PBDB Taxon

Basic info	Taxonomic history	Classification	Included Taxa
Morphology	Ecology and taphonomy	External Literature Search	Age range and collections

Megalonyx

Osteichthyes - Megalonychidae

Taxonomy

Megalonyx was named by Harlan (1825). It is not extant. Its type is Megatherium jeffersonii.

It was assigned to Bradypidae by Gray (1825); to Rodimorpha by Cope (1889); to Megatheriidae by Hay (1902); to Megalonychinae by Hay (1930), Varela et al. (2019); and to Megalonychidae by Harlan (1825), Kurten and Anderson (1980), Thurmond and Jones (1981), Carroll (1988), Gaudin (1995), Cisneros (2005), Pujos et al. (2007), McDonald and Naples (2007), Albright et al. (2019), Eshelman et al. (2025).

Species

M. curvidens, M. cuvieri, M. dissimilis, M. gigas, M. gracilis, M. jeffersonii (syn. M. laqueatus, M. hogani, M. brachycephalus, M. californicus, M. milleri), M. leidyi, M. leptostomus (syn. M. rohrmani), M. loxodon, M. mathisi, M. obtusidens, M. scalper, M. sierrensis, M. tortulus, M. validus, M. wheatleyi (syn. M. sphenodon)

Synonyms

Megalonyx gracilis was named by Lund (1893).

It was considered a nomen nudum by Cartelle et al. (2009).

Synonymy list

Year	Name and author
1825	Megalonyx Gray p. 343
1825	Megalonyx Harlan
1889	Megalonyx Cope p. 660
1893	Megalonyx gracilis Lund p. 219
1902	Megalonyx Hay p. 577
1930	Megalonyx Hay p. 407
1980	Megalonyx Kurten and Anderson p. 136
1981	Megalonyx Thurmond and Jones p. 178
1988	Megalonyx Carroll
1995	Megalonyx Gaudin
2005	Megalonyx Cisneros p. 245
2007	Megalonyx McDonald and Naples p. 154
2007	Megalonyx Pujos et al.
2019	Megalonyx Albright et al. p. 153
2019	Megalonyx Varela et al.
2025	Megalonyx Eshelman et al. p. 92

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Rank	Name	Author
kingdom	Animalia	()
—	Bilateria
—	Eubilateria	Ax 1987
—	Deuterostomia
phylum	Chordata	Haeckel 1874
subphylum	Vertebrata
superclass	Gnathostomata
class	Osteichthyes
subclass	Sarcopterygii	()
subclass	Dipnotetrapodomorpha	(Nelson 2006)
subclass	Tetrapodomorpha	()
—	Tetrapoda
—	Reptiliomorpha
—	Anthracosauria
subclass	Amphibiosauria	Kuhn 1967
—	Cotylosauria	()
—	Amniota
subclass	Synapsida
—	Therapsida	()

Rank	Name	Author
infraorder	Cynodontia	()
—	Mammaliamorpha
—	Mammaliaformes
class	Mammalia
—	Cladotheria
—	Zatheria
subclass	Tribosphenida	()
subclass	Theria
—	Eutheria	()
—	Placentalia
—	Americatheria
—	Xenarthra	()
infraorder	Pilosa	Flower 1883
—	Folivora
class	Eufolivora	Delsuc et al. 2001
superfamily	Megatherioidea	Gray 1821
family	Megalonychidae	Gervais 1855
subfamily	Megalonychinae	Trouessart 1904
genus	Megalonyx	Harlan 1825

If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.

