Nautilida

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Explains Teichert (1988):
Explains Teichert (1988):
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:The Nautilida exhibit an infinite variety in degrees of coiling (with no deviations from the planispiral model), whorl cross sections, and surface ornamentations, but no overall trends in any of these features. [[Suture]]s were straight or only weakly undulating in almost all genera, with the exception of a few that developed in the [[Carboniferous]] among the [[Trigonoceratidae]], in the Late [[Triassic]] in the [[Clydonautilidae]], [[Gonionautilidae]], and [[Siberionautilidae]], and during the Late [[Cretaceous]] and Early [[Tertiary]] among the [[Hercoglossidae]] and [[Aturiidae]], all of which have sutures similar to those of certain Upper Devonian [[Goniatitida|goniatite]] genera. Characteristically, [[siphuncle]]s are [[orthochoanitic]] and anywhere from subventral to subdorsal in position. Only few forms have marginal siphuncles, with those of the Late Paleozoic Aipocerataceae and of Triassic ''[[Menuthlonautilus]]'' being ventral and that of Early Tertiary ''[[Aturia]]'' being dorsal in position.
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:The Nautilida exhibit an infinite variety in degrees of coiling (with no deviations from the planispiral model), whorl cross sections, and surface ornamentations, but no overall trends in any of these features. Sutures were straight or only weakly undulating in almost all genera, with the exception of a few that developed in the [[Carboniferous]] among the Trigonoceratidae, in the Late [[Triassic]] in the Clydonautilidae, Gonionautilidae, and Siberionautilidae, and during the Late [[Cretaceous]] and Early [[Tertiary]] among the Hercoglossidae and Aturiidae, all of which have sutures similar to those of certain Upper Devonian [[Goniatitida|goniatite]] genera. Characteristically, [[siphuncle]]s are orthochoanitic and anywhere from subventral to subdorsal in position. Only few forms have marginal siphuncles, with those of the Late Paleozoic Aipocerataceae and of Triassic ''[[Menuthlonautilus]]'' being ventral and that of Early Tertiary ''[[Aturia]]'' being dorsal in position.
==Phylogenetic Relationships==
==Phylogenetic Relationships==

Revision as of 13:20, 14 December 2009

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