Archive for March, 2023

Why I don’t like using modern animal patterns in palaeoart

I remember from some years ago a pub chat with John Conway about what makes ‘good’ palaeoart. We came to the conclusion that it was down to three main things, 1) is it good artistically – is there a nice composition, correct use of perspective, shading and general technique, 2) is it accurate in the sense that the anatomy, environment etc. is right (no Velociraptors vs Diplodocus) and 3) personal taste. In other words, people can produce technically brilliant and scientifically accurate material and you don’t have to like it if it’s not to your taste (though hopefully people would still appreciate it). The others of course remain somewhat subjective too depending on what the artist is actually going for (if you want it to be surrealist or a tribute to 19th Century art then accuracy may not be what you are aiming for – just like John’s own recent History of Painting book.).

This last point about ‘what you like’ is most relevant here because I want to talk about a common theme in palaeoart that I really don’t like and while I’ll try to rationalise and explain it, I do want to be clear that it is a personal preference and so doing this doesn’t really make you wrong and I don’t want to give that impression. So what is this thing I’m now going to moan about for several hundred words? It’s using really clear and obvious patterns and colours from modern animals and applying them to dinosaurs. (And yes, other things too but usually dinosaurs).

I don’t mean really common patterns or general ones like countershading, marine animals being blue or forest ones being dappled or stripes that go through the eyes or anything like that, I mean doing an oviraptorid with the colours of a parrot, or a sauropod with a giraffe pattern or a lammergier pattern on a dromaeosaur or puffin-beaks on pterosaurs or plenty of others. This approach has been around for a long, long time but it appears to be ever more common and increasingly present in high-profile art and projects. I have thought about this a fair bit and what I don’t like boils down to a few key points.

First off, it seems really unoriginal. If you are making palaeoart that is supposed to be as rigorous and scientifically accurate as possible then there’s a lot of creativity potentially taken out of what you can do, but there’s plenty of options and freedom in colours and patterns (while still being realistic) with the unknown. Taking that away that option from yourself and your audience seems a real waste and one I can’t understand. OK, I can’t draw for toffee, but isn’t making up the colours and designs of the animals one of the most fun and creative bits? Just copying another species seems such an incredible waste of an opportunity.

Next up, it’s very distracting. I’m sure there are all manner of weird and unusual animals out there with odd patterns that can be copied without it being obvious (though I still think it’s better avoided) but it certainly pulls me out of looking at the art in front of me and simply going ‘but that just looks like a weird golden pheasant / king vulture / gemsbok’ rather than considering the art itself. It actively does a disservice to the work by distracting you from it.

Perhaps more importantly, I think duplicating well-known colours and patterns is something that, accidentally or deliberately, conveys things about animal depicted because of our understanding and associations with those patterns. If you put a peacock’s colours on a maniraptoran theropod you are imbuing it with cultural or behavioural traits about how they display and their mating system, their habitats and so on that we generally don’t know at all (or are most unlikely to be similar). It’s making inferences that shouldn’t be there and that’s not a good way to communicate about long lost animals and surely that’s a major aim of most palaeoart? I think it often shows a lack of understanding about signals too – after all, something like an agamid might have a bight head and neck to best show off it’s colours, but transferring that to a ceratopsian doesn’t make a lot of sense when the back of the frill and the neck would not be the most obvious place for bright signal colours to appear when the front of the frill has evolved to be the main signal. It’s ignoring or misunderstanding how the signals likely work in both the living model and the extinct animals and again that’s not conveying good information.

There are for sure common patterns like the general white and grey of seabirds, or eye stripes and bright breasts in birds, or occasional striping on antelope that can be easily transferred to dinosaurs and pterosaurs and the like *because* they are either generic, or ecologically driven, or are non-descript (you can’t point to a bird with an eye stripe as being unique it’s so common in a way that you can a puffin bill or a macaw’s pattern) and so again, this isn’t any kind of ‘never’ instruction to copy living taxa. But I think it’s far, far more often a problem than it is a good thing and I can’t be the only one who thinks this, can I?

Actually I know I’m not, since I’ve had this conversation with a few colleagues (palaeoartists and academics and those who span the two) and I know I’m not alone, though I also don’t know how far this feeling runs. Again, I’m not saying this can’t or shouldn’t be done and there’s always a time and place to break the ‘rules’ for various reasons, but what appears to be an often default opinion of just taking one set of colours and patterns and transferring them to another is way too common. It is, to me, not only dull and unoriginal but actively misleading in a way and imbues ancient animals with symbolism and traits that they shouldn’t have while taking the audience out of the moment. So please do it less and think about why you do it when you do.

Display features in the fossil record

It’s been more than a while coming but here’s an actual normal blogpost for the blog that’s not just PR for one of my own papers or projects (don’t worry, more of that coming sooner or later). This one has been prompted by some repeated comments I’ve seen in recent months about the hypothesis of various features being used for display by academics discussing dinosaurs in particular, but other extinct animals too.

The argument basically runs ‘you say it’s for display only because you don’t know what it is’ and usually followed with ‘like when archaeologists say it’s for ceremonial purposes when they don’t know what it’s for’. I can’t speak for my fellow professionals studying human culture, but I can very much speak for the assessment of display features having written perhaps more on this than anyone else when it comes to dinosaurs and pterosaurs at least.

