Abstract The Jurassic System (199.6-145.5 Ma; Gradstein et al. 2004 ), the second of three systems constituting the Mesozoic era, was established in Central Europe about 200 years ago. It takes its name from the Jura Mountains of eastern France and northernmost Switzerland. The term ‘Jura Kalkstein’ was introduced by Alexander von Humboldt as early as 1799 to describe a series of carbonate shelf deposits exposed in the Jura mountains. Alexander Brongniart (1829) first used the term ‘Jurassique', while Leopold von Buch (1839) established a three-fold subdivision for the Jurassic (Lias, Dogger, Malm). This three-fold subdivision (which also uses the terms black Jura, brown Jura, white Jura) remained until recent times as three series (Lower, Middle, Upper Jurassic), although the respective boundaries have been grossly redefined. The immense wealth of fossils, particularly ammonites, in the Jurassic strata of Britain, France, Germany and Switzerland was an inspiration for the development of modern concepts of biostratigraphy, chronostratigraphy, correlation and palaeogeography. In a series of works, Alcide d'Orbigny (1842-51, 1852) distinguished stages of which seven are used today (although none of them has retained its original strati graphic range). Albert Oppel (1856-1858) developed a sequence of such divisions for the entire Jurassic System, crucially using the units in the sense of time divisions. During the nineteenth and twentieth centuries many additional stage names were proposed - more than 120 were listed by Arkell (1956) . It is due to Arkell's influence that most of these have been abandoned and the table of current stages for the Jurassic (comprising 11 internationally accepted stages, grouped into three series) shows only two changes from that used by Arkell: separation of the Aalenian from the lower Bajocian was accepted by international agreement during the second Luxembourg Jurassic Colloquium in 1967, and the Tithonian was accepted as the Global Standard for the uppermost stage in preference to Portlandian and Volgian by vote of the Jurassic Subcommission ( Morton 1974 , 2005 ). As a result, the international hierarchical subdivision of the Jurassic System into series and stages has been stable for many years.

Abstract: A three-dimensionally preserved skull and parts of the postcranial skeleton of an ichthyosaur ( Leptonectes ) was found vertically oriented within on-average slowly deposited (0.5 m/My) Lower Jurassic shallow-water marls. The ichthyosaur sank headfirst into the seafloor because of its center of gravity, as anatomically similar comparably preserved specimens suggest. The skull penetrated into the soupy to soft substrate until the fins touched the seafloor. There is no evidence either for active penetration of the ichthyosaur during death agony or an acceleration by explosive release of sewer gas that would have pushed the skull into the substrate. Ichnofabrics and crosscutting relationships among trace fossils preserved therein allow analysis of stratigraphic completeness. In spite of on-average slow accumulation, the ichthyosaur-hosting sediments formed rapidly during three distinct but similar deposition-bioturbation phases. First, 10 to 15 cm of mud accumulated rapidly. Biodeformational structures subsequently produced therein imply a soupy consistency. As sedimentation slowed down, muds slightly dewatered and consolidated, as reflected by trace fossils with distinct outlines (Palaeophycus and Planolites, thereafter Thalassinoides and Chondrites). The contact with the overlying depositional interval is obliterated by biodeformational structures. Hence, the previously rapidly deposited mud must still have been soft. A short time after the third deposition-bioturbation phase, the ichthyosaur parts penetrated into the still-soft mud and started to be degraded microbially. Below the bioturbated zone, but before compaction, a concretion started to form around the ichthyosaur parts and led to their excellent preservation. During further burial, the skull-hosting concretion experienced differential compaction and moved downward relative to the underlying beds. The skull-hosting concretion penetrated through condensed deposits representing three ammonite zones. Restoring differential compaction, the initial porosity of the sediment can be estimated to have been > 70%. Compared to modern analogues, such muds are soft, as ichnofabrics imply.