Archaeomylodon

Last updated

Archaeomylodon
Temporal range: Middle Pleistocene (Ensenadan)
~0.700  Ma
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
↓
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Pilosa
Family:† Mylodontidae
Subfamily:† Mylodontinae
Genus:† Archaeomylodon
Brambilla and Ibarra 2018
Species:
†A. sampedrinensis
Binomial name
†Archaeomylodon sampedrinensis
Brambilla and Ibarra 2018

Archaeomylodon is an extinct genus of mylodontine ground sloths that lived during the Middle Pleistocene of what is now Argentina. It is known so far only from a single skull, which in its dimensions corresponds to those of the giant Lestodon . However, the skull differs from this one by its narrower and higher snout. In addition, the anterior canine teeth, which are usually large in many mylodonts, are greatly reduced. The find comes from the Pampa region of South America and was deposited in about 700,000 years old sediments.

Contents

Discovery and naming

The only known find of Archaeomylodon so far, was discovered in Cantera Iglesias near Partido San Pedro in the north of the Argentine province of Buenos Aires. The site is located south of the Río Paraná in the Pampa region of South America. The skull was deposited there in calcareous deposits in the upper section of the Ensenada Formation. According to radiometric measurements, these could be determined to be about 700,000 years old, corresponding to the beginning of the Middle Pleistocene. [1] The genus name, Archaeomylodon, is composed of the Greek words ἀρχαῖος archaios for "old" and the genus name Mylodon as the type genus of the Mylodontidae. The prefix archaeo- refers to the older age of the new genus in relation to the mostly Upper Pleistocene finds of other mylodonts. The only known species is Archaeomylodon sampedrinensis. The species epithet is a reference to the locality near San Pedro. [1]

Description

Archaeomylodon is so far known only from a skull of an adult individual. The skull has a length of 59.7 cm, the width of the skull is 23.8 cm and the height is 21 cm. Thus, it belongs to the largest known mylodontid. Archaeomylodon might have reached around the same dimensions of the giant Lestodon, which weighs up to 4 tons. [2] The skull showed an elongated tube-like shape typical for large ground sloths and was built almost rectangular in top view. Only in the area of the eyes was there a small constriction as well as a small widening in the nasal bone-upper jaw section. The anterior section was narrower than in Lestodon, but broader than in Mylodon . In lateral view, the frontal line was flat, lacking a dome-like bulge such as occurred in Glossotherium or Thinobadistes . The nasal bone was oriented slightly upwards. In anterior view, this resulted in a high nasal opening, reminiscent of Mylodon and differing from the distinctly flat one in Glossotherium. The anterior zygomatic arch originated from the maxilla above the third molar-like tooth. The parasagittal ridges on the parietal bone were widely spaced, comparable to Mylodon but unlike the close position to each other in Lestodon. The occipital bone in posterior view had a high and more rounded shape corresponding to Mylodon. In Lestodon and Glossotherium this was rather flattened and therefore broader. On the underside of the skull, the margins of the palate were largely parallel to each other and not divergently oriented anteriorly as in Glossotherium and Lestodon. [1]

The dentition has been fossilized only incompletely. However, it consisted of five teeth per jaw half. The foremost tooth was shaped like canines as in many mylodonts, while the posterior four were shaped like molars (molariform). This is reminiscent of Lestodon and Glossotherium, but differed from Mylodon, in which the upper caniniform teeth were receded. Differing from the former two, the rows of teeth did not diverge clearly towards the front, but were rather parallel to each other. Only in the most anterior region they diverged slightly. Thus, the two canine-like anterior teeth were not displaced laterally outward, but were much closer together. In addition, the distinct diastema to the following first molar-like tooth was missing. Altogether the caniniform tooth was very small and thus in its size already strongly reduced, which reminded of Mylodonopsis and formed a clear difference to the large teeth in Lestodon and Glossotherium. In cross section it possessed a rather circular shape. Of the following teeth, only the rearmost molar is preserved, the others being indicated by the position of their respective alveoli. It possessed a typically flat occlusal surface design for mylodonts consisting of two lobate sections, the posterior one being smaller than the anterior one. The entire alveolar molar row measured about 14.4 cm in length. [2]

