The trace fossilPolykampton recurvumn. isp. (sequestrichnia) from the Maastrichtian–Paleocene deep-sea deposits of NW Italy

Alfred Uchman,Bruno Rattazzi

doi:10.1017/jpa.2021.67

Abstract

AbstractPolykampton recurvumn. isp. is the sixth ichnospecies of the ichnogenusPolykamptonOoster, 1869. It is a horizontal structure composed of a median cylindrical tunnel and narrow, usually back-curved lateral lobes located in alternating position. It occurs 2–3 cm below the top of single beds in the Maastrichtian–Paleocene deep-sea turbiditic marlstones of the Monte Antola Unit in the Northern Apennines. The lobes ofP. recurvumn. isp. are actively filled with gray mudstone from above through the permanently open median tunnel. The trace fossil belongs to the category sequestrichnia, which is typical of oxygenated deep-sea environments characterized by seasonal or episodic supply of organic matter into a generally oligotrophic environment.P. recurvumn. isp. was produced by a “worm,” probably a polychaete, which adapted to seasonal or only episodic supply of organic matter to the deep-sea floor. The tracemaker stored the organic-rich mud in the lobes for nutrition during times of low organic matter availability on the seafloor.UUID:http://zoobank.org/49555117-1c39-4658-8b49-3f3e2f47ba27

Highlights

The trace fossil Polykampton Ooster, 1869, typified by P. alpinum Ooster, 1869 from the Paleogene flysch deposits of Switzerland, was almost forgotten for more than a century and treated as a monospecific ichnogenus (Häntzschel, 1975; Seilacher, 2007)
The trace fossil belongs to the category sequestrichnia, which is typical of oxygenated deep-sea environments characterized by seasonal or episodic supply of organic matter into a generally oligotrophic environment
The dark mudstone of the lobes and their meniscate structure prove that Polykampton recurvum n. isp. is actively filled with mud of similar lithology deposited above the top of the marlstone beds

Summary

Introduction

The trace fossil Polykampton Ooster, 1869, typified by P. alpinum Ooster, 1869 from the Paleogene flysch deposits of Switzerland, was almost forgotten for more than a century and treated as a monospecific ichnogenus (Häntzschel, 1975; Seilacher, 2007). Discoveries of four new ichnospecies of Polykampton from Cretaceous–Oligocene flysch deposits (Wetzel and Uchman, 1997; Uchman and Rattazzi, 2018; Uchman et al, 2019, 2020) showed that this ichnogenus is more diverse and widespread than previously thought. The new ichnospecies derives from the Maastrichtian–Paleogene deep-sea deposits of the Northern Apennines in Italy. The objectives of this study are to add to the knowledge on: (1) the general increase in diversity of deep-sea trace fossils since the Late Cretaceous, (2) the diversification of their nutritional strategies since the Late Cretaceous (Uchman, 2004), and (3) the competitive behavior of burrowing invertebrates in generally oligotrophic environments.

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