Saturday, 17 February 2018

Rusps turn out to follow biological rules about the weaponisation of tails

I recently came across an interesting paper on the evolution of the use of tails as weapons in Earth animals. This turns out to be a fairly rare occurrence, and perhaps that rarity helps explains why animals with tail weapons are so spectacular. After all, we take the common for granted, and it is the departure from the common that attracts attention.

The glyptodont Doedicurus; click to enlarge.

A nice example on an animal with a tail that is obviously useful as a weapon is the glyptodon genus Doedicurus, a giant armadillo-like mammal, the size of a small car. Doedicurus was encased in strong armour and endowed with a tail with an impressive thickened club at the end.

Click to enlarge; Pinacosaurus Grangeri; Copyright Gregory S. Paul. Princeton field Guide to Dinosaurs, second edition
Ankylosaurs had the same idea, but much earlier. As far as their design was concerned, they went overboard in adding an array of large sharp spikes to their armour.

Click to enlarge; Spinophorosaurus nigerensis; Copyright Gregory S. Paul. Princeton field Guide to Dinosaurs, second edition
Some sauropods may also have had body armour as well as similar thick knobs on the end of their tails. Only one sauropod (Spinophorosaurus nigerensis) apparently sported pointy spikes on its tail, shown here as a juvenile, and drawn by Gregory Paul (I do not think I have to urge dinosaur enthusiasts to get his book 'The Princeton field guide to dinosaurs'). If these long tails were swept at high speed, the transfer of all that kinetic energy should do some real damage. But perhaps a simple threat, along the lines of 'Make my day, punk' would be enough to prevent an actual fight.

The paper in question has the title "The evolution of tail weaponization in amniotes" and is written by Victoria Arbour and Lindsay Zanno. The paper describes which features are the evolutionary precursors of the evolution of tail weapons. The authors performed a thorough statistical analysis of many body traits, and looked separately at four aspects of tail weaponry:  tail lashing, bony terminal tail spikes, a stiff distal tail, and an expanded tail tip.

Click to enlarge. Arbour & Zanno 2018

Here is a figure of the paper, showing these four aspects and the features they are associated with. The result of all this is that you are not likely to find tail weaponry in agile quick-footed predators. If you were designing just such an animal for your speculative biology project, you should probably pause to consider its likelihood. Tail weapons seem to be a last resort for large slow herbivores who already invested in body armour. The authors make the point that equipping heads with weapons occurred much more often. This seems odd because heads are already filled with important structures that should not be damaged, whereas damage to a tail is probably much less risky, so you would expect 'anterior armatification' to be less common that 'posterior armatification'(I could not resist latinising 'weaponisation'). The authors do not speculate why this should be so, but I wonder whether the effective use of weapons requires excellent motor control, something that in turn depends on excellent sensory control, meaning sight. If so, the animal's body may simply be in the way, so it cannot see well enough where to place the sting in its tail.
   At any rate, the authors state that armour in mammals evolved in those animals that are neither small enough to hide nor large enough to deter predators by size alone, and that live in open environments. Close combat with a predator must be a risky business, so the best strategy may simply be running away faster than a predator. And if flight is your main strategy, heavy armour is not going to help. But  a wholly new set of constraints must come into play if you have no chance to outrun your predator to start with. Defensive features such as large size and armour then may become useful, and it seems that active weaponry is the last feature on the list to evolve.

Click to enlarge; copyright Gert van Dijk

So glyptodons, ankylosaurs, stegosaurs  and some sauropods all fit the 'big slow armoured' description to various degrees. And so do Furahan rusps! The image above shows half a rusp from an unfinished painting (for more on rusps, use the blog's search function). From my very first rusp sketch on, rusps were large, had thick hides and used their whips as active weapons. Of course rusps have front as well as hind whips, so the word 'tail' is not applicable at all, but the point is clear; rusp whips are analogous to the 'weaponised' tails of Earth. Those early rusp sketches predated the paper as well the posts in this blog about rusps by many years. I do not remember exactly how much of the rusp body plan came about consciously. I think that I started with a long body shape. Add to that some wondering why many Earth animals are so vulnerable at their rear and sometimes along their middle as well. As the earliest sketches show eyes on middle rusps segments as well, rusps must have started with a weak encephalisation tendency. From there on the double encephalisation seems natural. Note that the posterior whip is well controlled by its own ring brain, with excellent visual information available to direct the strikes. But part of all this may have come about through largely unconscious associations while sketching. Once a design is on paper, it is often hard to say where it came from. Regardless, it is nice that the meme 'rusps have whips' can now be attributed to a firmly established biological principle.