G. †Megalonyx Harlan 1825

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†Megalonyx curvidens Matthew 1924

†Megalonyx cuvieri Lund 1839

†Megalonyx dissimilis Leidy 1855

†Megalonyx gigas Marsh 1874

†Megalonyx jeffersonii Desmarest 1822 [Jefferson's ground sloth]

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Invalid names: Megalonyx brachycephalus Sellards 1941 [synonym], Megalonyx californicus Stock 1913 [synonym], Megalonyx hogani Stovall 1940 [synonym], Megalonyx laqueatus Harlan 1831 [synonym], Megalonyx milleri Lyon 1938 [synonym]

†Megalonyx leidyi Lindahl 1892

†Megalonyx leptostomus Cope 1893

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Invalid names: Megalonyx rohrmani Gustafson 1978 [synonym]

†Megalonyx loxodon Cope 1871

†Megalonyx mathisi Hirschfeld and Webb 1968

†Megalonyx obtusidens Webb and Perrigo 1985

†Megalonyx scalper Cope 1899

†Megalonyx sierrensis Sinclair 1905 [sloth]

†Megalonyx tortulus Cope 1871

†Megalonyx validus Leidy 1868

†Megalonyx wheatleyi Cope 1871

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Invalid names: Megalonyx sphenodon Cope 1871 [synonym]

Invalid names: Megalonyx gracilis Lund 1893 [nomen nudum]

Diagnosis

No diagnoses are available

Measurements

No measurements are available

Composition:

phosphaticsubp

Environment:

terrestrialsubc

Locomotion:

actively mobilec

Life habit:

ground dwellingf

Diet:

herbivoref

Reproduction:

viviparoussubc

Created:

2005-06-08 10:11:09

Modified:

2005-08-22 18:30:05

Source: f = family, subc = subclass, c = class, subp = subphylum

References: Hendy et al. 2009, Carroll 1988, Lillegraven 1979, Nowak 1991, Ji et al. 2002

Age range: base of the Hemphillian to the top of the Rancholabrean or 9.40000 to 0.01400 Ma

Collections (163 total)

