Exceptional preservation of embryos in the actinopterygian Saurichthys from the Middle Triassic of Monte San Giorgio, Switzerland

Abstract

New excavations in the famous Monte san Giorgio area, close to the historical sites where the cassina beds crop out (Lower Meride Limestone, Early Ladinian), revealed an interesting vertebrate fauna, including several specimens of the actinopterygian fish Saurichthys. Among the prepared specimens, three specimens of Saurichthys contain embryos, and in one example the embryos are preserved with traces of the soft parts, most probably phosphatized musculature. this discovery is of particular relevance because fossil embryos with preserved soft parts are extremely rare. In addition, although viviparity had previously been described for Saurichthys, the new specimens are rather better evidence and add further support to this reproductive mode.

Facies, depositional environment, and palaeoecology of the Middle Triassic Cassina beds (Meride Limestone, Monte San Giorgio, Switzerland)

“…Moreover, limiting the diffusion of chemical elements, the sealing effect of these biofilms creates particular geochemical microenvironments favourable to mineralization. This latter effect may account for the preservation of the fine structure of soft parts observed in some embryos of Saurichthys (Renesto and Stockar 2009).…”

“…Individuals reach up to 44 cm in standard length. Four of them contain preserved embryos (Renesto and Stockar 2009). The bulk of the unprepared material appears to be referable to S. curionii as well, with specimens mainly between 20 and 45 cm long.…”

Saurichthys and other fossil fishes from the late Smithian (Early Triassic) of Bear Lake County (Idaho, USA), with a discussion of saurichthyid palaeogeography and evolution

“…Beltan & Tintori 1980, Kogan et al 2009, Mutter et al 2008, Rieppel 1985. At least some Middle and Late Triassic species are known to have been viviparous (Bürgin 1990, Bürgin et al 1991, Griffith 1977, Renesto & Stockar 2009, Rieppel 1985.…”

“…skull and body fragments, complete specimens Alessandri (1910), Bassani (1886), Bellotti (1857Bellotti ( , 1873, Bürgin (1990), Griffith (1959), Deecke (1889), Renesto & Stockar (2009), Rieppel (1985, Tintori & Lombardo (1999) complete specimen Griffith (1962), Tintori & Gozzi (2005) basins; López-Arbarello 2004), and the Early Jurassic saurichthyid Saurorhynchus is exclusively known from marine deposits (e.g. Gardiner 1960, Neuman & Wilson 1985, Thies 1985.…”

Saurichthys (Pisces, Actinopterygii) teeth from the Lower Triassic of Spitsbergen, with comments on their stable isotope composition (δ13C and δ18O) and X−ray microtomography

“…Although the dentition of Saurichthys ("lizard fish") is fairly well known from partial and complete articulated skeletons, isolated teeth are not easily determined to either generic or species level. Several complete or nearly complete skeletons of Saurichthys have recently been described from many localities world− wide (Griffith 1962;Duffin and Gaździcki 1977;Mutter et al 2008;Kogan et al 2009;Renesto and Stockar 2009;Wu et al 2009Wu et al , 2011Schmid and Sánchez− Villagra 2010;Kogan 2011;Romano et al 2012), representing a considerable ad− vance in our knowledge of the group. Saurichthys was a relatively cosmopolitan ge− nus, being so far found in Triassic deposits on every continent except Antarctica.…”