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Graptolites of the Fezouata Biota (late Tremadocian; Zagora area, Morocco). A, Araneograptus murrayi (Hall, 1865), AA-BIZ3-OI-35 showing nematularium (upper left) and distal end on another young colony (centre-right); B, Paradelograptus tenuis Lindholm, 1991, AA-OFTa-OI-23; C, Koremagraptus sp., AA-FETi-OI-1; D, Clonograptus rigidus (Hall, 1858), AA-JTZb-OI-19; E, Paradelograptus norvegicus (Monsen, 1937), AA-JTZ-OI-10; F, " Tetragraptus " bulmani Thomas, 1973, AA-BIZ13-OI-9; G, " Didymograptus sp. 1 " (cf. Lindholm, 1991), AA-BIZ31-OI-40; H–I, Paratemnograptus magnificus (Pritchard, 1892), fragment of a large rhabdosome (F, AA-BZG-OI-13) and detail of a stipe showing plaited thecal structure (triad budding without bithecae), AA-BIZ13-OI-10; J, Dictyonema? sp., AA-BZG-OI-14; K–M, " Kiaerograptus " supremus Lindholm, 1991, K = AA-BGF2-OI-7; L = AA-BGF2-OI-6, with detail of the proximal end (M) showing sicular bitheca (arrow); N–O, Hunnegraptus copiosus Lindholm, 1991, N = AA-JBZ-OI-117; O = AA-JBZ-OI-116; and P, Paradelograptus sp., AA-JTZ-OI-9. All specimens, except A, H, I and M, were photographed under alcohol. Scale bars: A, D, and H, 20 mm; E, 10 mm; C, F, K, L, and J, 5 mm; B, G, N, and O, 3 mm; I, and P, 2 mm; and M, 0.5 mm.  

Graptolites of the Fezouata Biota (late Tremadocian; Zagora area, Morocco). A, Araneograptus murrayi (Hall, 1865), AA-BIZ3-OI-35 showing nematularium (upper left) and distal end on another young colony (centre-right); B, Paradelograptus tenuis Lindholm, 1991, AA-OFTa-OI-23; C, Koremagraptus sp., AA-FETi-OI-1; D, Clonograptus rigidus (Hall, 1858), AA-JTZb-OI-19; E, Paradelograptus norvegicus (Monsen, 1937), AA-JTZ-OI-10; F, " Tetragraptus " bulmani Thomas, 1973, AA-BIZ13-OI-9; G, " Didymograptus sp. 1 " (cf. Lindholm, 1991), AA-BIZ31-OI-40; H–I, Paratemnograptus magnificus (Pritchard, 1892), fragment of a large rhabdosome (F, AA-BZG-OI-13) and detail of a stipe showing plaited thecal structure (triad budding without bithecae), AA-BIZ13-OI-10; J, Dictyonema? sp., AA-BZG-OI-14; K–M, " Kiaerograptus " supremus Lindholm, 1991, K = AA-BGF2-OI-7; L = AA-BGF2-OI-6, with detail of the proximal end (M) showing sicular bitheca (arrow); N–O, Hunnegraptus copiosus Lindholm, 1991, N = AA-JBZ-OI-117; O = AA-JBZ-OI-116; and P, Paradelograptus sp., AA-JTZ-OI-9. All specimens, except A, H, I and M, were photographed under alcohol. Scale bars: A, D, and H, 20 mm; E, 10 mm; C, F, K, L, and J, 5 mm; B, G, N, and O, 3 mm; I, and P, 2 mm; and M, 0.5 mm.  

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The Lower Ordovician Fezouata Konservat-Lagerstätte from southern Morocco has been one of the major palaeontological discoveries of the last decade. It provides a unique insight into one of the most critical periods in the evolution of marine life: the Cambrian-Ordovician transition. However, its potential for deciphering key trends in animal diver...

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... graptolite species have been recognised through the studied succession (Fig. 5). These include the index species of the A. murrayi and Hunnegraptus copiosus graptolite biozones, which are the uppermost graptolite zones of the Tremadocian (Loydell, 2012). A. murrayi occurs in great abundance from 240 to 295 m above the base of the Fezouata Shale. EPF-bearing Interval 1 falls within the A. murrayi Biozone. EPF- ...
