Studies on the cupulate seed genus Hydrasperma Long from Berwickshire and East Lothian in Scotland and County Kerry in Ireland

Abstract

Twelve petrified cupules containing seeds of Hydrasperma tenuis Long from the Upper Devonian/Lower Carboniferous Transition Series from Ballyheigue, Kerry Head, Ireland have been studied. The cupules containing 2–6 seeds are borne in pairs. Each cupule is campanulate and composed of up to 24 oval to terete units. The axis of the cupule is forked, each resultant branch dividing in an alternate monopodial fashion producing six major axes. These divide repeatedly, each terminating in a narrow rounded tip. A reconstruction of a four-seeded cupule is presented. Hydrasperma longii sp. nov. is proposed for the first ‘named’ Scottish cupulate seeds named by Long as Hydrasperma cf. tenuis. Hydrasperma longii differs from H. tenuis: comparison of H. tenuis with other cupulate Lower Carboniferous seeds indicates that two major branching patterns of the cupule occur in early seed plants. Following an initial dichotomy, branching may either be entirely dichotomous, or alternately monopodial. The Aneurophytales appears to have the branching patterns consistent with its position as the ancestral group.