Transition-hybridization areas in parapatric species of Vipera aspis group from northern Italy

There is evidence of some contact between the parapatric species of Vipera aspis, Italian V. aspis and Vipera atra Meisner, 1820 along a North-South oriented sector, from about 8°45' to 9° 20' Longitude East. V. atra from north-western Italy is characterized by a high number of ventral scales and dorsal bars, and by a distinct morphological pattern of the hemipenes that has elongated lobes, mostly covered by short and small spines, while V. aspis has a relatively lower number of ventral scales and dorsal bars, and hemipenes that show large lobes with the upper part completely covered by a calyculate area. The intermediate specimens appear to be more similar to V.aspis than to V. atra