and check what you are saying. It’s important.


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