Reptiles Non Avian Diapsid Amonites Evolutionary Perspective 350

Reptiles Non Avian Diapsid Amonites

Evolutionary Perspective • 350 million years ago during the Carboniferous period primitive Amnoites emerged who developed into reptiles, birds and mammals • Amniota (amnion)- membrane around a fetus, was an egg adapted for life on land • Amniotic eggs- extraembryonic membranes that protect the embryo from dessication, cushion, promote gas transfer and store waste material • surrounded by a tough leathery or hard shell

Diapsids 4 living orders • Order Testudines- Turtles approx 300 living species • Characterized by a bony shell, limbs articulating internally to ribs and a keratinized beak (no teeth) • Carapace- dorsal portion of shell, formed from fusion of vertebrae, ribs, bones and skin. Keratin covers bone of the carapace • Plastron- Ventral portion of shell, formed from bones of pectoral girdle, dermal bone and keratin

Painted Turtle

Green Sea Turtle

Sea Turtle Shell interior

Sea Turtle with Barnacles

Aldabra Giant Tortoise

Turtles • On some shells the plastron has flexible areas which allows the shell openings to close when the turtle withdraws • S shaped neck vertebrae allow head to be withdrawn • Turtles have long life spans 14 years or more • Tortoises (terrestrial) can live 100 years • Oviparous- lay eggs which hatch outside mother, young are independent of parents • Slow growth rates make turtles vulnerable to extinction

Order Crocodylia • Alligators, crocodilians, gavials and caimans • Characterized by triangular eye orbits, openings in skull in front of eye and laterally compressed teeth • Have not changed much in 170 million years • Elongated snout used to catch food • Nostrils at tip of snout, eyes high on head • Air passages lead to back of mouth, sealed from throat by flap of tissue

Crocodylia • Muscular and elongated tail used for swimming • Teeth for seizing prey, swallow prey whole • If prey too large, bite and spin body to tear off large chunks • Swallow rocks as abrasives to help break down food • Oviparous, nesting behavior, parental care

Alligator

Alligator

Mother transporting Young

Crocodile

Crocodile Running

Gavialovy

Order Sphenodontida • Tuatarans- distinguished from other reptiles by two rows of upper teeth and a single row on lower jaw, produce a shearing bite • Unchanged in 200 million years, Mesozoic period • Found only in New Zealand • Oviparous, use underground burrows

Tuatara

Parietal Eye

Order Squamata, 3 suborders • Suborder Sauria- Lizards- 4, 500 species- two pairs of legs and jaws unite, legless lizards still have sternum and pectoral girdle • Vary in length from few cm to 3 meters • Most are oviparous, some ovoviviparous, and few viviparous • Usually hide for protection under rocks, live in trees, some burrowers

Lizards • Geckos- semitropical areas, short and stout bodies, nocturnal, large eyes and adhesive disks on digits to climb trees, walls • Iguania- robust bodies, short necks, distinct heads, includes marine iguanas of galapagos, and flying dragons of southeast Asia • Chameleons- Africa and Asia, adapted to arboreal life, long sticky tongue, ability to change color • Gila Monster, Mexican bearded lizard- venomous lizards, southwest U. S. , Mexico, venom released from grooves in teeth

Gecko

Leopard Gecko

Iguana

Marine Iguana

Marine Iguana

Flying Dragon, Iguana

Chameleon

Chameleon

Chameleon

Gila Monster

Suborder Serpentes • Snakes- 2, 900 species, about 300 species venomous • 30, 000 people die worldwide each year, 9 -15 die in U. S. due to lack of emergency health care • Snakes have elongate bodies and lack limbs, vestigial appendages in pythons and boas • Skeleton may have 200 vertebrae and pairs of ribs, joints between vertebrae very flexible

Snake Venom • Gene analysis found that 24 types of snake venom all evolved from a single ancestral gene • Snake venom is highly modified saliva • Venoms are a mixture of proteins, enzymes and other substances with toxic and lethal properties • Components of snake venom have very specific effects- blood coagulation, reducing blood pressure, blocking nerve impulses, blocking muscle impulse and digestion

Snakes • Skull adaptations to swallow prey whole • Upper and lower jaws loosely joined, move independently • Elongation (narrowing) of body resulted in loss of left lung, displacement of gall bladder, right kidney and gonads • Most snakes oviparous, many vipers, boas and cobras give birth to live young • Snakes evolved 135 mya, Cretaceous period

Diamond back Rattlesnake

Snake Bite Hemotoxin Africa

Rattle Snake Bite Hemotoxin

Python

Python Swallowing

Python with Alligator protruding from midsection

Snake Swallowing Egg

Snake Evolution • Originally snakes were thought to have evolved to burrow but recent findings of 90 million year old fossils indicate snakes were aquatic or lived in densely tangled vegetation • Elapsids- fixed fangs- Cobra, mambas, Kraits, taipans, and coral snakes. Neurotoxin produces paralysis of lungs and heart • Viperid- copperhead, rattlesnake, water moccasin(cottonmouth), Bushmaster and ferde-lance. Retractable fangs hemotoxin • 24 kinds of snake venom known to exist

Coral Snake

Reptile Skin • Reptilian skin is thick, dry, keratinized • Scales modified for various functions, belly scales • Ecdysis- shedding skin(scales) as body grows • Phermones-secretions function in sex recognition and defense • Chromatophores-dermal cells produce cryptic coloration, mimmicry, aposematic and used for thermal regulation

Suborder Amphisbaenia • Worm Lizards- 135 species, specialized burrowers, live in Africa, south America, Caribbean and Midwest U. S. • Some legless, skull wedge shaped • Single median tooth in upper jaw, forms nipper with two lower teeth • Skin has ring like folds used to bulge out against burrow walls • Move easily forward and backward, feed on worms

Worm Lizard

Worm Lizard

Support and Movement • Reptilian skeleton inherited from ancient Amphibians • Highly ossified, very strong • Secondary Palate- plate of bone separates nasal passages from mouth • Have Atlas and axis vertebrae at base of skull • Ribs may be highly modified, turtles, flying dragon • Snake ribs have a muscular connection to belly scales

Support and Locomotion • Autotomy- caudal vertebrae in many lizards contain a vertical fracture plane to sever tail • Primitive reptiles walk similar to salamanders • Modern reptiles have longer slender legs, hold body higher • Many prehistoric reptiles were bipedal which freed front appendages to adapt for capturing prey and flight

Nutrition and Digestion • Most reptiles carnivores, turtles may be carnivores, herbivores or omnivores • Tongues of some lizards and Tuatara sticky to capture prey • Chameleons tongue exceeds body length • Reptiles possess peg teeth some angled back to aid in holding and swallowing prey