The History of Vertebrates By Eric Przybyszewski Advanced Biology December 7, 2010 Section 3.4-3.7 p.671

In The Book Chapter 34 Sections 34.1- 34.7 With focus on 34.5 – 34.7

What is a Vertebrate? A vertebrate: Any animal with a backbone Backbone meaning a segmented spinal column Living examples: reptiles, fish, birds, amphibians, mammals, Humans 52,000 species of vertebrates, 1 million insect species Largest vertebrate blue whale, at 100,000 kg Origins traced back about 540 mya

Origins of Vertebrates Chordates: Simple bilaterally symmetrical animals Four features Post anal tail Pharygeal gill slit Notochord Hollow dorsal nerve cord Craniates: Chordates with a head Name derived from cranium (skull) Most well known: hagfish

Origins of Vertebrates Vertebrates: craniates with a backbone More complex nervous system Restricted to marine environments Examples: jawless armored fish Gnathostomes: vertebrates with a jaw Found up to 470 mya Chondrichthyans: cartilaginous fish Sharks, rays etc. Ray-finned fish Most common living fish Tuna, trout, bass, herring Lobe-fins Evolved during the Devonian period Today only three lineages that survive

Tetrapods Tetrapods: gnathostomes with limbs and feet Name: “four feet” 360 mya fins of lobe-fins evolved into limb and feet First vertebrates to came ashore Amphibians Ancestor to all land vertebrates

Terapods 360 mya Coastal wetlands home to many lobe-fins Most were shallow, oxygen-poor, water Caused them to use lungs and breath air Forced them to drag themselves across the floor Increasing the strength in fins and developing the muscles that would become limbs Muddy bottom could be pushed against and so feet developed

Terapods These earliest tetrapods were not terrestrial The earliest confirmed is some 20 million years later They may have spent very brief periods out of water and would have used their new legs to pull their way through the mud

Marine Mammals Not all terapods changed Some left shallow inter seas for the oceans Most evolved partially, fins, with leg bones now were again used as fins. Examples All whales Dolphins Manatee

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Living Tetrapods Amphibians Oldest known land group Name means “two lives” Most common Salamanders with 4,800 different species Not all live in both water and on land Some strictly aquatic Some strictly terrestrial Examples: frogs, salamanders, and caecilians

Amphibians Provide a look into prehistoric life Locomotion Predation Powerful hind legs (frogs) Legless, burrowing Predation Carnivores (insectivorous), omnivores, herbivores Defense mechanisms Mucus, distasteful of poisonous Camouflage Metamorphosis Example-Frogs Egg, to Larva (tadpole), to Adult Adapted climate Organisms adaption's speak to the current climate Reproduction External fertilization Mating behaviors

Amniotes Terpods that have a terrestrially adapted egg Late Devonian period Includes reptiles, birds and mammals The major difference is the egg

Amniotes The terrestrial egg Hard shell Albumen Protection Albumen Padding Extraembryonic membranes Padding and protection Amniotic cavity Nutrients and suspension Yolk Main source of nutrients Embryo Developing organism

Permanent Land Dwelling Amniotes The terrestrial egg allowed for Permanent Land Dwelling Led to internal fertilization Led to the Reptiles, Dinosaurs and Birds Without egg mammals may not be here

Amniotes Became terrestrially adapted Early examples True lungs with a rib cage Enough oxygen in the atmosphere Less permeable skin More elevated stance Capable of living in much drier environments Became herbivores, Carnivores, and Omnivores Grew larger in size Early examples Little fossil evidence

Reptiles Oldest well documented amniotes Includes Lizards, snakes, turtles, crocodilians Traced back to 350 mya Unique characteristics Have scales (protein kertin) Waterproof and protective Rely on lungs alone for gas exchange Not turtles Lay hard shelled eggs on land Internal fertilization “Cold Blooded” Ectothermic absorb heat Not birds

Reptiles The Major groups Parareptiles Diapsids First reptiles 300 mya Lepidosaurs Lizards, snakes, marine reptiles (plesiosaurs and ichthyosaurs) Archosaurs Crocodilians Petroasaurs (first tetrapods in the air) Dinosaurs

