Megalonychidae

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Megalonychidae
Megalonyx wheatleyi skeleton & restoration.jpg
Megalonyx wheatleyi skeleton and restoration
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Pilosa
Superfamily: Megatherioidea
Family:† Megalonychidae
Gervais, 1855
Type genus
†Megalonyx
Jefferson, 1799
Subgroups

See text

Megalonychidae is an extinct family of sloths including the extinct Megalonyx [1] . Megalonychids first appeared in the early Oligocene, about 35 million years (Ma) ago, in southern Argentina (Patagonia). [2] There is, however, one possible find dating to the Eocene, about 40 Ma ago, on Seymour Island in Antarctica (which was then still connected to South America). [3] They first reached North America by island-hopping across the Central American Seaway, about 9 million years ago, [4] prior to formation of the Isthmus of Panama about 2.7 million years ago (which led to the main pulse of the Great American Interchange). Some megalonychid lineages increased in size as time passed. The first species of these were small and may have been partly tree-dwelling, whereas the Pliocene (about 5 to 2 million years ago) species were already approximately half the size of the huge Late Pleistocene Megalonyx jeffersonii from the last ice age. [5]

Contents

It was formerly believed, based on morphological comparisons, that Greater Antilles sloths and extant arboreal two-toed sloths were part of this family. However, molecular results based on sequences from collagen [6] and mitochondrial DNA [7] have shown that the former represent a basal branch of the sloth radiation, while the latter are more closely related to mylodontid sloths. The megalonychids plus nothrotheriid and megatheriid sloths, together with living three-toed sloths, make up the sloth superfamily Megatherioidea. [6] [7]

Megalonychidae, along with all other mainland ground sloths became extinct in North and South America around the end of the Late Pleistocene, approximately 12,000 years ago, as part of the Quaternary extinction event following the arrival of humans to the Americas. [8]

Evolution

Megalonyx jeffersonii skeleton cast produced and distributed by Triebold Paleontology Incorporated Megalonyx Clean.png
Megalonyx jeffersonii skeleton cast produced and distributed by Triebold Paleontology Incorporated

Megalonyx , which means "giant claw", is a widespread North American genus that lived past the close of the last (Wisconsin) glaciation, when so many large mammals died out. Remains have been found as far north as Alaska and the Yukon. [9] [10] Ongoing excavations at Tarkio Valley in southwest Iowa may reveal something of the familial life of Megalonyx. An adult was found in direct association with two juveniles of different ages, suggesting that adults cared for young of different generations. [11] [12]

The earliest known North American megalonychid, Pliometanastes protistus, lived in Florida and the southern U.S. about 9 million years ago, and is believed to have been the predecessor of Megalonyx. Several species of Megalonyx have been named; in fact, a 2000 article by Harington et al. in Arctic claimed that "nearly every good specimen has been described as a different species". [9] A broader perspective on the group, accounting for age, sex, individual and geographic differences, indicates that only three species are valid (M. leptostomus, M. wheatleyi, and M. jeffersonii) in the late Pliocene and Pleistocene of North America. [13] Although work by McDonald lists five species.

Jefferson's ground sloth has a special place in modern paleontology, for Thomas Jefferson's "memoir" on Megalonyx, read before the American Philosophical Society of Philadelphia, on 10 March 1797 [1] , marked the beginning of vertebrate paleontology in North America. [9] Jefferson's paper was published, with an accompanying description and illustrations of the Megalonyx fossils by Casper Wistar, in 1799 [1] . When Lewis and Clark set out, Jefferson instructed Meriwether Lewis to keep an eye out for ground sloths. He was hoping they would find some living in the Western range. Megalonyx jeffersonii was named after Thomas Jefferson in 1822. [1] [9]

Taxonomy

The following sloth family phylogenetic tree is based on collagen and mitochondrial DNA sequence data (see Fig. 4 of Presslee et al., 2019). [14]

Folivora

A morphological tree of Megalonychidae, based on the work of Stinnesbeck and colleagues (2021). [15] (Note that this tree does not conform to genetic studies, as it includes the Caribbean sloths Neocnus, Parocnus Megalocnus and Arcatocnus which have been placed in the separate family Megalocnidae, well as the two toed sloths (Choloepus), which are placed in the clade Mylodontoidea). [16]

Total evidence phylogeny after Tejada et al. 2023. [16]


Genera

Related Research Articles

<i>Megatherium</i> Genus of ground sloth (extinct)

Megatherium is an extinct genus of ground sloths endemic to South America that lived from the Early Pliocene through the end of the Pleistocene. It is best known for the elephant-sized type species M. americanum, sometimes known as the giant ground sloth, or the megathere, native to the Pampas through southern Bolivia during the Pleistocene. Various other smaller species belonging to the subgenus Pseudomegatherium are known from the Andes.

