Eutatus

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Eutatus
Skeletal reconstruction of Eutatus

Skeletal reconstruction of Eutatus

Temporal occurrence
Pleistocene to early Holocene
3.6 to 0.012 million years
Locations
Systematics
Sub-articulated animals (Xenarthra)
Armored siderails (Cingulata)
Armadillos (Dasypoda)
Chlamyphoridae
Euphractinae
Eutatus
Scientific name
Eutatus
Gervais , 1867

Eutatus is an extinct genus of the armadillos and is more precisely assigned to the fossil line of the Eutatini, whose members were originally native to the southern part of South America. The genus lived mainly during the Pleistocene and reached the dimensions of today's giant armadillo . According to research, it mainly fed on plants and its hair was thicker than that of most modern armadillos.

features

Eutatus was a large representative of the armadillos (Dasypoda) and reached a head-trunk length of over 70 cm, with an assumed body weight of around 50 kg. This gave it a size comparable to today's giant armadillo ( Priodontes maximus ). In terms of physique, Eutatus was similar to today's armadillos, but had individual peculiarities. The skull was up to 26 cm long and 11 cm wide at the zygomatic arches . The cheekbones also had a downward-facing arch in the side view, so that they had a U-shaped course. The rostrum in particular was very elongated, typical of eutatine armadillos, and thus significantly more extensive than its current relatives, such as the bristle armadillos ( Chaetophractus ). Furthermore, it was significantly higher than that of most of the Eutatini members. The approximately 15 cm long lower jaw had a slim structure with a low bone body. The teeth consisted of nine simple, nail-like teeth per half of the jaw, a total of 36, with the rear teeth partially elongated. No teeth were formed in the intermaxillary bone.

Armor from Eutatus

The design of the tank was characteristic. The head armor was roughly triangular in shape and consisted of bone shields, the surface of which was sculpted by tubercle-like elevations. The oval and clearly coupled back armor only had a firmer shoulder part at the front edges, which is typical of the Eutatini. The rest of the front and middle tank area consisted of individual, movable bands. The solid, rear part of the pelvis had a unique structure in that the individual bands did not run in a semicircle over the armor, but each formed an open triangle with an obtuse angle on the middle of the back, the tip of which pointed forward. On the surface, the bone platelets that formed the ligaments and were mostly square in shape, had strong roughening through individual small openings and bumps. They had a structure similar to that of the other armadillos, with an inner and outer layer of bone between which there were individual cavities that represented glands and hair follicles . With four to six hair follicles per label, Eutatus was once relatively hairy.

Fossil finds

Eutatus occurred mainly in the Pleistocene in the central area of South America , but has also been detected in the late Pliocene around 3 million years ago. Significant sites are mainly in northern and central Argentina and in southern Uruguay . More than 40 sites with fossil remains of the armadillo are known. A more or less complete individual is from Mar del Plata in the Argentine province of Buenos Aires . A partial skeleton with skull and vertebrae as well as remains of the musculoskeletal system, which were discovered on the Río Salado , come from the same province . The most recent finds are dated to the early Holocene , including some skeletal elements and osteoderms from the Río Paraná in the Argentine province of Santa Fe .

Paleobiology

The construction of the lower jaw shows adaptations to a stronger, plant-based diet. This can be seen, among other things, at the joint ends, which are designed to be rather flat and thus enable lateral chewing movements. Such a way of feeding could also be determined on the basis of microscopic examinations of the teeth, which rather show an abrasion pattern of herbivores. The reconstruction of the masticatory muscles also proved to be very strong and suitable for plant-based food. Since Stenotatus , Doellotatus and Ringueletia also have similar characteristics, such a diet seems to have been typical of eutatine armadillos. The significantly stronger hairiness of Eutatus , recognizable by the larger number of hair follicles in the bone platelets, is possibly associated with the cold and dry climatic conditions of the pampa region during the Pleistocene .

