Topic 10: Lepidosaurs: Tuatara, Lizards, Snakes

Characteristics

• largest group of non-avian reptiles

• predominantly terrestrial

• scales cover the skin

• outer layer of epidermis is shed at intervals

• may have a reduction or loss of limns

• only tetrapod group with a transverse cloacal slit (horizontal instead of vertical)

2 Orders of Lepidosaurs

1. rhynchocephalia - tuatara

   1. only one extant species

2. squamata - lizards and snakes, more than 10k species (this is where species richness comes from)

Rhynchocephalia

aka tuatara, the only extant species (Sphenodon punctatus)

• only in NZ

• nocturnal animals that feed on invertebrates and small vertebrates (frogs, lizards, birfs)

• low active body temperatures because they live in damp, cool environments and are ectothermic for behavioural regulation

• live in burrows

Lizards

belong to squamata

• have determinate growth - genetically programmed to grow until X size then stop growing

• 42 families, about 6000 species

• range in size with many body forms

different species are adapted to their environments

• some have horns or spines for predators

• chameleons have zygodactylous feet (joining fingers/toes) with opposing fingers for grabbing tree limbs, and a prehensile tail for grabbing

• eyes most independently

most are dorsoventrally compressed and tend to be insectivores

Snakes

suborder serpentes

24 families, about 3000 species

• probably evolved from a subterranean (underneath earth) lineage of lizards

• range in size and body form

fossorial species have really reduced eyes since they’re subterranean, some have venom with specialized retractable teeth

Snake Characteristics

• forked tongues to collect chemical stimuli and transfer to the vermonasal organs

• skull is very flexible with loosely connected mandibles and flexible skin

• some are oviparous, others viviparous

• sex determination of most species is by genetics, but some have temperature dependent, like tuatara, some skinks, and gekkonids)

• most species have no parental care