Following this link will bring you to an Amazon page showing a book of extinct animals. I think it is a safe guess that most people interested in speculative biology will also like palaeontology. If so, the cover of this book should convince you that Mr. Kawasaki knows his business, and seems to prefer the bizarre. He does not shy away from speculative biology either, and in his case that concerns life in the future on Earth. He has a very nice website showing life on Earth in various geological ages, starting at the Cambrium. Clicking on an epoch shows a world map for that age, and selecting a continent or sea opens a page with its inhabitants. From the Cambrium on each major era has its own map. There are four such pages for the future, resulting in pages for 5, 50, 100 and 200 million years in the future. But before you zoom off to look there, stop at the other ages as well, because here and there you will find animals indicated with an outline and a question mark, and these are quite interesting.
Click to enlarge; copyright Satoshi KawasakiIn the present era, I found this intriguing dog with a human face living in Japan and China. The text says that the animal is not suffering at all, but that this is its normal face; at least I think that is what it says. The garbled translation suggests that the original text might be quite funny, but that is something I can only guess at. At any rate, images such as this one show that Mr. Kawasaki has a somewhat surrealistic sense of humour, which I rather like. If you do not, be warned, because similar themes will keep cropping up. If you take speculative biology as a completely serious business, do not bother visiting his site. Of course, taking anything entitled 'speculative biology' completely serious is a bit surrealistic by itself.
I will not delve into all the animals, nor discuss in any detail how life evolves in the future. I rather liked the way how chameleons leave the trees and evolve into a range of large terrestrial animals, looking a bit like present-day mammals as well as like dinosaurs. What I also liked was that intelligent beings seem to evolve here and there, only to vanish without a trace.
Instead I will focus on the world of 200 millions years into the future, and on one theme only: land-living cephalopods! Yes, there are land-living octopus and squid here. Dougal Dixon was probably the first to shoo cephalopods onto dry land in his book 'Life after Man'. The theme was worked out in more detail in 'The Future is Wild'. I think there are some significant problems with this concept. One is that the cephalopod body structure simply does not provide a good starting point for an animal that needs to withstand gravity. Tentacles in particular are an extremely bad starting point. In earlier entries (last one here) I explained my reasons for thinking so. In short, you can walk on tentacles, but once evolution has increased their efficiency, they are no longer tentacles, but will have become legs. The second reason to think that cephalopods will have a difficult time making it on land is that they are not the first to go there, so they will have to compete with animals with fully developed legs. In 'The Future is Wild' swamps were provided for the purpose, but the other animals were not whisked away to support the cephalopods. Perhaps an isolated island, where there are no land animals at all, might do the trick. Even then you have to hope that birds won't bother the new-fangled land-squids too much. Mr Kawasaki's terrestrial cephalopods do not seem to care one bit about such sombre estimates of their likelihood, but look quite alive. Let's have a closer look.
Click to enlarge; copyright Satoshi KawasakiThis one is entitled a 'Purototerasukuido', and is described as a primitive 'Terasukuido'. Let me guess: 'sukuido' might be a Japanese transliteration of the English word 'squid', and 'terasukuido' might be 'terrestrial squid'. 'Puroto' could be 'proto-', so this might be a proto-land-squid'. The animal looks like it is lifted bodily out of 'The Future is Wild', so it seems like Mr Kawasaki is playing another joke. It is describe as a living fossil, and the statement that high fertility balances high mortality shows that Mr Kawasaki also thinks that such an animal needs all the help it can get to stay alive.
Click to enlarge; copyright Satoshi KawasakiNext: a goby squid. The text says 'Second is to leap out of the crab', which may mean that it is an ambush predator, waiting for a crab to emerge. It has six walking legs and two prehensile arms, which makes sense, I think. It somehow manages to look very attentive, indeed like a little goby fish.
Click to enlarge; copyright Satoshi KawasakiThis is a 'Sleipnir', named after Odin's eight-legged horse. The first animal shown above is a functional hexapod, using two arms for predatory purposes. Perhaps this is another example of centaurism, but that is debatable. The Sleipnir lives in herds and is well-protected by scales. Its length is given as 200-250 cm, so it is quite large. The legs might still be tentacles, but they might just as easily have bones in them; perhaps this is an example of a tentacle turned into a leg.
Click to enlarge; copyright Satoshi KawasakiAn African predator? Yes, the 'chitopasu' is a sprinter; is there a cheetah in that name? In this case, the text clearly states that there is no skeleton in its legs. What a pity. Note that the illustration is apparently not by Mr Kawasaki but by 'UME'.
Click to enlarge; copyright Satoshi KawasakiThe Zeburasukuido must be prey, and it is (I guess its name means 'zebra squid'). Note that the mouth is underneath the animal, while he eyes are on top, just like its ancestors. I do think that the eyes should probably be smaller, as eyes do not generally scale in the same way as body size. Having such large eyes makes it look much smaller than it is supposed to be. Count its legs: there are ten this time! All this leg variability suggest that land squids are not a monophyletic group; that means that the species shown here are not descended from a single species. Instead, their resemblance suggests that various groups of cephalopods all made it onto land, bringing their different body plans with them. Not impossible, but what would drive such a tendency?
