As you may know, Tet Zoo has been going for four years now. Despite this, there are still entire tetrapod clades – consisting of hundreds or even thousands of species – that have scarcely been mentioned here, if at all.
Lately, I’ve been feeling ‘gecko guilt’. Yes, I can barely believe that the enormous squamate clade known as Gekkota has been all but unmentioned on these pages. I don’t have time to give the group any sort of justice (sorry, Gekkota), but here is a very brief intro to the group and how neat it is (aaaaand, as usual I wrote this sentence long before completing what you’re about to read…).
Gekkotans occur worldwide as more than 1500 species (some sources give figures of 2000 or so… if you keep an eye on the herpetology journals, you’ll know that new gekkotan species are constantly being described): they inhabit all continents except Antarctica, have done extremely well at colonising oceanic islands, and inhabit temperate regions (such as New Zealand) as well as subtropical and tropical ones. Most have well-developed limbs, but near-limblessness has also been evolved in the group. Indeed, because the near-limbless flap-footed lizards, snake lizards, pygopods or pygopodids are gekkotans, the term ‘gecko’ is not synonymous with Gekkota… unless you’re happy referring to pygopodids as geckos, and nobody really does that (… much. I have seen it done here and there) [the pygopodid Liasis burtoni (Burton's snake lizard) shown above; image courtesy of Wolfgang Wüster].
I’m going to use the spelling ‘gecko’ and ‘geckos’ here, but ‘gekko’ and the plural ‘geckoes’ are used by some.
Gekkotans are mostly ‘mid-sized’ lizards (with total lengths of 15 cm or so), but many are dwarfs. One species – Sphaerodactylus ariasae from the Dominican Republic – is adult at 1.6 cm [an S. macrolepis specimen from Puerto Rico shown here; photo by Samuel Thomas, from wikipedia]. The largest gekkotan – recently extinct Hoplodactylus delcourti from New Zealand* – reaches or reached 60 cm. There have never been any giant gekkotans so far as we know, nor are there any amphibious or aquatic ones.
* Probably. Worthy & Holdaway (2002) expressed scepticism about a New Zealand origin for this species (even though all other Hoplodactylus species are New Zealand endemics), only because additional specimens have never been found (the only known specimen – shown below, from wikipedia – was discovered in a French museum and its exact origin is unknown). I think it’s most likely that H. delcourti was endemic to New Zealand; it’s just that we have yet to find additional specimens (Naish 2004).
Introducing the cast
For ease of communication, I have to introduce the names of the main gekkotan groups now (their affinities and such will be covered later). As mentioned a moment ago, there are something like 1500-2000 gekkotan species but, as usual with herps, there’s nothing like a World Guide to Gekkotan Species – would anyone like to pay me to write one? If you’re in search of an introduction to the clade, good places to start are Mattison (1989), Bauer (2000) and Pianka & Vitt (2003). If you want to learn about the group on an intimate, species-level basis (good for you), you’ll have to rely on the primary literature, or on field guides. Among the best of the latter for gekkotans are Branch (1988), Cogger (2000)* and Spawls et al. (2004).
* Given its substantial weight I’m not sure it can be classed as a ‘field guide’…
As you’d expect for a group that includes 1500-2000 species, there’s a significant amount of disparity within the clade, and fossils indicate that some of the major divergences within Gekkota happened in the early Cenozoic or as long ago as the Cretaceous. If gekkotans were birds or mammals, they’d have been classified into something like 50-100 ‘families’ or more, or even into several separate ‘orders’. But, no, these are reptiles, so people have mostly been happy with a classification where all of those species, spanning an evolutionary history of more than 50 million years, are grouped into two – yes, TWO – family-level groups (namely, Gekkonidae and Pygopodidae). Huh. I’m not necessarily saying that a new classification is needed: my point is that ‘historical inertia’ has shaped our perception of diversity across the tetrapod clades (see Frost et al. (2006) for more on this subject). Anyway, in the scheme followed here, five main gekkotan groups are recognised: eublepharids, diplodactylines, pygopodids, gekkonids and sphaerodactylids. A sixth proposed clade might also exist: the phyllodactylids.
A relatively small number (c. 25 species) of terrestrial North American, African and Asian gekkotans are grouped together in Eublepharidae. The best known eublepharid is the familiar Leopard gecko Eublepharis macularius of southern Asia [shown here: photo by Fritz Geller-Grimm, from wikipedia]. Because they lack digital pads and possess eyelids, eublepharids have typically been regarded as morphologically primitive compared to other living gekkotans.
The vast majority of gekkotan taxa are part of Gekkonidae, and this group has often been divided into two ‘subfamilies': Gekkoninae and Sphaerodactylinae. Gekkoninae has conventionally been thought to include such geckos as Cyrtodactylus (bow-fingered geckos), Phelsuma (day geckos), Gekko (calling geckos), Phyllodactylus (American leaf-toed geckos), Ptychozoon (flying geckos), Tarentola (wall geckos) and Uroplatus (leaf-tailed geckos). Typically, five genera have been included within Sphaerodactylinae (Coleodactylus, Gonatodes, Lepidoblepharis, Pseudogonatodes and Sphaerodactylus), all of which inhabit the Caribbean and South and Central America. This group of genera is best known for including numerous tiny species. However, some studies (e.g., Gamble et al. 2007) find these taxa to be part of a more inclusive clade that also includes several Old World taxa, among which are the wonder geckos or frog-eyed geckos (Teratoscincus). The name Sphaerodactylidae has been used for this ‘expanded’ sphaerodactyl clade. Phyllodactylus and an assemblage of other taxa (Asaccus, Haemodracon, Homonota, Phyllopezus, Ptyodactylus, Tarentola and Thecadactylus) have recently been allied in a molecular phylogeny and named as the new clade Phyllodactylidae (Gamble et al. 2008). Phyllodactylids are the sister-group to Gekkonidae according to these authors. To date, only a few other authors have used the name Phyllodactylidae (e.g., Blair et al. 2009) and it will be interesting to see if other studies support the monophyly of this proposed clade.
