Ch 15 Lepidosaurs

Question 1

snakes share a common ancestor with…

Answer 1

a group of lizards

Question 2

Clade Lepidosauria

Answer 2

1 tuatara, 7000 lizards, 4000 snakes;
snakes monophyletic, but also part of lizard clade;
“lizard” by itself is a grade (paraphyletic)

Question 3

lepidosaur synapomorphy

Answer 3

keratinous overlapping scales, transverse cloacal slit, tail autotomy

Question 4

tail autotomy

Answer 4

ability to cause tail to fall off to escape predators, breaks at fracture plane of a caudal vertebra and can later regrow with a cartilagenous rod replacing tail vertebrae

Question 5

earliest known reptiles with tail autotomy lived in…

Answer 5

early Permian

Question 6

other lepidosaur characteristics

Answer 6

mainly terrestrial, many groups have reduced or lost limbs

Question 7

tuatara

Answer 7

diverse group during Mesozoic,
only extant species left,
lives in New Zealand,
nocturnal, has lowest optimal body temp of any reptile, primarily insectivorous, unique dentition, bony beak formed from fused snout bones

Question 8

unique dentition of tuatara

Answer 8

2 rows of teeth on upper jaw, 1 row on bottom jaw, for shearing food, structure of jaw joint allows bottom teeth to slide between upper teeth after mouth closes

Question 9

tuatara reproduction

Answer 9

slow growing, takes 10-20 years to reach sexual maturity, females mate every 4 years, lay 5-19 eggs, gestation period is about 8 months, incubation period in egg outside body is 11-16 months, no external genitalia, evidence suggests ancestor had a penis

Question 10

squamate synapomorphies

Answer 10

includes all lizards and snakes:
determinant growth, hemipenes

Question 11

determinant growth

Answer 11

growth occurs for a genetically determined period of time,
smaller size enables insectivory, in turtles and crocodiles

Question 12

hemipenes

Answer 12

paired copulatory organs (single or absent in all other amniotes),
stored in tail (males have longer tails), everted during copulation, only use one at a time, extravagantly ornamented, species-specific designs

Question 13

squamate anti-predator behavior

Answer 13

crypsis/camouflage, aposematic coloration, Batesian mimicry, playing dead

Question 14

crypsis/camouflage

Answer 14

blending into surroundings, solor-changing in anoles and chameleons, visual and behavioral, stripes to appear motionless while moving through vegetation

Question 15

aposematic coloration

Answer 15

bright coloring to advertise toxicity
ex. venomous snakes

Question 16

batesian mimicry

Answer 16

harmless species mimics the warning coloration of a toxic species to reduce predation
ex. scarlet king snake mimics coral snake

Question 17

playing dead

Answer 17

hog snake technique to avoid predation

Question 18

sexual dimorphism

Answer 18

common social behavior in “lizards”, males typically bigger

Question 19

visual cues

Answer 19

common social behavior used by iguanas and anoles,
ex. anole dewlaps and behavioral displays (head-bobbing, tail-wagging, etc.)

Question 20

dewlap

Answer 20

species-specific throat fan, in anoles

Question 21

pheromones

Answer 21

chemicals released by many lizards and snakes to attract mates

Question 22

vocalizations

Answer 22

social behavior common to geckos

Question 23

squamate reproduction

Answer 23

oviparity, viviparity, parthenogenesis

Question 24

oviparity in squamates

Answer 24

probably ancestral, most common

Question 25

viviparity in squamates

Answer 25

20% of squamates, associated with cooler climates, pregnant lizards more vulnerable to predation

Question 25

parthenogenesis in squamates

Answer 25

in 6 families of lizards and 1 snake species, create all-female populations genetically identical to mother, higher reproductive potential (important in frequently disturbed habitats)

Question 26

iguanas

Answer 26

can grow to large size, terrestrial or arboreal, primarily herbivorous, use short bursts of movement to escape threats, good swimmers

Question 27

chameleons

Answer 27

typically diurnal, primarily insectivorous, specialized arboreal lizard, zygodactylous feet, and prehensile tail, body laterally compressed, slow-moving, specialized tongue and hyoid apparatus allow tongue projection, independently mobile eyes and binocular vision for hunting prey

Question 28

geckos

Answer 28

large well-developed eyes, no eyelids, toe pads with setae allow dry adhesion to vertical and upside down surfaces

Question 29

setae

Answer 29

projections of highly modified scales on toe pads of geckos, so tiny that they form molecular bonds with surfaces

Question 30

amphisbaenians

Answer 30

"double walk", fossorial features, large median upper tooth fits between 2 lower teeth to act as sharp forcepts

Question 31

fossorial

Answer 31

burrowing

Question 32

fossorial features

Answer 32

limbless (or reduced limbs), heavily ossified skull for digging tunnels, eyes often reduced, elongate body, short tails, reduce right lung due to elongation of body, skin is loose and moves independently of skeleton

Question 33

telescoping

Answer 33

skin moves independently of skeleton

Question 34

helodermatids

Answer 34

5 living species, SW US to Guatemala, stout, flat head, blunt tail, venomous (no muscles around venom glands); eat mammals, birds, eggs, lizards, insects

Question 35

monitors

Answer 35

in Africa, Asia, and Australia; fast-moving, active predators, use gular pumping, varied carnivorous diet, forked tongue used to smell

Question 36

gular pumping

Answer 36

monitors can inflate/deflate their throat

Question 37

Komodo dragon

Answer 37

type of monitor, largest living lizard, two glands in lower jaw secrete toxic proteins

Question 38

snakes

Answer 38

limbless (earlier fossils had legs), elongated body, short tail, left lung reduced or absent, right kidney in front of left, about 120+ precloacal vertebrae, lack eyelids, have clear scale near eyes for protection, diverse diet (some venomous), wide range of habitats

Question 39

snake reproduction

Answer 39

oviparous or viviparous, little sexual dimorphism

Question 40

snake sensory systems

Answer 40

sight is limited, forked tongue aids in chemoreception, lack external and middle ear, have internal ears with receptors, many have one or more infrared-detecting pit organs

Question 41

snake feeding

Answer 41

highly kinetic skulls and jaws to eat prey larger than head, swallow slow and head first, eat mostly live prey, kinetic skull is very fragile; methods include constriction, envenomation, and oophagy

Question 42

constriction in snakes

Answer 42

grab with jaws, coil around prey, tighten coils; short vertebrae for tight coiling, short trunk muscles for strong contractions, morphology limits speed

Question 43

envenomation in snakes

Answer 43

use venom to kill prey, safer for snake, venom secreted by gland in upper jaw, muscles squeeze out venom, venom consists of complex mix of proteins and other molecules that differ among species

Question 44

oophagy in snakes

Answer 44

egg eating, very mobile jaws, vertebrae have ventral projections that press into egg and crack it, reduction in number of teeth