''Lagrivea'' is a fossil

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

squirrel Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels (including chipmunks and prairie dogs, among others), and flying squirrels. Squ ...

from the

Middle Miocene The Middle Miocene is a sub-epoch of the Miocene Epoch made up of two stages: the Langhian and Serravallian stages. The Middle Miocene is preceded by the Early Miocene. The sub-epoch lasted from 15.97 ± 0.05 Ma to 11.608 ± 0.005 Ma (million y ...

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

. The single species, ''L. vireti'', is known from three

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

s (lower jaws) and two isolated teeth. All come from the fissure filling (a fossil deposit formed when a rock fissure filled with sediment) of La Grive L5, part of the La Grive-Saint-Alban complex in

Saint-Alban-de-Roche Saint-Alban-de-Roche () is a Communes of France, commune in the Isère departments of France, department in southeastern France. Population See also *Communes of the Isère department References

Communes of Isère Isère communes ...

, southeastern France. ''Lagrivea'' was a large

tree squirrel Tree squirrels are the members of the squirrel Family (biology), family (Sciuridae) commonly just referred to as "squirrels." They include more than 100 arboreal species native to all continents except Antarctica and Oceania. They do not form a ...

with flat lower

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, whe ...

s and a large, triangular fourth lower

premolar The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...

(p4). Each of the four cheekteeth (p4 and three molars, m1 through m3) bears a deep basin in the middle of the crown. The m3 is about rectangular in shape, but rounded at the back. Although m1 and m2 have two roots, m3 has three.

Taxonomy

Pierre Mein Pierre is a masculine given name. It is a French form of the name Peter. Pierre originally meant "rock" or "stone" in French (derived from the Greek word πέτρος (''petros'') meaning "stone, rock", via Latin "petra"). It is a translation ...

and Léonard Ginsburg described ''Lagrivea vireti'' in 2002 in a review of the ages and faunas of the Miocene fossil sites of La Grive-Saint-Alban in southeastern France.Mein and Ginsburg, 2002, p. 29 They suggested that it was probably a

and related to the

Sciurini Sciurini is a tribe (taxonomy), tribe that includes about forty species of squirrels,Thorington and Hoffmann, 2005, p. 754 mostly from the Americas. It includes five living genera—the American dwarf squirrels, ''Microsciurus''; the Bornean ...

.Mein and Ginsburg, 2002, p. 30 ''Lagrivea'' belongs to the squirrel family (Sciuridae), which first appears in the

Late Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...

of North America and

Early Oligocene The Rupelian is, in the geologic timescale, the older of two ages or the lower of two stages of the Oligocene Epoch/Series. It spans the time between . It is preceded by the Priabonian Stage (part of the Eocene) and is followed by the Chatti ...

of Europe. The specific name, ''vireti'', honors Jean Viret for his work on the mammals of La Grive-Saint-Alban.

Description

''Lagrivea'' is known from three mandibles (lower jaws)—one, the

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, with the fourth premolar (p4) and all three molars (m1–3) preserved; one with the incisor and m2; and one with the incisor, p4, m1, and m2—an isolated lower incisor, and an isolated m2. It was large for a squirrel, and can be distinguished from the fossil squirrels '' Palaeosciurus'', '' Aliveria'', and '' Ratufa obtusidens'' by its larger size. In the mandible, the

diastema A diastema (plural diastemata, from Greek διάστημα, space) is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition ...

(gap) between the incisors and the cheekteeth (premolars and molars) is relatively deep. The

mental foramen The mental foramen is one of two foramina (openings) located on the anterior surface of the mandible. It is part of the mandibular canal. It transmits the terminal branches of the inferior alveolar nerve and the mental vessels. Structure The m ...

(an opening in the bone) is located relatively high and before the p4. The upper and lower masseteric ridges, which are located on the outer side of the jaw and anchor some of the chewing muscles, meet at the m1. The surfaces of the incisor are very flat, but there are small, irregular striations in the enamel along the length of the tooth. The cheekteeth increase regularly in size from front to back. They all consist of a large central basin surrounded by

cusp A cusp is the most pointed end of a curve. It often refers to cusp (anatomy), a pointed structure on a tooth. Cusp or CUSP may also refer to: Mathematics * Cusp (singularity), a singular point of a curve * Cusp catastrophe, a branch of bifurca ...

s and crests. The basins are deeper than in ''Palaeosciurus'' and ''Ratufa obtusidens'' and lack crenulations in the enamel, which distinguishes them from another fossil squirrel, '' Albanensia''. The first cheekteeth, p4, is large and about triangular in form, short and quite broad at the back. The two cusps at the front, the

protoconid Many different terms have been proposed for features of the tooth crown in mammals. The structures within the molars receive different names according to their position and morphology. This nomenclature was developed by Henry Fairfield Osborn i ...

and

metaconid Many different terms have been proposed for features of the tooth crown in mammals. The structures within the molars receive different names according to their position and morphology. This nomenclature was developed by Henry Fairfield Osborn ...

