FIGURE 2. Lithological section of the Campanian Hindaw Member (the Quseir Formation) in the study area (modified after Abu El-Kheir, 2020). Arrows mark occurrences of the three turtle-bearing horizons (I‒III) studied. Abbreviations: FM = Formation. MBR = Member.
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, non-branched 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.
FIGURE 5. A sketch showing bioerosion traces colonising the turtle bones from the Campanian of the Hindaw Member (the Quseir Formation) in the Qarn Ganah area, Kharga Oasis, Egypt (1. Nihilichnus nihilicus, 2. Karethraichnus lakkos, 3. Cubiculum ornatus, 4. Cubiculum inornatus, 5. Osteocallis mandibulus, 6. Radulichnus inopinatus, 7. Osteichnus ossiobontum, 8. Osedacoides jurassicus, 9. Sulculites bellus, and 10. Machichnus ?bohemicus).
FIGURE 6. Palaeoecology and post-mortem stages of the three turtle-bearing horizons in the Qarn Ganah area, Kharga Oasis, Egypt. (A) A sketch showing the proposed life of side-necked turtle (Bothremydidae) living in small isolated ponds during the Campanian time. (B‒D) A proposed model for the formation of the three horizons of turtle concentrations.