Balticeras
Encyclopedia
Balticeras is an involute, discoidal Upper Jurassic (Oxfordian) ammonite (order Ammonitida
) found in England, Germany, and Switzerland, belonging to the Perisphinctidae
. The shell is strongly embracing, tending to be oxyconic (sharp rimmed). Sides are gently curved, converging on a narrow to sharp ventral rim.
Balticeras is considered by some to be a subgenus of Ringsteadia which in contrast is more evolute, with ribbed inner whorls. Both are included in the Pictoniinae, a subfamily established by Spath, 1924, for large ammonites within the Perisphinctidae, tending to develop smooth middle and outer whorls.
Ammonitida
The Ammonitida is an order of more highly evolved ammonoid cephalopods from the Jurassic and Cretaceous time periods, commonly with intricate ammonitic sutures....
) found in England, Germany, and Switzerland, belonging to the Perisphinctidae
Perisphinctidae
Perisphinctidae is a family of Middle and Upper Jurassic discoidal ammonites in the order Ammonitida. They have a shell morphology that is mostly evolute, typically with biplicate, simple, or triplicate ribbing...
. The shell is strongly embracing, tending to be oxyconic (sharp rimmed). Sides are gently curved, converging on a narrow to sharp ventral rim.
Balticeras is considered by some to be a subgenus of Ringsteadia which in contrast is more evolute, with ribbed inner whorls. Both are included in the Pictoniinae, a subfamily established by Spath, 1924, for large ammonites within the Perisphinctidae, tending to develop smooth middle and outer whorls.
References
- Arkell, et al, 1957. Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L (Ammonoidea). Geol. Soc. of America and Univ. Kansas Press.