Despite the common and widespread occurrence of turtle shell remains in many fossil vertebrate assemblages worldwide, few palaeontological studies have addressed the palaeoecological significance of turtle bone modification features. Here, we report on ichnofossils occurring on carapacial and plastral bones of the small terrapin genus Mauremys (Testudinoidea, Geoemydidae) from Upper Pliocene deposits exposed at La Serra, in the Valdelsa basin of Tuscany (central Italy). The trace fossil assemblage includes Karethraichnus lakkos, Gunnellichnus cf. moghraensis, and Thatchtelithichnus holmani, all of which are found on the nonvisceral surfaces of the shell. As observed elsewhere, some of the Karethraichnus lakkos borings occur along the epidermal sulci that mark the border between adjacent keratinous scutes. Based on the relevant literature, the studied ichnofossils are interpreted as being due to the parasitic action of leeches/spirorchiid liver flukes (K. lakkos and Thatchtelithichnus holmani) and to algal/fungal/bacterial (sub)cutaneous infections (Gunnellichnus cf. moghraensis). The observed stock of bioerosional features compares favourably with the Italian Pliocene climate, which was warmer and wetter than today.

Specimens of the rugose coral Streptelasma? sp. are found intergrown with a host bryozoan Oanduellina bella in the lower Katian of Estonia. Rugosa also occur in the bryozoan Proavella proava. This is the earliest and only known record of endobiotic rugose symbionts in cryptostome bryozoans from the Late Ordovician of Baltica. The erect bryozoan colonies provided symbiotic Rugosa with both a higher and more advantageous tier for feeding in the water column and a hard substrate that these encrusting Rugosa required. The rugose corals may have protected the bryozoans with their stinging cells against predators. The lack of malformations in the bryozoan zooid architecture and their normal dimensions around the Rugosa show that the relationship between the Rugosa and bryozoans could have been mutualistic, which is similar to many other Rugosa-bryozoan associations in the Late Ordovician of Baltica, although the exact nature of this association remains uncertain.