The northernmost Jurassic rudists: A revision of the Diceratidae and Epidiceratidae (Bivalvia: Hippuritida) from the Korallenoolith of northern Germany

The Late Jurassic (Late Oxfordian) Diceratidae and Epidiceratidae (Bivalvia: Hippuritida) from the Korallenoolith Formation at Salzhemmendorf south of Hanover (northern Germany) are revised. Due to poor preservation of the material, the species names Diceras koeneni Dubbers, 1888 and Diceras gracile Dubbers, 1888, established on the re-studied material, are regarded as nomina dubia. The specimens are assigned to the genera Diceras, Epidiceras and Plesiodiceras. For all three genera the occurrence at Salzhemmendorf constitutes their northernmost record. The rudist faunal community suggests a largely tropical to subtropical environment. Palaeoclimate and facies are thought to have restricted further expansion of the Diceratidae and Epidiceratidae towards the north.