Much as I like the paper, there is a minor matter that might have made it even nicer. Rather than 'tail weaponisation', the authors could easily have used a word that is both relevant and fun: a tail weapon is a 'thagomiser'.

Click to enlarge; copyright

The first use of 'thagomizer' is shown above (this blog uses British spelling, so I assumed the word would become 'thagomiser' in the UK; the rules aren't always clear...).
   It was published as one of Gary Larson's Far Side cartoons in May, 1982. Actually, this colour image stems from a later luxury edition of all Far Side cartoons. Poor Thag Simmons. For 'Far Side' fans, a caveman called 'Thag' occurs at least once more, and one cartoon, taking place in modern times, featured a 'Mr Thagerson'.
  At first glance the word thagomiser seems to indicate 'to turn an object, animal or person into thag', but the real meaning is obviously a 'structure to kill animals or persons, in particular Thag Simmons'. The word has later been picked up in the scientific community to describe the tail weapons of stegosaurs, and apparently of stegosaurs only. I propose to widen its use to all tail weapons.
   As an author of scientific papers myself I realise that the use of humour in scientific papers can be tricky as it is often frowned upon, and you never wish to harm your chances of getting a paper accepted. (I once inserted the phrase 'This resistance is futile' in one of my own scientific papers as an irreverent reference to Star Trek, but I do not think anyone ever noticed).

If we use 'thagomiser' as a word for 'tail weapon', the paper could have been called "The evolution of thagomizers in amniotes", which would be clear, succinct and elegant, but admittedly probably too flippant for a serious paper. Once 'thagomiser' is an accepted word, can we resist to stop there? The tendency to evolve a thagomiser then might become 'thagomiserificability', and the transition process from 'nonthagomiseriness' (not having a thagomiser) to 'orthothagomiserity' (having a proper thagomiser) is 'thagomogrification'. Obviously. 

Wednesday, 27 December 2017

"The Spirally Slanted Spidrid's Mad Dash For Safety!"

Last September I presented part of a painting showing the Mad Sickle, a species of spirally slanted spidrid ('slanties'). The comments quickly gave rise to two new ideas: the first was that the legs and body of slanties might hook up to form a nearly impregnable wall. I should probably do a painting of one. The second was that slanties might well move by cartwheeling. Imagine that as follows: a spidrid's body along with the legs sticking out in all directions forms a disk; now flip the disc onto its edge and roll it along; that's it.  Slanties might use this trick to escape very quickly down a hill.

As usual, life on earth manages to trump anything the speculative biologist can think of. To prove that, here is a short video showing a Namibian spider using exactly that same trick to escaper down a hill, narrated by Sir David Attenborough. There are also spiders that actually do a series of somersaults, head over tails, but that is another type of movement and also another story: here's a video).

Slanties have an additional trick up their sleeves: once flipped on their side, there is nothing to stop them from using the power of their legs to make this an active way of locomotion. Slanties need not be content with passively rolling downhill; they can get out of the way on horizontal terrain too. Actually, they could even roll uphill. I do not think that that would be more effective than normal walking (normal for slanties, that is!), but they could. 

Mind you, I am not saying I am the first to invent this way of locomotion for a fictive animal. I have written about Warren Fahy's 'disc ant' in the past, and there may be earlier manifestations as well.

So here is a quick animation of a slanted spidrid moving in this fashion. The legs flex and extend while the body rotates. I suppose it could also move on the other direction with nearly the same movement. We are looking at the dorsal side of the beast.

Here it is again, rolling in and out of view.

I doubt the animal would use this type of movement as part of its normal repertoire, because I do not think it would be able to see well, with the entire world circling around them like mad. In this respect, the movement is a bit like 'cernuation', a term to describe the movement of the 'squibbon' of The Future is Wild. To read about possible visual problems, find the posts here and here. The poor spidrid only sees the world as a blur when wheeling around in this way, and that is why it uses wheeling only as a last resort to escape from predation.

Sunday, 24 December 2017

Run, rusp, run!

