Remarkably preserved benthic organisms and their traces from a Middle Triassic (Muschelkalk) mud flat

Abstract

Knaust, D. 2010: Remarkably preserved benthic organisms and their traces from a Middle Triassic (Muschelkalk) mud flat. Lethaia, Vol. 43, pp. 344–356. A new Fossil‐Lagerstätte is reported from the Middle Triassic of Germany, preserving Foraminifera, Nematoda, Platyhelminthes, Nemertea, Annelida and a range of Arthropoda together with their traces. This is the oldest fossil record of free‐living nematodes and turbellarians, and the first occurrence of nemerteans in the Mesozoic. The rare preservation of the benthic associations together with their traces is unique; especially the abundant occurrence of different phyla as meiofauna (organisms with shortest dimension between 0.06 and 1 mm) provides an insight into the palaeoecological conditions of a 240‐Ma‐old muddy tidal flat. The preservation of benthic animals at the termination of their traces offers the exclusive opportunity to assign producers to the trace fossils. The results show that the discussed phyla were already established in the early Mesozoic in a similar diversity and composition as in modern analogues. The new Fossil‐Lagerstätte has the potential to prove a number of soft‐bodied taxa immediately after the end‐Permian mass extinction, which has wide‐ranging implications for phylogenetic interpretations. □Benthos, soft‐bodied organisms, Fossil‐Lagerstätte, Muschelkalk, trace fossils, Triassic.

Trace fossils from the Lower Muschelkalk of Raciborowice Górne (North Sudetic Synclinorium, SW Poland) and their palaeoenvironmental interpretation

“…1999;Knaust 2007aKnaust , 2008. According to Knaust (2008Knaust ( , 2010a, sipunculans (peanut worms) and polychaetes (eunicid-like polychaetes) are more probable tracemakers, as enteropneusts (acorn worms) are not typical bioeroders (see also Jaglarz and Uchman 2010). This ichnotaxon involves burrow system at the transition between firmgrounds and hardgrounds (Knaust and Costamagna 2012) and is a common component of the Glossifungites and Trypanites ichnofacies (Knaust 2008).…”

“…In carbonate deposits it forms borings in hardgrounds and is most typical of the inner ramp Ghibaudo et al 1996;Knaust 1998Knaust , 2007aKnaust , 2008Knaust , 2010aŽítt and Mikuláš 2006;.…”

Middle Turonian trace fossils from the Bystrzyca and Długopole sandstones

“…Cerianthid sea anem o nes, acorn worms and fish are also spec u lated as the pos si ble tracemakers of Thalassinoides (Myrow, 1995). Thalassinoides rep re sents a facies-cross ing ichnotaxon be ing re ported from deep ma rine en viron ments (Uchman 1995(Uchman , 1998) and more com monly, shallow-ma rine set tings (Ekdale and Bromley, 2003;Rodríguez-Tovar and Uchman, 2004a, b;2010;Malpas et al, 2005).…”

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.…”

“…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). …”