Giant beaver

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Giant beaver
Skeleton of Castoroides ohioensis

Skeleton of Castoroides ohioensis

Temporal occurrence
Gelasian to Young Pleistocene
2.1 million years to around 10,000 years
Locations
Systematics
Superordinate : Euarchontoglires
Order : Rodents (Rodentia)
Family : Beaver (Castoridae)
Subfamily : Castoroidinae
Tribe : Castoroidini
Genre : Giant beaver
Scientific name
Castoroides
Foster , 1838

The giant beavers ( Castoroides ) are a fossil genus of very large beavers that occurred in North America during the Pleistocene . Castoroides leiseyorum and its sister species C. ohioensis are the largest known beavers that have ever existed.

description

Illustration by Castoroides by Charles R. Knight from 1904

Giant beavers were similar to modern beavers, but as the name suggests, they were considerably larger. They reached lengths of over 2.50 m. This made them not only the largest rodents in North America during the last ice age, but also weighed around 60 to 100 kg, the weight of a recent black bear. Some estimates even assume 220 kg. Their hind feet were much larger than that of modern beavers. However, since the soft tissues have not survived in fossil form, it is not known whether webbed toes were present, as is the case with modern beavers. For the same reason it can only be assumed whether the tail resembled that of the modern beaver; In terms of skeletal anatomy, the tail of the giant beaver must have been longer, but narrower. The incisors were six inches long and had blunt, rounded tips. In contrast, the incisors of modern beavers have chisel-like tips. The molars were well adapted for grinding food and thus resembled those of capybaras , which have an S-shaped pattern on the grinding surfaces. Their large mass may have restricted their movement on land. As isotope studies have shown, the giant beavers did not primarily feed on twigs, bark and leaves like their more recent relatives, but on aquatic plants.

Systematics

Two species are known: The remains of Castoroides leiseyorum were discovered in Florida and South Carolina. Castoroides ohioensis bone finds are known from across the continental United States and Canada. Castoroides is not closely related to the modern beavers of the genus Castor . It is the type genus of the subfamily Castoroidinae , which also contains the fossil genera Monosaulax , Eucastor , Dipoides , Priusaulax and Procastoroides . Castor, on the other hand, belongs to the Castorinae subfamily. Both the Castorinae and the Castoridinae, however, form a monophyletic unit that summarizes the semi-aquatic beavers. Opposite them is a group of terrestrial or burrowing forms, which are divided into the subfamilies of the Palaeocastorinae and the Migmacastorinae . Molecular genetic studies, which also included the genome of the giant beaver, suggest that the lines of Castoroides and Castor were separated in the Lower Miocene . According to this, the semi-aquatic group of beavers has existed for at least around 19.7 million years.

Discovery story

A cast by C. ohioensis assembled from different specimens

The first giant beaver fossils were brought to light in a peat bog in Ohio in 1837, hence the species epithet ohioensis . Nothing is known about whether the giant beavers built buildings. In Ohio there are claims of a possible giant beaver castle that is said to be 122 cm high and 244 cm in diameter. It is said to have been built from small, young tree trunks. There is clear evidence that a beaver castle was built in the related genus Dipoides . This leads to the assumption that giant beavers could also have built such structures. Giant beaver fossils are concentrated in the American Midwest , particularly Illinois and Indiana . However, there is also evidence from Alaska, Canada and Florida. Specimens from Florida have been classified into a separate subspecies Castoroides ohioensis dilophidus based on differences in the molars and premolars. Castoroides leiseyorum fossils have been discovered in Florida and South Carolina . Mark D. Uhen, Ph.D. at George Mason University , dated the remains from the Cooper River site in South Carolina to an age of 1.8 million to 11,000 years. The specimens from the paleontological deposits Leisey Shell Pit 1A and 3B in Hillsborough County, Florida were determined in November 2007 by John Alroy to an age of 2.1 million years. Castoroides leiseyorum was described by Gary S. Morgan and John A. White in 1995 and named after the Leisey family, Hillsborough County phosphate quarry owners who discovered the first skull.

die out

Mounted skeleton

Fossils of the older species C. leiseyorum from Florida are 1.4 million years old, while fossils of the younger species C. ohioensis from Toronto, Ontario and the Old Crow Basin , Yukon are 130,000 years old. However, it is assumed that the giant beavers together with the mammoths, mastodons and ice age horses became extinct in the Quaternary wave of extinction at the end of the last ice age 10,000 years ago. Giant beavers were most common south of the Great Lakes in what is now Indiana and Illinois. The giant beaver's extinction could be due to the ecological changes at the end of the Pleistocene. The appearance of humans in North America could also have been a factor, however there is no evidence that the giant beavers were hunted by humans.

folklore

Both the Mi'kmaq tribe from Canada and the Pocumtuc tribe from the Connecticut River Valley in Massachusetts have myths about giant beavers. Such myths also exist among the Cree Indians.