Click to enlarge; copyright Satoshi Kawasaki
Finally, a brachiator (that's an animal swinging from its arms). It looks agile, as it should be. Its legs are attached to the underside of the body. If these animals indeed hang from branches much of the time, instead of sitting on them, the attachments of their legs might wander to the top of the body, making life a little easier mechanically.I really like the sense of humour that permeates these creatures. It would be nice to have Mr Kawasaki tell us a bit more about his creations, and perhaps he will respond. Until then, have fun with his website and his creations.
"Instead, their resemblance suggests that various groups of cephalopods all made it onto land, bringing their different body plans with them. Not impossible, but what would drive such a tendency?"
ReplyDeleteOr, the ancestral terrasquid had some basic body plan (perhaps similar to a more terrestrially adapted 'Purototerasukuido'), and then the body plan has changed radically as the squids radiate into different niches like cursorial runners, branchiating climbers, etc. I mean look how much variation you see in tetrapods. Compare a turtle to a snake/amphisbaenid to a bird to a gibbon to a horse. Once a particular body plan is established, there's a lot of wiggle room to alter the body's structure and occupy different niches.
Hi Anonymous,
ReplyDeleteThat might be so. I tried to look up what is known about the evolution of the number of arms/tentacles in cephalopods. Except for finding that the 'original' number is presumably ten, nothing much seems to be known about that. I had assumed that the number of legs might be fairly fixed in a specific body plan. In vertebrates, it is four, which holds for all the animals you mentioned except for the snake. But, seeing that existing gropus of cephalopods have different numbers anyway, perhaps the number is more mutable in them.
The number of limbs is pretty mutable in vertebrates too. Most of the "agnathan" fish have no fins or two fins, some of the amphisbaenids have no legs or two legs, snakes have none, whales have virtually two legs (hind legs being vestigial), most tetrapods have four, fish have a potential fifth limb in the anal fin, and acanthodians could have more than three pairs of fins. It just seems like that the lineage that lead to tetrapods somehow got locked into four limbs (or else four limbs was chosen over three or six limbs by sheer luck, and the limbs remained generally conservative in number because in general the benefits of six limbs don't outweigh the liabilities of having to mess with your development to get said limbs).
ReplyDeletePerhaps the reason why we don't really see any two-limbed vertebrates (like Dixon's wakka as opposed to the amphisbaenids of Bipedidae) is that having a pair of grabbity appendages is just too good to pass up. I mean even those bipeds that seemed to be on the way to losing their arms, like abelisaurids and tyrannosaurids, evolved from longer-armed ancestors.
If by some chance cephalopods did manage to invade land and get a toehold there, my money would be on the cuttlefish, because they have the beginnings of an endoskeleton that could be modified (albeit greatly) to support the animal's weight on land. From there, it seems likely that any land-squid would have but seven tentacles, because one of these tentacles is used in reproduction. Not only is it a good idea to protect your ability to reproduce, but internal fertilization is a big necessity for any wanna-be land colonizer (that actually wants to succeed). Perhaps four tentacles could go on to become the legs (or else four tentacles and derivatives of the side fins or something), and some of the remaining ones would either go to form tentacle-arms or trunk-like appendages. And it goes without saying that the former of these (the legs) would have some sort of bony support.
Actually, at least one two-limbed animal has evolved, that being the giant flightless bird known as the moa. in the course of evolution it lost all trace of its front limbs, including vestigial bones, as the picture in this link shows. http://upload.wikimedia.org/wikipedia/commons/0/0a/Moa_skeleton.JPG
ReplyDeleteHello Luke,
ReplyDeleteThere are more examples than just moa's: as Anonymous wrote, there are whales, snakes, legless lizards, etc.
The issue is not whether or not the number of legs is mutable -it is- but how you get there. Whales and snakes got to where they are by adaptation to very different environments. Changing the limb number was part of that adaptation. The run of the mill mammal or reptile did not need to adapt to extremely different circumstances, so its original number of limbs remained as it was.
Back to land-living cephalopods; adapting to a life on dry land would qualify as the kind of special circumstance in which changing the number of life might prove useful. You could have an octopus keep 6 arms/legs for locomotion and two for manipulation. Once that major redesign has been done, I do not think there would be much need to change the number again, provided the animals more or less keep to their lifestyle.
What I find less likely is that the number should change without any major changes in life style. Exactly what constitues 'major' remains open to discussion.
Ah, thank you for this clarification. Really though, I was only contradicting the statement that there have never been any vertebrates with only two limbs. The whole concept of limb mutability is extremely interesting, however.
ReplyDelete