I keep coming back to rusps because their basic centipede shape allows me to play with gaits and movements more than I thought at the start. So far, I have only shown very large rusps, 'megarusps', having a mass equalling or surpassing that of sauropods. If you need to brush up on your crambology (yes, I invented a word to describe the knowledge of rusps), start with some earlier posts: one, two, three and four (there are more, but these will do). Of course, you can also learn about rusp gaits on the main Furaha page.  

Now, megarusps are immense, and you should not expect them to hop and jump around a place like a rabbit on speed. Instead, expect them to move ponderously and solemnly. Still, megarusps must have evolved from smaller ancestors, and that by itself suggests there could be lots of medium and small rusp species, and indeed there are. And then I wondered whether their multilegged nature might keep them from running fast?

Click to enlarge; copyright Gert van Dijk

Here is my earliest sketch of small rusps again. I have not done any full paintings of such minirusps yet, but I do envision a fruitful adaptive radiation, including arboreal and burrowing species.  I have finished two paintings showing metriorusps ('metrio-' indicates medium-sized), and to do so I had to think about their gaits and in which way these would differ from those of megarusps.

Digging rusp. Click to enlarge; copyright Gert van Dijk
Varkrusp. Click to enlarge; copyright Gert van Dijk
 Here are some sketches of metriorusps, that did not make it to 'evolved' status. I played with the idea of differential leg development, so I could have digging species. That design has not made it to a painting, but running and armoured rusps did make the 'evolved' status, though.     

Millipedes and centipedes on Earth can move pretty fast, but they do not really run. Can rusps run?  The answer lies in what exactly is meant by 'running'. On the one hand you can simply interpret the word as 'walking quickly', but there are more complex biological connotations too.
  Walking consists of cyclical strides, and each stride consists of two phases. In the stance phase, a leg is pushed down onto the ground and backwards, providing upwards and forwards force. In the swing phase, the leg is lifted and moves forwards so it will be ready for the next stance phase. During the lift phase the animal should not fall, and preventing that is usually accomplished by having other legs on the ground at that time. To walk more quickly there are few options: increase stride frequency and increase stride length. The latter can be done by having long legs and by swinging it over the largest distance possible, and to get that working, the time a leg is on the ground will have to be shortened.

copyright Gert van Dijk
 This is precisely what happens on Earth. Here is an old animations of mine showing a horse walking. When walking, each leg is on the ground for more than half the time, so there are likely to be multiple legs on the ground at any one time. The slower an animal moves, the more the situation resembles standing still, and for an animal standing still its centre of gravity must fall within the area described by the feet: that is static stability. The stars in the animations represent the corners of that area. The order in which the leg moves ensures that the area has the shape of a triangle under the body.
copyright Gert van Dijk

For a galloping horse, each leg only touches the ground for a short fraction of its movement cycle. The result is that the chances are low that many legs will touch the ground at any time. In fact, there may well be no legs on the ground at all at some times, so the animal is in fact making a series of jumps. At high speeds static stability gives way to dynamic stability, meaning the animal is kept from falling through inertia and a footfall at the correct time and place.

Running is regularly defined as walking with each leg touching the ground for less than half a walking cycle. On earth, all really fast animals use these principles. Having said that, it is time to go back to centipedes and rusps. Centipedes do not run: their stance phase typically lasts much longer than their swing phases. This increases the chance that there are many legs on the ground at any one time, and, seeing how many legs rusps have, this is almost a certainty. This adds up to there being no jump phases, which seems a bad idea if we want a fast rusp.


The answer, I thought, would lie in the gait. The animation above shows a rusp with a slow gait: each foot is on the ground more than half the time. In real life, the animation may have to be sped up for a more realistic effect, but at least the movements are well visible. To support the body well, no region of the long rusp body should be unsupported for a long time, and that is achieved by choosing specific phase differences between the legs. In this case, these seem to work reasonably well. Mind you, rusps have typical 'zigzagzig' legs (see here, here and here for what that means).

The next step, above, is to equip the rusp with a different movement cycle for its legs; the legs now swing further and touch the ground less than half the time. I kept the phase differences the same for comparison. Fortunately for this rusp, its legs do not kick one another with this setting, so the result is not at all bad. There are always legs on the ground though, and that may limit a further increase in speed.

So the gait is the next parameter to tweak. Here, the phase difference between successive legs is much less than before, so the legs on one side move almost in unison. Still, at the moment the last leg on one side leaves the ground, there is already a leg just touching the ground on the other side.            

