BIOL 204 Lecture Notes - Lecture 7: Pharyngeal Arch, Neural Crest, Endochondral Ossification
Document Summary
Parareptilia: only extent- turtles, bony shell (dorsal carapace and a ventral plastron, covered in epidermal scales. Lepidosauria: sphenodonta (tuatara, squamata (snakes, lizards, and amphisbaenids) Mammalia: monotremata: platypus and achidna, only 3 living sp. lay eggs. Mammalia: metatheria: metatherians and eutherians give birth to free-living young (viviparous, metatherians; young are born relatively early in development and are incubated and nursed after birth in a pouch. In vertebrates the endoskeleton (internal skeleton) is composed of 2 parts: cranial, skull, chondrocranium, splanchnocranium, dermarocranium, postcranial, axial skeleton, vertebral column, notochord, ribs, appendicular skeleton, limbs/paired fins, girdles. Components of the skull: skull is composed of up to 3 distinct components working together (mentioned earlier, ^differentiated based on their embryonic origins. In teleostomi, although initially forms as cartilage, the generally becomes partially or completely ossified into bone (endochondral bone) during development: forms ventral portion of braincase, but the dorsal region of the braincase is formed by the dermatocranium.
