Vertebrate Evolution Torsten Bernhardt Redpath Museum, McGill University This teaching resource was made possible with funding from the PromoScience programme of NSERC. McGill University 2010
History of the Earth Origins of Bacteria Origins of Eukaryotes Phanerozoic 4.6 3.8-3.5 1.5 0.542 0 (Billions of years) (Millions of years) Paleozoic Mesozoic Cenozoic
Chordates http://associationpourlasanteetlenvironnement.skynetblogs.be/ archive-day/20060514 Pikaia http://media-2.web.britannica.com/eb-media/54/4054-004-f5eb3891.jpg Tunicates (sea squirts)
The First Fish? http://permian.files.wordpress.com/2007/05/vida-antes-de-los-dinosaurios-02.jpg 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 -Skeleton is made of cartilage instead of bone -Don t fossilize well -Are thought to have evolved from placoderms http://www.divephotoguide.com/user/181/gallery/183/ Manta ray http://templecuttingedge.files.wordpress.com/2009/06/great-white-shark-1.jpg Great white shark Chimera http://www.mcaorals.co.uk/photos/deep%20sea%20 Fish/chimaera_fish1.jpg
Cartilaginous Fish (Chondrichthyes) (ii) http://www.karencarr.com Stethacanthus (~360 Mya) Megalodon (~1.5 mya) http://data3.blog.de/media/606/2129606_fb5a2adfe5_m.jpeg
Bony Fish (Osteichthyes) http://ricomoss.files.wordpress.com/2009/04/big-fish.jpg Nile Perch Betta http://home-aquarium-store.co.uk/wp-content/uploads/2009/01/beta-fish-pictures.jpg
Bony Fish Ray-finned Fish (Actinopterygii) http://www.gnb.ca/0078/hey_kids/images/brooktrout.jpg -25 000 species, 99% of all fish today -Fins are supported by bony rays Clown fish http://www.free-mobilewallpapers.com/wallpapers/iphone-wallpaperclown-fish.jpg Brook trout Homalacanthus
Bony Fish Lobe-finned Fish (Sarcopterygii) Eusthenopteron -Fins have bones and muscle -Live on the bottom -Not especially diverse, as fish Coelacanth http://www.itsnature.org/sea/images/article-images/coelacanth.jpg
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 http://higheredbcs.wiley.com/legacy/college/levin/0 471697435/chap_tut/images/nw0276-nn.jpg 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 http://www.foundalis.com/bio/cre/icht hyostega.jpg Ichthyostega -Early amphibians didn t look like modern amphibians -Three-chambered heart -Had lungs, but also breathed through their skin -Were tied to water for reproduction -Dominant predators in the Carboniferous http://darwiniana.org/acanthostega1.jpg Acanthostega http://dic.academic.ru/pictures/wiki/file s/101/eryops1db.jpg Eryops
Amniotes Outer envelope Yolk Inner envelope http://en.wikipedia.org/wiki/fil e:chroniosuchusdb126.jpg Amphibian egg Chroniosuchus, which may be an ancestor of amniotes http://kentsimmons.uwinnipeg.ca/16cm05/1116/34-19-amnioticegg-l.gif Amniote egg -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://lesdinos.free.fr/dimetrodon.jpg http://9thestate.com/images/gorgonopsid.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 -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 http://www.dkimages.com/discover/pre views/1519/11653653.jpg http://www.kidsdinos.com/images/dino saurs/mesosaurus1139704078.jpg Mesosaurus, one of the first reptiles to return to the sea Coelurosauravus, a gliding reptile http://mrugala.net/nature/animaux/dinos aures/coelurosauravus.jpg
Crurotarsi -The group that today includes crocodiles -Ruled the world in the Triassic, after the mammal like reptiles were severely affected by the Permian extinction -Were themselves severely affected by the extinction event at the end of the Triassic Postosuchus http://www.cryptomundo.com/wp-content/uploads/postosuchus.jpg
Other Reptiles http://naturescrusaders.files.wordpress.com/2009/02/gex_gr een-sea-turtle.jpg http://petzotics.com/lizards%20image s/tokay_gecko.jpg http://naturescrusaders.files.wordpress.com/2009/04/rhabdo phis_tigrinus_06toad.jpg Green sea turtle Snake Tokay gecko Tuatara http://mudpuddle.files.wordpress.com/ 2009/02/henry.jpg
Dinosaurs -Were around for 160 million years -Two groups, based on hip structure -May have been warm blooded -Advanced features bones, gait Triceratops Gorgosaurus
Dinosaurs http://sciencejunkies.com/media//2009/03/blue_whale_size_comparison.gif http://bydirigible.files.wordpress.com/2008/05/dinosaurs.jpg
Not Just Dinosaurs! (i) http://www.flashweb.gr/turtle2008/photos/arch.jpg Turtles http://archeowiesci.files.wordpress.com/20 07/11/sarcosuchus_and_nigersaurus.jpg http://blogs.nationalgeographic.com/blogs/news/chi efeditor/world%27s-biggest-snake-picture.jpg Snakes Crocodylimorphs Lizards Tuatara
Not Just Dinosaurs! (ii) http://www.linternaute.com/science/biologie/diaporam as/05/dinosaures/images/pteranodon.jpg Ichthyosaurs http://www005.upp.sonet.ne.jp/jurassicgallery/ichthyosaurs.jpg Pterosaurs - the first flying vertebrates http://www.search4dinosaurs.com/miller_mosasaur.jpg Mosasaurs Plesiosaurs http://www.discoverynews.us/discovery%20museum/creatu resfromthedeep/creaturesimages/plesiosaur_4_large.jpg
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
http://centroufologicotaranto.files.wordpress.com/2009/10/archaeopteryx.jpg http://desireestanley.files.wordpress.com/2009/03/blue-birdmissouri.jpg Archaeopteryx Birds -Evolved from dinosaurs; specifically, the meat-eating deinonychosaurs, which includes Dromaeosaurus -Are technically dinosaurs -Feathers evolved before birds did; T. rex may have been fuzzy -May have outcompeted the pterosaurs and helped drive them to extinction -The second vertebrate group to fly
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) http://s3.amazonaws.com/lcp/first_corner_of_a nita_bokeron/myfiles/elephant.indricotherium.h uman.jpg http://upload.wikimedia.org/wikipedia/commons/th umb/7/7a/panochthus_frenzelianus.jpg/800px- Panochthus_frenzelianus.jpg Indricotherium Glyptodont http://www.bbc.co.uk/science/seamonsters/factfile s/images/arsinoitherium1.jpg Arsinoitherium http://hiddenway.tripod.com/images/creatures/smilodon.jpg Saber-toothed cat Leptictidium http://www.pts.org.tw/~web02/beasts/factfiles/primary_ff_displays/l eptictidium_1.jpg
Mammals Take Over (ii) http://fascinatingly.com/wp-content/uploads/2009/03/humpback_whale.jpg Humpback whale Bat http://www.dumbaaldum.org/images/picsounds/letter-h/hand.jpg http://www.treehugger.com/bat-organic-coffee-001.jpg