BIOL211 Lecture Notes - Lecture 4: Notochord, Dermal Bone, Endostyle
6 Dec 2014
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Document Summary
An important feature of early vertebrates was the development of a distinct head end that contained a tripartite brain within the cranium. Instead of sessile filter feeders early vertebrates were active predators. The ostracoderms are an assembly of extinct, armored jawless fishes. Dermal bone formed body armor (ostrac = shell, derm = skin) Early soft-bodied vertebrates were small, fish-shaped specimens or eel like in formation. Contain evidence of a notochord & myomeres . Also have a cranium & sensory structures at head end : early vertebrates, class agnatha. The first vertebrates lived in the cambrian era (~500 mybp) They are placed in the class agnatha jawless vertebrates. Early agnathans are often referred to as ostracoderms shell skins in reference to their bony armour. Although ostracoderms have been extinct since ~300 mybp we still have some extant members of the class agnatha today: ostracoderm characteristics. Single nostril on the top of the head rather than a pair.
