| 词条 | Valcourocratidae |
| 释义 |
| fossil_range = M-U Ordovician | image = | taxon = Valcouroceratidae | authority = Flower (1945) | subdivision_ranks = Genera | subdivision = See text }} The Valcouroceratidae is a family within the Oncocerida, nautiloid cephalopods from the middle and upper Ordovician, established by Rousseau Flower in 1945. DiagnosisValcouroceratids 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 siphuncles 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 longitudinally along the inner wall of the siphuncle and project forward as blades into the siphuncle interior from the septal foremina.(Sweet 1964, Flower 1950) DistributionMost valcouroceratids come from North America but Valcouroceras has been found in northern Europe (Norway) as well. (Sweet 1964) GeneraThe Valcouroceratidae includes 8 genera:
References
5 : Prehistoric nautiloid families|Ordovician cephalopods|Middle Ordovician first appearances|Late Ordovician extinctions|Taxa named by Rousseau H. Flower |
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