Chidleyenoceras
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| Chidleyenoceras Temporal range: Middle Ordovician | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Nautiloidea |
| Order: | †Tarphycerida |
| Family: | †Plectoceratidae |
| Genus: | †Chidleyenoceras Shimizu & Obata, 1935 |
Chidleyenoceras is a Middle Ordovician tarphyceroid with a closely coiled, evolute shell; whorl section subquadrate, widest just above a broadly rounded venter; dorsum with a broad shallow impression; sutures moderately spaced, weakly sinuous; siphuncle large, subventral, apparently orthochoantitic[clarification needed] with tubular segments.
The tubular, subventral siphuncle separates Chidleyenoceras from the Apsidoceratidae (Sweet, 1964) where it had been included and puts it well into the Plectoceratidae (Flower, 1984).