Herpetology Chp 1 & 2
Lectures 1&2
Herp history & evolution
Herp history & evolution
Terms
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- Tiktaalik
- fish-apod; limb-like fins capable 4 support in water; true neck
- neck
- lifting head for O
- Elpistostegidae
- lobe-finned fish w/ some tetrapod like feature: flattened body & head, elongate snout, orbits on top, no dorsal/anal fins, ribs project ventrally
- Synapomorphy
- New shared/derived trait b/c homoplasy or convergent evolution
- Mosaic evolution
- mosaic of ancestral and derived traits
- key features of herps
- terrestriality, tetrapods, ectothermy
- Lungs
- ancestral to swim bladder; evolved for gas exchange in low O water
- adapt 4 terrestriality
- grtr support-stronger vertebral column & limb girdles; feeding mechanics: suction 2 inertial feeding; middle ear structure 4 hearing
- Ichthyostega
- robust, not efficient on land, fish: external fert, jelly eggs, gills; could move on land
- paraphyletic
- everything but of descendant
- ectothermy
- temp matches environment; behavioral thermoregulation; environmentally constrained; metabolic efficiency
- Tetrapod synapomorphies
- well-formed limbs (paired distal limb bones- radial, ulna; tibia, fibula); neck (pectoral girdle); occipital condyles for rotating head
- Acanthostega
- "stem-tetrapod; primarily aquatic, shallow water, internal gills, 8 digits/foot
- limbs
- evolved in aquatic 4 moving in vegetation; prop up head for breathing
- Stem group
- includes extinct organism more closely related to crown than other group (Stego...)
- polyphyletic
- Describes invalid clades which group several species without a common ancestor
- Monophyletic or clade
- everything of descendant of ancestor
- Crown group
- all descendants of most recent common ancestor of certain extant organism (tetrapods of all living & extinct amphibians)