Abstract
Trace fossils occur in several strata of the Devonian and Carboniferous of the eastern Anti-Atlas, but they are still poorly documented. Here, we describe a fossil swimming trace from strata overlying the Hangenberg Black Shale (correlation largely based on lithostratigraphy; Postclymenia ammonoid genozone, ca. 370 Ma old). We discuss the systematic position of the tracemaker and its body size. This ichnofossil is important for three main reasons: (1) it is considered here to be the first record of Undichna from the Devonian of Gondwana, as far as we know; (2) it is the oldest record of vertebrate trace fossils from Africa; (3) it provides a unique window into the behaviour of Late Devonian fishes for which body-fossils cannot provide direct evidence. Further, we put this discovery into the macroecological context of the palaeoenvironment following the Late Devonian Hangenberg biodiversity crisis.
Highlights
Swimming traces of fishes such as Undichna are astonishingly rare, especially when taking into account that many of these animals live close to the sediment surface
The ichnofossils are on the underside, while wave-generated ripple marks cover the upper bedding surface
Relatively similar swimming trace fossils assigned to Undichna britannica were described from the the Late Carboniferous of Spain, which was ascribed to Chondrichthyes (Soler-Gijon & Moratalla, 2001)
Summary
Swimming traces of fishes such as Undichna are astonishingly rare, especially when taking into account that many of these animals live close to the sediment surface. The oldest records of the ichnogenus Undichna date back to the Late Silurian (Knaust & Minter, 2018: U. unisulca) This ichnotaxon, U. unisulca, is not undulating like all other ichnospecies of Undichna; these ichnofossils range among the oldest published records of vertebrate traces apart from coprolites. Even in the middle Palaeozoic or in younger strata, described occurrences of Undichna and similar ichnogenera such as the amphibian traces Lunichnium and Serpentichnus are rare. Both latter ichnotaxa display a combination of continuous and/ or discontinuous sinusoidal trails associated with scattered partial or complete footprints (Braddy et al, 2003; Minter & Braddy, 2006; Turek, 1989; Walter, 1983). Such ichnofossils are known from the Carboniferous of Argentina (Buatois & Mangano, 1994; Melchor & Cardonatto, 1998), Czech Republic (Turek, 1989, 1996), England (Higgs, 1988), Spain (Soler-Gijon & Moratalla, 2001), and USA
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