Caulostrepsis cretacea ( Voigt, 1971 )

Gaaloul, Nadia, Uchman, Alfred, Ali, Syrine Ben, Janiszewska, Katarzyna, Stolarski, Jarosław, Kołodziej, Bogusław & Riahi, Sami, 2023, In vivo and post-mortem bioerosion traces in solitary corals from the upper Pliocene deposits of Tunisia, Acta Palaeontologica Polonica 68 (4), pp. 659-681 : 667-669

Caulostrepsis cretacea ( Voigt, 1971)

Figs. 8A , 12C 2 .

Diagnosis.—Galleries bent in a long, narrow U-form with the inward-facing walls of the limbs fused by complete removal; the original position of the median wall is sometimes indicated by a very shallow axial depression along the structure. Vane absent. Transverse section always flattened-ellip- tical but showing gradual decrease in width toward the aperture. Shape of aperture flattened-oval (cited from Bromley and D’Alessandro 1983).

Material.—INGUJ265P151, 156, 166; U-shaped, tongue depressions on the surface of coralla; El Melah stream section, the upper part of the Argiles de Sidi Barka Formation (upper Pliocene) of Tunisia.

Description.—Straight to slightly winding depression/gallery, which is distinctly gradually widened towards the distal semicircular termination, from 0.25 mm up to 1 mm, up to 10.5 m long, without vane. In the illustrated case, two groves converge in the proximal part and diverge at an angle of 40°. About 1 mm before the aperture, the galleries diverge again. It is not clear whether this is an effect of the intersection of two galleries or the divergence of one fused gallery. The borings are concentrated within the corallum wall. Some depressions have a roof in the most distal part.

Remarks.— Bromley and D’Alessandro (1983) observed broader specimens, which are at least 2 mm wide and never show interpenetration. However, the characteristic distal widening is diagnostic of this ichnospecies. Originally, this ichnospecies was described by Voigt (1971) as Dodecaceria cretacea . Later, it was transferred to Trypanites by Bromley (1972) and finally to Caulostrepsis by Bromley and D’Alessandro (1983). Voigt (1971) and Bromley and D’Alessandro (1983) regarded it as having been produced by the cirratulid polychaete Dodecacería concharum Örsted, 1843 , but Gibson (2016) who examined the material studied by the aforementioned author and compared it with recent borings of this polychaete, questioned this view and suggested that Caulostrepsis cretacea is similar to the borings of Polydora .

Stratigraphic and geographic range.—Santonian (possibly Cenomanian) ( Voigt 1970)–Recent. However, poorly documented specimens are known since the Cenomanian ( El-Hedeny 2007) to the Recent ( Voigt 1970); the Atlantic and the Mediterranean regions.

Caulostrepsis avipes Bromley and D’Alessandro, 1983

Figs. 8C , 9A 8 .

Emended diagnosis.— Caulostrepsis with or without a vane, dumbbell-shaped to flattened oval in cross section, characterized by the possession of two to four grooves branched out from the aperture. The grooves are shorter than the triple width of the boring. In some cases, the branching occurs beneath the substrate surface, so that each diverging branch bears its own aperture.

Material.— INGUJ265P153, 176; U-shaped, tongue depressions, preserved on the surface of coralla; El Melah stream section, the upper part of the Argiles de Sidi Barka Formation (upper Pliocene) of Tunisia.

Description.—Surface or shallow subsurface, straight, curved, or slightly winding tongue-like depression/gallery with or rarely without vane, up to 9–13 mm long, up to 0.8– 1.5 mm wide. The groves branching from the aperture are slightly divergent and bifurcating at the end. The borings are concentrated within the corallum wall.

Remarks. —Most probably, the surface depressions resulted from erosion/collapse of the roof of subsurface galleries. The roof is still present in the distal part of some galleries. Information that the grooves branching out from the apertures are much shorter than the remaining part of the boring is added to the diagnosis by Bromley and D’Alessandro (1983) in order to describe the distinction between Caulostrepsis avipes and the new ichnospecies described in the following. The grooves were probably produced by the tentacles of spionid polychaetes. It is the first appearance of this ichnospecies beyond the Upper Cretaceous, where it is documented by Reis (1921) but without assignation to any ichnotaxon, and by Hillmer and Schulz (1973) under Ramosulcichnus biforans Gripp, 1967 , which was transferred to Caulostrepsis and split into Caulostrepsis as C. biforans and C. avipes (see Bromley and D’Alessandro 1983).

Stratigraphic and geographic range.—Santonian–Maastrichtian of Germany, Denmark, England, and Ukraine, upper Pliocene of Tunisia.

Figures

Fig. 8. Caulostrepsis, a domichnion produced by polychates, in the skeleton of caryophylliid coral Ceratotrochus (Edwardsotrochus) duodecimcostatus Goldfuss, 1826), from the El Melah stream section, the upper part of the Argiles de Sidi Barka Formation (upper Pliocene) of Tunisia. A. Caulostrepsis cretacea (Voigt, 1971), INGUJ265P156. B. Caulostrepsis taeniola Clarke, 1908 and Pinaceocladichnus onubensis Mayoral, 1988 (Pn), INGUJ265P154. C.Caulostrepsis avipesBromleyand D’Alessandro,1983,INGUJ265P176.D.A clusterofCaulostrepsis taeniolaClarke,1908,INGUJ265P162.E–G.Caulostrepsis penicillus isp. nov. E. INGUJ265P158 holotype (a), and paratype (b). F. INGUJ265P174 paratype. G. INGUJ265P172, partial views (G1, G2).

Fig.12. Pinaceocladichnus onubensis Mayoral,1988, (a domichnion produced by ctenostome bryozoans) and associated trace fossilsin the skeleton of caryophylliid coral Ceratotrochus (Edwardsotrochus) duodecimcostatus (Goldfuss, 1826), from the El Melah stream section, the upper part of the Argiles de Sidi Barka Formation (upper Pliocene) of Tunisia.A. INGUJ265P152, different placesof the same corallum (A1,A2). B. INGUJ265P154,also Maeandropolydora elegans Bromley and D’Alessandro, 1983 (Me).C. INGUJ265P151,C1, C2 different places of the same corallum, also Caulostrepsis cretacea (Voigt,1971) (Cc).

Fig.2. Lithostratigraphy and subdivision of the Neogene and Quaternary series of northern (A) and north-eastern Tunisia (B) (Burollet 1951; Colleuil 1976).

Fig. 9. Snapshots from micro-CT images of Caulostrepsis in the skeleton of caryophylliid coral Ceratotrochus (Edwardsotrochus) duodecimcostatus Goldfuss, 1826) (INGUJ265P153), from the El Melah stream section, the upper part of theArgiles de Sidi Barka Formation (upper Pliocene) of Tunisia. A. The surface with indications of bioerosion traces, with partial transparency, and without corallum, A1–A4, respectively; Ct, Caulostrepsis taeniola Clarke, 1908; Me, Maeandropolydora elegans Bromley and D’Alessandro, 1983. B. View from the other side, B1–B4, respectively; Ca, Caulostrepsis avipes Bromley and D’Alessandro, 1983.