covered with thousands of setae, 

 hairlike structures that branch into 

 hundreds of microscopic endings, 

 called spatulae, that maximize con- 

 tact with a surface. 



Flap-toots belong to the Aus- 

 tralian family Pygopodidae. Py- 

 gopodids are elongate lizards with 

 no forelimbs and greatly reduced 

 hind limbs. Some are burrowers, 

 others terrestrial or arboreal. Many 

 flap-foots swim through grass tus- 

 socks. Some are nocturnal, others 

 diurnal. Some mimic venomous 

 snakes in coloration or by acting menacingly. 



One flap-foot, Lialis, acts more like a snake than it 

 does other lizards in that it swallows very large prey, 

 including other lizards. Skinks, Lialis's primary prey, 

 are armored with bony plates known as osteoderms 

 embedded in their scales, and so, like some skink- 

 eating snakes, Lialis has evolved hinged teeth. When 



Flap-foot (Lialis burtonis), a snakelike, virtually limbless lizard shown here about 

 two times life size, specializes in eating other lizards, which it swallows whole. It 

 has an extremely flexible joint in the middle of the skull, which enables it to raise 

 and lower its upper jaw when catching and killing prey. 



a tooth hits an osteoderm, it folds, whereas a tooth 

 that goes between scales remains erect, giving it 

 good purchase. As the skink squirms and wiggles in 

 the jaws of Lialis, it literally ratchets itself down the 

 predator's gullet. 



Autarchoglossans, "independent tongue" reptiles, 

 pick up heavy, nonairborne chemicals from surfaces 



SQUAMATA 



RHYNCHOCEPHALIA 



SCLEROGLOSSA 



AUTARCHOGLOSSA 



Cladogram, a diagram that shows evolutionary branching points, depicts probable 

 interrelations among living families and other large groups in the order Squamata, 

 as well as their shared ancestry with the Rynchocephalia, once a much more wide- 

 spread and diverse group. Within squamates, iguanians have prehensile tongues 

 for capturing prey, an ancestral feature lost in scleroglossans. Autarchoglossans 

 use their tongues to pick up heavy, nonairborne chemicals and deliver them to the 

 vomeronasal organ, a sense organ in the roof of the mouth. 



July/August 2006 NATURAL HISTORY 



33 



