EARTH 307: Lecture 19: Reptiles 1

Class Reptilia

• respiration through skin was lost as they moved away from aquatic environments

• evolved by active breathing by changing volume of chest box, this happened through the development of chest bone

• skin became thicker, losing capability to absorb the atmospheric oxygen

• reproduction is through small number of eggs, protected by shell and sometimes parents

What are the 3 informal groups?

• defined by the occurrence/absence and number of opening behind eye socket

1. Anapsid - no opening

2. synapsid - one

3. diapsid - 2

Earliest reptiles

• small sized, lizard like and most insectivores (some adapted to carnivorous diet)

• mixture of anapsid and diapsid with the latter group being dominant

• adapted to terrestrial environment

• small number were tree gliders or adapted to aquatic environments

Synapsid evolution

• most important adaptation which began in Pennsylvanian times

• 2 synapsid groups dominated during upper Pennsylvanian - Triassic times

• order pelycosauria and therapsida

Order Pelycosauria

• evolved endothermy and thermoregulation

• 3m in length

• referred to as back sail reptiles although not all developed this

• middle/upper carboniferous - upper permian

• synapsid

Order therapsida

• mammal like reptiles

• some were large with massive bones

• further developed thermoregulation

• Pennsylvanian - triassic

• evolved from pelycosauria

• dominant reptile group in middle permian - lower triassic

• in upper triassic, they gave birth mammals

• synapsid

Order Mesosauria

• small aquatic reptiles (max 1m), lizards to crocs

• their fossils were used to demonstrate continental drift, found in southern hemi

• lower permian

• anapsid

Order placdontia

• aquatic reptiles that found food in shallow water

• dentition is adapted for shell crushing (bivalves, gastropods, cephalopods)

• triassic

• diapsid

Order ichthyosauria

• aquatic reptiles with streamlines body and paddled members

• tail is situated in vertical plane

• predators, fish eaters, could swallow prey whole

• triassic - cretaceous

• diapsid

Order sauropterygia

• aquatic reptiles with massive body and long neck

• 4 members are pddle-like

• fish eaters

• triassic - cretaceous

• diapsid

Order pterosauria

• winged reptiles that evolved flight

• at first interpreted as gliders but more data suggested active mode of flight

• entothermic

• upper triassic - cretaceous

• diapsid

Order crocodilia

• predators living in aquatic environments (fresh waters) but can move inland on short distances

• cold blooded, distribution restricted to equatorial and tropical regions

• upper triassic - holocene

• diapsid

Order chelonia

• aquatic to terrestrial reptiles that evolved protective plates on ventral and dorsal side (plastron and carapace)

• evolved from multiple ancestors

• upper triassic - holocene

• anapsid

Order Squamata

• most diverse order of reptiles and includes lizards, iguanas, chameleons

• marine to terrestrial

• jurassic - holocene

• diapsid