ZOO 2090 Lecture Notes - Lecture 3: Recapitulation Theory, Ernst Haeckel, Actinopterygii

• School: University of Guelph
• Department: Zoology
• Course: ZOO 2090
• Professor: Jinzhong Fu

Document Summary

Mouth present, but no biting apparatus derived from pharyngeal arches. Two extant groups, hag shes and lampreys, together often referred to as cyclostomes. Groups were already highly specialized by 330 mya and display features likely representative of ancestral agnathans. Scavengers of the deep sea (~70 species) that can also prey on invertebrates. They use a rasping tongue"; a cartilaginous plate bearing horny teeth-like processes. Many are parasitic, using their round mouth to cling to live prey while sucking blood, others use their mouth to cling to substrate. Were known only from hard tooth-like elements for a long time. So abundant they are used for stratigraphic dating (540-230 mya) Fossils found in early 1980s highlighted vertebrate characters (dentin and enamel, notochord, myomeres, postanal tail) Complex feeding basket in the pharynx and large eyes suggest that they were active feeders. Small jawless shes that displayed a lateral line system and an outer exoskeleton made up of dermal bone plates.