ZOO 2090 Lecture Notes - Lecture 3: Acipenseriformes, Holostei, Endochondral Ossification

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

Document Summary

Mouth present, no biting apparatus from pharyngeal arches. Two extant groups, hagfishes and lampreys, together referred as cyclostomes. Scavengers of the deep sea (~70 species) prey on invertebrates. use rasping tongue"; a cartilaginous plate bearing horny teeth-like processes. Marine or freshwater inhabitants (~ 40 species). Parasitic, using round mouth to cling to prey, Fins (dorsal, unpaired) & image-forming eyes (unlike hagfish). Were known only from hard tooth-like elements for a long time. Abundant so used for stratigraphic dating (540-230 mya) Fossils found in1980s highlighted vertebrate characters (dentin and enamel, notochord, myomeres, postanal tail) Complex feeding basket in pharynx and large eyes suggest active feeding. Small jawless fishes that displayed a lateral line system and an outer exoskeleton made of dermal bone plates. Were extinct by the end of the devonian (>100 my) Allowed new diets and food-handling techniques, e. g. , firm grip, cutting and grinding.