Slide 1

Fish The Earliest Vertebrate Animals A.Urochordates (tunicates) B.Cephalochordates (amphioxus) C.Craniata (fishes) Slide 2 Fish & Primitive Aquatic Vertebrates preservation Sharks teeth & skin denticles Teleosts (bony fish) bone, otoliths & scales Conodonts tooth elements Slide 3 Urochordate larva free swimming with a notochord, but as an adult it morphs into a sessile sponge like form. Slide 4 Cephalochordate Amphioxus has a notochord with V-shaped body muscles, a primitive brain at the anterior end and is free swimming Slide 5 Jawless fish (agnathids) develop from the Ordovician through the Devonian in three groups: Heterostracans- headshields with eyes on sides Osteostracans- headshields with eyes atop and lateral fins Furcacaudiformes- (forktails) GOKWTA Slide 6 The Ostracoderm Astrapis from the Ordovician of Colorado. Jawless, lacked an internal bony skeleton and sported bony armor and a heavy headshield, eyes on side. Slide 7 Slide 8 The jawless Heterostracan Anglaspis heavily armored, lacked jaws with a crude ventral mouth, eyes on side of skull Silurian and Devonian Slide 9 The Devonian Heterostracan Pteraspis with typical heavily plated headshield but flexible trunk and tail, lateral eyes. Slide 10 The configuration of gills in early jawless fish was simplicity itself with water taken in at the mouth and passing out through several gill slits shown in black. Between each gill slit was a thin strip of bone, the gill arch (in white) that supported the gill. .To adapt a simple jaw required only the development of a crude hinge on the first gill arch. Slide 11 Reconstruction of the gill structure of the Heterostracan Amphiaspid closely resembles an automobile manifold structure Slide 12 Gill structure and function on most living fish are remarkably similar regardless of the taxonomy with plates mounted on a rigid axis and two pumps; one for blood and one for water (In a similar fashion a water cooled engine requires a water pump and a fan) Slide 13 The Osteostracan cephalaspid Hemicyclaspis had the typical armored headshield of a jawless fish but featured paired fins, a flexible tail for propulsion and eyes atop skull (Late Silurian to Devonian) Slide 14 Unlike the Heterostracans the Osteostracans as Hemicyclaspis shown here had small eyes set very close together atop their heads. Slide 15 Only discovered in 1998 the early Devonian Furcacudiformes or forktails dont conform to the other jawless fish (heterostracans & osteostracans) and seem to be an entriely new group of agnathids Slide 16 Fish with jaws (the Gnathostomes) Slide 17 DEVONIAN FISH Fish first appear in the Ordovician period but the number and variety of fish explodes in the Devonian so the name age of fish is highly apropos for this period Slide 18 The Upper Devonian primitive gnathostome placoderm arthrodire Dunkleosteus featured a massive 6 foot long headshield with scissor-like jaws mounted on a 20 foot long body Slide 19 The second group of placoderms, the Antiarchs are characterized by the genus Pterichthys shown here with a well armored body and small mouth sited below the eyes. Restricted to the Devonian period they were probably sediment feeders like an earthworm or snails. Slide 20 The anterior-ventral pectoral appendages of the antiarch Pterichthys tell us they groveled about the bottom only rarely rising off the sediment water interface Slide 21 Sharks (Chondrichthyes) Legendary resistance of phosphate parts to dissolution CaPO 4 Apatite composition Tooth classification (natural) Denticle classification (classically artificial) Mainly used in marine geology for deposits well below CCD Sharks remarkable for slow evolution and subsequent looooong stratigraphic ranges Slide 22 Slide 23 Slide 24 Slide 25 Slide 26 Slide 27 Slide 28 Slide 29 Slide 30 Slide 31 Slide 32 Slide 33 Slide 34 Slide 35 The Actinopterygiians or ray-finned bony fish (Osteichthyes) include the zillions of species of extant bony fish the Teleosts that underwent a phenomenal evolutionary explosion beginning in the Jurassic Slide 36 The Devonian lungfish Dipterus is remarkably similar to modern coelacanths found in very deep water off South Africa and Indonesia today. Slide 37 A living fossil! The coelacanth Latameria is a lobe finned fish with close relatives dating back to the Devonian period over 400 million years ago Slide 38 As soon as the first specimen of the coelacanth Latimeria was brought to the surface the demand from museums and ichthyologists world wide quickly threatened their dwindling stocks. The animal was very nearly studied to death! Slide 39 Slide 40 Anterior ventral, posterior ventral and posterior ventral fins lobe fins of the extant Sarcopterygian coelacanth Latimeria all display a well developed (robust) internal bony skeleton in stark contrast to the ray finned fish (Actinoperygians) Slide 41 Bony Fish (Teleostei) Extremely successful group, regardless if you measure success by diversity, biomass or adaptive radiation Bone, otoliths, scales, teeth Bone of little use unless skeleton is articulated Otoliths used to assess age of populations by annular growth rings Scales extremely useful in subdividing deeper portions of Los Angeles Basin (Lore Rose David) Slide 42 Slide 43 Slide 44 Slide 45 Slide 46 Slide 47 Slide 48 Slide 49 Teleost (bony) fish Slide 50 Slide 51 Slide 52 Angel Fish Pliocene, Po Valley, Italy ~3 m.y.a. Slide 53 Slide 54 Slide 55 Slide 56 Feeding Strategies Predator Slide 57 Slide 58 Slide 59 Slide 60 Slide 61 Slide 62 Conodonts Candidate affinities Snail radula Scolecodonts Cephalopod molluscs Fish teeth Gill supports Slide 63 Slide 64 Slide 65 Slide 66 Slide 67 Conodonts Biostratigrapy Cambrian Triassic Thermal maturation (Harris, Epstein & Harris 1977) CaPO 4 composition bilateral symmetry facies free = nektonic primitive fish Classically parataxial fossils Discovery papers on biological affinity by: Scott 1969 Briggs, Clarkson & Aldridge 1983 Slide 68 Conodont Morphology Simple cones Compound cones Blade/bar Platform TRENDS Cambrian simple cones Ordovician compound cones, blades/bars Silurian platforms appear Devonian modified platforms (plates) appear Miss/Penn expansion of escutcheon on oral side Permian/Triassic mostly blades & cusps, fewer platform types Slide 69 Slide 70 Thermal Maturation - Conodonts (also utilized with palynomorphs) Pigment change due to enclosed organics Experimental work by Harris et. al. Munsell soil color chart- Pale yellow 50 - 80 C Very pale brown 50 - 90 C Brown to dark brown 60 - 140 C Very dark greyish brown-dark reddish brown-black 110 - 200 C Black 190 - 300 C Black +300 C Clear to crystal clear >300 C Slide 71 Slide 72 Slide 73 The End