Hidden subsurface garden on own faeces – the trace fossil Tubulichnium rectum (Fischer-Ooster, 1858) from the Cretaceous-Palaeogene deep-sea sediments

Tubulichnium rectum (Fischer-Ooster, 1858) is an oblique to horizontal, unbranched, blind ending tube having margins densely lined with ellipsoidal muddy pellets. It occurs in fine sandy to muddy, siliciclastic and marly deep-sea sediments mostly from Turonian to Eocene times. It was probably produced by “worm”-like organisms, which fed on organic-rich sediment deposited seasonally or episodically on the sea floor. The faecal pellets were stored in the deep parts of the burrow within the anoxic zone beyond the depth that other burrowers usually penetrate. During periods of food shortage, the pellets were utilized as a supplementary nutrition source. Such behaviour in constructing and using a cache is interpreted as an adaptation to increased competition for food in the deep sea after the Cenomanian.