Dinosaur and Reptile Classification traditional classification scheme 1

Dinosaur and Reptile Classification traditional classification scheme 1. Subclass Anapsida (cotylosaurs, turtles) 2. Subclass Synapsida (pelycosaurs, mammallike reptiles; Dimetrodon) 3. Subclass Euryapsida (marine reptiles; ichthyosaurus & Plesiosaurs) 4. Subclass Archosauria (ruling reptiles) 5. Subclass Lepidosauria (scaly reptilesmosasaurs)

Temporal Fenestre

Cladistic Scheme

Dinosaurs: A General Overview • "age of reptiles" mid-late Triassic (250 mya)- Cretaceous (180 mya) • Thecodont ancestry • size: initially small--->huge

skeleton • hollow bones • bipedalism • unique pelvic structure (triradiate & quadraradiate pelvic structures) • tail large; carried off the ground as a counterweight

"The Great Extinction" • occurred at the end of the Mesozoic (65 mya) • • > 50% of all species became extinct • all tetrapods > 10 kg & all marine reptiles went extinct • ~ 90% of all protists went extinct • extinctions occurred over a period of 10, 000 -100, 000 years or immediately

extinction hypotheses • climatic change- equitability and seasonality changed • impact with extra terrestrial body • exotic species exchange via land bridges

Modern Reptiles • diversity: 6000 species • turtles (anapsid reptiles) • snakes & lizards/squamates (lepidosaurs) • crocodilians • tuatara (Spenodon) • amniotes • ectotherms (Their blood is NOT cold!)

Integument • epidermal scales • dry; water proof & mechanical barrier • chromatophores • ecdysis = molting/shedding • claws • few skin glands

Skeleton • one occipital condyle • ossified skull • temporal openings- anapsid, diapsid, synapsid • secondary palate in some

Circulation/Respiration • three or four chambered heart • no diaphragm • lungs

Excretory System • metanephric kidneys • uric acid & urea

Feeding • herbivores & carnivores • venom glands • Jacobson's organ

Reproduction • internal fertilization • oviparous, ovo-viviparous, & viviparous • hemipenis • parthenogenesis

Chelonia (Turtles) • bizarre skeleton • ribs fused & outside limb girdles • carapace • plastron • dermal scales • ridged beak- no teeth • true penis • long lived & long generation times • oviparity • temperature determine sex & survival • no parental care

Squamata (snakes & lizards) • diapsid lineage • second largest tetrapod group • paired copulatory organ • protrusible tongue • Jacobson's organ

Lizards (Suborder Lacertia) • 3300 species; (3 cm- 3 m); 75 Kg • most are small (80% < 20 grams) • differences from snakes: • eyelids -vs- fused spectacle; swivel eyes and color vision • external & middle ear -vs- none • fused -vs- unfused mandibular symphysis • limbs & girdles • tail autotomy • zygodactylous feet • prehensile tails • protrusible tongue

Lizard Families • Iguanidae- North & South America • Scincidae- cosmopolitan • Teiidae- North & South America

Snakes (suborder Serpentes) • • limblessness reduction or loss of left lung loss of external and middle ear No eyelids • Family Colubridae • Family Elapidae • Family Viperidae

Snake Venom • Hemotoxic- Crotalus, Agkistrodon • Neurotoxic- Elapidae • Symptoms & Treatment

Crocodylia • survivors of the anthracosaur radiation • ectotherms • 4 -chambered heart • Family Aligatoridae • Family Crocodylidae • Family Gavialidae