What does it take to make a reindeer fly?

This blog is about 'Furahan Biology and Allied Matters', and today we will stretch the 'allied matters' a bit, to produce this special Christmas post. Somewhere in Speculative Biology there must be a place to think about re-engineering mythological life forms, which is what this post is about.

The starting condition is simple. Thanks to globalisation, a most unusual subspecies of reindeer (Rangifer tarandus) has spread widely from its original area, so it can now be observed in skies over many parts of the world. In the skies? Yes, because these reindeer fly.       

It is not clear whether these reindeer can fly in their natural state, as they are only observed to do so when tethered to sleighs. This is slightly worrying, but even so, the force that keeps them in the air must be magic, as the reindeer lack any observable physical means to provide lift. While magic is a potent force in the imagination, in the real world it is noticeably difficult to acquire, so we need a more pragmatic approach. 

What would it take to make a reindeer fly in the real world? And I mean 'fly', not hurtling it through the air by strapping a jetpack to its back or using a large catapult. No, it must fly though biological means. The first problem is that reindeer have no wings, so we will have to use advanced creative bioengineering and splice in some wings. Done! That was quick...

Reindeer weigh around 100 kg, if we average estimates of male and female weight. But even these brand-new wings won’t make a 100-kg reindeer fly. And don't you start objecting that some pterosaurs weighed more than 100 kg and could still fly. We could in fact probably re-engineer the flying reindeer to achieve pterosaur-like mass, but the result would definitely look a lot like a pterosaur, and it should look like a reindeer, right?
 
Where was I? Oh yes, the 100 kg mass is a problem. Why? Well, take a 0.6 kg pigeon with a 70 cm wingspan. If you double its length, width and height, you get a wingspan of 140 cm and it will weigh 8 times the original weight. That factor 8 represents doubling of all three of length, width and height, so it is doubling to the third power (2 to the power of 3). By the way, for more on basic scaling of animals, see these posts here and here.

The problem is that lift is proportional to wing area, and area is proportional to the square of length. Doubling the pigeon's size makes the wing area four times larger, but that four times larger wing must carry eight times the weight. That won’t fly. (Sorry for that one.) We can make the wings extra large to compensate for the larger weight, but that will also increase weight. As explained in another post, at some point of increasing body size the wings can no longer carry the body.  

The obvious solution is to shrink the reindeer until it weighs as much as something that can fly. Say a rather massive goose at about 5 kg. Some calculations reveal that the reindeer's length should then be 25-30% of the original length of 180 cm.

To allow room for massive wing muscles, everything else must be reduced in weight: to decrease gut size it needs a new diet, mostly sugar; we can then also abolish the teeth, because it doesn't need them and won't get caries. We'll give it slender legs, tiny light hooves and fluffy hair. You will probably insist on antlers, so antlers can stay, but they will be much reduced. We can splice some red bioluminescence into its nose, to put the cherry on the cake.    

Done! A realistic flying reindeer! 

Click to enlarge; copyright Gert van Dijk & Roelien Bastiaanse

 

Happy holidays!

The aliens of the TV-series ‘Invasion’ (also: ‘Inversion Fish II’)

All episodes of the first season of the TV series ‘Invasion’, from Apple, are now available for viewing. If you are still planning to see the series later, stop reading now, because there are spoilers ahead.

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The series shows an alien invasion of Earth from the viewpoint of a few individual people, here and there on the globe. The protagonists at first seem to be people randomly caught up in the events, but some later wind up playing more important parts. I wouldn’t be surprised if all of the remaining apparent bystanders will end up being close to the centre of things, but that will have to wait for future series (a second series has been ordered).   

In the early episodes no-one has a clue what is going on, an that includes the protagonists as well as the viewers. That uncertain state lasts quite a while, because the series is no hurry at all to speed up the story or to explain where it is going. This may be a reason why the ratings haven’t been very high. Personally, I do not mind that the story unfolds slowly. This ‘strategy of keeping the viewer in the dark also means that the makers do not explain much, and so did not have to insert the kind of technobabble that is often used in science fiction series to explain alien technology or biology. In fact, there was almost no explanation of how anything works, which was fine with me. 

