New information on Hauffiosaurus (Reptilia, Plesiosauria) based on a new species from the Alum Shale Member (Lower Toarcian: Lower Jurassic) of Yorkshire, UK

摘要: An almost complete, three-dimensionally preserved plesiosaurian from the Hildoceras bifrons Zone of Alum Shale Member (Whitby Limestone Formation; Lower Toarcian) Yorkshire, UK, is described in detail. This represents a new species Hauffiosaurus, H. tomistomimus, distinguished zanoni (Harpoceras serpentinum Zone, Toarcian, Germany) by proportionally shorter neck and strongly concave preaxial margin tibia. It differs longirostris (previously ‘Macroplata’ longirostris; Har. Yorkshire) absence prominent midline ridges on dorsal surface premaxillae ventral mandibular symphysis, pterygoid contact to basioccipital. Several synapomorphies support monophyletic Hauffiosaurus: broad longitudinal troughs occupy dorsolateral maxilla posterior half lateral dentary; basicranial fontanelle bounded laterally posterolaterally elongate projections an undetermined ossification; neural arch contacts rib facet all postaxial cervical vertebrae. However, systematic position as pliosauroid or basal plesiosauroid, remains uncertain. There little evidence for geographic differentiation Toarcian faunas United Kingdom Germany minor differences between abundant taxa may arise temporal offset fossils these regions, marked taxonomic are confined rare whose one other area be attributable incomplete sampling. Lack consensus relationships Jurassic plesiosaurians requires further detailed description taxa.