A work in progress: the pied stickler

It has been a while since I last posted something here. There were multiple reasons for that: the realisation that there are more than enough paintings for The Book lessened my enthusiasm to start new Furaha paintings. An interesting side effect of that is that I started painting a series of paintings completely unrelated to speculative biology, which was refreshing. So much so, in fact, that having finished three such paintings I became eager to do some more Furahan creatures.

Another factor is that the number of views and replies has been fairly low lately. Is a blog like this one too old-fashioned, or perhaps too complex? No longer interesting? Or is it too difficult to leave a reply? I thought so when I wanted to write something on someone else's blog. Ideas and thoughts are welcome.

 

Click to enlarge; copyright Gert van Dijk

Anyway, here is a detail of a work in progress showing a 'pied stickler' (Perfixor artifex). The name means 'cunning impaler'. A part of the accompanying text follows.

Katarzyna Altanero, who devoted her life to the study of hexapod carnivores, described sticklers as ‘prototypical gregarious piluferentic centauraptors’. This statement shows that doctissimus Altanero was one of those people who, once they have learned something, think that people are born with that knowledge already in place. But the cumbersome jargon is correct. 

'Centauraptors’
These animals are obviously hexapods, but they have freed their front legs from all locomotion duties, a principle known on Furaha as ‘centaurism’. Here, the limbs have become weapons.  
Centaurism probably involves very quick evolution. The front limbs, liberated from walking, were free to quickly evolve suitable shapes for their new roles. At the same time the balance and locomotion of the animal changed drastically. The front part of the trunk became shorter and was tilted upwards, while the former middle legs increased in size and moved forwards.  
   These changes must have evolved hand in hand with specialisation to a specific way of catching prey. For instance, predators relying on speed should not carry massive heavy clubs, and those aiming to bring down armoured prey must have adequate weaponry and need only be faster than their prey. Scavenging centauraptors can be slow , allowing some of the heaviest weaponry of all.   

‘Piluferentic’
Centauraptor weapons betray an interesting array of forms. Some are pure clubs, others function only as ‘pointy end’ weapons, and in yet others the limb has more than one purpose. The limb type known as ‘axes’ have a sharp edge on the underside, useful to hack open a carcass, but the same weapon usually has a heavy bulge too, allowing it to double as a club to knock prey off their feet or to bludgeon the prey's head, blinding it.
   The stickler’s weapons are no exception to this ‘Swiss army knife’ approach. While its weapon is primarily shaped like a club, the former foot has become a sharp protrusion that can be swung into action. This sting explains the word ‘piluferens’, meaning 'lance carrying’.   

‘Gregarious’
As the word suggests, sticklers live in groups. In this species’ case, tasks differ between group members, allowing a fairly complex society that must run on advanced cognitive capacity. Do not underestimate sticklers; one may appear to study you with open curiosity, but its pack members may well be behind you, on their way to encircle you. They cannot digest humans but that makes little difference to the human involved.       
           

Tabulae Mortuae V (Archives XV): Digital paintings die too...

 Every now and again I show an image from the Creature Vaults, those hidden domains where old sketches, failed paintings and discarded designs find their final resting place. 'Final', unless they are dragged out to be presented to the world, usually for the first time.

Click to enlarge; copyright Gert van Dijk

This image is one such, and it is the first to come from a vault without physical form. Other vaults consist of large cardboard folders, or of stacks of oil paintings carelessly stacked against the back wall of a closet. This vault is digital.

I started the conversion of the Furaha project from oil paintings to digital art some 11 years ago. The project, now nearly done, changes as time passes. The Great Hexapod Revolution had as a result that legs, heads and jaws or earlier hexapods no longer followed my self-imposed rules. The changes were too large to be solved with moderate cosmetic changes (I tried), so many paintings are now seeing a 'Mark II". In fact, some started as oil paintings (MkI), were later redone as digital paintings (MkII), and are now revisited to become MkIII. Mind you, most paintings these days are entirely new.

Click to enlarge; copyright Gert van Dijk

Here is some more detail of the head of this now defunct animal. It is a pity that I had to discard it, as I rather like the painting. But I kept the overall design and colour scheme for the MkIII version, which is nearly finished, and looks just as well or better, I think.