, are isolated from each other. In front of the metaconid, there is a small cuspule, an anteroconid, at the lingual side of the tooth (the side of the tongue). The central basin of the tooth is relatively deep. At the back of the tooth, the

entoconid Many different terms have been proposed for features of the tooth crown in mammals. The structures within the molars receive different names according to their position and morphology. This nomenclature was developed by Henry Fairfield Osborn i ...

cusp is connected to the posterolophid, a crest that forms the back margin. Of the two roots, the one at the front is round and the one at the back is broad. Although m1 is nearly rectangular, the width at the front is still smaller than the width at the back. There is a strong anteroconid. A crest, the metalophid, reaches from the protoconid nearly to the metaconid. A small cusp, the mesostylid, is connected to the metaconid in front of it, unlike in '' Miopetaurista'' and ''Aliveria''. There are two broad roots. The next tooth, m2, is similar to m1 in most respects, but the width at the front is virtually equal to the width at the back, so that the tooth is about rectangular. The back of m3 is rounded, but the tooth is still nearly rectangular. There is a long anteroconid, which is mainly connected to the metaconid. There is no metalophid. This tooth has three roots: two at the front and a larger one at the back.

Range and context

The remains of ''Lagrivea'' were probably collected by Viret at the site La Grive L5 in the village of Saint-Alban-de-Roche, department of

Isère Isère ( , ; frp, Isera; oc, Isèra, ) is a landlocked department in the southeastern French region of Auvergne-Rhône-Alpes. Named after the river Isère, it had a population of 1,271,166 in 2019.MN zone MN 7/8, about 13 to 11 million years ago. La Grive L5 is one of the younger sites of La Grive, and Mein and Ginsburg proposed placing it in a separate zone MN 8.Mein and Ginsburg, 2002, p. 37 Other squirrels at La Grive-Saint-Alban include species of '' Heteroxerus'', '' Spermophilinus'', ''Palaeosciurus'', and

chipmunk Chipmunks are small, striped rodents of the family Sciuridae. Chipmunks are found in North America, with the exception of the Siberian chipmunk which is found primarily in Asia. Taxonomy and systematics Chipmunks may be classified either as ...

s, and

flying squirrel Flying squirrels (scientifically known as Pteromyini or Petauristini) are a tribe of 50 species of squirrels in the family Sciuridae. Despite their name, they are not in fact capable of full flight in the same way as birds or bats, but they ar ...

s in the genera ''Albanensia'', ''Miopetaurista'', ''

Forsythia ''Forsythia'' , is a genus of flowering plants in the olive family Oleaceae. There are about 11 species, mostly native to eastern Asia, but one native to southeastern Europe. ''Forsythia'' – also one of the plant's common names – is ...

'', ''

Hylopetes ''Hylopetes'' is a genus of flying squirrels. There are about 10 species. Species include: * Particolored flying squirrel - ''H. alboniger'' (Hodgson, 1836) * Bartel's flying squirrel - ''H. bartelsi'' Chasen, 1939 * Hainan flying squirrel - '' ...

'', and '' Blackia''.Mein and Ginsburg, 2002, p. 35 ''Miopetaurista neogrivensis'', ''Spermophilinus bredai'', and ''Heteroxerus huerzeleri'' are also known from La Grive L5. In 2012, Ginsburg and Mein described an indeterminate squirrel from the older (MN 6) site of Sansan, France, on the basis of a single p4. This tooth is similar in size to ''Lagrivea'', but differs in a narrower talonid.Ginsburg and Mein, 2012, p. 93

References

Literature cited

*Ginsburg, L. and Mein, P. 2012. Les Sciuridae (Rodentia) de Sansan. Mémoires du Muséum national d'Histoire naturelle 203:81–94. *McKenna, M.C. and Bell, S.K. 1997. Classification of Mammals: Above the species level. New York: Columbia University Press, 631 pp. *Mein, P. and Ginsburg, L. 2002. Sur l'âge relatif des différents karstiques miocènes de La Grive-Saint-Alban (Isère). Cahiers scientifiques, Muséum d'Histoire naturelle, Lyon 2:7–47 (in French). *Steininger, F. 1999. Chronostratigraphy, geochronology and biochronology of the Miocene "European Land Mammal Mega-Zones (ELMMZ)" and the Miocene "Mammal Zones (MN-Zones)". Pp. 9–24 in Rössner, G.E. and Heissig, K. (eds.). The Miocene Land Mammals of Europe. Munich: Verlag Dr. Friedrich Pfeil, 515 pp. {{Good article Miocene rodents Prehistoric mammals of Europe Squirrels Prehistoric rodent genera Fossil taxa described in 2002