Tetrapod Zoology

Squamozoic sneak-peek # 2

When unable to find time to do anything else, resort to posting Squamozoic sneak-peeks (previous example here)…

i-b3beca6a7962da9d899c90d05f39b2bc-Squamozoic-riverbank-ambush-color-May-2011.jpg

This scene – ‘Riverbank ambush’ – features a giant macro-predatory amphisbaenian and some surprised gekkotans. Colouring by Tim Morris. Feel free to discuss among yourself. Kinda busy right now…

Comments

  1. #1 Andrea cau
    May 27, 2011

    The amphisbaenian is a _Graboidus tremorensis_, I suppose.

  2. #2 C. M. Kosemen
    May 27, 2011

    Great image! But how energetically feasible would a large-bodied “lurking” hunter be? Wouldn’t it be too hard to support such a body size on such a lifestyle? Perhaps if there was a specific biotope with loose/muddy soil and an abundance of prey… But in this case, such animals would be vulnerable to sudden changes in conditions…

  3. #3 heteromeles
    May 27, 2011

    Um yeah, what they said. ‘Sides, what’s a burrowing animal doing without a way to close its mouth against the dirt, even if it could move that way?

    I’d also point out that gekkotans have so much limb and digital diversity that you could probably have them evolve hoofs, and it would still be realistic.

  4. #4 DMA
    May 27, 2011

    Are any of these animals endothermic? After all, many marine reptiles seemed to have evolved some sort of high metabolism. It would also explain why mammals and birds never became the dominate land animals. Will these really have to wait until April, 2012.

  5. #5 Darren Naish
    May 27, 2011

    Graboidus (I’m going with it) isn’t bigger than the biggest snake we know of, and who’s to say how mobile it was? It clearly gets by just fine (frequenting softer substrates where burrowing is not physiologically inhibitive). As for “closing its mouth against the dirt”, it’s just a souped-up version of real-world amphisbaenians like Anops, and they manage fine.

  6. #6 heteromeles
    May 27, 2011

    Now you’ve got me giggling. Of course, the softer the substrate is, the less it holds up under burrowing, and the biggest sand swimmers aren’t very long.

    Besides, it’s not that soft a substrate, since you’ve shown it with turf on top.

    Unless of course, that’s *not* turf. Grass only became common 40 mya or so. Giant moss mats?

  7. #7 birger johansson
    May 27, 2011

    Graboidus could do without burrowing if it was made of metamaterials bending light around its body, like the Predator but without the tech.

    Or maybe it only needs to clear the head, spitting venom far away. Anyway, I suspect it would need some kind of hibernation or daily torpor to wait for a prey to get close enough without starving.

  8. #8 Patrick
    May 27, 2011

    #6: Maybe it’s Isoëtes.

  9. #9 heteromeles
    May 27, 2011

    Since Isoëtes is aquatic, I’m not really buying that. It could be a dwarf lepidodendron though. Maybe. Lycopod would be better. In any case, moss does form mats of that type, so that would be my first guess, absent other evidence.

    Nice deal with the umlauts by the way. How’d you do that?

  10. #10 DMA
    May 27, 2011

    This reminds me of the different burrowing creatures from primeval. I don’t think you could really have something over a few feet moving efficiently through the ground, and this looks bigger than a few feet.

  11. #11 Sigmund Nastrazzurro
    May 27, 2011

    Nice! Beyond a certain point ‘swimming’ through sand or soil becomes very difficult, as discussed elsewhere (http://planetfuraha.blogspot.com/2011/03/swimming-in-sand-iii-real-and-robotic.html)

    Your amphisbaenids may perhaps pull it off though.

    (On another note; “C.M. Kosemen”: would that be Mehmet Kösemen?)

  12. #12 Marcus Good
    May 27, 2011

    DMA – “I don’t think you could really have something over a few feet moving efficiently through the ground”.

    I’m sure Darren will be able to correct me if I’m wrong here, but I seem to recall there being evidence for burrowing in _Phascolonus gigas_ (not as much as in modern vombatids, though) and they were up to six foot long..

  13. #13 heteromeles
    May 27, 2011

    Heck, don’t warthogs dig burrows with their noses?

    The problem is the swimming and ambush part on a presumably legless lizard. The biggest sand swimmers are on order of 0.5-1 m in length.

    Personally, I’d find it more believable if it was a pack-hunting varanid. Or the large paleophid equivalent of a seal. Or an overgrown Schlegel’s blind snake. Just saying…

  14. #14 DMA
    May 27, 2011

    Marcus Good, I don,t doubt that larger creatures can burrow, I just don’t think such a large animal could tunnel, or “swim” through sand like smaller amphisbaens do. On the first squamozoic teaser, Darren mentioned it having a 30 cm skull, making it about 20 ft. Such a large creature would have difficulty moving on land let alone tunneling underground.