Context 2
... are both abundant and well preserved throughout the Fezouata Shale (Fig. 5). They are reliable markers for dating and correla- tions, especially in the Ordovician ( Webby et al., 2004;Sadler et al., 2009). The graptolite assemblages of the Fezouata Shale are dominated by planktonic forms that are assumed to have lived in epipelagic niches ( Cooper et al., 1991Cooper et al., , 2012a, with a small percentage of ...
Context 3
... markers for dating and correla- tions, especially in the Ordovician ( Webby et al., 2004;Sadler et al., 2009). The graptolite assemblages of the Fezouata Shale are dominated by planktonic forms that are assumed to have lived in epipelagic niches ( Cooper et al., 1991Cooper et al., , 2012a, with a small percentage of rooted benthic dendroids ( Fig. 5C and J). The planktonic ones have a cosmopolitan dis- tribution and have been widely used for global correlations. They occur in Scandinavia (Lindholm, 1991), North America ( Williams and Stevens, 1991;Maletz, 1997;Jackson and Lenz, 2003), South America ( Maletz and Egenhoff, 2001;Ortega and Albanesi, 2005), China (Feng et al., 2009) and ...

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... Considering only diversity, there are (almost) as many hurdiid taxa exclusively known from shallow-water settings as taxa exclusively known from deep-water environments ( Fig. 6; Table 2). However, it is important to note that hurdiids are rare or absent in shallowwater deposits in strata of Cambrian Series 2, Miaolingian, Furongian and lower Ordovician as a whole, with the exception of the Fezouata biota (Lefebvre and Botting, 2007;Martin et al., 2016;Saleh et al., 2021), where the hurdiids are relatively both diverse and abundant (two, or possibly-three genera; Table 2; Van Roy and Briggs, 2011;Van Roy et al., 2015a;Van Roy et al., 2015b). This could be interpreted as a preference of hurdiids for deep-water settings. ...
... Specific numbers in circle representing different hurdiid taxa correspond to those in Fig. 2. The taxa (Schinderhannes and Zhenghecaris) with questionable hurdiid affinities are excluded. References for the depth/environment displayed for all the deposits: Afon Gam (Botting et al., 2015); Balang (Liu, 2013;Yun et al., 2019); Burgess Shale Jackson, 2006, 2008;Gaines, 2014;O'Brien et al., 2014); Carrara Formation (Palmer and Halley, 1979); Chengjiang (Hu, 2005;Zhao et al., 2009;Saleh et al., 2022); Fezouata (Lefebvre and Botting, 2007;Martin et al., 2016;Saleh et al., 2021); Guole (Zhu et al., 2016;Lerosey-Aubril et al., 2017); Little Bear (Harvey and Butterfield, 2011); Mantou Formation (Zhang and Liu, 1996); Marjum Formation (Elrick and Snider, 2002); Pioche Formation (Webster et al., 2008); Spence Shale (Aigner, 1985;Garson et al., 2012); Wheeler Formation (Foster and Gaines, 2016); Wiśniówka Sandstone Formation ( _ Zyliń ska et al., 2006); Zawiszyn Formation (Dzik and Lendzion, 1988;Daley and Legg, 2015); Zhangxia Formation (Sun et al., 2019;Sun et al., 2020a). Abbreviations: Cam., Cambrian; Fm., Formation; Ord., Ordovician. ...
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Over one hundred of arthropod fossil species have been described from the famous Chengjiang Lagerstätte (South China, Cambrian Stage 3, ca. 518 Ma) including a diverse assemblage of radiodonts – a group containing Anomalocaris and its relatives. These iconic stem-group euarthropods include some of the largest animals of the time, and some are known from hundreds of specimens. A longstanding conundrum has been the rarity or absence of hurdiids from Cambrian Series 2 Lagerstätten like Chengjiang. This is because radiodonts are generally common in such deposits and the oldest radiodont ever discovered is a hurdiid. Furthermore, this family displays the widest geographic and temporal ranges of all radiodont families, and the highest diversity. Here we document the first hurdiid frontal appendages from Chengjiang, which display unique features within the family and may provide insights for understanding the character evolution of hurdiid appendages. The palaeoenvironmental distribution of hurdiids suggests that the rarity of hurdiids in Chengjiang may be due to a preference for deeper water environments, and the later success of this family from the Wuliuan onwards may relate to their ability to tolerate cooler water temperatures than other radiodont families. The palaeogeographical, palaeoenvironmental, and stratigraphical patterns observed in hurdiids maybe caused in part by the limited distributions of Konservat-Lagerstätten in the Cambrian as well.
