Phylogeny, functional morphology, and palaeoecology of basal Hippuritida (Bivalvia) from the Tithonian (Upper Jurassic) of central Europe.

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Diceratidae and Epidiceratidae are highly significant bivalves with regard to carbonate sedimentology and phylogeny. During the Late Jurassic, they form a widespread biofacies, and they are the basal representatives of the order Hippuritida. The limestones of Ernstbrunn (Lower Austria) have yielded one of the largest and best-preserved diceratid faunas of Tithonian age, and the proposed project adresses open questions on diceratid palaeoecology, functional morphology, and phylogeny by exploiting quantitative data from these samples and supplementary material from the tramberk limestones (CZ). In a first step, intraspecific variability of diceratids will be assessed by combining qualitative character analyses with classic morphometry, Fourier shape analysis, landmark analysis, and three-dimensional-shell modelling, in order to develop a modern comprehensive species concept. Subsequently, diceratids and other basal Hippuritida from Ernstbrunn and tramberk will be thoroughly revised using modern terminology and the previously developed species concepts. Based on the results, the early phylogeny of the Hippuritida will then be adressed applying a cladistic analysis. Supplementary data will be derived from material from other localities and time slices to distinguish temporal from spatial aspects, and to detect palaeobiogeographic patterns. Digital three-dimensional modelling of the rudist body and shell, using data from internal moulds and well-preserved shells, will be used to infer shell and body volumes, as well as soft anatomy, and the relationship of these parameters to the adaptive process of shell coiling and cementation. Finally, a survey of the co-occurring biota and characterisation of the microfacies will be carried out to identify and address the particular diceratid life habits and palaeoecology at Ernstbrunn and tramberk, as well as the environmental parameters that generally make a habitat suitable for colonisation by Diceratidae.