<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. Ground sloths varied widely in size, with the largest genera Megatherium and Eremotherium being around the size of elephants. Ground sloths are a paraphyletic group, as living tree sloths are thought to have evolved from ground sloth ancestors.

<span class="mw-page-title-main">Mylodontidae</span> Extinct family of ground sloths

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 family of extinct ground sloths, Scelidotheriidae, as well as to the extant arboreal two-toed sloths, family Choloepodidae; together these make up the superfamily Mylodontoidea. Phylogenetic analyses based on morphology uncovered the relationship between Mylodontidae and Scelidotheriidae; in fact, the latter was for a time considered a subfamily of mylodontids. However, molecular sequence comparisons were needed for the correct placement of Choloepodidae. These studies have been carried out using mitochondrial DNA sequences as well as with collagen amino acid sequences. The latter results indicate that Choloepodidae is closer to Mylodontidae than Scelidotheriidae is. The only other living sloth family, Bradypodidae, belongs to a different sloth radiation, Megatherioidea.

<span class="mw-page-title-main">Scelidotheriidae</span> Extinct family of prehistoric ground sloths

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 Choloepodidae. The only other extant family of the suborder Folivora is the distantly related Bradypodidae. Erected as the family Scelidotheriidae by Ameghino in 1889, the taxon was demoted to a subfamily of Mylodontidae by Gaudin in 1995. However, recent collagen sequence data indicates the group is less closely related to Mylodon and Lestodon than Choloepus is, and thus it has been elevated back to full family status by Presslee et al. (2019).

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

Megalonyx is an extinct genus of ground sloths of the family Megalonychidae, native to North America. It evolved during the Pliocene Epoch and became extinct during at the end of the Late Pleistocene, living from ~5 million to ~13,000 years ago. The type species, M. jeffersonii, the youngest and largest known species, measured about 3 meters (9.8 ft) in length and weighed up to 1,000 kilograms (2,200 lb).

<span class="mw-page-title-main">Pilosa</span> Order of mammals

The order Pilosa is a clade of xenarthran placental mammals, native to the Americas. It includes anteaters and sloths. The name comes from the Latin word for "hairy".

<span class="mw-page-title-main">Two-toed sloth</span> Genus of sloth

Choloepus is a genus of xenarthran mammals of Central and South America within the monotypic family Choloepodidae, consisting of two-toed sloths, sometimes also called two-fingered sloths. The two species of Choloepus, Linnaeus's two-toed sloth and Hoffmann's two-toed sloth, were formerly believed on the basis of morphological studies to be the only surviving members of the sloth family Megalonychidae, but have now been shown by molecular results to be closest to extinct ground sloths of the family Mylodontidae.

<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.

Pliometanastes is an extinct genus of ground sloths of the family Megalonychidae endemic to North America during the Late Miocene epoch through very early Pliocene epoch. Its fossils have been found in Costa Rica and across the southern United States from California to Florida.

Miocnus is an extinct genus of ground sloths of the family Megalocnidae endemic to Cuba during the Pleistocene and very early Holocene epochs, living from 1.8 Mya—11,000 years ago, existing for approximately 1.789 million years.

The mammalian order Pilosa, which includes the sloths and anteaters, includes various species from the Caribbean region. Many species of sloths are known from the Greater Antilles, all of which became extinct over the last millennia, but some sloths and anteaters survive on islands closer to the mainland.

<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.

Xibalbaonyx is an extinct genus of megalonychid ground sloth known from the Late Pleistocene of Mexico. Three species are known: X. oviceps and X. exiniferis from the Yucatan peninsula and X. microcaninus from Jalisco. The genus is named after Xibalba, the underworld in Maya mythology.