Time interval	Ma	Country or state	Original ID and collection number
Hemphillian	9.4 - 4.7	USA (Oklahoma)	Megalonychidae indet. (18304)
Hemphillian	9.4 - 4.7	USA (Nebraska)	M. curvidens (18033 18201 18323 18441) M. sp. (18043 18225)
Hemphillian	9.4 - 4.7	Mexico (Guanajuato)	M. sp. (18718 175257)
Hemphillian	9.4 - 4.7	USA (California)	Megalonychidae indet. (19479) M. mathisi (19187)
Hemphillian	9.4 - 4.7	USA (Oregon)	Megalonychidae indet. (19015) M. sp. (19116)
Hemphillian	9.4 - 4.7	Mexico (Hidalgo)	M. sp. (18746)
Hemphillian	9.4 - 4.7	Mexico (Jalisco)	M. sp. (189788 189790)
Hemphillian	9.4 - 4.7	Mexico (Nayarit)	M. sp. (212338)
Late/Upper Hemphillian	9.4 - 4.7	USA (Texas)	M. sp. (18036)
Late/Upper Hemphillian	9.4 - 4.7	USA (Nebraska)	M. curvidens (18126 18247 18359 18499)
Late/Upper Hemphillian	9.4 - 4.7	Mexico (Guanajuato)	M. sp. (18737)
Blancan	4.7 - 1.4	USA (Kansas)	M. leptostomus (19942) M. sp. (19932 19936 19939)
Blancan	4.7 - 1.4	USA (Florida)	M. leptostomus (19753 19754 19764)
Blancan	4.7 - 1.4	Mexico (Hidalgo)	M. sp. (20079)
Blancan	4.7 - 1.4	USA (Texas)	M. leptostomus (20022 20023 20033) M. sp. (20034 20038 20052)
Blancan	4.7 - 1.4	USA (Idaho)	M. leptonyx (19808) M. leptostomus (19911 19913)
Blancan	4.7 - 1.4	USA (Nebraska)	M. leptostomus (19959) M. sp. (19954 19955)
Blancan	4.7 - 1.4	Mexico (Sonora)	M. wheatleyi (20322)
Blancan	4.7 - 1.4	USA (Arizona)	M. sp. (19653 19656 19657 19658)
Blancan	4.7 - 1.4	USA (New Mexico)	M. leptostomus (19655 19968)
Blancan	4.7 - 1.4	USA (Washington)	M. leptostomus (20062) M. rohrmanni (20063)
Blancan	4.7 - 1.4	USA (California)	M. sp. (19667 20112 20115 20118 20121) Xenarthra indet. (19714)
Blancan	4.7 - 1.4	USA (Nevada)	M. leptostomus (20009)
Blancan	4.7 - 1.4	Mexico (Baja California Sur)	M. sp. (20075)
Blancan - Irvingtonian	4.7 - 0.21	USA (South Dakota)	M. leptostomus (20020)
Blancan - Irvingtonian	4.7 - 0.21	USA (New Mexico)	M. wheatleyi (20397)
Blancan - Irvingtonian	4.7 - 0.21	El Salvador	M. sp. (70118)
Late/Upper Pliocene	3.6 - 2.58	USA (Texas)	M. sp. (191451)
Piacenzian	3.6 - 2.58	USA (California)	M. sp. (19703)
Gelasian	2.58 - 1.8	USA (Florida)	M. leptostomus (20384) M. sp. (19758)
Early/Lower Pleistocene	2.58 - 0.774	USA (Florida)	M. leptostomus (19750 98313)
Early/Lower Pleistocene	2.58 - 0.774	USA (South Carolina)	M. leptostomus (206955)
Early/Lower Pleistocene	2.58 - 0.774	USA (Arizona)	M. jeffersonii (85145)
Early/Lower Pleistocene - Middle Pleistocene	2.58 - 0.129	El Salvador	M. obtusidens (20152)
Pleistocene	2.58 - 0.0117	USA (Mississippi)	M. jeffersoni (161954) M. sp. (161194)
Pleistocene	2.58 - 0.0117	USA (South Carolina)	M. jeffersonii (65405)
Pleistocene	2.58 - 0.0117	USA (Tennessee)	M. jeffersonii (93373)
Pleistocene	2.58 - 0.0117	USA (West Virginia)	M. jeffersonii (108095)
Pleistocene	2.58 - 0.0117	USA (Florida)	M. jeffersoni (227368)
Pleistocene	2.58 - 0.0117	USA (New Jersey)	M. sp. (65469)
Pleistocene	2.58 - 0.0117	USA (Texas)	Megalonychidae indet. (207423) M. sp. (85140 207541)
Pleistocene	2.58 - 0.0117	USA (Illinois)	M. jeffersonii (87059)
Irvingtonian	1.4 - 0.21	USA (Pennsylvania)	M. wheatleyi (20479)
Irvingtonian	1.4 - 0.21	USA (Alabama)	M. jeffersonii (20281)
Irvingtonian	1.4 - 0.21	USA (South Carolina)	M. sp., M. jeffersonii (79919)
Irvingtonian	1.4 - 0.21	USA (Iowa)	M. jeffersonii (20556)
Irvingtonian	1.4 - 0.21	USA (California)	M. sp. (20125 20130 20155 20161 20272 20319 20327 20387) M. sp., M. wheatleyi (20128) M. wheatleyi (20187)
Irvingtonian	1.4 - 0.21	USA (South Dakota)	M. wheatleyi (20158)
