Phylum: Mollusca
Class: Tentaculida
Family: Tentaculitidae
Genus: Tentaculites von Schlotheim, 1820
Cincinnatian Species: Tentaculites richmondensis, Tentaculites sterlingensis

Geologic Range
Late Ordovician – Late Devonian

Common Paleoecology
Tentaculites is an extinct genus of facultatively mobile semi-infaunal suspension feeders

Identification in Hand Sample:

  • Thick and heavy conch
  • 15-30 mm in length
  • Inter-ring area usually with transverse ringlets or striae noticeably developed only in adult region
  • Conical embryonic section, can be hollow or solid

Geographic Occurrences

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Fossils of Ohio (1996):

  • Tentaculites is included in the order Tentaculitida, which along with the order Dacryoconarida belong to the class Tentauclitoidea. Hence, the proper designation for representatives of this class is tentaculitoids. The mode of life of tentaculitoids remains a matter of speculation. Species that have a fairly thick and heavy conch, such as Tentaculites scalariformis, are likely to have been benthic, but whether the conch was resting more or less horizontally or was orientated vertically is not known. The idea that these forms were benthic is supported by the fact that such species tend to have limited geographic range. Species that have thin-walled and light conches, such as representatives of Styliolina, have in many cases a wide geographic range and occur in black shales and other sediments deposited in environments in which bottom conditions were hostile to animal life. Such species are likely to have been planktic or nektic.

Treatise on Invertebrate Paleontology, Part W, Volume 1, (1962):

  • Medium sized (15 -30 mm) cone, exterior with coarse transverse rings which are less uniform in spacing towards aperture; inter-ring area usually with transverse ringlets or striae noticeably developed only in adult region. Embryonic portion conical, hollow or solid. Growth angle, 7-12 degrees in juvenile portion, 3 to 7 degrees in mature portion.


  • The shell of Tentaculites, as in well known, has the form of a straight conical tube, tapering towards one extremity to a pointed closed apex, and expanding toward the other to a
    rounded aperture. The walls of the shell are thin, and are surrounded with numerous thickened rings or annulations, sometimes with intermediate striae, over the whole part of the length of the tube.
  • No specimen of TentacuWes has ever been found attached to any foreign body; and though this of itself would not be fatal to the view that the genus belongs to the Tubicola, the mode of occurrence of the fossil completely negatives this supposition. Thus, Tentaculites are usually found in great numbers together, often over large areas, confusedly scattered over the surfaces of the laminae of deposition. If we have to deal with a tubicolar annelide, it seems certain that specimens would be found embedded vertically in the rock, with the closed apex downwards, and the aperture directed upwards, or else we should find them attached by their smaller extremities to shells and other foreign objects.

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Tentaculites richmondensis