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![Euchelicerate coxae. A, gnathobase of a eurypterid coxa from the Winneshiek Shale, SUI 143688-3, borehole H2, depth 15 ft (ca. 4.6 m). B, possible euchelicerate coxa from the Winneshiek Shale (same as Fig. 3E), SUI 143617-1, WS-12(2), W53/2. C, exuvial coxa of a juvenile Limulus polyphemus Linnaeus, 1758 (modern Atlantic horseshoe crab). [Colour figure can be viewed at wileyonlinelibrary.com]](profile/Hendrik-Nowak/publication/319064847/figure/fig6/AS:613870506872844@1523369542548/Euchelicerate-coxae-A-gnathobase-of-a-eurypterid-coxa-from-the-Winneshiek-Shale-SUI.png)
Euchelicerate coxae. A, gnathobase of a eurypterid coxa from the Winneshiek Shale, SUI 143688-3, borehole H2, depth 15 ft (ca. 4.6 m). B, possible euchelicerate coxa from the Winneshiek Shale (same as Fig. 3E), SUI 143617-1, WS-12(2), W53/2. C, exuvial coxa of a juvenile Limulus polyphemus Linnaeus, 1758 (modern Atlantic horseshoe crab). [Colour figure can be viewed at wileyonlinelibrary.com]
Source publication
The Middle Ordovician (Darriwilian) Winneshiek Shale from Winneshiek County, Iowa, USA, hosts a Konservat-Lagerstätte that has yielded a diverse fauna including soft-bodied fossils. The shale is rich in organic content; in particular, algal material and fragmentary cuticular remains. Palynological acid treatment alongside modified, low-manipulation...
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Context 1
... samples, except for one from near the boundary with the overlying St Peter Formation, yielded a rich organic fossil content (Fig. 1). Aside from fragmen- tary eurypterid cuticle ( Fig. 6A shows an example; compare Lamsdell et al. 2015a), and cyanobacterial sheaths, algae and acritarchs similar to those recov- ered during a separate earlier study (P.A. Zippi 2011, unpublished report), we recovered organic-walled microfossils with possible chelicerate and crustacean affinity that presently cannot be linked to macrofos- ...
Context 2
... samples, except for one from near the boundary with the overlying St Peter Formation, yielded a rich organic fossil content (Fig. 1). Aside from fragmen- tary eurypterid cuticle ( Fig. 6A shows an example; compare Lamsdell et al. 2015a), and cyanobacterial sheaths, algae and acritarchs similar to those recov- ered during a separate earlier study (P.A. Zippi 2011, unpublished report), we recovered organic-walled microfossils with possible chelicerate and crustacean affinity that presently cannot be linked to macrofos- sil groups known from this ...
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Citations
... Alternatively, these arrays may represent clusters of sensory setae. The examples here substantially expand the known paleogeographic range of microscopic arthropod SCFs-the current scattering of reports being exclusively restricted to the paleocontinent Laurentia Butterfield, 2008, 2022;Harvey et al., 2012;Harvey and Pedder, 2013;Nowak et al., 2018;Wallet et al., 2021; Table S1). ...
Burgess Shale−type (BST) Lagerstätten record an exceptional variety of Cambrian soft-bodied fauna, yet these deposits are typically restricted to outboard depositional settings >1000 km from the paleocoastline. For shallow, well-oxygenated shelf environments, our knowledge of non-mineralized animals (the majority of diversity) is severely limited, giving rise to substantial bias in our perception of Cambrian biotas. An alternate means of detecting soft-bodied Cambrian fauna, independent of paleobathymetry, is to use acid maceration to extract microscopic organic remains of non-mineralized animals, known as “small carbonaceous fossils” (SCFs). Here, a hitherto unknown diversity of Cambrian arthropod and mollusk remains are reported from shallow-marine sediments (Cambrian Stage 3 Mickwitzia Sandstone, Sweden). These microfossils comprise a variety of arthropod cuticles preserving sub-micron-scale anatomy alongside abundant radular mouthparts from mollusks—among the oldest known arthropod and molluscan SCFs on record. Significantly, at least three distinct types of fossil radula are identifiable (uniseriate, distichous, and polystichous forms), revealing that substantial diversification of the basic molluscan radula had already taken place by the early Cambrian. These cryptic elements of the biota—otherwise undetectable in such deposits—offer novel insights into Cambrian primary consumers as well as aspects of the fauna that are absent from deeper-water BST deposits.