... The depositional environment of the Liexi fauna is interpreted to be an offshore to lower shoreface, in accordance with palaeogeographic setting [12]. In contrast with some other [33][34][35], the Liexi fauna occurs in a marine geological setting with muddy substrate, and its burial and preservation probably resulted from a sudden muddy flood moving from the shelf edge to the upper slope, similar to the burial Fezouata biota [36,37]. Most of the documented fossiliferous Early Ordovician Lagerstätten globally are interpreted to occur in high-latitude regions, such as the Fezouata biota near the South Pole [2,3] and the Afon Gam biota from North Wales at a palaeolatitude of 60°S [4]. ...
... [38,39]. Although the Liexi fauna has a similar phyletic composition to the Fezouata biota (table 1), e.g. the high abundance and diversity of organisms [36,40], it shows some distinctive faunal features, e.g. the unique palaeoscolecidan worms, rhombiferan and cyclocystoid-like echinoderms. ...
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The Ordovician Lagerstätten record substantial amounts of excellent preservation and soft-bodied fossils during the Great Ordovician Biodiversification Event (GOBE). However, few Lagerstätten are known from the Lower Ordovician, most of which are preserved in restricted environments and high-latitude regions. Here, we report on a new tropical Lagerstätte, Liexi fauna, which has been recently discovered from a carbonate succession within the Lower Ordovician Madaoyu Formation in western Hunan, South China. It contains a variety of soft tissues, as well as rich shelly fossils, including palaeoscolecidan worms, possible Ottoia , trilobites, echinoderms, sponges, graptolites, polychaetes, bryozoans, conodonts and other fossils. The fauna includes taxa that are not only Cambrian relics, but also taxa originated during the Ordovician, constituting a complex and complete marine ecosystem. The coexistence of the Cambrian relics and Ordovician taxa reveals the critical transition between the Cambrian and Palaeozoic Evolutionary faunas. The unusual Liexi fauna provides new evidence for understanding Ordovician macroevolution and the onset of the GOBE.
... Bivalves from the Montagne Noire (France, Babin, 1982) occur in the Saint Chinian and La Maurerie formations and the deposits were formed in relatively deep shelf at/or slightly below storm wave base (Vidal, 1996;Vizcaïno and Lefebvre, 1999;Vizcaïno et al., 2001;Lefebvre, 2007). The Lower Ordovician bivalves from Morocco come from the Fezouata Fm. (Polechová, 2016); their depositional environment is within the offshore to lower shoreface, close to storm wave base (Martin et al., 2016). Cope and Kříž (2013) summarised the palaeobiogeography of the Late Ordovician bivalves. ...
Article
The bivalve fauna from the Sandbian Letná Formation of the Prague Basin includes ten species: Praenucula bohemica, Myoplusia cf. incisa, Synek sp., Pseudarca? incola, Cuneamya catilloides, Modiolopsis draboviensis, Macrodesma flexa, Ectenocardiomorpha veterana, Whiteavesia antiquior, and Myodakryotus patricia. Modiolopsis, often used as a “cumulative” name for pteriomorphids from the Late Ordovician, is recorded from the Letná Formation, including only one species. Species palaeoecology is analysed and briefly discussed. Although the infaunal and semi-infaunal elements still prevail, the epifaunal bivalves are also significantly represented. The Sandbian bivalve fauna of the Barrandian area comes from high latitudes of the Southern hemisphere. Pteriomorphids are dominant, but heteroconchs and protobranchs belong also to important elements in the bivalve association from the Letná Formation. From coarse quartzose sandstones of the Letná Formation the Modiolopsis draboviensis Association of the Modiolopsis Community is established. The composition of the Late Ordovician bivalve fauna from the different areas and sedimentological environments are compared and discussed. There is a clear trend toward rapid diversification of pteriomorphids and epifaunal bivalves in all palaeocontinents. Bivalves from the Letná Formation of the Barrandian area show affinities to the Sandbian bivalve faunas from Avalonia, Laurentia and Morocco.
