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Order XENARTHRA (formerly Edentata)

anteaters, sloths and armadillos

Traits

  1. xenarthrous vertebrae [fig 15.3]
  2. incorporation of caudal vertebrae into sacrum
  3. reduced to absent dentition, without enamel;
  4. low metabolic rates and low body temperatures [Fig. 15.1]

CLASSIFICATION

Recent studies have divided the xenarthrans into two orders.  The cingulates have a dermal bones in their skin, producing a "shell."  The pilosans are covered with hair.

Order CINGULATA
Dasypodidae (9, 21) Armadillos
Glyptodontidae the extinct glyptodonts (Fig. 15.4)
Order PILOSA
Suborder Folivora (Tardigrada)
Bradypodidae (1, 4) Three-toed sloths
Megalonychidae (1, 2) Two-toed sloths
Suborder Vermilingua
Myrmecophagidae (2, 3) True anteaters
Cyclopedidae (1,1) Silky anteater

Folivora (Tardigrada) sloths

  1. the two living sloths were traditionally been placed in the same family (Bradypodidae) because they have many characteristics in common, such as the following:
    1. Neotropical
    2. no tail, blocky skull
    3. arboreal; hang upside down in trees
    4. folivores
    5. variable body temperature,  bask to warm
    6. form symbiotic relationships with red or green algae on the surface of hair making green appearance to pelage
    7. gestation unusually long--11.5 months

Bradypodidae

  1. Bradypus (three-toed tree sloths, ais) [Figs. 15.5B, 15.7]
  2. 3 toes on front [Fig. 15.6A, B] and hind limb
  3. 8 or 9 cervical vertebrae give neck greater flexibility
  4. photographs of Bradypus tridactylus left by Dr. Lloyd Glenn Ingles, California Academy of Sciences. Copyright 2001 California Academy of Sciences.  Right by Ben Hernandez,  2001 used with permission 

 

Megalonychidae

  1. Choloepus (two-toed tree sloths) [fig 15.5A] is more closely related to the extinct, giant ground sloth Megalonyx than to Bradypus.
  2. two toes on the front foot [Fig. 14.5C], three on the hind.  Observe the front and hind feet on the Choloepus quicktime movie taken by William Lukefahr at the US National Zoological Park
  3. anterior-most cheektooth is a caniniform premolar
  4. 5 to 8 cervical vertebrae
  5. more active than three-toed sloths
  6. broader range of food habits than Bradypus

 

         
 Choloepus didactylus:   US National Zoo                     Megalonyx Image from Wikipedia
           picture by Will Lukefahr                                             This file is licensed under
                                                                                    Creative Commons Attribution ShareAlike 3.0 Unported

Vermilingua -- Anteaters

  1. Neotropical
  2. feed on ants and termites (myrmecophagy)
  3. long tapered skull [Fig. 7.3]
  4. no teeth
  5. very long vermiform tongue [Fig. 7.3] extending to posterior portion of sternum
  6. large salivary glands 
  7. powerful clawed forelimbs with 3 toes
 Myrmecophagidae--anteaters [Fig. 15.8]
  1. Myrmecophaga, the giant anteater (up to 60+ kg)
  2. Tamandua is arboreal


  Myrmecophaga - photographed at the US National Zoological Park by Will Lukefahr.  Used with permission.

Cyclopedidae
  1. Cyclopes didactylus 
  2. the silky anteater
  3. arboreal
  4. the smallest Neotropical anteater, 250 g.

      

Cyclopes didactylus -- pictures by Dr. Michael Tewes  used with permission

Dasypodidae--armadillos [Fig. 15.9, 15.11]
  1. Neotropical, Nearctic
  2. body covered with bony scutes, which are overlain by epidermal, keratinized scales, connected by flexible skin, and are attached to body by connective tissue [Fig. 15.12]
  3. homodont dentition
  4. diet is insects, invertebrates, carrion, plant material
  5. powerful diggers
  6. delayed implantation [Fig. 10.7D, pp. 205-206]
  7. birth of 1 to 12 young from a single ovum (monozygotic polyembryony).  Dasypus novemcinctus   produces four young of the same sex. [p. 206]
  8. Dasypus novemcinctus  (the Texas state small mammal) has expanded its range into the Southeastern U.S. [Fig. 15.10]

Dasypus novemcinctus -- nine banded armadillo photograph 2001by Dr. Allan H. Chaney,
 used with permission

the Texas Small Mammal

 


Order PHOLIDOTA--pangolins or scaly anteaters

 

  • learn more about pangolins from
  1. the University of Michigan Animal Diversity web
  2. or the University of California Museum of Paleontology

Family Manidae

  1. pangolins: "scaly anteaters" (fig 15.13)
  2. covered dorsally in overlapping, keratinous scales 
  3. belly is furred
  4. nocturnal, arboreal or terrestrial
  5. arboreal forms with prehensile tail
  6. Diet of ants and termites
  7. edentate
  8. extremely long tongue (longer than head and body length) passes over sternum and is anchored to long processes of the pelvis

 


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