Nohochichak is an extinct genus of megalonychid ground sloth from the Late Pleistocene (Rancholabrean) of the Yucatan Peninsula in Mexico.

<span class="mw-page-title-main">Megalocnidae</span> Extinct Greater Antilles sloth family

Megalocnidae is an extinct family of sloths, native to the islands of the Greater Antilles from the Early Oligocene to the Mid-Holocene. They are known from Cuba, Hispaniola and Puerto Rico, but are absent from Jamaica. While they were formerly placed in the Megalonychidae alongside two-toed sloths and ground sloths like Megalonyx, recent mitochondrial DNA and collagen sequencing studies place them as the earliest diverging group basal to all other sloths. or as an outgroup to Megatherioidea. They displayed significant diversity in body size and lifestyle, with Megalocnus being terrestrial and probably weighing several hundred kilograms, while Neocnus was likely arboreal and similar in weight to extant tree sloths, at less than 10 kilograms.

Meizonyx is an extinct genus of megalonychid ground sloth from the Pleistocene of El Salvador and southern Mexico. The type and only species, Meizonyx salvadorensis, was described in 1985 from a mandible found in Barranca del Sisimico and other remains found at Rio Tomayate in El Salvador considered to be Middle Pleistocene in age. Later, in 2021, two partial skeletons were described from Late Pleistocene aged deposits in Sistema Huautla cave in, Oxaca, Mexico, with one of these dating to around 12,562 ± 130 years Before Present. It is considered closely related to Xibalbaonyx. It is thought to be comparable or somewhat greater in size than Megalonyx jeffersonii. It inhabited relatively mountainous areas.

<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.

Mesopotamocnus is an extinct genus of megalonychid ground sloth that lived during the Late Miocene in what is now Argentina. Fossils have been found in the Ituzaingó Formation of Argentina.

Neonematherium is an extinct genus of scelidotheriid ground sloths that lived in Argentina, Chile, and Colombia during the Early to Late Miocene. Fossils have been found in the Honda Group of Colombia, and the Río Frías Formation of Chile.

