Tentaculites

Tentaculites is an extinct genus of conical fossils of uncertain affinity, class Tentaculita, although it is not the only member of the class. It is known from Lower Ordovician to Upper Devonian deposits^[1] both as calcitic shells with a brachiopod-like microstructure^[2] and carbonaceous 'linings'.^[3][4] The "tentaculites" (i.e. tentaculita) are also referred to as the styliolinids.

Tentaculites Temporal range: Early Ordovician – Late Devonian[1] PreꞒ Ꞓ O S D C P T J K Pg N
Tentaculitids from the Devonian of Maryland.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Class:	†Tentaculita
Order:	†Tentaculitida
Family:	†Tentaculitidae
Genus:	†Tentaculites von Schlotheim, 1820
Species
T. bellulus Hall, 1876 T. exaltatus Talent, 1963 T. grandis Roemer, 1870 T. oswegoensis F.B. Meek & A.H. Worthen, 1865

Affinity

Tentaculites bellulus from the Middle Devonian of Wisconsin.

The taxonomic classification of tentaculitids is uncertain. Some grouped them with pteropods, but there is no modern support and only superficial similarity.^[who?][5] They may also be related to other conical shells of uncertain affinity including cornulitids, Anticalyptraea, microconchids and trypanoporids.^[6] Their shell microstructure has warranted their comparison with the brachiopods and phoronids,^[2][7] and the possible Ediacaran lophophorate Namacalathus.^[8]

Morphology

Sketch of a Tentaculites ornatus, Silurian.

Tentaculitid from the New Creek Limestone (Lochkovian, Early Devonian) of New Creek, West Virginia.

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.^[4]

Ecology

Some species are inferred to have been planktonic.^[9]

See also

• Mari Mari Group, fossil formation in the state of Amazonas of northwestern Brazil