Paleobiology

In general, mylodonts are considered specialized grazers. Based on the snout shape of various extinct sloths, an attempt was made to reconstruct food preferences. Here, broad snouts indicate grazers and narrow snouts indicate leaf-eaters comparable to the difference between the white rhinoceros and the black rhinoceros. Archaeomylodon, with its narrower snout, differs markedly from Lestodon and Glossotherium. [3] [4] It is therefore suggested that the animals may have fed generalistically on plant foods. [1]

Classification

Archaeomylodon is an extinct genus of the also extinct family Mylodontidae. The Mylodontidae represent a branch of the suborder of sloths (Folivora). Within this they are often grouped together with the Scelidotheriidae in the superfamily Mylodontoidea (sometimes, however, the Scelidotheriidae is considered only as a subfamily of the Mylodontidae). [5] 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-toed sloths of the genus Choloepus, one of the two extant sloth genera. [6] [7] 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. [8] [9] Mylodonts appeared as early as the Oligocene, with Paroctodontotherium from Salla-Luribay in Bolivia among their earliest records. [10]

The combination of features of Archaeomylodon such as the tubular skull, the heterodont dentition with posterior molariform and an anterior caniniform tooth, and the design of the molariform teeth in general clearly refer the genus to the mylodonts. The anterior caniniform tooth is formed very small in Archaeomylodon, which distinguishes the shape from other large mylodonts such as Lestodon and Glossotherium. According to phylogenetic analyses, the greatest similarity is to Mylodon, which occurred mainly in the southern part of South America. In contrast to Archaeomylodon, Mylodon has a more reduced dentition, with the anterior canine teeth completely retracted. Archaeomylodon was found to be the sister taxon to Mylodon.

Below is the phylogeny recovered in the description of Archaeomylodon. [1]


Mylodontidae


Related Research Articles

<i>Mylodon</i> Extinct genus of mylodontid ground sloths

Mylodon is an extinct genus of ground sloth belonging to the family Mylodontidae, known from southern South America. With a total length of 3 to 4 m and a body mass of 1-2 tonnes, it is one of the largest mylodontids.

<span class="mw-page-title-main">Ground sloth</span> Diverse group of extinct sloth species

Ground sloths are a diverse group of extinct sloths in the mammalian superorder Xenarthra. They varied widely in size with the largest, belonging to genera Lestodon, Eremotherium and Megatherium, being around the size of elephants. Ground sloths represent a paraphyletic group, as living tree sloths are thought to have evolved from ground sloth ancestors.

<i>Glossotherium</i> Extinct genus of ground sloths

Glossotherium is an extinct genus of large mylodontid ground sloths of the subfamily Mylodontinae. It represents one of the best-known members of the family, along with Mylodon and Paramylodon. Reconstructed animals were between 3 and 4 metres long and possibly weighed up to 1,002.6–1,500 kg. The majority of finds of Glossotherium date from the Middle and Upper Pleistocene, around 300,000 to 10,000 years ago, with a few dating older, as far back Pliocene, about 3.3-3 million years ago. The range included large parts of South America, east of the Andes roughly from latitude 20 to 40 degrees south, leaving out the Amazon Basin in the north. In western South America, finds are also documented north of the equator. The animals largely inhabited the open landscapes of the Pampas and northern savanna regions.

<i>Eremotherium</i> Extinct genus of giant ground sloth

Eremotherium is an extinct genus of giant ground sloth in the family Megatheriidae. Eremotherium lived in southern North America, Central America, and northern South America from the Pliocene, around 5.3 million years ago, to the end of the Late Pleistocene, around 10,000 years ago. Eremotherium was one of the largest ground sloths, with a body size comparable to elephants, weighing around 4–6.5 tonnes and measuring about 6 metres (20 ft) long, slightly larger than its close relative Megatherium.

<i>Paramylodon</i> Extinct genus of ground sloths from North America

Paramylodon is an extinct genus of ground sloth of the family Mylodontidae endemic to North America during the Pliocene through Pleistocene epochs, living from around ~4.9 Mya–12,000 years ago.

