Baraguatherium

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Not to be confused with Baguatherium.

Baraguatherium
Temporal range: 20.43–15.97 
Ma[1]
↓
Early Miocene (Colhuehuapian-Santacrucian)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Pilosa
Family: †Mylodontidae
Genus: †Baraguatherium
Rincón et al. 2016
Species:
†B. takumara
Binomial name
†Baraguatherium takumara
Rincón et al. 2016

Baraguatherium is an extinct genus of ground sloths of the family Mylodontidae that lived during the Early Miocene of what is now Venezuela. It dates to the Early Miocene, around 20.44 to 15.97 million years ago and represents the oldest representative of its family in the northern part of South America to date. The structure of the teeth suggests that the genus represents a rather basal form within the Mylodontidae. Unlike other mylodonts, which tended to prefer open grasslands, Baraguatherium lived in a riverine, coastal tropical rainforest.

Discovery and naming

The remains of Baraguatherium known to date are from the

Orophodontidae.[5]

The genus name Baraguatherium is composed of the name Baragua for Serranía La Baragua (also Sierra de La Baragua), a mountain range in northern Venezuela, on the southern flank of which the Cerro la Cruz locality is located, and the Greek word θηρίον (thērion) for "beast". The only species known to date is Baraguatherium takumara. The species epithet refers to the word takumará of the Ayamanes Indio group, in whose language means "sloth".[6]

Description

Baraguatherium is a medium sized representative of the Mylodontidae. Its body weight was estimated to be about 495 to 765 kg based on an incompletely preserved femur. In addition to the long bone, a fragmented right mandibular branch with the preserved posterior three teeth and some isolated teeth of the maxilla are also present. The mandible is missing the anterior section and the upper part of the ascending branch. The fragment is 12.3 cm long in total. The mandible itself was massive and wide. When reconstructed, the two rows of teeth were probably parallel to each other, which differs from most other mylodonts, which had divergent rows of teeth due to their ready snouts. The symphysis extended to the second molariform (molariform) tooth and was rather narrow. The lower margin of the mandible was straight. At the upper margin, the transition to the ascending articular branch was rounded, it started directly behind the last tooth. The mandibular dentition was similar to that of other mylodonts with one anterior canine (caniniform) tooth and three posterior molariform teeth. Of the anterior caniniform tooth, only the alveolus has been documented in Baraguatherium, but there was no diastema to the posterior teeth, unlike numerous other mylodonts. All three molars were characterized by a bilobate occlusal surface structure with raised margins and a shallow depression between them. On the last molar-like tooth, the anterior lobe was significantly wider than the posterior. In internal structure, the teeth had a core of vasodentin, a softer component of the dentine, encased in orthodentin, a harder variety. The outer layer was formed of tooth cementum, but it was thinner in Baraguatherium than in other mylodonts. As in all sloths, the enamel was absent. The length of the molar row was 6.8 cm. The second molar-like tooth was the largest tooth at 2.1 cm long and 1.7 cm wide, but all teeth were similar in dimensions.[6]

The femur is preserved at about 35 cm in length, which is about 60 to 70% of the total length. When reconstructed, it may have been between 41 and 46 cm long. The shaft showed a board-like flattened shape characteristic of large ground sloths. The condyle and the greater trochanter have not survived, and the third trochanter was located at the middle of the shaft and pointed backwards. The knee joint was characterized by a larger inner (middle) and smaller outer (lateral) joint roll.[6]

Paleobiology

Due to the large femur it can be assumed that Baraguatherium belonged to the ground-dwelling sloths and moved quadrupedally. The geological-paleontological evidence points as habitat to a coastal tropical rainforest, which was crossed by numerous rivers. In this respect Baraguatherium differed from other mylodonts, which rather preferred open grasslands.[6]

Classification

Baraguatherium is an extinct genus of the extinct family Mylodontidae. The Mylodontidae represent a branch of the suborder of sloths (

Mylodontoidea (sometimes, however, the Scelidotheriidae and the Orophodontidae are considered only as a subfamily of the Mylodontidae).[7] In a classical view, based on skeletal anatomical studies, the Mylodontoidea in turn represent one of the two major evolutionary lineages of sloths, along with the Megatherioidea. Molecular genetic studies and protein analyses assign a third to these two groups, the Megalocnoidea. Within the Mylodontoidea are the two-fingered sloths (Choloepus), one of the two extant sloth genera.[8][9] The Mylodontidae form one of the most diverse groups within the sloths. Prominent features are found in their high-crowned teeth, which deviate from those of the Megatherioidea with a rather flat (lobate) occlusal surface. This is often associated with a greater adaptation to grassy foods. The posterior teeth have a round or oval cross-section, while the anteriormost have a canine-like design. The hind foot is also distinctly rotated so that the sole points inward.[10][11] Mylodonts appeared as early as the Oligocene, with Paroctodontotherium from Salla-Luribay in Bolivia among their earliest records.[12]

