Palaeanodonta

Palaeanodonta ("ancient toothless animals") is an extinct clade of stem-pangolins. They were insectivorous, possibly fossorial, and lived from the Early Paleocene to Early Oligocene in North America, Europe and East Asia.[4][5][6] While the taxonomic grouping of Palaeanodonta has been debated,[7] it is widely thought that they are a sister group to pangolins.[8][9][5][10]

Palaeanodonta
Temporal range: Early Paleocene – Early Oligocene
From top to bottom: Ernanodon antelios, Xenocranium pileorivale and Metacheiromys marshi
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Pholidotamorpha
Order: †Palaeanodonta
Matthew, 1918[1]
Families and genera
Synonyms
list of synonyms:
  • Ernodonta (Ding, 1987)
  • Ernanodonta (Ding, 1987)
  • Palaeanodontiformes (Kinman, 1994) [2]
  • Palaenodontina (Pearse, 1936)[3]

Anatomy

Skull

Palaeanodonts generally have low and caudally-broad skulls, with notable lambdoid crests and inflated bullae and squamosals.[4]

Teeth

Despite the name of the group and contrary to their pangolin relatives, palaeanodonts are known to have had teeth.[11][4][10] Early palaeanodonts retained minimal tribosphenic post-canines while later species had peglike or otherwise reduced molar crowns.[11][4][10] Many also had large, characteristic cuspids.[11][10]

Classification and phylogeny

Traditional classification
  • Order: †Palaeanodonta (Matthew, 1918) (stem-pangolins)[4]
    • Family: †Epoicotheriidae (Simpson, 1927)
    • Family: †Escavadodontidae (Rose & Lucas, 2000)
    • Family: †Metacheiromyidae (Wortman, 1903)
    • Incertae sedis:
      • Genus: †Amelotabes (Rose, 1978)
      • Genus: †Arcticanodon (Rose, 2004)
      • Genus: †Melaniella (Fox, 1984)

Revised classification
  • Order: †Palaeanodonta (Matthew, 1918) (stem-pangolins)[6]
    • Family: †Epoicotheriidae (Simpson, 1927)
      • Genus: †Alocodontulum (Rose, 1978)
        • †Alocodontulum atopum (Rose, 1977)
      • Genus: †Auroratherium (Tong & Wang, 1997)
        • †Auroratherium sinense (Tong & Wang, 1997)
      • Genus: †Dipassalus (Rose, 1991)
        • †Dipassalus oryctes (Rose, 1991)
      • Genus: †Pentapassalus (Gazin, 1952)
        • †Pentapassalus pearcei (Gazin, 1952)
        • †Pentapassalus woodi (Guthrie, 1967)
      • Genus: †Tubulodon (Jepsen, 1932)
        • †Tubulodon taylori (Jepsen, 1932)
      • Subfamily: †Epoicotheriinae (Simpson, 1927)
        • Genus: †Epoicotherium (Simpson, 1927)
          • †Epoicotherium unicum (Douglass, 1905)
        • Genus: †Molaetherium (Storch & Rummel, 1999)
          • †Molaetherium heissigi (Storch & Rummel, 1999)
        • Genus: †Tetrapassalus (Simpson, 1959)
          • †Tetrapassalus mckennai (Simpson, 1959)
          • †Tetrapassalus proius (West, 1973)
        • Genus: †Xenocranium (Colbert, 1942)
          • †Xenocranium pileorivale (Colbert, 1942)
    • Family: †Ernanodontidae (Ting, 1979)
      • Genus: †Asiabradypus (Nessov, 1987)
        • †Asiabradypus incompositus (Nessov, 1987)
      • Genus: †Ernanodon (Ting, 1979)
        • †Ernanodon antelios (Ting, 1979)
    • Family: †Escavadodontidae (Rose & Lucas, 2000)
      • Genus: †Escavadodon (Rose & Lucas, 2000)
        • †Escavadodon zygus (Rose & Lucas, 2000)
    • Family: †Metacheiromyidae (paraphyletic family)[6] (Wortman, 1903)
      • Genus: †Brachianodon (Gunnell & Gingerich, 1993)
        • †Brachianodon westorum (Gunnell & Gingerich, 1993)
      • Genus: †Mylanodon (Secord, 2002)
        • †Metacheiromys dasypus (Secord, 2002)
      • Subfamily: †Metacheiromyinae (paraphyletic subfamily)[6] (Wortman, 1903)
        • Genus: †Metacheiromys (Wortman, 1903)
          • †Metacheiromys dasypus (Osborn, 1904)
          • †Metacheiromys marshi (Wortman, 1903)
        • Genus: †Palaeanodon (Matthew, 1918)
          • †Palaeanodon ignavus (Matthew, 1918)
          • †Palaeanodon nievelti (Gingerich, 1989)
          • †Palaeanodon parvulus (Matthew, 1918)
      • Subfamily: †Propalaeanodontinae (Schoch, 1984)
        • Genus: †Propalaeanodon (Rose, 1979)
          • †Palaeanodon parvulus (Rose, 1979)
    • Incertae sedis:
      • Genus: †Amelotabes (Rose, 1978)
        • †Amelotabes simpsoni (Rose, 1978)
      • Genus: †Arcticanodon (Rose, 2004)
        • †Arcticanodon dawsonae (Rose, 2004)
      • Genus: †Melaniella (Fox, 1984)
        • †Melaniella timosa (Fox, 1984)

