The unique fossil assemblage from the Lode Quarry (Upper Devonian, Latvia)

Abstract

The unique fossil fauna from the Lode clay quarry, lower Frasnian, Latvia, includes a diverse ichthyofauna of at least 15 taxa of agnathans and gnathostomes, representing most of the major taxa of Devonian vertebrates. Six new fish taxa (five species and one genus) were discovered during the last ten years. Exceptionally well‐preserved juvenile fishes (Asterolepis ornata, Lodeacanthus gaujicus) provide unique data on ontogenetic change. Diverse arthropods are recorded. Parasitic platyhelminth remains in juvenile fish bodies is their first discovery in the fossil record, and represents the oldest parasitic association ever found. A complete faunal and floral list for the Lode quarry is presented, with a detailed biostratigraphic section. Comparison of vertebrata taxa from the Gauja Regional Stage with similar of the Main Devonian Field, Scotland, Timan, Canada, and Germany is reviewed.

The Miguasha Fossil-Fish-Lagerstätte: a consequence of the Devonian land–sea interactions

“…In the second type, specimens are found in thick siltstone units originating from rapid burial (obrution events) in higher energy environments. Other Devonian and Carboniferous fish Fossil-Lagerstätten have been associated with thinly laminated tidal lithofacies and anoxic events (Feldman et al 1993(Feldman et al , 1994Kuecher et al 1990;Schultze 1999;Trewin 1986;Upeniece 2001). Threedimensional preservation of articulated fish has also been reported in a few Devonian localities associated either with reefal (Long and Trinajstic 2010) or fluvial palaeoenvironments (Daeschler et al 2006;Johanson 1997).…”

Fossil Crustaceans as Parasites and Hosts

“…Platyhelminth worms have been reported to infest Late Devonian (Frasnian) fishes from Latvia based on the presence of hooks in 16 specimens of the placoderm Asterolepis ornata and in 27 specimens of the acanthodian Lodeacanthus gaujicus (Upeniece, 1999(Upeniece, , 2001(Upeniece, , 2011De Baets et al, 2015). Two hooks were also found in a crustacean specimen ascribed to the Mysidacea, but Upeniece (2001Upeniece ( , 2011 considered the hooks too large relative to the size of this crustacean for it to have been a host.…”

“…Two hooks were also found in a crustacean specimen ascribed to the Mysidacea, but Upeniece (2001Upeniece ( , 2011 considered the hooks too large relative to the size of this crustacean for it to have been a host. Another hook was found close to a Conchostraca (clam shrimp) specimen, but the inference that it constitutes evidence of parasitism is not convincing.…”

“…Modern crustaceans can act as hosts of platyhelminthes (e.g. Fredensborg and Poulin, 2005;Boyko and Williams, 2011), but the fact that only a single specimen out of thousands of mysidaceans was reported to contain hooks (Upeniece, 2001) may indicate accidental parasitism of these crustaceans at best. For comparison, over 300 A. ornata and more than 50 specimens of L. gaujicus were found, of which 16 and 27 specimens yielded hooks.…”

“…These examples have in common that the evidence for parasitism is small in size compared to the other examples in Figure 12. The length of the only copepod body fossil in a fish is w1.0 mm, the length of larval pentastomids is 0.78 mm and platyhelminth hooks are only 0.4 mm long (Cressey and Boxshall, 1989;Upeniece, 2001). This small size explains the spotty occurrence of this type of parasitism in combination with rare circumstances allowing preservation of such fossils.…”