There was one instance of an irritating wilful neglect of knowledge in the series: a child lies shaking in an apparent MRI machine with an EEG cap on, resulting in an apparent MRI image with overlaids spots of colour, prompting a passing neurologist to say that the EEG was flat. That's not how MRIs or EEGs work; I guess that a real EEG wasn’t considered impressive enough.  

Anyway, it takes quite a while before you see the actual aliens. When you finally do, they are just dark blobs from which spikes shoot out towards a nearby floor, wall or ceiling. You typically do not see them moving in great detail, but it is clear at one point that they more or less ‘invert’ themselves. That is not easy to explain in words, so it is good that the producers posted a short video on YouTube about how they designed the aliens. 

Here it is. The commentary at one point includes the following: ‘A biological entity that we cannot even begin to understand’. Well, I am not going to take that at face value... 

In science, it is always time begin doing just that. Of course, here we do not have have to deal with real alien biology, but just with a human design, and what one human can design, another can understand.
   
You may have to watch the video a few times to see exactly what happens. I still found that difficult, so I made a slow-motion version of part of the video.

And here is that version. Aha. Let’s analyse what we have seen. 

The aliens are roughly cylindrical, about 60-80 cm in length, with a diameter about half that. If they would be solid cylinders they would have a volume of 42 to 100 L, but they must be hollow, so I estimate their volume to be 30 to 60 L. If their density is the same of that of Earth animals, their mass would be 30 to 60 kg. If they would be denser, say with a density of 1.4 kg/L, their mass would be 40-80 kg. That makes them quite hefty.  

‘Inversion fish’
The animation shows rings coming in from the centre, moving forwards and outwards, after which the rings move backwards again, where they no doubt move back inwards and forwards again. The spikes on the rings can be seen to point forwards at first. Then they move backwards over the surface of the rings. I do not think that the rings are separate objects. It seems to me that they form a contiguous surface instead, one that moves over the substance of the animal. You could say that they invert themselves.

Believe it or not, but inverting animals, consisting of a torus with exactly such a gliding surface, has already been discussed on this blog, back in 2013. That discussion was inspired by Thomastapir’s ‘Moebius fish’. I called the resulting type of animal ‘Inversion Fish’, assuming such animals would be small and simple sea creatures, like jellyfish. With all the inversion going on, it would be difficult for them to form brains or guts, so such animals might have non-invertible parts. I meant to follow that first post later with a second one on the same subject, but I never did, for a variety of reasons. The good news is that I can label this post ‘Inversion Fish II’, bringing closure to that long-open end.

I now resurrected some old Matlab routines to animate the inversion fish and pimped them a bit. Here is the result of that; the Inversion Fish is still a simple ring, but it is now rotated to make it swim horizontally. The lines sticking out represent hairs that will help propel it through the sea. The animal was supposed to be at most a few mm in size. 

 

Here is a second animation: I stretched the animal to give it a cylindrical appearance, so it begins to resemble the aliens. 

 

And a third one Inversion Fish, cut in half. The cut surfaces help to visualise the movement of the surface. Note that the surface moves forwards on the inside of the animal, while it is moving backwards on the outside, with not much distance between the two. There is no way to attach the surface to the inner substance of the body, in the way our skin stays close to the underlying tissues. In essence,  something like this can only work if the surface is essentially loose from the subsurface. The easiest way to achieve that is with a fluid between the surfaces. That is why I compared the Inversion Fish to jellyfish: jellyfish are essentially also membranes with jelly in between. But in their case, the membranes do not move in opposite directions.     
     
The spikes
The spikes appear at various points on the bodies, shoot out quickly and in doing so vary in length. They are always straight, never curved, and their width tapers to a pointy end. These ends apparently attach themselves to walls, ceilings or the ground. I did not see anything in the way of suckers, feet, hooks, nails or anything else that could help to attach a fairly large mass to a ceiling or wall. The spikes do not leave any marks either, as far as I could see. What also struck me is that I did not see the spikes sagging in any way. If you use a rope to suspend a weight from a wall or ceiling, the rope will sag a bit. These spikes are also used as rigid legs, and so must be very rigid. All in all, they must be able to withstand compression as well as tension easily, even while they are being formed.  

