New symmetrodonts (Mammalia, Theria) from the Purbeck Limestone Group, Lower Cretaceous, southern England

The genus Spalacotherium Owen was initially created from material collected in the Purbeck Group in 1854. A new species, S. evansae, is here described from a Purbeck site discovered in 1986; it is represented not only by lowe r and upper molars, but possibly also by milk molars. The genus Tinodon was , until now, known only from the slightly older Morrison Formation in Wyomi ng, USA; a few lower molars and an upper molar also from the site are attri buted to a new and smaller species, T. micron, which adds one more genus th at is common to the two formations. The attributed upper molar of T. micron is especially interesting in that it yields new data on a taxon widely dis cussed in symmetrodont phylogeny, while at the same time raising problems o f cusp homology. (C) 2000 Academic Press.