Yet again I am going to have to go quiet-ish on Tet Zoo for a little while as I just cannot put the time into completing the many planned articles. Sigh. One thing approaching on the near horizon is eating up lots of my research time: the third Big Cats in Britain conference, happening in early March, and at which I’m speaking. I’ll post details on it over the next few days. For now, I thought I’d enthuse a bit about lizards: like (I’m sure) everyone in the UK interested in zoology, I am watching David Attenborough’s Life in Cold Blood series at the moment, and last night’s episode (number 3, ‘Dragons of the dry’) was about lizards. I’m hoping to talk more about the series later on, as it has included some amazing stuff that hasn’t been shown on TV before. For no particular reason (although they were featured in one episode of Life in Cold Blood I think), here are random thoughts on girdled lizards, the cordylids…
Girdled lizards are endemic to Africa and include about 50 species in four genera: flat-bodied flat lizards Platysaurus, the flattish crag lizards Pseudocordylus, the deeper-bodied, often spiny girdled lizards, zonures or sungazers Cordylus and the serpentiform grass lizards or ground lizards Chamaesaura. Molecular work indicates that Pseudocordylus is not monophyletic, with different species being nested in among the Cordylus assemblage (Frost et al. 2001). Furthermore, Cordylus seems to be paraphyletic to not only Pseudocordylus, but also to Chamaesaura. Frost et al. (2001) proposed that, as a result, both Pseudocordylus and Chamaesaura should be sunk into Cordylus, but this idea doesn’t yet seem to have caught on (or, maybe it has: see du Toit et al. 2004) and I’ll continue to use the old names for convenience.
Cordylids are closely related to another armoured scincomorph clade, the Afro-Madagascan gerrhosaurids or plated lizards, and the two were formerly grouped together. Some workers think that they should be united again in an inclusive Cordylidae. Gerrhosaurids + cordylids = Cordyliformes. The cordylid fossil record is poor (that of gerrhosaurids is better, with good records from the Miocene of Africa and possible records from the Eocene or Oligocene of Europe), but an Upper Cretaceous lizard from Madagascar, Konkasaurus mahalana, was cautiously interpreted as a cordylid by Krause et al. (2003).
Chamaesaura is weird: very long-tailed (the tail might be three or four times the body length), snake-like in movement, and superficially like reduced-limbed or limbless anguids but with an altogether more cordylid-look to the integument (the body scales are sharply keeled). They differ from most other cordylids in that osteoderms are restricted to the head (a condition which has convergently arisen in ‘Pseudocordylus‘ species). They’re viviparous, giving birth to 5-9 babies. ‘Pseudocordylus‘ and Cordylus sensu lato are viviparous too, with females giving birth to one or two surprisingly large babies [image above shows Armadillo girdled lizard giving birth, her mouth open in a silent scream. Image borrowed from Gary Fogel's excellent page here]. Platysaurus (indicated by phylogenies to be the most basal cordylid) is oviparous, with females producing two elongate eggs. The remarkable flat bodies of these lizards have apparently resulted in the evolution of low clutch size and unusual egg shape (Pianka & Vitt 2003)
The three Chamaesaura species (Transvaal grass lizard C. aenea, Cape grass lizard C. anguina and Large-scaled grass lizard C. macrolepis), usually called grass lizards (a dumb name: it’s used around the world for various entirely different types of lizard), recall other reduced-limbed, serpentiform lizards (like certain skinks for example) in that they represent a continuum, with one species (C. aenea) having five clawed digits on all four limbs, another (C. anguina) having only one or two clawed digits on its very much reduced limbs, and a third (C. macrolepis) lacking forelimbs, and only have a single clawed digit on its tiny, spike-like hindlimbs (Branch 1988) [adjacent image shows C. macrolepis, with arrow pointing to tiny hindlimb. C. macrolepis is also the species shown at the very top of the article: image from Herpetology in South Africa]. Broadley & Branch (2002) noted that the Ukinga girdled lizard Cordylus ukingensis appears to approach the Chamaesaura species in having a very reduced osteoderm compliment and in lacking the lateral groove that Cordylus species normally have along the side of the body.
While most cordylids are apparently solitary animals, the Armadillo girdled lizard Cordylus cataphractus is gregarious, with groups of up to 30 sharing the same refuge site. Lone individuals tend to be adult males; these differ from females in reaching larger sizes and in having proportionally larger heads and longer tails (Mouton et al. 1999). As a defensive measure, members of this species form a spiky ring by grabbing their tails in their mouths [see adjacent image]. Much recent work has been done on sorting out the many Cordylus species: there are terrestrial species, arboreal ones (like Co. tropidosternum), and melanistic ones that inhabit the cool Atlantic coast of South Africa (Broadley & Branch 2002, Mouton et al. 2002). I was originally planning to write more about these species, but got distracted by the grass lizards. And that’s it – time’s up, back to work…
Refs – -
Branch, B. 1988. Field Guide to the Snakes and Other Reptiles of Southern Africa. New Holland, London.
Broadley, D. G. & Branch, W. R. 2002. A review of the small east African Cordylus (Sauria: Cordylidae), with the description of a new species. African Journal of Herpetology 51, 9-34.
du Toit, A., Mouton, P. le F. N. & Flemming, A. F. 2004. Aseasonal reproduction and high fecundity in the Cape grass lizard, Cordylus anguinus, in a fire-prone habitat. Amphiphia-Reptilia 24, 471-482.
Frost, D., Janies, D., Mouton, P. le F. N. & Titus, T. 2001. A molecular perspective on the phylogeny of the girdled lizards (Cordylidae, Squamata). American Museum Novitates 3310, 1-10.
Krause, D. W., Evans, S. E. & Gao, K.-Q. 2003. First definitive record of Mesozoic lizards from Madagascar. Journal of Vertebrate Paleontology 23, 842-856.
Mouton, P. le F. N., Nieuwoudt, C. J., Badenhorst, N. C. & Flemming, A. F. 2002. Melanistic Cordylus polyzonus (Sauria: Cordylidae) populations in the Western Cape, South Africa: relics or ecotypes? Journal of Herpetology 36, 526-531.
Pianka, E. R. & Vitt, L. J. 2003. Lizards: Windows to the Evolution of Diversity. University of California Press, Berkeley.