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Paired pleural disks in Dicaulograptus cumdiscus n. sp.


A diplograptid graptolite with strongly introverted thecae and unusual thecal processes was isolated from limestones of the Ordovician Pratt Ferry Formation of Alabama and is described as a new species Dicaulograptus cumdiscus. The thecal processes are referred to as pleural disks. They occur in pairs above every thecal aperture and are inferred to have functioned as suspension processes receiving uplift from small‐scale turbulent water motion. Such a function is compatible with a passively buoyant mode of life and is difficult to reconcile with an automobile mode of life.


  1. Ordovician graptolites
  2. Dicaulograptus
  3. morphology
  4. mode of life

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Published In

Volume 18Number 41 October 1985
Pages: 361368


Received: 25 September 1984
Published online: 1 October 1985
Issue date: 1 October 1985



Stanley C. Finney
T. Boone Pickens. Jr. School of Geology, Oklahoma State University, Stillwater, Oklahoma, 74078, U.S.A.;

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  • Possible propulsion modes in Graptoloidea: a new model for graptoloid locomotion, Paleobiology.
  • The morphology and ultrastructure of Brevigraptus quadrithecatus n. gen., n. sp. (Diplograptacea), and Its convergence upon Dicaulograptus hystrix (Bulman) , Journal of Paleontology.
  • Palaeoecology of the Graptoloidea, Earth-Science Reviews.
  • Die Graptolithen des Ordoviziums von Rügen (Norddeutschland, Vorpommern), Paläontologische Zeitschrift.

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