Mylodontidae 

References

  1. ^ "†Baraguatherium Rincón et al. 2016 (edentate)". Fossilworks.
  2. ^ Marcelo R. Sánchez-Villagra, R. J. Burnham, R. M. Feldmann, E. S. Gaffney, R. F. Kay, R. Lozsán, R. Purdy und G. M. Thewissen: A new nearshore marine fauna and flora from the Early Neogene of Northwestern Venezuela. Journal of Paleontology 74 (5), 2000, S. 957–968
  3. ^ a b Marcelo R. Sánchez-Villagra, Robert J. Asher, Ascanio D. Rincón, Alfredo A. Carlini, Peter Meylan und Robert Purdy: New faunal reports for the Cerro La Cruz Locality (Lower Miocene, Northwestern Venezuela). In: Marcelo R. Sánchez-Villagra und J. A. Clack (Hrsg.): Fossils of the Miocene Castillo Formation, Venezuela: contributions on neotropical palaeontology. Special Papers in Palaeontology 71, 2004, S. 105–116
  4. ^ Marcelo R. Sánchez-Villagra, Orangel A. Aguilera, Rodolfo Sánchez und Alfredo A. Carlini: The Fossil Vertebrate Record of Venezuela of the Last 65 Million Years. In: Marcelo R. Sánchez-Villagra, Orangel A. Aguilera und Alfredo A. Carlini (Hrsg.): Urumaco and Venezuelan Paleontology, The Fossil Record of the Northern Neotropics. Indiana Press University, 2010, S. 19–51
  5. ^ a b Ascanio D. Rincón, Andrés Solórzano, Mouloud Benammi, Patrick Vignaud und H. Gregory McDonald: Chronology and geology of an Early Miocene mammalian assemblage in North of South America, from Cerro La Cruz (Castillo Formation), Lara State, Venezuela: implications in the ‘changing course of Orinoco River’ hypothesis. Andean Geology 41 (3), 2014, S. 507–528, doi:10.5027/andgeoV41n3-a02
  6. ^ a b c d Ascanio D. Rincón, Andrés Solórzano, H. Gregory McDonald und Mónica Núñez Flores: Baraguatherium takumara, Gen. et Sp. Nov., the Earliest Mylodontoid Sloth (Early Miocene) from Northern South America. Journal of Mammalian Evolution 24 (2), 2017, S. 179–191
  7. PMID 30239971
    .
  8. ^ Frédéric Delsuc, Melanie Kuch, Gillian C. Gibb, Emil Karpinski, Dirk Hackenberger, Paul Szpak, Jorge G. Martínez, Jim I. Mead, H. Gregory McDonald, Ross D.E. MacPhee, Guillaume Billet, Lionel Hautier und Hendrik N. Poinar: Ancient mitogenomes reveal the evolutionary history and biogeography of sloths. Current Biology 29 (12), 2019, S. 2031–2042, doi:10.1016/j.cub.2019.05.043
  9. ^ Samantha Presslee, Graham J. Slater, François Pujos, Analía M. Forasiepi, Roman Fischer, Kelly Molloy, Meaghan Mackie, Jesper V. Olsen, Alejandro Kramarz, Matías Taglioretti, Fernando Scaglia, Maximiliano Lezcano, José Luis Lanata, John Southon, Robert Feranec, Jonathan Bloch, Adam Hajduk, Fabiana M. Martin, Rodolfo Salas Gismondi, Marcelo Reguero, Christian de Muizon, Alex Greenwood, Brian T. Chait, Kirsty Penkman, Matthew Collins und Ross D. E. MacPhee: Palaeoproteomics resolves sloth relationships. Nature Ecology & Evolution 3, 2019, S. 1121–1130, doi:10.1038/s41559-019-0909-z
  10. ^ H. Gregory McDonald und Gerardo de Iuliis: Fossil history of sloths. In: Sergio F. Vizcaíno und W. J. Loughry (Hrsg.): The Biology of the Xenarthra. University Press of Florida, 2008, S. 39–55.
  11. ^ H. Gregory McDonald: Evolution of the Pedolateral Foot in Ground Sloths: Patterns of Change in the Astragalus. Journal of Mammalian Evolution 19, 2012, S. 209–215
  12. S2CID 42451
    .
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