Actinobalanus ? sloveniensis (Thoracica, Balanoidea), a new species of cirripede from the Oligocene and Miocene of Slovenia that grew attached to wood substrates

Abstract

A new species of acorn barnacle, Actinobalanus? sloveniensis, is recorded from Oligocene and Miocene deposits in Slovenia, representing the first record of extinct balanoids attached to plant remains from this country, and in fact from the entire central Paratethys. Assemblages available include more than 200 specimens attached to tree branches and/or roots from a cypress forest (Taxodioxylon) and from estuarine mangroves (Carapoxylon). A taphonomic interpreta- tion is provided, suggesting that some of these remains represent fragments that were dislodged during a storm event and quickly embedded in what were likely to have been anoxic sediments.

The first record of a Konservat‐Lagerstätten in which early post‐settlement stages of fossil archaeobalanids (Cirripedia: Balanomorpha) are preserved

“…Actinobalanus sloveniensis Buckeridge et al. , 2020 (Figs 6–18) 2020 ? Actinobalanus sloveniensis p. 55, figs 3–7. …”

“…Remarks : Zullo & Perreault (1989) revised Actinobalanus , which in Newman & Ross (1976) included seven species, to five species [ A. actinomorphus (Moroni, 1952) , A. bisulcatus (Darwin, 1854), and A. dolosus (Darwin, 1854) plus Zullo & Perreault's two new species, A. collinsi and A. floridanus ]; Buckeridge et al. (2020) added ? A. sloveniensis , but due to insufficient material, were unable to unequivocally determine the genus.…”

“…Diagnosis (amended after Buckeridge et al. 2020): An Actinobalanus with shell low, conical, interior relatively smooth, with ribbing weak to absent; compartments thin, mono‐lamellar; basis calcareous, bi‐lamellar with a single layer of large radially arranged pores; radii solid, narrow. Scuta thin with external surface gently concave, with fine transversal growth lines and small radial ribs; articular ridge strong, developed up to one third of this margin.…”

“…Fossilization of genus Carapoxylon is common in strata of Early to Middle Miocene age in Central Europe of the Central Paratethys. The nearest existing relatives of Carapoxyylon are the genera Carapa, Xylocarpus, and Entandrophragma (Križnar & Čufar 2008;Buckeridge et al 2020). However, some wood substrates may have been gymnosperms, as there are also remains of Cupressaceae such as Taxodioxylon sp.…”

“…They concluded that at best, it can only be a stem-line representative of the Cirripedia.) Descriptions of the associated adult barnacles, attached to various sub-strates, including fossilized wood, mangrove leaves, and mollusc shells expand the record of balanomorphs from Slovenia (Buckeridge et al 2020. General balanomorph shell morphology is provided in Fig.…”