Tentaculites

Tentaculites is a genus of a problematic group of Paleozoic fossils called tentaculids. The shells of Tentaculites consist of conical tubes (5 to 20 mm long) that are  straight or slightly bent and have transverse rings (ribs) on the surface. The tubes are closed at the small pointed end and open at the opposite, larger end called the aperture. The three specimens shown above are incomplete Tentaculites sp. from the same locality in Devonian rocks of New York. The specimen on the left is 5.8 mm in length; the middle specimen is 6 mm in length; and the specimen on the right is 4 mm in length.

One of the interesting features of most shells of Tentaculites is the presence of chambers in the early stage of growth. A photomicrograph (i.e., taken through a microscope) of a cross-section of a Tentaculites shell, 7 mm in length, shows these chambers. Jasmyn Nolasco took the photomicrograph, and James Ingraffia facilitated the process.

This is a cluster of Tentaculites sp. from the Manlius Limestone of Devonian age near Ravenna, New York. The largest specimens are approximately 10 mm in length. 

Tentaculites ranged in geologic age from the Early Ordovician to the Late Devonian (see time diagram below) (a span of 128 million years).