Saturday 22 January 2011

It's a 'Fish'!

One of my good intentions for this year was to cut back on blogging. I did have my doubts whether this was really a good idea, as I like writing. Still, blogging keeps me from painting, and I had been postponing that for too long. I had decided to switch from brushes and artists' oils to digital painting about a year ago, but my first attempts proved a shock: I was used to applying paint where I saw the tip of the brush, and now there was a large distance between the graphics tablet and the screen. There were other mishaps as well. Even after changing Photoshop for Painter (more on that here) I still procrastinated, until I put aside enough time to really play with the brushes. Once I managed to forget what I was doing, my visual and motor skills, such as they are, met again and renewed their friendship. To make a long story short, here is my first digital painting I feel I can show the outside world. It's a fish. Sort of.

Click to enlarge; copyright Gert van Dijk

To be more precise, it is a Fusus rostrauctus of the Clade Fishes IV (Proculcapiti). I may have to check naming conventions here though. Anyway, I revealed a glimpse of Fish evolution previously, which I will not repeat. You may observe the typical traits of the Clade, but I will focus on artistic matters here (just as well, as there were some sudden changes in their anatomy compared to the rough sketch in the earlier post!). Having done a fairly large number of full paintings in oils for the eventual Book, I felt I needed additional illustrations, highlighting individual species, cladograms, things like that. This is the first of those. I wished to keep the painting style more or less the same as that of my previous oil paintings, and think I managed. After messing about with Painter's very large assortment of brushes, I settled on just two, and used those throughout (for those in the know, I used a detail oil brush and a blender, but tweaked size, opacity, 'resaturation' and 'bleed' continuously).

Just for fun I will show some layers of the final painting. The nice thing with digital painting is that you can use layers of colour that stay separate, so you can go back to a deep layer even after you painted others over it. In a 'real' painting ('physical' painting?) the only way to correct a deep layer is to scrape it, and everything on top of it, away altogether.

Click to enlarge; copyright Gert van Dijk

So here is the start of my project (it's not a tutorial: I'm not good enough for that). I started with a rough sketch and simply changed lines and shapes until the concept became more or less ready; that is the image on the left. I then drew a much neater line drawing on another layer, and used that as a guide for the painting job: the one on the right. In old times, I would have done exactly the same, but using various sheets of paper for the sketches on the left and one sheet of transparent paper for the one on the right.

Click to enlarge; copyright Gert van Dijk

After that you start painting. In this case I chose flat colours to start with. With oils, this basic colour layer would have obscured the line drawing on the board. Digitally, things are different: you can paint underneath your sketch, so that stays visible. Very odd at first, but extremely useful. The base colours are on the left, but without the line drawing. After that, another layer was added (on the right), and that is where it becomes interesting: that one modifies the base colours with shadows and highlights, as well as with some subtler colour changes here and there.

Click to enlarge; copyright Gert van Dijk

After that I decided to add another colour layer (I should have done that before, but, as I said, I am new at this). The rest comprises adding some reflections, details, some final shadows etc., and there we are. Mind you, the original is almost 7 times bigger, so some detail is lost. Anyway, here's my first digital painting. I hope you like it.

Saturday 8 January 2011

Birds with clubs and other smashers: clavigerism

I intended to write just one blog entry every two weeks this year, and am already breaking that rule. I could not resist, after reading a paper on an extinct Terran bird. The similarities to some Furahan creatures were simply too interesting to leave it alone, so there you are.

The bird, a flightless ibis, was described in a paper entitled 'The bizarre wing of the Jamaican flightless ibis Xenicibis xympithecus : a unique vertebrate adaptation' (Longrich NT, Olson SL; Proc R Soc B 2011, online 5 January 2011).

