BIOL-3030 Lecture Notes - Lecture 23: Great American Interchange, Urogenital Sinus, Eutheria
Document Summary
Distinguished by chorioallantoic placenta (vascular connection between mom and young derived from two extraembryonic membranes, chorion and allantois) Clade xenarthra - 29 species sloth, anteaters, armadillos. Have xenarthrae = extra articulations between vertebrates. Reduced teeth; most big foreclaws for digging/hanging/defense. Sloths out of trees weekly to defecate harbor insects/algae in fur. Lagomorphs (rabbits and allies) edge -- good for gnawing. Distinctive teeth: every growing upper and lower incisors with enamel on front. Many groups: beavers, squirrels, mice and rats, guinea pigs, porcupines. Distinctive teeth: two upper incisor sets, one directly behind the other. Many rabbits have large ears, legs specialized for jumping locomotion. Many nocturnal or burrowing: most have long, sensitive snout and small eyes. Eutherian diversity - bats and primates (part of clade archonta) Skin over several long fingers (different than birds or pterosaurs) Most weak hind legs, hang upside down. Microchiropterans: small, echolocation - detect reflected sound pulses to find objects.
