Skitters ('Falling Skies'), spidrids and footless crabs

The previous post was devoted to spidrids, Furahan radially symmetrical walking animals. In thinking about their movement my attention was drawn more and more to Earth crabs, because the anatomy of their legs proved to resemble the anatomy I had chosen for spidrid legs. I admit that spidrid leg anatomy mostly came about because of a wish to see them walk. There are programming problems that I cannot solve myself (inverse kinematics) and I do not have any of the high-end graphics programs that can do it for me. So that is why I came up with the simple scheme I discussed before: at the hip joint there is a vertical axis of movement allowing clockwise rotation, but all other leg segments have horizontal axes enabling shortening and extension of the legs. Later, the exact same scheme proved popular with robot builders.

Last time I discussed a feature of crab (or spidrid) legs that I still do not understand well: slanting. I tried to contact arthropod experts but without luck so far. But there is another feature of crabs I do not understand: why do they not have feet? Crab legs more or less just end in rounded points. This is odd, because crabs, often living in tidal water, need to be able to get to good hold on the ground they are walking on, or else they may be swept away by the current. You would expect feet with curved claws for that. I have not found a discussion of why crabs do not have feet, just one mention of the fact that they do not. As I was considering adding feet to spidrids, I wondered whether there could be an anatomical reason for their absence. That will be discussed first, and only then will the 'skitters' of  'Falling Skies' be discussed: they have feet.

Click to enlarge; copyright Gert van Dijk

In the past I discussed the influence of leg posture on the anatomy of leg joints, and in particular how many axes are needed. The image above shows a new version of an old design (Mechanicus disneius). In the left image the leg is simply rotated forward around the vertical axis of the hip/shoulder joint: the foot ends up rotated with respect to the ground. While walking, the foot should move along a path shown as a stripe on the ground; in reality the animal moves forwards and the foot stays on the ground; it's the same relative movement. The foot should point forwards during the entire step, and that requires rotation around an axis parallel to the most distal leg segment, shown by an axis sticking out of it. The image on the right shows where the foot should be: many joint positions need to be adapted, but the one important here is the rotation of the feet around that longitudinal distal leg axis. By the way, rotate your hands palm up and palm down: what you are doing is pronation (palm down) and supination (palm up), which is just such a movement, due to the long bones in the forearm crossing and uncrossing.

The need for pronation and supination must be present for any animal with sprawling legs. That does not only include lizards and turtles, but arthropods -and spidrids and radial robots!-. I have not found any mention of how arthropods solve this problem. The robot builders just ignore it. Insects have a series of short segments at the need of their legs, the tarsus, linked through ball and socket joints. Are they how insects cope? Does the tarsus more or less flip around during a leg cycle? As said, crabs have no feet, so the end segment of their legs must turn in place during a step, rotating against the ground. Do crabs have no feet because there is no mechanism for pronation and supination? I cannot believe that. All this rotation with friction without a proper way to grab the ground seems an odd way to design a leg, and yet it seems to be there. If anyone knows an arthropod limb expert, please ask them...

Click to enlarge

What does all this have to do with the skitters of the television series 'Falling Skies'? Well, they have radial legs with feet, in an interesting example of 'convergent speculation'. A skitter is shown above, along with my simplified version to illustrate its anatomy (Disneius horrificus). Skitters have invaded an conquered Earth, but as the story unfolds it seems they did so under duress, so to speak. Their top end shows bilateral symmetry but their nether end has radial symmetry, which is odd. There are more aspects that suggest we should be well prepared to suspend disbelief (I like the series). For one, the legs are overly thick given that there are six of them. In itself that might indicate evolution in a very high gravity, but the sprawled position of the legs argues strongly against that. They can walk along vertical walls, a feature so unlikely there is little need to discuss it. They communicate through radio, an old favourite of speculative biology that seems difficult to get underway in an evolutionary sense. (All right, here is why I think so: the evolution of biological radio might well start with a primitive capability to receive radio waves, but can you see/hear with that sense? Where is the benefit?).

                            
The video fragments above show skitters in action. I have repeated the very short fragments to make it easier to see what is going on. It is clear that their nether ends are indeed fully radial, and that the feet accordingly stick out in all directions.

