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ABSTRACT
The fish described here is from the Madongshan Formation, Liupanshan group (Early Cretaceous), Tongxin County, Ningxia Autonomous Region, China. It is assigned to Osteoglossomorpha because it has the following synapomorphies of the superorder: a full neural spine on the first preural centrum, a primary bite between parasphenoid and basihyal, and absence of a supraorbital. This fish differs from other osteoglossomorphs in having a very short premaxilla with only three teeth, of which one is exceptionally large, and an unusual caudal skeletal in which hypural 1 is fused to the first ural centrum and hypural 2 remains autogenous. A new name is proposed, Xixiaichthys tongxinensis gen. et sp. nov., based on the unique characters and a combination of other characters. The results of the phylogenetic analysis show that Xixiaichthys is the sister group of the Osteoglossiformes ([[Notopterus + Osteoglossum] + [Huashia + Kuntulunia]]). Therefore, the new genus is referred to Osteoglossiformes.