That can easily be amended. Now the phase differences are almost gone, and there are two periods in the movement cycle when there is no foot on the ground at all. Again, you will have to imagine a proper film speed. This rusp is going so fast, its feet hardly touch the ground!  

So yes, I think there are ways to have rusps run. Actually, they might be able to change phase differences very subtly and continuously, giving them a 'continuously variable transmission', unlike Earth's large mammals, that typically have up to three gaits to choose from (walk, trot and gallop), each with a specific preferred speed.  But that will also depend on energy requirements, something I haven't studied in any detail. 

Click to enlarge; copyright Gert van Dijk

So here is the scale diagram of the runrusp, one of the metriorusps that has already been painted. To close with, it may be interesting to know that I leave hexpods for last, because I am not fully satisfied with the animation of their middle legs yet. But I must say that exploring all the nonhexapod lineages on Furaha is perhaps not a bad idea: it gives more attention to designs that are least Earth-like.  

Sunday, 22 October 2017

The Trench Gobbler

For once I will show a complete painting. Well, more or less. The painting in question is part of a two page spread concerning 'Fishes VI'. The six groups of 'Fishes' are part of the hexapod family tree, with Fishes I, II, III and V as the direct ancestors of terrestrial hexapods, and Fishes IV and VI as parallel aquatic groups. Mind you, I wondered about using 'Fish' instead of 'Fishes', as 'Fish' in English can be both singular as well as plural. A singular language, English.  I found that 'Fishes' can be used to describe multiple species, so that seemed the right choice.

In Fishes VI the third, i.e. the last, pair of flippers have fused to form a horizontal fluke, very much like that of whales. The problem with making 'Fish' alien is the high probability that a torpedo-like streamlined shape is rather likely to evolve as a 'universal' feature. I chose to accept that, so 'Fishes' superficially look much like Terran animals. But they share their world with cloakfish, kwals and aquatic wadudu, so there are definitely some odd shapes to be found too. And Fishes VI are not all that 'earthy': after all, they have four jaws, four eyes, their respiratory system is completely separate from the digestive tract, etc.

The painting combines several themes. I will split it in four panels that show various species of Fishes VI in 'powers of 10', meaning each species is 10 times as large as the previous one, starting at 4.5 cm. Each panel will also show the species eating, so food webs can be illustrated as well.

Click to enlarge; copyright Gert van Dijk
This is the Trench Gobbler; I haven't thought of a binomen yet. This painting forms the second panel of the four. The Gobbler is a typical deep sea species. In this biotope, the only light is that produced by lifeforms, and these are scattered far and wide. This is in fact a very barren ecosystem, which is due to the fact that it is almost entirely based on a slow and sparse trickle of organic material from above. Before anyone asks, I do not know whether there are hydrothermal vents. Animals need to conserve energy here. The water is largely still, and there is no need to swim fast habitually. Hence, there are no fast swimmers here, so there is no overriding advantage in streamlining. If the rare opportunity to catch some fresh food presents itself, it must be jumped upon, because there may not be a second chance anytime soon. These two influences together have resulted in very odd shapes, just as on Earth. The Trench Gobbler has elongated lateral jaws to grab anything possibly edible. In this image, it is attacking a tentacled creature, probably some larval Cthulhuoid. The larva has just emitted a cloud of bioluminescent ink to try to escape, a trick that seems to be working.

Click to enlarge; copyright Gert van Dijk
And here is a detail, for once at full resolution. It is fun to paint such structures, in particular the somewhat glassy structures of the teeth and fins.      

(PS: There is something wrong with my access to the main Furaha website, so I cannot update the loading screen for a while. To check for new posts you should check here directly)

Saturday, 2 September 2017

Spirally slanted spidrids II

The post has the simple purpose of showing that there is progress with The Book. Readers with good memories may remember that I write about spidrid gaits back in 2013. In one post, I toyed with the idea of changing the plane of movement of the spidrid legs from a purely vertical to an angled one. This was inspired by the legs of many crabs and by those of scorpions.

Click to enlarge; from Wikipedia
Here is a nice image of a scorpion from Wikipedia, showing that the plane of the legs is not vertical but at an angle to the ground.

Click to enlarge; from Wikipedia
And here is a 'sally lightfoot' crab (Grapsus grapsus) also from Wikipedia. Note that the hind legs are seen edge-on, so the plane in which they operate is at an angle of that of the surface on which it stands. 

