Editing Mylodon (section)

== History of research ==
=== First description ===
[[File:Richard Owen 1856.jpg|thumb|upright|left|[[Richard Owen]] (1856)]]
[[File:Mylodon holotype Owen 1840.png|thumb|left|The holotype of ''Mylodon'' used by Owen in his initial description]]
The taxonomic history of ''Mylodon'' is complex. It has involved confusion and equivocation with other mylodont forms such as ''[[Glossotherium]]'' and ''[[Paramylodon]]'' over a long period of time. Some of this complexity can be attributed to the [[first description|first describer]] of the genus itself, who is [[Richard Owen]] (1804-1892). Owen, one of the most important explorers of the Victorian era, was concerned from 1836 with fossil finds brought back by [[Charles Darwin]] from his pioneering voyage on [[HMS Beagle (1820)|HMS ''Beagle'']] to [[South America]]. The collection also included a mandible from [[Punta Alta]] near [[Bahía Blanca]] in the south of the [[Argentina]] [[Buenos Aires|Buenos Aires Province]] (specimen number [[Natural History Museum, London|NHM]] 16617). The nearly complete specimen was distinguished by a row of teeth consisting of a total of four [[molar (tooth)|molar-like]] Teeth. In an extensive 1840 paper, Owen referred the mandible to the new genus he had created, ''Mylodon,'' and named the species ''M. darwinii'' (''darwinii'' is the spelling used by Owen, but in modern times ''darwini'' is also often used; according to the [[International Rules of Zoological Nomenclature|Regulations of Zoological Nomenclature]], the former version is correct.<ref name="Iuliis et al. 2017">{{cite journal |last1=De Iuliis |first1=Gerardo |last2=Cartelle |first2=Cástor |last3=McDonald |first3=H. Gregory |last4=Pujos |first4=François |title=The mylodontine ground sloth Glossotherium tropicorum from the late Pleistocene of Ecuador and Peru |journal=Papers in Palaeontology |date=November 2017 |volume=3 |issue=4 |pages=613–636 |doi=10.1002/spp2.1088 |bibcode=2017PPal....3..613D |s2cid=135080382 |hdl=11336/64132 |hdl-access=free }}</ref>) He related the genus name to the molar-like teeth (from [[Greek language|Greek]] ''μυλη'' (''myle'') for "molar" and ''ὀδούς'' (''odoús'') for "tooth", thus translating as much as "molar tooth"), with the [[Specific name (zoology)|species epithet]] ''darwinii'' honoring Darwin as finder of the [[holotype|voucher specimen]]. As a second species besides ''M. darwinii'' Owen referred in his paper to ''M. harlani''. This form was based on a mandible and clavicle, both of which came from the Big Bone Lick in [[Boone County (Kentucky)|Boone County]] in the U.S. state of [[Kentucky]], and which [[Richard Harlan]] had already described in 1831 under the species assignment ''Megalonyx laqueatus''.<ref name="Harlan 1831">{{cite journal |id={{ProQuest|135712153}} |first1=Richard |last1=Harlan |title=Description of the jaws, teeth, and clavicle of the Megalonyx laqueatus |journal=Monthly American Journal of Geology and Natural Science |volume=1 |issue=2 |date=August 1831 |pages=74–76 }}</ref> Owen, however, recognized similarities in the construction of the mandible to his ''M. darwinii'' and renamed Harlan's form.<ref name="Owen 1840">Richard Owen: Fossil Mammalia. In: Charles Darwin (ed.): Zoology of the Voyage of HMS Beagle, under the command of Captain Fitzroy, during the years 1832 to 1836. Part I. Fossil Mammals. London, 1840, pp. 12-111 (pp. 63-73) ( biodiversitylibrary.org ).</ref> Harlan used an essay two years later to comment on Owen's choice of name regarding ''Mylodon,'' which he felt was not very descriptive. According to him, the name could be applied to almost any extinct mammalian form because almost all of them had the posterior molars. Moreover, the name would be inappropriate because, starting from the [[Latin]] version ''dens molaris'' for "molar tooth" and the second part of speech ''don'' (from ''dens'' for "tooth"), there is a duplication that would translate as "molar tooth-tooth".<ref name="Harlan 1842"/<ref name="Juan Carlos Fernicola 2009, pp. 147-159">{{cite journal |last1=Fernicola |first1=Juan Carlos |last2=Vizcaíno |first2=Sergio F. |last3=De Iuliis |first3=Gerardo |title=The fossil mammals collected byCharles Darwin in South America during his travels on board the HMS Beagle |journal=Revista de la Asociación Geológica Argentina |date=April 2009 |volume=64 |issue=1 |pages=147–159 |url=http://www.scielo.org.ar/scielo.php?pid=S0004-48222009000100016&script=sci_abstract&tlng=pt |citeseerx=10.1.1.1061.9082 }}</ref> Regardless, Owen's establishment of the genus ''Mylodon'' with two species resulted in the extinct sloth representative being distributed in both South and North America.<ref name="Juan Carlos Fernicola 2009, pp. 147-159"/><ref name="Vizcaino et al. 2009">{{cite journal |last1=Vizcaíno |first1=Sergio F. |last2=Fariña |first2=Richard A. |last3=Fernicola |first3=Juan Carlos |title=Young Darwin and the ecology and extinction of pleistocene south american fossil mammals |journal=Revista de la Asociación Geológica Argentina |date=April 2009 |volume=64 |issue=1 |pages=160–169 |url=http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0004-48222009000100017 }}</ref>

