Squamata - lizards and snakes
Chelonia - turtles
Crocodylia - crocodilians
Rhynchocephalia - Tuatara
What are the 4 orders of living reptiles?
Poikilothermic - easier to live in warmer climates
Dry scaled skin
Internal fertilisation
3/4 chambered heart
Aquatic, semi-aquatic, terrestrial and arboreal
Attributes of Reptilia
Smaller brain case - cerebrum smaller and simpler
Lower Jaw made of several bones, not just 1
Dentition - simple cheek teeth replaced continuously
Occipital condyles - reptiles 1, mammals 2
Middle ear bones - reptiles 1, mammals 3
Bony palate - reptiles i
How do reptile skulls differ to mammal skulls?
Ancient order, 1 surviving family, 2 surviving genus = tuatara, 2 species of tuatara
Externally resembles lizard
Similarities
-caudal autotomy (ability to detach tails when in danger)
Differences
-lack external ears
-parietal eye more formed
-lack of peni
Order: Rhynchocephalia characteristics
Has a retina, lens, cornea and nerves but not used for vision
Only visible in hatchlings, covered in scales and pigments after 4-6 months
Function is believed to be useful in absorbing UV and setting seasonal cycles.
Features of tuataras parietal eye
Includes all crocodiles, lizards, snakes, tuatara, birds and non-avian dinosaurs
Amniote tetrapods that developed two holes in each side of their skulls
Lizards lost one hole, snakes lost both
What are diapsids?
Prefer tropical climates but found on all continents but antarctica
Lizards - suborder Lacertilia
Snakes - suborder Serpentes
Order: Squamata characteristics
Bone between skull and lower jaw (quadrate) is loosely attached by ligaments
Means jaw open wide and have a faster, stronger bite
What are the differences of Squamata compared to Rhynchocephalia?
Quadrate bone hinges in 2 places to allow mouth to open wide and swallow large prey
Loose hinges allow mandible to move freely - chewing inefficient
Upper and lower teeth meet unpredictably - don't occlude
Loose jaw construction doesnt support masticatory
What are the properties of snake mandibles?
72 socketed teeth used for crushing bone, shredding and tearing flesh
Dentition fits within jaw enabling snap shut without damaging teeth
Jaw and snout long and narrow
Large robust skull with powerful muscles
Antagonistic masticatory muscles open jaw - ve
Order:Crocodilia characteristics
Alligator
- U shaped palate
- easier to eat turtles
- upper jaw wide so hides lower teeth
Crocodile
- V shaped palate
- easier to catch fish
- jaws similar width so all teeth exposed
Compare Alligators and Crocodiles
Gharial
-one of longest crocodilians
-males grow up to 21ft long
-eats fish
Caiman
-small crocodilians from south and central america
- straight, wide jaws
- upper jaw covers lower jaw
- technically alligators
Gharial/Gavial and Caiman crocodiles
Turtles
Both upper and lower jaw composed of multiple bones
Posterior braincase articulates with the cervical vertebrae
Order: Chelonia characteristics
5 major bones - frontal, parietal, premaxillary, nasal (top beak), mandible (bottom beak)
1 occipital condyle
Lightweight (1% of total bodyweight)
Beaks made of keratin on outside
Incredibly diverse - adapt to diet
No dentition - linked to flight adaption
Overview of bird skulls
Moveable bony ring surrounding eyeball
Have if non-spherical eyeballs or underwater habitat
Found in several groups of vertebrates except mammals and crocodilians
Owls turn head rather than move eyeballs
What is a sclerotic ring?
Seabirds secrete excess ions in a salty solution released into the nostril
Also called nasal/supraorbital glands
Fossae on skull
What is the function of salt glands?
Agnatha
Chrondrichthyes
Osteichthyes
What are the 3 classes of fish?
Jawless
Bony scales and skin plates present in ancient species but absent in living species
Cyclostomic (circular) mouth - suck blood
Hagfish and Lampreys
Agnatha characteristcs
Most fearsome predator to harmless mollusc eaters
Possess true bone and also a cartilaginous skeleton
Only the teeth are calcified, rarely vertebrae
Sharks, skates and rays
Chrondrichthyes characteristics
Have more or less bony skeleton and numerous vertebrae
Jaws present
Spindle shaped, oval in section and flattened
Protective scales
Some have actual lungs and sharp eyesight
Operculum = a bone on sides of fish protecting chambers that house gills
Fertilis
Osteichthyes characteristics
Ray finned - thin, flexible, skeletal rays
Lobe finned - muscular fins supported by bones
Describe the two groups of osteichthyes