Reptiles…

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Dinosaurs Covers many animals Two main Branches Ranged from the size of pigeons to massive 45m (148ft) long quadrupeds Two main Branches Ornithischian (bird hipped) Herbivores, many had defenses Iguanodon, Stegosaurus, Triceratops Saurischian (lizard hipped) Sauropods Apatosaurus, Diplodocus, Brachiosaurus Theropods (birds later) Allosarus, Deinonychus, T-rex, Velociraptor

Dinosaurs From 248 mya to 65 mya Dinosauria is one of the most successful superorders in the earth’s history 9,000 different species Much debate Extinction Mobility Parental abilities Surviving lineages Lepidosaurs Tuatara Squamates Lizards and Snakes Birds

Lepidosaurs Surviving lineages Tuatara Snakes Lizards Lizard like Traced back 220 mya Snakes Legless, very successful Small and Carnivores Some poisonous Highly evolved sense of smell Lizards Most numerous and diverse reptiles, (excluding birds) alive Most are small and Carnivores Komodo Dragon

Crocodilians Alligators and Crocodiles Archosaur lineage back to late Triassic First were small quadrupeds with slender legs Over time later species became more and more suited to aquatic environments and grew in size Largest known is Super Croc. Others 10 m or more in length

Birds Decedents of the Theropod dinosaurs Technically reptiles Lost almost every resemblance to reptiles 8,600 different species Endothermic From Archosaurs came about during the Jurassic Flight gives several advantages Enhances hunting, scavenging Easy escape from predators Several different physical characteristics that set birds apart and allow most of them to fly No urinary bladder Most only have one ovary Small gonads All living birds are toothless Light skull Hallow bones Wings, feathers (made of Kertin) Several modern bird species

Origin of Birds From the bipedal Saurischians Archaeopteryx Theropds Raptors ex. Velociraptor Archaeopteryx Earliest known bird at 150 mya Feathered with wing claws Capable of powered flight but keep many dinosaur like features Weak flyer but still it could fly Other fossils show similar types birds but none are as complete

Mammals Synapsids Amniotes, the synapsids, that produce milk Nonmammalian have no hair Temporal fenestra, hole behind the eye socket on each side Large herbivores or carnivores Amniotes, the synapsids, that produce milk Mammary glands Hair, layer of fat under the skin Live birth Larger brain Long duration of parental care Very social Endothermic Higher metabolism rate First appeared almost 200 mya During Jurassic Never became larger then modern day shrews Kept hidden by reptile’s dominance After the 65 mya mass extinction Mammals started to dominate Became large predators and herbivores plus flying and aquatic species

Mammal Skull Example of Biarmosuchus Jaw and it make up. Note the difference between the ears in a reptile and a mammal.

Primates Eutherians Physical traits Living primates Placental mammals Feet and hands adapted for grasping Opposable thumbs Large brain Short jaws, flat face Living primates New World Monkeys Prehensile tail Nostrils that open to the side Old world Monkeys No perhensile tail Nostrils that open down New World Old World

Review A vertebrate: Any animal with a backbone Backbone meaning a segmented spinal column Terapods: have limbs, feet, digits Adoptions for on land Amphibians Amniotes The terrestrial egg: allowed for? Reptiles Diapsids

Review Dinosaurs Crocodilians Birds Mammals From Theropds Ornithischian Saurischian Surviving lineages Crocodilians Birds From Theropds Archaeopteryx Mammals Skull Primates

Review Paleontology ends First Primates Mass extinction First Birds First Mammals Dinosaurs First Reptiles Amphibians Life on land First Vertebrates Life Begins

Review What is a vertebrate? Oldest land group? First bird? Any animal with a backbone Backbone meaning a segmented spinal column Oldest land group? Amphibians First bird? Archaeopteryx Largest Crocodilian? Super Croc. Two types of living monkeys? New and Old world

Review Chapter overview P. 707,708 Sections 34.1 - 34.7 with focus on 34.5 – 34.7 Try Self Quiz P. 708 #1-7 Paleontology