<i>Lestodon</i> Extinct genus of ground sloths

Lestodon is an extinct genus of giant ground sloth native to South America during the Pleistocene epoch. Its fossil remains have been primarily been found in the Pampas and adjacent regions. The largest member of the family Mylodontidae, It is estimated to have weighed 4,100 kilograms. It was a herbivore and primarily fed on the grasses and low-growing plants.

<i>Glyptodon</i> Genus of large, heavily armored mammals

Glyptodon is a genus of glyptodont, an extinct group of large, herbivorous armadillos, that lived from the Pliocene, around 3.2 million years ago, to the early Holocene, around 11,000 years ago, in South America. It is one of, if not the, best known genus of glyptodont. Glyptodon has a long and storied past, being the first named extinct cingulate and the type genus of the subfamily Glyptodontinae. Fossils of Glyptodon have been recorded as early as 1814 from Pleistocene aged deposits from Uruguay, though many were incorrectly referred to the ground sloth Megatherium by early paleontologists.

<i>Catonyx</i> Extinct genus of ground sloths

Catonyx is an extinct genus of ground sloth of the family Scelidotheriidae, endemic to South America during the Pliocene and Pleistocene epochs. It lived from 2.5 Ma to about 10,000 years ago, existing for approximately 2.49 million years. The most recent date obtained is about 9600 B.P.

<span class="mw-page-title-main">Mylodontinae</span> Extinct subfamily of mammals

Mylodontinae is an extinct subfamily of ground sloths that lived from the Early Miocene to the Early Holocene epochs.

Lestobradys is an extinct genus of ground sloth, which existed in Uruguay during the Late Miocene period; Huayquerian in the South American land mammal age (SALMA). The type species is L. sprechmanni, found in the Camacho Formation of Uruguay.

<i>Ahytherium</i> Extinct genus of sloths

Ahytherium is an extinct genus of megalonychid sloth that lived during the Pleistocene of what is now Brazil. It contains a single species, A. aureum.

<i>Pseudoprepotherium</i> Extinct genus of ground sloths

Pseudoprepotherium is an extinct genus of sloths of the family Mylodontidae. It was widespread across northern South America during the Early to Late Miocene epoch around 21 to 5.3 million years ago. Fossils of the animal have been found in Brazil, Venezuela, and Peru. Pseudoprepotherium lived in a tropical climate with a water-rich environment. Their known remains are limited to limb bones, except for a few skulls and teeth. Based on these remains, they were most likely medium to large-sized mylodontid. The genus was described in 1961 and currently contains three species, which were originally assigned to the genus Prepotherium.

Megathericulus is an extinct genus of ground sloths in the Megatheriidae family. It lived during the Middle Miocene, 11-16 Ma in what is now South America. Fossils have been found principally in Argentina, Bolivia, and Peru. It is a smaller representative of the megatheres. Despite being one of the earliest-known members of the family, its dentition structure is associated with homodont teeth belonging to the more modern line of evolution. The genus was scientifically named in 1904. Only one species is currently recognized, Megathericulus patagonicus.

<i>Proeremotherium</i> Extinct genus of mammals

Proeremotherium is an extinct genus of megatheriine ground sloths in the family Megatheriidae. It lived during the Late Miocene and Early Pliocene of what is now Venezuela. So far, two largely complete skulls have been recovered in the Falcón Basin in Venezuela. The finds identify the animals as medium-sized representatives of the Megatheriidae. In the cranial anatomy, Proeremotherium resembles the later and giant Eremotherium. It is therefore assumed that the two ground sloths are directly related to each other.

Urumacotherium is an extinct genus of ground sloths of the family Mylodontidae. It lived from the Middle Miocene to the Early Pliocene of what is now Brazil, Peru and Venezuela.

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.

Simomylodon is an extinct genus of ground sloths from the family Mylodontidae. It lived from the Late Miocene to the Middle Pliocene of what is now Bolivia and Argentina, 5.3 to 2.8 million years ago. The most important find material comes from the central Altiplano in Bolivia and includes several skulls and dentition remains. Thus, the so far documented body skeleton is the best known and most significant of a Miocene representative of the Mylodontidae. On the basis of the remains, it can be concluded that it is a rather small member of the Mylodontidae. The construction of the limbs supports ground-dwelling locomotion, but this does not exclude occasional digging or climbing. The type and only known species is Simomylodon uccasamamensis.