This inspired a very lively discussion in the comments sections why the legs would be slanted. Among the possible advantages were that the animal would be less high, so it could fit in a crevasse among rocks, or it would be less likely to be swept away by tidal waters. Another argument was that the slanted posture allows more muscles to be recruited for propulsion.

Well, I can now add that I found some evidence for the latter argument, in Mantons's Arthopods (There is more on that book in this post). It is difficult to find anything on the biomechanics of arthropod joints. It seems that most of the relevant work was done in the 1960 and 1970's by Manton. In the end I bought a second-hand copy of her book, which proved to be one of the most densely-written science books I have ever read, but it contains an enormous amount of information. She wrote about 'rocking' of arthropod legs, the word she used for what I described as 'slanting', and her reasoning was that it recruited additiopnal muscles for propulsion. No formal proof though! It does not mean the other arguments are invalid though!

In 2013, I produced this quick and rough animation of what a 'spirally slanted sipidrid' might look like.  I recently sat down to do justice to spidrids in The Book, which means doing a few proper paintings with accompanying size diagrams and maps. I chose to add a slanted spidrid to the introductory page showing the variety of shapes spidrid bodies can take. I do that more often: designing various shapes is fun, and it nicely illustrates adaptive radiation. It also allows me to paint various colours and different surface textures.

Click to enlarge; copyright Gert van Dijk
Here it is. It is just a fragment of the original 4200x6000 pixel illustration, and is just meant to give you a taste, not to satisfy your appetite! As you can see, I chose to go with the shiny texture of the sally lightfoot, as well as its riotous colours.  The text introduces it as follows:

"Mad Sickle
This species represents a major spidrid clade. While ‘square spidrids’ move their legs in a vertical plane, the ‘slanted spidrids’ do not: the basic leg joints have tilted. The most likely reason for this is that the flexion and extension muscles can now more easily help with propulsion. Most ‘slanties’ are very flat and live in crevasses. There are clockwise and anticlockwise slanties; the direction is inherited, so each species has its own exclusive direction. It seems that the two types of slanties arose completely indepedently, so ‘clocko's’ and ‘antics’ are not at all related. The mad sickle is very agile. Please do not try to catch one: you disturb them, you are not likely to succeed, but if you should, it will pinch you very forcefully. 
Name Sicilicula insana; Sicilicula (L.): little sickle; insanus (L.): frenzied, maddening"

Wednesday, 16 August 2017

Flying animals or true 'weight lifting'

In response to a question on the Speculative Evolution website I thought it might be useful to write a short post on animal flight, with an eye on other worlds besides Earth. It will turn out that the logic is very similar to that of leg design. That subject, focussing on bone thickness, was discussed in two earlier posts, here and here. There is some math involved, but nothing more complicated than understanding powers and roots.

This post will only deal with the most basic aspect of flight, which is staying aloft. Let's start by considering an animal that is in stable flight. This means that is neither losing nor gaining height, with some kind of propulsion we will ignore (the same reasoning will also hold when the animal stably glides downwards, so lift is a bit less than weight). When the animal says aloft without sinking two forces must be equal in size: gravity pulls the animal down and lift pulls it up. We need to take a closer look at each. First, weight; it is the force induced on a body by gravity:

   weight = gravity constant (g) * body mass (m),

Click to enlarge; copyright Gert van Dijk

The image above shows several views of a general avian of the genus 'Avidisneius'. We will deal with the size of the animal's body; the wing will come later. For that we need to understand that its mass equals the product of its density and its volume. We will not alter density at all but will play with the volume. Volume is determined by its length, height and width. If this sounds as if the animal is shaped like a rectangular brick, that is essentially correct. But a more complex shape than a brick does not alter the principle that its volume depends on the product of its length, width and height; there will just be various constant factors thrown in, that we ignore. All three are measurements of length that we can label as 'L'. Volume thus equals L* L* L, or L to the third power: L^3. Weight was g*m, and we now replace 'm' with L^3:

    weight =  g * density * L^3.

Now we can go on to lift. Textbooks will tell you that it depends on a fairly simply equation:

  lift = rho * area * v^2.

