Dead in Their Tracks--Cambrian Arthropods and Their Traces From Intertidal Sandstones of Quebec and Wisconsin

Abstract

The large euthycarcinoid arthropod Mictomerus melochevillensis from the middle Cambrian-Furongian Potsdam Group of Quebec occurs as threedimensional casts at the end of Cruziana-and Didymaulichus-like trace fossils. This association provides a rare opportunity to test functional morphological hypotheses about these animals, it provides a framework for understanding how arthropods can be sand-cast in three dimensions, and it suggests that euthycarcinoids may have burrowed into mud as an antidesiccation strategy. In the coeval Elk Mound Group of Wisconsin, the phyllocarid arthropod Arenosicaris inflata occurs on the same beds as Cruziana-like and Rusophycus traces; together with morphologically similar ropelike traces, they are interpreted as having been produced by phyllocarids. These traces preserve the earliest known ethological evidence of phyllocarid crustaceans, and imply that Cambrian phyllocarids employed antidesiccation and possibly feeding strategies still used by modern intertidal leptostracan phyllocarids.

COMMENT: MARINE INFLUENCE IN THE UPPER ORDOVICIAN JUNIATA FORMATION (POTTERS MILLS, PENNSYLVANIA): IMPLICATIONS FOR THE HISTORY OF LIFE ON LAND: PALAIOS, v. 25, no. 8, p. 527-539, 2010

“…' Davies et al (2010) also failed to note other trackways from the Juniata Formation recorded by Diecchio and Hall (1998). Terrestrial arthropod trackways of Ordovician and Cambrian age were initially controversial, but are now accepted (Retallack, 2009a;Collette et al, 2010). So the argument for marine paleoenvironment comes down to non-repichnial trace fossils of the Juniata Formation, presented by Davies et al (2010) in an unsystematic account, and illustrated with field photographs of indeterminate specimens.…”

“…Wilson (2006) and Shear and Edgecombe (2010) confirm trackways from the Lake District of England as evidence of Middle Ordovician (Darriwilian) myriapods, though of a type (Polyxenida or Arthropleurida) unlikely to have made the Potters Mills burrows. Other Cambrian and Ordovician subaerial trackways are attributed to creatures other than myriapods, especially euthycarcinoids (Retallack, 2009a;Collette et al, 2010). Davies et al (2010, p. 528) are correct that the maker of the Potters Mills burrows, like many trace makers, remains hypothetical.…”

Burrowing trilobite caught in the act

“…Findings of trace fossils and their unequivocal producers are generally rare in the fossil record (e.g., Osgood 1970;Mikuláš 1990;Fortey and Seilacher 1997;Cherns et al 2006;English and Babcock 2007;Collette et al 2010;Knaust 2010). Such a rarity is owing to differences in the preservation potential of the trace and its tracemaker, combined with the fact that carcasses could be transported, while trackways are usually preserved in situ.…”

“…They re-defined mortichnia as ''… associations where an animal died atop, in, or at the end of its trace fossil,'' while the term close associations was adopted from Fortey and Seilacher (1997) as samples ''… where a trackway is linked with a particular organism, but where an animal is not preserved at the end of, in, or atop its trace.'' Comparable mortichnial associations have been recently established from the Furongian (former Upper Cambrian) Potsdam Group of Quebec, Canada, and the coeval Elk Mound Group of Wisconsin, USA (Collette et al 2010).…”

“…Several notable examples of mortichnia, described by Knaust (2010) and listed by Collette et al (2010) and Seilacher and Hagadorn (2010), should be supplemented by the lower Cambrian redlichiid trilobite Eoredlichia intermedia (Lu, 1940), which has been found associated with its trace in the Chengjiang Lagerstätte (Ou et al 2009). …”