... Exceptional fossil preservation, consisting of the preservation of soft anatomies in the rock record, is crucial to reconstruct accurate pictures of ancient ecosystems (Butterfield, 1995;Hou et al., 2004;Van Roy et al., 2010;Fu et al., 2020;Nanglu et al., 2020;Saleh et al., 2020aSaleh et al., , 2021a. The Fezouata Shale discovered in Morocco is an Early Ordovician deposit bearing a large number of taxa that were previously unknown from this time interval (Van Roy et al., 2010, 2015Martin et al. 2016). Exceptionally preserved fossils in the Fezouata Shale are discovered in levels that are relatively rich in iron . ...
Article
The Fezouata Shale in Morocco is the most diverse Lower Ordovician unit yielding soft-tissue preservation. Iron played a crucial role in the preservation of soft parts in this formation through the damage of bacterial membranes under oxic conditions and the pyritization of soft parts under the activity of bacterial sulfate reduction. However, the origin of Fe in this formation remains largely speculative. Herein, trace and rare earth elements were investigated in drilled-core sediments from the Fezouata Shale. It is shown that a correlation exists between Fe and Al suggesting that most Fe has a detrital source. Elemental concentrations in the Fezouata Shale are most comparable to rivers and are the least similar to loess and sediments deposited near active island arcs. In this sense, continental weathering and its related Fe in river fluxes dictated occurrences of exceptional fossil preservation in the Fezouata Shale.
... The Fezouata Shale is an approximately 850 m thick succession composed of argillites with sandy mudstone and siltstone beds . The depositional environment facilitated a rapid burial of autochthonous communities in an open shallow marine environment (Martin et al. 2016a), ranging from offshore to the foreshore with a depth range from 50 to 150 m Martin et al. 2016a). ...
... The Fezouata Shale is an approximately 850 m thick succession composed of argillites with sandy mudstone and siltstone beds . The depositional environment facilitated a rapid burial of autochthonous communities in an open shallow marine environment (Martin et al. 2016a), ranging from offshore to the foreshore with a depth range from 50 to 150 m Martin et al. 2016a). ...
... The Fezouata Biota provides a critical link between the Cambrian Explosion and the Great Ordovician Biodiversification Event, due to its temporal position between both events (Servais et al. 2010;Landing et al. 2018;Servais and Harper 2018). Exceptional preservation in the Fezouata Shale is restricted to two intervals (Martin et al. 2016a;Lefebvre et al. 2018), the lower of which is about 70 m thick and situated 260-330 m above the Cambrian/ Ordovician contact, and the second of which is about 50 m thick and 570-620 m above the Cambrian/Ordovician contact. The lower interval with exceptional preservation is situated mostly within the Araneograptus murrayi Zone and lowermost parts of the Hunnegraptus copiosus Zone, which both correspond to the third slice of the Tremadocian stage (or Tr3, see Gutiérrez-Marco and Martin 2016;Lefebvre et al. 2018). ...
Article
Pilekiines are the earliest diverging members of the successful trilobite family Cheiruridae. The pilekiine genus Anacheirurus is characterized by sub-quadratic to sub-oval glabella, pitted genae, and a distinct trunk with elongated pleural spines in its posterior part. Anacheirurus adserai is a common component of the Fezouata Shale (Lower Ordovician, Morocco), where it was intially included into several species of the genus Lehua. This assignment and taxonomic over-splitting created confusion, overestimated cheirurid diversity at this locality, and simultaneously underestimated morphological variability within A. adserai. In this contribution we examine new material of A. adserai from the Fezouata Shale, clarifying its morphology and systematics. A detailed re-description of the species shows that Anacheirurus is distinct from Lehua, the latter being a more derived member of Cheiruridae. The comparison of Anacheirurus with other pilekiines shows that morphological variability within this subfamily is mostly constrained to the trunk region. Exceptionally preserved specimens of A. adserai from the Fezouata Shale show details of appendages, revealing the endopodite and exopodite morphologies in early members of Cheiruridae. The endopodite of A. adserai is unique among trilobites in possessing comparatively longer distal podomeres 5 and 6, but otherwise, it has the same general morphology as other described trilobite endopodites. The exopodite morphology of A. adserai shows characters typical of some Cambrian species but differs in several aspects from those known in post-Cambrian taxa. It is concluded that trilobite exopodite morphology was probably more variable than the endopodite morphology, which remains rather conservative across different taxa. Morphological diversity of trilobite exopodites in post-Cambrian taxa might be related to ecological escalations during the Ordovician biodiversification and he transition between Cambrian and Ordovician trilobite faunas.