The animal is a 'thresher', with the Latin name 'Ira tarda'. That means 'slow anger', a name that was inspired by memories of an old teacher of mine. Threshers are solitary, grumpy and are best left to their own devices. They do have to meet from time to time, in view of the perpetuation of the species, but their behaviour at such times gives little indication of a mood upswing. Best not talk about it, really.

What does a Hexapod gallop sound like? (1)

Click to enlarge; copyright Gert van Dijk

 The image above represents one of the very first Furaha images ever, painted way back in the previous century. The planet did not even have a name yet, and I certainly had not thought much about biomechanics. I just tried to paint an interesting and pleasing picture. These primal hexapods were fairly insect-like, with a stiff-looking body. The details where the legs join the body suggest exoskeletal parts as much as they could represent skin flaps. I can show the painting here, as it will not feature in The Book: it doesn't fit anymore. 

But I still like the scene very much. In my minds' eye, I can see a large herd of these impressive animals ('handlebars' or 'handlebar-horns') enter the scene from the left, advancing towards the right, until they turn towards the camera, wheeling like cavalry. That scene deserves to be done again, with new and updated handlebars. The update does not only require revising their anatomy, as part of the Great Hexapod Revision, but their gait as well. After all, if you paint a fast-moving hexapod, you should have an idea how its legs should be positioned. Imagining six-legged walks is apparently not something that comes naturally to all illustrators: many, including brilliant artists, fell back on on four-legged locomotion patterns, and simply added additional pairs of identical hind legs until the required number of legs was reached (see here, here, here and here). I never liked that, even though I realise that doing otherwise asks a lot of an artist who may not be familiar with the gaits of insects and other invertebrates. 

Perhaps I am being too difficult about this; after all, the viewers are likely to accept the result anyway. When you looked at the handlebar painting, did you think 'I wonder whether that gait is correct?' My guess is you did not, but I still wanted to do better. I like to think that a fairly thorough biomechanical background is a selling point of Furahan fauna; I also do not think I could let it slip anyway... 

Click to enlarge; copyright Gert van Dijk

I therefore wrote a suite of programmes to help me design decent hexapod gaits. In fact, I wrote them again, as I had done so once before, in 'BBC Basic' on an Acorn Archimedes. There are still a few animations on the main Furaha website that survived the transition to other operating systems. The programmes did not. This time, I wanted to do better, meaning that the programme should find out how to fold a leg by itself, rather than requiring me to control each minute limb movement by hand. I thought that that would be tricky, and it was... I had to settle for limbs with three main segments, as I could not yet add a fourth one the position of which looked convincing enough. You will just have to imagine the feet. I will use the program as background material to design paintings, and I can add details myself. The programme does allow body position to adapt to the chosen gait, so that part works. 

 

Here is an example of such a three-segment limb. The programme uses segment length, built-in movement restrictions of the joints, and the phase of the movement cycle to control the thigh angle. The other bit of information is where the foot should end up on its motion path. Together, that is enough. The movement is a bit uneven, because the programme chooses from an array of possibilities, and I should have increased the number of possible solutions. 

 

This shows what happens when you vary the choice which joint should 'stick out' the most. The further a joint is from the vertical, the more energy is needed to keep it in that position. You can see here that making life easier for one joint makes it more difficult for another. The middle position looks like it provides a nice middle ground in that respect. In biology, an optimum usually represents a compromise that minimises the overall energy required. 

Click to enlarge; copyright Gert van Dijk

 

The basic hexapod anatomy these days consists of six fairly similar legs that all have 'zagzigzag' pattern, (see here , here and here), meaning the most proximal segment ('coxae' or thighs) generally point backwards. I chose that as I could not find a convincing argument to state whether zigzagzig or zagzigzag was better. The legs are not identical, though, and future hexapods will see more pronounced differences. In the pattern shown here, the middle pair of legs is stouter than the front and hind pairs, and their feet are placed wider apart. That latter bit of information is only visible if you look at the 'support diagram' under the beastie. Placing some feet wider apart is a trick to avoid leg collisions, although it is not strictly necessary: Earth tetrapods manage to avoid collisions just fine with similar distances between pairs of limbs. 

 

And here is one complete hexapod in a slow walk. The sounds were taken from sound recordings of horse hoof beats, because I had to use something; it doesn't mean the animal has hooves! Keen observers may well deduce some as yet undescribed anatomical information from the animation. 

So how about the gallop sound? Next post!

Are there dragons on Furaha?

 No, of course not!