Click to enlarge; Longrich NT, Olson SL; Proc R Soc B 2011, online 5 January 2011

And here you see a reconstruction of the bird (top) and a comparison of its wing bones (bottom) with that of a still living ibis species. The authors make a case that the bird was flightless, and go on to say that the wing bones are odd for flightless birds. That holds for the hand in particular, with its thick and curved bone. The authors think it functioned as a club, and provide various anatomical reasons why they think so. After that, they discuss the club some more:
"We therefore propose that the wing of Xenicibis functioned as a club or flail. Several features of the limb would have facilitated this function. Kinetic energy is the product of mass and velocity squared; accordingly, weapons such as clubs and flails have a long handle to increase the angular velocity of the club, and are heavily weighted to increase the mass accelerated by the swing, and the centre of mass is near the end of the club, where the angular velocity is highest. Precisely this design is seen in the hand of Xenicibis, where the end of the wing is massive, and the proximal metacarpus and long forelimb could act as a handle. "

The authors of the paper also compare this odd ibis design with the front legs of mantis shrimps (Stomatopods), that function in a similar manner. The video above shows a slowed down version of a strike, and incidentally allows the shape of the club to be appreciated as well. It is taken from the lab of Sheila Patek, whose work on the biomechanics of their legs featured in this blog previously.

Click to enlarge; copyright Gert van Dijk

A long time ago mantis shrimps were the inspiration for Furahan neocarrnivores. You will find more material on them on the Furaha site (go to the land page). One of them is shown here (one of its commoner names is 'pugile'). Compare its front legs to those of mantis shrimps and to the ibis; I think that the ibis still had a long way to go before its clubs measured up to those of other club bearers. Then again, they were probably meant to hit other ibises, not kill prey animals, and it might not be advantageous in the long run to kill fellow ibises; merely sending them off might be good enough.

Stomatopods, Xenicibis and Furahan neocarnovores may all be said to have developed their clubs from what originally were locomotor limbs. In the Stomatopod and Neocarnivore cases, the limbs in question were used to walk with, and in the Xenicibis case its ancestors used them to fly with. In all cases their freedom from locomotion opened the door for a new function, and interestingly the new function was a weapon in all three cases. I think that Xenicibis therefore qualifies as much as the other two as an example of 'centaurism' (more on centaurism here and here).

I am delighted that we now have an example of 'raptorial centaurism' concerning a fairly large animal on Earth. Both Stomatopods and Furahan Neocarnivores have evolved various kinds of front legs, functioning as different types of weapons: there are 'smashers' and 'spearers' in both cases (Neocarnivores have webs or basket-like thingies as well). It would be great if more diligent paleontological work would uncover a 'spearer' on Earth as well, but I will not hold my breath. Meanwhile, perhaps it is time to coin a phrase to start differentiating between the various kinds of weapons limbs may turn into. 'Smashers' sounds good, but is limited to English, and that won't do. Luckily we still have Latin. A 'claviger' is an existing word for club carrier, with the plural 'clavigeri'. Turning it into a principle would result in 'clavigerism'. I don't expect a follow-up paper on Xenicibis to use the word; then again, the authors used the interesting phrase 'volant species' for birds that actually fly, so perhaps they can appreciate a bit of biogeekery...

Monday 3 January 2011

Nereus (or how you can have radial flight with an odd number of wings)

As regular readers know, I am always on the lookout for creative projects concerning speculative biology. On places like Deviant Art you will find many interesting alien or alternate animals. Some feature new traits, others rework well-known themes; some are professionally drawn, others are less so. But what interests me most if there is a background: are there biotopes, is there a food web, do the predators match the prey, etc. That shortens the list considerably.

Some large projects have been in existence for very long times, and it does not feel entirely right to discuss them here. But there is one project, Nereus, that is relatively new. Its creator, Evan Black, does not mind, so that helps. Apparently Nereus received its name because humans first thought it was a water world (Nereus is a being from Greek mythology). The earliest post on the Nereus project on the Speculative Biology forum dates from May 2009. Evan has already produced 100 species and aims to achieve no less than 200 species. That is a lot or work: creatures have to be designed and described, and also drawn. I like the way Evan draws animals: while a bit stylised, they are very energetic, and as design they work: what you see are lively animals.

Click to enlarge (VERY much so!) Copyright Evan Black

Here is a start: a rather large cladogram of current Nereid species. Don't be surprised to find that the one on Evan's site differs from the one here, because he might have added a new species by the time you go there...

