Land Animals in the Silurian: Arachnids and Myriapods from Shropshire, England

Abstract

A new assemblage of arthropod cuticles from Upper Silurian rocks in Shropshire, England, includes at least two centipedes and a trigonotarbid arachnid. This unequivocal terrestrial fauna from the Silurian constitutes the earliest direct record of land animals. The presence of predatory arthropods suggests that complex terrestrial ecosystems were in place by the late Silurian (414 x 10(6) years before present) and that the animal invasion of the land occurred earlier than was previously thought.

The development of early terrestrial ecosystems

“…In the present southern hemisphere, the beginning of the phase is marked by records of Baragwanathia (Tims & Chambers, 1984), and in the present northern hemisphere where subsequent events are best documented, by the genus Zosterophyllum itself (Edwards, 1990). These two taxa exemplify the two major kinds of gross morphology in early land plants, viz.…”

“…peat) and within galleries in wood in a coal ball (Baxendale, 1979;Scott & Taylor, 1983). Coprolites are also known from the Lower Carboniferous of France and Scotland (Scott, 1977;Scott, Chaloner&Paterson, 1985;Rex&Galtier, 1986) Norton et al (1988), Norton et al (1989), Schawaller, Shear & Bonamo (1991), Selden, Shear & Bonamo (1991), Shear (1986), , Shear et al (1984), Shear et al (1987); Rhynie -Hirst (1922), Hirst & Maulik (1926); Ludford Lane -Jeram, Selden & Edwards (1990); Alkenan-der-Mosel - St0rmer (1970-76); Rheinischen Schiefergebirge -Schultka (1991).…”

“…The Irish fossils resemble Cooksonia which occurs in later Silurian and early Devonian sediments, but they are devoid of any anatomical detail. Cooksonia itself found in the Ludlow and Prfdolf of north America, Britain, Bohemia, Libya and Podolia (Richardson & Edwards, 1989;Edwards, 1990) is characterized by smooth isotomously branching axes terminated by globular or discoidal sporangia. Although no complete plants have been found, the small diameter and lengths of Silurian axes are suggestive of plants of short stature, probably rarely more than a few centimetres tall.…”

“…The Prfdolf Ludford Lane biota (Jeram, Selden & Edwards, 1990) may have lived in arhyniophytoid saltmarsh. The terrestrial animals in this biota share many similarities with later, Devonian, faunas.…”

The youngest trigonotarbidPermotarbus schubertin. gen., n. sp. from the Permian Petrified Forest of Chemnitz in Germany

“…The oldest trigonotarbid genus -Palaeotarbus Dunlop, 1999 -hails from the late Silurian (Pridoli: 419-423 Ma) of Ludford Lane in England (Jeram et al 1990;Dunlop 1996aDunlop , 1999a. This remains the oldest nonscorpion arachnid and, assuming that trigonotarbids were all terrestrial, one of the oldest land-living animals known to date.…”