The new complex helical trace fossil Avetoichnus luisae igen. n. et isp. n. from the Cainozoic deep-sea sediments of the Alpine realm: a non-graphoglyptid mid-tier agrichnion

A new mid-tier, minute complex trace fossil Avetoichnus luisae igen. n. et isp. n., composed of a horizontal or subhorizontal helical spiral with a simple, straight or slightly curved central core, all developed and interconnected on a few levels, is proposed on the basis of material from Cainozoic deep-sea sediments from the Northern Apennines (Italy) and the Carpathians (Poland). Additional data on its occurrence come from northern Spain (W Pyrenees) and northern Turkey (Sinop Basin in the Pontian system). Avetoichnus is probably produced by polychaetes, less probably by enteropneusts, and is interpreted as a non-graphoglyptid middle tier complex agrichnion, in which microbes were cultivated on organic-rich sediment packed in a horizontal spiral, available from a central tunnel running inside the spiral. Such a behavioural invention was a response to high competition for food the deep sea during the Paleogene.