... formed of polysaccharides), such as annelids and priapulids, or even entirely cellular bodies, such as jellyfish (e.g. Liu et al., 2008;Zhang et al., 2008;Lamsdell et al., 2013;Duan et al., 2014;Lei et al., 2014;Gutiérrez-Marco and García-Bellido, 2015;Martin et al., 2016a;Lerosey-Aubril et al., 2017). Thus, studies based on mineralized parts in the fossil record provide incomplete samples of past animal life on Earth. ...
... In the early 2000s, a new Lagerstätte was discovered in the Zagora area, Central Anti-Atlas of Morocco. The Fezouata Shale is, so far, the only unit to yield a highly diverse, fully marine exceptionally preserved Ordovician biota (Van Roy et al., 2010, 2015aLefebvre et al., 2016a;Martin et al., 2016a). With more than 185 taxa of marine invertebrates recovered from numerous sites in the Zagora area, this formation offers new insights into the diversification of metazoans, at a key interval between the Cambrian Explosion and the Ordovician Radiation (Van Roy et al., 2010, 2015aLefebvre et al., 2016a). ...
... The first one occurs in concretions (Gaines et al., 2012b). The second type of exceptional preservation is associated with shales in a generally shallower environment in comparison to the classical Burgess Shale (Martin et al., 2016a;Vaucher et al., 2016). Most Fezouata BST fossils collected in shales are preserved as molds or imprints on the sediments (Martin et al., 2016a), and it is unclear whether these organisms were originally preserved as carbonaceous compressions. ...
Article
The Fezouata Biota in Morocco is the only Lower Ordovician Lagerstätte yielding a biologically diverse assemblage in a fully marine environment, whilst also containing organisms typical of Cambrian Burgess Shale-type (BST) ecosystems. Fossils from the Fezouata Shale share the same mode of preservation as Cambrian BST biotas defined by carbonaceous compressions and accessory authigenic mineralization. Most organisms of the Fezouata Biota were already dead and decaying on the seafloor when they were buried in-situ by occasional storm-induced deposits in an environment just below the storm-weather wave base. Pre-burial decay in the Fezouata Shale was responsible for the non-preservation of completely cellular organisms such as jellyfish. These conditions contrast with the processes described for soft-tissue preservation in the Burgess Shale (Canada) and the Chengjiang Biota (China). In these two Cambrian Lagerstätten, animals were transported alive or shortly after death by obrution events to an environment that was favorable for preservation. Despite preservational biases, the autochthonous assemblages of the Fezouata Shale offer a unique opportunity to decipher the structure of in-situ communities and ecological dynamics in Early Palaeozoic seas, when compared to the allochthonous communities of most Cambrian BST biotas.
... Previous studies have interpreted the sedimentary environment associated with the Guanshan Biota as mainly offshore transition with common storm events Chen et al. 2019), which is comparable with the Cambrian Stage 4 Emu Bay Shale from Australia (Paterson et al. 2016) and the Ordovician Fezouata Biota (Martin et al. 2016). However, typical storm-generated structures such as hummocky cross-stratification, an indicator of oscillatory combined flows reflecting deposition under high-energy storm conditions (Arnott and Southard 1990;Cheel 1990;Southard et al. 1990;Cheel and Leckie 1993;Yokokawa et al. 1999;Dumas et al. 2005) are absent in the Wuding succession. ...
... The absence of basal conglomerates and the occurrence of medium to very coarse sandstones with few granules at the base of the Wulongqing Formation in the Wuding area (Fig. 4e) suggest a relatively deeper and low-energy clastic sedimentary environment than that in the Malong and Kunming areas Chen et al. 2019), although this remains to be tested because detailed continuous successions of the Wulongqing Formation have not been studied sedimentologically. Overall, the depositional environment here is interpreted as offshore to lower shoreface as defined by Martin et al. (2016) and the offshore zone of Buatois and Mángano (2011), which slightly extends below the storm wave base (Fig. 3g). ...
... The relatively shallow sedimentary environment (lower offshore in Martin et al. 2016 or offshore in Buatois and Mángano 2011) of the Guanshan Biota also separates it from most other Cambrian Lagerstätten worldwide except, perhaps, for the early Cambrian Emu Bay Shale from Australia, which is interpreted to have been deposited in a nearshore micro-basin setting adjacent to an active tectonic margin that generated continual syndepositional faulting and slumping (Paterson et al. 2016). The Guanshan Biota is also comparable with the Ordovician Fezouata Biota, both in terms of depositional environment and shelly faunal composition (Van Roy et al. 2015;Saleh et al. 2018). ...
