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Mammalian diversity
mammalian infraclasses, orders, etc and characteristics
| Term | Definition |
|---|---|
| Order: Monotremata | Monotremata=1 hole in reference to cloaca, distribution: Australia & New Guinea, sublclass: Prototheria, 1 order, 2 families, 5 species |
| Monotremata, ancestral characteristics | Ovipary, no corpus collosum, cloaca, cervical rib, low body temperature 32 degrees celcius (not very stable, tracks environment somewhat), epipubic bones, reptile-like teste and sperm, pectoral girdle: coracoid, precoracoid and interclavicle bones present |
| Monotremata, mammal-like characteristics | hair, mammary glands (no nipples), dentary-squamosal articulation in jaw, 3 ear bones, left aortic arch 4 chambered heart |
| Monotremata, other distinctive characteristics | edentate as adults (no teeth, juvenile teeth never break gumline), abdominal testes (no scrotum), baculum, quite k-selected (low reproductive rates, high parental care, long-lived, slow development), no vibrissae |
| Monotremata, reproduction | eggs (16X14mm), 10-11 day incubation, only left ovary sheds eggs |
| Monotremata, family: Ornithorhynchidae | duck-billed platypus, semi-aquatic, feed on invertebrates, some small fish, amphibians, bill has nerve-endings sensitive to electrical fields from muscle contractions of prey, venomous glands in spur (deadly to small animals prey on), lay eggs in burrows |
| Monotremata, family: Tachyglossidae | echidnas/spiny anteater, specialized for myrmecophagy, spurs (no venom), pouch (single young) |
| Infraclass: Metatheria | Neotropics, Australia, South America, simple placenta (choriovitelline), altricial young, no cloaca, angular inflection mandible, 7 orders based largely on dentition and digits |
| Metatheria, Dentition | Polyprotodont: multiple lower incisors, Diprotodont: 2 lower procumbent incisors |
| Metatheria, Digits | Didactylus: no digits fused, Syndactylus: 2nd and 3rd digits fused in common skin-sheet |
| Metatheria, General characteristics | pouch (~1/2), teeth throughout life, altricial young, viviparous, smallish brains, scrotum anterior to penis, low metabolic rate (~30%) than Eutherians, narrower range ecological niches than Eutherians, no baculum, smaller body size range |
| Metatheria, historical zoogeography | may have originated North America during Cretaceous (~100mya), some dispersal to Europe (~50mya), extirpated in North America by 15-20 mya, dispersed to Antarctic/Australia continent (~65mya), in Australia developed in isolation from Eutherians |
| Metatheria, Order: Didelphimorphia, Family: Didelphidae | New World opossums, most in South America, polyprotodont, didactylus, primitive dental formulae, absent to well developed pouch, pentadactyl, sparsely-haired prehensile tail, narrow brain case |
Created by:
jebeard
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