Radulichnus inopinatus Voigt, 1977

Hedeny, Magdy El, Mohesn, Sara, Tantawy, Abdel-aziz, El-Sabbagh, Ahmed, AbdelGawad, Mohamed & El-Kheir, Gebely Abu, 2023, Bioerosion traces on the Campanian turtle remains: New data from the lagoonal deposits of the Quseir Formation, Kharga Oasis, Egypt, Palaeontologia Electronica (a 40) 26 (3), pp. 1-21 : 8-10

Radulichnus inopinatus Voigt, 1977

( Figure 4C, D )

Material. Many arcuate bundles on three carapace remains (NVP019‒021).

Description. Parallel to sub-parallel arcuate bundles closely spaced in groups, each group ranges from six to eight patches, covering some areas of the turtle skeletons.

Discussion. Radulichnus inopinatus occurs commonly on the external surfaces of the carapace of some turtle skeletons, uncovering the whole surfaces. In some cases, the studied ichnotaxon is associated with Osteocallis mandibulus . The latter ichnospecies differ from R. inopinatus by their small trail of arcuate grooves and sometimes consist of a network of randomly overlapping trails. Two ichnospecies of Radulichnus have been described: Radulichnus inopinatus and R. transversus . The second ichnospecies was characterised by parallel and short grooves (less than 1 mm in length) arranged in rows, concentrated in the central part of the inner surface of the valves of the clam species Anomalocardia brasiliana . Radulichnus inopinatus corresponds to the marks left by gastropods, while R. transversus to those left by polyplacophorans ( Lopes and Pereira, 2019). Radulichnus inopinatus has been recognised from invertebrate shells ( Lopes and Pereira, 2019), as well as from vertebrate remains ( Jagt et al., 2020). Producer. Invertebrate (chiefly molluscan) shells and polyplacophorans (chitons) (Voigt, 1977; Jagt, 2003; Gibert et al., 2007; Lopes and Pereira, 2019; Collareta et al., 2023b).

Stratigraphic and geographic distribution. Campanian of the Qarn Ganah, Kharga Oasis (this study). Radulichnus inopinatus was previously recorded from the Middle Devonian of Germany (Bohatý, 2011), Maastrichtian of Netherlands and Belgium ( Jagt, 2003; Mulder et al., 2005; Janssen et al., 2013), Pliocene of France and Italy ( Gibert et al., 2007; Collareta et al., 2023b), and Pleistocene of Southern Brazil ( Lopes and Pereira, 2019).

Ichnogenus Osteichnus Thenius, 1988a

Type ichnospecies. Asthenopodichnium ossibiontum ( Thenius, 1988a)

Diagnosis. U-shaped burrows having a spreite (weblike construction) between the two limbs of the burrow, with a tube diameter of 3–5 mm, at an average notch length of 8–15 mm. Depth of U-constructions up to 7 mm ( Thenius, 1988a).

Figures

FIGURE 4. (A, B) Osteocallis mandibulus. (A) Small randomly oriented surface borings. (B) Close up view of A, showing small randomly oriented surface borings. (C, D) Radulichnus inopinatus, parallel to sub-parallel arcuate bundles closely spaced in groups. (E) Osteichnus ossiobontum, parallel borings with fused U-notches, inclined to the bone surface. (F) Osedacoides jurassicus, small simple borings in bone (yellow arrows) penetrating into the turtle bone. Note the occurrence of some Cubiculum isp. traces (red arrows). (G) Sulculites bellus, smooth, slender narrow, nonbranched straight to curved grooves. (H) Machichnus?bohemicus, shallow serial parallel or subparallel grooves (arrows) in carapace peripheral. Scale bars equal 1.0 cm, except for B, D, and E, which are 0.5 cm.