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54 Cards in this Set

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  • Back
Describe the skull of a Metatherian
1. Narrow, sm braincase housing a brain w/relatively sm cerebral hemisphisphres
2. Auditory bullae, if present, formed fm allisphenoid bone
3. Palate w/lg vacuities
4. Angular process of mandible inflected medially
What's the dental formula for Metatherians?

5/4i, 1/1c, 3/3p, 4/4m = 50
What's unique about the dentition of Metatherians?
There are never equal numbers of incisors above and below (except in the Vombatidae)
What type of cheekteeth do the Metatherians have?
What's the name of the bone that's present on the pelvic girdle and is used to support the marsupium?
Epipubic bones are present on the pelvic girdle
Describe the Metatherian female reproductive tract.
1. Bifid
2. Bicornate vagina
3. Bipartate uterus
4. Lateral vaginal canal recieves forked penis of male and is the sperm pathway
5. Vaginal sinus is bith canal
Is the Metatherian female's Vaginal sinus Macropodidae (remaining open) or is it closed?
1. Some remain open (Macropodidae)
2. Most marsupials; sealed shut except during parturition
Where is the penis located in relation to the testes?
Penis is posterior to testes
Is the gestation period in the Metatherian long or short?
Short; the young are tiny and rudimentary at birth
What type placenta is found in the Metatherian? What's the yolk sac like?
1. Primitive Choriovitelline placenta
2. Yolk sac greatly enlarged; forms placenta
What are the three parts to reproduction in Kangaroos?
1. Postpartum estrus
2. Embryonic diapause
3. Double suckling
Describe Postpartum estrus
Mates shortly after giving birth
Describe Embryonic diapause
Suckling initiates neural and hormonal responses that induce dormancy of blastocyst, which is then covered by a protective membrane; no implanting or cell division
What happens when suckling stops?
Blastocyst development begins again; implanted and cell division initiated
Describe double suckling
-newborn on one nipple; recieves milk low in fat for slow growth
-Joey on 2nd nipple; recieves milk high in fat for rapid growth
Due to this unique three part reproduction cycle in Kangaroos, how many young could a mother potentially be nourashing?
Three; The blastocyst, pouchling attached to nipple, and Joey
Where and when are Marsupials first known?
Lower Cretacious in Texas
What were Cretacecous marsupials like?
Small, insectivorous and omniverous
What is the most primitive family in the Infraclass Metatheria?
Didelphidae; stem group from which most other forms were derived
When were Didelphidae present in N. America? What of its fossil record?
Early Cretaceous (no fossil record during Cenozoic)
When were Didelphidae present in S. American? What of its fossil record?
-Late Cretaceous
-Early Paleocene: 4 genera
*Nearly a continuous fossil record through the Cenozoic
When were Didelphidae present in Antarctica?
Late Cretaceous or Early Paleocene
When were Didelphidae present in Australia? What of fossil records?
-NO didelphids known
-earliest fossil marsupials Early Eocen
When were Didelphidae present in Africa?
-Oligocene; same genus as known fm Europe
When were Didelphidae present in Europe?
Early Eocene to Middle Miocene; single genus
Where do marsupials appear to have had their origin? Where did they migrate to and "develope"?
North America, they seem to have dispersed through the Southern Continents (Gondwanaland) and have had tr major radiations in South America and Australia.
What's the geographic distribution of the Family Didelphidae?
Living forms in North and South America; fossil forms more widely distributed
Contrast Syndactylous and Didactylous
- Syndactylous: two or more toes fused into common compartments of skin
- Didactylous: toes not fused into common compartments of skin
List 6 representative Genuses (common name) of the Family Didelphidae; Order Didelphimorphia
1. Wooly opossum
2. Four-eyed opossum
3. Mouse Opossums
4. Yapok (or water opossum)
5. Didelphis (lg American Opossum)
6. Thick-tailed opossum
How many species of Genus Didelphis are there? Are they herbivores, carnivores or omnivores?
Four species. Opportunistic feeders; omnivores
Are Didelphis virginiana nocturnal? What is their geographic distribution?
-yes, they're nocturnal
-Range fm S. Canada along the West Coast and from S. Canada, VT and NH along the East Coast to central Mexico; large hiatus in center of northern range (Rocky Mountains and desert region)
What is the Didelphis virginiana's current habitate expansion direction?
Expanding range northward into Canada
How long is the Didelphis virginiana gestation period? What's the litter size? How many Pouchlings?
-Gestation 13 days
-Litter size at birth: 10-56, average of 21
-Pouchlings (13nipples) 5 to 13, averages 8 to 9 in north US and 6 to 7 in south US
How old before a Didelphis virginiana baby releases the nipple? How long before baby leaves the pouch? How long before it is weaned?
-Releases nipple: 50 days
-leaves pouch: 70 days
-Rides mom's back until weaned at 90-120 days
What temperature in New England does the Didelphis virginiana stop foraging at?
Of the other Didelphis, which two are virtually impossible to tell apart w/out doing genetic analysis?
The black-eared opossum (Didelphis marsupialis) and white-eared opossum (Didelphis albiventris)
What is the single living family of Order Didelphimorphia?
Family Didelphidae
What are two examples of extinct South American families of Order Didelphimorphia?
1. Family Borhyaenidae
2. Family Necrolestidae
3. Family Caroloameghiniidae
What was the basal stock of South American Didelphoids (late Eocene)?
Family Caroloameghiniidae
Borhyaena where what? (of the family Borhyaenidae)
Hyaena-like marsupial
Thylacosmilus where what? (of the family Borhyaenidae)
Sabertooth marsupial
When did the Borhyaenidae Family become extinct and probably why?
- Pliocene, wn S. America came back in contact w/North America
-Modern ungulates replaced the archaic herbivores of S. Am.
-Eutherian carnivores colonized and outcompeted
What family and order is the Monito del monte in? What else is in this family and order?
Order Microbiotheria
Family Microbiotheridae
*No other living species or families in this order
The Monito de Monte was originally placed in which family? Why was it moved?
Originally in Family Didelphidae based on identical dental formulas, then DNA sequencing data placed it in the current Order-family-etc.
Which taxa did the DNA analysis show the Monito de Monte to be a sister taxa of?
Sister taxon of the Australian Diportodontidae
What's the geographic range of the Microbiotheria (Monito de Monte)?
Restricted to south-central Chile
Where have fossils of the Microbiotheria (Monito de Monte) been found?
S. America, Antarctica
What do natives call the Monito de Monte and what do they consider it?
Colo-colo: very bad luck
What's in the Order Paucituberculata?
Shrew or rat opossums
How many living families of Order Paucituberculata are there?
What is a key characteristic of the Paucituberculata marsupials?
No marsupium!
What's the range of the Paucituberculata?
Restricted to the Andes Mountains of norhtwestern S. America
Where have Paucituberculata fossils been found?
S. America and Antarctica
What are the three Genera of Order Paucituberculata?
1. Common rat opossum or shrew-opossum
2. Incan rat opossum
3. Chilean rat opossum