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Chapter 1

Chapter One of Vertebrate Life Notes.docx

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Nancy Loadman

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1.1  The number of species of terrestrial vertebrates reached its maximum in the middle Miocene, 12-14 million years ago, and had declined since. Major Groups of Vertebrates  Two major groups are Amniotes and non-Amniotes.  Generally, amniotes are terrestrial and non-amniotes are aquatic, but there are a few exceptions.  Amniotes o Are animals that have an amnion which surrounds the embryo. This is one of three fetal membranes derived from the embryo. o Secondarily aquatic animals such as sea turtles and whales are exceptions to the terrestrial Amniote pattern. o Ancestral characters of this group includes scaled-covered skins without an insulating layer of hair of feathers, a simple kidney, simple lungs, and a heart without a septum dividing the ventricle. o During the Late Devonian Period Amniotes broke into Sauropsides (reptiles and birds) and Synapsids (mammals). o Sauropsid Amniotes  Contains turtles, scaly reptiles, crocodilians, and birds.  Extinct sauropsids include dinosaurs, pterosaurs (flying reptiles), ichthyosaurs, and plesiosaurs.  Turtles (Testudinia) ~209 species  Only vertebrates with pectoral girdle and pelvic girdle inside the ribs.  Tuatara, Lizards, and Snakes (Lepidosauria)  Scale-covered skin  Tuatara (2 species) only remnants of sphenodontida lineage.  Lizards (5000 species) and snakes (3015) species are at the peak of their diversity.  Alligators, and Crocodiles (Crocodilia) ~23 species  From same lineages as dinosaurs and birds (Archosauria).  Crocodilians range between less than a meter to 7 meters long.  Skin contains bones (Osteoderms) that act as armor.  Birds (Aves) ~9670 species  Lineage of dinosaurs that evolved for flight during the Mesozoic.  Feathers characteristic of extant species.  Dinosaur fossils with feather show they came before flight. o Synapsid Amniotes ~4800 species  Living mammals can be traced back to an origin in the late Paleozoic Era.  Most mammals are placental.  Contains 3 kinds of extant mammals: 1. Monotremes (Prototheria; Platypus and echidna)- hatchyoung from eggs. 2. Marsupials (Metatherians)- have a placenta, but have a shorter gestation period and must care for immature young. 3. Placentals (Eutherians)  Extincit Synapsids include pelycosaurs, therapsids, an multituberculates.  Non-Amniotes o Embryos enclosed by membrances produced by the reproductive tract of the female o Hagfishes and Lampreys (Myxinoidea and Petromyzontoida)  Elongate, limbless, scaleless, slimy and have no internal bony tissue.  Scavengers and parasites  Lack jaws and were therefore traditionally grouped as agnathans or cyclostomes.  Hagfishes are marine and live on the seabed. They have a skull, but no vertebral column.  Lampreys are mostly migratory (live in oceans and spawn in rivers). They have a simple vertebrae. o Sharks, Rays, and Ratfishes (Chondrichthyes)  "Cartilage- fish" -Cartilaginous skeletons  Extant sharks and rays form a group called Neoselachii  Sharks range 15cm to 10 meters.  Rays are dorsoventrally flattened and are frequently bottom dwellers that swim with the undulations of their pectoral fins.  Ratfishes or chimaeras consist of 33 species in the group Holocephalii ("whole head") which refers to the single gill cover that extends over all four gill openings.  They live on the sea floor and eat crustaceans and mollusks. o Bony Fishes (Osteichthyes)  "Osteo"=Bone and "ichthyes"= fish  Ray finned fishes (actinopterygians) consist of 27000+ species discovered 1. Chondrostei (bichins, sturgeons, and paddles fishes) 2. Neopterygii i.Gars (Lepisosteiformes, 7 species) ii.Bowfin ( one species, Arnia calva) iii.Teleostei (27000+ species including trout and bass)  Lobe-finned fishes / fleshy finned (Sarcopterygians)- 8 species  6 Species of lungfishes (Diproi)
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