The Speculative Evolution pages contain discussions and comments on how Nereus develops, but I much prefer to see the result on Evan's own site. There, you can work your way through the menu, clicking on the Latin names of the various groups until you get to individual species, but you do not see what you are aiming for until you get to the species pages. Once there each species has two pages: one with text and a thumbnail, which leads to a much larger image with additional text. But there is another way to browse Nereus that I much prefer, and that is to choose 'world', and then 'cartography and climates'. That will take you to a list of 7 biomes, and clicking on them rewards you with an overview of that biome and small images of the species in it, that you can then pick and read at will.

Click to enlarge. Copyright Evan Black

As an example, here is the 'Sog Basin'. Sog "carpets the landscape like a thick tangle of spongy red veins", which sounds a bit like Well's Martian weeds. Luckily, there are no intelligent aliens around to regard Earth with envious eyes (or not yet). Sog sucks up water from the few available sources, and transports it across the otherwise dry biome. Leaks in the sog create watering holes, on which many species depend. Now that is why I prefer creations with a background: you immediately start to think how that works, how such species might look, etc.

Click to enlarge. Copyright Evan Black

Here is one such species: the kappa (Nothorana pratensis). It is a predator lying in wait in sog ponds, with just its dorsal eyes and its nostrils above the water. Take a good look: the kappa has three legs: two paired front ones and one unpaired jumping leg in the back. The illustration also contains a classification list containing the familiar Linnaean scheme, which starts at the species level and goes all the way up to the phylum Tetrabrachia (that would be 'four arms', if I remember my Greek correctly). One of the nicest things about Nereus creations is that it all fits together. Look up the Tetrabrachia, and you will find a page devoted to their anatomical Bauplan.

Click to enlarge. Copyright Evan Black

And here it is. The four arms in question concern four major nerve trunks emerging from the central brain. One trunks goes upwards, and that one deals mostly with sensory functions, which in modern Tetrabrachia has caused them to develop a head. The other three trunks control movement. In effect, what we are seeing here are radially organised animals, and I like the idea of taking radial animals rather further than they have managed to do on Earth (see the discussion on tetropters here, here, here and you can more on tetropters yourselves; here is something about radial symmetry; if that is not enough, just search for spidrids on this blog). But the kappa does not show radial symmetry; it is blatantly bilaterally symmetrical, and the legend includes information just when that happened.

Click to enlarge. Copyright Evan Black

I cannot resist showing one particular specimen, and that is because Evan and I discussed its s flight mode. Again, this is a radial life form. Most flying forms on Nereus are bilaterally symmetrical, resulting in flight plans that are superficially similar to the ones on earth. Not so the Cliff Whistler (Cadosmilos Aetopsis).

As you can see, it flies a bit like my tetropters. The tetropter discussions may have helped inspire the Cliff Whistler, which is flattering. Anyway, the Whistler flies by beating its three wings horizontally to and fro. Diehards out there may remember that I made extensive use of the 'clap-and-fling' principle to explain tetropter flight. The 'clap' involves two wings beating against one another at the end of their movement, then sweeping back to the other end of their range, where they then clap against another wing. Etcetera. That works with two wings (Terran insects and some birds), four wings (Furahan tetropters) and would work with more wings too, although no-one has yet invented any of those yet as far as I know. Besides offering increased lift through 'clap-and-fling', an even number of radial wings neatly solves the problem of torque: if a wing moves clockwise it pushes the body counter clockwise, which is useless. With two or four wings these forces even out.

Three-winged radial flyers run into problems. There is no clap-and-fling mechanism, and the wings move in unison: all three clockwise, and then all three counter clockwise. That leaves torque to be solved. Well, evolution, in the form of Evan, designed an adaptation of the Whistler's mouth parts at its bottom: these evolved into winglets beating in the opposite directions of the main wings, countering to a degree. Enough for the Cliff whistler to be a viable organism, or so Evan and I thought.

Recently I came up with a way to have a clap-and-fling mechanism with just three wings though. It would increase lift but introduce some new problems. Again, Evan and I thought that it might work, but not necessarily better than the Cliff Whistler approach. Perhaps one species will emerge on Nereus with this particular mechanism, we would have to ask Evan. I am not going to tell you how it works, merely that it can be done: each of the wings A, B and C claps against another wing on the extreme ends of its movement range. I wonder if anyone will take the bait...