Clionolithes convexus Wisshak 2017, comb. nov.

Clionolithes convexus (Hofmann, 1996) comb. nov.

Fig. 10

Nododendrina convexa Hofmann, 1996: 82, pl. 9, figs 5–6, pl. 10, figs 1–2.

non Nododendrina convexa – Thuy et al. 2014: fig. 1h (? C. pannosus).

Original diagnosis

Rosettenartiges Bohrgangsystem in konvex-gewölbter Form mit starkem Gang im zentralen Bereich, von dem aus dünner werdende Gänge in die peripheren Rosettenbereiche abzweigen. [Translation: Rosetted boring system in a convex-arched shape with prominent main gallery in the centre, from which galleries emerge and taper towards the peripheral area.]

Emended diagnosis

Oblique inlet gallery leading to a wide, convex-arched and elongated main cavity in the centre of the trace, from which galleries emerge and sharply taper towards the periphery and towards the substrate surface, forming numerous fine connections. Surface texture smooth, except for inlet tunnel, which may bear short and spiny protrusions.

Original description

The rosette consists of a very pronounced gallery in the central area (diameter 100 to 150 µm), from where few and slightly thinner galleries branch (diameter 60 to 80 µm). From these, further galleries emerge, ramify and taper. Like in Rosetten-Form A, there is a remarkably large penetration depth of the boring trace in the shell […] exceeding that of all other rosette types. Distances of up to 400 µm to the shell surface were measured. This penetration depth, together with the relatively small diameter of the rosette (ca 1 to 2 mm), lead to a nearly dome-shaped morphology of the boring trace in casts and its characteristic appearance. [Translated from German]

Supplementary description

A prominent and diagnostic feature not addressed in the original description is the arched initial gallery leading from the initial vertical point of entry to the main trunk of the trace. This gallery is present not only in the lectotype (Fig. 10), but also in all of the reinvestigated paralectotypes, and in contrast to the main trace often exhibits a slight hairy texture. Thereby the course of the initial gallery ranges from an immediately bent and almost prostrate orientation to a more arcuate morphology that exceeds the main trace in penetration depth.

Type material, locality and horizon

The type material comprises various specimens in several epoxy resin casts of Ostrea oyster shells sampled in an old quarry near the northern limit of the Swedish lake island Ivö; lower Campanian, Cretaceous. Of the two specimens on the cast indicated as “ holotype ”, the one illustrated on Hofmann’s plate 9, figure 5–6 is hereby designated as the lectotype (Fig.10 A–C),rendering the other specimens on this and three other casts paralectotypes. The type material is deposited at the Institut für Geowissenschaften, Goethe Universität, Frankfurt, Germany (Bo 5/146: 146.1 = lectotype and one paralectotype, 146.2 to 146.4 = further paralectotypes).

Remarks

Originally established within the ichnogenus Nododendrina, which is a junior synonym of Olkenbachia, which in turn is a junior synonym of Clionolithes. Spelling changed to the masculine convexus in order to correlate with the ichnogenus in gender.