I really want to get these pygopodid articles finished. Actually, I really want to get the whole gekkotan series finished: the end is in sight and I know I’ll get there eventually. In the previous articles on pygopodids (part of the long-running series on gekkotan lizards: see links below), we looked at pygopodid diversity and biology in general, and also at the phylogeny and evolutionary history of these fascinating, snake-like gekkotans. This time round, we look in more detail at the various different pygopodid taxa – not on a species-by-species basis (alas), but according to the units we typically term genera. The most famous pygopodids – the Lialis species or snake-lizards – are covered in the next article. [Diagram below shows a simplified version of the Jennings et al. (2003) phylogeny, with diagrammatic pygopodid heads from Kluge (1974).]
As before, remember that the group being discussed here is ‘Pygopodidae of tradition’, not Pygopodidae as currently formulated by some authors. More on this matter later.
Aprasia: blindsnake-mimicking pygopodids
I mentioned in the previous article that Aprasia appears to be a blindsnake-mimicking, ant-eating pygopodid.
The 11 or so Aprasia species resemble blindsnakes (Typhlopidae) in overall appearance, and also recall them in having a reduced dentition and a very short tail (a real constrast to other pygopodids where the tail can be as much as four times body length). The Aprasia species are also typhlopid-like in being binge-feeders (Webb & Shine 1994): that is, they feed infrequently but consume large numbers of prey on the occasions when they do feed. In snakes, there’s a debate as to what binge-feeding in typhlopids (and other scolecophidians) might tell us about the early stages of snake feeding behaviour (see the discussion in the scolecophidian article).
The Aprasia species are variable in head shape (look at the portraits above, all from Kluge (1974). Head length in most of these animals is less than 5 mm). Most have deep, short, rounded snouts, but A. haroldi at least has a more pointed snout and a sloping dorsal outline to its head. A. rostrata has a distinctly overhanging, pointed snout tip [diagram shown here from Kluge (1974). It also has an extra postnasal scale, marked here with an arrow]. Or, had a distinctly overhanging, pointed snout tip: its type (and only) locality, Hermite Island off the north-west coast of Western Australia, was subjected to atomic weapons testing in the 1950s. No specimens have been collected since, rendering it possible that it’s now extinct [UPDATE: it was rediscovered in 2006! And it's not unique to Hermite Island - it also occurs on nearby Trimouille Island. See comments].
A. smithi is unique among Aprasia species in having a black head. Its tail is black too – this is likely one of those cases where the tail-tip functioned as a ‘head mimic’. One Aprasia species (A. aurita) differs from the others in possessing a small external ear (Kluge 1974).
Delma is the largest ‘genus’ within Pygopodidae, containing about 16 species. Prior to the publication of Kluge’s enormous 1974 monograph, most Delma populations were included within D. fraseri (two additional species were also recognised pre-Kluge). It should therefore be noted that pre-Kluge articles that refer to D. fraseri typically refer to members of other species (but exactly which species can’t usually be determined). [Adjacent image shows D. borea; by Stewart Macdonald, used with permission.]
Delma species have conspicuous ear openings and some have longitudinal stripes or dark transverse head bands, though these markings tend to fade with age (the opposite is true, however, of D. impar). To Northern Hemisphere eyes, Delma species superficially recall glass lizards or natricine snakes, but they’re far more specialised for arid environments than either of those groups. [D. tincta shown below; by Stewart Macdonald, used with permission.]
At least some Delma species appear to be generalists, able to thrive in diverse microhabitats. D. australis, for example, has been discovered in grass clumps, in termite mounds, in spoil piles next to roads, and under logs and coral slabs on beaches. Individuals of D. fraseri have been discovered in ‘disturbed’ locations like trash piles and one specimen was even found swimming in a tidal pool (Kluge 1974).
