Leymeriellidae
Leymeriellidae is a family of Lower Cretaceous ammonites comprising rather small forms distinguished from Hoplitidae by their flattened and grooved ribs and virtual absence of umbilical tubercles. The family is derived from the Desmoceratidae. "Leymeriella schrammeni anterior" has evolved from "Desmoceras keilhacki keilhacki". Taxonomic position. Leymeriellidae are currently regarded is belonging to the Acanthoceratoidea according to W. J. Kennedy "et al" (1980). The previous placement was in the Hoplitoidea according to W.J. Arkell "et al" (1957) in the "Treatise on Invertebrate Paleontology, Part L". Genera. Leymeriellidae includes the following genera: "Leymeriella" Jacob 1907. Shell evolute, venter flat to sulcate . Ribs single, wide spaced, grooved in outer part. "Lower Albian to Middle Albian" "Proleymeriella" Breistroffer 1947. Shell moderately evolute, whorl section oval with constrictions present throughout. Ribs single, strong, form chevrons on a narrowly rounded to acute venter. "Lower Albian" "Epileymeriella" Breistroffer 1947. Differs from "Leymeriella" in that the ribs branch from weak umbilical bullae. "Lower Albian"