Scoyenia burrows from Ordovician palaeosols of the Juniata Formation in Pennsylvania

Abstract

ABSTRACT. Scoyenia beerboweri is a new ichnospecies of burrow from the late Ordovician (Ashgill) Juniata Formation in central Pennsylvania, USA. The burrows are abundant in red calcareous palaeosols, and were created by animals living at the time of soil formation, because they are ®lled with red sediment like that of the palaeosol matrix, and both cut across, and are cut by, nodules of pedogenic carbonate. The isotopically light carbon and oxygen of carbonate in the palaeosols indicate a terrestrial ecosystem of well-drained¯oodplains in a tropical seasonally-dry semi-arid palaeoclimate. Back®ll layering within the burrows is evidence of a bilaterally symmetrical animal. Size distribution of the burrows reveals discontinuous growth, as found in arthropods. Ferruginized faecal pellets in the burrows indicate that they ingested sediment. For these reasons the burrows of Scoyenia beerboweri are most likely to be the work of millipedes. The nature of vegetation supporting them is unknown, although a single problematic plant-like fossil cast was found, and liverwort spores are widespread in rocks of this age. Vegetative biomass was limited judging from the degree of chemical weathering, extent of burial gleization and isotopic composition of carbon in the palaeosols. These distinctive respiration-dominated liverwort-millipede polsterlands lived at a time of global greenhouse climate, following Precambrian±Cambrian lichen-algal microbial earths and supplanted by Silurian brakelands of early vascular land plants.

A timeline for terrestrialization: consequences for the carbon cycle in the Palaeozoic

“…The gait preserved in these trackways is strongly suggestive of a millipede tracemaker [83] and, if correctly ascribed to Diplopoda, these traces provide the earliest evidence of Myriapoda in the fossil record. Backfilled burrows assigned to the ichnogenus Scoyenia in Upper Ordovician rocks in Pennsylvania have been considered to be produced by millipede burrowing [84], though this interpretation has been cast into doubt on functional grounds [83], and the sediments have alternatively been interpreted to be of marginal marine origin [85].…”

Coevolution of Life and Earth

“…These evolutionary changes were matched by comparable increases in depth and intensity of weathering indicated by paleosols, suggesting that not only individuals evolved but also soil communities distributed over broad continental areas (Retallack, 1997a). Woody steles of the earliest land plants frustrated early Silurian herbivores, which were mainly millipedes adapted to feeding on unvascularized liverworts (Retallack, 2001c). A coevolutionary swing toward woody plants to the disadvantage of herbivorous animals would not be enough in itself to change the world, unless such communities became globally distributed, commandeering the source of mineral nutrients in soil, metabolic gases in the atmosphere, and the distributive capacity of rivers and the ocean.…”

Acritarch Evidence for an Ediacaran Adaptive Radiation of Fungi

“…First, Archaeosporales are a group of free living soil glo me romycotans represented by Geosiphon pyriforme, which has a large vesicle to contain the endosymbiotic cya nobac te rium Nostoc punctiforme (Schüßler et al 1994, Schüßler 2012 (Rosentreter 1984, Belnap et al 2001. Current ecological succession may be re ca pi tu lating Precambrian communities of lichens and microbes on land (Retallack 2012), with cyanobacterial stage 2 reached very early in Earth history, lichen stage 3 by the Proterozoic, non-vascular land plant stage 6 by Ordovi cian (Katian), and the vascular plant stage 11 by Silurian (Wen lo ckian: Retallack 2001.…”