There have never been enough amphisbaenians on Tet Zoo. In fact, the only time I’ve written about them at any sort of length is in the 2008 (and 2012) April Fool’s article wherein they were convincingly (cough) shown to be the true ancestors of mammals. In reality, amphisbaenians – popularly called worm lizards – are highly specialized, subterranean squamates; that is, part of the same group of diapsid reptiles as lizards and snakes. The 140 or so living amphisbaenian species inhabit the tropical Americas, western Asia, Spain, Portugal and parts of Africa. Most (but not all) are limbless; they have reduced eyes and ears, a distinctly segmented body, and often a keeled or spade-like snout. The word amphisbaenian is pronounced something like ‘am-fis-bay-nee-an’.
I think I recall saying in one of my pygopodid articles (see links below) that among the earliest of reptile images to inspire a far younger Darren Naish were the remarkable and sometimes exceptional paintings produced by Alan Male for Philip Whitfield’s 1983 book Reptiles and Amphibians, one of my favourite childhood books (Whitfield 1983). Amphisbaenians get just a single page of illustrations therein, but among the six species illustrated we see... this (below): Male’s depiction of a Somali edge snout or Angled worm lizard Agamodon anguliceps. What the hell? If you’re interested in weird, obscure animals, this is an arresting image.
Agamodon is a trogonophid, or short-headed amphisbaenian, and it really isn’t easy to find good images of it, or indeed information on it. Indeed, there aren’t that many good places to go on amphisbaenians in general: they tend to get brief coverage in herpetology books, and you need to go to more technical sources if you want to know more. I recommend in particular the several reviews produced by the great Carl Gans (Gans 1969, 1974, 2000, 2005).
Six ‘family-level’ amphisbaenian groups are presently recognized, and a very quick run-through of these groups will serve as a crash course in amphisbaenian diversity. Rhineurids, represented by Rhineura floridana from Florida, possess depressed, spade-shaped snouts and are the sister-group to remaining amphisbaenians in most studies (Conrad 2008, Vidal et al. 2008, Gauthier et al. 2012, Pyron et al. 2013). Several fossil rhineurids are known, the oldest of which (Plesiorhineura) is from the Paleocene. Bipedids – the one group that possesses limbs (and are exclusive to Mexico) – might be very closely related to blanids (Conrad 2008, Vidal et al. 2008), a group currently unique to the fringes of the Mediterranean but with fossil representatives known from the Eocene of England, France and Belgium. Cadea blanoides, a morphologically unexciting amphisbaenian from Cuba, has recently been identified as the sister-taxon to Blanus, raising interesting questions about amphisbaenian biogeography (Vidal et al. 2008). Cadea has been given its own 'family': Cadeidae.
Amphisbaenids (note: the terms ‘amphisbaenid’ and ‘amphisbaenian’ are not interchangeable) are present in both Africa and South America and include the majority of tropical amphisbaenians while trogonophids are the African and Middle Eastern short-headed amphisbaenians, all of which have formidable teeth fused to the edges of their jaws. Gauthier et al. (2012) named the amphisbaenid + trogonophid clade Afrobaenia. For a substantial review of amphisbaenian phylogeny and diversity see Kearney (2003).
The biology, behavior and functional morphology of amphisbaenians are areas of special interest and much has been written about them. All species are predatory, preying on arthropods, worms and small vertebrates. They catch animals in tunnels, often immobilising them by holding them against the side of the tunnel with a curve of the body. Some amphisbaenians, such as the large South American Amphisbaena species, take surprisingly large prey and regularly kill other reptiles as well as rodents. When hunting surface-dwelling prey, an amphisbaenian will lunge forward with its mouth open, grasping the prey with a powerful bite before dragging it underground. Alternatively, it might tear a chunk from the prey animal's body, sometimes by powerfully twisting after initially grabbing hold. Amphisbaenians return to disabled or deceased prey and it has even been suggested that they may scavenge from dead bodies lying on the surface.
Exactly how amphisbaenians relate to other squamates has long been controversial. Several radically different hypotheses have been published, and so much could be said about this subject that I’m deliberately going to avoid it for now.
If you were hoping for a big and comprehensive review of amphisbaenian evolution, diversity and biology – sorry, this isn’t it. But I’ll come back to them in time, and at least Tet Zoo now has something more than parody about them.
Tet Zoo now features some fairly reasonable coverage of squamate diversity... but there is still so much to do...
