Josephoartigasia
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| Temporal occurrence | ||||||||||||
| Pliocene to Pleistocene | ||||||||||||
| 4 to 2 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Josephoartigasia | ||||||||||||
| Mones , 2007 |
Josephoartigasia monesi is an extinct rodent and belongs to the family of Dinomyidae ("terrible mice"), which includes the Pakarana , which is still alive today. It is the largest known rodent. Fossils of Josephoartigasia monesi have been found in South American layers, which are assigned to the Pliocene and possibly the Pleistocene . The specific epithet “ monesi ” was chosen in honor of the Uruguayan paleontologist Álvaro Mones .
Locations
Fossils of Josephoartigasia monesi were found in 4 to 2 million year old layers of the San José Formation on the banks of the Río de la Plata in Uruguay . It is believed that the Dinomyidae family first spread to southern South America 20 million years ago. The species Josephoartigasia monesi is the youngest member of the family.
properties
A skull 53 centimeters long was found in the San José formation with unusually small molars in the jaws . The attachments of the masticatory muscles, which are responsible for the grinding movements of the lower jaw, are said to have been unusually weak for rodents . From this, the paleontologists Ernesto Blanco and Andrés Rinderknecht conclude that Josephoartigasia monesi probably lived on soft plants and fruits. This would support the theory that the rodent lived in river deltas with abundant vegetation.
However, a later examination revealed a bite force three times stronger than originally assumed. It is said to have corresponded to that of a tiger. Like the elephants their tusks, Josephoartigasia monesi could probably also use its incisors for digging and defense.
Estimates of the weight assume 1,211 kilograms. However, these calculations have a large uncertainty range of 753 kilograms more or less. With this weight, Josephoartigasia monesi would be twice as heavy as the Phoberomys pattersoni, previously known as the largest rodent, and 16 times heavier than the South American capybara, which weighs up to 60 kilograms. According to calculations, because of its huge body, the animal was probably occupied with feeding all day in order to be able to keep its body temperature constant.
classification
Josephoartigasia monesi are assigned to rodents (Rodentia) on the basis of the skull features, such as the weakly pronounced zygomatic process of the frontal bone , the jawbone designed for the strength of the chewing apparatus, the eye socket that is open to the rear and the toothless gap (diastema) between the molars and incisors . The incisor teeth of the species were about 30 centimeters long.
literature
- Andres Rinderknecht, R. Ernesto Blanco: The largest fossil rodent. In: Proceedings of the Royal Society. B Vol. 275, No. 1637, April 2008, ISSN 0080-4649 , pp. 923-928, doi : 10.1098 / rspb.2007.1645 .
Web links
- Spektrumdirekt article on Josephoartigasia monesi
- In English: Summary of the find
- A very big brother for rats, capybaras and co
Individual evidence
- ^ Andrés Rinderknecht, R. Ernesto Blanco: The largest fossil rodent . January 15, 2008, doi : 10.1098 / rspb.2007.1645 ( online PDF [accessed January 17, 2007]).
- ^ Philip G. Cox, Andrés Rinderknecht, R. Ernesto Blanco. Predicting bite force and cranial biomechanics in the largest fossil rodent using finite element analysis. Journal of Anatomy, 2015; DOI: 10.1111 / joa.12282