Substrate is a poor ichnotaxobase: a new demonstration

Substrate is a poor ichnotaxobase, yet it has been widely used for distinguishing the clavate (club-shaped) borings commonly produced by bivalves. A chert nodule from the Upper Cretaceous of Morocco encloses the external mould of a clast of unknown composition (rock? wood?) which had been extensively bored, producing both small cylindrical and large clavate pits. Numerous small, short borings are referred to Oichnus isp. cf. O. simplex Bromley; Oichnus is otherwise commonly limited to shelly substrates. More significantly, the clavate borings may either be Gastrochaenolites turbinatus Kelly and Bromley, considered confined to rock and shelly substrates, or be Teredolites clavatus Leymerie, thought to be limited to wood. These borings are morphologically indistinguishable, only being differentiated by substrate, and thus, they are considered to be synonymous herein. Gastrochaenolites clavatus (Leymerie) has priority and is the type species of Teredolites Leymerie, now considered a junior synonym of Gastrochaenolites Leymerie. Thus, the clavate borings of this specimen are identified as Gastrochaenolites clavatus (Leymerie).