Dibamids and amphisbaenians
- The Tet Zoo guide to Gekkota, part I
- Gekkota part II: loud voices, hard eggshells and giant calcium-filled neck pouches
- Squirting sticky fluid, having a sensitive knob, etc. (gekkotans part III)
- Lamellae, scansor pads, setae and adhesion… and the secondary loss of all of these things (gekkotans part IV)
- The incredible leaf-tailed geckos (gekkotans part V)
- 300 years of gecko literature, and the ‘Salamandre aquatique’ (gekkotans part VI)
- Whence Uroplatus and… there are how many leaf-tailed gecko species now?? (gekkotans part VII)
- Ptychozoon: the geckos that glide with flaps and fringes (gekkotans part VIII)
- Meet the pygopodids (gekkotans part IX)
- The Great Goswell Copse Zootoca
- The New Forest Reptile Centre (on Zootoca and Lacerta)
- It’s high time you were told about Psammodromus
- Tale of the Takydromus
- Harduns and toad-heads; a tale of arenicoly and over-looked convergence
- Ermentrude the liolaemine
- ‘Cryptic intermediates’ and the evolution of chameleons
- Tell me something new about basilisks, puh-lease
- Amazing social life of the Green iguana
- The Squamozoic actually happened (kind of): giant herbivorous lizards in the Paleogene
- The enormous liolaemine radiation: paradoxical herbivory, viviparity, evolutionary cul-de-sacs and the impending mass extinction
- Leiosaurus: big heads, bold patterns
- Grassland earless dragons
- Australia, land of dragons (by which I mean: agamids) (part I)
- Australia, land of dragons (part II)
Scincomorphs and cordyliforms
- Evolutionary intermediates among the girdled lizards
- Isopachys: worm-like skinks from Thailand and Myanmar
- Mystery emo skinks of Tonga!
- Hammer-toothed skink SMASH!
- Pompey and Steepo, the world-record-holding champion slow-worms
- Arboreal alligator lizards – yes, really
- Of giant plated lizards and rough-necked monitors
- Slow-worms of 2008
- Dinosaurs come out to play (so do turtles, and crocodilians, and Komodo dragons)
- What I saw at the zoo yesterday... (more brief comments on Komodo dragons)
- Perentie tries to swallow echidna. Echidna too spiky, Perentie gets horribly injured. Dies.
- Monstersauria vs Goannasauria
- Goanna-eating goannas: an evolutionary story of intraguild predation, dwarfism, gigantism, copious walking and reckless thermoregulation
- Obscure and attractive monitor lizards to know and love
- “Lean, green and rarely seen”: enthralling prasinoid tree monitors
- Hell yes: Komodo dragons!!! (again)
- Stupidly large snakes, the story so far
- Scolecophidians: seriously strange serpents
- Side-stabbing stiletto snakes
- Terrestrial elapids, take 2
- Why do some snakes have horns?
- Close encounters with the Father of Death
- Not two, not three, but FOUR anacondas
- The tiniest snakes
- "What was that cute little Mexican snake?", and other musings...
- Snake 195 mm long eats centipede 140 mm long. Centipede too big. Snake dies.
- Micropechis ikaheka, the Small-eyed snake
- Help identify the snake. Please.
- Monster pythons of the Everglades: Inside Nature's Giants series 2, part II
- Possibly the first ever photos of a live Bothrolycus ater. Or: a test of how much information exists on a really obscure snake.
- The more you know about colubrid snakes, the better a person you are
- Love for Mastigodryas, Tomodon, Sordellina and all their buddies: you know it’s right
Refs - -
Gans, C. 1969. Amphisbaenians – reptiles specialized for a burrowing existence. Endeavour, 28, 146-151.
- . 2000. Amphisbaenians. In Cogger, H. G., Gould, E., Forshaw, J., McKay, G. & Zweifel, R. G. (consultant eds) Encyclopedia of Animals: Mammals, Birds, Reptiles, Amphibians. Fog City Press (San Francisco), pp. 650-655.
Gauthier, J. A., Kearney, M., Maisano, J. A., Rieppel, O. & Behlke, A. D. B. 2012. Assembling the squamate tree of life: perspectives from the phenotype and the fossil record. Bulletin of the Peabody Museum of Natural History 53, 3-308.
Kearney, M. 2003. Systematics of the Amphisbaenia (Lepidosauria: Squamata) based on morphological evidence from Recent and fossil forms. Herpetological Monographs 17, 1-74.
Pyron, R. A., Burbrink, F. T. & Wiens, J. J. 2013. A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes. BMC Evolutionary Biology 2013, 13:93 doi:10.1186/1471-2148-13-93
Vidal, N., Azvolinsky, A., Cruaud, C. & Hedges, S. B. 2008. Origin of tropical American burrowing reptiles by transatlantic rafting. Biology Letters 4, 115-118.