Origin of Tetrapod Body Plan: water-land transition
- Created by: ValentineDevil
- Created on: 28-02-19 10:52
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- Origin of Tetrapod Body Plan: water-land transition
- Tetrapod Emergence:
- 1. Lungfish-tetrapod separation
- 2. Stem-tetrapod diversification
- 3. Crown-tetrapod emergence
- 2. Stem-tetrapod diversification
- 1. Lungfish-tetrapod separation
- SARCOPTERYGIAN
- Lobe fins
- Muscular part connecting fin to either shoulder or pelvic girdle
- Fins are borne on fleshy, lobe-like, scale-covered stalk
- Appear early in the history of the group
- Fin/limb skeleton is joined to the girdle via a single bone
- Endoskeleton
- Humerus, radial and ulna
- Paired fins and limbs show one main axis
- Monoaxial appendages!
- Fin and limb skeletons show extensive distal endochondral ossification
- Cosmoid scales
- 1. Basal, dense lamellar layer of isopedine
- 2. Middle layer of spongy, vascularised bone
- Top, complex layer of dentine (cosmine)
- Outer coating of vitrodentine
- Broadly similar to the ganoid scales
- Primitively, broad snouts and small orbits
- Configuration of Skull bones
- Conserved pattern of bones is super imposed over the primitive osteichthyan pattern
- parietal and postparietal bones in dermal skull roof meet in a dermal joint
- the external manifestation of a endocranial hinge
- Neurocranium: dorsally hinged and mobile intracranial joint
- Neurocranium ossifies as two units completely separated by a ventral cranial fissure
- Large shoulder girdle elements
- Enlarged clavicles and expanded dorsal part of the girdle
- Lobe fins
- Rhizodontida
- Deepest part of family tree
- Panderichthyida
- Fish-tetrapod intermediate
- Tiktaalik roseae
- Close relative, another fish-tetrapod intermediate
- Tetrapod Emergence:
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