Nessariostoma

Nessariostoma granulosum is a lightly armored pseudopetalichthyid placoderm from the Hunsrückschiefer Lagerstätte of Early Devonian Germany. The type and only known specimen is an articulated, but very incomplete individual, deformed and elongated, consisting of a large, incomplete, tubercle-covered head, a long, beak-like rostrum, and some of the trunk, with a total length of 18 centimeters. "N. granulosum" was once placed in Stensioellida, though most other experts regard it at as a pseudopetalichthyid: Denison 1978 regards it as a placoderm "incertae sedis" because the specimen is deformed and so poorly preserved so as to stymie proper attempts at classification.