Above you see another fragment, one I rather like. I have repeated this one a few times as well. The skitter turns as it negotiates the path between the furniture. It must turn, as its top end has clear front and back sides: if it has to face the humans, it has to turn. With that clear preference you would expect its bottom end to have an equally clear fore to aft distinction, but that part is radially symmetrical. The one distinguishing feature of radial symmetry is that it allows movement in all directions. With such feet, a skitter might be expected to walk in any direction with equal ease, even directions in which it cannot see...  

The feet remain planted on the floor during the turn, so the legs in fact rotate around a longitudinal axis of the distal leg segment. That is nice; a pity that the anatomical mechanism is not visible. I very much like the way the animators solved the problem of how an organism with such a wide leg base negotiates the limited space between the furniture, designed for the much narrower forms of humans. The skitter behaves like an all-terrain vehicle and simply puts its legs on the furniture where needed, evening out the differences in height between its feet as it goes. That is very well done, I think.

But still... Leaving spidrids with leg points that pirouette against the ground at every step is very unsatisfying. The feeling is a bit like when you are unable to solve a puzzle, the answer of which must be staring you in the face. I think I will equip spidrids with feet, if only to end the irritation. That still leaves crabs, presenting the same puzzle...    
          

Between the Morae River and the Red Valley

I discussed Brynn Metheny's 'Morae River' project once before in this blog. The project dealt with life forms in a certain geographical area called 'Solturna'. The animals there at first glance looked like Earth's mammals, reptiles, or fish, so you might think that the Morae valley might be somewhere on Earth. But a closer look revealed small but telling differences in anatomy, so you might think that the creatures perhaps stemmed from a not too alternate time-line and were mammaloid, reptiloid and ichthyoid. But a few animals departed so much from regular Earth stock to make you think that they required an extremely early divergence or an unearthly origin. Brynn gave no clue as how to place her creations, and preferred a fluid interpretation. Earlier this year she unfortunately decided to stop working on the Morae River. But that should those who never visited the site from doing so, as it is a great project even if it is no longer updated.

Luckily she did not stop producing odd animals. Far from it! I gather that she is making 'creature design' her career, which hopefully means that there is much more to come. There are several places where you can admire her work: she has a site on Deviant Art where she goes under the name of LenoreKitty. She has a site under her own name, brynnart.com, as well as one going by the name of Fishhook studio. I selected a few paintings for you to see here, and expect that they will make you hungry for more.

Click to enlarge; copyright Brynn Metheney

The pygmy esorifleu
As you can see, this is an arboreal creature with a strong bill, like a parrot's, and six limbs. The middle pair are placed at the top of the animal and are directed upwards, whereas the front and aft pairs are directed downward. There is also a tail, which looks like it is prehensile. This animal can only be a brachiating carnivore. It looks somewhat like my marblebill, to be found on the Furaha site but also in this blog (here and here). A fairly large design difference is that the esorifleu using its middle pair of limbs to swing from, whereas I chose the front pair. Brynn wrote me that the pygmy was designed for a creature design contest. I think the marblebill and the esorifleu are nice examples of convergent speculation.

Click to enlarge; copyright Brynn Metheney

Elegant hunters
And indeed they are. Mind you, the prey look rather dashing as well. The beaks of the hunters remind me of the mouth of a deinichthys. At first glance their body design seems to say 'bony fish from Earth', with its vertical tail, fin rays, gills and dorsal fin. But then you notice that instead of one pair of pectoral fins there are two, giving a jolt to the idea of what exactly they are. What I do not know is whether you have to know that two pairs of pectoral fins are impossible for that jolt to occur. Anyway, four gill slits is an unusual number as well.
I would like to see more of their prey, whose 'Bauplan' seems much more unearthly. I like the bumps on the front of the flippers. Not many swimming animals have those, but humpback whales have very knobbly leading edges on their enormous flippers, and in their case the turbulence they cause actually seems to help. Is that the end of a siphon I see on their sides? Are those expiratory outlets?

Click to enlarge; copyright Brynn Metheney

'Mamma'
No classification problems here: that's a perissodactyl unguloid, or a hoofed animal with an odd number of toes. But are those concentric structures external ears? Perhaps the animal is not Terran after all...
What I like a great deal about this one is how the animals are not simply shown in side view, but are much more three-dimensional. The calf's head cannot be seen, and the mother's head is turned away a bit as well. This is where the trained artist shows herself, I think.