  15. #15 Mike from Ottawa
    May 27, 2011

    Fans of the whimsical and wise tetrapodal stylings of our host, the most estimable Mr Naish, might be interested in nominating their favourite TetZoo post in the past year for the 3QuarksDaily science prize at:

    http://www.3quarksdaily.com/3quarksdaily/2011/05/lisa-randall-to-judge-3rd-annual-3qd-science-prize.html

    I’ve nominated the Kentrosaurus thagomizer post http://scienceblogs.com/tetrapodzoology/2011/01/heinrichs_digital_kentrosaurus.php .

  16. #16 Wilbert Friesen
    May 28, 2011

    Ik could be a lurker which burrows into a hole or under loose soil en plant debris, invisible for it’s prey and wait untill an unsuspected prey is within sight. This kind of ambush technique can produce large snakes

  17. #17 Patrick
    May 28, 2011

    heteromeles: Well, not all Isoëtes are strictly aquatic, and some can grow just on rather wet ground. And a good thick patch of them does look amazingly like grass turf. I suppose these would have to be rather large geckos for Isoëtes too be that small in comparison, though. So, OK, maybe a moss.

    As for the umlauts, I just type them as I would in other contexts (“alt”+”u” then “e”, in OS-X), and they show up fine. HTML codes apparently work here, too; “ë” is “&euml”.

  18. #18 Patrick
    May 28, 2011

    Also, for some random trivia quite distantly related to the putative topic, the “¨” here is not an umlaut, but a trema (apparently a context-neutral term for the two dots, or so says wikipedia) being used to indicate diaeresis (i.e., that the vowels are pronounced separately rather than as a diphthong), as in old-school spellings of words like “coördinate”, “naïve” (which I guess is the proper French spelling, but not typically used in English), etc. It pops up in other genera as well (“Laënnecia“, “Kalanchoë“).

    Of course, maybe you already knew all that. Anyways…

  19. #19 Darren Naish
    May 28, 2011

    In the end, it’s just a nice picture, and not a depiction of anything real. But why couldn’t a hypothetical giant burrower construct tunnels in soft substrate, bursting through a close-to-surface excavation when prey are detected? All kinds of animals construct (often large) tunnels in soil.

  20. #20 DMA
    May 28, 2011

    Perhaps it could ambush prey from tunnels, though even that might be difficult. I just don’t see it as being able to swim through sand like smaller amphisbaeans do. I think an aquatic amphisbaean might be more realistic.

  21. #21 Birger Johansson
    May 28, 2011

    You miss the point! It can swim through a soft substrate, but by mixing clay with its saliva it gets a strong material it can use for construction (like the Alien), for instance, for lining more durable tunnels. It could even build larger nests for a social group of related individuals, like badgers do.
    The gekkotans clearly need more natural defences. Posonous spikes?

  22. #22 Jerzy
    May 28, 2011

    You forgot laser eyes. How else it would anihillate earth during digging?

    Burrowing animals compact earth to the sides to open the tunnel. For a large animal, this is impossible.

    BTW, chanced on a marvellous French film in TV showing mole digging underground live in X-ray.

  23. #23 D. Valentine
    May 28, 2011

    Did Darren ever say it was a “swimmer”? Maybe it’s just a scaly trapdoor spider. We also don’t know what the scale is: just because there’s a 20-foot creature in Peek #1, doesn’t mean these things are over one-foot.

  24. #24 DMA
    May 28, 2011

    Valentine, the whole squamozoic idea is that reptiles evolved into the cenozoic megafauna. It even says macro-predator at the top. Besides, it’s way to robust to be only 1 ft in length.

  25. #25 Anonymous
    May 28, 2011

    There are serious, serious biomechanical issues with making a head-first burrowing animal that large. Laduke et al. 2010 mentions some of these problems. Essentially, most burrowing limbless reptiles and amphibians are less than a meter long, and all are less than 2.5 cm in diameter. The authors suggest that this is because the force required to push substrate away from the head goes up exponentially.

    It doesn’t appear as though this is as much of a problem for animals with limbs. It has been suggested that the mylodontid ground sloths burrowed, and aardvarks seem to be able to burrow with little issue. Perhaps the giant amphisbaenid could be related to Bipes, though I don’t know if that would cause any other biomechanical problems.

  26. #26 DMA
    May 28, 2011

    Wow. I’m commenting a lot on this post. Technically it might be able to ambush prey from large tunnels, like a big trapdoor spider does. I just don’t see how it could make a big tunnel with it’s jaws, or even ( if it has any) tiny front legs. The animal is just to large.

