The new trace fossil Gyrolithes lorcaensis isp. n. from the Miocene of SE Spain and a critical review of the Gyrolithes ichnospecies

The 18 ichnospecies of the vertically oriented, helical marine to marginal marine trace fossil Gyrolithes Saporta, 1884 known so far are revised. A new ichnospecies, G. lorcaensis isp. n. (Miocene, SE Spain), is introduced, and Conispiron Vialov, 1969 and Spirocircus Mikuláš and Pek, 1994 are included in Gyrolithes. The ichnotaxobases of the Gyrolithes ichnospecies are based on the character of the burrow margin (presence or absence of a wall or ornamentation) and/or on morphometric parameters (burrow width versus radius of the whorls). As a result of synonymization, 13 ichnospecies are recommended. The morphometric parameters of Gyrolithes show two distinct lineages (large ratio of whorl radius to burrow width and medium ratio of whorl radius to burrow width; 10–12 and 1–1.6, respectively). The third lineage (small ratio of whorl radius to burrow width; up to 1) is less distinct.