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Toxodontia

Toxodontia[3] is a suborder of the meridiungulate order Notoungulata. Most of the members of the five included families, including the largest notoungulates, share several dental, auditory and tarsal specializations.[4] The group is named after Toxodon, the first example of the group to be discovered by science.

Toxodontia
Temporal range: Paleocene–Holocene
Mixotoxodon
Scientific classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Notoungulata
Suborder: Toxodontia
Families[2]

Description edit

 
Thomashuxleya reconstruction

Isotemnidae, the oldest and most primitive family of toxodonts, were generally large animals with larger canines than other early notoungulates. The family is probably paraphyletic or polyphyletic since only primitive dental features unite the 12 included genera, such as a complete dentition with unreduced canines and no diastemata in the earliest genera. Likewise, they are only weakly linked to other toxodonts by a few dental features, and their primitive cheek tooth pattern can be basal to all notoungulates except notioprogonians. The oldest of the 12 genera in this family is Isotemnus known from the Riochican-Casamayoran, but other genera are known from the Casamayoran, including Thomashuxleya, Pleurostylodon, and Pampatemnus. Of these, the sheep-sized Thomashuxleya is the best known; its skeleton shows that it was relatively robust, had limbs with reduced distal elongation, and five-hoofed feet with a large central digit.[4]

Notohippidae was also present during the Casamayoran but tend to have more hypsodont cheek teeth than isotemnids. Pampahippus, one of the earliest genera in this family was, nevertheless, low-crowned with densely packed cheek teeth. Its primitiveness is suggested by the retained paraconids on the lower molars. Eomorphippus, a Mustersan notohippid, was moderately hypsodont, Deseadan genera such as Rhynchippus and Eurygenium were very high-crowned, and Santacrucian genera had acquired cementum on the crowns similar to equids.[4]

 
Leontinia gaudryi skull
 
Toxodon skull

The last toxodont family from the early Tertiary are the Leontiniidae. They share several derived tarsal and auditory features with the notohippids and are, together with the Deseadan Toxodontidae, nested within the paraphyletic Notohippidae. Leontiniids are known from the Deseadan or later, but the oldest and most primitive leontiniid, the Mustersan Martinmiguelia, retained a primitive brachydont dentition without diastemata except around the very small canines. Scarrittia, the best-known leontiniid, had mesaxonic (enlarged central digit) feet with reduced lateral digits.[4]

Toxodontids first appeared during the Oligocene in the form of Proadinotherium. Another well-known toxodontid is Nesodon, a medium-sized Miocene toxodontid descended from Proadinotherium which had converted its second upper incisors into tusks. Toxodon itself evolved during the Pliocene alongside the related Trigodon, an equally large mammal which possessed a horn projecting from its forehead, in the same way as a modern rhinoceros. Toxodon was a huge herbivore (about the size of a modern black rhinoceros) with four toes on each foot.

Notes edit

  1. ^ Martínez, Gastón; Dozo, María T.; Gelfo, Javier N.; Ciancio, Martín R.; González-José, Rolando (2020-12-16). "A new toxodont (Mammalia, Panperissodactyla, Notoungulata) from the Oligocene of Patagonia, Argentina, and systematic considerations on the paraphyletic 'Notohippidae'". Journal of Systematic Palaeontology. 18 (24): 1995–2013. doi:10.1080/14772019.2021.1872723. ISSN 1477-2019. S2CID 232116246.
  2. ^ . Mikko's Phylogeny Archive. Archived from the original on June 22, 2013. Retrieved 26 June 2009.
  3. ^ Toxodontia in the Paleobiology Database. Retrieved April 2013.
  4. ^ a b c d Rose 2006, pp. 230–1

References edit

  • McKenna, Malcolm C.; Bell, Susan K. (1997). Classification of Mammals Above the Species Level. New York: Columbia University Press. ISBN 0231110138. OCLC 37345734.
  • Rose, Kenneth David (2006). The beginning of the age of mammals. Baltimore: JHU Press. ISBN 0801884721.