Diplodactylines or diplodactylids are an entirely Australasian group that seem to form a clade with the snake-like pygopodids (Kluge 1987, Donnellan et al. 1999, Conrad 2008). Some diplodactylines – including knob-tailed geckos (Nephrurus), New Caledonian geckos (Rhacodactylus) and chameleon geckos (Carphodactylus) – are sometimes grouped together as the carphodactylids, carphodactylines or carphodactylins. They might warrant distinction relative to diplodactylines (and may be closer to pygopodids than diplodactylines are), might be a diplodactyline clade, or might be a grade within diplodactylines.
A few other gekkotan groups have sometimes been recognised. Teratoscincus was considered worthy of its own ‘subfamily’, termed Teratoscincinae, by Kluge (1987) [T. keyserlingii shown here; from wikipedia]. The Cat gecko Aeluroscalabotes felinus of south-eastern Asia has also been given its own ‘subfamily’ on occasion, dubbed Aeluroscalabotinae (modern classifications generally include A. felinus in Eublepharidae) while a group of African gekkonines have sometimes been referred to as the Ptyodactylini.
We’ll look at gekkotan phylogeny later on. Much more to come. Coming next: voices, eggshells and cervical sacs.
For previous Tet Zoo articles on neat squamates see…
- Mosasaurs might have used the same microscopic streamlining tricks as sharks and dolphins
- Tongues, venom glands, and the changing face of Goronyosaurus
- Dinosaurs come out to play (so do turtles, and crocodilians, and Komodo dragons)
- Tell me something new about basilisks, puh-lease
- ‘Cryptic intermediates’ and the evolution of chameleons
- The Great Goswell Copse Zootoca
- Of giant plated lizards and rough-necked monitors
- Ermentrude the liolaemine
- Evolutionary intermediates among the girdled lizards
- Hell yes: Komodo dragons!!!
- Amazing social life of the Green iguana
- Arboreal alligator lizards – yes, really
- Pompey and Steepo, the world-record-holding champion slow-worms
Refs – –
Bauer, A. M. 2000. Lizards. 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. 564-611.
Blair, C., Méndez de la Cruz, F. R., Ngo, A., Lindell, J., Lathrop, A. & Murphy, R. W. 2009. Molecular phylogenetics and taxonomy of leaf-toed geckos (Phyllodactylidae:
Phyllodactylus) inhabiting the peninsula of Baja California. Zootaxa 2027, 28-42.
Branch, B. 1988. Field Guide to the Snakes and Other Reptiles of Southern Africa. New Holland (London).
Cogger, H. G. 2000. Reptiles & Amphibians of Australia (Sixth Edition). New Holland Publishers (Sydney).
Conrad, J. L. 2008. Phylogeny and systematics of Squamata (Reptilia) based on morphology. Bulletin of the American Museum of Natural History 310, 1-182.
Donnellan, S. C., Hutchinson, M. N. & Saint, K. M. 1999. Molecular evidence for the phylogeny of Australian gekkonoid lizards. Biological Journal of the Linnean Society 67, 97-118.
Frost, D. R.., Grant, T., Faivovich, J., Bain, R. H., Haas, A., Haddad, C. F. B., De Sá, R. O., Channing, A., Wilkinson, M., Donnellan, S. C., Raxworthy, C. J., Campbell, J. A., Blotto, B. L., Moler, P., Drewes, R. C., Nussbaum, R. A., Lynch, J. D., Green, D. M. & Wheeler, W. C. 2006. The amphibian tree of life. Bulletin of the American Museum of Natural History 297, 1-370.
Gamble, T., Bauer, A. M., Greenbaum, E. & Jackman, T. R. 2007. Evidence for Gondwanan vicariance in an ancient clade of gecko lizards. Journal of Biogeography 35, 88-104.
– ., Bauer, A. M., Greenbaum, E. & Jackman, T. R. 2008. Out of the blue: a novel, trans-Atlantic clade of geckos (Gekkota, Squamata). Zoologica Scripta 37, 355-366.
Kluge, A.G. 1987. Cladistic relationships in the Gekkonoidea (Squamata, Sauria). University of Michigan Museum of Zoology Miscellaneous Publications 173, 1-54.
Mattison, C. 1989. Lizards of the World. Blandford (London).
Naish, D. 2004. New Zealand’s giant gecko: a review of current knowledge of Hoplodactylus delcourti and the kawekaweau of legend. The Cryptozoology Review 4 (2), 17-21.
Pianka, E. R. & Vitt, L. J. 2003. Lizards: Windows the Evolution of Diversity. University of California Press (Berkeley).
Spawls, S., Howell, K., Drewes, R. & Ashe, J. 2004. A Field Guide to the Reptiles of East Africa. A & C Black (London).
Worthy, T. H. & Holdaway, R. N. 2002. The Lost World of the Moa. Indiana University Press (Bloomington, Indiana).