Questions and Answers
What type of jaw has the angular process lying in the same vertical plane as the tooth row?
What is the definition of a Hystricognathous jaw?
Angular process lies lateral to the vertical plane of the tooth row.
What is the function of the masseter muscle?
It is especially important in horizontal movements of the jaw, large and subdivided in rodents for mastication.
What is the masseteric tubercle?
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What is the zygomatic plate?
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What family does the mountain beaver belong to?
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What family are squirrels and chipmunks part of?
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What is a characteristic of the Geomyidae family?
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What type of habitat do pocket mice belong to?
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What is the activity pattern of beavers (family Castoridae)?
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What type of diet do springhares (family Pedetidae) have?
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What family do jerboas belong to?
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What is the diet of Muridae family members?
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What type of habitat do new world porcupines (family Erethizontidae) prefer?
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What is the lifestyle of the Caviidae family?
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What type of activity pattern do agoutis (family Dasyproctidae) have?
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What is the primary habitat of chinchillas (family Chinchillidae)?
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What family does the nutria (or coypu) belong to?
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What lifestyle characterizes mole-rats (family Bathyergidae)?
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Study Notes
Jaw Types in Eutheria
- Sciurognathous Jaw: Angular process aligns with the vertical plane of the tooth row.
- Hystricognathous Jaw: Angular process is positioned laterally to the vertical plane of the tooth row.
Morphological Types
- Protrogomorphous: Specific morphological type; details not provided.
- Sciuromorphous: A type with anatomical features distinct to certain rodent families.
- Hystricomorphous: Refers to another morphological structure; specifics not detailed.
- Myomorphous: Morphological design common to different rodent species; specifics not outlined.
Muscular Structures
- Masseter Muscle: Crucial for jaw movements, particularly in rodents; subdivided into three sections (superficial, lateral, medial) to facilitate powerful chewing.
- Masseteric Tubercle: A prominent buccal feature where the superficial masseter muscle originates.
Rodent Families and Their Characteristics
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Aplodontiidae (Mountain Beaver): Found in dense forests; herbivorous diet; active during day and night; semi-fossorial; colonial behavior; range from Central California to Southern British Columbia.
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Sciuridae (Squirrels, Chipmunks, etc.): Habitat includes tundra to rainforest; diet consists of nuts and seeds; primarily diurnal; can be arboreal or terrestrial; solitary; worldwide distribution, except for Australia and polar regions.
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Geomyidae (Gophers): Predominantly found in North America; solitary and fossorial lifestyle.
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Heteromyidae (Pocket Mice, Kangaroo Rats): Ranging from deserts to tropical forests; nocturnal and solitary; diet includes seeds; distributed in Western North America to Central and Northwestern South America.
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Castoridae (Beavers): Habitat in rivers and lakes; nocturnal eaters of bark and leaves; gregarious; found in Northern Europe, Asia, and North America.
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Pedetidae (Springhare): Inhabit grasslands; herbivorous; nocturnal and solitary; exclusive to Africa.
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Dipodidae (Jerboas, Jumping Mice): Found in forests to deserts; herbivorous; nocturnal or crepuscular; solitary; inhabit Europe, North America, Asia, and Africa.
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Muridae (Old World Rats, Mice): Occupy diverse habitats from subarctic to tropical; omnivorous; active in various patterns; often gregarious; widespread across Europe, Asia, Africa, Australia, and Madagascar.
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Cricetidae (New World Rats, Mice): Diverse habitats including prairies and forests; omnivorous; exhibit varied activity patterns; lifestyle can be aquatic or arboreal; found in North America, Central America, South America, Europe, and Asia.
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Hystricidae (Old World Porcupines): Found from deserts to forests; nocturnal herbivores; behavior ranges from solitary to moderately gregarious across Asia and Africa.
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Erethizontidae (New World Porcupines): Inhabit various terrains from deserts to forests; nocturnal dietary herbivores; solitary; found in North America and northern South America.
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Caviidae (Guinea Pigs, Capybara): Live in grasslands to forest edges; primarily herbivorous; diurnal or crepuscular; social in nature; distributed in South America.
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Dasyproctidae (Agoutis): Found in forest environments; herbivorous with both diurnal and nocturnal activity; solitary in nature; native to Central and South America.
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Chinchillidae (Chinchillas, Viscachas): Inhabit rocky mountainous areas and grassy plains; herbivorous; active during the day or night; can leap bipedally; found in western and southern South America.
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Myocastoridae (Nutria or Coypu): Live in slow-moving streams and marshes; herbivorous and nocturnal; amphibious with gregarious behavior; range includes South America and parts of Europe.
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Bathyergidae (Mole-rats): Adapted to various soil types in arid regions; herbivorous diet; primarily active in the morning and mid-afternoon; can be solitary or colonial; confined to Africa.
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Test your knowledge of the subclass Eutheria with these flashcards. Each card features important terminology related to jaw morphology in placental mammals. Perfect for students of zoology and animal classification.