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The Guanshan Biota is an unusual early Cambrian Konservat-Lagerstätte from China and is distinguished from all other exceptionally preserved Cambrian biotas by the dominance of brachiopods and a relatively shallow depositional environment. However, the faunal composition, overturn and sedimentology associated with the Guanshan Biota are poorly understood. This study, based on collections through the best-exposed succession of the basal Wulongqing Formation at the Shijiangjun section, Wuding County, eastern Yunnan, China recovered six major animal groups with soft tissue preservation; brachiopods vastly outnumbered all other groups. Brachiopods quickly replace arthropods as the dominant fauna following a transgression at the base of the Wulongqing Formation. A transition from a botsfordiid-, eoobolid-and acrotretid-to an acrotheloid-dominated brachiopod assemblage occurs up-section. Four episodically repeated lithofacies reveal a relatively low-energy, offshore to lower shoreface sedimentary environment at the Shijiangjun section, which is very different from the Wulongqing Formation in the Malong and Kunming areas. Multiple event flows and rapid obrution are responsible for faunal overturn and fluctuation through the section. A detailed lithofacies and palaeontological investigation of this section provides a better understanding of the processes and drivers of faunal overturn during the later phase of the Cambrian Explosion. Supplementary material: Composition and comparison of the Malong Fauna and the Guanshan Biota is are available at: https://doi.org/10.6084/m9.figshare.c.5080799
... Previous studies have interpreted the sedimentary environment associated with the Guanshan Biota as mainly offshore transition with common storm events Chen et al. 2019), which is comparable with the Cambrian Stage 4 Emu Bay Shale from Australia (Paterson et al. 2016) and the Ordovician Fezouata Biota (Martin et al. 2016). However, typical storm-generated structures such as hummocky cross-stratification, an indicator of oscillatory combined flows reflecting deposition under high-energy storm conditions (Arnott and Southard 1990;Cheel 1990;Southard et al. 1990;Cheel and Leckie 1993;Yokokawa et al. 1999;Dumas et al. 2005) are absent in the Wuding succession. ...
... The absence of basal conglomerates and the occurrence of medium to very coarse sandstones with few granules at the base of the Wulongqing Formation in the Wuding area (Fig. 4e) suggest a relatively deeper and low-energy clastic sedimentary environment than that in the Malong and Kunming areas Chen et al. 2019), although this remains to be tested because detailed continuous successions of the Wulongqing Formation have not been studied sedimentologically. Overall, the depositional environment here is interpreted as offshore to lower shoreface as defined by Martin et al. (2016) and the offshore zone of Buatois and Mángano (2011), which slightly extends below the storm wave base (Fig. 3g). ...
... The relatively shallow sedimentary environment (lower offshore in Martin et al. 2016 or offshore in Buatois and Mángano 2011) of the Guanshan Biota also separates it from most other Cambrian Lagerstätten worldwide except, perhaps, for the early Cambrian Emu Bay Shale from Australia, which is interpreted to have been deposited in a nearshore micro-basin setting adjacent to an active tectonic margin that generated continual syndepositional faulting and slumping (Paterson et al. 2016). The Guanshan Biota is also comparable with the Ordovician Fezouata Biota, both in terms of depositional environment and shelly faunal composition (Van Roy et al. 2015;Saleh et al. 2018). ...
