Derived Vertebrate Characteristics: Backbone, segmental – (usually surrounding/protecting dorsal nerve cord Skull

Figure 34.2 Echinodermata Cephalochordata Urochordata Myxini Petromyzontida Chondrichthyes Actinopterygii Actinistia Dipnoi Amphibia Reptilia Mammalia Milk Amniotic egg Limbs with digits Lobed fins Lungs or lung derivatives Jaws, mineralized skeleton Vertebrae Common ancestor of chordates Chordates Vertebrates Gnathostomes Osteichthyans Lobe-fins Tetrapods Amniotes Notochord ANCESTRAL DEUTERO- STOME

HAGFISH: skull of cartilage Rudimentary cartilaginous vertebrae Retained notochord that is made of cartilage at maturity Segmented muscles Marine Bottom dwelling scavengers Releases defensive slime

Lampreys Mostly marine Ectoparasites Larvae in freshwater, filterfeeders Most migrate to sea and mature Cartilage that lacks collagen Notochord in adult – rudimentary cartilage partially protect nerve cord Inner ear for dynamic equilibrium

GNATHOSTOMES Jawed vertebrates Another Hox gene duplication developed forebrain – w/ increased visual and olfactory capabilities Lateral line system in aquatic gnathostomes

Figure (b) Southern stingray (Dasyatis americana) Blacktip reef shark (Carcharhinus melanopterus) (c) Spotted ratfish (Hydrolagus colliei) (a) Pelvic fins Dorsal fins Pectoral fins

Chondrichthyes Sharks, rays,(elasmobranchs) and chimaeras (holocephalii) Skeletons of cartilage showing some mineralization. – Mineralization present in the teeth and scales Placoid scales – Homologous to teeth (in dev and structure) Paired appendages

Sharks: model chondrichthyans Powerful swimming poor maneuverability – Pectoral fins mostly for stability and lift Creates and stores massive amounts of oil in liver to help increase buoyancy – Still are negatively buoyant and will sink when not swimming Swimming helps ventilage gills, but then can also use jaw and pharynx muscle to pump water over gills Largest examples are suspension feeders that consume plankton BUT mostly carnivorous Rows of teeth that move forward as a conveyor belt Have a relatively short digestive tract – Spiral valve increases SA and prolongs passage of material in digestive tract (i.e., more digestion and absorption) Nostrils are dead ends for olfaction Entire body conducts sound to the inner ear Electroreceptors—ampulae of lorenzini Internal fertilization Males have claspers Oviparous, ovoviviparous, & viviparous Cloaca=digestive, urinary, and reproductive opening

Ampullae of Lorenzini

Osteichthyes=vertebrate clade with calcified endoskeleton (calcium phosphate) Term originally applied to boney fish – Now to all vertebrates with skeleton of bone tissue

Bony fish = actinopterygii + actinistia + dipnoi Have 4-5 pairs of gills – covered by a bony operculum Swim bladder  buoyancy control Gas can be transported in and out of gas bladder from blood controlling buoyancy Skin covered by flat, boney scales – Grow in size as fish grows Slime from glands – Reduces drag – Reduces topic infection Lateral line system Most species are oviparous with external fertilization, but there are lots and interesting variations

Figure 34.18

Ray—finned fish = Actinopterygii Have bony rays that support fins and in some cases connect to deeper skeleton Marine and fresh water Lobed fin fish Rod shaped bones surrounded by thick layers of muscle in pectoral and pelvic fins May have been used to “walk” across substrate under water—some extant species still do this Ceolacanth—actinistia Believed to be extinct but re-discovered in 1938 marine Dipnoi—lung fish Freshwater Swamps and stagnant water Gulp air into pharynx which connects to lungs—suplements gas exchange across gils (which are still main gas exchange organs)

Organ systems