Tarphyceratida

Tarphyceratida is an extinct order of cephalopods that lived during the Devonian period. These marine mollusks are characterized by their coiled shells, which were typically planispiral, meaning they were coiled in a single plane. The shell aperture was often contracted, and the siphuncle, a tube connecting the camerae (chambers) of the shell, was typically located ventrally. Tarphyceratids belonged to the subclass Nautiloida, which also includes modern nautiluses.

Fossils of Tarphyceratida are found in marine sedimentary rocks from the Devonian. They were likely nektonic swimmers, using their shells for buoyancy. The exact diet and lifestyle of these cephalopods are not fully understood, but it is presumed they were predators, like other cephalopods. The taxonomic placement of Tarphyceratida has been subject to debate among paleontologists, with some classifying it as a distinct order and others considering it a suborder within the Nautilida.

The shells of tarphyceratids are often found as fossils, providing valuable insights into the morphology and diversity of Devonian marine life. Their planispiral coiling is a notable feature, distinguishing them from some other nautiloids. The presence of a ventral siphuncle is another key characteristic used in their identification. While the group is extinct, its study contributes to our understanding of cephalopod evolution.