Sequestrichnia - an ethological category of marine trace fossils recording the collection and stowage of nutritional material within burrows Author Uchman, Alfred Jagiellonian University, Faculty of Geography and Geology, Institute of Geological Sciences, Gronostajowa 3 a, PL- 30 - 387 Kraków (Poland) alfred. uchman @ uj. edu. pl (corresponding author) alfred.uchman@uj.edu.pl Author Wetzel, Andreas Department of Environmental Sciences - Geology, Universität Basel, Bernoullistrasse 32, CH- 4056 Basel (Switzerland) andreas. wetzel @ unibas. ch andreas.wetzel@unibas.ch text Comptes Rendus Palevol 2024 2024-08-30 23 22 325 338 http://dx.doi.org/10.5852/cr-palevol2024v23a22 journal article 305524 10.5852/cr-palevol2024v23a22 fefdf6a6-89e6-4b61-8d87-ff08580d85f9 1777-571X 13595789 urn:lsid:zoobank.org:pub:FAE07554-6F51-46B5-A81D-EA7D9091E776 Ichnogenus Zoophycos Massalongo, 1855 ( Fig. 1 ) Zoophycos represents a regularly to irregularly coiled, simple to complex lobate spreite burrow that has shown changes in shape, size, and geometry through the Phanerozoic (e.g. Seilacher 1977b ; later refined by Chamberlain 2000 and Zhang et al. 2015 ). For most Zoophycos older than the late Mesozoic, different ways of spreite production and behaviour are possible, including fodinichnial behaviour (e.g. Olivero & Gaillard 1996 ). In contrast, for Late Cretaceous to modern Zoophycos , sequestrichnial behaviour of the producers appears to be common. These are outlined here. Evidence for sequestration of sediment on the seafloor is given by the colour of the spreite fill in combination with enlarged organic carbon values. The spreite consists of alternating lamellae containing host sediment and material likely sequestered on the seafloor and transferred downward; pellets may occur in both types of lamellae ( Fig. 1 ). The sequestered sediment is commonly darker in greenish-grey host sediment or grey in reddish host sediment. In both cases, the organic carbon content of the spreite fill is higher than that of the host sediment; for example, the black spreite material of Paleocene Zoophycos (Gurnigel Flysch; Seligraben/Gurnigelbad, Switzerland ) contains 1.1-1.7% Corg compared to 0.5-0.7% Corg in the green host sediment (see Wetzel & Uchman 1998 : fig. 1d, e). In the Eocene of Arnakatxa Headland near Bilbao, 0.3-0.7% Corg occurs in grey spreite material and <0.1% Corg in red limestone lutite alternations. However, in deep oceanic settings, also lighter material deposited during periods of enhanced nannoplankton productivity can be transferred downward ( Fig. 1A ). Other tracers, e.g. volcanic ash, also record a downward sediment transfer (e.g. Kotake 1991 ). For Pleistocene and Holocene Zoophycos , chronometric age data record a sequestration of surface material as the spreite fill is generally younger than the host sediment (e.g. Löwemark & Werner 2001 ; Leuschner et al. 2002 ; Küssner et al. 2018 ). In well-dated sediments, Zoophycos appears to be produced when environmental conditions switch to a starved sedimentation regime ( Küssner et al. 2018 ) or during times of enhanced seasonality (e.g. Löwemark et al. 2006 ; Wetzel et al. 2011 ; Dorador et al. 2016 ). The Zoophycos producer stows the sequestered material commonly in the form of mud lamellae or pellets in the spreite. Pellets, however, occur in both host and sequestered sediment, suggesting that they could have provided “seed” microbes housed in the gut to the spreite “bioreactor” ( Fig. 1C ). Therefore, a priming scenario appears realistic, in particular as subsequent lamellae overlap previous ones, indicating partial reworking and utilization of the spreite fill by the tracemaker ( Fig. 1D ). Since Zoophycos represents very likely a lifetime burrow of its producer (e.g. Wetzel & Werner 1980 ), the worm-like tracemaker probably took advantage of priming on a time scale of months to years.