Clymeniida

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Clymeniida
Temporal range: Upper Devonian
Clymenia laevigata.JPG
Clymenia laevigata
Scientific classification e
Kingdom: Animalia
Phylum: Mollusca
Class: Cephalopoda
Subclass: Ammonoidea
Order: Clymeniida
Hyatt, 1884
Suborders

The Clymeniida constitute a unique order of ammonoid cephalods from the Upper Devonian characterized by having an unusual dorsal siphuncle. They measured about 4 cm in diameter and are restricted to Europe, North Africa, and possibly Australia.

Morphologic characteristics[edit]

Clymeniids produced a variety of shells ranging from smooth to ribbed and spinose and from evolute with all whorls exposed to strongly involute with the last whorl covering the previous. Some were even triangular as viewed from the side (along the axis of coiling). With the exception of the first few chambers, all have a siphuncle that runs along the dorsal margin, along the inside of the coils, opposite that of most ammonoids.

The siphuncle starts off ventrally, like that in other ammonoids, but after the first few septa migrates to a definite and stable dorsal position. Septal necks are retrosiphonate, characteristic of their nautlloid ancestors, and are commonly very long, forming an almost continuous siphunclular tube. Septa, characteristic of ammonoids, are convex toward the front.

Classification[edit]

Miller, Furnish, and Schindewolf, 1957, in Part L of the Treatise [1] included three superfamilies in the Clymeniida, the Gonioclymeniaceae, Clymeniaceae, and Parawocklumeriaceae. The Gonoclymeniaceae unites five families, the Clymeniaceae three. The Parawocklumeraceae was established for a single family, the Parawocklumeriidae.

Saunders, Work, and Nikoleava, 1999,[2] divided the Clymeniida into two suborders, the Gonioclymeniina and the Clymeniina. The Gonioclymeniina includes the Sellaclymeniaceae with 7 families and 20 genera, the Gonioclyemniacea, containing a single family with six genera, and the Parawocklumeraceae, also containing a single family, but with only three genera. The Clymeniina combines five families with a total of 36 genera into a single superfamily, the Clymeniaceae.

GONIAT Website [3] gives two suborders which fall into the Clymeniida. They are the Clymeniina with four superfamilies and Gonioclymeniina, established for a single superfamily. In contrast, Dieter Korn, 2006 divided the Clymeniida into the Clymeniina with superfamilies and families, and Cyrtoclymenia, named by him in 2002. with superfamilies and families.[4] Shevyrev, 2006 on the other hand divided the Clymeniida into the Clymeniina and Gonioclymeniina, as with GONIAT and Saunders, Work, and Nikolaeva [5]

Taxonomy[edit]

Clymeniida

References[edit]

  1. ^ Miller, Furnish, and Schindewolf, 1957; Paleozoic Ammonoidea; Treatise on Invertebrate Paleontology, Part-L, Ammonoidea, Geological Society of America & Univ of Kansas.
  2. ^ Evolution of Complexity in Paleozoic Ammonoid Sutures; Supplementary Materia [1]
  3. ^ GONIAT
  4. ^ D. Korn. 2006. Paleozoic ammonoid classification
  5. ^ Classification of A. A. Shevyrev 2006