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54 Cards in this Set
- Front
- Back
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Describe the skull of a Metatherian
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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 |
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What's the dental formula for Metatherians?
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Primite;
5/4i, 1/1c, 3/3p, 4/4m = 50 |
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What's unique about the dentition of Metatherians?
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There are never equal numbers of incisors above and below (except in the Vombatidae)
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What type of cheekteeth do the Metatherians have?
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Tribosphenic
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What's the name of the bone that's present on the pelvic girdle and is used to support the marsupium?
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Epipubic bones are present on the pelvic girdle
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Describe the Metatherian female reproductive tract.
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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 |
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Is the Metatherian female's Vaginal sinus Macropodidae (remaining open) or is it closed?
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1. Some remain open (Macropodidae)
2. Most marsupials; sealed shut except during parturition |
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Where is the penis located in relation to the testes?
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Penis is posterior to testes
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Is the gestation period in the Metatherian long or short?
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Short; the young are tiny and rudimentary at birth
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What type placenta is found in the Metatherian? What's the yolk sac like?
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1. Primitive Choriovitelline placenta
2. Yolk sac greatly enlarged; forms placenta |
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What are the three parts to reproduction in Kangaroos?
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1. Postpartum estrus
2. Embryonic diapause 3. Double suckling |
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Describe Postpartum estrus
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Mates shortly after giving birth
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Describe Embryonic diapause
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Suckling initiates neural and hormonal responses that induce dormancy of blastocyst, which is then covered by a protective membrane; no implanting or cell division
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What happens when suckling stops?
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Blastocyst development begins again; implanted and cell division initiated
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Describe double suckling
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-newborn on one nipple; recieves milk low in fat for slow growth
-Joey on 2nd nipple; recieves milk high in fat for rapid growth |
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Due to this unique three part reproduction cycle in Kangaroos, how many young could a mother potentially be nourashing?
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Three; The blastocyst, pouchling attached to nipple, and Joey
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Where and when are Marsupials first known?
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Lower Cretacious in Texas
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What were Cretacecous marsupials like?
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Small, insectivorous and omniverous
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What is the most primitive family in the Infraclass Metatheria?
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Didelphidae; stem group from which most other forms were derived
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When were Didelphidae present in N. America? What of its fossil record?
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Early Cretaceous (no fossil record during Cenozoic)
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When were Didelphidae present in S. American? What of its fossil record?
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-Late Cretaceous
-Early Paleocene: 4 genera *Nearly a continuous fossil record through the Cenozoic |
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When were Didelphidae present in Antarctica?
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Late Cretaceous or Early Paleocene
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When were Didelphidae present in Australia? What of fossil records?
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-NO didelphids known
-earliest fossil marsupials Early Eocen |
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When were Didelphidae present in Africa?
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-Oligocene; same genus as known fm Europe
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When were Didelphidae present in Europe?
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Early Eocene to Middle Miocene; single genus
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Where do marsupials appear to have had their origin? Where did they migrate to and "develope"?
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North America, they seem to have dispersed through the Southern Continents (Gondwanaland) and have had tr major radiations in South America and Australia.
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What's the geographic distribution of the Family Didelphidae?
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Living forms in North and South America; fossil forms more widely distributed
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Contrast Syndactylous and Didactylous
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- Syndactylous: two or more toes fused into common compartments of skin
- Didactylous: toes not fused into common compartments of skin |
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List 6 representative Genuses (common name) of the Family Didelphidae; Order Didelphimorphia
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1. Wooly opossum
2. Four-eyed opossum 3. Mouse Opossums 4. Yapok (or water opossum) 5. Didelphis (lg American Opossum) 6. Thick-tailed opossum |
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How many species of Genus Didelphis are there? Are they herbivores, carnivores or omnivores?
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Four species. Opportunistic feeders; omnivores
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Are Didelphis virginiana nocturnal? What is their geographic distribution?
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-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) |
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What is the Didelphis virginiana's current habitate expansion direction?
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Expanding range northward into Canada
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How long is the Didelphis virginiana gestation period? What's the litter size? How many Pouchlings?
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-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 |
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How old before a Didelphis virginiana baby releases the nipple? How long before baby leaves the pouch? How long before it is weaned?
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-Releases nipple: 50 days
-leaves pouch: 70 days -Rides mom's back until weaned at 90-120 days |
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What temperature in New England does the Didelphis virginiana stop foraging at?
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20F
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Of the other Didelphis, which two are virtually impossible to tell apart w/out doing genetic analysis?
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The black-eared opossum (Didelphis marsupialis) and white-eared opossum (Didelphis albiventris)
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What is the single living family of Order Didelphimorphia?
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Family Didelphidae
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What are two examples of extinct South American families of Order Didelphimorphia?
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1. Family Borhyaenidae
2. Family Necrolestidae 3. Family Caroloameghiniidae |
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What was the basal stock of South American Didelphoids (late Eocene)?
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Family Caroloameghiniidae
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Borhyaena where what? (of the family Borhyaenidae)
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Hyaena-like marsupial
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Thylacosmilus where what? (of the family Borhyaenidae)
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Sabertooth marsupial
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When did the Borhyaenidae Family become extinct and probably why?
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- 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 |
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What family and order is the Monito del monte in? What else is in this family and order?
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Order Microbiotheria
Family Microbiotheridae *No other living species or families in this order |
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The Monito de Monte was originally placed in which family? Why was it moved?
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Originally in Family Didelphidae based on identical dental formulas, then DNA sequencing data placed it in the current Order-family-etc.
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Which taxa did the DNA analysis show the Monito de Monte to be a sister taxa of?
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Sister taxon of the Australian Diportodontidae
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What's the geographic range of the Microbiotheria (Monito de Monte)?
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Restricted to south-central Chile
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Where have fossils of the Microbiotheria (Monito de Monte) been found?
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S. America, Antarctica
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What do natives call the Monito de Monte and what do they consider it?
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Colo-colo: very bad luck
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What's in the Order Paucituberculata?
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Shrew or rat opossums
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How many living families of Order Paucituberculata are there?
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One
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What is a key characteristic of the Paucituberculata marsupials?
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No marsupium!
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What's the range of the Paucituberculata?
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Restricted to the Andes Mountains of norhtwestern S. America
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Where have Paucituberculata fossils been found?
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S. America and Antarctica
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What are the three Genera of Order Paucituberculata?
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1. Common rat opossum or shrew-opossum
2. Incan rat opossum 3. Chilean rat opossum |
