Mrs. Ofelia Solano Saludar Department of Natural Sciences University of St. La Salle Bacolod City

Amniotes: embryos develop within an amniotic sac in association with other extraembryonic membranes

 1 st amniotes; 6,000 living species  Mostly ectothermic tetrapods  Respiration by lungs  Skin dry, lacking mucous glands, and covered by epidermal scales, clawed  Reptilian subclasses are classified in part according to presence or absence of temporal fenestrae which are large holes on the side of the skull serving as muscle attachments.  The resulting greater bulk of muscles results in stronger jaw musculature

Eurypsida

Cotylosaurs- stem reptiles; about 300 mya

MODERN-DAY REPTILES

1.Chelonia - turtles & tortoises; unchanged for about 175 million years; identified by bony dermal plates to which ribs & trunk vertebrae are fused 2.Lepidosauria  Rhynchocephalia (Sphenodonta) - only living representative is the tuatara  Squamata - lizards, geckos, & snakes Tortoise- land dwelling; Turtle-aquatic

3.Archosauria a. Thecodontia- stem archosaurs: common ancestor for pterosaurs, dinosaurs, crocodilians & birds

 Saurischia & Ornithischia are the 2 dinosaur orders, with the division based on the shape of the pelvic bone.  Saurischian pubis juts forward, and its ischium points backward.  Herbivorous Ornithischian pubis & ischium both point backward; structure similar to birds  The famous carnivorous dinosaurs were from the Saurischian order, as were the largest herbivorous dinosaurs.

b. Pterosauria- winged diapsid reptiles; wing was supported by an elongated fourth digit; modified scales that were wing-supporting fibers are analogous to bird feathersPterosauria c.Crocodilia- crocodiles and alligatorsCrocodilia Alligators have "U"-shaped, rounded snout, whereas crocodiles have pointed "V"-shaped noses. In alligators, the upper jaw is wider than the lower so the teeth are hidden when the mouth shuts. In crocodiles, the jaws are the same width, so teeth interlock when the mouth shuts. Crocodiles have salt glands on their making them tolerant to saline water. Alligators prefer to stay in freshwater areas. Crocodiles are also more aggressive than alligators

 Birds; 8,700 species; endothermic vertebrates with front limbs modified for flight; body covered with feathers; scales on feet.  May have arisen from an archosaurian reptile, perhaps a small bipedal dinosaurarchosaurian reptile  Lost several dinosaur characteristics (e.g., long tail & teeth) but retained others: claws, scales, diapsid skull, single occipital condyle & feathers

Archaeopteryx appeared in mid- Mesozoic; it had solid bones, but weakly developed keel & weakly developed flight muscles

1.Odontognathae- extinct; toothed marine birds (Hespornis, Ichthyornis); many features of modern birds (e.g., hollow bones & short tail) 2.Paleognathae- small wings but powerful leg muscles; flightless ratites (rhea, ostrich, emus, cassowaries)

3.Neognathae - birds adapted for sustained flight; with large sternal carina; modifications to reduce weight include: loss of some bones, pneumatic bones, reduced tail, loss of teeth, loss of urinary bladder

 4,500 species  Hair, mammary glands, 3 middle ear bones, muscular diaphragm, sweat glands, marrow within bones, 2 sets of teeth, biconcave, enucleate red blood cells, well-developed cerebral cortex

Synapsid lineage began with Pelycosaurs (transitional between amphibians and later members), and succeeded by Therapsids from within mammals evolved. Mammals retain therapsid features: 2 occipital condyles, a secondary palate, heterodont dentition, dentary is the largest jaw bone.

Prototherians

Primates- arboreal mammals Apes have mobile, rotary shoulder joint which allows them to brachiate and hang from their arms Monkeys do not have a broad shoulder structure and are quadrupeds.

 Prosimians- nocturnal primates; tarsiers and lemurs  Anthropoids- Platyrrhines (New world monkeys, marmosets); Catarrhines (baboons, macaques, rhesus monkeys, man)

 Hominid lineage diverged from other primates about 7 million years ago. Humans compared to other hominids:  Brain size – large size allows development of language and social behavior.  Jaw shape – shortened to give a flatter face.  Bipedalism - walking on two legs. o Frees hands to do other things. o Eyes set higher; can see farther.  Females smaller than males  Extended parental care changes family structure & enhances learning and social behavior.

THE SUMMIT OF CHORDATE EVOLUTION

QUIZ NEXT MEETING