toxodontia, suborder, meridiungulate, order, notoungulata, most, members, five, included, families, including, largest, notoungulates, share, several, dental, auditory, tarsal, specializations, group, named, after, toxodon, first, example, group, discovered, s. Toxodontia 3 is a suborder of the meridiungulate order Notoungulata Most of the members of the five included families including the largest notoungulates share several dental auditory and tarsal specializations 4 The group is named after Toxodon the first example of the group to be discovered by science ToxodontiaTemporal range Paleocene Holocene PreꞒ Ꞓ O S D C P T J K Pg NMixotoxodonScientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass MammaliaOrder NotoungulataSuborder ToxodontiaFamilies 2 Homalodotheriidae Isotemnidae paraphyletic Eutoxodontia 1 Leontiniidae Notohippidae paraphyletic ToxodontidaeDescription edit nbsp Thomashuxleya reconstructionIsotemnidae the oldest and most primitive family of toxodonts were generally large animals with larger canines than other early notoungulates The family is probably paraphyletic or polyphyletic since only primitive dental features unite the 12 included genera such as a complete dentition with unreduced canines and no diastemata in the earliest genera Likewise they are only weakly linked to other toxodonts by a few dental features and their primitive cheek tooth pattern can be basal to all notoungulates except notioprogonians The oldest of the 12 genera in this family is Isotemnus known from the Riochican Casamayoran but other genera are known from the Casamayoran including Thomashuxleya Pleurostylodon and Pampatemnus Of these the sheep sized Thomashuxleya is the best known its skeleton shows that it was relatively robust had limbs with reduced distal elongation and five hoofed feet with a large central digit 4 Notohippidae was also present during the Casamayoran but tend to have more hypsodont cheek teeth than isotemnids Pampahippus one of the earliest genera in this family was nevertheless low crowned with densely packed cheek teeth Its primitiveness is suggested by the retained paraconids on the lower molars Eomorphippus a Mustersan notohippid was moderately hypsodont Deseadan genera such as Rhynchippus and Eurygenium were very high crowned and Santacrucian genera had acquired cementum on the crowns similar to equids 4 nbsp Leontinia gaudryi skull nbsp Toxodon skull The last toxodont family from the early Tertiary are the Leontiniidae They share several derived tarsal and auditory features with the notohippids and are together with the Deseadan Toxodontidae nested within the paraphyletic Notohippidae Leontiniids are known from the Deseadan or later but the oldest and most primitive leontiniid the Mustersan Martinmiguelia retained a primitive brachydont dentition without diastemata except around the very small canines Scarrittia the best known leontiniid had mesaxonic enlarged central digit feet with reduced lateral digits 4 Toxodontids first appeared during the Oligocene in the form of Proadinotherium Another well known toxodontid is Nesodon a medium sized Miocene toxodontid descended from Proadinotherium which had converted its second upper incisors into tusks Toxodon itself evolved during the Pliocene alongside the related Trigodon an equally large mammal which possessed a horn projecting from its forehead in the same way as a modern rhinoceros Toxodon was a huge herbivore about the size of a modern black rhinoceros with four toes on each foot Notes edit nbsp Wikimedia Commons has media related to Toxodonta nbsp Wikispecies has information related to Toxodonta Martinez Gaston Dozo Maria T Gelfo Javier N Ciancio Martin R Gonzalez Jose Rolando 2020 12 16 A new toxodont Mammalia Panperissodactyla Notoungulata from the Oligocene of Patagonia Argentina and systematic considerations on the paraphyletic Notohippidae Journal of Systematic Palaeontology 18 24 1995 2013 doi 10 1080 14772019 2021 1872723 ISSN 1477 2019 S2CID 232116246 Toxodonta Mikko s Phylogeny Archive Archived from the original on June 22 2013 Retrieved 26 June 2009 Toxodontia in the Paleobiology Database Retrieved April 2013 a b c d Rose 2006 pp 230 1References editMcKenna Malcolm C Bell Susan K 1997 Classification of Mammals Above the Species Level New York Columbia University Press ISBN 0231110138 OCLC 37345734 Rose Kenneth David 2006 The beginning of the age of mammals Baltimore JHU Press ISBN 0801884721 Retrieved from https en wikipedia org w index php title Toxodontia amp oldid 1118808994, wikipedia, wiki, book, books, library,

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