... The ostracod fossil record covers an extremely prolonged time period from the Lower Cambrian, provided the Bradoriida is assigned to the class Ostracoda (Melnikova et al., 1997;Vannier et al., 2005;Williams et al., 2007). Palaeocopida, Myodocopida, and Podocopida are known from the later (upper) deposits (Harvey et al., 2012;Nowak et al., 2018). ...
The ostracods are an ideal object for studies of microevolutionary process, in particular, the evolution of sexual dimorphism, since they have a long and continuous fossil record, clearly expressed morphological traits, the presence of sexual dimorphism, and numerous and clearly distinguished age stages. The paper reviews previous reports on the evolution of sexual dimorphism in ostracods and reports new data on this phenomenon. For some ostracods, males have been shown to be the first to be involved in evolutionary process from the Miocene to the present. The carapace hinge of the males differs from that in females due to pedomorphic reorganizations. This phenomenon has been identified for the first time in the Mesozoic (Late Callovian) species Lophocythere acrolophos (Mikhailovtsement section, Ryazan oblast), the juvenile features of which continue to retain in the hinge of male carapaces.
... Famous examples from the Palaeozoic include the Cambrian Burgess Shale in Canada (Briggs et al., 1995) and the Maotianshan Shales in Chengjiang, China (Zhang et al., 2008), as well as the Devonian Hunsrück Slate in Germany (Bartels et al., 2009). Ordovician Konservat-Lagerstätten are mainly known from siliciclastic deposits of the Lower Ordovician of Morocco (shale; Van Roy et al., 2010, 2015Lefebvre et al., 2016;Martin et al., 2016) and Wales (mudstone; Botting et al., 2015), the Middle Ordovician of Iowa, USA (shale; Nowak et al., 2018;Briggs et al., 2018) and Wales (mudstone; Hearing et al., 2016), and the Upper Ordovician of Scotland (shale; Stewart and Owen, 2008), Wales (mudstone; Botting et al., 2011), Morocco (sandstone;Gutiérrez-Marco and García-Bellido, 2015), New York, USA (shale; Briggs et al., 1991;Farrell et al., 2009), Pennsylvania, USA (shale; Meyer et al., 2018) and South Africa (shale; Gabbott et al., 2017). In contrast, exceptional preservation of soft-bodied biota from Palaeozoic carbonates is rarely known and includes the Fossil-Lagerstätte of Manitoba, Canada (Young et al., 2007(Young et al., , 2012. ...
A diverse benthic fauna containing exceptionally preserved soft-bodied organisms is described from the new Vauréal Konservat-Lagerstätte from the Upper Ordovician Vauréal Formation (Katian) of Anticosti Island, Canada. These fossils occur as pyritic (or goethitic, if weathered), calcitic aggregates or sediment-filled voids on micritic bedding planes of a marlstone-limestone alternation originated on a shallow tropical carbonate ramp. Many organisms are preserved in association with their traces (e.g. burrows, trails), whose changing shapes indicate increasing cohesiveness of the substrate. Rapid burial (obrution) under dysoxic bottom conditions must have favoured exceptional preservation. Although anatomical details of the organisms are often lacking due to recrystallization, members of different groups of organisms could be interpreted based on their shape and other characteristic features, including those of which represent their oldest fossil record (i.e. Acoelomorpha, Turbellaria, Nemertea, Nematoda), beside Polychaeta, Sipuncula, Ostracoda and other Arthropoda. In parallel with molecular data, which recently have changed the phylogenetic status of some clades, this soft-bodied fauna and their traces not only record their appearance but add to the understanding of their body plan and behaviour. The new Konservat-Lagerstätte provides important information about a diverse benthic community in the Late Ordovician after the Great Ordovician Biodiversification Event (GOBE), and represents a calibration point for comparison across the Late Ordovician mass extinction. Moreover, comparable Fossil-Lagerstätten are probably more common in shallow-marine carbonates than currently known but might have been simply overlooked.
