Week 2 - Origin of Tetrapods and Reptiles

Amphibian meaning

amphi = double

bios = life

amphibians live in two extremes (land and water) throughout their lifetime

Carboniferous

the age of amphibians

urodela/caudata

salamanders: loss of bone in skull, eastern US and central Mexico are hotspots, yes legs, usually no metamorphosis

gymnophiona

caecilians: legless and tailless, burrowers, tropical

anura

frogs/toads: 7,713 spp, large hind legs, tailless as adults

permeable skin

water and gases can pass through skin

tetrapodomorph

whats leading up to amphibians as we know it, large heads, double breathers, well-ossified skeleton

acanthostega

stem tetrapods, ceratobrachis (internal fishlike gills), more aquatic

sarcopterygii

lobe-finned fish, lungfish and coelacanths, mixed land and aquatic traits

Tiktaalik

FINS WITH WRISTS; connection between water and land

Ichthyostega

first good land vertebrate fossil, fish-like tail, polydactyl, strong girdles

lissamphibia

modern amphibians; loss bone in skull, three chambered heart, loss of scales, mostly four digits, two ear bones

Temnospondyli

gave rise to lissamphibia, more aquatic lifestyle, hands reduces to four digits

problems with land life

gravity, locomotion, breathing, feeding, reproduction, outer covering, pumping blood, sensory systems

Why move to land?

predation hypothesis, food availability on land, competitive avoidance

testudines

turtles; closer related to crocs and birds, archelon is the largest turtle, carapace and plastron

amniotes

amniotic egg, skull fenestration

skull fenestration

holes/windows in the skull; allows graeter movement and allows for more muscles without too much weight

squamata

lizards, snakes, worm lizards; scale patterns, paired hemipenes, lost legs in some

amniotic egg

provides aquatic environment for embryo, breaks tie to water!!!!!!!!!!!!!!

rhynchocephalia

tuatara; 1 spp, New Zealand

serpentes

snakes; lost limbs, ectoderms, specialized jaw

amphisbaenia

worm lizards; limbless, borrowers, limblessness is analogous

ichthyosauria

extinct, highly specialized marine spp, similar to dolphins