The Javelin lizard
You’ll have noticed from the pictures I’ve been using in this series of articles that the two Lialis species – popularly known as snake-lizards – have particularly long, slender snouts (of course, if you know anything about pygopodids already, you’ll have known this anyway). However, Lialis isn’t the only long-snouted pygopodid. The Javelin lizard Aclys concinna (named as a new species by Kluge in 1974) is very obviously named for its relatively long, pointed snout (Aclys means javelin) [see diagrams below, from Kluge (1974)]. This slender, smooth-scaled climbing species is also notable for its dark longitudinal stripes. The type specimen was collected in a back garden in Western Australia (insert comment about ease with which people can find new species in Australia); according to Kluge (1974), local people there already knew it as the ‘hoop snake’ because of its tendency to contort and coil when alarmed. It seems to have an extremely restricted range, being found only in the Shark Bay region and the lower west coast of WA (Cogger 2000).
While Kluge originally considered the Javelin lizard worthy of ‘generic’ status, he later demoted it to a ‘subgenus’ of Delma (Kluge 1976). MtDNA data supports its distinction relative to all other pygopodids, but combined data doesn’t (Jennings et al. 2003) – in fact, combined data shows that it’s the sister-taxon to the uncontroversial Delma species D. labialis. While some authors now refer to the Javelin lizard as D. concinna, others still use Kluge’s original generic name for it.
The Javelin lizard is not just interesting for being scansorial, it also seems to include a significant amount of unspecified plant material in its diet (see John Scanlon’s comment on this subject here). The fact that pygopodids combine a snake-like form with occasional herbivory (a not thoroughly surprising discovery in view of their gekkotan heritage) makes it tempting to suggest that they somehow have the potential to evolve dedicated herbivory in the future – how cool would that be? It also suggests that the total absence of herbivory (even occasional or facultative herbivory) in snakes might not be anything to do with the snake body plan: it could instead be linked to some indelible trait specific to snakes (and not to long-bodied squamates in general), like some aspect of their dentition, skull construction or digestive system.
Paradelma and Pygopus
Another monotypic genus – Paradelma – was traditionally recognised for Pa. orientalis (the Brigalow scaly-foot) from central-eastern Queensland [adjacent photo by Stewart Macdonald, used with permission.]. This woodland species is reported to be an occasional climber and, as we saw in the previous article, individuals in at least some populations eat tree sap. It’s glossy brown with a black bar behind the head and conspicuous ear openings. Recent phylogenetic studies have found Pa. orientalis to be part of the Delma lineage, but as the ‘most divergent’ species (that is, it’s outside of the clade formed by the other species) (Jennings et al. 2003). This means that its recognition at ‘generic’ rank is down to personal opinion, and different authors do different things. Pa. orientalis is one of several pygopodid species that may be threatened by habitat change, environmental disturbance, and/or habitat fragmentation (remember that many pygopodid species are restricted to relatively small areas and are hence already vulnerable to human-caused changes). The type locality – Peak Downs in Queensland – is now heavily cultivated and grazed.
Pygopus contains five relatively large, robustly built, widespread pygopodids, popular known as scaly-foots (seven species were recognised by Wells & Wellington (1985), one of which was named P. klugei). P. lepidopodus, the Common scaly-foot, is very attractive, often marked with a complex pattern of lateral stripes, lines and/or spots. There are a few surprising extra-limital records for P. lepidopodus: two from Tasmania and one from New Zealand (Kluge 1974). However, the Tasmanian records are apparently mistakes of some sort and the New Zealand record represented an introduction. The latter was established by W. R. B. Oliver in 1921 (yes, the same W. R. B. Oliver who wrote the 1949 monograph ‘The moas of New Zealand and Australia’). I was interested to see that Oliver used the name ‘Australian slow-worm’ for the pygopodid in question.
Ophidiocephalus and Pletholax
One of the most poorly known pygopodids is Ophidiocephalus taeniatus, a small species (c. 10 cm long) with a pointed snout, enlarged head scales, small eyes and an external ear that’s hidden from view by the temporal scales.
