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Book Chapter

Part IV.—Distribution: Aglaspid Chronology

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Published:
January 01, 1939

The arrangement of the aglaspid species in the chronological order of their stratigraphic occurrence brings out the prominence of the group in late Cambrian time and emphasizes the limited time span of known aglaspid occurrence. Both chronologically and morphologically a wide gap separates the Aglaspida from their dependent Xiphosura, Synxiphosure, and Eurypterida, while the aglaspid forebears remain to be discovered.

UPPER CAMBRIAN

Trempealeau formation

  Jordan member

    Aglaspis sp.

  Lodi member

    Aglaspis barrandei Hall

    A. spinifer nov.

    A. simplex nov.

    Aglaspella granulifera nov.

    A. eatoni (Whitfield)

    Glypharthrus thomasi (Walter)

    Aglaspoides sculptilis nov.

    A. semicircularis nov.

    U-arlhrus instdbilis nov.

    Cyclopina vulgaris nov.

    Chraspedops modesta nov.

    C. fragilis nov.

    Setaspis spinulosus nov.

    S. regularis nov.

  St. Lawrence member

    Aglaspis dorsetensis nov.

    Aglaspella eatoni (Whitfield)

    Cyclopina sp.

Franconia formation

  Bad Axe member (and equivalent strata in Montana)

    Cyclopina sp.

    Aglaspis near franconensis nov.

    Aglaspella cf. eatoni (Whitfield)

  Hudson member

    Aglaspis franconensis nov.

    Undetermined smooth aglaspids

  Goodenough member

    Undetermined aglaspids

  Ironton member (and equivalent strata in Missouri and South Dakota)

    Glypharthrus vulpes nov.

    G. deadwoodensis nov.

    Aglaspoides ? sp. nov.

    Strabops thacheri Beecher

  Dresbach formation

    Crepicephalus zone

      Beckwithia ? major (Graham)

    Cedaria zone

      Beckwithia ? major (Graham)

MIDDLE CAMBRIAN

Marjum formation (highest Middle Cambrian) (from Utah)

  Beckwithia typa Resser

STRATIGRAPHIC OCCURRENCE AND HABITAT

GENERAL CONSIDERATION

The limited stratigraphic range of the Aglaspida (late Middle Cambrian to late Upper Cambrian) is in marked contrast to that of the Xiphosura (Upper Devonian to Recent), more restricted than that of the Eurypterida (Ordovician to Pennsylvanian), and . . .

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Contents

GSA Special Papers

Cambrian Merostomata

Gilbert O. Raasch
Gilbert O. Raasch
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Geological Society of America
Volume
19
ISBN print:
9780813720197
Publication date:
January 01, 1939

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