The Valcouroceratidae is a family within the Oncocerida

Oncocerida

The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian ,in which the connecting rings are thin and siphuncle segments are variably expanded...

, nautiloid cephalopods from the middle and upper Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

, established by Rousseau Flower

Rousseau H. Flower

Rousseau Hayner Flower was an extremely prolific 20th century paleontologist, known for his eccentric personality.- Career :Although trained as an entomologist, and a specialist in dragonflies and orthopterans, Flower began studying paleontology in the middle of the 1930s...

 in 1945.

Diagnosis

Valcouroceratids are characterized by exogastric cyrtocones and brevicones that change during the life span from compressed to depressed or subtriangular in cross section, and which have ventral siphuncle

Siphuncle

The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and Spirula...

s that are cyrtochoanitic and which contain lammelar actinosiphonate fillings. The actinosiphonate fillings, commonly referred to as deposits, are radially inward projections of the connecting rings that extend logitudinally along the inner wall of the siphuncle and project forward as blades into the siphuncle interior from the septal foremina.(Sweet 1964, Flower 1950)

Distribution

Most valcouroceratids come from North America but Valcouroceras has been found in northern Europe (Norway) as well. (Sweet 1964)

Genera

The Valcouroceratidae includes 8 genera:

• Valcouroceras
• Actinomorpha
• Augustoceras
• Fayettoceras
• Kindeloceras
• Manitoulinceras
• Minganoceras
• Staufferoceras