''Baraguatherium'' is an extinct genus of ground sloths of the family

Mylodontidae Mylodontidae is a family of extinct South American and North American ground sloths within the suborder Folivora of order Pilosa The order Pilosa is a clade of xenarthran placental mammals, native to the Americas. It includes the anteaters a ...

that lived during the Early Miocene of what is now

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

. 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 Castillo Formation, which is exposed in the Falcón Basin in northwestern

. The Falcón Basin is located in the boundary of the

Caribbean The Caribbean (, ) ( es, El Caribe; french: la Caraïbe; ht, Karayib; nl, De Caraïben) is a region of the Americas that consists of the Caribbean Sea, its islands (some surrounded by the Caribbean Sea and some bordering both the Caribbean Se ...

to the

South American Plate The South American Plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African Plate, with which it forms the southern part of the Mid-A ...

. An almost complete depositional sequence has been preserved here, ranging from the

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

to the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Urumaco sequence of the Middle and Upper

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...

. The Castillo Formation is

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

older and covers the northwestern to southwestern margin of the Falcón Basin in a semicircular pattern. It was first studied and named in the 1960s. Among the most important outcrops is that of Cerro la Cruz near the town of La Mesa about 20km north of

Carora The City of Carora, commonly called Carora City (in Spanish, Ciudad de Carora), is a city in Lara State, Venezuela, on the Morere River, a branch of the Tocuyo River. It is about 54 miles southwest of Barquisimeto. Carora City was founded twice. T ...

in the Venezuelan state of

Lara Lara may refer to: Places * Lara (state), a state in Venezuela *Electoral district of Lara, an electoral district in Victoria, Australia * Lara, Antalya, an urban district in Turkey * Lara, Victoria, a township in Australia * Lara de los Infa ...

. It is located on the southern flank of the Serranía La Baragua and consists of a Sedimentary sequence at least 360m high on an area of about 2km². The sequence is composed of various layers of

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

s, in which individual layers of

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

and

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

are interbedded, in addition to which

limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...

s and conglomerates occur locally. Altogether, four units (A to D from bottom to top) can be distinguished. Especially the three lower units contain abundant fossil material, which increases again strongly in the sections B and C. The fossil abundance was first noted in the transition from the 20th to the 21st century.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 Overall, marine life predominates in the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

, which includes

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

turtles Turtles are an order (biology), order of reptiles known as Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) an ...

manatees Manatees (family Trichechidae, genus ''Trichechus'') are large, fully aquatic, mostly herbivorous marine mammals sometimes known as sea cows. There are three accepted living species of Trichechidae, representing three of the four living species ...

, and

whales Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...

. Among these, some forms, such as the genus '' Portunus'', which belongs to the decapods, suggest nearshore waters. Moreover, freshwater forms such as the

Black Pacu Black is a color which results from the absence or complete Absorption (electromagnetic radiation), absorption of visible spectrum, visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or fi ...

or the genus ''

Mylossoma ''Mylossoma'' is a genus of serrasalmids from tropical and subtropical South America, including the basins of the Amazon, Orinoco, Lake Maracaibo and Paraguay- Paraná. These common fish are found both in main river sections and floodplains. T ...

'' occur as representatives of fishes, as well as members of the Snake-necked Turtles. In the middle section of Unit C, remains of terrestrial vertebrates were also recovered. Prominent among these would be some members of the South American ungulates and the

xenarthra Xenarthra (; from Ancient Greek ξένος, xénos, "foreign, alien" + ἄρθρον, árthron, "joint") is a major clade of placental mammals native to the Americas. There are 31 living species: the anteaters, tree sloths, and armadillos. Ex ...

ns, including the remains of ''Baraguatherium''. In this area, informally called ''Valle de los vertebrados'' (the valley of vertebrates), numerous

bioturbation Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a pr ...

s can be traced in the form of

trace fossil A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

s, such as ''

Gyrolithes ''Gyrolithes'' is a trace fossil consisting of a vertically spiraling burrow, known from Cambrian strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or att ...

'', a possibly crustacean-like creature that dug corkscrew-like passage structures in the coastal soil. Based on the geological and paleontological evidence, a former mangrove-covered shallow coastal landscape can be assumed, which probably existed only for a short time. Dating using

strontium Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...

isotopes gave the Castillo Formation an age of 19.27 to 17.21 million years, corresponding to the Lower Miocene, with the section that includes the terrestrial vertebrates likely younger than 18.27 million years.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. 105–116Marcelo 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. 19–51Ascanio 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 The isolated molars of ''Baraguatherium'' were presented in a scientific paper as early as 2004, but their exact

taxonomic Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

assignment, however, was uncertain. In another publication from 2014, the authors referred the mandible to the more basal ground sloth family

Orophodontidae Mylodontidae is a family of extinct South American and North American ground sloths within the suborder Folivora of order Pilosa, living from around 23 million years ago (Mya) to 11,000 years ago. This family is most closely related to another f ...

. 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".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

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. 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.

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.

Classification

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

Folivora Sloths are a group of Neotropical xenarthran mammals constituting the suborder Folivora, including the extant arboreal tree sloths and extinct terrestrial ground sloths. Noted for their slowness of movement, tree sloths spend most of their li ...

). Within this they are often grouped together with the

and the

Scelidotheriidae Scelidotheriidae is a family of extinct ground sloths within the order Pilosa, suborder Folivora and superfamily Mylodontoidea, related to the other extinct mylodontoid family, Mylodontidae, as well as to the living two-toed sloth family Choloe ...

in the superfamily

Mylodontoidea Sloths are a group of Neotropical xenarthran mammals constituting the suborder Folivora, including the extant arboreal tree sloths and extinct terrestrial ground sloths. Noted for their slowness of movement, tree sloths spend most of their li ...

(sometimes, however, the Scelidotheriidae and the Orophodontidae are considered only as a subfamily of the

). 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.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.2019.05.043Samantha 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 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.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.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 Mylodonts appeared as early as the Oligocene, with ''Paroctodontotherium'' from Salla-Luribay in Bolivia among their earliest records.

References

{{Pilosan genera, P. Prehistoric sloths Miocene xenarthrans Miocene mammals of South America Neogene Venezuela Fossils of Venezuela Colhuehuapian Santacrucian Prehistoric placental genera Fossil taxa described in 2017