LECTURE 5 - OUTLINE Evolution & Classification - Part I Evolution & Classification 1. Overview - vertebrate origins 2. Overview - extant fishes Agnatha 3. Phylogenetic relationships 4. Conodonta 5. Pteraspidomorphi BIOL 4340 – Lecture 5 - 1 Overview : origin of vertebrates Gnathostome(s)Sacabambaspis - raptorial feeders - pharyngeal expansion rapid & strong - rapid mouth closure & strong bite Agnathan(s) - exploited expanded pharyngeal pump - deposit feeders, mud grubbers etc. - transitional raptorial feeders 1. expansion of pharyngeal pump 2. definitive mouth closure Prevertebrate(s) - suspension feeders - feeding based on ciliary “pumps” - developed muscular pharyngeal pump 1. encircling band of muscles - pharynx 2. cartilage replaced collagen - pharyngeal bar BIOL 4340 – Lecture 5 - 2 1 MBP (millions of years before present) - each column, first known fossil trace - widths, estimates of abundance and diversity - traditional broad groups across top - conodonts missing BIOL 4340 – Lecture 5 - 3 Overview : extant fishes Phylum Chordata Subphylum Vertebrata (Craniata) Superclass Agnatha Superclass Gnathostomata (jawless vertebrates) (jawed vertebrates) Class Myxini Class Chondrichthyes (hagfishes) Subclass Holocephali Class Cephalaspidomorphi (ratfish) (lampreys) Subclass Elasmobranchii (sharks/skates/rays) BIOL 4340 – Lecture 5 - 4 2 Overview : extant fishes Phylum Chordata Subphylum Vertebrata (Craniata) Superclass Gnathostomata (jawed vertebrates) Class Sarcopterygii Subclass Coelocanthimorpha (coelocanths) Subclass Dipnoi (lungfish) Class Actinopterygii Subclass Chondrostei (sturgeons/bichirs) Subclass Neopterygii (gars/bowfin) Superclass Agnatha Division Teleostei (all “modern” fishes) Phylogenetic Relationships (e.g. lancelet) (jawless vertebrates) BIOL 4340 – Lecture 5 - 5 Conodonta Cephalochordata Myxini (outgroup) Loss: mineralized dental tissue; eyes Pteraspidomorphi : extant : extinct Cephalaspidomorphi Gnathostomata true bone cellsjaws lateral line neural crest,tripartite ectodermal brain placodes ? 3 Conodonts Cambrian (544 - 505 mbp) - Triassic (250 - 208 mbp) Gk. kōnos , cone; odous , tooth Conodont elements - tooth-like microfossils - generally < 1 mm long - used for dating marine sediments Molluscs? Chordates? Aquatic Plants? - origins unknown until ~1973 !! - origins unknown until ~1983 BIOL 4340 – Lecture 5 - 7 Conodonts Cambrian (544 - 505 mbp) - Triassic (250 - 208 mbp) - laterally compressed animal bearing a complete set of conodont elements - chordate hallmarks present Conodont elements - evidence of wear & tare - mineralized dental tissue 1. calcium phosphate 2. enamel 3. dentin * *dentin laid down by odontoblasts, indirect evidence for the presence of a neural crest BIOL 4340 – Lecture 5 - 8 4 Class Pteraspidomorphi (“ostracoderms”) Late Cambrian (544 - 505 mbp) - Late Devonian (410 - 360 mbp) Gk. ostrakon , shell; derma , skin First vertebrates to possess; - paired appendages - lateral-line system - bone (acellular) Bone located almost exclusively as an outer exoskeleton Endoskeleton; - fibrous tissue - cartilaginous elements - occasionally bone cephalic plates fused, head shield BIOL 4340 – Lecture 5 - 9 Class Myxini (hagfishes) Cambrian (544 - 505 mbp) - to date Myxinikela siroka scale bar = 1 cm - functional eyes - no slime glands BIOL 4340 – Lecture 5 - 10 5 Class Myxini (hagfishes) Cambrian (544 - 505 mbp) - to date slime gland pores - scaleless, worm-like, 3 pairs of barbels surrounding mouth - 1 to 14 lateral gill openings & a series of slime gland pores - caudal fin present but no paired fins or dorsal fin - eyes degenerate (blind) and no lateral-line system BIOL 4340 – Lecture 5 - 11 6.