First off, yeah, some researchers are very much guilty of this. One recent paper did argue something was for ‘display’ and that was the last word on the subject. That is, there was no actual evidence or discussion of the implications and how it might function or have evolved or what it was a good signal etc. and that’s clearly suboptimal at best. And it’s hardly new, it’s a classic old argument for lots of things on dinosaurs that’s been about for a century at this point and so people arguing for display without data isn’t some recent phenomenon. However, for plenty of cases we either do have decent scientific evidence or it’s fairly trivial to make a reasonable argument and that comes from our understanding of sexual selection in particular and signaling structures in general. So here’s a breakdown of the kind of lines of evidence and reasoning that can support display as a function.

1. It has no clear mechanical function. Not every bit of anatomy is functional in presenting a positive advantage to an animal, and some can be optimised for multiple things, or are used only very occasionally, or, yes, can be cryptic and we don’t know what they are for. But in general, selection is very good at getting rid of things that are costly and not useful (see how quickly flightless birds reduce their wings for example) and things argued to be for display are often large and heavy and are unlikely to survive many round of selection.

2. Diversity of form between species. There’s a reason the claws, fingers, ulna, humeri, spine and even ribs of moles, golden moles, marsupial moles, pangolins, aardvarks, armadillos and anteaters look very similar and that’s convergent evolution based on strong selection for a clear mechanical function. Animals, especially closely related ones, doing the same things in the same ways will almost inevitably end up with very similar anatomy. There’s a reason the wings of birds all look similar (flight), but the variety seen in their tails or head wattles etc. (display) are so varied. There’s probably only one or two optimum mechanical shapes and repeatedly deviating from that, especially in close relatives is a display hallmark. There’s also a general suggestion (though I think untested) that these tend to evolve rapidly as well compared to more classic functional traits.

3. Diversity of form within species. Moose all look alike but their antlers can be very different to one another and there’s usually far more variability of display features between individuals than other anatomical features, and that’s before the possibility of things like dimorphism (though an absence of dimorphism is not an argument against a signalling function for various reasons).

4. Rapid growth late in ontogeny. Sexually selected and display structures grow when the animal is at, or close to, sexual maturity and are very small or non-existent before then. So if there’s any indications of the growth rate from having multiple animals at different ages or sizes this can really help.

5. Structures are costly. A related point to 1, but the idea of ‘honest’ signals means that these features should be expensive to grow or maintain and have some kind of disadvantage for bearing them. And that also means they tend to be big and obvious (though with various trade-offs often at play limiting size – things can’t grow forever).

6. Analogy. While few features are clearly analogous to those seen in living clades (though of course some like fossil deer have lots of living and well-studied relatives) it is possible to draw analogies for some. The elongate tail streamers of microraptorines and various Cretaceous birds are obviously similar to those of numerous extant birds which have been shown to be signaling structures, so it’s reasonable to infer that similarly shaped ones in related animals with similar ecologies and behaviours and doing similar things.

Not everything fits these moulds perfectly. Features can be multi-functional like elephant tusks where they are under sexual selection but also are used to fight off predators, strip bark from trees and other things and probably are under selection to optimise multiple activities. And of course functions can change over evolutionary history with, for example, horns potentially shifting from an initial display feature to an anti-predator function or combining the two. Thus what the original function of a feature may have been and what selection pressures drove it to its current condition are not necessarily the same thing (though I suspect often are).

Take something like pterosaur head crests which have repeatedly been suggested to have some kind of steering function. We’d expect there to be only one or two optimised versions of this given the complexities of flight and the extreme similarity of pterosaur wings to each other, but instead we see enormous varieties of crests, they vary between and within species and both grow in size and change shape during ontogeny and are apparently small or absent in young juveniles. Despite the suggestion that this has a mechanical advantage, it’s not clear how it would work and one might expect if head crests were so useful they would have appeared in birds and bats too at some point, and it’s not like pterosaurs are short of flight control surfaces. Plus of course, for such light and flying animals, these would have been heavy features and therefore presumably costly.

So it’s fairly easy to make a case for these as display features even if we can’t do a detailed analysis of their flight mechanics or look at the detailed ontogeny and variation of many (any?) species to the degree we would like. In short, yes, palaeontologists need to be much better at explaining how and why they are arguing for display as a feature and simply saying ‘it’s big and odd’ while kinda hinting at a couple of these points, really isn’t good enough. But on the other hand, a lot of the things argued to be display features (ankylosaur armour, ceratopsian frills, hadrosaur crests, tyrannosaur hornlets, spinosaur sails etc.) fit most or all of these categories and even if in-depth analyses aren’t possible, it’s certainly a reasonable starting hypothesis that they are there for display.

So the often knee-jerk response of ‘ugh, you just say it’s display without evidence’ belies a real lack of understanding of the ways we can make reasonable inferences about these features and the simple fact that big and weird structures almost by default will match these lines of evidence (when say a big tooth or long leg or extra toe will not) should not argue against these as a starting point for discussion. Display features are rampant in large tetrapods at least and it should be no surprise that highly vision-oriented animals like dinosaurs and pterosaurs would have gone down various display routes. Yes, we need better arguments and testing, but I’m more than confident that many of these features will ultimately be shown to have had display as a major part of their functionality.

@Dave_Hone on Twitter


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