Dragons are mythological beings, usually shown as very large scaly reptilian animals with four legs and two batlike wings. Did I mention that they breath fire and that some of them can talk? Of course, there are no such creatures on Furaha, but the human citizens of the planet did not shed their myths when they relocated to another planet, so they brought stories and depictions of dragons with them.

The citizen-scientists duly observed, with great interest, that six-legged beasties had taken to the skies and now had evolved into excellent flyers (‘not long’ should be taken literally: the animals flew around the spacers’ heads the moment they stepped out of their ship). Closer inspection revealed that some of these animals had four wings (and two legs) while others had two wings (with four legs). 

Click to enlarge; copyright Gert van Dijk

Later speculation suggested that both groups, the Quadrialata and the Dialata, had separately evolved from animals using membranes between all six legs to glide down from one tree to another. In one group, the middle pair of limbs had increased quickly in size, whereas the front and middle pair of limbs turned into wings in the other group.

While the scientists started studying mechanisms of lift and anatomical adaptations to flight, classifying everything meticulously, the general public took one glance at the four-legged two-winged avians and shouted ‘They’re DRAGONS!’. Now, scientists generally dislike lay people interfering with their subject matter, and protested that the animals were not dragons at all; they were ‘Dialata’, not dragons, and dragons did not exist anyway.

Of course, this resistance was futile, and the concept of ‘Furahan dragons’ was quickly assimilated by everyone except the scientists in question.                 

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So much for the ‘in universe’ version of dragon lore. What happened is that the ‘Great Hexapod Revolution’ is in full swing, and I am now working on flying hexapods. The good news, by the way, is that I now think that I only need to do about four of five new paintings to finish The Book. I am aiming at some 140 pages, so you will get your money’s worth (if I find a publisher, that is).  

The unfeathered bird by Katrina van Grouw

 

I am working on my first painting of a Dialate flyer. I took the revamped general hexapod body scheme and thought about how it would need to be modified to become a successful flyer (also see here). Beautiful examples of such anatomical adaptations can be found in the book ‘The unfeathered bird’ by Katrina van Grouw. The image above was taken from that book, and shows the extent of anatomical  modifications.

The elongated hexapod body would have to go, to keep the mass centred. That meant that the frame of the animal had to be shortened, with the hind and front legs bending down towards the middle of the animal. These walking legs also became small and slender, whereas the wings, the middle limbs, increased in mass. The wing skeleton resembles the ‘bat mode’ more than the ‘bird model’, as it has  intact ‘finger’ bones. Of course the toe/finger pattern is not as nicely radial as in Earth’s vertebrates, but flows a Devonian branching pattern instead. The wings themselves are only partly membranous, so they do not really resemble bat wings that much.  

 

Click to enlarge; copyright Gert van Dijk

Here is a simple model done with Zbrush. People can achieve amazing results with Zbrush, but I am definitely not one of them (and I am not alone in disliking its complex convoluted completely counter-intuitive interface). The body and walking legs are sculpted and show the by now general zag-zig-zag basic hexapod pattern.  The wings are only shown as a sort of scaffolding (‘Zspheres’). Their Devonian branching is obvious. 

Click to enlarge; copyright Gert van Dijk

Here I have given up on making the sculpt follow the scaffolding, so you only see the scaffolding. The scaffolding is NOT the animal’s skeleton, but just a shape placeholder (the bumps on the body just indicate its size). Notice how the walking legs are tucked away against the body. 

Click to enlarge; copyright Gert van Dijk

And here is the same animal (Draco umbraferens), clinging on to a reed or stem, looking down to see if here is anything in the water it might eat. It unfolded one wing to provide shade, either to lure animals to the shade, to see better underwater, or both.

I liked that pose, so I developed it further. I am not going to show the painting, which isn’t finished yet anyway, but thought you might wish to see part of it. The Draco will be sitting on a reed in a marsh in bright sunshine. I used Vue Infinite as I often do to compose the scene to help with lighting and perspective, but only roughly. 

Click to enlarge; copyright Gert van Dijk

The scene provided a challenge, as it deals with reflections, transparency and shadows. The image above shows a detail of the future painting: a background plant. Panel A shows the shadow the plant casts on the marsh bottom; B shows the part of the plant that is underwater; C shows the shadow the above-water parts of the plant casts on the water surface; D shows the part of the plant that is above water, and E shows the reflections of that part on the water surface. Finally, panel F shown all parts together, with transparency adjusted to provide a realistic image; or I hope so anyway. The Draco and the reed it sits on will be constructed similarly.

