''Misikella'' is an extinct genus of

conodont Conodonts, are an extinct group of marine jawless vertebrates belonging to the class Conodonta (from Ancient Greek κῶνος (''kōnos''), meaning " cone", and ὀδούς (''odoús''), meaning "tooth"). They are primarily known from their hard ...

s. Two species were named as type species for the genus in separate publications by the same authors in the same year (1974). The first paper named ''Misikella longidentata'', while the second named ''Misikella posthernsteini''. Most species assigned to ''Misikella'' have a Norian-Rhaetian distribution and a bimembrate conodont apparatus, including ''M. posthernsteini''. On the other hand, ''M. longidentata'' has a

Carnian The Carnian (less commonly, Karnian) is the lowermost stage (stratigraphy), stage of the Upper Triassic series (stratigraphy), Series (or earliest age (geology), age of the Late Triassic Epoch (reference date), Epoch). It lasted from 237 to 227.3 ...

-Norian distribution and a tetramembrate apparatus. Fåhræus & Ryley (1989) retained the name ''Misikella'' for only ''M. longidentata'', placing the rest of the species into the new genus ''Axiothea''. However, other conodont specialists utilize the name ''Misikella'' primarily in the context of ''M. posthernsteini'' and other bimembrate species, rather than ''M. longidentata''. Uniquely, ''M. posthernsteini'' is known from the Hettangian of Japan, suggesting that conodonts underwent extinction debt and then were outcompeted by other organisms.

Use in stratigraphy

The top of the

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

(the base of the

Rhaetian The Rhaetian is the latest age (geology), age of the Triassic period (geology), Period (in geochronology) or the uppermost stage (stratigraphy), stage of the Triassic system (stratigraphy), System (in chronostratigraphy). It was preceded by the N ...

, stages of the Upper Triassic) is close to the first appearance of several species of ''Misikella,'' as well as '' Epigondolella mosheri''. In 2010, the Norian-Rhaetian boundary was defined by the first appearance of ''Misikella posthernsteini''. The most often-discussed Rhaetian GSSP Candidate sections are in Steinbergkogel in Austria, or Pignola-Abriola in Italy.

References

* Conodonts of the genus Misikella Kozur and Mock, 1974 from the Rhaetian of the Tatra Mts (West Carpathians). A Gazdzicki, Acta Palaeontologica Polonica, 1978

External links

* * Conodont genera Triassic conodonts Norian genus first appearances Rhaetian genus extinctions {{conodont-stub