Miocene sepiids (Cephalopoda, Coleoidea) from Australia
- 1Institute of Geology and Palaeontology, Faculty of Science, Charles University in Prague, Albertov 6, Prague 2, 128 43, Czech Republic
- 2Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia
- 3Earth and Planetary System Science, Department of Natural History Sciences, Hokkaido University, Sapporo, Japan
Abstract. Two sepiid genera, Notosepia Chapman, 1915, and Sepia Linnaeus, 1758, are described from the Neogene deposits of Australia. A new and unique record of the middle Miocene Sepia sp. is reported from southern Australia. Based on similarities to contemporaneous sepiids, the new sepiid cuttlebone described herein belongs to the genus Sepia. Notosepia cliftonensis is suggested herein to be a descendant of the archaeosepiid stem lineage. Microstructures (lamella-fibrillar nacre is the nacre Type II of septa and pillar prismatic layers) of the excellently preserved cuttlebone of Sepia sp. display a modern character of the phragmocone, fully comparable to the recent taxa. The stratigraphically well-calibrated (based on foraminifera) cuttlebone represents the first unambiguous fossil record of the genus Sepia from the Southern Hemisphere. It significantly extends the biogeographical distribution of modern sepiids in the Miocene and suggests the existence of a sepiid eastward migratory route. Moreover, the presence of both conservative- and modern-type cuttlebones suggests a dual colonisation of Australian waters: the first (archaeosepiid) during the late Eocene–late Oligocene and the second (sepiid) during the early Miocene.