Testudines
- Created by: ValentineDevil
- Created on: 29-03-19 19:25
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- Testudines
- Diagnostics
- Massive breaks covered in sharp keratinous ridges
- No teeth
- Pectoral and pelvic girdles situated inside the rib cage
- Fan-shaped ribs
- Retractable neck
- Enlarged otic capsules
- Shell
- Dorsal carapace and ventral plastron forming an armour
- Ectothermic
- Some with high metabolic rates
- Anapsid skull, with posterior emargination
- No side openings behind the orbit
- Massive breaks covered in sharp keratinous ridges
- Leatherback Sea Turtle Adaptations
- brown fat tissue
- muscle-generated heat
- Countercurrent heat exchange mechanisms
- I.e. in flippers and around trachea
- Body temp. higher than that of the surrounding water
- 3m long
- Giant sea turtles Archelon and Protostega were even larger
- Neck retraction
- Cryptodira
- Pleurodira
- Withdraw neck sideways into the shell
- Only two extant families
- Bony elements
- Dorsal carapace and ventral plastron
- Vertebraw and ribs fused to dermal plates beneath skin which interlock to form a hard shell
- Exteriorly, the bony shell is covered by keratinous scutes
- Plastron is made up of 9 bones
- 2 epiplastra are homologous to the other clavicles of other tetrapods
- remaining plastral bones are homologous to abdominal ribs in other tetrapods
- pectoral and pelvic girdles are inside the rib cage
- Shoulder girdle has a triradiate configuration: consists of 2 scapula processes and 1 coracoid process
- Pelvic girdle is compact with stout ilia, ischia and *****
- Paired large openings (thyroid fenestrae) on the ventral surface of the pelvis
- Elongation of the trunk vertebrae
- Skull Morphology
- Extensive plate-like bones
- Anapsid type
- Absent of skull fenestrations
- Palate
- Maxilla forming a medial bony sheet fused with vomer and palatine
- Sight
- Well developed
- Colour vision
- Oil droplets occur in sensory cells of retina
- Blue, green, red, and double cone cells are present
- Smell
- Well developed
- jacob's organ present
- Gular pumping is thought to facilitate passage of air particles over the Jacob's organ
- Olfactory bulbs
- Internal Anatomy
- Massive lungs extending anteroposteriorly below carapace (attached to underside)
- Breathing
- paired transverse abdominis (TA) muscles wrapped around posterior portion of lungs
- Exhalation: compress the lungs when they contract
- Cup-shaped oblique abdominis (OA) muscles
- Inhalation: flatten, which causes an expansion of the inguinal flank posteriorly, ventrally and laterally
- Air forced out of lungs when head and limbs are retracted into the shell
- paired transverse abdominis (TA) muscles wrapped around posterior portion of lungs
- Hearing
- Cartilaginous tympanic disc, overlaying epidermis
- 'ear drum'
- lower sounds 100-60Hz
- Cartilaginous tympanic disc, overlaying epidermis
- Eunotosaurus
- Ribs: wide and flat, forms broad plates similar to a primitive turtle shell
- ribs t-shaped in cross section, each w/ broad, flat surface on top and narrow ridge running along its length on bottom
- most ribs fused to vert.
- babies show a diapsid skull
- Pappochelys
- wide body, small skull, long tail
- skull pointed, large eye sockets
- Several turtle-like features: expanded ribs and tightly packed gastralia
- Each rib flattened into broad-blade like structure w/ bumps and ridges covering outer surface and a ridge running down inner surface forming T in cross section; also diapsid skull
- Odontochelys
- teeth embedded in its upper and lower jaws
- Plastron, NO carapace
- wide ribs like modern turtle embryos (before developing ossified plates of carapace)
- Long-pointed skull and elongate tail
- evidence plastron evolved before carapace (indicates aquatic origin)
- How Shells came to be
- Carapacial ridge develops in lateral aspect of the flanks of the turtle embryo and will give rise to a carapacial margin
- The ribs are arrested in the dorsal part of body growing toward the carapacial ridge (amniotes: ribs grow ventrally)
- Serratus anterior muscles ventral to ribs because of the folding of the lateral body wall
- Ribs grow laterally and are confined dorsally
- Muscle plate eventually becomes folded at a level coinciding with tip of ribs- runs inside the scapula as in other amniotes
- Diagnostics
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