Now making such a material presents quite a design challenge. Which material can be extruded and absorbed at will and can remain very rigid and strong while it also behaves as a fluid? The commentary says ‘It’s made of ferrofluids, so it can be hard, but when you touch it, it moves like mercury.’ I cannot say I know much about ferrofluids, but my short foray into the subject suggest that the term 'fluid' should be taken quite literally. I did not see examples of hard ferrofluids.

Could you evolve animals using ferrofluids biologically? Obviously, evolution has no preset aim and cannot set out to evolve a ferrofluid. Evolution could start with a readily available source of ferrofluids, or there should be a reasonable reason for an animal to produce them, and after that it can evolve in a different direction. In other words, how do you wind up with tiny magnetic particles permanently suspended in a fluid? And how would you wind up with a handy biological way to acquire and control magnetism? Those are extremely tough challenges, and I doubt they can be met.    

Conclusion
Are these aliens original? Yes, very much so, unless you feel that ‘original’ may only be used for something that that has never been proposed anywhere. That would not be the case here, as witnessed by Thomastapir’s Moebius Fish and the later Inversion Fish. But that is asking too much: I really like the inventiveness shown here.   

Are they realistic as products of biological evolution? I very much doubt it. It will not be easy for biological evolution to come up with an animal whose living matter is essentially the fluid surface of a torus, and in which that living matter can become strong and rigid at will. We should probably add some additional problems here: the animals have no recognisable sense organs, and their brain and other relevant organs would have to be malleable and able to continue working while being inverted (but perhaps you could actually do something like that to an octopus brain, while it would continue working; don't try it!). At the end of the series, the aliens all collapse when the mother ship is destroyed, which is in Earth orbit. The aliens must therefore have a means of constant communication that functions immediately over large distances; should we add radio to their list of improbable biological feats? 

Perhaps it makes more sense to treat them not as the product of biological evolution, but as the result of engineering? Are they in fact bio-inspired robots? I guess we'll see in future series.

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…      

Trying to sculpt a dinosaur (Sauropelta)

This blog and the Furaha project are about speculative biology, so there is no reason to talk about dinosaurs. Then again, you could argue that there are so many unknowns in palaeontology that it is to a large extent a speculative discipline. 

Anyway, I decided to sculpt a dinosaur with polymer clay. Why polymer clay? It is perfectly possible to sculpt digitally, with more detail, and cleaner too. I do so habitually to help me decide on shapes and perspective. And if I would want a physical object, I can order a 3D print. But physical sculpting has its own rewards, and sometimes I would like to have a nice statuette of a rusp or another Furahan animal. 

Why a dinosaur and not a rusp? In the distant past I had used 'Fimo' and 'Das' to sculpt animals, but I was never satisfied with the ease of use or the level of detail. Still, I kept an eye on what people did with Sculpey and similar materials. There are people on YouTube, such as 'Kayakasaurus', who make very nice dinosaurs in polymer clay. I thought that my first attempt would probably not be very good, so I chose something I did not care about that much, which may sound strange. But anyway, that is why I chose a dinosaur. Perhaps foolishly, I chose a material that looked interesting but for which there were not many didactic video's: Cosclay. That is a polymer clay that after baking was supposed to stay flexible, allowing very thin parts without risk of breaking. The video shows that this was indeed the case.

 

The video above shows the result of that experiment. I have also uploaded a version with better resolution to YouTube. 

I will leave it to you whether the attempt was successful or not. Among the things I learned was that I need to have much better control over details, and that means I need a working environment with better light and preferably a magnifying glass. 

The working method was copied from YouTube videos. I started with a nice skeletal drawing by Gregory Paul, from his excellent book 'The Princeton Field Guide on Dinosaurs'. In spite of the title, it is not a Field Guide; how many field guides preferentially show animal skeletons? 

Click to enlarge; copyright Gregory S. Paul

Here is a drawing of a Sauropelta skeleton from that book. I used the trick of printing a scanned image on the desired size, so I would end up with a roughly 1:16 scale model: the model is about 25 cm, half of which is tail. 

