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ZOOL 320 - CH 22

Primitive Mammals

reversed triangles in molar teeth holotheria
tribosphenic molars with protocone and talonid tribosphenida
braincase. double rooted cheek teeth. initially quadrate-articular and squamosal-dentary in jaw articulation. early mammals
middle ear evolved independently three times in early mammals
expansion of cerebrum from dorsal ventribular ridge of dorsal pallium bird
expansion of cerebrum from lemnopallium of dorsal pallium mammal
docodont. triconodont. symmetrodont. dryolestid. holotheria. tribosphenida. mesozoic mammals
glenoid cavity oriented horizontally. scapula immobile. both clavicle and interclavicle. primitive shoulder girdle
cusps on their molars are concave anteriorly on the uppers and concave posteriorly on the lowers, indicating retraction of the mandible during chewing. multituberculate
cusps on their molars are concave posteriorly on the uppers and concave anteriorly on the lowers, indicating protraction of the mandible during chewing. rodents
forelimb placed under girdle closer to midline. shoulder girdle moves with forelimb during the stride. excursion of the shoulder girdle in therian mammals
shoulder joint immobile. glenoid laterally oriented. both coracoid and procoracoid. primitive
scapulocoracoid fused Derived (A)
acromion process of scapula strongly overturned. glenoid oriented downward. proximal head of humerus spherical and inturned. procoracoid reduced or lost. theriiformes
interclavicle lost. supaspinous fossa. theria
platypus. long-nosed echidna (New Guinea). short-nosed echidna (Australia). monotremes
modern forms have reduced teeth as juveniles before losing them monotremes
early forms had teeth, not tribosphenic molars monotremes
cochlea structure uncoiled early mammals
cochlea structure half a coil monotreme
cochlea structure coiled up to 360 degrees theria
ampulla, utriculus, sacculus, cochlea, semicircular canals multiple coils of therian mammals
obturator foramen first appears in synapsids
ilium extended farther forward in mammals
bone present in monotremes, marsupials, and earliest placentals marsupial bone
monotreme, lays eggs, suckles young platypus
passages from the uterus, bladder, and intestine open into the cloaca as in reptiles. monotremes
passages form uterus and bladder exit together but the anal exit is separate. marsupials
usually separate openings for the uterus, bladder, and intestine. placental mammals
sidewall of braincase is from alisphenoid therian synapomorphy
lost interclavicle. procoracoid lost with theriiformes. coracoid reduced as process on scapula. supraspinous fossa is new. therian shoulder girdle
have small cervical ribs monotremes
superposition of astragalus over calcaneum in therians
marsupial bones originally thought to support the pouch, but present in monotremes, basal placentals, and even tritylodont cynodonts. epipubic
the bones stiffen the trunk in them during walking when one hindlimb and diagonally opposite forelimb are forward and others back. the opossum
jugal forms portion of jaw glenoid. flared nasal bones. 5 upper incisors and 4 lower. 3 premolars. 4 molars. inflected angle to jaw. marsupial (opossum, Didelphis)
rectangular nasal bones. jugal ends before glenoid. auditory bulla. noninflected angle to jaw. 2 molars. 4 premolars. 3 upper and lower incisors. placental (raccoon, Procyon)
shrew opossum, monitor del monte, tasmanian devil, rabbit-eared bandicot, koala, rat kangaroo, honey possum, marsupial mole, and opossum are examples of marsupials
shearing teeth in carnivorous forms is an adaptation of this marsupial borhyaena
divergent first toe for climbing is an adaptation of this marsupial opossum
syndactylous 2nd and 3rd toes in this marsupial for grooming fur kangaroo
a giant herbivorous marsupial from the Pleistocene of Australia, about 11 feet in length. diprotodon
dog-like carnivore, cat-like carnivore, arboreal glider, fossorial herbivore, and digging ant feeder are examples of this. strongest examples or convergent evolution in biology.
How do tribosphenic molars work? occlusion between teeth of upper and lower jaw.
group of primitive placentals with lower metabolic rates. tongue retractor muscles originate on sternum. xenarthra
lost all incisors and canine. large, recurved claws. caniniform premolar. gets name from extra articular surfaces of vertebrae. xenarthra
have interclavicle and coracoid bones marsupial newborns
front claws act as holdfasts, shoulder arch assist in wriggling crawl of body. marsupial newborns
in mammalian placenta, choriovitelline placenta is associated with the yolk sac
in mammalian placenta, chorioallantoic placenta is in basic placental mammal
used for countercurrent flow for thermoregulatiton vasular plexus
carnivorous marsupials of South America of upper Oligocene to Miocene age, was as large as a wolf. Borhyaena
of Pliocene age, was comparable to a jaguar in size and paralleled in a remarkable way the large sabertooth cats. Thylacosmilus
Created by: dominatrix