Click to enlarge; copyright Brynn Metheney

A work in progress
Lacking a name, let's call it a 'wip'. If I see correctly there is just one pair of eyes, and the other markings on its head are nostrils and ears. Even so, this animal is more alien than the previous one, with the sail on its neck and particularly the spikes at the base of its tail. Now what are these doing there? They are not placed well for attack or defence, so perhaps they are for display purposes, and display to members of the same species always boils down to sex. Do the spikes serve to impress other wips, or do they provide tactile stimulation during procreation? I had better reign in my imagination here...
It's a beauty though.

Click to enlarge; copyright Brynn Metheney

Another work in progress
If it is, we might as well label it a 'wiptoo'. It is interesting how this head and neck study immediately evokes the notion that we are looking at a very large animal. One reason must be the relatively thick neck. Large animals need proportionately thicker limbs, and that goes for necks too (see here and here for the reasons). Apparently we are so used to seeing the results of these laws of nature that we immediately draw conclusions from seeing their results. Alternatively, of course, this could be a moderately sized animal from a heavy-gravity world, but I do not think so: its eyes are also small in relation to its body. They seem to be camera eys such as vertebrates have on Earth. While bigger animals generally have bigger eyes, eye size does not increase directly with body size, so large animals have relatively small eyes. As with neck thickness, the observer takes these cues and judges the size of the animal, consciously or unconsciously.
Its skin glistens. You can tell from the linear nature of the reflections that its skin is smooth, and I wonder whether it is wet because it just emerged from a swamp or something similar or because the skin itself is wet or oily. A large animal with a permanently wet skin would need a permanently moist and saturated environment. Perhaps it lives as brontosaurs were once thought to do: in humid steaming swamps.

Click to enlarge; copyright Brynn Metheney

There are no animals on this painting, but the image contains a promise. The website of the Red Valley project is already up, but there's not much to see yet. We are promised that animals will appear there in the Fall, so hopefully Brynn won't keep us waiting too long. She wrote me that she is not going to reveal all about the planet: "I might know details about the whole of the planet and such but as far as my viewers are concerned, I'd like it to just be about this valley." I agree with that sentiment: always leave the viewer or the audience hungry for a bit more, and a hint that there is in fact more does wonders to whet the appetite. She added: "I want the flora and fauna to feel alien enough but I want viewers to relate to them as well."
From what Brynn has done in the past, I think she will succeed. The text on the Red River site also states: "No regions, no classification, just this place as it is." Oh very well, I get the message: I should stop trying to classify these animals to see where they belong and what makes them work.

Hmmm; as if I could...

Radial Robots

'Radial robots'; for a title that isn't too bad. I was tempted to add words with 'r' such as 'rampaging' or 'ravaging', but I resisted, as that ran the risk of rather ruining the effect, rendering it ridiculous.

Back to the matter at hand. When I first thought of a radial walking pattern, resulting in Furahan spidrids, I was content to visualise the gait by writing some programmes in Matlab. The results are shown on the Furaha page, and some were featured in the blog as well (here and here). I never imagined I would see really see spidrids walk. Literally, of course, I never will, unless creative bioengineering kits become available quickly, which is unlikely. But walking robots have emerged on the scene since I thought of the spidrids, and among them radial leg designs, as opposed to bilateral symmetry, seem to be quite popular. You can even buy kits to build one yourself. As these designs probably evolved independently, it is interesting to see how parallel these forms of evolution have become: convergent speculation? I therefore surveyed the internet to see whether their anatomy and gaits resembled those of Furahan spidrids. As most of the robots out there seem to be hexapods, I made a quick hexapod version of my originally octapod spidrids (if you need information on spidrids, go to the land section of the Furaha site and select 'walking with...'). A mutation, if you will.

Mutated spidrid; copyright Gert van Dijk

And here it is. I cannot call it a spidrid any longer, as that name evoked spiders, and therefore eight legs. Suggestions are welcome. The beasty walks with the simplest possible gait: that is a double tripod gait, in which the six legs are divided into two groups of three. The three legs of a group move in unison, and the two groups are exactly out of phase. Provided that each leg touches the ground longer than it is off it, there will always be at least three lags on the ground (either that or six). This gait, together with sprawling legs, provides excellent stability. As discussed previously, this is useful for very small animals, soupy atmospheres or a very low walking velocity. It also doesn't require subtle neural control, making it suitable for today's rather dumb robots. It is also a bit boring, which is why my spidrids walk with different gaits, but that is another matter.