=== ''Glossotherium'', ''Grypotherium'' and ''Paramylodon'' ===
[[File:Glossotherium skull lithographic plate.jpg|thumb|right|Skull of ''[[Glossotherium]]'' with typical short and broad snout and open nasal cavity]]
Owen, in his 1840 work, established the genus ''Glossotherium'' in addition to ''Mylodon'', but without designation of a specific species. The basis here was a posterior skull fragment taken from the riverbed of the Arroyo Sarandi in the [[Uruguay]] department of [[Soriano Department|Soriano]]. In contrast to ''Mylodon'', for which Owen assumed a kinship proximity to the other large ground sloths known at the time, such as ''[[Megatherium]]'' or ''[[Megalonyx]]'', he placed ''Glossotherium'' in a series with the [[anteaters]] and with the [[pangolins]], respectively, and postulated an insectivorous lifestyle for the animals.<ref name="Owen 1840"/> Two years later, however, Owen discarded the name ''Glossotherium'' again. This occurred in the course of processing a nearly complete skeleton that had been discovered the year before in the flood plains of the [[Río de la Plata]] north of [[Buenos Aires]]. The largely intact skull was characterized by a short and broad snout and by a dentition consisting of a total of 18 teeth, of which the foremost tooth in each case showed a canine design. Based on the similarities in dental structure with the flat, molar-like teeth, Owen placed the skeleton in the genus ''Mylodon'' and introduced the new species ''M. robustus.'' The skull fragment that he had originally placed in ''Glossotherium'' he now associated with ''M. darwinii''.<ref name="Owen 1842">Richard Owen: Description of the skeleton of an extinct gigantic Sloth, Mylodon robustus, Owen, with observations on the osteology, natural affinities, and probable habitats of the Megatherioid quadrupeds in general. London, 1842, pp. 1-176 (especially p. 154) ( archive.org ).</ref> As a result of this study, three species of the genus ''Mylodon'' already existed in the 1840s.<ref name="Juan Carlos Fernicola 2009, pp. 147-159"/><ref name="mcafee2009">{{cite journal |last1=Mcafee |first1=Robert K. |title=Reassessment of the cranial characters of Glossotherium and Paramylodon (Mammalia: Xenarthra: Mylodontidae) |journal=Zoological Journal of the Linnean Society |date=April 2009 |volume=155 |issue=4 |pages=885–903 |doi=10.1111/j.1096-3642.2008.00468.x |doi-access=free }}</ref>

A skull including mandible found at [[Pergamino]] in Buenos Aires Province served the Danish zoologist [[Johannes Theodor Reinhardt]] (1816-1882) in 1879 as the basis for a comprehensive description. Characteristic of the skull was the narrow snout and a closed nasal arch, which was formed by the firm adhesion of the nasal bone to the middle jaw bone. Furthermore, the dentition consisted of a total of 16 teeth, the upper front canine-like tooth was reduced in each case, in the lower jaw, however, sat four molar-like teeth each. Reinhardt noticed similarities to ''M. darwinii'' in the construction of the lower jaw, but in the skull design his find deviated clearly from the broad-nosed ''M. robustus'' by the narrow snout. However, according to Reinhardt, there were matches in Owen's ''Glossotherium'' skull fragment with corresponding skull sections in ''M. robustus''. Based on the clear parallels between ''M. darwinii'' and his narrow-beaked skull finding, Reinhardt propagated the new genus ''Grypotherium'' with ''Grypotherium darwinii'' as the [[type species]].<ref name="Reinhardt 1879">Johannes Theodor Reinhardt: Beskrivelse af Hovedskallen af et Kæmpedovendyr, Grypotherium darwini. In: Det Kongelige Danske Videnskabernes Selskabs Skrifter. 5 Række. Naturvidenskabelig og Mathematisk Afdeling 12 (5), 1879, pp. 351–381 ( archive.org ).</ref> A different approach was taken by [[Florentino Ameghino]] (1854-1911) about ten years later. He confirmed in 1889, the separation of both ''M. darwinii'' and ''M. robustus'' not only at the species level, but also at the genus level. Deviating from Reinhardt, but agreeing with Owen, he considered the mandible of ''M. darwinii'' and the skull fragment of ''Glossotherium'' to belong together. Since in this scenario ''Glossotherium'' possessed [[principle of priority|priority]] over ''Mylodon'' (Owen mentioned the former over the latter in 1840) and ''Grypotherium,'' Ameghino introduced the species ''Glossotherium darwinii.'' In contrast, he left the status of ''M. robustus'' untouched.<ref name="Ameghino 1889">Florentino Ameghino: Contribución al conocimiento de los mamíferos fósiles de la República Argentina. In: Actas de la Academia Nacional de Ciencias. Volume 6, 1889, pp. 1-1027 (pp. 734-744).</ref> [[Arthur Smith Woodward]] (1864-1944), in turn, followed Reinhardt's reasoning. In a paper published in 1900, he presented findings from ground sloths of southern [[Patagonia]] and at the same time revised Charles Darwin's collection. In doing so, he equated the mandible of ''M. darwinii'' with Reinhardt's ''Grypotherium'' and subsequently recovered ''Grypotherium darwinii''. Smith Woodward assigned the skull fragment of ''Glossotherium'' to ''M. robustus'' by analogy with Reinhardt.<ref name="woodward1900"/><ref name="McDonald 1995">{{cite journal |last1=McDonald |first1=H. Gregory |title=Gravigrade xenarthrans from the early Pleistocene Leisey Shell Pit lA, Hillsborough County, Florida |journal=Bulletin of the Florida Museum of Natural History |volume=37 |issue=11 |year=1995 |pages=245–373 |doi=10.58782/flmnh.tdzu5337 |url=https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-11.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.floridamuseum.ufl.edu/wp-content/uploads/sites/35/2017/03/Vol-37-No-11.pdf |archive-date=2022-10-09 |url-status=live }}</ref><ref name="Juan Carlos Fernicola 2009, pp. 147-159" /><ref name="mcafee2009"/>