That's it; the next post will probably be about hexapod gaits, and will include the sounds of some gaits, including a hexapodal gallop…      

The great hexapod revolution and Furahan Fishes' evolution

 In the past I had remarked that I was trying to solve two evolutionary puzzles concerning hexapods, the last major animal group needed to finish The Book. Well, those puzzles were solved, so I am now busy with the Great Hexapod Revolution.  I worked on the puzzles off and on, and realised that there should really at least be a sprinkling of plants, small insect-like creatures and mixomorphs. These expanded The Book from 100 to 130 pages. I guess that number means I can safely lower the number the hexapod paintings to keep the book manageable.        

The 'revolution' means that there will be changes to the anatomy of just about every hexapod I ever painted. I will therefore revisit some old paintings and give them a makeover. The process also deciding which characteristics should be included and which had to go. Once I had a list of useful characteristics for terrestrial hexapods, the next problems was of course how they actually evolved.

That meant I went back to the drawing board for Furahan 'Fishes'. (I know that 'fish' can be singular as well as plural, but the English language also had 'fishes', in particular when multiple species are meant,  and Furahan biologists used the term in that meaning. Blame them, not me. )

Anyway, for those who are not up to date with Furahan cladistics, there are six groups of Furahan 'Fishes', numbered I to VI, for which example species had already been painted. The anatomy of Fishes I to III needed a bit of tweaking, and I did not like the paintings much anymore.

Click to enlarge; copyright Gert van Dijk

This was the previous, now discarded, image showing Fishes I. The shape is well visible, and the major Fishes I characteristics are there for all to see: two lateral membranes, no jaws, four eyes, and some respiratory openings along the bottom. As an illustration of these traits, it works. But it looked too schematic and a bit boring: a living animal will have peculiarities common to its species or even to it being an individual, and those were completely absent.

 

Click to enlarge; copyright Gert van Dijk

So here is the new picture showing Fishes I: there is a background to make the image more appealing, and the animal has more individuality, I think. I leafed through my cephalopod books and was inspired by iridescence and partial transparency of some species. I wondered whether I could pull that off, and think I succeeded reasonably well. Close observers will see that there are now openings on the back of the animal too; well, that is because Fishes I now come with four respiratory canals. It's part of the revolution...

I have never shown much in the way of evolutionary trees, and the ones I did were not meant to be included in the book. However, I thought that I should perhaps include one or two cladograms in The Book, so I made a table showing characteristics of the six groups of Fishes to help with a cladogram of Fishes I to VI.  

Click to enlarge; copyright Gert van Dijk

 
Here it is. It has the 'diagonal form' you often see in biology books. When I first encountered cladograms, this diagonal representation really confused me. If you start at the bottom, you reach most species by making some sharp turns, but there is one route up that involved just one straight line. Perhaps it was my strong preference for visual matters, but the relation between the two species connected by that straight unbroken line seemed much stronger than any route that involved zigzagging. But that is not true at all: the fact that there is a split (a 'node') is meaningful, not at which angle the lines depart from the node. It turns out I was not the only one who tended to interpret such diagrams the wrong way: students learning biology have more trouble with diagonal than with 'bracket' diagrams. Well, stop making diagonal cladograms!

 

Click to enlarge: from TR Gregory, Evo Edu Outreach 2008; I: 121-137

That point is well made in the diagram above. The source is free and very readable. If anyone else also has trouble with cladograms, dendograms or phylogenetic trees, including remembering the differences between them, I recommend this paper: it lists the 10 most common misperceptions of such trees. It is very clear. But I cannot help thinking that if there are no less than 10 common misperceptions, there are probably even more uncommon misperceptions, and then I start wondering if there is no easier way to teach evolutionary relationships.

 

Click to enlarge; copyright Gert van Dijk

So here is a very similar tree but now every line running up to a node is vertical before it reaches that node, and the two resulting descendant lineages depart from the node in a symmetrical way. It is much more intuitive, I think!

