Lets start 390 million years ago…During the Devonian Period, there were many

creatures living in the oceans (some on their way to becoming the true bony fish of today!)

PlacodermsName means “plated skin”First seen 390 million years agoExtinct 345 million years agoHad true jawsMany were small bottom dwellers, but many

more were bottom dwelling predatorsArmor plates on their skin

A Placoderm

Next came the Chondrichthyes

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Chondrichthyes

ChondrichthyesFirst seen 375 million years agoThey’re still around todayIncludes sharks and skatesSharks are sometimes called “living fossils”Developed cartilaginous skeletons

Chondrichthyes of old….

OsteichthyesModern ‘bony fish’First appeared 395 million years agoRay-finned fish of today are still the dominant

fish groupTrue bones

Osteichthyes

Osteichthyes branched into… Actinopterygii…Kingdom:Animalia

Phylum:ChordataSuperclass:OsteichthyesClass: Actinopterygii

Ray-finned bony fish Fins are webs of skin supported by bony or

horny spines. They are the dominant aquatic vertebrates

today, making up about half of all vertebrate species known

… and SarcopterygiiKingdom: Animalia

Phylum: Chordata

Superclass: Osteichthyes

Class: Sarcopterygii

SarcopterygiiName means “fleshy finned fishes”First appeared 385 million years agoAncestors of land vertebrates!Internal nostrils, fleshy fins and cosmoid

scales

1. What does this mean that sharks are “living fossils”?

Sea to Land Transition

Sea to Land TransitionScientists think that the major cause for

marine life moving on to land was a lack of oxygen in the water.

There was also fierce competition for food in the oceans.

Also, at this time insects were becoming very plentiful on land.

2. What do you think would be required for this sea to land transition to occur?

Tiktaalik roseae

Tiktaalik roseae

Tiktaalik roseaeFirst seen 375 million years agoLarge aquatic predator with a flattened head and

bodyScientists think that Tiktaalik lived on the bottom

of the ocean in shallow waterTiktaalik might have been able to come out of the

water for brief periods of timeSkull, neck, ribs and limbs are similar to the

earliest limbed animalsHad fish-like features such as scales and fin rays

Tiktaalik roseaeDiscovered on Ellesmere Island, Canada in

2004Name means “large freshwater fish” in

Inuktituk

Tiktaalik roseae