Fadeeva T.V., Kruskop S.V. 2009. Rudimentary small upper premolars in the Northern bat, Eptesicus nilssoni (Vespertilionidae, Chiroptera) // Russian J. Theriol. Vol.7 (for 2008). No.2: 77–80 [in English].

Tatyana V. Fadeeva [fadeeva.tatyana@mail.ru], Institute of Plant and Animal Ecology of RAS Ural Branch, ul. 8th of March 202, Ekaterinburg 620144, Russia;

Sergei V. Kruskop [kruskop@zmmu.msu.ru], Zoological Museum, Moscow State University, ul. Bolshaya Nikitskaya 6, Moscow 125009, Russia.

KEY WORDS: Eptesicus, northern bat, tooth formula, small premolar, cave deposits.

ABSTRACT. A case of presence of the upper small premolar in the genus Eptesicus is being described. Members of this genus were thought to be invariable in having no small premolars in upper toothrows. However, nine partial skulls of northern bats with traces of upper small premolars were excavated from cave deposits of Perm’ Territory. One additional specimen with abnormal dental formula was found in the collection of the Zoological Moscow of Moscow University. The presence of the small premolars in at least some individuals represents a primitive trait which puts E. nilssoni apart from the more advanced members of its genus.

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