... Winneshiekia helps to resolve the relationships of early euchelicerates and confirms that xiphosurans ('horse-shoe crabs') are a paraphyletic group. Small carbonaceous fossils extracted from acid-treated samples of Winneshiek Shale include gnathobasic structures (Fig. 3i), which may represent the coxae of Winneshiekia or some similar xiphosuran (Nowak et al. 2018). ...
... The Winneshiek fauna also includes at least three different ostracods (Briggs et al. 2016). Filtering appendages preserved as small carbonaceous fossils (Fig. 3h) may belong to some of these taxa (Nowak et al. 2018). ...
... Some fossils, including conodont elements , linguloid brachiopods and the valves of Decoracaris, Iosuperstes and the probable leperditiid (Briggs et al. 2016), were biomineralized and therefore more readily preserved. A number of taxa, however, are preserved as organic remains, including organic-walled algae (Nowak et al. 2017), small carbonaceous arthropod remains (Nowak et al. 2018) and the eurypterid Pentecopterus (Lamsdell et al. 2015b). The phyllocarid C. winneshiekensis is likewise commonly represented by organic cuticles, but some specimens also preserve phosphatized gut contents and even traces of musculature (Briggs et al. 2016). ...
The Winneshiek Shale (Middle Ordovician, Darriwilian) was deposited in a meteorite crater, the Decorah impact structure, in NE Iowa. This crater is 5.6 km in diameter and penetrates Cambrian and Ordovician cratonic strata. It was probably situated close to land in an embayment connected to the epicontinental sea; typical shelly marine taxa are absent. The Konservat-Lagerstätte within the Winneshiek Shale is important because it represents an interval when exceptional preservation is rare. The biota includes the earliest eurypterid, a giant form, as well as a new basal chelicerate and the earliest ceratiocarid phyllocarid. Conodonts, some of giant size, occur as bedding plane assemblages. Bromalites and rarer elements, including a linguloid brachiopod and a probable jawless fish, are also present. Similar fossils occur in the coeval Ames impact structure in Oklahoma, demonstrating that meteorite craters represent a novel and under-recognized setting for Konservat-Lagerstätten.
... The arthropods include the phyllocarid Ceratiocaris winneshiekensis, the oldest known representative of the Ceratiocarididae , the oldest described eurypterid (Lamsdell et al. 2015b), a basal euchelicerate arthropod (Lamsdell et al. 2015a), and several species of ostracods . Additionally, organic-walled microfossils have been extracted from the Winneshiek Shale using palynological techniques (Nowak et al. 2017). Conodonts occur as new complete giant apparatuses as well as individual elements . ...
... The arthropods include the phyllocarid Ceratiocaris winneshiekensis, the oldest known representative of the Ceratiocarididae , the oldest described eurypterid (Lamsdell et al. 2015b), a basal euchelicerate arthropod (Lamsdell et al. 2015a), and several species of ostracods . Additionally, organic-walled microfossils have been extracted from the Winneshiek Shale using palynological techniques (Nowak et al. 2017). Conodonts occur as new complete giant apparatuses as well as individual elements . ...
Cuticular remains of the phyllocarid crustaceans Caryocaris? and Ceratiocaris? obtained via maceration of macrofossil remains in hydrofluoric acid are compared with dispersed fragments isolated using both the low-manipulation HF extraction and the standard HCl–HF–HCl method. The studied specimens were obtained from Ordovician and Silurian shales of the Šárka and Požáry formations (Prague Basin, Barrandian area, Czech Republic). This methodological approach allows a direct comparison of macrofossil remains with microfossils in residue. The differences in residues obtained through the two bulk-rock extraction methods are also discussed.
