INFRACLASS EUTHERIA (= "Placentalia")

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INSECTIVORA (Eulipotyphla)

shrews, moles, hedgehogs (4 families,442 species)

  1. The Order Insectivora has been used as a scrap basket for a variety of very small, relatively unspecialized, insectivorous eutherians with cheekteeth simple, tritubercular or quadritubercular.
  2. Tree shrews, elephant shrews, and dermopterans have been placed in separate orders.
  3. Insectivora has been restricted to the Lipotyphla (shrews, solenodons, moles, hedgehogs, tenrecs and golden moles).
  4. However, molecular evidence indicates golden moles and tenrecs belong in the Afrotheria, a taxonomic group that also includes elephants, sea cows, hyraxes, aardvarks, elephant shrews.  A new order "Afrosoricida" comprises Chrysochloridae (golden moles) and Tenrecidae (tenrecs).
  5. The Insectivora is restricted to to the Eulipotyphla (shrews, solenodons, moles, hedgehogs, and Nesophontes)
  6. CHARACTERISTICS
    1. simplified hindgut lacking a caecum [Fig. 7.2]
    2. small to medium sized
    3. pentadactyl
    4. plantigrade
    5. long pointed snouts
    6. sharp teeth
    7. pinnae and eyes are usually small to absent
    8. annular tympanic bone [absence of auditory bullae]
    9. smooth cerebrum
  7. The Insectivora has been divided further into two orders: Erinaceomorpha for the hedgehogs, Soricomorpha for the rest.

Order Erinaceomorpha

  1. Erinaceidae--hedgehogs [figs. 12.5, 12.6] and moon rats (gymnures)
    1. Ethiopian, Palearctic, Oriental
    2. 10 genera, 24 species
    3. Most with spiny (barbless) pelage, roll into ball for defense
    4. moon rats (gymnures) lack spines; when threatened, produce a foul smell.
    5. omnivorous: diet consists of invertebrates, small vertebrates, eggs, fruit.
    6. Skull and dental characteristics
      1. low cusps (unlike shrews or moles): used in crushing and grinding
      2. first lower incisors are well developed, but not as large as in shrews
    7. estivate in response to low food availability
    8. hedgehogs as pets
    9. The Compleat Internet Hedgehog Atlas
    10. Clipart images courtesy of the The Florida Center for Instructional Technology


Hedgehog


Raffle's gymnure

  •  Order Soricomorpha

    1. Talpidae--moles [fig 12.12]
      1. Holarctic, Oriental
      2. 17 genera, 42 species
      3. Fossorial [fig. 12.13]
        1. Convergent evolution in all faunal regions [Fig. 12.4]
        2.  zygomatic arch complete 
        3. eyes minute
        4. ears lack pinnae
        5. modifications of the forelimb and pectoral girdle [Fig. 112B, C]
      4. touch receptors (Eimer’s organ) on snout [Figs. 7.4, 21.7]
      5. Old World desmans feed on aquatic invertebrates and fish



    Neurotrichus gibbsii--Shrew-mole; photograph by Dr. Lloyd Glenn Ingles, California Academy of Sciences Copyright � 2000 California Academy of Sciences; used with permission

    1. Soricidae--shrews [figs. 12.9]
      1. Holarctic, Ethiopian, Oriental, Neotropical (to northern Colombia)
      2. largest "insectivore" family (26 genera, 376 species)
      3. constitute about 60% of individuals in community composition studies when pitfalls are used rather than Sherman or other live traps (!)
      4. 2.5g (smallest living mammal) - 180 g
      5. Long slim snout, small eyes, ears usually visible
      6. skull characters (Fig. 12.10)
        1. no zygomatic arch
        2. I1, large hooked
        3. strongly procumbent lower incisors)
      7. high metabolic rate (must eat almost constantly)
      8. saliva toxic in some (e.g. Blarina, Fig. 6.12)
      9. Rudimentary echolocation in Sorex and Blarina to locate prey
      10. Caravanning in crocidurines 
      11. more information from the shrew site by Werner Haberl 



    Sorex vagrans--Vagrant Shrew; photograph by Dr. Lloyd Glenn Ingles, California Academy of Sciences. Copyright � 1999 California Academy of Sciences; used with permission

    1. Solenodontidae--solenodons [fig. 12.7]
      1. Neotropical (Greater Antilles - Hispaniola and Cuba, until recently in Puerto Rico)
      2. 1 genus, 2 species
      3. large size, up to 600 g
      4. Feed primarily on invertebrates
      5. high frequency clicking for echolocation
      6. elongate, flexible, shrew-like snout for locating food
      7. neurotoxic saliva injected with grooved lower incisor [Fig. 12.8]
      8. more information from Alexander Ferworn, Ryerson University
      9. , more on the Solenodon 

     


    Solenodon
    Clipart image courtesy of the The Florida Center for Instructional Technology

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