“Megatheriidae”的意思、由来-开放百科全书

Megatheriids appeared during the Late Oligocene (Deseadan in the SALMA classification), some 23 million years ago, in South America. The group includes the heavily built Megatherium (given its name 'great beast' by Georges Cuvier^[2]) and Eremotherium. An early megatheriid, the more slightly built Hapalops, reached a length of about {{convert|1.2|m|ft}}. The nothrotheres have recently been placed in their own family, Nothrotheriidae.^[3]

The skeletal structure of these ground sloths indicates that the animals were massive. Their thick bones and even thicker joints (especially those on the hind legs) gave their appendages tremendous power that, combined with their size and fearsome claws, provided a formidable defense against predators.

The earliest megatheriid in North America was Eremotherium eomigrans which arrived 2.2 million years ago, after crossing the recently formed Panamanian land bridge. At more than five tons in weight, 6 meters in length, and able to reach as high as {{convert|17|ft|m}}, it was taller than an African bush elephant bull. Unlike relatives, this species retained a plesiomorphic extra claw. While other species of Eremotherium had four fingers with only two or three claws, E. eomigrans had five fingers, four of them with claws up to nearly a foot long.^[4]

Classification

Subfamily †Megatheriinae
- Tribe †Megatheriini
- Subtribe †Prepotheriina
- Genus †Proprepotherium
- Genus †Planops
- Genus †Prepotherium
- Subtribe †Megatheriina
- Genus †Megathericulus
- Genus †Promegatherium
- Genus †Plesiomegatherium
- Genus †Megatheridium
- Genus †Pyramiodontherium
- Genus †Megatherium
- Genus †Eremotherium
- Genus †Ocnopus
- Genus †Perezfontanatherium
?Subfamily †Schismotheriinae^[5]
- Genus †Hapaloides
- Genus †Schismotherium
- Genus †Hapalops
- Genus †Pelecyodon
- Genus †Parapelecyodon
- Genus †Analcimorphus
- Genus †Hyperleptus
- Genus †Neohapalops
?Subfamily †Thalassocninae^[6]
- Genus †Thalassocnus

References

1. ^Paleobiology Database: Megatheriidae
2. ^G. Cuvier (1796)
3. ^{{cite journal | last = Muizon | first = C. de | authorlink = |author2=McDonald, H. G. |author3=Salas, R. |author4=Urbina, M. | title = The Youngest Species of the Aquatic Sloth Thalassocnus and a Reassessment of the Relationships of the Nothrothere Sloths (Mammalia: Xenarthra) | journal = Journal of Vertebrate Paleontology | volume = 24 | issue = 2 | pages = 387–397 | publisher = Society of Vertebrate Paleontology | location = |date=June 2004 | url = http://www.bioone.org/doi/abs/10.1671/2429a | doi = 10.1671/2429a | id = | accessdate = 2009-01-29}}
4. ^De Iuliis and Cartelle (1999)
5. ^However, a phylogenetic study conducted by Amson, de Muizon & Gaudin (2017) indicates that at least the genera Schismotherium, Pelecyodon, Analcimorphus and Hapaloides do not belong to the family Megatheriidae, or even to the group Megatheria (containing the families Megatheriidae and Nothrotheriidae). See: {{cite journal |author1=Eli Amson |author2=Christian de Muizon |author3=Timothy J. Gaudin |year=2017 |title=A reappraisal of the phylogeny of the Megatheria (Mammalia: Tardigrada), with an emphasis on the relationships of the Thalassocninae, the marine sloths |journal=Zoological Journal of the Linnean Society |volume=179 |issue=1 |pages=217–236 |doi=10.1111/zoj.12450 |url=http://hal.upmc.fr/hal-01331193/file/Amson_2016_A_reappraisal_of.pdf }}
6. ^{{cite journal |author1=Eli Amson |author2=Christian de Muizon |author3=Timothy J. Gaudin |year=2017 |title=A reappraisal of the phylogeny of the Megatheria (Mammalia: Tardigrada), with an emphasis on the relationships of the Thalassocninae, the marine sloths |journal=Zoological Journal of the Linnean Society |volume=179 |issue=1 |pages=217–236 |doi=10.1111/zoj.12450 |url=http://hal.upmc.fr/hal-01331193/file/Amson_2016_A_reappraisal_of.pdf }}

Classification

References

External links