Fossilised guts in trilobites from the Upper Ordovician Letná Formation (Prague Basin, Czech Republic)

Abstract

The preservation of digestive structures of trilobites is extremely rare. Here we describe two new examples of trilobites from the Upper Ordovician Letná Formation (Prague Basin, Czech Republic), which display remains of the digestive system. The first specimen, assigned to <i>Selenopeltis buchi </i>(Barrande, 1846), exhibits cavities under the posterior part of the glabella and the axis of most thoracic segments. These cavities are interpreted as remains of metamerically paired digestive caeca and constitute the first example of preserved digestive structures in the order Odontopleurida. The second specimen belongs to <i>Birmanites ingens </i>(Barrande, 1852) and displays a tube-like structure, filled with a finely-grained material, that runs under the axial lobe of the entire trunk. We interpret this structure as a gut infilling similar to that repeatedly observed in the Moroccan <i>Basilicus calzadai</i>. These specimens confirm that the depositional environment of the Letná Formation was locally favourable to soft-tissue preservation. They also further document the presence of two different types of digestive systems in trilobites. The possibility that different processes might have been involved in the preservation of different parts of the trilobite gut is discussed, and several criteria to differentiate genuine gut remains from scavenger burrows are proposed

A probable case of heterochrony in the solutan Dendrocystites Barrande, 1887 (Echinodermata: Blastozoa) from the Upper Ordovician of the Prague Basin (Czech Republic) and a revision of the family Dendrocystitidae Bassler, 1938

“…A wide range of thecal sizes is observed for individuals of Dendrocystites in both the Letná and the Zahořany Formation. In both stratigraphic levels, palaeoenvironmental and taphonomic conditions were relatively similar, and no evidence of size sorting was reported so far (Chlupáč 1993, Mikuláš 1999, Kácha & Šarič 2009, Fatka et al 2013. Moreover, the skeleton of Dendrocystites is composed of hundreds of loosely articulated skeletal elements: this condition is typical of "type 1" taxa in the qualitative taphonomic classification of echinoderms proposed by Brett et al (1997;see also Lefebvre 2007).…”

“…The Letná Formation is a particularly thick lithostratigraphic unit (40-600 m), consisting mainly of sandstones alternating with finer sediments (Havlíček 1982, Fatka et al 2013. This unit has yielded particularly rich and diverse echinoderm assemblages, comprising the aristocystitid diploporan Aristocystites cf.…”

Survival of Burgess Shale-type animals in a Middle Ordovician deep-water setting

“…Digestivetract preservation in Selenopeltis (Fig. 2d) shows the serial paired digestive caeca described by Fatka et al (2013). The nonbiomineralized taxa are preserved as pyritized carbonaceous compressions (Fig.…”

The illaenid trilobites Vysocania (Vaněk & Vokáč, 1997) and Octillaenus (Barrande, 1846) from the Upper Ordovician of the Czech Republic, Portugal, Spain and Morocco

“…2) and localities in the Prague Basin of the Barrandian area (locality 1, Fig. 1A; see Havlíček 1998, Fatka et al 2013and Kraft et al 2015 for information on the Ordovician stratigraphy of the basin). The specimens of Vysocania moraveci sp.…”

“…Repository acronyms are as follows: CMP -Miguel Pires collection and CMG -Marques Guedes collection, Departamento de Geologia from the Faculdade de Ciências da Budil et al (2011), Fatka et al (2013) and Kraft et al (2015 Diagnosis. -Cranidium semi-circular in outline, very convex (sag.…”