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Semi-articulated remains of a large chelonioid turtle from the Turonian strata (Upper Cretaceous; ca. 93.9–89.8 Myr) near Sant'Anna d'Alfaedo (Verona province, northeastern Italy) are described for the first time. Together with the skeletal elements, the specimen also preserves pebbles inside the thoracic area which are lithologically distinct from the surrounding matrix. These allochthonous clasts are here interpreted as geo-gastroliths, in-life ingested stones that resided in the digestive tract of the animal. This interpretation marks the first reported evidence of geophagy in a fossil marine turtle. SEM-EDS analysis, together with macroscopic petrological characterization, confirm the presence of both siliceous and carbonatic pebbles. These putative geo-gastroliths have morphometries and size ranges more similar to those of gastroliths in different taxa (fossils and extant) than allochthonous "dropstone" clasts from the same deposit that were carried by floating vegetation A dense pitted pattern of superficial erosion is microscopically recognizable on the carbonatic gastroliths, consistent with surface etching due to gastric acids. The occurrence of a similar pattern was demonstrated by the experimental etching of carbonatic pebbles with synthetic gastric juice. Gut contents of modern green sea turtles (Chelonia mydas) were surveyed for substrate ingestion, providing direct evidence of geophagic behavior in extant chelonioids. Comparison with modern turtle dietary habits may suggests that the pebbles were ingested as a way to supplement calcium after or in preparation for egg deposition, implying that the studied specimen was possibly a gravid female. [ABSTRACT FROM AUTHOR]

Modern cetaceans are considered the best anatomical and ecological analogue for many Mesozoic secondary aquatic reptiles. Such similarities extend also after the death of these phylogenetically distant amniotes, when the sinking and decomposition of large carcasses in marine environments (deadfalls) follow common biostratinomic processes. Most taphonomic studies on Mesozoic deadfalls have been limited to shallow-water settings, often neglecting deeper waters. Here we provide a detailed taphonomic survey of ichthyosaurs, pliosaurs and metriorhynchoids from the pelagic Middle-Upper Jurassic Rosso Ammonitico Veronese (RAV) of northeastern Italy. Our taphonomic revision of the RAV tetrapod record highlights a common poor state of preservation of the bones, often associated with abundant macrofossils, consistent with a prolonged exposure of carcasses on a well-oxygenated seafloor. For the first time we confirm the role of nautiloids as active mobile scavengers by means of tens of beak elements found closely associated with, or even piercing, the bones. Hexanchiform shark teeth are also found associated with the carcasses, supporting a distinctive deep-water mobile scavenging community. Echinoids, sponges and other bioeroders are identified as representative of the enrichment-opportunist stage, and a high concentration of belemnites is believed to be indicative of mass-spawning deaths in the surroundings of the carcasses. Abundant crinoids are recognized as part of the reef stage by colonization of the eroded bones. While some of our data deviate from previous Mesozoic reptile-falls from shallow-waters, they are consistent with findings at Recent whale-falls in bathyal zones, and overall represent a precious window into the complex ecology of Jurassic open seas. [ABSTRACT FROM AUTHOR]

Simple Summary: Nowadays, the infraorder Delphinida consists of oceanic dolphins and porpoises plus a handful of riverine and (sub-)Arctic forms. Overall, the delphinidans account for more than half of the living cetacean species, thus comprising the core of present-day marine mammal diversity. The fossil record indicates that a critical phase of the evolutionary history of Delphinida occurred during the Early Miocene (c. 23.0–16.0 million years ago) when the extinct genus Kentriodon first appeared and became widespread worldwide. Our paper deals with a new delphinidan fossil from northeastern Italy, namely, an incomplete skull with ear bones dating back to 20.4–19.0 million years ago. This new specimen is recognized herein as a representative of Kentriodon and specifically as the first unambiguous member of this genus from the Euro-Mediterranean region. Our new find represents the best candidate for being the most ancient member of Kentriodon. The evolutionary success of Kentriodon (which lasted until the Late Miocene, less than 11.3 million years ago) may have been favored by the evolution of a peculiar biosonar system exploiting narrow-band high-frequency sounds, which in turn would have been hardly detectable by large-bodied, predatory toothed whales. Furthermore, Kentriodon was seemingly characterized by a proportionally larger brain compared to many coeval toothed whales, which in turn may evoke enhanced behavioral capabilities. Nowadays, the infraorder Delphinida (oceanic dolphins and kin) represents the most diverse extant clade of Cetacea, with delphinids alone accounting for more than 40% of the total number of living cetacean species. As for other cetacean groups, the Early Miocene represents a key interval for the evolutionary history of Delphinida, as it was during this time span that the delphinidans became broadly distributed worldwide, first and foremost with the widespread genus Kentriodon and closely related forms. Here, we report on a new odontocete find from Burdigalian (20.4–19.0 Ma) deposits of the Friulian-Venetian Basin of northeastern Italy, consisting of the partial cranium of a small delphinidan with associated ear bones (right periotic, stapes, malleus and tympanic bulla). Osteoanatomical considerations and comparisons allow us to assign the studied specimen to the genus Kentriodon. This is the first confirmed record of Kentriodon from Europe as well as from the whole proto-Mediterranean region. Stratigraphic and phylogenetic considerations suggest that our new specimen may represent the geologically oldest member of Kentriodon. The evolutionary success of Kentriodon may correlate with the emergence of narrow-band high-frequency echolocation as a possible strategy to escape acoustic detection by large marine predators such as the squalodontids. In addition, the relatively high encephalization quotient of Kentriodon spp. may have provided these early dolphins with some kind of competitive advantage over the coeval non-delphinidan odontocetes. [ABSTRACT FROM AUTHOR]