Turtles

Turtles

• sister group to archosaurs

• anapsid skull is derived

• mainly endochondral bone, some dermal bones on the outside

• carapaces: upper shell made of ribs (endochondral bone)

• plastron: lower shell made from the shoulder girdle (endo), ventral dermal bones

Eunotosaurus primitive (late permian)

• ribes wide and flat = primative caraspace 

• number,size,structure identical to turtles 

• no intercostal muscles, like turtles ( cant do costal breathing)

• had teeth and diapsid skull unlike modern turtles

odontochelys (late Triassic)

• fully develpoed pastron (fused gastralia)

• partial caraspace: potected ribs and distict vertebrae 

• anapsid skull derived, had teeth (primative)

Proganochelys (late triassic)

• fully developed formed shell (earliest turtle with this)

• long tail

• lacked full neck retraction (unlike modern)

• anapsid and lacked teeth

turtle synapmorphys

• shell, limb girdles, and no teeth

shell

• bony skeleton and covering, body axis not flexible

• affects locomotion and respiration

limb girdles 

deep w/i ribs

ribs grow to enclose girdles, unlike among vertebrates

features not synapomoprhys

neck retraction and anapsid skull 

extant turtles

crypodires and pleurodires

cyrptodires

“hidden neck”

• turtle neck bends in “S” shape

• snapping turtles and sea turtles lost this 

pleurodires

“side neck”

neck bends sideways w/i shell, leaving one side of neck exposed

geography

• cryptodires found all over

• pleurodires in southern hemisphere

• all pleurodire species semi aquatic and freshwater

cryptodire diversity

pig nosed turtles,

soft shelled turtles,

sea turtles ,

snapping turtles,

pond turtles,

tortoises 

Shell covering

• keratinized scutes, overlap bony sutures adds strength

• skin: 3 aquatic species (pignose, softshell, leatherback) have flat shells

• terrestrial have round shells: makes it hard to eat them

locomotion

• sprawling posture

• no latteral movement

• no flexability in ankles

• freshwater: hindfeet w/ webb feet, forefeet webbing varies modified flippers

feeding 

no teeth, instead keratin beak 

tortiose; carnvores

turtle: omnivores

aquatic: only feed in water w/ suction (can ambush predators using tongue as bait)

softshell: bury in sand and wait

respiration

lungs at top of shell attached to gut

abdominal muscles move gut

inhale: gut moves down, lungs expand

exhale: gut moves up, lungs contract

underwater respiration

reduces need to resurface frequently

• pharyngeal respiration, pump water in and out pharynx, covered w/ villi 

• rhodutes kukops: cloacal respiration

circulation (turtle and lizard heart)

• completely divided atria

• right receives DEOx blood from body

• left receives Oxy blood from lungs

• incompletely divided ventricle has 3 compartments (can shift blood back and forth)

right-to-left shunting

pulmonary blood to systematic, more blood in ksin helps warm body up 

• blood may still mix

left-to-right shunting

blood from systemic circuit directed to pulmonary

might help to feed heart oxygen durring high activity

reproduction and nesting

• lay eggs in moist conditions, moisture helps embryo grow better

• no parental care

• embryonic diapause: pauses development until enviormental trigger

environment sexual determination

• type 1A: cold (male) warm (female)

• Type 2: intermediate temp(male) extreme temp (female)

• wetter nest: more males 

hatching behavior

interna;/external cues help synchronize hatching

• vocalie of more developed embryos speeds up development of slower embryos

• sychronized hatching provides more protection when moving to water

orientation and navigation

follows light/moon

follows elevation gradient

uses waves to pull them into water

adults use magnetic field to find exact beach and lay eggs there too bc of better survival