Systematics

Eutatus is a now extinct genus from the group of armadillos (Dasypoda) and belongs to the Chlamyphoridae family , within this the genus belongs to the subfamily Euphractinae . This are the closest living relatives, the chaetophractus ( Chaetophractus ), the six-banded armadillo ( Euphractus ) and the Pichi ( Zaedyus ). However, these three forms form an independent tribe within the Euphractinae, the Euphractini, while Eutatus is counted to the Eutatini, a line that has now died out. The subfamily of the Euphractinae appeared in fossil form in the Upper Eocene over 40 million years ago, but from a phylogenetic and anatomical point of view they represent the most modern member of the armadillos. In some cases, the Eutatini were considered a possibly polyphyletic group, as Proeutatus is a form that comes from anatomical conditions was grouped closer with the gigantic Glyptodontidae . Molecular genetic studies from 2016 provisionally contradict this.

A total of three types are distinguished today:

Other species, mostly established by Florentino Ameghino , such as E. brevis , E. punctatus and E. minutus, are now part of E. seguini . Of the three recognized species, E. pascuali is the oldest, it existed since the end of the Pliocene and disappeared again at the end of the Lower and in the transition to the Middle Pleistocene. E. seguini occurred mainly in the Middle and Younger Pleistocene , while E. crispianii has so far only been documented from the transition from the Pleistocene to the Holocene . The genus was first described in 1867 by Paul Gervais . The holotype (copy number MNHN -PAM: 273) comprises a partial skeleton with a skull and is kept in the Natural History Museum in Paris .

Individual evidence

  1. ↑ a b c d e C. M. Krmpotic, A. Carlini and GJ Scillato-Yané: The species of Eutatus (Mammalia, Xenarthra): Assessment, morphology and climate. In: Quaternary International 210, 2009, pp. 66-75
  2. ^ A b Sergio F. Vizcaíno and María S. Bargo: The masticatory apparatus of the armadillo Eutatus (Mammalia, Cingulata) and some allied genera: paleobiology and evolution. In: Paleobiology 24 (3), 1998, pp. 371-383
  3. ↑ a b C. M. Krmpotic, MR Ciancio, C. Barbeito, RC Mario and AA Carlini: Osteodermmorphology in recent and fossil euphractine xenarthrans. In: Acta Zoologica (Stockholm) 90, 2009, pp. 339-351
  4. ↑ a b c Luciano Brambilla and Damián Alberto Ibarra: A new species of Eutatus Gervais (Xenarthra, Dasypodidae) from the Late Pleistocene of the Northern Pampean Region, Argentina. Palaeontologia Electronica 20 (1). 2017, p. 13A ([palaeo-electronica.org/content/2017/1767-a-new-species-of-eutatus])
  5. ^ Alfredo A. Carlini, Martín Ricardo Ciancio, John J. Flynn, Gustavo J. Scillato ‐ Yané and André R. Wyss: The phylogenetic and biostratigraphic significance of new armadillos (Mammalia, Xenarthra, Dasypodidae, Euphractinae) from the Tinguirirican (early oligocene ) of Chile. In: Journal of Systematic Palaeontology 7 (4), 2009, pp. 489-503
  6. ^ Daniela C. Kalthoff: Microstructure of Dental Hard Tissues in Fossil and Recent Xenarthrans (Mammalia: Folivora and Cingulata). In: Journal of Morphology 272, 2011, pp. 641-661
  7. ↑ Guillaume Billet, Lionel Hautier, Christian de Muizon and Xavier Valentin: Oldest cingulate skulls provide congruence between morphological and molecular scenarios of armadillo evolution. In: Proceedings of the Royal Society B 278, 2011, pp. 2791-2797
  8. ↑ Frédéric Delsuc, Gillian C. Gibb, Melanie Kuch, Guillaume Billet, Lionel Hautier, John Southon, Jean-Marie Rouillard, Juan Carlos Fernicola, Sergio F. Vizcaíno, Ross DE MacPhee and Hendrik N. Poinar: The phylogenetic affinities of the extinct glyptodonts. Current Biology 26, 2016, pp. R155-R156 DOI: 10.1016 / j.cub.2016.01.039

Web links

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