The occurrence of the coronuloid barnacle Chelonibia Leach, 1817 as an encruster on mammalian bone in the central Mediterranean Sea

Among the turtle and whale barnacles (Coronuloidea: Chelonibiidae, Coronulidae, †Emersoni-idae and Platylepadidae), the members of the chelonibiid species Chelonibia testudinaria (Linnaeus, 1758) are known as epizoic barnacles that can attach to a rather wide spectrum of substrates (pri-marily sea turtles, crabs and sirenians). At present, three living morphs of C. testudinaria have been recognised; of these, the less host-specific is the patula morph, which also displays a remarkably simple, unspecialised shell architecture. Here we report on several chelonibiid shells, referred to the patula morph of C. testudinaria, encrusting a cetacean scapula collected from the floor of the Adriatic Sea facing Salento (Apulia Region, southeastern Italy) and tentatively referred to Tursiops truncatus (Montagu, 1821). This is one of the few records worldwide of a coronuloid barnacle from an inanimate substrate, as well as the second as an encruster on mammalian bone. Such an unusual occurrence is then briefly discussed in the broader framework of the coronuloid commensalism and substrate habits.

Mammalian bone palaeohistology: a survey and new data with emphasis on island forms

The interest in mammalian palaeohistology has increased dramatically in the last two decades. Starting in 1849 via descriptive approaches, it has been demonstrated that bone tissue and vascularisation types correlate with several biological variables such as ontogenetic stage, growth rate, and ecology. Mammalian bone displays a large variety of bone tissues and vascularisation patterns reaching from lamellar or parallel-fibred to fibrolamellar or woven-fibred bone, depending on taxon and individual age. Here we systematically review the knowledge and methods on cynodont and mammalian bone microstructure as well as palaeohistology and discuss potential future research fields and techniques. We present new data on the bone microstructure of two extant marsupial species and of several extinct continental and island placental mammals. Extant marsupials display mainly parallel-fibred primary bone with radial and oblique but mainly longitudinal vascular canals. Three juvenile specimens of the dwarf island hippopotamidHippopotamus minorfrom the Late Pleistocene of Cyprus show reticular to plexiform fibrolamellar bone. The island muridMikrotia magnafrom the Late Miocene of Gargano, Italy displays parallel-fibred primary bone with reticular vascularisation and strong remodelling in the middle part of the cortex.Leithiasp., the dormouse from the Pleistocene of Sicily, is characterised by a primary bone cortex consisting of lamellar bone and a high amount of compact coarse cancellous bone. The bone cortex of the fossil continental lagomorphProlagus oeningensisand three fossil species of insularProlagusdisplays mainly parallel-fibred primary bone and reticular, radial as well as longitudinal vascularisation. Typical for large mammals, secondary bone in the giant rhinocerotoidParaceratheriumsp. from the Late Oligocene of Turkey is represented by dense Haversian bone. The skeletochronological features ofSinomegaceros yabei, a large-sized deer from the Pleistocene of Japan closely related toMegaloceros, indicate a high growth rate. These examples and the synthesis of existing data show the potential of bone microstructure to reveal essential information on life history evolution. The bone tissue and the skeletochronological data of the sampled island species suggest the presence of various modes of bone histological modification and mammalian life history evolution on islands to depend on factors of island evolution such as island size, distance from mainland, climate, phylogeny, and time of evolution.