Classification

Phylum Chordata

SubphylumUrochordata

SubphylumCephalochordata

SubphylumVertebrata

tunicates lancets AgnathansFishSharkstetrapods

Chordate Characteristics

Pikaia- earliest known chordate

Burgess Shale Fauna(540 MYBP)

1st fish

Proto-vertebrate

Tunicate larvae Adult tunicate

lancelet

Possible evolution of 1st fish

Adult tunicate Larval tunicate

Amphioxus

1st dinosaur

end of dinosaurs

1st reptiles1st amphibians

1st land plants1st fish

1st invertebrates

Millions of YearsGeologic Time Scale

Class Agnatha, the jawless fishesSubclass (or order) Cyclostomata, the lampreys and

hagfishes.

Class Chondrichthyes, the cartilaginous-skeleton fishesSubclass Holocephali, the chimaeras, or ratfishesSubclass Elasmobranchii, the sharks, skates, and rays

Class Placodermi

Class Acanthodii

Class Osteichthyes, the bony fishesSubclass Actinopterygii, the ray-finned fishes

Superorder Chondrostei, the primitive ray-finned bony fishes: sturgeons, paddlefish, and bichirs

Superorder Holostei or Neopterygii, the intermediate ray-finned fishes: gars and the bowfin

Superorder Teleostei or Neopterygii, the advanced bony fishes: herring, salmon, perch.

Subclass Crossopterygii, the coelacanthSubclass Dipnoi or Dipneusti, the lungfishes

Evolution of Jaws in fish

agnathostome gnathostome

1st appeared 400 mya

chondocranium

palatoquadrateHyomandibular arch

Meckel’s cartilage

Ostracoderm400 mya

• Lack jaws, paired fins, scales• Possess medial nostril, medial fins,

notocord rather than vertebral column

heterostracan

ClassAgnatha

Hagfish

• Strictly marine• No bone • Rasping tongue • Eyes degenerate, covered by skin; no pineal; single pair

of semicircular canals• No lateral line organs• 5-15 pair gills• Partial open circulatory system• Holonephros and neotenic pronephros• Numerous slime glands in skin, secrete copious

amounts of mucus;• Separate sexes, but all individuals have ovitestis,• Eggs deposited at sea; direct development; totally

marine

Hagfish characteristics

Lamprey

Lamprey Characteristics

• Oral disc/buccal funnel, with epidermal denticles and rasping tongue; active "predatory parasites”

• No bone• Nostril on top of head• Well-developed vertebrate eyes • Well-developed Lateral Line system • Best developed pineal “eye” of any aquatic vertebrate;• 2 pairs of semicircular canals;• Uniformly 7 pairs of gills• Cranium cartilaginous, open on top• Opisthonephros• Eggs deposited in freshwater; freshwater larva; many

species have freshwater adult, but most migrate to sea and have marine adult stage (anadromous).

• Posses jaws with teeth, cartilaginous skeleton, paired fins• Scales (denticles) have same origin and composition as teeth• Possesses 5-7 gills• Spiral valve intestine• Ureoosmotic strategy• Lateral line• No swim bladder• Heterocercal tail• Relatively unchanged (480 mybp)

ClassChondrichthyes

Placoid scales

Basic Shark Anatomy

ClassChondrichthyes

• Totally fossil, early jawed fishes;• Bony armor usually present around head-trunk,

generally flattened body, tend to be bottom-adapted with eyes rather dorsal (other various designs);

• No true teeth• Notochord persistent, un-constricted.

