Some early actinocerids

Here are holotypes of three actinocerids (order Actinocerida) housed at the New Mexico Museum of Natural History and Science in Albquerque, N.M. They all belong to the Wutinoceratidae, which is an early actinocerid family and all three come from the Pallisaria zone in the Antelope Valley Limestone near Beatty, Nevada. They are, with museum catalogue numbers:

Adamsoceras leonardi P-42779
Cyrtonybyoceras adamsi P-42976
Wutinoceras huygenae P- 42877




All three are from the Whiterock stage at the beginning of the Middle Ordovician. Wutinoceras is considered the ancestral form, which gave rise to the other two, as well as to the Armenoceratidae and Actinoceratidae. Adamsoceras is thought to have given rise to the Ormoceratiae. Cyrtonybyoceras apparently left no descendants.

What about Barrandeocerida

Flower, in Flower and Kummel, in A Classiification of the Nautiloidea, Journal of Paleontology Sept 1950, estalished the Barrandeocerida as a separate order, derived from the Tarphycerida. Barrandeocerids first appear in the Middle Ordovician, later than the Tarphycerida which first appear in the Lower Ordovician. Moreover Barrandeocerids have derived (evolved) characters, the principal one being thin connecting rings. So it makes, or made, sense to separate the two on an equal basis.

As recently as 1976, Flower in his paper of Ordovician Cephalopod Faunas, published by the Palaeontological Society ( Gr Br) separated the Barradeocerida from the Tarphycerida, deriving the former from the latter. This changed in 1984.

Flower, in Bodeiceras; a New Mohawkina Oxycone; ... Journal of Paleontology Nov. 1984, showed that the first two families of the Barrandeocerida, the Barradeoceratidae and Plectoceratidae are derived from different genera in the Tarphyceratidae, making the Barrandeocerida polyphyletic and therefore invalid, which according to Flower, should be abolished. Families that were included in the Barrandeocerida now belong in the Tarphycerida, which as a result has become greatly expanded. However Teichert, 1988, in has review paper on Main Features of Cephalopod Evolution in The Mollusca Vol 12, Academic Press, retained the Barrandeocerida as a distiinct group, but as a suborder of the Tarphycerida, the Barrandeocerina. The other suborder of course being the Tarphycerina.

Flower's claim that the Barrandeoceratidae are derived from Centrotarphyceras and that the Plectoceratidae are derived from Campbelloceras is not stated with clear evidence, but is left for the reader to simply accept, or reject. For this reason the claim that the Barrandeocerida (sensu Flower 1950) is polyphyletic can not be taken as an absolute. It is obvious however that barrandeocerids form a group that evolved from earlier tarphycerids and might just as well be included as a suborder pending further evidence of separate origins for the Barradeoceratidae and Plectoceratidae.

No more Basslerocerida

The late Rousseau Flower in Flower and Kummel, 1950, in the Journal of Paleontology, Sept 1950 set up the Bassleroceratida as an order of nautiloid cephalopods intermediary between the more primitive, generally straight shelled Ellesmerocerida and the more evolved, coiled Tarphycerida and later Barrandeocerida. Basslerocerids are exemplified by the upwardly curved genus Bassleroceras in which the lower or ventral side is longitudinally convex and the upper or dosal side is curved in the opposite sense. The order at that time included two families, the Bassleroceratidae and Graciloceratidae.

Seven years later, Flower 1957 in Flower and Teichert, in a University of Kansas publication on the Discosorida, abandoned the Bassleroceratida and instead included the Bassleroceratidae, with thick connecting rings in the Tarphycerida and the Graciloceratidae with thin connecting rings in the Oncocerida.

Taking a somewhat difference approach, W.M, Furnish and Brian Glenister in the original, 1964 edition of Part K of the Treatise on Invertebrate Paleontology, included the Bassleroceratidae in the ancestral Ellesmerocerida . Walter Sweet on the otherhand followed Flower's perspective and retained the Graciloceratidae in the Oncocerida. Later, Flower, 1976, in a publication of the Palaeontological Society ( Gr Br) on Ordovician Cephalopod Faunas, shows the Bassleroceratidae in the Tarphyceratida (same as Tarphycerida), with the earlier more primitive forms giving rise to the Tarphyceratidae and the more derived forms later giving rise to the Oncocerida following his original (1957) idea.

So, to conclude, no more Basslerocerida. The order should be regarded as unnecessary, more so than "invalid". Never-the-less Shevyrev, 2006, according to the Paleobiology Database website, retained the Basslerocerida as a distinct nautiloid order, with the Barrandeocerina its sole suborder. This follows neither the sense of Flower (1950, 1957, and 1976), of the Treatise Part K, 1964, Teichert et al, or of Teichert 1988. For one thing the Barrandeocerina ( ex Barrandeocerida) are clearly derived from the Tarphyceratidae and therefore cannot be part of the Basslerocerida, regardless. Since what is presented on line is not necessarily what is in the original, perhaps Basslerocerida should really be Barandeoceida, which makes more sense.