Astrapotheria

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Astrapotheria
Temporal range:
Ma
Skull of Astrapotherium
Reconstruction of Astrapotherium
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade: Meridiungulata
Order: Astrapotheria
Lydekker 1894[1]
Families

Astrapotheriidae

Eoastrapostylopidae

Trigonostylopidae

Astrapotheria is an extinct order of South American[2] and Antarctic[3] hoofed mammals that existed from the late Paleocene to the Middle Miocene, 59 to 11.8 million years ago.[2] Astrapotheres were large, rhinoceros-like animals and have been called one of the most bizarre orders of mammals with an enigmatic evolutionary history.[4]

This taxonomy of this order is not clear, but it may belong to

perissodactyls.[5][6][7]

Description

Astrapotherium magnum skull

Their

notoungulates, but it seems to have evolved independently. The cheek teeth are similar to rhinocerotoids, including similar microstructure, which indicate they had the same function.[4]

Postcranially, astrapotheres are relatively robust and more or less graviportal but have slender long bones, most notably in the hindlegs, suggesting they were amphibious. In order to support their proboscises and large heads they had relatively long and massive necks in relation to the rest of the vertebral column. Their feet are pentadactyl with short and stout podial and metapodial bones. Most characteristic for the order are the flat astragalus, equipped with a short neck and a flat head, articulating with both the navicular and cuboid bones; and their calcaneus with its enlarged peroneal tubercle.[4]

Three families are recognized:

Trigonostylopidae from the Paleocene-Eocene, and Astrapotheriidae from the Eocene-Miocene. The Brazilian, Itaboraian Tetragonostylops and the Argentinian, Riochican Eoastrapostylops are the oldest astrapotheres. The latter, with its low-crowned and lophoselenodont cheek teeth, is considered the most primitive astrapothere. Trigonostylopids are distinct from other astrapotheres in their ear anatomy but are included in the order because of otherwise similar characters.[4] Antarctodon is one of few eutherian mammals, as well as one of the last known terrestrial vertebrates, found in Antarctica.[8]

The most famous member of the order is undoubtedly

Scaglia and Albertogaudrya, were between a sheep and a tapir in size and already the largest South American mammals.[4]

Classification

There is no scientific consensus regarding the classification within Astrapotheria. For example, Paula Couto 1963 originally described Tetragonostylops as a trigonostylopid but Soria 1982 and 1984 transferred the genus to Astrapotheriidae and concluded that the remaining two genera in that family, Trigonostylops and Shecenia, form a basal collateral branch within Astrapotheriidae. According to Cifelli 1993, Trigonostylopidae (including Eoastrapostylopidae) is the stem group of Astrapotheriidae.[9]

References

  1. ^ Astrapotheria in the Paleobiology Database. Retrieved March 2013
  2. ^ a b "The uruguaytheriine Astrapotheriidae from the rich middle Miocene Honda Group of the upper Magdalena River valley in Colombia (...) are the youngest securely dated remains of that order in South America." Johnson & Madden 1997, p. 356
  3. S2CID 58908785
    .
  4. ^ a b c d e Rose 2006, pp. 235–6
  5. S2CID 4467386
    .
  6. .
  7. .
  8. ^ Bond et al. 2011
  9. ^ Bond et al. 2011, Relationships
  10. ^ a b c d e f g h i j Classification of the order Astrapotheria in the Paleobiology Database. Retrieved March 2013.
  11. ^ "Phylogenetic analysis suggests that Antarctodon is closer to genera classified by previous authors as astrapotheriids (e.g., Albertogaudrya and Tetragonostylops) than it is to Trigonostylops." Bond et al. 2011, p. 2
  12. ^ "Name — Eoastrapostylopidae Soria & Powell 1981". Index to Organism Names. Archived from the original on 2016-12-21. Retrieved 1 March 2013.

Bibliography