Article
Full-text available
The Guanshan Biota is an unusual early Cambrian Konservat-Lagerstätte from China and is distinguished from all other exceptionally preserved Cambrian biotas by the dominance of brachiopods and a relatively shallow depositional environment. However, the faunal composition, overturn and sedimentology associated with the Guanshan Biota are poorly understood. This study, based on collections through the best-exposed succession of the basal Wulongqing Formation at the Shijiangjun section, Wuding County, eastern Yunnan, China recovered six major animal groups with soft tissue preservation; brachiopods vastly outnumbered all other groups. Brachiopods quickly replace arthropods as the dominant fauna following a transgression at the base of the Wulongqing Formation. A transition from a botsfordiid-, eoobolid- and acrotretid- to an acrotheloid-dominated brachiopod assemblage occurs up-section. Four episodically repeated lithofacies reveal a relatively low-energy, offshore to lower shoreface sedimentary environment at the Shijiangjun section, which is very different from the Wulongqing Formation in the Malong and Kunming areas. Multiple event flows and rapid obrution are responsible for faunal overturn and fluctuation through the section. A detailed lithofacies and palaeontological investigation of this section provides a better understanding of the processes and drivers of faunal overturn during the later phase of the Cambrian Explosion. Supplementary material: Composition and comparison of the Malong Fauna and the Guanshan Biota is are available at: https://doi.org/10.6084/m9.figshare.c.5080799
... Discovered in the early 2000s in the Central Anti-Atlas of Morocco, the Early Ordovician Fezouata Lagerstätte has dramatically altered evolutionary scenarios on the initial diversification of metazoans during the early Paleozoic , 2015aLefebvre et al. 2016b;Martin et al. 2016a). In the Zagora area, the~900 meter sediments of the Fezouata Shale ( Fig. 1A) have yielded over 200 taxa of marine invertebrates, the majority of which are shelly organisms typical of the Great Ordovician Biodiversification Event including asterozoans, bivalves, rhynchonelliformean brachiopods, cephalopods, crinoids, gastropods, graptolites, ostracods, and trilobites (Havlíček 1971;Destombes et al. 1985;Ebbestad 2016;Gutiérrez-Marco and Martin 2016;Lefebvre et al. 2016a;Martin et al. 2016b;Polechová 2016). ...
... Discovered in the early 2000s in the Central Anti-Atlas of Morocco, the Early Ordovician Fezouata Lagerstätte has dramatically altered evolutionary scenarios on the initial diversification of metazoans during the early Paleozoic , 2015aLefebvre et al. 2016b;Martin et al. 2016a). In the Zagora area, the~900 meter sediments of the Fezouata Shale ( Fig. 1A) have yielded over 200 taxa of marine invertebrates, the majority of which are shelly organisms typical of the Great Ordovician Biodiversification Event including asterozoans, bivalves, rhynchonelliformean brachiopods, cephalopods, crinoids, gastropods, graptolites, ostracods, and trilobites (Havlíček 1971;Destombes et al. 1985;Ebbestad 2016;Gutiérrez-Marco and Martin 2016;Lefebvre et al. 2016a;Martin et al. 2016b;Polechová 2016). The Fezouata Biota also comprises a high number of soft-bodied to lightly sclerotized taxa, generally preserved as colorful iron oxides, resulting from the weathering of pyrite (Van Roy 2006;Van Roy et al. 2010, 2015aLefebvre et al. 2016b;Martin et al. 2016a). ...
... In the Zagora area, the~900 meter sediments of the Fezouata Shale ( Fig. 1A) have yielded over 200 taxa of marine invertebrates, the majority of which are shelly organisms typical of the Great Ordovician Biodiversification Event including asterozoans, bivalves, rhynchonelliformean brachiopods, cephalopods, crinoids, gastropods, graptolites, ostracods, and trilobites (Havlíček 1971;Destombes et al. 1985;Ebbestad 2016;Gutiérrez-Marco and Martin 2016;Lefebvre et al. 2016a;Martin et al. 2016b;Polechová 2016). The Fezouata Biota also comprises a high number of soft-bodied to lightly sclerotized taxa, generally preserved as colorful iron oxides, resulting from the weathering of pyrite (Van Roy 2006;Van Roy et al. 2010, 2015aLefebvre et al. 2016b;Martin et al. 2016a). Some of these exceptionally preserved organisms (e.g., cirripede crustaceans, eurypterid, and xiphosuran chelicerates) represent the oldest occurrences of particular marine invertebrates, previously recorded from younger Paleozoic Lagerstätten , 2015a. ...