Vassallia is an extinct genus of cingulate belonging to the family Pampatheriidae. It lived between the Middle Oligocene and the Early Pliocene in what is now South America.

Brievabradys is an extinct genus of ground sloth belonging to the family Mylodontidae that lived in Colombia during the Middle Miocene. This genus was discovered in the Honda Group of Colombia, in the strata of the Tatacoa Desert in the Huila Department with an approximate age of 13 to 11 million years ago, dating to the Middle Miocene. Brievabradys was described based on a fossilized skull and additional cranial remains found in that area.

<i>Ortotherium</i> Extinct genus of ground sloth

Ortotherium is a genus of megalonychid ground sloth from the Late Miocene Ituzaingó Formation of Entre Rios Province, Argentina. Although many species were described, the only valid species of the genus is Ortotherium laticurvatum, with many species being junior synonyms. Ortotherium is known from very fragmentary material, all of which is material from the mandible and teeth. The holotype of O. laticurvatum consists of an incomplete left dentary that had been unearthed from a series of sediments known as ‘Conglomerado osifero’ in Paraná, Argentina. Argentina paleontologist Florentino Ameghino named the species in 1885, though he would go on to name four more, invalid, species of the genus. One species however, O. brevirostrum, has been reclassified as Mesopotamocnus.

References

  1. 1 2 3 4 5 Brambilla, Luciano; Ibarra, Damián Alberto (2018-11-02). "Archaeomylodon sampedrinensis, gen. et sp. nov., a new mylodontine from the middle Pleistocene of Pampean Region, Argentina". Journal of Vertebrate Paleontology. 38 (6): e1542308. Bibcode:2018JVPal..38E2308B. doi:10.1080/02724634.2018.1542308. ISSN   0272-4634. S2CID   91874640.
  2. 1 2 Bargo, M. Susana; Vizcaíno, Sergio F.; Archuby, Fernando M.; Blanco, R. Ernesto (2000-09-25). "Limb bone proportions, strength and digging in some Lujanian (Late Pleistocene-Early Holocene) mylodontid ground sloths (Mammalia, Xenarthra)". Journal of Vertebrate Paleontology. 20 (3): 601–610. doi:10.1671/0272-4634(2000)020[0601:LBPSAD]2.0.CO;2. ISSN   0272-4634. S2CID   86036390.
  3. ↑ Bargo, M. Susana; Toledo, Néstor; Vizcaíno, Sergio F. (2006). "Muzzle of South American Pleistocene ground sloths (Xenarthra, Tardigrada)". Journal of Morphology. 267 (2): 248–263. doi:10.1002/jmor.10399. ISSN   0362-2525. PMID   16315216. S2CID   39664746.
  4. ↑ Bargo, M. Susana; Vizcaíno, Sergio F. (2008). "PALEOBIOLOGY OF PLEISTOCENE GROUND SLOTHS (XENARTHRA, TARDIGRADA): BIOMECHANICS, MORPHOGEOMETRY AND ECOMORPHOLOGY APPLIED TO THE MASTICATORY APPARATUS". Ameghiniana (in Spanish). 45 (1): 175–196. ISSN   1851-8044.
  5. ↑ Varela, Luciano; Tambusso, P Sebastián; McDonald, H Gregory; Fariña, Richard A (2018-09-15). "Phylogeny, Macroevolutionary Trends and Historical Biogeography of Sloths: Insights From a Bayesian Morphological Clock Analysis". Systematic Biology. 68 (2): 204–218. doi:10.1093/sysbio/syy058. ISSN   1063-5157. PMID   30239971.
  6. ↑ 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
  7. ↑ 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
  8. ↑ 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.
  9. ↑ 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
  10. ↑ Shockey, Bruce J.; Anaya, Federico (2011). "Grazing in a New Late Oligocene Mylodontid Sloth and a Mylodontid Radiation as a Component of the Eocene-Oligocene Faunal Turnover and the Early Spread of Grasslands/Savannas in South America". Journal of Mammalian Evolution. 2 (18): 101–115. doi:10.1007/s10914-010-9147-5. ISSN   1064-7554. S2CID   42451.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.