''Tannuolina'' is a genus of

tommotiid Tommotiids are an extinct group of Cambrian invertebrates thought to be early total-group lophophorates (the group containing Bryozoa, Brachiopoda, and Phoronida), including members of the lophophorate stem group, as well as early diverging mem ...

, belonging to the

brachiopod Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear e ...

stem lineage. Its

phosphatic Phosphates are the naturally occurring form of the element phosphorus. In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphor ...

shells exhibit a complex series of open pores/chambers/channels in outer shell layer.Kouchinsky, A., Bengtson, S. & Murdock, D. J. E. A new tannuolinid problematic from the lower Cambrian of the Sukharikha River in northern Siberia. Acta Pal. Pol. 55, 321–331 (2010). It is conventionally interpreted as an essentially

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

d organism, similar to ''

Micrina ''Micrina'' is an extinct genus of tommotiids with affinities to brachiopods. ''Micrina'' can be considered a stem group brachiopod based on its larval shell. Its microstructure is very brachiopod like and its adult morphology is similarly biv ...

'', though some use the unequal ratio of stellate to

mitrate Mitrates are an extinct group of stem group echinoderms, which may be closely related to the hemichordates. Along with the cornutes, they form one half of the Stylophora. Morphology The organisms were a few millimetres long. Like the echinod ...

sclerites A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

to argue for a

halkieriid The halkieriids are a group of fossil organisms from the Lower to Middle Cambrian. Their eponymous genus is ''Halkieria'' , which has been found on almost every continent in Lower to Mid Cambrian deposits, forming a large component of the smal ...

-like anatomy.Li, G.-X. & Xiao, S.-H. ''Tannuolina'' and ''Micrina'' (Tannuolinidae) from the Lower Cambrian of Eastern Yunnan, South China, and Their Scleritome Reconstruction. J. Paleontol. 78(5), 900–913 (2004). More recently a tube-like construction inspired by ''

Eccentrotheca ''Eccentrotheca'' is a genus of "tommotiid" known from Cambrian deposits. Its sclerites form rings that are stacked to produce a widening-upwards conical scleritome. Individual plates have been homologized with the valves of brachiopods, and a ...

'' has been proposed.Skovsted, C. B., S. Clausen, J. J. Álvaro, and D. Ponlevé. 2014: Tommotiids from the early Cambrian (Series 2, Stage 3) of Morocco and the evolution of the tannuolinid scleritome and setigerous shell structures in stem group brachiopods. Palaeontology 57:171–192.

Species

* ''T. fonini'' Esakova ''in'' Esakova & Zhegallo, 1996 * ''T. maroccana'' Skovsted & Clausen ''in'' Skovsted, Clausen, Álvaro & Ponlevé, 2014 * ''T. multifora'' Fonin & Smirnova, 1967 * ''T. pavlovi'' Kouchinsky ''et al.'', 2010 * ''T. zhangwentangi'' Qian & Bengtson, 1989

References

Cambrian brachiopods Prehistoric brachiopod genera Cambrian genus extinctions {{cambrian-animal-stub