 

Click to enlarge; Carpenter K. Can J Earth Sci 1984; 21: 1491-1498

I also had a quick look at some published papers on Sauropelta. Above you see drawings from a formal 1984 paper. Compare the posture and the length of the spikes to the drawing by Paul. The fossils may not have changed much, but the reconstructions certainly do. What I like about the 1984 paper is the emphasis on how close the left and right feet are to one another. I tried to do that in the model, but probably still used too large a distance. 

Click to enlarge; Brown et al Current Biology 2017; 27: 2514-2521

 

And here is a recent drawing of the Sauropelta skin bones that form the large back shield (the 'pelta') . I only found it after I had already baked the final model, so the shield bones on my version are much too big. An accurate dinosaur model would require a large amount of study. Looking at other reconstructions makes me think that most reconstructions rest more on speculation than on science. Mine included! 

But at least I think I am ready for a rusp sculpt now. But first, more painting, and perhaps a stegosaur sculpt, just to be certain.

How global warming changes the future's past in the Furaha Universe

'The Book' starts with some explanations about the planet Furaha, how humanity got there, why anyone would choose to go there, as well as some other background material. The image above gives the reader an idea how large the planet and its two small moons are in comparison to Earth and its large moon. A variety of techniques were used to make it. First of all, for something like this a 'digital elevation map' (DEM) is needed, showing elevation on a grid of longitude by latitude. Such maps are easy to find, for Earth that is, and Matlab's mapping toolbox offers many ways to play with maps. Obviously, I had to make my own DEM for Furaha. The intermediate stage is to make a nice digital map in which colours represent elevation. Second, take a suitable 3D-program and set up a scene with spheres in it. I still use my 2014 copy of Vue Infinite to do so. Then you just wrap the maps around the spheres, set up some light, and you get a nice picture comparing two globes, one representing Furaha, one Earth. However, I increasingly felt that the image I used for Earth might not be appropriate for the future. Mind you, I have never settled on a period in which the future history of Furaha is to take place. Is it the 24th century, like Star Trek? Sometime earlier or later? I do not know and do not care too much. However, the Institute of Furaha Biology is at least some 200 years old, so at least two centuries are needed for that. Moreover, a 'Faster-Than-Light' drive, or an 'Around-Light' drive for that matter, does not seem around the corner, so perhaps we need to give that some time as well. Overall, we are probably looking at at least four centuries. Would the overall contours of the continents look different? The recent report on global warming makes me wonder how much sea level might rise. Humanity is causing global warming, and it is too late to prevent all of it, but part of it can be prevented. If people act in time and wisely, that is. Will they, or will it be a case of too little, too late? The Book is a science fiction project, so the choices are fictional. In the Furaha setting, in that far future, wrong choices were made. All of the Greenland ice melted, and all Antarctic ice, and so the sea rose. By 70 meters. I found that number on the internet as a rough estimate of what would happen if all the ice melted. Wikipedia tells me that Greenland is good for a 7.4 meter 'sea-level equivalent', and Antarctica supplies 58.3 meters, so together they account for 65.7 meters. That is still a sizeable amount.

I took the elevation data and adapted them to reflect a 70 m rise. I then had to edit some areas manually, because the program found some inland areas that it now regarded as 'sea', even though those areas had no access to the oceans. Large parts of the UK are gone, as well as the Netherlands, Denmark, Bangladesh, etc. No current coastal city would escape unharmed. I have no idea how such a change would affect the climate, pollution of the seas and myriads of other matters. In the Furaha universe civilisation endured, because otherwise I would have nothing to write about. But I think these fictional future people would look back to their past, our future, with perhaps some new hard-won wisdom. The citizens of the Furahan Institute of Biology passed a unanimous vote to change the formal scientific name of mankind. They abandoned the old familiar name 'Homo sapiens', meaning 'wise man', and changed it to 'Homo semisapiens': man who is half wise. They felt that wisdom must have two parts: the first consists of the ability to think, and the second requires that those thoughts are acted on. According to the Institute, humanity passed the first criterion, but failed the second.

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!