Chaniella, a new lower Tremadocian (Ordovician) brachiopod from northwestern Argentina and its phylogenetic relationships within basal rhynchonelliforms

The new rhynchonelliform brachiopod Chaniella pascuali n. gen. n. sp. is described from the lower Tremadocian Guayoc Chico Group of northwestern Argentina. Cladistic analysis shows that Chaniella is closest to the billingsellides Protambonites and Korinevskia. The particular combination of features of the new genus, in particular the presence of narrow lateral deltidial plates instead of a complete pseudodeltidium, led to the designation of the new monotypic family Chaniellidae. Parsimony analysis supports the separation of clitambonitidines and billingsellidines as monophyletic clades within the order Billingsellida and places the protorthide Arctohedra and the orthides Jivinella and Bohemiella close to the ancestry of the billingsellides.