Phylogenetic tree

The phylogenetic relationships of Palaeanodonta are shown in the following cladogram:[4][5][6]

 Pholidotamorpha 
 

Pholidota (sensu stricto)

 
 †Palaeanodonta 
 

†Escavadodontidae

 
 
 ? 

†Amelotabes

 
 ? 

†Melaniella

 
 
 

†Epoicotheriidae

 
 ? 

†Arcticanodon

 
 
†Metacheiromyidae
 

†Propalaeanodontinae

 
 
 

†Mylanodon

 
 
 

†Brachianodon

 
 
 

†Palaeanodon

 
 
 

†Metacheiromys

 
 

†Ernanodontidae

 
 
 
 
 †Metacheiromyinae
 
 
 
 
 
 (Pholidota [sensu lato]) 

References
  1. W. D. Matthew (1918.) "A revision of the Lower Eocene Wasatch and Wind River faunas. Part V. Insectivora (Continued), Glires, Edentata." Bulletin of the American Museum of Natural History 38(16):429-483
  2. Kenneth E. Kinman (1994.) "The Kinman system: toward a stable cladisto-eclectic classification of organisms: living and extinct, 48 phyla, 269 classes, 1,719 orders"
  3. Arthur Sperry Pearse (1936.) "Zoological names. A list of phyla, classes, and orders, prepared for section F, American Association for the Advancement of Science" American Association for the Advancement of Science
  4. Rose, K. D. (2008). "9. Palaeanodonta and Pholidota". In Janis, C. M.; Gunnell, G. F.; Uhen, M. D. (eds.). Evolution of Tertiary Mammals of North America. Cambridge University Press. pp. 135–146. doi:10.1017/CBO9780511541438.010.
  5. Gaudin, T. J.; Emry, R. J.; Wible, J. R. (2009). "The Phylogeny of Living and Extinct Pangolins (Mammalia, Pholidota) and Associated Taxa: A Morphology Based Analysis". Journal of Mammalian Evolution. 16: 235. doi:10.1007/s10914-009-9119-9.
  6. Kondrashov, Peter; Agadjanian, Alexandre K. (2012). "A nearly complete skeleton of Ernanodon (Mammalia, Palaeanodonta) from Mongolia: morphofunctional analysis". Journal of Vertebrate Paleontology. 32 (5): 983–1001. doi:10.1080/02724634.2012.694319. ISSN 0272-4634.
  7. Averianov, A. O. & Lopatin, A. V. (2014.) "High-level systematics of placental mammals: Current status of the problem." Biology Bulletin, 41(9), 801–816.
  8. McKenna, M. C.; Bell, S. K. (1997). Classification of Mammals: Above the Species Level. Columbia University Press. pp. 220–221. ISBN 978-0-231-52853-5.
  9. Rose, K. D.; Emry, R. J.; Gaudin, T. J.; Storch, G. (2005). "Xenarthra and Pholidota". In Rose, K. D.; Archibald, J. D. (eds.). The Rise of Placental Mammals. Origins and Relationships of the Major Extant Clades. Johns Hopkins University Press. pp. 106–126. ISBN 978-0-8018-8022-3.
  10. Ungar, P. S. (2010). "Cenozoic Mammal Evolution". Mammal Teeth: Origin, Evolution, and Diversity. pp. 110–126. ISBN 978-0-8018-9668-2.
  11. Rose, K. D.; Lucas, S. G. (2000). "An early Paleocene palaeanodont (Mammalia, ?Pholidota) from New Mexico, and the origin of Palaeanodonta". Journal of Vertebrate Paleontology. 20 (1): 139–156. doi:10.1671/0272-4634(2000)020[0139:AEPPMP]2.0.CO;2.
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