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 both as calcitic shells with a brachiopod-like microstructure and carbonaceous 'linings'.Wood, G.D., Miller, M.A., and Bergstrom, S.M. 2004. Late Devonian (Frasnian) tentaculite organic remains in palynological preparations, Radom−Lublin region, Poland. Memoirs of the Association of Australian Palaeontologists 29: 253–258.
Affinity The taxonomic classification of tentaculitids is uncertain. Some grouped them with pteropods, but there is no modern support and only superficial similarity.Ager, 1963, Principles of Palaeontology They may also be related to other conical shells of uncertain affinity including cornulitids, Anticalyptraea, microconchids and trypanoporids. Their shell microstructure has warranted their comparison with the brachiopods and phoronids, and the possible Ediacaran lophophorate Namacalathus.1. Zhuravlev, A.Y., Wood, R.A., and Penny, A.M. (2015). Ediacaran skeletal metazoan interpreted as a lophophorate. Proc. R. Soc. B 282, 20151860. Available at: http://rspb.royalsocietypublishing.org/lookup/doi/10.1098/rspb.2015.1860.
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.
See also Mari Mari Group, fossil formation in the state of Amazonas of northwestern Brazil
References
Further reading
Treatise on Invertebrate Paleontology, Part W - Miscellanea. Geological Society of America and University of Kansas Press, 1962. LCCN 53012913