Tuesday, 12 May 2015

My Home, The Sauropod - Part I: Getting Filthy

The idea of an organism playing host to a multitude of other organisms is well known, and is something which most of us are familiar with - even if it's only through catching headlice at school or pushing a worming tablet down a cat's throat. On a smaller scale, there are gut bacteria, some of which perform an important role in keeping the digestive tract healthy. Others are less helpful, as those who frequent dodgy kebab shops will testify - if they're still alive. And it's not all restricted to Animalia, with trees being well-studied examples of a complex ecosystem centred around an individual.

It's not just about parasitism. Sharks, large fish, turtles and whales are often seen with a posse of remora, unusual fish with a sucker-like organ on top of the head, allowing them to hitch a ride. They take advantage of a steady food supply, in the form of particles of food dropped by the host animal, sloughed skin and faeces, but they also help keep the host healthy by consuming parasites which may attempt to adhere to its surface. In return, the host doesn't (always) eat them. On land, large mammals may be parasitised by blood-sucking invertebrates, but these, in turn, may be preyed upon by birds, which the larger mammals are big enough to bear the weight of - and the additional irritation. So, there's a constant battle being enacted on and in many animals, by other organisms, and often this affects the way these animals look and behave. A consideration of how parasites, symbiotes and associated organisms interacted in ancient settings may steer palaeoart in the direction of increased accuracy. It may also result in depictions which look rather different to what we're used to. After all, nature isn't always a tidy place.

Now, portraying these kinds of interactions probably drops this type of speculative palaeoart somewhere in the All Yesterdays camp. Of course, it's only 'speculative' with regard to how one might decide to show those interactions; they undoubtedly happened, but fossilised remains of those interactions are exceedingly rare. And not all of those interactions will be targeted encounters between a parasite or symbiote, and host, and this is what I have attempted to show in the following sketches.

Sauropods represent an interesting branch of Dinosauria, and include the largest terrestrial animals ever to walk the earth. The idea of these keystone species forming some sort of walking ecosystem is an attractive one, as they no doubt carried a contingent of parasites which may have attracted animals which predate those parasites. In addition, they may have provided a perch for flying reptiles and insects, and a surface for non-parasitic organisms to grow on. It's probably also not unreasonable to imagine some sauropods accumulating leaf litter and a twigs, especially if one restores certain species with a row of spines and other ornamentation, as some palaeontologists and artists do. It's hard to imagine sauropods successfully ridding themselves of all the material which rains down on them from the forest canopies under which they must have spent some time. That's not to say an apatosaur would never have dislodged accumulated forest junk from its back, but it would probably have found cleaning itself with any kind of precision difficult.

An apatosaurine sauropod, sketched up quickly and based on Scott Hartman's 'Apatosaurus' excelsus skeletal illustration. The dorsal spines form a trap for falling leaf and branch material, whilst the mosaic of scales and osteoderms provides a surface on which lichen fragments and diaspores adhere.  (Copyright © 2015 Gareth Monger)
That probably looks like a lot of twigs and branches, but these are long-lived animals which may have spent a long time in wooded environments. A smooth-backed sauropod probably won't accumulate twigs in any appreciable quantity, but you might expect to see a bit of lichen growth, especially on those surfaces which see little abrasion from rubbing against trees and other surfaces, or areas of skin which experience minimal flexing. A sauropod might look rather colourful - and different - if adorned with a collection of brightly-coloured lichens, dried on leaves, and small branches. And different populations of a single species might look different, depending on the differences in the vegetation of their respective home-ranges.

An apatosaurine sauropod, as viewed from above, wandering through a pine forest. Dead twigs and branches constantly rain down onto the forest floor, with some inevitably landing on passing sauropods. Reference photo: SV-POW! (Copyright © 2015 Gareth Monger)
For the fans of wild speculation, it might be fun to imagine that certain sauropods used a pile of vegetation in sexual displays, with those male sauropods carrying the largest pile of woody compost most likely to attract a female. Behaviour is one aspect of palaeoart which is wide open to ideas. You've only to look at extant animals' courtship displays to realise that from the future skeletal remains of, say, the bird of paradise, you'd never come close to guessing how they go about impressing a potential mate. There's every reason to think that some non-avian dinosaurs could have been at least as weird. And for palaeoartists, that's where a little imagination can prove useful.

Next up: some more thoughts on Yi qi...   ...and maybe something quick on Stegosaurus.


  1. So what you're suggesting is that some sauropods could be shrubopods.