An exceptional concentration of marine fossils associated with wood-fall in the Terhagen Member (Boom Formation; Schelle, Belgium), Rupelian of the southern North Sea Basin

Abstract

A large fragment of driftwood was discovered in the marine Terhagen Member (Boom Formation, NP23) at Schelle (Belgium), representing the first well-documented case of wood-fall in the Rupelian of the North Sea Basin. This trunk with a side-branch, identified as Cupressinoxylon sp. (Cupressaceae), caused a large irregularity on the sea bottom, creating a unique microenvironment which allowed colonization by some taxa virtually absent elsewhere in the Boom Formation. The fossils were further concentrated in a silty lens against the trunk by the effects of prolonged wave-driven turbulence. This lens comprised a large set of compartmental plates of the turtle barnacle Protochelonibia hermani Gale sp. nov., possibly part of a single colony originally attached to a turtle. The material includes the best preserved plates of Protochelonibia known to date, yielding new information on the construction of its shell. Additionally, a disarticulated tooth set of 154 teeth of Carcharias contortidens (Agassiz, 1843) was found, the first such discovery in more than 100 years. An articulated dentition of this taxon, initially studied by Leriche (1910), is refigured herein. Some very rare valves of the bivalve Palliolum permistum (Beyrich, 1848) are identified and the gastropod Amblyacrum cf. roemeri (von Koenen, 1867) is reported here for the first time from the Belgian Rupelian. The teleost otolith assemblage comprises ca 30,000 specimens belonging to 11 species only, of which Trachurus reineckei Hoedemakers sp. nov. is new to science and Myoxocephalus primas (Koken, 1891) and Capros siccus Schwarzhans, 2008 are new for the Belgian Rupelian. The new species represents the earliest record of the thermophilic genus Trachurus in the Oligocene of the North Sea Basin. Liparis minusculus Nolf, 1977 is synonymized with Myoxocephalus primas, whereas Erythrocles ohei Schwarzhans, 1994 is transferred to the genus Trachurus.