EEB267H1 Lecture Notes - Cyclostomata, Hagfish, Haikouella
1 Mar 2013
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Document Summary
What the phylogenetic tree for chordata looks like when we add one important fossil species: Haikouella vertebrata at least 530 my proto-vertebrae, true gills, two eyes, olfactory lobes at least 520 my dorsal hollow nerve cord, notochord, post-anal tail. Complete notochord with irregular cartilaginous blocks in places (proto-vertebrae) . True gills (larger pharyngeal openings, cartilaginous bars in pharyngeal openings are much larger and stronger, muscles to pump water through the openings, cilia. [seen on pharyngeal rods of amphioxus and tunicates] replaced by stronger, longer filaments) haikouella shows the first switch to a more active lifestyle in the chordates. These animals were capable of swimming for longer periods of time (true gills = better oxygen supply, higher metabolic rate) and selecting and tracking their prey via sight and smell. many molecular characters. The vertebrata (vertebra [joint or articulation of body]) also known as the craniata (from kranion [skull]) Representative outlines of the skull in a hagfish (top) and a lamprey.
