''Tentaculites'' is an extinct genus of conical fossils of uncertain affinity, class

Tentaculita Tentaculita is an extinct class of uncertain placement ranging from the Early Ordovician to the Middle Jurassic. They were suspension feeders with a near worldwide distribution. For a more thorough discussion, see ''Tentaculites''. The presenc ...

, although it is not the only member of the class. It is known from Lower Ordovician to Upper Devonian deposits both as calcitic shells with a brachiopod-like microstructure and carbonaceous 'linings'. The "tentaculites" (i.e. tentaculita) are also referred to as the styliolinids.

Affinity

The taxonomic classification of tentaculitids is uncertain. Some grouped them with pteropods, but there is no modern support and only superficial similarity. They may also be related to other conical shells of uncertain affinity including

cornulitids Cornulitida is an extinct order of encrusting animals from class Tentaculita, which were common around the globe in the Ordovician to Devonian oceans, and survived until the Carboniferous. The organisms had shells, and were subject to predation ...

, ''

Anticalyptraea ''Anticalyptraea'' is a fossil genus of encrusting tentaculitoid tubeworms from the Silurian to Devonian of Europe and North America (Vinn, 2010). ''Anticalyptraea'' commonly encrust various invertebrate fossils such as stromatoporoids, rugose c ...

'',

microconchids The order Microconchida is a group of small, spirally-coiled, encrusting fossil "worm" tubes from the class Tentaculita found from the Upper Ordovician to the Middle Jurassic (Bathonian) around the world. They have lamellar calcitic shells, u ...

and trypanoporids. Their shell microstructure has warranted their comparison with the

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan 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 end, w ...

s and

phoronid Phoronids (scientific name Phoronida, sometimes called horseshoe worms) are a small phylum of marine animals that filter-feed with a lophophore (a "crown" of tentacles), and build upright tubes of chitin to support and protect their soft bodies. ...

s, and the possible Ediacaran lophophorate ''

Namacalathus ''Namacalathus'' is a problematic metazoan fossil occurring in the latest Ediacaran. The first, and only described species, ''N. hermanastes'', was first described in 2000 from the Nama Group of central and southern Namibia. A U–Pb zircon age ...

''.

Morphology

Tentaculitids have ribbed, cone-shaped shells which range in length from 5 to 20 mm. Some species septate; their embryonic shell, which is retained, forms a small, sometimes spherical, chamber.

Ecology

Some species are inferred to have been planktonic.

Affinity

Morphology

Ecology

See also

References

Further reading