Irvingtonian	1.4 - 0.21	Canada (Saskatchewan)	M. sp. (20563)
Irvingtonian	1.4 - 0.21	USA (Montana)	M. jeffersonii (20310)
Irvingtonian	1.4 - 0.21	USA (Florida)	M. leptostomus (20308) M. sp. (26550) M. wheatleyi (20299 20350 20415 20475)
Irvingtonian	1.4 - 0.21	USA (Oklahoma)	M. jeffersonii (20382)
Irvingtonian	1.4 - 0.21	USA (Maryland)	M. sp. (20302)
Irvingtonian	1.4 - 0.21	USA (Kansas)	M. leidyi (20353) M. sp. (20291 20301)
Irvingtonian - Rancholabrean	1.4 - 0.014	USA (California)	M. sp. (20323)
Middle Pleistocene	0.774 - 0.129	USA (California)	M. sp., Megalonychidae indet. (20639)
Middle Pleistocene	0.774 - 0.129	USA (Virginia)	M. jeffersonii (104662)
Middle Pleistocene	0.774 - 0.129	USA (Nebraska)	M. sp. (34382)
Middle Pleistocene	0.774 - 0.129	USA (South Carolina)	M. jeffersonii (79767 79768)
Rancholabrean	0.21 - 0.014	USA (Texas)	M. jeffersonii (225289)
Rancholabrean	0.21 - 0.014	USA (South Carolina)	M. jeffersonii (79757 79760)
Rancholabrean	0.21 - 0.014	USA (Florida)	M. sp. (20491)
Rancholabrean (glacial)	0.21 - 0.014	USA (California)	M. jeffersonii (20624)
Late/Upper Pleistocene	0.129 - 0.0117	USA (Georgia)	Megalonyx indet. (13066) M. sp. (84189)
Late/Upper Pleistocene	0.129 - 0.0117	USA (Texas)	M. jeffersonii (230753) M. sp. (85142)
Late/Upper Pleistocene	0.129 - 0.0117	USA (Florida)	M. jeffersonii, M. wheatleyi (74292) M. sp. (74294) M. wheatleyi (20638)
Late/Upper Pleistocene	0.129 - 0.0117	USA (California)	M. jeffersonii (236636) M. sp. (20273 73752 74235 93250 155409)
Late/Upper Pleistocene (high glacial)	0.129 - 0.0117	USA (Texas)	M. brachycephalus (93103)
Late/Upper Pleistocene	0.129 - 0.0117	USA (West Virginia)	M. sp., M. jeffersonii (93332)
Late/Upper Pleistocene (interglacial)	0.129 - 0.0117	USA (Idaho)	M. jeffersonii (20569 20612)
Late/Upper Pleistocene (late glacial)	0.129 - 0.0117	USA (North Dakota)	M. jeffersonii (93268)
Late/Upper Pleistocene (interglacial)	0.129 - 0.0117	Canada (Alberta)	M. sp. (20615)
Late/Upper Pleistocene	0.129 - 0.0117	USA (Virginia)	M. jeffersonii (103358 104678)
Late/Upper Pleistocene (interglacial)	0.129 - 0.0117	USA (Florida)	M. sp. (20573)
Late/Upper Pleistocene (glacial)	0.129 - 0.0117	USA (California)	M. jeffersonii (155393)
Late/Upper Pleistocene (interglacial)	0.129 - 0.0117	USA (California)	M. jeffersonii (20574) M. sp. (20585 20609)
Late/Upper Pleistocene	0.129 - 0.0117	USA (Illinois)	M. jeffersonii (93486)
Late/Upper Pleistocene (late glacial)	0.129 - 0.0117	USA (Utah)	M. jeffersonii (93266)
Late/Upper Pleistocene	0.129 - 0.0117	Guatemala (El Petén)	M. sp. (189383)
Late/Upper Pleistocene (interglacial)	0.129 - 0.0117	Canada (Yukon)	M. jeffersonii (20626)
Late/Upper Pleistocene	0.129 - 0.0117	Guatemala (Peten)	M. sp. (71312)
Late/Upper Pleistocene (late glacial)	0.129 - 0.0117	USA (Ohio)	M. jeffersonii (93208)
Late/Upper Pleistocene	0.129 - 0.0117	Honduras	M. sp. (190753)
Late/Upper Pleistocene (late glacial)	0.129 - 0.0117	USA (Illinois)	M. jeffersonii (93209)
Late/Upper Pleistocene	0.129 - 0.0117	USA (Arkansas)	M. jeffersoni (216259)
Late/Upper Pleistocene (late glacial)	0.129 - 0.0117	USA (Kansas)	M. jeffersonii (83073)
Late/Upper Pleistocene (interglacial)	0.129 - 0.0117	Canada (Northwest Territories)	M. jeffersonii (20610)
Late/Upper Pleistocene	0.129 - 0.0117	USA (South Carolina)	M. jeffersoni (152904)
Late/Upper Pleistocene	0.129 - 0.0117	USA (Missouri)	M. jeffersoni (93379)
Late/Upper Pleistocene (interglacial)	0.129 - 0.0117	USA (Alabama)	M. jeffersonii (20584)
Late/Upper Pleistocene - Holocene	0.129 - 0.0	USA (Missouri)	M. jeffersonii (63563)