Osteocallis mandibulus Roberts et al., 2007

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

Osteocallis mandibulus Roberts et al., 2007

( Figures 3D, H , 4A, B )

Material. Small trails on four carapace remains (NVP006, 019‒021).

Description. Shallow, small trail of arcuate grooves, mostly formed of paired scratches ( Figure 3H ), sometimes consist of a network of randomly overlapping trails ( Figure 4A, B ). Ranging in width between 0.9 to 11 mm, generally less than 0.7 mm in length.

Discussion. This ichnotaxon was recorded for the first time in dinosaur bone from continental deposits of the Upper Cretaceous of Madagascar and Utah ( Roberts et al., 2007). In the present study, O. mandibulus was recorded together with insect pupal chambers ( Cubiculum ornatus ; Figure 3D ). Because similar bioglyph appeared in both ichnotaxa, the trace-making organisms are believed to be the same ( Roberts et al., 2007). Palaeoecologically, O. mandibulus is found in nonmarine environmental settings ( Paes Neto et al., 2016). The presence of these borings suggests that the turtle bones had a relatively long time of exposure, which was sufficient to allow the silphid and histerid beetles to leave such a significant bone modification.

Producer. Necrophagous or osteophagous insects are considered to be the main producers of O. mandibulus ( Roberts et al., 2007) . They usually use their robust mouthparts for feeding.

Stratigraphic and geographic distribution. Campanian of the Qarn Ganah, Kharga Oasis (this study). Osteocallis mandibulus has been recorded from the Upper Triassic of Southern Brazil ( Paes Neto et al., 2016), Upper Jurassic of Western Colorado ( McHugh et al., 2020), the Upper Cretaceous of Utah and Madagascar ( Roberts et al., 2007), and Lower Pliocene of Italy (Collareta et al., 2023b).

Ichnogenus Radulichnus Voigt, 1977

Type ichnospecies. Radulichnus inopinatus Voigt, 1977

Diagnosis. Minute patches or shallow grooves with parallel or subparallel striae arranged side by side in transverse rows or irregularly distributed (Voigt, 1977).

Figures

FIGURE 3. (A) Nihilichnus nihilicus, circular, subcircular to ellipsoidal non-penetrating holes (arrows) on the carapace peripheral. (B, C) Karethraichnus lakkos. (B) Cluster of bowl-shaped pits (arrows) of on the carapace peripheral. (C) Small rounded holes (arrows) of which are not completely penetrating the plastron fragments. (D) External surface of carapace peripheral containing three ichnospecies Cubiculum ornatus, C. inornatus and Osteocallis mandibulus (E, F, and H, respectively). (E) Cubiculum ornatus (arrows), showing the characteristic features of the ichnospecies with well pronounced bioglyphs. (F) Cubiculum inornatus (arrow), showing details of the morphological features the ichnospecies. (G) Cubiculum isp., showing borings arranged in groups of mostly parallel to each other and infilled with sediments. (H) Osteocallis mandibulus (ellipse), showing, randomly oriented surface borings with distinct arcuate (commonly paired) scratches in turtle skeleton. Scale bars equal 0.5 cm, except for B, D and G, which are 1.0 cm, and for C, which is 0.4 cm.

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.