Melanopsis from the Mid-Pleistocene site of Gesher Benot Ya’aqov (Gastropoda: Cerithioidea)

Submitted by admin on Sun, 20/11/2011 18:54
J. HELLER
N. SIVAN
(2001)
Volume
37
Part
2
Page from
127

Gesher Benot Ya’aqov is a 780,000 yr. old mid-Pleistocene site in the Hula Valley (Israel). Its rich Melanopsis fauna was found to include seven species: buccinoidea Olivier, costata Olivier (with two ill-defined forms, shouldered and conic), obediensis Picard, corrugata Schütt, vincta Blanckenhorn, sigmocorrugata n. sp. and turriformis Picard (with three ill-defined forms, ‘typical’, ‘ivory’ and 'gray-orange’).

Within the Jordan Valley, the Melanopsis faunal assemblage of Gesher Benot Ya’aqov is broadly similar to that of ‘Ubeidya. Beyond the Jordan Valley three species of Gesher Benot Ya’agov occur also in Plio-Pleistocene sites of the Orontes, thereby weakening arguments that the fauna of the Jordan evolved independently of the Orontes catchment area.

Most shells at Gesher Benot Ya’aqoo fall into clearly distinct species. However, intermediates are found between vincta and corrugata and between buccinoidea and turriformis. The occasional occurrence of the buccinoidea-turriformis intermediates within the layers of Gesher Benot Ya’aqov suggests that they are hybrids (rather than representatives of gradual evolutionary transition). Similarly among Recent Melanopsis, smooth-shelled buccinoidea and costate-shelled costata almost always remain distinct, but in zones of contact hybrids with intermediate shells may be found, at low frequencies and over short distances.

Keywords
Melanopsis
Pleistocene
Gesher Benot Ya’aqov
Systematics
Jordan Valley
hybrids