Turtles (Testudines)

Testudines

376 Species, 14 families

found worldwide

mostly aquatic or semi-aquatic

carnivores, herbivores, etc.

all lay eggs

synapomorphies

• loss of teeth (beak)

• anapsids

• shell

• only vertebrates that have their pectoral and pelvic girdles inside their rib cage

Carapace

the upper shell

made up of dermal bones intimately associated with the ribs and vertebrae

Plastron

The lower shell

made up of bones of the shoulder girdle (interclavicle and clavicle) and several additional bones

Origin of Turtle Shell

• New fossil finds now suggest that the sequence of

events leading to the turtle shell was a series of

transitional states

– Widening of the ribs

– Formation of bony ventral structures that eventually

fused to become the plastron

– Formation of fused carapace elements and ribs

How to Turtle’s Breathe?

Muscles move viscera to increase and decrease pressure in lungs instead of ribcage expanding and contracting

Two Turtle Clades

Pleurodira = “side necked turtles” (horizontal retraction)

Cryptodira = “hidden-necked turtles” (vertical retraction)

Pleurodira

Side necked turtle clade

includes 3 families of (mostly) obscure turtles from South America, Australia, Africa, and Madagascar

Cryptodira

hidden necked turtle clade

11 families of turtles found all over the world (but not in Australia or Madagascar)

• Most diverse in Asia and North America

• Includes most of the turtles that you have ever heard of

Turtle Pleurodira Phylogeny

Chelidae

15 genera, 69 species

• Found in Australia and New Guinea and South America

• Aquatic, mostly freshwater

• Omnivorous

Only major group of freshwater turtles in Australia

Most species-rich family of turtles in South America

mata-mata turtle

Pelomedusidae

2 gen, 27 sp

• Africa, Madagascar (most species-rich turtle family in Africa)

• Aquatic, freshwater

• Carnivorous

Podocnemidae

3 gen 8 sp

• 2 genera in South America (Peltocephalus, Podocnemis)

• 1 genus with 1 species in Madagascar (Erymnochelys)

• Herbivorous, aquatic, freshwater (rivers and lakes)

• Podocnemis are very large

• Large numbers come ashore at night to nest on sandy beaches (like sea turtles)

• individuals seem to return to same beach where they were born

• Harvested for meat and eggs some highly endangered

Turtle Cryptodira Phylogeny

Trionychoidea

• Clade that unites the Carretochelyidae and Trionychidae

Synapomorphies:

• Snout has fleshy proboscis

• No keratinized scutes on shell

• Hard parts of carapace covered by leathery skin

• Shell is more flattened than other turtles (more streamlined for faster swimming?)

Trionychidae

Soft Shelled Turtles

• 13 genera, about 36 species

• Found in North America, Asia, Africa

• Aquatic, carnivorous

• like to bury themselves with just head sticking out

• ambush and attack

Carettochelyidae

1 gen, 1 sp

• Found only in New Guinea and northern Australia

• Aquatic (freshwater, brackish), omnivorous

• Feet like Flippers

• Flaps both forelimbs simultaneously like sea turtles

Rest of Cryptodira (Excluding Trionychoidea)

Kinosternidae

Dermatemydidae

Geoemydidae

Testudinidae

Emydidae

Platysternidae

Chelydridae

Cheloniidae

Dermochelyidae

Kinosternonidae

Mud and Musk Turtles

4 gen, 33 sp

North America to South America

Aquatic, mostly carnivorous

poor swimmers, tend to walk on bottom

many have hinged plastron

Chelydridae

Snapping Turtles

2 gen, 6 sp

• North America to northwest South America

• Big, aquatic (freshwater or brackish), omnivorous

• Poor swimmers, walk on bottom

Chelydra serpentina - common snapping turtle

Macrochelys temminckii - Alligator snapping turtles (rare and endangered) (fish lure tongue)

Cheloniidae and Dermochelyidae

Sea Turtles

• Paddle like forelimbs

• only primarily marine turtles

• fully aquatic

• females come ashore to nest on beaches

Cheloniidae

Sea Turtle

5 gen, 6 sp

Found in oceans nearly worldwide (temperate and tropical, but not arctic)

Feed on plants or animals attached to the substrate

Green Turtle is herbivorous

Hawksbill Turtle feeds on sponges

Dermochelyidae

Leatherback Sea Turtle

1 gen, 1 sp

• Carapace is composed of small osteoderms embedded in leathery

skin (hence name)

• Has reduced skeleton and very paedomorphic (juvenile) morphology

• Yet, is largest living turtle, up to 2–2.5 meters long

• Ranges into colder waters thanks to partially warm blooded

• Feeds in the water column

• Eat jellyfish

Emydidae

12 gen, 57 sp

aquatic to terrestrial

carnivorous to herbivorous

majority are aquatic

2 fully terrestrial species

Testudinidae

Tortoises

17 gen, 58 sp

• Found nearly worldwide in tropical and warm-temperate areas

• Most diversity in Africa and Asia

• Terrestrial, many herbivorous or omnivorous

• stocky, elephant like legs

• tall, domed shell

• enlarged scales on front of forelimbs

• Pancake tortoise (Malacochersus tornieri) has flattened, soft

shell and hides in rock crevices

• 3 species of tortoises in United States (genus Gopherus)

• Found only in warmest parts of the country

Galapagos Tortoises

Giant tortoises

1 sp, 15 subspecies

• Different subspecies occur on different islands or even different parts of islands

• Some have strikingly different shell shapes

• Saddleback occurs on drier islands; food is harder to reach (e.g., tree cacti)

• Domed shell occurs on wetter islands (can graze on grass and other low growing plants)

Are giant tortoises on Galapagos and Seychelles related?

• Two giant species became Giant separately 

  • (Island rule) (Big animals get small, small  animals get big) - NOT THE CASE

  • They are actually just the last remaining species of giant tortoise 

  • There used to be giant tortoises on almost all major landmasses

Geoemydidae

Eastern Pond Turtles

• 19 gen, 73 sp 

• Global tropical distribution 

• Aquatic, semi-aquatic, terrestrial 

Platysternidae

Big Head Turtle

• 1 sp, 3 subspecies 

• Huge head 

• Asia 

• Can not retract head 

• Mainly terrestrial and can climb 

• Not a good swimmer 

Dermatemydidae

River Turtle

• 1 sp, 1 genus 

• Central America 

• Herbivorous, aquatic, nocturnal 

• Only leaves water to lay eggs 

• Eggs can survive underwater