THE ICHNOGENUS BEACONITES AND ITS DISTINCTION FROM ANCORICHNUS AND TAENIDIUM

Beaconites is a trace-fossil name that has been adopted indiscriminant ly for unlined, lined, unwalled, thinly walled, and thickly walled, me niscate backfilled burrows. The confusion is further exacerbated by th e inconsistent use of the terms 'wall' and 'lining'. A wall and a lini ng (a type of wall) are herein restricted to features actively constru cted by the burrower, and are considered distinct from peripheral feat ures produced by simple excavation or during locomotion. Differences i n the type of meniscate backfilling are also recognized, and may assis t in the distinction of ichnotaxa. Beaconites, and likewise the type i chnospecies B. antarcitus, is a lined (walled) meniscate trace fossil; B. barretti, the ichnospecies most popularly assigned to the ichnotax on, is actually unlined and unwalled, and cannot therefore be included within Beaconites. Recent emendments to Taenidium describe it essenti ally as unlined meniscate backfilled burrow. The diagnosis of Taenidiu m is, however, further emended to clarify that it is an unwalled struc ture. Forms previously assigned to B. barretti can therefore be includ ed within Taenidium as T. barretti. Emendments to the original diagnos is of Ancorichnus describe this trace fossil as a walled ichnotaxon. T hese emendments are rejected because this world place the ichnogenus i n junior synonymy with Beaconites; instead, the original diagnosis of Ancorichnus is re-established. Two ichnospecies, A. capronus and A. co ronus are, nevertheless, considered to be separate ichnospecies of Bea conites, namely B. capronus and B. coronus. The type ichnospecies, A. ancorichnus, is distinguished by a structured mantle peripheral to a m eniscate core. The mantle is not considered as a wall structure since it is formed by the locomotive behaviour of the burrow producer.