  27. #27 Anonymous
    May 28, 2011

    The “scaly trap-door” spider approach could work, but it would still have to dig the trap-door chamber in the first place. Though if it did do this the irregular frequency of prey would suggest it is not endothermic, even if other megafaunal squamates are.

  28. #28 kamion
    May 29, 2011

    A trap-door spider construction might work; Nile Crocodiles are known to dig deep burrows to survive the dry season and those are pretty big. there is a relict population in the west of Africa that hibernates through the drought season this way.
    this kind of animal could have started out the same way; digging a hibernation hole and at some stage got activated by passing prey that either fell through the not that solid roof or it broke the roof itself by coïncidence. those that had the tendensy to have thin roofs evolved to this type of hiding predators, particulary in area’s where the water did not return with the seasons.

  29. #29 David Marjanović
    May 29, 2011

    Trying to reconstruct my comment from yesterday…

    Part 1 didn’t get through, here’s part 2:

    HTML codes apparently work here, too; “ë” is “&euml”.

    Of course it’s not. It’s ë. There are browsers that repair such broken HTML by adding the missing semicolon and displaying the code as intended, but neither IE nor Firefox do that.

  30. #30 David Marjanović
    May 29, 2011

    I can’t find the problem. Part 1a:

    As for the umlauts, I just type them as I would in other contexts (“alt”+”u” then “e”, in OS-X), and they show up fine.

    No such thing works on a Windows keyboard (except on French, Swiss and AFAIK Spanish layouts). Windows never had a good keyboard driver.

  31. #31 David Marjanović
    May 29, 2011

    Part 1b, with HTML entities removed…

    The Windows character map is a bit hidden: All Programs — Accessories — System Programs — Character Map. You can copy and paste from there. I use it so often that it’s always on top of the list of recently used programs.

  32. #32 David Marjanović
    May 29, 2011

    Apparently there’s a limit on the number of HTML entities per comment.

  33. #33 DMA
    May 29, 2011

    Kamion, Nile crocodiles have legs. This creature would have to dig with it’s mouth. Most amphisbaens are legless. Those with legs have only two stumpy ones in the front.

  34. #34 C. M. Kosemen
    May 29, 2011

    BTW, the skull of Graboidus bears more than a passing resemblance to the skulls of extinct sperm whales.

    Personally, the only way I can see something like this functioning is as a non-burrowing, “anaconda/alligator” type of swimmer on the pampas (with eyes, of course…)

    There could be smaller “trapdoor amphisbaenians” that habitually lurk in leaf litter or burrow in soil, (perhaps even with enlarged shield-heads that block the entrances to their burrows,) but IMHO, nothing of this size range.

  35. #35 John Scanlon, FCD
    May 29, 2011

    Trying again, sorry if this double-posts:

    It could even build larger nests for a social group of related individuals, like badgers Great Desert Skinks Liopholis kintorei do.

    Since we’re doing squamates…

    And I see someone already cited LaDuke et al. (2010) on size limits for head-first burrowing, so I don’t have to self-promote (anyway, that bit was Nate Kley’s IIRC). Not exponential but proportional to cross-sectional area (i.e diameter squared), I think.

  36. #36 Darren Naish
    May 29, 2011

    Thanks to all for an enjoyable discussion. Given that this was all inspired by a totally hypothetical organism, I can cheat and just say that Graboidus has a load of adaptations you haven’t accounted for (it has big, clawed limbs, for example, as well as lasers and afterburners). Anyway, I think we all learnt a lot. There does appear to be a constraint on the maximum size of limbless burrowing animals. So, dammit, no Minhocão! As for real burrowing, limbless squamates, check out the next article…

  37. #37 gray Stanback
    May 29, 2011

    Is there a squamozoic website, or somewhere I could go to see the project in its current state?

  38. #38 heteromeles
    May 29, 2011

    I guess this also nails the coffin on Dune sandworms too. So sad.

  39. #39 Anonymous
    May 29, 2011

    @John Scanlon

    Yes, it was proportional to cross-sectional area of the head. I just had a brain fart and said the wrong word.

    A large, limbed Graboidus does sound interesting. It kind of reminds me of the lindwurm and tatzelwurm of European mythology.

  40. #40 Patrick
    May 29, 2011

    David Marjanović:
    “Of course it’s not. It’s ë. There are browsers that repair such broken HTML by adding the missing semicolon and displaying the code as intended, but neither IE nor Firefox do that.”

    If you type “&euml” into the comment box, guess what shows up? Yup, “ë”. :-) But you’re right, I forgot the semicolon; “&euml” only works in isolation, not within a word. Oh well.