Leptosphinctes

Leptosphinctes is an ammonite genus from the middle Jurassic with a fairly wide spread distribution, and is the type genus for the Leptosphinctinae.

Two subgenera have been described, Leptosphinctes (Leptosphinctes) and Leptosphinctes (Cleistosphinctes). Both are strongly evolute with all whorls showing. The early whorls of the macroconch of L (Leptosphinctes), which reaches a diameter of 13.5cm, have close spaced ribs covering the sides. The final,external whorl has strong ribs on the lower, inner flanks. The shell itself is moderately narrow, the venter narrowly rounded. In contrast the smaller microconch of L (Cleistosphinctes) cleistus has close spaced ribs on the outer whorl that slope forward dorso-ventrally and large lappets that extent from either side of the aperture. Diameter, some 4.5cm (~1.8 in) e.g.