Formerly unknown holes in shells of freshwater gastropods are described and assigned to the ichnogenus Nihilichnus. The smaller size range, the different substrate, and the sometimes present scratchings around the holes distinguish our praedichnion from the type ichnospecies N. nihilicus, and we propose N. covichi n. isp. for the herein presented material. The type material of N. covichi n. isp. derives from the middle Miocene (Mammal Neogene zones MN6 and MN7) lake sediments of the Steinheim Basin (Steinheim am Albuch, SW Germany); the holes occur in shells of Gyraulus trochiformis (Planorbidae) and Bania pseudoglobulus (Hydrobiidae). Further material consists of perforated shells of Nematurella bavarica (Hydrobiidae) and Galba armaniacensis (Lymnaeidae) from the early Miocene Kirchberg Formation (MN 4; SE Germany). In contrast to the other morphologically similar but marine praedichnia (e.g., Belichnus and Oichnus, recently synonymized with Sedilichnus), Nihilichnus is known from terrestrial, palustrine, freshwater (reported herein), and marine environments. Nihilichnus covichi n. isp. was probably produced by the pharyngeal teeth of durophagous tench fish (Tinca spp.; Cyprinidae).

Unattached nodules of calcareous red algae (Rhodophyta), known as rhodoliths, are widely reported and studied in places that extend from the tropics to polar latitudes. Factors controlling the distribution of the rhodolith-forming species remain poorly understood. A review of the global distribution of present-day rhodolith beds was undertaken, collating information on 106 rhodolith-forming species from 10 families, representing 21 genera distributed through 11 realms: 1) Arctic, 2) Temperate Northern Atlantic, 3) Temperate Northern Pacific, 4) Tropical Atlantic, 5) Western Indo-Pacific, 6) Central Indo-Pacific, 7) Eastern Indo-Pacific, 8) Tropical Eastern Pacific, 9) Temperate South America, 10) Temperate Australasia, and 11) Southern Ocean. The Central Indo-Pacific and Temperate Australasia proved to be the most diverse realms. Of 62 provinces across these realms, the Tropical Southwestern Atlantic, the Mediterranean Sea and the Tropical East Pacific feature the highest diversity of rhodolith-forming species. A significant proportion of the 106 species (14.2%; 15 species) are endemic to a single biogeographic province. Species richness is weakly related to sampling effort (r2=0.573) and unrelated to littoral area (r2=0.012). Even when high latitude provinces are excluded from the analysis, no correlation between species richness and littoral was found (r2 = 0.0005). A wider, evolutionary-time framework revealed that the existence of marine barriers and the geological age of their final emplacement are key elements to explaining compositional differences between the rhodoliths of former contiguous areas (e.g., Pacific versus Atlantic shores of Panama and Costa Rica, in the Central America; eastern Mediterranean Sea versus Red Sea and Gulf of Aden). Finally, we propose that the lower diversity of the rhodolith-forming species in the tropical Pacific Ocean when compared to the Atlantic Ocean (23 versus 33 spp.), may be linked to the higher abundance of corals and coral reefs in the Pacific, which act as competitors with coralline algae for space.

In contrast to other kinds of biological interactions, symbiosis is a scarcely investigated aspect of the fossil record. This is largely due to taphonomic biases that often frustrate any attempt to make a strong case that two organisms shared an intimate association in life. Among extant marine vertebrates, the sea turtles (Cheloniidae and Dermochelyidae) bear a broad and diverse spectrum of epibiotic symbionts, including specialists such as the turtle barnacles (Chelonibiidae and Platyleapadidae). Here, we reappraise an early Oligocene (Rupelian) fossil cheloniid skeleton, featuring the remains of cirripedes on the exterior of its entoplastron, from the Rauenberg fossil-lagerstätte, southwestern Germany. The barnacle specimens are assigned to Protochelonibia melleni, an extinct protochelonibiine species and the geologically oldest known member of Chelonibiidae. In the light of taphonomic and palaeoenvironmental considerations, and given that the extant chelonibiids are mostly known as epizoic symbionts of sea turtles, we conclude that this unique fossil association resulted from the epizoic growth of the barnacles on the external surface of the plastron of the turtle during its lifetime. This remarkable fossil association provides evidence that chelonibiids, including the extinct protochelonibiines, have been chelonophilic epizoans for more than 30 Myr. A survey of the trace and body fossil records shows that platylepadids are also likely as old as the Rupelian as is their symbiotic association with cheloniid hosts. This early emergence of the modern-looking, turtle-dwelling barnacle lineages corresponds to a climate-driven phase of major radiation and taxonomic turnover among sea turtles at the Eocene–Oligocene transition.