Mandibulate arthropods (myriapods, hexapods and crustaceans) account for a major component of extant animal diversity but their origins remain unclear. Here, we re‐examine the record of exceptionally preserved arthropodan microfossils, including mandibles, from the lower Cambrian (Stage 4) Mount Clark Formation, Northwest Territories, Canada. The assemblage comes from a single drillcore horizon and occurs as thousands of small carbonaceous fossils (SCFs) representing disarticulated body parts. The mandibles occur as isolated molar surfaces with an elongate outline, a heavy setal fringe, and a subtle right–left asymmetry. These are sufficiently distinctive to diagnose a new genus and species of arthropod, Masticaris fimbriata. Co‐occurring SCFs include diverse appendage lobes and ventral body fragments, along with spines and setae assignable to 53 morphological categories and occurring either singly or in arrays, including filter plates. Most are plausibly interpreted as belonging to the feeding apparatus of M. fimbriata. The mandibles and filter plates correspond to those in extant pancrustaceans, particularly branchiopods, although the mouthparts of some more basal Cambrian arthropods raise the possibility of convergent feeding adaptations. Overall, anatomical and taphonomic continuity with younger SCFs suggests that M. fimbriata belongs to an early pancrustacean radiation that is still largely cryptic in the fossil record. More generally, the assemblage provides an inventory of fine‐scale cuticular specializations in early Cambrian arthropods that prefigure the trophic versatility and ecological dominance of crustaceans in the modern marine fauna.
The Sirius Passet Lagerstätte of North Greenland is one of the oldest records of soft-bodied metazoan-dominated ecosystems from the early Cambrian. The Lagerstätte site itself is restricted to just a single c. 1-km-long outcrop located offshore from the shelf margin, in an area affected by metamorphic alteration during the Ellesmerian Orogeny (Devonian-Early Carboniferous). The recent recovery of small carbonaceous fossils (SCFs) to the south, in areas that escaped the effects of this deformation, has substantially expanded the known coverage of organic preservation into shallower water depositional settings in this region. Here, we describe additional SCF assemblages from the siliciclastic shelf succession of the Buen Formation (Cambrian Series 2, stages 3-4; c. 515 Ma), expanding the previously documented SCF biota. Newly recovered material indicates a rich diversity of non-mineralizing metazoans, chiefly represented by arthropod remains. These include the filtering and grinding elements of a sophisticated crustacean feeding apparatus (the oldest crustacean remains reported to date), alongside an assortment of bradoriid sclerites, including almost complete , 3D valves, which tie together a number of SCFs previously found in isolation. Other metazoan remains include various trilobite cuticles, diverse scalidophoran sclerites, and a range of metazoan fragments of uncertain affinity. This shallower water assemblage differs substantially from the Sirius Passet biota, which is dominated by problematic euarthropod stem-group members and sponges. Although some of these discrepancies are attributable to taphonomic or temporal factors, these lateral variations in taxonomic composition also point to significant palaeoenvironmental and/or palaeoecological controls on early Cambrian metazoan communities .
We describe an assemblage of small carbonaceous fossils (SCFs) and acritarchs from cored siltstones of the Lappajärvi impact structure, west‐central Finland. Previous studies had detected a depauperate acritarch biota ascribed to a deep Proterozoic origin—this age, however, was based on recovery of long‐ranging poorly age‐diagnostic sphaeromorphs. To resolve the age and provenance of these crater sediments, we applied low‐manipulation processing techniques optimized for retrieval of larger organic‐walled microfossils. Our study revealed a previously undetected assemblage containing numerous metazoan SCFs consisting of flattened ‘protoconodonts’ (grasping spines assignable to total group Chaetognatha) and a distinctive fossilised chaeta, possibly representing the oldest known annelid remains. Phylogenetically problematic fossils include various acritarchs (large Leiosphaeridia sp., Tasmanites tenellus, smaller sphaeromorphs, Synsphaeridium, Archaeodiscina and Granomarginata) and filamentous forms (Palaeolyngbya‐ and Rugosoopsis‐like filaments, Siphonophycus), likely representing prokaryotic or protistan grades of organisation. As well as adding new diversity to an emerging SCFs record, these data substantially refine the age of these sediments by more than half a billion years, to an early Cambrian Terreneuvian age. More specifically, the assemblage is equivalent to that of the Lontova Formation from the Baltic States and northwest Russia, but is previously unreported from Finland. Identification of Lontova‐type SCFs/organic‐walled microfossils at Lappajärvi further constrains the poorly resolved extent of maximum flooding during the early Cambrian in Baltica. Renewed attention should be directed to strata that have thus far produced only biostratigraphically long‐ranging or ambiguous palynological assemblages—‘SCF‐style’ processing can reveal hitherto undetected, age‐informative microfossils that are otherwise selectively removed in conventional palynological studies.
