Lower Cretaceous ammonites from the Neuquen Basin, Argentina: the Hauterivian neocomitid genus Hoplitocrioceras (Giovine, 1950)

Hoplitocrioceras is a poorly-known ammonite genus of late Early Hauterivian age that may be endemic to the Neuquen Basin, Argentina, where it occurs a t a clearly defined horizon in the Agrio Formation. It is an unusual genus with uncoiling (crioceratitid) whorls that remain linked by a thick dorsal shell that drapes over the tips of sharp, upwardly-pointing ventro-lateral spines. It has been interpreted as either a necomitid or a crioceratitid, b ut is here regarded as one of the last members of the Family Neocomitidae. One new species is proposed: H. giovinei. (C) 2001 Academic Press.