Vertebrate Evolution (PDF)

Torsten Bernhardt Redpath Museum, McGill University

This teaching resource was made possible with funding from the PromoScience programme of NSERC.

Origins of Origins of Bacteria Eukaryotes Phanerozoic

4.6 3.8-3.5 1.5 0.542 0 (Billions of years)

(Millions of years) Paleozoic Mesozoic Cenozoic Chordates F5EB3891.jpg 004 - - media/54/4054 day/20060514 - - 2.web.britannica.com/eb - http://associationpourlasanteetlenvironnement.skynetblogs.be/ archive

Pikaia http://media Tunicates (sea squirts) The First Fish? 02.jpg - dinosaurios - los de - - antes - http://permian.files.wordpress.com/2007/05/vida

Haikouichthys Agnathans: Jawless Fish (i)

Ostracoderms -armoured, jawless fish -used gills only for respiration -no paired fins, so probably poor swimmers

Endeiolepis aneri Agnathans: Jawless Fish (ii) http://www.ne.jp/asahi/fragi/ragi/gallery/cephalaspis.html Cephalaspis

Ostracoderms went extinct in the Devonian, most likely due to the placoderms (who we’ll get to in a minute…) Agnathans: Jawless Fish (iii) http://www.utsc.utoronto.ca/~youson/images/lamprey.jpg

A modern agnathan: the lamprey Placoderms: Jaws Evolve (i)

-Still armoured -Jaws are a major advantage -First live birth -Paired fins http://www.pangaeadesigns.com/_gra phics/page/retail/large/bothriolepis.jpg

Bothriolepis Placoderms: Jaws Evolve (ii) http://www.dinotime.de/pictures/dunkleosteus.jpg

Dunkleosteus http://www.nmnh.si.edu/rtp/students/2006/images/paleo_day72.jpg

No teeth Cartilaginous Fish (Chondrichthyes) (i)

-Sharks, skates, rays, chimeras Fish/chimaera_fish1.jpg http://www.mcaorals.co.uk/Photos/Deep%20Sea%20 -Skeleton is made of cartilage instead of bone -Don’t fossilize well -Are thought to have evolved from placoderms 1.jpg - shark - white - Chimera http://www.divephotoguide.com/user/181/gallery/183/ http://templecuttingedge.files.wordpress.com/2009/06/great Manta ray Great white shark Cartilaginous Fish (Chondrichthyes) (ii) http://www.karencarr.com http://data3.blog.de/media/606/2129606_fb5a2adfe5_m.jpeg Stethacanthus Megalodon (~1.5 mya) (~360 Mya) Bony Fish (Osteichthyes) http://home - aquarium fish.jpg - store.co.uk/wp - content/uploads/2009/01/beta - - http://ricomoss.files.wordpress.com/2009/04/big fish - pictures.jpg Nile Perch Betta Bony Fish – Ray-finned Fish (Actinopterygii)

-25 000 species, 99% of all fish today clown wallpapers.com/wallpapers/iphone - http://www.free - -Fins are supported by bony rays fish.jpg - mobile - wallpaper - Clown fish http://www.gnb.ca/0078/Hey_kids/images/BrookTrout.jpg Brook trout Homalacanthus Bony Fish – Lobe-finned Fish (Sarcopterygii) images/Coelacanth.jpg - http://www.itsnature.org/Sea/images/article Eusthenopteron Coelacanth

-Fins have bones and muscle -Live on the bottom -Not especially diverse, as fish From Fish to Amphibians

We think that amphibians evolved from sarcopterygian (lobe-finned) fish. Why is this?

One group of sarcopterygians, the osteolepiforms, had nostrils that led to an opening in the roof of its mouth. This allowed air to pass into the mouth and then to paired swim bladders (similar to our lungs).

Lungfish, which are modern sarcopterygians, can crawl over land from one water body to another.

The sturdy fins of the sarcopterygians have bones much like those in our limbs. Other anatomical features, such as skull bones and teeth, also point to a relationship. From Fish to Amphibians nn.jpg http://higheredbcs.wiley.com/legacy/college/levin/0 - 471697435/chap_tut/images/nw0276 Amphibian limb (left) and lobe-finned fish fin (right) http://www.hmnh.org/galleries /deadanimalblog/pf_tiktaalik.j pg

Early amphibians had as many as eight toes; this was eventually reduced to five, or four Amphibians

-Early amphibians didn’t look like modern amphibians -Three-chambered heart -Had lungs, but also breathed through their skin http://www.foundalis.com/bio/cre/Icht hyostega.jpg Ichthyostega -Were tied to water for reproduction -Dominant predators in the Carboniferous

http://darwiniana.org/acanthostega1.jpg Eryops Acanthostega http://dic.academic.ru/pictures/wiki/file s/101/eryops1db.jpg Amniotes

Outer envelope L.gif Yolk Amphibian - AmnioticEgg

Inner envelope egg 19 - - http://kentsimmons.uwinnipeg.ca/16cm05/1116/34 http://en.wikipedia.org/wiki/Fil e:ChroniosuchusDB126.jpg Chroniosuchus, which may be an Amniote egg ancestor of amniotes

-Amniotes’ eggs allowed them to reproduce away from water and expand to drier areas -They diverged into two lineages: one would eventually become mammals, the other would become reptiles and birds Mammal-like reptiles (Synapsids) http://9thestate.com/images/gorgonopsid.jpg http://lesdinos.free.fr/dimetrodon.jpg