Rho is the density of air.  'Area' is the wing area as seen from above, and 'v^2' is the square of the velocity of the animal with respect to the air. What this tells us is that there are three ways to get more lift. Obviously we cannot change the first, atmospheric density, but the equation tells us that an atmosphere with double the density doubles lift. Halve that density and you get half the lift, which is bad news for animals trying to fly on planets such as Mars. We can and will play with wing area: double the wing area and you obtain double the lift. The real winner here is velocity: doubling velocity gives four times the lift, because the formula contains velocity squared.

Of course, a wing can also be described by length and width and height. We will not use 'L' here but 'W' to specify that we are dealing with the wing. The mass of the wing will be W^3, but its area is proportional to W^2. So the equation for lift becomes:

  lift = rho * W^2 * v^2.

Click to enlarge; copyright Gert van Dijk

The two equations for weight and lift are all we need, for now. Let's take 'Avidisneius' and either double or treble its size as in the image above. To get the new forms, we replace 'L' in the weight equation with '2L' or '3L'. The volume becomes (2L)^3 or (3L)^3, giving us 8*L^3 and 27*L^3. The mass and weight change linearly with volume, so weight will increase by a factor of 8 or 27.

Unfortunately, this 'simple scaling' disturbs the balance between weight and lift. Why? Remember that lift depends on area, and hence on W^2. So if we double or treble W just as we did for L, we get new wing areas of (2W)^2 and (3W)^2, or 4*W^2 and 9*W^2. These wings, even though they are larger, are too small to hold the larger weight up. It's because of that infernal third power for weight versus the square for lift. (As an aside, the usual expression for 'scaling every dimension by the same amount' is 'geometrically similar'.)
Click to enlarge; copyright Gert van Dijk
Alas, the wings will have to be made even bigger. The image above shows the results, first for the previous 'simple' scaling and for a 'corrected' scaling attempt. We have seen that doubling body size (L=2) will make weight increase 8 times. What we therefore need is a new wing with 8 times the area. Similarly, if we make the body three times larger (L=3) then the new wing area must be 27 times the original one. We can find out how much we need to change the wing dimension 'W': area was the square of W, so to find the new 'W' we take the square root of 8 and of 27: the numbers are 2.82 and 5.20 respectively. So, if the body dimension (L) is to be 2 times bigger, the wing dimension (W) has to become 2.82 times bigger, and if the body becomes 3 times larger, the wing has to become 5.2 times larger.
Is everything solved now? Alas again... The additional increase in wing generates just the right amount of lift to compensate for the larger body. But the wing itself will also become heavier. Remember that volume corresponds to length to the third power? If our new wing dimension W is 2.82 times the original, the new wing mass will be 2.82^3 larger than the original, or 22.43 as much! This is not funny anymore. For the animal that became 3 times larger, the wing dimension W had to become 5.2 instead of 3, meaning the new wing volume is 140 times the original one, even though the body became only 27 times heavier. The 'corrected' scaling definitely falls short...

There is no escape from these cubic effects. Here is another way to look at its devastating effects. Suppose that the mass of the wing was originally about 20% of the mass of the animal. For an original Avidisneius of 500g in total, the wing would have a mass of 100g and all the rest has a mass of 400g. Let's take the animal we made three times larger using the 'corrected' scaling: the new mass of the body will be 27*400g, or 10,800g. The wing mass of 100g becomes 140*100g, or 14,000g. So our original 0.5 kg beastie now weighs 24.8 kg, and a staggering 56% of it is now wing. That's good if you like wing meat, and the animal should be easy to catch: can its heart and lungs even keep up with these massive wings? Mind you, in reality the bones and muscles themselves also need to increase by additional amounts, as their strengths depend on diameters (for examples see the posts mentioned above or my discussion of the giants in Game of Thrones here). 

The lesson is that, if you increase a flying animal's size, the wing dimension must increase more than the body. This actually happens in nature: larger birds have relatively larger wings. But there is no escape from the merciless differences caused by weight depending on cubic effects and lift, while bone and muscle strength depend on cross-sectional areas. At some size, the only weight that the wing can lift is that of the wing itself! But long before that point is reached, the construct will no longer be a viable animal. It is difficult to say where the 'Limit of Flight Plausibility' lies. On Earth now, kori bustards are arguably the largest flying birds. They weigh up to 18 kg, with a 275 cm wingspan. But extinct birds may have weighed 40 kg or even 72 kg. Did pterosaurs really weigh up to 250 kg? There is room for speculation here (which convinces me that Furaha needs some gargantuan beasts in the sky). However, please do not just geometrically enlarge a sparrow and present it as a 250 kg avian: approaching the Limit calls for profound changes in anatomy and flight efficiency.      

