Josephoartigasia spp.

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Josephoartigasia spp.


Illustration of two fighting J. monesi. © @ Raúl Martín.

Temporal range: Pliocene-Early Pleistocene

Scientific classification:

Life
Clade: Neomura
Domain: Eukarya
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
Clade: Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Subphylum: Cephalochordata
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Clade/Order: Therapsida
Clade: Neotherapsida
Clade: Theriodontia
Clade: Eutheriodontia
Clade/Suborder: Cynodontia
Clade: Epicyonodontia
Infraorder: Eucynodontia
Clade: Probainognathia
Superfamily: Chiniquodontoidea
Clade: Prozostrodontia
Clade: Mammaliformes
Class: Mammalia
Subclass: Theria
Infraclass: Placentalia
Subcohort: Exafroplacentalia
Magnorder: Boreoeutheria
Superorder: Euarchontoglires
(unranked): Glires
Order: Rodentia
Suborder: Hystricomorpha
Infraorder: Hystricognathi
Parvorder: Caviomorpha
Superfamily: Chinchilloidea
Family: Dinomyidae
Genus: †Josephoartigasia
Species: †Josephoartigasia monesi
†Josephoartigasia magnus

The largest fossil rodent
Andrés Rinderknecht & R. Ernesto Blanco

Abstract

"The discovery of an exceptionally well-preserved skull permits the description of the new South American fossil species of the rodent, Josephoartigasia monesi sp. nov. (family: Dinomyidae; Rodentia: Hystricognathi: Caviomorpha). This species with estimated body mass of nearly 1000 kg is the largest yet recorded. The skull sheds new light on the anatomy of the extinct giant rodents of the Dinomyidae, which are known mostly from isolated teeth and incomplete mandible remains. The fossil derives from San José Formation, Uruguay, usually assigned to the Pliocene–Pleistocene (4–2 Myr ago), and the proposed palaeoenvironment where this rodent lived was characterized as an estuarine or deltaic system with forest communities."

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Predicting bite force and cranial biomechanics in the largest fossil rodent using finite element analysis

"Josephoartigasia monesi, from the Pliocene of Uruguay, is the largest known fossil rodent, with an estimated body mass of 1000 kg. In this study, finite element analysis was used to estimate the maximum bite force that J. monesi could generate at the incisors and the cheek teeth. Owing to uncertainty in the model inputs, a sensitivity study was conducted in which the muscle forces and orientations were sequentially altered. This enabled conclusions to be drawn on the function of some of the masticatory muscles. It was found that J. monesi had a bite of 1389 N at the incisors, rising to 4165 N at the third molar. Varying muscle forces by 20% and orientations by 10° around the medio-lateral aspect led to an error in bite force of under 35% at each tooth. Predicted stresses across the skull were only minimally affected by changes to muscle forces and orientations, but revealed a reasonable safety factor in the strength of the skull. These results, combined with previous work, lead us to speculate that J. monesi was behaving in an elephant-like manner, using its incisors like tusks, and processing tough vegetation with large bite forces at the cheek teeth."

onlinelibrary.wiley.com/doi/10.1111/joa.12282/abstract

Here's an article by Brian Switek on this.

phenomena.nationalgeographic.com/2015/02/04/giant-fossil-rodent-had-an-awesome-bite/

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New size estimate for Josephoartigasia and other giant fossil rodents using occipital condyle width, which was recently shown to be a strong predictor of body mass in mammals. Turns out it...probably wasn't as big as we thought it was.

Resizing the largest known extinct rodents (Caviomorpha: Dinomyidae, Neoepiblemidae) using occipital condyle width

Several extinct chinchilloid rodents in the clades Dinomyidae and Neoepiblemidae grew to sizes much larger than any living rodent species. However, the exact size of these rodents is a matter of controversy, with authors disagreeing due to issues over extrapolation and model selection. Prior estimates for the two largest extinct rodents, Phoberomys pattersoni and Josephoartigasia monesi, range from 230 to 700 kg for P. pattersoni and 350 to 2600 kg for J. monesi. Here, I estimate body mass in large, extinct rodents using occipital condyle width (OCW), a strong predictor of body size in mammals, using a dataset that circumvents many of the issues faced by previous studies of species. Body masses under shape-corrected OCW are much lower than previous studies: 108–200 kg for P. pattersoni and 480 kg for J. monesi. Mass estimates for other rodent taxa (Neoepiblema, Telicomys, Dinomys) agree with previous studies. Estimates using skull length, corrected condyle width and head-body length are similar, suggesting estimates of 150 kg for Phoberomys and 480 kg for Josephoartigasia, and that larger estimates of 700 and 1200 kg are unlikely. High estimates in previous studies appear to be due to the unrecognized, nonlinear relationship between certain skeletal measurements (skull size) and body mass.

royalsocietypublishing.org/doi/10.1098/rsos.220370


Also, it looks like this profile could use some serious overhauling.