This piece is from a locomotive shove Tim Haye found about 30 years ago.
Lituites is an extinct nautiloid genus from the Middle Ordovician and type for the Lituitidae (a tarphyceratid family) that in some more recent taxonomies has been classified with the orthocerids and listed under the order Lituitida. Fossils have been found in New York, Argentina, Norway, Sweden, Estonia, and China.
Lituites produced a shell with a planospirally coiled juvenile portion at the apex, reflective of its tarphyceratid ancestry, followed by a long, moderately expanding, generally straight, orthoconic adult section with a subdorsal siphuncle connecting the chambers. The adult body chamber may equal or exceed the length of the chambered part of the orthoconic section. The mature aperture has a pair of pronounced ventrolateral lappets and a similar but shorter pair of dorsolateral lappets.
Lituites gives its name to the term "lituiticone" which refers to a shell that is coiled in the early growth stage and later becomes uncoiled. This is a particularly lovely specimen found by my friend Tim on a fossil field trip when he was just a young lad. I associate this nautiloid with the wee gnomes we set out over the winter holidays. Once you see it, you cannot unsee it. Enjoy!
References:
- Flower & Kummel, 1950. A Classification of the Nautiloidia. Jour Paleontology, V.24, N.5, pp 604–616, Sept
- Furnish & Glenister, 1964, Nautiloidea -Tarphycerida. Treatise on Invertebrate Paleontology Part K... Nautiloidea
- Mutvei, H. 2002. Connecting ring structure and its significance for classification of the orthoceratid cephalopods. Acta Palaeontologica Polonica 47 (1): 157–168.
No comments:
Post a Comment
Note: Only a member of this blog may post a comment.