Leymeriellidae Explained

Leymeriellidae is an extinct 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.^[1]

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.^[2]

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

References

• W.J. Kennedy et al. 1980. Albian and Cenomanian ammonites from the island of Bornholm (Denmark). Bull. geol. Soc. Denmark 29:203-244
• Leymeriellidae Paleobiology Database.

Notes and References

1. BERT, D. Les ammonites du niveau Paquier (Albien basal, Crétacé inférieur) du Sud-Est de la France. Fossiles, 2012, 12: 4-25.
2. Book: W.J. . Arkell . B. . Kummel . C.W. . Wright . Treatise on Invertebrate Paleontology, Part L, Mollusca 4. Mesozoic Ammonoidea . Geological Society of America and University of Kansas Press . Lawrence, Kansas. 1957.