Click to enlarge; copyright Gert van Dijk

Next, a scheme to show how the joint anatomy works. Spidrids are very simple: there is a joint at the 'hip', in which the entire leg can rotate clockwise or anti-clockwise. The rotation axis is vertical, indicated by a shiny metal axis and a red arrow. All other joints are simple hinges allowing the segments of the leg to be stretched or bent, and the axes are horizontal, indicated by more shiny axes and blue arrows. Now that the basic spidrid anatomy and gait are clear, it is time to see whether the robot creators have evolved completely different approaches, or whether they evolved the same ideas.

The first video is of a hexapod robot from this YouTube source. As soon as you see it move you will see that its leg anatomy is exactly that of the spidrid: there is one vertical axis at the hip, and the leg itself only contains horizontal axes. The gait is simple as well, in that the legs move in two sets of three, just like the animation above. I like the clunking sound it makes, as if a whole battalion of Cybermen comes clunking down the street. It does one thing my spidrid animations do not (as yet): it changes gait, in the sense that it moves from a circular rotation to walking again (I could have programmed that, but that is a lot of work...).

Here is another one (source here), and this one has a more biological feel to it, in the sense that the movements seem smoother and less mechanical. It does have the same basic anatomy though. Its gaits seem more diverse.

Just to show that radial robots are not restricted to six legs, here is an eight-legged one (source here), more reminiscent of the original spidrids. With eight legs there are many ways to move the legs, and the risks of falling are diminished, as it is easier to spread weight-bearing evenly around the centre of gravity.

Click to enlarge; source here

Finally, just a look at this one suggest a radical departure from the norm. It has four legs, but that is not the point, as it still clearly has a radial anatomy. The legs do not seem to be attached in the usual fashion: where they touch the body the joint seems to be a simple hinge with a horizontal axis. In fact, all its joints seem to have horizontal axes. So how does it move its legs in more than one direction? How can it walk if all its legs can do is stretch and shorten? The answer lies in its design: this robot is fundamentally different. It is part of a project in which the robot has an internal representation of its body, so it can learn to move once more after its legs have been damaged. In short, it is a lot more intelligent than its dumb brethren. If you want interesting movements, always add a brain (an insect type of brain will do).

And this video shows how it moves: it tilts its body, and that takes the place of (anti)clockwise leg rotations. By varying the tilt of its body the reach of its legs becomes much more varied than with an immobile body. In fact, with the anatomy it has, body tilt is the only way forward (pun intended). What a clever design! I love it.

Does this mean that the 'usual' radial design is flawed? I think not. There are good reasons why this design was invented several times, for robots as well as spidrids: it is simple and allows good mobility. Now, if the robots develop more interesting and sophisticated gaits, we are in business: model spidrids in your own home; what more could you wish for?

Warren Fahy's "Fragment"

Predators resembling mantis shrimps, insect-like life forms whose wings are placed in a radial design, and covers of books that do not exist... You might think that this is the Furaha site I am talking about, and indeed it could be. But the same characteristics also describe another speculative playing field, and that is "Henders Island". 'Fragment' is a novel by Warren Fahy that came out last year. I have never discussed any of the large number of interesting life forms in written science fiction before; the reason is simply that I have a strong predilection for visual matters. 'Fragment' is accompanied by a website with quite a bit of visual material. Some of the images there are printed in the book as well. I will not describe the story in any detail; if you like an adventure story along the lines of Crichton's 'Jurassic Park', you will like this book as well. The story begins with a camera crew stumbling upon an unexplored island. 'Unexplored' means except for a captain Henders a few centuries ago, who noted its existence. The island is the remnant of a former continent, where life went through its own evolutionary process regardless of mainstream evolution. You might think that that is what islands are for, in fact. The Galapagos islands, definitely a breeding ground for somewhat original shapes, are 5-10 million years old, and Madagascar, the home of lemurs and some of the oddest trees in existence, has been isolated for some 100 million years (or so Wikipedia says). It makes sense to think that longer isolation allows further separation between island and mainland life forms, giving rise to the dictum that 'weirdness waxes with time'. Well, Henders Island has been isolated since the Precambrian...