Web links

Commons : Giant Beaver ( Castoroides )  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c Bjorn Kurten, Elaine Anderson: Pleistocene Mammals of North America. Columbia University Press, New York NY 1980, ISBN 0-231-03733-3 .
  2. ↑ a b c d e Giant Beaver: Natural History Notebooks . Canadian Museum of Nature. May 2, 2011. Retrieved October 18, 2013.
  3. ^ Canadian Museum of Nature , Notebooks: Giant Beaver
  4. ^ PS Reynolds: How Big Is a Giant? The Importance of Method in Estimating Body Size of Extinct Mammals. In: Journal of Mammalogy . Vol. 83, No. 2, May 2002, pp. 321-332, doi : 10.1644 / 1545-1542 (2002) 083 <0321: HBIAGT> 2.0.CO; 2 .
  5. ↑ a b C.R. Harrington: Yukon Beringia Interpretive Center - Giant Beaver . 1996. Archived from the original on September 14, 2007. Retrieved October 18, 2013.
  6. ↑ Tessa Plint et al. 2019. Giant beaver palaeoecology inferred from stable isotopes. Scientific Reports 9, article number: 7179, doi: 10.1038 / s41598-019-43710-9
  7. ^ William W. Korth: The Tertiary record of rodents in North America (= Topics in Geobiology. Vol. 12). Plenum Press, New York et al. 1994, ISBN 0-306-44696-0 , p. 145.
  8. ↑ Georgios Xenikoudakis, Mayeesha Ahmed, Jacob Colt Harris, Rachel Wadleigh, Johanna LA Paijmans, Stefanie Hartmann, Axel Barlow, Heather Lerner, Michael Hofreiter: Ancient DNA reveals twenty million years of aquatic life in beavers. Current Biology 30, 2020, pp. R110 – R111, doi: 10.1016 / j.cub.2019.12.041 .
  9. ^ Robert A. Martin: Taxonomy of the Giant Pleistocene Beaver Castoroides from Florida. In: Journal of Paleontology. Vol. 43, No. 4, July 1969, pp. 1033-1041.
  10. ↑ RC Hulbert Jr., GS Morgan: Stratigraphy, Paleoecology, and vertebrate fauna of the Leisey Shell Pit local fauna, early Pleistocene (Irvingtonian) of Southwestern Florida (= Papers in Florida Paleontology. No. 2, ISSN  1062-8614 ). University of Florida - Florida Museum of Natural History, Gainesville FL 1989.
  11. ^ John Alroy: Conjunction among taxonomic distributions and the Miocene mammalian biochronology of the Great Plains. In: Paleobiology. Vol. 18, No. 3, 1992, pp. 326-343, online (PDF; 2.79 MB) .
  12. ^ John Alroy: Speciation and extinction in the fossil record of North American mammals. In: Roger K. Butlin, Jon R. Bridle, Dolph Schluter (Eds.): Speciation and patterns of diversity. Cambridge University Press, Cambridge et al. 2009, ISBN 978-0-521-70963-7 , pp. 301-323, online (PDF; 182.5 kB) .
  13. ^ Gary S. Morgan, John A. White: Small mammals (Insectivora, Lagomorpha, and Rodentia) from the early Pleistocene (early Irvingtonian) Leisey Shell Pit Local Fauna, Hillsborough County, Florida. In: Bulletin of the Florida Museum of Natural History. Vol. 37, Part 2, No. 13, 1995, ISSN  0071-6154 , pp. 397-461, online .
  14. ↑ Paleobiology Database, Collection 20403 and 20400 . Location Leisey's Shell Pits 1A and 3B, Hillsborough County, Florida. Authorized and entered by John Alroy, on February 18, 1993 and Mark D. Uhen, Ph.D.
  15. ^ Paul W. Parmalee, Russell Wm. Graham: Additional records of the Giant Beaver, Castoroides, from the mid-South: Alabama, Tennessee, and South Carolina. In: Robert J. Emry (Ed.): Cenozoic Mammals of Land and Sea. Tributes to the career of Clayton E. Ray (= Smithsonian Contributions to Paleobiology. Vol. 93, ISSN  0081-0266 ). Smithsonian Institution Press, Washington DC 2002, pp. 65–71, online (PDF; 148.45 MB) .