Dimetrodon Gorgonopsids

-Ancestors of true mammals -Regulated their temperature -Different types of teeth -Very successful until the end of the Permian The Permian Extinction -The most severe extinction event in the Earth’s history -May be related to the Siberian Traps, the largest volcanic eruptions on Earth -96% of species in the oceans go extinct, 70% of vertebrates on land go extinct, 99.5% of all living creatures die -The mammal-like reptiles are severely affected http://www.lpi.usra.edu/education/timeline/gallery/images/053.jpg ! Reptiles views/1519/11653653.JPG http://www.dkimages.com/discover/pre -Many different groups -Scales, “3.5”-chambered heart -Almost all lay eggs -Extremely successful in the Mesozoic (which is known as the Age of Reptiles) Scutosaurus aures/Coelurosauravus.jpg http://mrugala.net/Nature/Animaux/Dinos http://www.kidsdinos.com/images/dino saurs/Mesosaurus1139704078.jpg

Mesosaurus, one of the Coelurosauravus, a first reptiles to return to gliding reptile the sea Crurotarsi

-The group that today includes crocodiles -Ruled the world in the Triassic, content/uploads/postosuchus.jpg after the mammal–like reptiles were severely affected by the Permian extinction - http://www.cryptomundo.com/wp -Were themselves severely affected by the extinction Postosuchus event at the end of the Triassic Other Reptiles s/Tokay_Gecko.jpg http://petzotics.com/Lizards%20Image turtle.jpg - sea http://naturescrusaders.files.wordpress.com/2009/02/gex_gr een - Green sea turtle Tokay gecko http://mudpuddle.files.wordpress.com/ 2009/02/henry.jpg http://naturescrusaders.files.wordpress.com/2009/04/rhabdo phis_tigrinus_06toad.jpg Snake Tuatara Dinosaurs

-Were around for 160 million years -May have been warm blooded -Two groups, based on hip structure -Advanced features – bones, gait

Triceratops Gorgosaurus Dinosaurs http://bydirigible.files.wordpress.com/2008/05/dinosaurs.jpg http://sciencejunkies.com/media//2009/03/blue_whale_size_comparison.gif Not Just Dinosaurs! (i) http://www.flashweb.gr/turtle2008/photos/arch.jpg http://archeowiesci.files.wordpress.com/20 07/11/sarcosuchus_and_nigersaurus.jpg Turtles

Crocodylimorphs picture.jpg - snake - biggest - Lizards

http://blogs.nationalgeographic.com/blogs/news/chi efeditor/world%27s Tuatara Snakes Not Just Dinosaurs! (ii) - http://www005.upp.so net.ne.jp/JurassicGallery/Ichthyosaurs.jpg Ichthyosaurs http://www.linternaute.com/science/biologie/diaporam as/05/dinosaures/images/pteranodon.jpg resFromTheDeep/CreaturesIMAGES/Plesiosaur_4_large.jpg http://www.discoverynews.us/DISCOVERY%20MUSEUM/Creatu

Pterosaurs - the first flying vertebrates http://www.search4dinosaurs.com/miller_mosasaur.jpg Plesiosaurs Mosasaurs True Mammals

-Evolved from the synapsids (mammal-like reptiles) -Vaguely rodent-like, small -Showed up not too long after the dinosaurs -Didn’t amount to much in the Mesozoic; lawnmower ecology http://piclib.nhm.ac.uk/piclib/webimages/0/1000/400/1461_med.jpg Birds

-Evolved from dinosaurs; specifically, the meat-eating deinonychosaurs, which includes Dromaeosaurus -Are technically dinosaurs http://centroufologicotaranto.files.wordpress.com/2009/10/archaeopteryx.jpg -Feathers evolved before birds did; T. rex Archaeopteryx may have been fuzzy -May have outcompeted the pterosaurs

bird - and helped drive them to extinction -The second vertebrate group to fly missouri.jpg - http://desireestanley.files.wordpress.com/2009/03/blue Cretaceous Extinction http://life7.beyondgenes.com/images115/theend.JPG

-Ends the reign of the dinosaurs -Flying and swimming reptiles also go extinct -Many other groups suffer as well -Mammals step into the empty niches ! Mammals Take Over (i) umb/7/7a/Panochthus_frenzelianus.jpg/800px http://upload.wikimedia.org/wikipedia/commons/th Panochthus_frenzelianus.jpg - http://s3.amazonaws.com/lcp/first_corner_of_a nita_bokeron/myfiles/elephant.indricotherium.h uman.jpg Indricotherium Glyptodont eptictidium_1.jpg http://www.pts.org.tw/~web02/beasts/factfiles/primary_ff_displays/l http://hiddenway.tripod.com/images/creatures/smilodon.jpg http://www.bbc.co.uk/science/seamonsters/factfile s/images/arsinoitherium1.jpg Arsinoitherium Saber-toothed cat Leptictidium Mammals Take Over (ii) http://www.treehugger.com/bat - organic - coffee - 001.jpg

Bat content/uploads/2009/03/humpback_whale.jpg - sounds/letter http://www.dumbaaldum.org/images/pic - h/hand.jpg http://fascinatingly.com/wp Humpback whale -