Click to enlarge; copyright Warren Fahy and Company

The resulting life forms cannot even be categorised in modern terms. Above is a Henders rat attacking a poor mongoose, let loose by scientists to see how well 'normal' animals fare against Henderian ones (the Henderian ones kill them in minutes). This 'rat' has a ringlike internal skeleton that seems to have developed from a crustacean (?) exoskeleton. They have fur, give birth to live young, have blue blood, have interesting eyes (mantis shrimps again), a second brain with its own eyes on its back. One of their 9 limbs is really a tail; the first two pairs of limbs are adapted to catch prey ('hypercentaurism').

Click to enlarge; copyright Warren Fahy and Company

This is a Henders wasp, one of the radially symmetrical flying life forms. It seems to have five wings, which means it will not be easy to develop a wing 'gait' that does not produce a wobble in flight. The wings stick out but do not seem to move to and fro as frantically as you might expect. They are quite a bit like my tetropters; that's convergent speculation, all over again. Previous posts on tetropters started here and continued here, here and here. (By the way, I have solved the major hurdles of producing smooth tetropter flight animations, but there is still quite a bit to do.)

Click to enlarge; copyright Warren Fahy and Company

Life on Henders Island is so extremely aggressive and efficacious in eating anything anywhere anytime that the rest of the Earth had better watch out. Step on land and you will be stung, bitten into or simply turned into shish kebab in a few minutes. You cannot even trust the 'plants'! Interestingly, the book contains discussions between the protagonists whether or not an ecosystem can flourish without any clear distinction between herbivores and carnivores. I suppose I am one of the doubters: if anything that can be eaten will be eaten in a matter of minutes, you wonder how anything can live long enough to grow large. And there are large animals; above is a spigre with a human for scale. Large animals may be fairly immune to attacks from animals half their size, but they are not so to insect-sized or smaller animals.

Click to enlarge; copyright Warren Fahy and Company

Small Henderian animals are certainly dangerous; above is a disk ant, a radially symmetrical animal, like a spidrid, but much nastier. Disk ants carry their own young that carry their own young etc, so there is a cascade of nastiness. The book describes how they bore their way into flesh and open a leg to the bone in a matter of seconds; a bit too quick, I thought: movement takes time, certainly on a miniature scale. But what keeps them from devouring a spigre? I do like the disk ant's movement: it can walk as any decent radial animal should, but can switch to rolling on one side. Likely? Probably not. Fun? Definitely! Reading the book gave me a distinct feeling that the author had a film in mind, and indeed Mr Fahy wrote me that a film is 'definitely now in the works'. I suppose that that is why so much visual material has been developed. Because I like to credit the artists where possible, I asked him for their names, and here they are: Daren Bader, Steven Olds, Ron Lemon and Michael Limber. I guess we now wait for the sequel and for the film. I do hope that the movie makers will pay more attention to how animals move than the designers of Avatar did. If you read 'Fragment', it is clear that the author likes his creations and thought a lot about their biology; that's a very good starting point.

Anatomy of an alien III: Europan waters

The first blog entry in this new decade travels back in time again, to the 1997 BBC television series 'Anatomy of an alien'. This time the chosen fragment chosen deals with life on the moon Europa, or perhaps it may be better to call it 'in Europa', as the life forms in question are found in water underneath an ice cap over 15 km thick (according to the documentary).

You will first see an explanation of deep ocean vents on Earth, and those are never boring. Jack Cohen makes an appearance again, to speculate about similar vents in Europan seas or lakes. The vents are surrounded with walls built by bacteria that stretch upwards to form very long tubes. The speculation really gets underway when it deals with the ecosystem surrounding these tubes. There are creatures that can bite or drill through the wall of the tube, after which they gorge themselves on bacteria from within the tube. Of course there are predators out there too, preying on the 'grazers'.

Click to enlarge; copyright BBC

Here is a picture of a bacterivore; the predators have almost exactly the same shape. There is a feeding trunk on the front end of the animal, underneath the central opening. There is another opening in the front end of the animal; what is it for? Unfortunately, the documentary keeps completely silent about the body plan of these animals, which is a pity.

There is an opening right at the front, and one at the back. The one in the front is not for feeding. Perhaps these are the inlet and outlet openings of its respiratory system. After all, there is no reason to have air go in and out through the same opening, as is the case in Earth's tetrapods. Actually, using the same opening for air moving in and out is not good engineering, and is probably just a remnant of lungs starting as a sac with just one opening. In Earth's fish, waters enter the mouth and leave through its sides after having passed through the gills; a much better design! Obviously, evolution should be able to find other solutions on other worlds: air enters the lungs of Furahan hexapods through openings at the front of the trunk, and exits the body at its rear end (not that you can see that on any of the paintings on the site, but is true nevertheless).

