Basal Eutheria Flashcards
How did explosion of plant diversity contribute to increasing presence of early eutherians?
- angeosperm starts to appear (flowering plants)
- produces pollen = explosion of insects
- early mammals are insectivores (lots of food for them to eat in Cretaceous = diversification)
What kind of molariform teeth are characteristic of basal eutherians?
- 3 tribosphenic molars with high, sharp cusps
- last PM clearly distinguishable from first M
Duplex uterus:
- 2 uteri, each with cervix opening into vagina
- rabbits, rodents, hares, aardvarks, hyrax
Bicornuate uterus:
- uterine horns Y-shaped but fused forming a chamber opening into the vagina through a single cervix
- whales, carnivores
Bipartite uterus:
- horns of uterus are separate but enter the vagina by a single cervix
- most widespread
Simplex uterus:
- no separation between the uterine horns, opens into the vagina through one cervix
- some bats, higher primates
baculum
- bony structure in penis
- some mammals have it (very reduced in great apes, carnivores usually have one)
Choreoallantoic placenta
- characteristic of all eutherian mammals
- develops from embryonic membranes
- long-lived and vascular (vs. metatherians)
- villi provide increased surface area for exchange of nutrients, gases, and waste
- nutrients passed along walls and capillaries but no actual blood exchanged
Types of chorioallantoic placenta
-differ in distribution of villi, efficiency of nutrient/gas/waste exchange
- Diffuse: villi scattered evenly throughout uterus
- Cotyledonary: evenly spaced patches of villi
- Zonary: continuous band of villi around the placenta
- Discoid: villi organized into 1-2 disc shapes
Epitheliochorial chorioallantoic placenta
- villi rest in pockets of endometrium
- least efficient type of chorioallantoic placenta
Endotheliochorial chorioallantoic placenta
- maternal capillary in direct contact with chorion of fetus
Hemochorial chorioallantoic placenta
- no maternal epithelium
- no distinct maternal capillaries
- mother’s blood is bathing villi directly
Endothelioendothelial chorioallantoic placenta
- no connective tissue in between mother and embryo
- second most effective chorioallantoic placenta
Hemoendothelial chorioallantoic placenta
- fetal capillaries (cells) bathed in maternal blood
- most direct/effective chorioallantoic placenta
- some rodents, rabbits, hares
Golden moles
s.C. Theria
I.C. Eutheria
S.O. Afrotheria
O. Afrosoricida
- resemble marsupial moles
- no pinnae, eyes covered with skin and fur
Tenrec
s.C. Theria
I.C. Eutheria
S.O. Afrotheria
O. Afrosoricida
- very diverse group
- found mostly in Madagascar
- panniculus carnosus muscle to roll into a ball
- several have spines
Elephant shrew
s.C. Theria
I.C. Eutheria
S.O. Afrotheria
O. Macroscelida
- small insectivores
- diverse
- Africa
- bipedal hopping
Aardvark
s.C. Theria
I.C. Eutheria
S.O. Afrotheria
O. Tubulidentata
- myrmecophagy
- use smell to find ant/termite prey = fleshy tentacles on nose
- teeth surrounded by cementum instead of enamel (make of dentine prisms) = not true teeth
Paenungulates
- elephant, hyrax, manatee
- shared characteristics:
- no clavicles
- short nails, 4 digits on forefeet
- all nonruminating, herbivorous, hindgut fermenters with a large caecum
- bicornuate uterus, males have no scrotum or baculum
Proboscidea
elephants (African and Asian)
s.C. Theria
I.C. Eutheria
S.O. Afrotheria
O. Proboscidea
Synapomorphies:
- graviportal limbs = bone vs. muscle supports large weight
- proboscis
- tusks grow throughout life
- heavy skull with air pockets
widespread by Oligocene
Manatees and Dugongs
s.C. Theria
I.C. Eutheria
S.O. Afrotheria
O. Sirenia
- only herbivorous aquatic mammals
- live in warm water due to poor thermoregulation and low metabolism
- fusiform
- only fur is vibrissae
- no ear pinnae
Hyraxes
s.C. Theria
I.C. Eutheria
S.O. Afrotheria
O. Hyracoidea
- hypsodont or lophodont teeth
- two cecums to aid with digesting veg
- diastema with super weird upper incisors and tricuspid lower incisors
Xenarthra
s.C. Theria
I.C. Eutheria
S.O. Xenarthra
-sloths, anteaters, armadillos
Synapomorphies:
- at least 2 intervertebral articulations (xenarthrales) on lumbar and some thoracic vertebrae
- reduced/simplified dentition
- no incisors/canines
- cheekteeth single-rooted, no enamel
- extra rigidity in axial skeleton
- Limbs specialized for digging, climbing
- Well-developed processes on scapula and expanded ischium
- Low metabolic rates, body temps: limited to warm areas, move slowly
Anteaters and sloths
s.C. Theria
I.C. Eutheria
S.O. Xenarthra
O. Pilosa
- anteaters and sloths
- N and S America
Anteater:
- edentate
- myrmecophagous
Sloth:
- algae in fur
- low metabolic rate
- 2- or 3-toed
