Lagomorpha, Macroscelidea, RODENTIA

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Lagomorpha, Macroscelidea, RODENTIA

• Mammalogy
• EEOB 625
• 13 February 2004

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Order Lagomoprpha

• Are lagomorphs closely related to Rodentia?
  - similar cranial morphology adaptive zones
  
• - no consensus from molecular studies
  (Vaughan)
• Lagomorphs arose in Asia (Paleocene) underwent
  radiation in N. America in Oligocene - Miocene
• Comparisons with Rodentia
  - incisors adaptations to herbivory I
  2/1 vs. I 1/1
• - Jointed skull with diastema
  fenestrated maxillary - cursorial adaptations
  long hind legs (in Leporidae)

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Order Lagomorpha 80 species

• Worldwide distribution except Australia
• Family Leporidae 11 genera, 54 species
• Competitive herbivores with derived
  cursorial adaptations in diverse habitats around
  the World
• Family Ochotonidae 2 genera, 26 species
  Smaller with sorter hind limbs and ears Nearctic
  and Paleactic in mountainous habitats
• Unusual nutritional strategy of hay making

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Order Macroscelidea Elephant Shrews

• Family Macroscelididae 4 genera, 15 species
• Medium-sized, 50-500 g, in the Ethiopian since
  the Miocene
• Related to insectivores or elephants?
• Reduction of digits to 4 in pes, 3 (?) in pes
• Wide variety of habitats, feed on a variety of
  invertebrates, mostly termites ants

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Rodentia the gnawing victors

• About 43 of all mammals are rodents
• Criteria of success of a taxon __, ___, ___
• Why are rodents so successful? (Exam II)
• How do we approach such a question?
• Origin and Evolution Fossils from the late
  Paleocene in Asia and North America
• - Paramys, a squirrel-like ancestral genus from
  the Paleocene

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Paramys sp
Therapsid
Multituberculate
Feldhamer (1999)
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Rodentia the gnawing victors

• How do we classify 2004 species, 443 genera, and
  29 extant families?
• Derived characters (Vaughan Table 18-1)
• Parallel evolution obscures relationships and
  make classification to suborder difficult
• A classification based on the infraorbital
  foramen, masseter, zygomatic arch (Vaughan
  18-2)
• Sciuromorpha, Myomorpha, Hystricomorpha

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Paramys sp
Cobert (1969)
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Zygo-masseteric Patterns in Rodents

• Sciuromorphous Primitive, squirrel-like
  masseter lateralis originates on rostrum and
  zygomatic plate, infraorbital foramen, small
• Myomorphous Derived, mouse-like medial
  masseter originates on rostrum (maxillary)
  passes through a slightly enlarged infraorbital
  foramen.
• Hystricomorphous Highly derived,
  porcupine-like. Medial masseter originates on
  rostrum and passes through a greatly enlarged
  infraorbital Typical of several Neotropical
  families

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Medial masseter the infraorbital foramen of a
myomorph rodent
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Rodent Dentition Mastication

• Is mastication the key to rodents success?
• Incisors enamel on labial surface only and
  rootless for continuous growth
• Diastema - a common gap in herbivores
• Molars premolars similar in appearance but
  different in development.
• Marvelous masticatory movements of the mandible
  the elongated glenoid fossa and the moveable
  mandibular symphysis

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Heteromyidae
View from below glass of a foraging kangaroo rat
Seeds beads
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The EndLagomorpha, Macroscelidea, RODENTIA I
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Family Dipodidae

• Jerboas jumping mice (51 species)
• Nearctic, Palearctic, Ethiopian,

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Dipodidae ( Zapodidae)
Zapus or Napaeozapus ?