Other planets

The lessons for other planets are not very complicated: if you increase gravity by a certain amount, you increase weight by the same amount. If you transplant an Earth-like flying animal to a heavy world, you should make certain that lift increases by the same amount. Enlarging the wings will do that, but, because of the heavier wing, you should trim off a considerable amount of weight wherever you can. You could also make your animal fly faster, but do not think that that solves everything: your animal must be able to fly at low speeds to start and stop. You could evolve the propulsion system in such a way that it provides additional lift.

A high atmospheric density is a luxury, in contrast: if you double density, you can get away with half the wing area, which means that 'W' need only be 0.7 of what it would be on Earth. The soupier the air is, the more you can dream of avians with short stubby wings, resembling flying penguins.
But could you have something as large as a 'Game of Thrones' dragon flying around on a planet with an apparently Earth-like gravity and atmosphere? Of course not. Don't be silly. Dragons fly through magic. Birds don't.          

Sunday, 28 May 2017

Mr Masato's CGI creatures

Well before I cut down on blogging altogether, I had stopped writing about other people's projects regarding life on other planets. I did so more often when I first started blogging in April 2008, but then it was difficult to find anything about speculative biology. The 'speculative evolution' website that now caters for such needs probably started at more or less the same time (it says that I became its 42nd member on July 21, 2008). But in the following years the field grew, so I thought everyone would be able to find interesting work for themselves.

I will make an exception now, as I miss blogging. The main reason I chose to present the work of Mr Masato here is that it seems to have gone unnoticed, perhaps because it is shown on a Japanese website only, as far as I know.

His work can be found here. Oddly, that page will not take you to his speculative biology images; that is found here, or, without further clicking, here. You will find 30 images there, showing a love of strong colours, a fondness of cuteness that may be particularly Japanese, and a wide variety of forms, some odd, some less so. Mr Masato told me that there is no underlying story and that the images may well be from different planets.   

Speculative biology of the 'alien world' type is not his major interest. That is dinosaur work, as the other pages on his site show (I liked the page on Gallery 4 where he places CGI dinosaurs in Japanese street scenes). Mr Masata is one those artists who rely heavily on computer-generated images to produce his art. That approach has many advantages, such as that it is easy to take another view of a scene from a different angle, or change the lighting, etc. Once all such decisions are made, you set the programme to 'render', have some coffee, and there's the image. For some of the best work done along such lines, I recommend the book 'Dinosaur Art' (there will be a second volume too). But it is very difficult to get photorealistic CGI work to look convincing, oddly enough. Often there is something unnatural or even sterile about the placing of plants; the surface of water looks like it is made of jelly or of glass, rocks look like sponges, etc. Among the few people who can really pull it off is Marc Boulay, whose work I discussed more than once in this blog (for instance here and here). I personally do use CGI techniques, but only as scaffolding for a painting. Here is an example.

Click to enlarge; copyright Masato Hattori
Anyway, on to Mr Masato's work. I picked out three paintings. The first one is this odd head sticking out above the surface of the water. Well, I assume it is a head and not the entire animal. The hair is well done, in particular for CGI work, and the image as a whole is nicely mysterious. Notice the lack of background. In essence it's just the beast, but that scarce approach works well here.

Click to enlarge; copyright Masato Hattori
These 'armoured marmots' are rather cute, with their spectacular headdress. In my own creatures I often reduce the extravagance of such elements after the first sketch, but having looked at these daring shapes I should probably do the opposite once in a while. The rocks are interesting here; I think I can identify the texture from Vue Infinite that was used to make them. 

Click to enlarge; copyright Masato Hattori
I like this one because it is so full. It can be chore filling up a scene in a programme such as Vue Infinite, even though it has an 'ecosystem' features to help with that. There variety of plants helps top create a convincing scene. The tetrapod has very interesting rainbow colours, suggesting iridescence. The young animal again adds a cute element to the scene. The tusks worry me a bit: they look very slender, so they could break easily. With such a long neck the animal would have little need for them. The animal approaching the tetrapod seems to behave like a crocodile, slowly making its way towards its potential prey. The bony head with all those bumps reminded me of an uintathere. The best feature of this image are the wildly coloured blue flying thingies. Are they just there by coincidence, or do they have some relation with the 'uintacroc'? I like images that tell a story.