ClassPlacodermi

Class Placodermi

• Posses jaws with teeth• bony skeleton• paired fins• 4 paired gill arches covered by operculum• Intestine- simple, no spiral valve• Swim bladder• Lateral line• Homocercal tail• Scales- cycloid, ctenoid, ganoid

ClassOsteichthyes

Basic Fish Structure

paddlefish

• ganoid scales (don’t form rings as they grow)• heterocercal tail• persistent notochord; centra absent or cartilage rings• large mouth, long maxilla attached at rear• open spiracle

sturgeon

Superorder Chondrostei

gar

• L.Permian-Recent, but mostly Juras. & Cretac.;• Abbreviated heterocercal tail, often symmetric caudal

fin;• Ganoid or cycloid scales• Single dorsal swim bladder, hydrostatic & respiratory;

physostomous;• No open spiracle• Vertebral centra often at least partly ossified,

constricting persistent notochord;• More modernized jaws (than Chondrosteans) - maxilla

shorter, free at rear; shorter mouth

Superorder Holostei

bowfin

Superorder Holostei

Superorder Teleostei

680 species of fish in the islands' waters.About 30% of these fish are endemic to the area .

Fish Diversity

Domino damsel

Trigger (Humu)

Dwarf moray

Porcupine

trumpetfishAchilles tang

White mouthed

morey

Latimeria

• Swim bladder modified to lungs• Paired appendages• May have given rise to terrestrial tetrapods• Bony head• Scales and teeth

Subclass Crossopterygii

Coelacanth

Thought to be extinct 80 million years ago Found in 1938 off the coast of the Comoro Islands

Coelacanth Anatomy

Subclass Dipnoi

Lungfish

                           

Acanthostega

Foot of Acanthostega had 8 digits

360 mya

Acanthostega

• First complete tetrapod with free digits- eight digits on each hand

• Retained “fishy” characters:- gills- tail fin- Partial connection between skull and

pectoral girdle- Labyrinthodont teeth- Lateral line- Ulna shorter than radius

Ichthyostega

Transition fossil from fw Crossopterygian to tetrapod

Ichthyosetga

• Much like Acanthostega, but…- stronger limbs; radius & ulna of equal length- no gills in adults- reduced number of skull bones

• Still retains panderichthyid-like skull, tail fin, labrinthodont teeth, lateral line

• First tetrapod known that was capable of life on land

Rana cancrivora

Class Amphibia

Amniotic Egg

Sea snake

Marine turtle

Marine iguanaSaltwater crocodile

Class Reptilia

Phylogeny of the Amniotes

Ancestral amniote

Anapsids DiapsidsTherapsids

Sauropsids Synapsids

Archaeopteryx

                                                                  

Ratites

Carinate

Class Aves

• The skeletons of birds have several adaptations that make them light, flexible, but strong.– The bones are honeycombed to reduce weight

without sacrificing much strength.

Dugong

manatee

Sea otter Whales & Dolphins

Polar bear

Seals & sealions

Class Mammalia

• hair or fur• mammary glands • endothermic

Evolution of the mammalian jaw and ear bones

Therapsid (mammal-like reptile)

Prototherians (Monotremes): Cretaceous-Recent • Egg-laying, aquatic predators on arthropods and worms• Milk oozes from the skin (no breasts). • Hair • Ear bones shift from lower jaw to skull during embryonic

development. • Electroreception

Metatheria (Marsupials): Cretaceous-Recent • Pouched mammals. • Born as gross little embryos.  Crawl into pouch, attach to

nipple, and develop. • Cretaceous ones were fairly opossum-like in their ecology. 

Later ones are more diverse.• Today, they are most diverse on Australia and South

America. • They share complex type of molar tooth shape with

Placental mammals.

Eutheria (Placentals): Cretaceous-Recent • Nourish their young internally with a placenta• Placentals give birth to offspring that are more "adult" like

and independent. Cretaceous ones were shrew-like in their ecology. 

• Later placentals are spectacularly diverse.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• The current hypothesis, based on molecular systematics, for the evolutionary relationships among eutherian orders clusters them into four main clades.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin CummingsFig. 34.33

Multiregional Model- modern humans evolved in parallel in different parts

of the world

Multiregional Model

African Origins Model- modern humans evolved in Africa and dispersed to

different parts of the world

Homo erectus

Homo sapiens

African Origins Model