Thesis
The Fezouata Shale is the most diverse Lower Ordovician unit with exceptional fossil preservation. Fossils from this formation altered our understanding of early metazoan communities at the transition between the Cambrian Explosion and the Ordovician Radiation. The paleontology and the general sedimentological context of the Fezouata Shale are well established. However, little was done to understand the interaction between both, and studies regarding fossil preservation remain scarce. In this thesis, we investigate the general conditions and mechanisms responsible for soft-tissue preservation in the Fezouata Shale. Comparing brachiopod, bivalve, and trilobite size fluctuations between sites allowed us to constrain burial rates in this formation. This permitted the discovery of a relative post-mortem burial tardiness in sites where exceptional fossil preservation occurred. Moreover, mineralogical investigations showed a correlation between particular chlorite phases (i.e. chamosite/berthierine) and preserved soft parts. This mineralogy may have slowed down oxic decay and its deposition was most probably due to periods with high seasonality. Furthermore, we hypothesized for the first time, a possible implication of biomolecules (i.e. ferritin) in the preservation of soft parts. This, if confirmed, would resolve the observed discrepancies between the fossil record preserving nervous systems to the exclusion to everything else, and decay experiments showing that nervous tissues are among the first structures to decay and disappear in laboratory conditions. Additionally, we show that metamorphism was not operational in the Fezouata Shale. However, modern weathering leached organic material from surface sediments and transformed pyrite into iron oxides. This finding infers that the original mode of preservation of the Fezouata Shale comprises both carbonaceous compressions and accessory authigenic pyritization. The direct implication of this work was shown through a comparison of enigmatic patterns preserved in three groups of echinoderms. It appears that some of these patterns in eocrinoids and somasteroids do not reflect original anatomies and are preservation artifacts. However, it is certain that the structures preserved in stylophorans are real, closing a long-standing debate on the affinity of this animal group. Finally, a general comparison between the Fezouata Shale and Cambrian Lagerstätten allowed us to decipher the implication of the suggested taphonomic pathway on fossil preservation. It appears that the Fezouata Shale mechanism for preservation failed to preserve completely cellular organisms (e.g. chordates, ctenophores, medusoids) implying a possible underestimation of the original Fezouata Biota and confirming that the Cambrian Explosion and the Ordovician Radiation are one single episode of anatomical innovation. Thus, all these results have implications on understanding ecosystems, and evolution at the dawn of animal life and may contribute in the future to the development of a predictive approach for the discovery of exceptionally preserved biotas
... North of Zagora, the Lower Ordovician strata are exposed in the Ternata plain, forming the Tremadocianearly Darriwilian Outer Feijas Shale Group (Choubert et al. 1947;Destombes et al. 1985). The Outer Feijas Shale Group unconformably overlies middle Cambrian sandstones of the Tabanite group and underlies the First Bani Group (Middle Ordovician; Destombes et al. 1985;Martin et al. 2015). The Outer Feijas Shale Group is subdivided into the Lower Fezouata Shale formation, the Upper Fezouata Shale formation, the Zini sandstone and quatzite formation, and the Tachilla Shale formation (Destombes et al. 1985). ...
... The Fezouata Shale is generally composed of argillites with blue-green to yellow-green sandy mudstone and siltstone interbeds (Destombes et al. 1985). It is interpreted to have been deposited around storm wave-base, in an open shallow-marine environment (Martin et al. 2015), ranging from proximal offshore to foreshore with a depth range of 50-150 m (Martin et al. 2015;Vaucher et al. 2016). The fluctuations of the water level are of low amplitude, but it is possible to recognize the deepest depositional environment in the middle of the Fezouata Shale . ...
... The Fezouata Shale is generally composed of argillites with blue-green to yellow-green sandy mudstone and siltstone interbeds (Destombes et al. 1985). It is interpreted to have been deposited around storm wave-base, in an open shallow-marine environment (Martin et al. 2015), ranging from proximal offshore to foreshore with a depth range of 50-150 m (Martin et al. 2015;Vaucher et al. 2016). The fluctuations of the water level are of low amplitude, but it is possible to recognize the deepest depositional environment in the middle of the Fezouata Shale . ...
Article
Nektaspids are Palaeozoic non-biomineralized euarthropods that were at the peak of their diversity during the Cambrian Period. Post-Cambrian nektaspids are a low-diversity group with only a few species described so far. Here we describe Tariccoia tazagurtensis, a new species of small-bodied nektaspid from the Lower Ordovician Fezouata Shale of Morocco. The new species differs from the type (and only other known) species from the Ordovician strata of Sardinia (Italy), Tariccoia arrusensis, in possessing more pointed genal angles, a cephalon with marginal rim, a pygidium with anterior margin curved forwards, a rounded posterior margin, and longer and more curved thoracic tergites. The two specimens of T. tazagurtensis sp. nov. show remains of digestive glands that are comparable to those seen in the Cambrian nektaspid Naraoia. The rare occurrence of T. tazagurtensis sp. nov. in the Fezouata Shale and the distribution of other liwiids suggest that these liwiids were originally minor members of open-marine communities during the Cambrian Period, and migrated into colder brackish or restricted seas during the Ordovician Period.