Early perisphinctid ammonites from the early/late Bajocian boundary interval (Middle Jurassic) from Lokut, Hungary

On the basis of an evaluation of data from the literature and a systematic study of rich material from the Stephanoceras humphriesionum and Strenoceras niortense Zones of the Bakony Mountains (Transdanubian Hungary), it is supported that leptosphinctids, the earliest Perisphinctidae s.str., most probably originated from Western Tethyan Stephanoceratidae. This descent is documented here with stephanoceratids very close to earliest leptosphinctids (Phaulostephanus exilis nov. sp. and Ph. apertus nov. sp.) and with very early leptosphinctids showing mixed stephanoceratid and perisphinctid characters. This latter group is represented by species described previously elsewhere plus new species (Stephanosphinctes tuberculatus nov. sp., a macroconch, and Leptosphinctes (Cleistosphinctes) umbilicatus nov. sp., a microconch). Possible migration routes of early perisphinctids are discussed and the Hispanic Corridor is suggested as the most probable. (C) 2012 Elsevier Masson SAS. All rights reserved.