Hildoceratoidea, formerly Hildoceratacaea, is a superfamily of compressed or planulate ammonites, some tending to develop acute outer rims; generally with arcuate or sigmoidal ribs. Aptichus were found in place are double-valved.[1]
Hildoceratoidea is an upper Lower to lower Middle Jurassic group belonging to the Ammonitina that unites the Hildoceratidae, Hammatoceratidae, Graphoceratidae, and Sonniniidae.[1] In some taxonomies the name Phymatoceratidae is substituted for the Hammatoceratidae[2]
Hildoceratidae, which is the ancestral family, is derived from the Acanthopleuroceratinae, a subfamily in the Eoderoceratoidean family, Polyorphitidae. The Stephanoceratoidea, Perisphinctoidea, and Haploceratoidea have their source in the Hammatoceratidae which is derived from the Hildoceratidae.[1]