Some of you will have noted that, according to the cladogram, Fishes IV and VI have a more recent common ancestor than either does with Fishes V. In other words, Fishes IV and VI are closer related than IV is with V or V is with with VI. Oh dear! Shall I keep that in, and blame it on a mistake of early Furahan Biologists? Or I could just exchange the labels 'V' and 'IV'? Or I could go back to names I came up when I thought I might still need not just names for the Species and Genus, But also for the Familia, Ordo, Classis and Regnum (the Latin names of the groups of the old Linnaean system): Fishes I would revert to Clavifluitati, II to Gnatha, and III to Penpinnata. I will think of something.

Anyway, onwards with the Great Hexapod Revolution!  

The evolutionary origin of dragon flight

Perhaps some of you know the ‘dragon’ series of books by Marie Brennan. They are very enjoyable fantasy novels, describing the consecutive adventures of a woman in a fictional world resembling late 19-century Earth quite a bit. There are of course disparities, such as the existence of dragons. 

The protagonist is a young woman, or she is at the start of the first book; in later volumes she is older. She wishes to study Natural History, not at all a proper endeavour for a young woman in her rather Victorian world. To find out more about her and her adventures, you should read the books for yourself, because this post mostly deals with the cover art of one the books: 'Within the sanctuary of wings'. 

You can have a look at all the covers on the site of the artist, Todd Lockwood, where you can also buy prints and have a better look at the covers. 

 

Click to enlarge; copyright Todd Lockwood

Here is the cover in question. I think you can guess why it caught my interest, well, other than this being creative and high-quality art. The four creatures form an obvious succession, starting with a six-legged dog-lizard wingless beastie in front. The distance between its hind and middle legs is larger than between the middle and front legs, which is interesting, but the really important detail is the little membrane connecting the hind part of the middle leg to the torso. 

In the next stage, that membrane is a lot larger, and that second 'protodraco' seems to be gliding as much as it is running. The middle legs stick out sideways a bit; do they even hit the ground? The third stage has undeniable wings, and the fourth stage is all about wings. That one is a proper dragon, with four walking legs and two wings. I think this cover is a diagram of the evolutionary history of flight in dragons. 

The covers of all these books betray an obvious biological interest, which is completely in keeping with the content of the books: the heroine builds her career on the scientific study of dragons, and the readers get to hear interesting snippets here and there. When I saw the cover, I was curious whether this apparent evolutionary history also featured on the books, but I did not find that there. 

Would this progression from a running hexapod with six walking legs to a clade with four walking legs and two wings work? Regular readers will know that Furahan hexapods gave rise to flying forms as well, so I had to devise an evolutionary background for them, just as had been done for these dragons. Actually, hexapods did not only gave rise to the four-winged tetrapterates, but also to two-winged bipterates. On paper there is even a third flying clade, but I haven't worked much on that one yet. 

A basic concept in evolution is that an organ or feature will not develop just because some future descendent, a few million times removed, may make good use of whatever the organ does. That structure must convey some advantage in its early stage, or why would it be there? That advantage is unlikely to be true flight. But the future wing could help in gliding down from a tree or a cliff, or it could help the animal to jump higher and longer, or to run better. If you read about the evolution of flight in pterosaurs, birds and bats, you will find such explanations. I think that the winglets in the 'protodracones' on the cover show that, in dragons, flight evolved 'from the ground up', starting with more efficient running. 

Click to enlarge; copyright Gert van Dijk

At present, that is not how Furahan tetrapterates or bipterates got into the air. They took the 'down towards the ground' route. The rough sketch above was my first try at finding a shape for such animals. This is an arboreal species with folding leg flaps on all six of its legs. They crawl up into trees and then jump out of them and glide away, somewhat clumsily. 

Once the evolution of such gliders is jump-started (sorry for that one), the next stage is likely to involve optimization. The animals will probably not be very good at flying in the beginning, so it may pay for them to have an aerodynamically stable body plan. A stable flight scheme would make them less maneuverable, but at least it should keep them airborne without sophisticated neural control. The easiest way to achieve a stable shape would be to have the centre of lift directly above the centre of gravity, and in turn the easiest way to get there is probably to use the middle limbs as the main or only wings. 

There are intriguing other possibilities though, because the hexapod Bauplan in principle allows  not just one, but two or even all three pairs of limbs to be used for flight. With less than three pairs the next question is which pairs of limbs should be used for that? Any such design must also look into how the remaining legs must be adapted, so the animal will make aerodynamic sense while also being able to move about on the ground. 

Such things might be good material for another post, but I would not be surprised if readers run away with these and better ideas long before I will ever get around to writing that post.