Exam 2 - V & D

tetrapods

• first appeared in the late Devonian and underwent significant radiation in the carboniferous

• first tetrapods spent most time in shallow water

• characterized by a chiridium

amphibians : salamanders, frogs, caecilians

• all require water for reproduction and development

• anaminiotic eggs must be laid in water or very moist enviroment

• embryos lack amnion

• aquatic gill breathing larval stage most often followed by terrestrial lung breathing adult stage

• lungs and skin used as adult respiratory organs

• skin is most often scaleless

• ectothermic

• heart with 2 atria and 1 ventricle

• pedicellate teeth with pleurodaunt attachment

salamanders

least specialized, elongated body, 2 pairs of limbs, maintains tail throughout life

frogs

highly specialized, lose tail as adult, elongated hind limbs, caudal vertebrae fuse forming urostyle, well-developed vocal cords, tympanic membrane on surface of head

caecilians

highly specialized, elongated and limbless, small eyes, sensory tentacle on head

amniotes

• amniotic egg permitted invasion of vast number of new habitats

• amniotic sac which serves to provide a protective enviroment for the developing embryo or fetus in reptiles, birds, and mammals

• classification of amniotes based largely on temporal skull fenestrate

reptiles

• first fully terrestrial vertebrates

• extends back to carboniferous

• mesozoic is age of reptiles

• epidermal derived scales

• lungs for respiration

• 3 or 4 chambered heart

• mostly ectothermic

anapsids : turtles

• no temporal fenestrae

• ribs, vertebrae, dermal bone, and epidermal plates modified to form a carapace and plastron

• pectoral and pelvic girdles located inside ribs

• no teeth

• KNOW TEMPORAL BONES

synapsids : proto mammals

• infra temporal fenestrae only

• all extinct but gave rise to mammals

diapsids : most reptiles

• 2 temporal fenestrae

lepidosaurians : lizards, snakes, Amphisbaenia

• overlapping epidermal derived scales

• acrodont or pleurodont tooth attachment

• skull has secondarily lost 1 or both temporal fenestrae

archosaurians : crocs, dinosaurs, pterosaurs, ancestor of birds

• epidermal derived plates

• thecodont tooth attachment

• 4 chambered heart

• crop

• 2 temporal fenestrae

• most with ant orbital and mandibular fenestrae

• antorbital fenestrae secondarily lost in crocodiles

pterosaurs : flying reptiles

• wings were formed by skin membranes attached to elongated 4th digit of each arm and extending to ankles

saurischian

lizard hipped with pubis directly anteriorly and ischium directed posteriorly

ornithischian

bird hipped with pubis and ischium parallel and directed posteriorly

avians (birds)

endothermic saurician dinosaurs with feathers

archaeopteryx

long tail, thecodont tooth attachment, brain case not expanded, small sternum, synsacrum not well developed, trunk vertebrae not rigidly fused

• had feathers

neornithes : modern birds

• retained reptilian scales on legs and feet

• toothless keratinized beak

• 4 chambered heart

• very thin modified diapsid skull

• slender long bones containing air sacs from lungs

• wrist, palm and digits have reduced number of bones

• large cerebellum

• feathered wing, fusion of carpals with metacarpals and fusion of digits

mammals

• appeared end triassic

• endothermic amniotes with the greatest habitat diversity of all tetrapods

• synapsid skull, hair, and mammary glands

• 3 ossicle bones in middle ear cavity

• muscular diaphragm separating thoracic and abdominal cavities

• sweat glands

• only 2 sets of teeth heterodontic dentition

• extensive development of cerebral cortex

prototherians : monotremes

lay heavily yolked eggs, malleus and incus larger then in other mammals, no corpus callous in brain, endothermic but body temperature is less stable than that of most other mammals, cloaca

metatherians : marsupials

• embryonic yolk sac in contact with chorion serves as choriovitelline placenta

• young incubated and nursed after birth in mammals abdominal pouch

• walls of pouch supported by epipubic bones

• no cloaca, double vagina and bifurcation penis

eutherians : placentals

• very diverse with varied habitats

• chorion in contact with allantois serves as chorioallantoic placenta

• young carried in uterus until fully developed