Derived Vertebrate Characteristics:

• Backbone, segmental – (usually surrounding/protecting dorsal nerve cord

• Skull

Figure 34.2Echinodermata

Cephalochordata

Urochordata

Myxini

Petromyzontida

Chondrichthyes

Actinopterygii

Actinistia

Dipnoi

Amphibia

Reptilia

MammaliaMilk

Amniotic egg

Limbs with digits

Lobed fins

Lungs or lung derivatives

Jaws, mineralized skeleton

Vertebrae

Common ancestorof chordates

Chordates

Vertebrates

Gnathostom

es

Osteichthyans

Lobe-fins

Tetrapods

Amniotes

Notochord

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

(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