The trace fossil Ctenopholeus Seilacher & Hemleben, 1966 from the Jurassic of India and Iran: distinction from related ichnogenera

The relationship between the ichnogenera Saerichnites BILLINGS, 1886, Hormosiroidea SCHAFFER, 1928, and Ctenopholeus SEILACHER & HEMLEBEN, 1966 is discussed. Straight, curved to looped uniserial rows of closely spaced circular to subcircular pits or knobs (negative or positive epireliefs) have been accommodated in the ichnotaxon Ctenopholeus kutcheri SEILACHER & HEMLEBEN, 1966. They were found on a bedding plane with oscillation ripples in Upper Jurassic rocks of the Jaisalmer Basin, Rajasthan, and on flat surfaces with parting lineation in lower Jurassic sandstones of the Shemshak Formation of the eastern Alborz, Iran. In both cases, a shallow-water, high-energy environment is indicated. Evidence of a horizontal burrow situated below and connected to these pits/knobs confirms the interpretation of a three-dimensional burrow system consisting of a horizontal tunnel from which at close distance vertical shafts extended to the sediment water interface. In contrast to earlier interpretations of the burrow system as fodinichnion, it is here interpreted as an agrichnion, functioning as trap for small mobile organisms.