<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 Babcock, Loren E. (2024-03-18). "Nomenclatural history of Megalonyx Jefferson, 1799 (Mammalia, Xenarthra, Pilosa, Megalonychidae)". ZooKeys (1195): 297–308. doi: 10.3897/zookeys.1195.117999 . ISSN   1313-2970. PMC   10964019 .
  2. ↑ Morgan, Gary S. (2002). "Late Rancholabrean Mammals from Southernmost Florida, and the Neotropical Influence in Florida Pleistocene Faunas". In Emry, Robert J. (ed.). Cenozoic Mammals of Land and Sea: Tributes to the Career of Clayton E. Ray. Vol. 93. Washington, D.C.: Smithsonian Institution Press. pp. 15–38.{{cite book}}: |journal= ignored (help)
  3. ↑ Vizcaíno, Sergio F.; Scillato-Yané, Gustavo J. (December 1995). "An Eocene tardigrade (Mammalia, Xenarthra) from Seymour Island, West Antarctica". Antarctic Science. 7 (4): 407–408. Bibcode:1995AntSc...7..407V. doi:10.1017/S0954102095000563. S2CID   129075656.
  4. ↑ Tedford, R.H.; Albright, L.B.; Barnosky, A.D.; Ferrusquaia-Villafranca, I.; Hunt, R.M.; Storer, J.E.; Swisher, C.C.; Voorhies, M.R.; Webb, S.D.; Whistler, D.P. (21 April 2004). "Mammalian Biochronology of the Arikareean Through Hemiphilian Interval (Late Oligocene Through Early Pliocene Epochs)". In Woodburne, M.O. (ed.). Late Cretaceous and Cenozoic Mammals of North America: Biostratigraphy and Geochronology. Columbia University Press. pp. 169–231, see also p. 337. ISBN   978-0231503785. OCLC   880404891.
  5. ↑ J.L. White (1993)
  6. 1 2 Presslee, S.; Slater, G. J.; Pujos, F.; Forasiepi, A. M.; Fischer, R.; Molloy, K.; Mackie, M.; Olsen, J. V.; Kramarz, A.; Taglioretti, M.; Scaglia, F.; Lezcano, M.; Lanata, J. L.; Southon, J.; Feranec, R.; Bloch, J.; Hajduk, A.; Martin, F. M.; Gismondi, R. S.; Reguero, M.; de Muizon, C.; Greenwood, A.; Chait, B. T.; Penkman, K.; Collins, M.; MacPhee, R.D.E. (2019). "Palaeoproteomics resolves sloth relationships" (PDF). Nature Ecology & Evolution. 3 (7): 1121–1130. Bibcode:2019NatEE...3.1121P. doi:10.1038/s41559-019-0909-z. PMID   31171860. S2CID   174813630.
  7. 1 2 Delsuc, F.; Kuch, M.; Gibb, G. C.; Karpinski, E.; Hackenberger, D.; Szpak, P.; Martínez, J. G.; Mead, J. I.; McDonald, H. G.; MacPhee, R.D.E.; Billet, G.; Hautier, L.; Poinar, H. N. (2019). "Ancient Mitogenomes Reveal the Evolutionary History and Biogeography of Sloths". Current Biology. 29 (12): 2031–2042.e6. Bibcode:2019CBio...29E2031D. doi: 10.1016/j.cub.2019.05.043 . hdl: 11336/136908 . PMID   31178321.
  8. ↑ Steadman, D. W.; Martin, P. S.; MacPhee, R. D. E.; Jull, A. J. T.; McDonald, H. G.; Woods, C. A.; Iturralde-Vinent, M.; Hodgins, G. W. L. (2005-08-16). "Asynchronous extinction of late Quaternary sloths on continents and islands". Proceedings of the National Academy of Sciences of the United States of America . 102 (33). National Academy of Sciences: 11763–11768. Bibcode:2005PNAS..10211763S. doi: 10.1073/pnas.0502777102 . PMC   1187974 . PMID   16085711.
  9. 1 2 3 4 Harrington (1993)
  10. ↑ McDonald, H. G.; Harington, C. R.; De Iuliis, G. (September 2000). "The Ground Sloth Megalonyx from Pleistocene Deposits of the Old Crow Basin, Yukon, Canada" (PDF). Arctic . 53 (3). Calgary, Alberta: The Arctic Institute of North America: 213–220. doi:10.14430/arctic852 . Retrieved 2008-08-16.
  11. ↑ Semken and Brenzel, "The Tarkio Valley Sloth Project · Project Summary". Archived from the original on 2009-01-01. Retrieved 2009-09-25.
  12. ↑ Semken; Brenzel (2007). "One Sloth Becomes Three". Newsletter of the Iowa Archeological Society. 57: 1.
  13. ↑ Kurtén & Anderson, 1980, p. 136.
  14. ↑ Presslee, S.; Slater, G. J.; Pujos, F.; Forasiepi, A. M.; Fischer, R.; Molloy, K.; et al. (2019). "Palaeoproteomics resolves sloth relationships" (PDF). Nature Ecology & Evolution. 3 (7): 1121–1130. Bibcode:2019NatEE...3.1121P. doi:10.1038/s41559-019-0909-z. PMID   31171860. S2CID   174813630. Archived (PDF) from the original on 12 September 2020. Retrieved 18 September 2020.
  15. ↑ Stinnesbeck, Sarah R.; Stinnesbeck, Wolfgang; Frey, Eberhard; Avilés Olguín, Jerónimo; González, Arturo González (2021-10-03). "Xibalbaonyx exinferis n. sp. (Megalonychidae), a new Pleistocene ground sloth from the Yucatán Peninsula, Mexico". Historical Biology. 33 (10): 1952–1963. Bibcode:2021HBio...33.1952S. doi:10.1080/08912963.2020.1754817. ISSN   0891-2963. S2CID   219425309.
  16. 1 2 Tejada, Julia V; Antoine, Pierre-Olivier; Münch, Philippe; Billet, Guillaume; Hautier, Lionel; Delsuc, Frédéric; Condamine, Fabien L (2023-12-02). Wright, April (ed.). "Bayesian Total-Evidence Dating Revisits Sloth Phylogeny and Biogeography: A Cautionary Tale on Morphological Clock Analyses". Systematic Biology. doi: 10.1093/sysbio/syad069 . ISSN   1063-5157. PMID   38041854.

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