''Mikrotia'' is an extinct

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

belonging to the

Muridae The Muridae, or murids, are the largest family of rodents and of mammals, containing approximately 1,383 species, including many species of mice, rats, and gerbils found naturally throughout Eurasia, Africa, and Australia. The name Muridae come ...

. It lived during the

upper Miocene The Late Miocene (also known as Upper Miocene) is a sub-epoch of the Miocene Epoch made up of two stages. The Tortonian and Messinian stages comprise the Late Miocene sub-epoch, which lasted from 11.63 Ma (million years ago) to 5.333 Ma. The ev ...

(about 11.63 - 5 million years ago) and its fossil remains have been found in

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...

(

Gargano Gargano (, Gargano Apulian Italo-Romance arˈgæːnə is a historical and geographical sub-region in the province of Foggia, Apulia, southeast Italy, consisting of a wide isolated mountain massif made of highland and several peaks and forming ...

). The type species is ''M. magna'', although two other species (''M. maiuscula'' and ''M. parka'') are also known.M. Freudenthal. (1976). Rodent stratigraphy of some Miocene fissure fillings in Gargano (prov. Foggia, Italy). ''Scripta Geologica'' 37:1-23M. Freudenthal. (2006). ''Mikrotia'', ''nomen novum'' for ''Microtia'' Freudenthal 1976 (Mammalia, Rodentia). ''Journal of Vertebrate Paleontology'' 26(3):784 Garganoaetus freudenthali

Description

This animal, despite belonging to the Muridae, was much larger in size than its modern equivalents. The only known skull of the largest species, ''Mikrotia magna'', was about long. The three known species of the genus ''Mikrotia'' show an evolutionary tendency towards the development of hypsodontal molars (with a high crown) and in the increase of the number of dental lobes in the first lower molar (as happened later to modern

vole Voles are small rodents that are relatives of lemmings and hamsters, but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of low-c ...

s). The oldest specimens of the genus were still characterized by a dental pattern typical of murids, consisting of a succession of three parallel rows of cusps. However, an additional lobe was already present in the anterior part of the lower first molar. In a rather rapid evolutionary succession, various successive species of Mikrotia developed more and more additional lobes and increased hypsodontia. In the last and largest species, ''M. magna'', the first lower molar had acquired a pattern totally similar to that of voles, with six rows of transverse ridges.

Classification

''Mikrotia'' is represented by three species (''M. parva'', ''M. maiuscula'' and ''M. magna''), all found in the fissure deposits of Gargano. During the Miocene Gargano became an island and developed insular fauna, including large rodents. ''Mikrotia'' developed from unknown continental forms (perhaps '' Parapodemus'', with which the older species of ''Mikrotia'' share the shape of the lower molars) and later its size increased, as did dental specializations. Freudenthal initially described these species in the genus ''Microtia'' in 1976 (with reference to ''

Microtus ''Microtus'' is a genus of voles found in North America, Europe and northern Asia. The genus name refers to the small ears of these animals. About 62 species are placed in the genus. They are stout rodents with short ears, legs and tails. They ea ...

'', a vole with similar teeth), but later the same scholar renamed the genus to ''Mikrotia'' in 2006, since the name ''

Microtia Microtia is a congenital deformity where the auricle (external ear) is underdeveloped. A completely undeveloped pinna is referred to as anotia. Because microtia and anotia have the same origin, it can be referred to as microtia-anotia. Microtia ...

'' was already preoccupied by a butterfly genus named in 1864. ''Mikrotia'', despite the affinities of the dentition with those of the arvicolines, belongs to the Muridae on the basis of cranial characteristics.Parra, V., Jaeger, J.-J. & Bocherens, H. (1999/06/15): The skull of ''Microtia'', an extinct burrowing murine rodent of the late Neogene Gargano palaeoisland. ''Lethaia'', Vol. 32, Oslo. ISSN 0024-1164.

References

{{Taxonbar, from=Q20721927 Prehistoric murids Prehistoric rodent genera Fossil taxa described in 2006 Old World rats and mice