Click to enlarge; copyright Gert van Dijk

Then again, the Europan bacteriovore's openings might have to do with propulsion, in which case these animals would have the same propulsion system as is found on Furaha. Just visit the page, choose the 'water' icon; choose 'swimming with...', and then got to the 'tubes' page. There you are. To save you the trouble I copied the image to this blog message; mind you, the image shows the external appearance of the animal; to understand how it works you still have to visit the page. I doubt that this propulsion system was separately invented for the Europan creatures. If so much thought would have gone into their design, you would think that this neat feature would be mentioned, and it isn't.

Still, there is something else about their propulsion that makes me wonder. The animals have a set of three fins around their body, more or less like the pectoral and back fins of sharks and dolphins. This makes sense, as three such fins are useful in countering rotations around the body's front-to-aft axis. You would want such fins near the centre of the body, as they would impede movements around the other axes if placed at the front or the rear of the animal. These animals indeed have three such wings right where you would expect them, around the centre of mass. As an aside, you may well wonder why there are three. To counter rotations, two or four (or more) would work just as well. Their area may have to increase if you have fewer fins, and vice versa, but that does not seem to be an important factor. Some whales have large dorsal fins and some have no dorsal fins at all, so having two seems to work as well as having three. Why are there never four? Is this just an evolutionary accident? Perhaps it is easier to have more such fins at the bottom half of the animal than at the top half, if only to make it easier to keep the body upright.

Anyway, now have a look at the tail of Europan bacterivores: there is another, smaller, set of three fins. That only makes sense if the animal needs more to be kept on track like an arrow, but this 'triad' fin design is not optimal if you use the tail for propulsion. Suppose you wish to beat the tail in an up and down direction: with a triad set the top fin will be useless for propulsion. While moving upwards it might even start to bend sideways and then it would impair propulsion. The other two will not be perpendicular to the direction of movement and will therefore not provide optimal thrust. No, if you want a beating tail, the surfaces providing propulsion must be perpendicular to the direction of the beat, and surfaces not aiding in propulsion should not be in the way.

Whale shark  / orca / orca; click to enlarge

The tails of sharks and whales provide excellent examples of this design. The pictures above were taken from the internet. The whale shark beats its tail sideways, and the 'stem' of the tail, just before the tail fin, is flattened sideways. In this way, there is room for the attachment of muscles and ligaments without impairing propulsion. The two photographs of orca's show that an orca's tail stem is flattened vertically, exactly as expected for an animal that beats its tail up and down.      
                  
Back to Europan bacterivores. Their tails suggest a mode of propulsion similar or identical to the ones I invented for Furaha. Convergent speculation once again? Possibly; remember that this type of propulsion results in linear motion without any externally visible means of propulsion. That is not what you see in the video. Instead, the predators near the end can be seen to swim with a strongly undulatory pattern, like the one you would expect for animals with sideways-beating tails.

I wonder what happened to cause this odd combination of a design plan with a movement pattern that doesn't seem to fit the plan. The people who designed these animals knew what they were doing, so the answer probably does not lie there. Perhaps the animators simply added a familiar type of movement to add some spice to the footage? That is possible: I remember from conversations with Steven Hanly that the movement of Eponan uthers in the same documentary did not come out as planned either. I doubt we will ever know.

 

Alex Ries and the Birrin

Those on the lookout for speculative biology that catches the eye as well as the imagination could do much worse than to have a look at the work of Alex Ries. I have kept an eye on his website for several years, and had drawn the mistaken conclusion that he probably stopped working, as the site hadn't changed for quite a while. I was wrong, and should have searched in other places. It would not have taken that long to find him again on Deviant Art. (you will find more paintings on Deviant Art by typing his name in the search box). But what is more interesting than my shortcomings are his messages there that he is planning a book on his extraterrestrial creations. He is certainly not alone in wanting to do that; in fact, aspirations of producing a book are a recurrent theme among those who spend considerable time on their speculative biology creations. His remarks reveal that the book might revolve around an intelligent species, the Birrin, so perhaps that species is a good place to start looking.

