Hildoceratoidea

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.^[3]

Hildoceratoidea Temporal range: Early—Middle Jurassic, Pliensbachian–Bajocian PreꞒ Ꞓ O S D C P T J K Pg N
Harpoceras exaratum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Ammonoidea
Order:	†Ammonitida
Suborder:	†Ammonitina
Superfamily:	†Hildoceratoidea Hyatt, 1867
Families[1]
Erycitidae[2] Hildoceratidae Hammatoceratidae Graphoceratidae Sonniniidae

Hildoceratoidea is an upper Lower to lower Middle Jurassic group belonging to the Ammonitina that unites the Hildoceratidae, Hammatoceratidae, Graphoceratidae, and Sonniniidae.^[3] In some taxonomies the name Phymatoceratidae is substituted for the Hammatoceratidae^[4]

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.^[3]

Approximate timeline of Hildoceratoidea families with their evolutionary relationships.