Arthropod Body Fossil - Probable Protichnites Track Maker

(Euthycarcinoid or Aglaspid)

Protichnites trackway maker

Body Fossil (cast) of putative euthycarcinoid or aglaspid

Geologic Time: Upper Cambrian

Size (25.4mm=1 inch): Matrix: 350 by 225 mm, Arthropd length 150 mm

Location: Krukowski Quarry, Mount Simon Sandstone Outlier, Mosinee,Wisconsin

Protichnites Track MakerSeveral hypotheses exist regarding what animal (or animals) made the tracks (Ichnofossils) of Protichnites. Protichnites is distinguished by prominent markings of a tail or other body part being dragged and footprints, not always present, that are subtle by comparison. Past speculation was that the tracks were made by horseshoe crabs or Eurypterids, or earlier and related stem groups. More recently, however, fossils such as this from the Elk Mound Group suggest that the Protichnites (and probably also the Diplichnites) trackways of the late Cambrian and early Ordovician were made by a member of one of two enigmatic groups of Arthropods, the Conjectured Protichnites Body Fossileuthycarcinoids or the aglaspids. If so, those in the Krukowski quarry may be the oldest occurrence in the fossil record of animal footprints on land.

The pictures shown here are of the largest (almost 6 inches) of these rare fossils that have been found so far in the quarry. Its resemblance to the impression we might expect from either a euthycarcinoid, aglaspid, horseshoe crab or Eurypterid is apparent. If you study the pictures you will note traverse lines that are possibly the evidence of a segmented body structure.

These probable Protichnites (and Diplichnites) trackmaker fossils were discovered in 2003. At six inches in length, this is the largest of all of them.

See also: Cambrian Shawdows main page

Click pix to enlarge

Additional Pictures

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