An unusual process structure in Tresarcus, a new acritarch genus from the Ordovician of Öland, Sweden.
Tresarcus, a new monospecific acritarch genus, is established along with the type-species Tresarcus suecicus sp. nov. It was found in samples from the upper Arenig (Lenodus sp. A conodont Zone) of the Hagudden and Horns Udde sections, Öland, Sweden. The three-arched process tip is a peculiar characteristic of Tresarcus. This structure recalls, from a morphological point of view (though at a different dimensional scale), the four-arched termination of the epidermal hairs that ornate the adaxial (upper) surface of the assimilating leaves of Salvinia natans, Adanson, 1785 (Pteridophyta). This species has an aquatic habit and the four-arched structure as the tip of the epidermal is interpreted as a device that favours buoyancy by trapping air on the leaf surface. A similar function is hypothesized for the three-arched processes of Tresarcus.
Università degli Studi di Pisa, Dipartimento di Scienze della Terra, via S. Maria 53, I 56126, Pisa, Italy
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Tropepi
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Ribecai