It seems to be a specialised ‘sand-swimmer’ and superficially it much resembles certain limbless (or near-limbless), sand-swimming skinks. Ophidiocephalus was long thought to be extinct following the 1897 collection of the single holotype from Charlotte Waters in southern Northern Territory, right in the middle of Australia. Additional specimens didn’t show up until 80 years later in an adjacent part of northern South Australia. [Image above combines drawings from Kluge (1974) with photo by Stewart Macdonald, used with permission.]
Pletholax gracilis is apparently closely related to both Ophidiocephalus and the Aprasia species (like Ophidiocephalus, the genus is monotypic). It’s a small, slender pygopodid with a pointed, beak-like snout, and it’s unique to coastal areas of south-western Western Australia [adjacent diagrams from Kluge (1974)]. A dark stripe runs across the side of the face, beneath the eye and along the neck, and the throat and thorax are yellow in breeding males (Cogger 2000). A unique feature of this species is the presence of keeled ventral scales (Kluge 1974).
So, that’s it, apart from Lialis. Most of the information you’ve just read is easy enough to find in books and the technical literature (as I said before, Pianka & Vitt (2003), Cogger (2000) and Kluge (1974) are the most useful primary resources on these lizards*) but not, it seems, so easy to find for free, online. Hopefully this article helps to remedy this situation a little. Knowledge is power, with great blogging comes great responsibility and all that.
* I really must get a copy of Aller Greer’s The Biology and Evolution of Australian Lizards. Shame it’s so expensive.
For the previous articles in the gekkotan series, see…
- 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 pygopodid radiation: diverse diets and the ‘pygopodids got there first’ hypothesis (gekkotans part X)
And for previous Tet Zoo articles on other kinds of squamates, please see…
- Pompey and Steepo, the world-record-holding champion slow-worms
- Arboreal alligator lizards – yes, really
- Amazing social life of the Green iguana
- Hell yes: Komodo dragons!!!
- Ermentrude the liolaemine
- Evolutionary intermediates among the girdled lizards
- The Great Goswell Copse Zootoca
- Of giant plated lizards and rough-necked monitors
- ‘Cryptic intermediates’ and the evolution of chameleons
- Tell me something new about basilisks, puh-lease
- Tongues, venom glands, and the changing face of Goronyosaurus
- Mosasaurs might have used the same microscopic streamlining tricks as sharks and dolphins
- Dinosaurs come out to play (so do turtles, and crocodilians, and Komodo dragons)
- Isopachys: worm-like skinks from Thailand and Myanmar
- Mystery emo skinks of Tonga!
- Cambodia: now with dibamids!
Refs – –
Cogger, H. G. 2000. Reptiles & Amphibians of Australia (Sixth Edition). New Holland Publishers, Sydney.
Jennings, W. B., Pianka, E. R. & Donnellan, S. 2003. Systematics of the lizard family Pygopodidae with implications for the diversification of Australian temperate biotas. Systematic Biology 52, 757-780.
Kluge, A. G. (1974). A taxonomic revision of the lizard family Pygopodidae. Miscellaneous Publications, Museum of Zoology, University of Michigan, 147, 1-221
– . 1976. Phylogenetic relationships in the lizard family Pygopodidae: an evaluation of theory, methods and data. Miscellaneous Publications, Museum of Zoology, University of Michigan 152, 1-72.
Pianka, E. R. & Vitt, L. J. 2003. Lizards: Windows the Evolution of Diversity. University of California Press, Berkeley.
Webb, J. K. & Shine, R. 1994. Feeding habit and reproductive biology of Australian pygopodid lizards of the genus Aprasia. Copeia 1994, 390-398.
Wells, R. W. & Wellington, C. R. 1985. A classification of the Amphibia and Reptilia of Australia. Australian Journal of Herpetology, Supplementary Series 1, 1-61.