Click to enlarge; © Alex Ries

This one image speaks volumes. The first is that Mr Ries really knows his business as an artist (I wish I could paint in such a assured manner). Obviously, you can also see that it is an intelligent species (or at least it has intelligence in the toolmaking sense, and I am not certain that that is enough to qualify). Something else that struck me is what the body plan of the Birrin reveals about its planet. There is no indicator of scale, but the objects and choice of perspective suggest that the Birrin is at least one meter tall. It must live on a low-gravity world. I think so because its legs are rather spindly and stick out sideways, instead of being held vertically underneath the body. On Earth such limb positions only work for animals that are rather small, up to the size of a coconut crab, but most animals with such limb designs are smaller that that.

The reason for this is that gravity affects animals of different sizes in different ways, a subject known as scaling. It is less complex than it sounds. Suppose you make an animal twice as large in the sense that its height, width and breadth are all twice the original amount. The large one will weigh 8 times as much; that is because weight relates to mass, and mass relates to volume, and volume relates to length by a power of three. Now the cross area of its legs will be four times as much as in the original animal, because area relates to length by a power of two. The strength of legs is relates to their cross section, so what we have is an imbalance: the animal's weight has increased more than the strength of its legs. The solution? Increase the cross sectional area of the legs out of proportion. That's why elephants have thick columnar legs held under the body, and spiders have thin ones that can stick sideways. Can you have a large animal with spindly legs sticking sideways? You can, on a low gravity planet. Alternatively, the material the animal is made of are incredibly strong (how about a skeleton of biological carbon nanotubes?). The Birrin doesn't look very small but has thin legs, so I assume it lives on a low gravity world. I wonder what really small animals look like: hair-thin legs?)

Anyway, I cannot resist plugging the concept of 'centaurism' once more; the Birrin looks like its manipulative front legs have evolved from walking legs, so there we are again...

Click to enlarge; © Alex Ries

Here is another fine animal, one with (largely) radial symmetry. It is good to know that tetropters and spidrids are not the only animals in the fictional universe with radial symmetry. They have their counterparts in the known universe, with anemones and starfish and the like, but sadly we know of no animals walking around with any degree of elegance. I like the anatomical details of this one. I have no idea whether or not it is supposed to live on the same world as the Birrin.

Click to enlarge; © Alex Ries

Click to enlarge; © Alex Ries

What an intriguing shape. It is probably so intriguing because it is not immediately obvious what part does what, or why it is where it is. That is what makes it convincingly alien, I think. Is it a passive floater? It has a rather large bladder, apparently larger than a mre swimbladder would require. What are the membranes for, I wonder; perhaps they are a sea anchor to make it fave waves head-on?

Click to enlarge; © Alex Ries

This one I found on Deviant Art. This animal is an excellent example of convergent evolution. I do no just mean that it is similar in some ways to seals, turtles or plesiosaurs, with its apparent 'swimming with wings' design. I was thinking about 'convergent speculation', meaning that it resembles a design that someone else has also come up with. In this case that someone is me, but you see this happening everywhere where people sit down with a sketch pad and create new animals (while writing this I hesitated a bit with the word 'create', because creationists have tainted it to such a degree that it is difficult to use without evoking wrong connotations). The animal I was thinking about follows:

Click to enlarge; © Gert van Dijk

See the resemblance? Mine was just a very rough sketch, but it conveys the general idea; they are 'AYUS' (As Yet Unnamed Species) from the 'Fishes IV' class. There are differences too, such as the apparent size differences, with mine at about a meter, and his perhaps at humpback size. But look at the similar design of the mouth parts. Before anyone thinks otherwise, I am not saying that either one of us took the idea from each other's work. That cannot have been the case anyway, as mine was done over 10 years ago and has never been published.

It's a simple case of convergent speculation! Of course there are clear influences to be seen in some people's work pf others'ideas, I think that Alex' work looks all his own. Anyway, there are a limited number of biological principles to go around, so all of us tend to arrive at the same ones, having all been subjected to similar ideas. Luckily, there are infinite ways to arrange such similar ideas (and if that sounds a bit like Mr Spock, so be it).

Be certain to have a look at the websites I mentioned, as there is more to see there. But not enough to satisfy the appetite for more... I hope Alex Ries will be successful in getting his book published, because his work makes me very curious to see more of it.