''Schloenbachia'' is a genus of

ammonoid Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

cephalopods from the

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

stage of the Upper

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

, and type for the Schloenbachiidae, a family within the ammonitid

Hoplitoidea Hoplitoidea, formerly Hoplitaceae, is a superfamily of mostly Upper Cretaceous ammonites comprising families united by a similar suture pattern with multiple similar elements that tend to decrease in size going toward the umbi ...

.Arkell ''et al.'', Mesozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part L, 1957. ''Schloenbachia'' was named by Newmayer, 1875, the type species is Schloenbachia varians (Sowerby 1817). The genus has been found in Europe (France, Germany, England), the Middle East (Iran), and North America (California, Oregon).

Species

''Schloenbachia varians''

''Schloenbachia varians'', known from Europe and Iran, is a highly varied species with a number of possible synonyms. Variations include ''S. varians'' (var) ''subvarinas'', ''S.v''. (var) ''subtuberculata'', ''S.v''. (var) ''ventricosa'', and ''S.v''. (var) ''varians''. ''Schloenbachia varians'' comprises a highly variable group of medium-sized, involute and compressed to evolute and highly inflated, weak to strongly keeled ammonites, most all of which bear umbilical and lower lateral tubercles. Compressed forms may be smooth and constricted. More inflated forms usually have flexuous ribs that arise from lower lateral tubercles ending in strong clavi at the ventrolateral ends. The variations included cannot be regarded as geographic subspecies or successive chrono-subspecies, but reflect a high degree of variability in shell form and ornament (phenotypic plasticity) in ''S. varians''.

''Schloenbachia'' in western North America

A suite of species attributed to ''Schloenbachia'' have been described from Upper Cretaceous sediments in California and Oregon (Chico Formation and equivalents), including among others ''Schloenbachia chicoensis'', ''S. knighteni'', ''S. multicostata'', ''S. oregonensis'', and ''S. siskiyouensis''. These differ in the nature of the ribbing, tuberculation, and keel as well as the degree of compression or inflation of the shell. Most come from northern California and Oregon, however two species ''Schloenbachia knighteni'' and ''Schloenbachia siskiyouensis'' have been found in the coastal mountains in southern California east of Santa Anna.Silverado Canyon Natural area
/ref>

References

Hoplitoidea Ammonitida genera Cretaceous ammonites Ammonites of Europe {{Ammonitina-stub