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Examples of other Nemathelminthes. A. The fossil Markuelia sp. from the same time and area in Australia as Shergoldana australiensis (own material); white arrows point to the fronto-marginal, posteriorly pointing soft spines. Black arrow points to caudal spines, which are arranged in two sets on either side. B. Extant macrodasyid gastrotrich Dactylopodola baltica (Remane, 1926) from the Isle of Sylt, Germany. Arrows point to the paired caudal extensions. C. Extant homalorhagid kinorhynch Paracentrophyes praedictus Higgins, 1983, from Belize. Arrows point to the paired tail end with setae (B and C, kindly provided by B. Neuhaus, Berlin).
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Herein, we describe a 145 µm long, three-dimensionally preserved fossil from Middle Cambrian rocks collected in 1986 in the Duchess Embayment, Queensland, Australia. The new, possibly immature form is formally named Shergoldana australiensis gen. et sp. nov. It shares features with minute taxa among the Recent Nemathelminthes, such as the gastrotri...
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... The embryos of Markuelia sp. (Fig. 7A) are much more than one millimetre long when unrolled. They are characterised by a blunt frontal region with possibly soft spines, an annulated body and short caudal region with a paired set of distally curved spines ventrocaudally (Fig. 7A). In light of this morphology, our fossil seems even to be an ontogenetically younger stage than ...
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... The embryos of Markuelia sp. (Fig. 7A) are much more than one millimetre long when unrolled. They are characterised by a blunt frontal region with possibly soft spines, an annulated body and short caudal region with a paired set of distally curved spines ventrocaudally (Fig. 7A). In light of this morphology, our fossil seems even to be an ontogenetically younger stage than the embryo of Markuelia -but is clearly free- living. Likewise, this rules out the possibility that S. australiensis represents a younger stage of Markuelia. The Recent Gastrotricha (Fig. 7B) and Kinorhyncha (Fig. 7C) both are extremely ...
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... with a paired set of distally curved spines ventrocaudally (Fig. 7A). In light of this morphology, our fossil seems even to be an ontogenetically younger stage than the embryo of Markuelia -but is clearly free- living. Likewise, this rules out the possibility that S. australiensis represents a younger stage of Markuelia. The Recent Gastrotricha (Fig. 7B) and Kinorhyncha (Fig. 7C) both are extremely small (70 to 1500 µm). Species about the same size as S. australiensis bear many more features indicative of their developed status, e.g., mouth, anus and the genital opening (see Maas et al. in press for an example of the preservation of a genital opening in an 'Orsten' fossil). Ax (2003), ...
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... curved spines ventrocaudally (Fig. 7A). In light of this morphology, our fossil seems even to be an ontogenetically younger stage than the embryo of Markuelia -but is clearly free- living. Likewise, this rules out the possibility that S. australiensis represents a younger stage of Markuelia. The Recent Gastrotricha (Fig. 7B) and Kinorhyncha (Fig. 7C) both are extremely small (70 to 1500 µm). Species about the same size as S. australiensis bear many more features indicative of their developed status, e.g., mouth, anus and the genital opening (see Maas et al. in press for an example of the preservation of a genital opening in an 'Orsten' fossil). Ax (2003), in the third volume of ...
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... trunk (postseptum) of nematomorph larvae consists of two similarly wide portions, which differ in length. The long anterior part is annulated but otherwise smooth, while the smooth end piece bears two pairs of short spines ventrally (Fig. 9A-B). The tail end of Markuelia sp. also shows paired groups of spines, with two or three in each group (Fig. 7A). If the set-off tail end of S. australiensis could be compared with this, the postseptum would equal the third and fourth regions of S. australiensis together. Likewise, the entire body behind the neck of priapulids would be the same region (Fig. ...
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... the bifid caudal end, comparable structures to those of S. australiensis occur in nematomorph larvae, and also in gastrotrichs and several cycloneuralians. In many gastrotrichs, the tail ends in paired outgrowths (Fig. 7B) bearing several adhesive glands (Schmidt-Rhaesa 2002). Paired paddles occur in loriciferan larvae and in kinorhynchs ( Fig. 7C; Kristensen 2002;Neuhaus & Higgins 2002). In kinorhynchs, the outgrowths represent cuticular spines. The toes of the Higgins larva of Loricifera may enclose adhesive glands in benthic forms (Kristensen 2002). ...
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... the bifid caudal end, comparable structures to those of S. australiensis occur in nematomorph larvae, and also in gastrotrichs and several cycloneuralians. In many gastrotrichs, the tail ends in paired outgrowths (Fig. 7B) bearing several adhesive glands (Schmidt-Rhaesa 2002). Paired paddles occur in loriciferan larvae and in kinorhynchs ( Fig. 7C; Kristensen 2002;Neuhaus & Higgins 2002). In kinorhynchs, the outgrowths represent cuticular spines. The toes of the Higgins larva of Loricifera may enclose adhesive glands in benthic forms (Kristensen 2002). It is unclear whether the structures in S. australiensis are hollow or solid, a terminal pore of a possible gland could not be ...
Citations
... Parasitoid nematomorph larvae have preserved an introvert surrounded by concentric rings of spines (e.g., [14,29]). Such larvae show an overall similarity to Cambrian vermiform larvae with introverts, such as Shergoldana and Orstenoloricus, which can represent larval palaeoscolecidans [30,31]. ...
Nematomorpha (hairworms) is a phylum of parasitic ecdysozoans, best known for infecting arthropods and guiding their hosts toward water, where the parasite can complete its life cycle. Over 350 species of nematomorphs have been described, yet molecular data for the group remain scarce. The few available mitochondrial genomes of nematomorphs are enriched with long inverted repeats, which are embedded in the coding sequences of their genes—a remarkably unusual feature exclusive to this phylum. Here, we obtain and annotate the repeats in the mitochondrial genome of another nematomorph species—Parachordodes pustulosus. Using genomic and transcriptomic libraries, we investigate the impact of inverted repeats on the read coverage of the mitochondrial genome. Pronounced drops in the read coverage coincide with regions containing long inverted repeats, denoting the ‘blind spots’ of short-fragment sequencing libraries. Phylogenetic inference with the novel data reveals multiple disagreements between the traditional system of Nematomorpha and molecular data, rendering several genera paraphyletic, including Parachordodes.
... The Burgess Shale-type Lagerstätten, e.g., the Burgess Shale biota (Conway Morris, 1977), the Chengjiang biota (Hou et al., 2017), and the Sirius Passet biota (Conway Morris et al., 1987;Conway Morris and Peel, 2010), generally preserve macroscopic cycloneuralian fossils, possibly representing adult stages. By contrast, the Orsten-type Lagerstätten (Maas et al., 2006), e.g., the lower Cambrian (Topper et al., 2010) and middle Cambrian (Mü ller and Hinz-Schallreuter, 1993;Maas et al., 2007Maas et al., , 2009) of Australia, the middle Cambrian of southern Scandinavia (Streng et al., 2017), the upper Cambrian Wangcun Lagerstätte (Duan et al., 2012) and the lower Cambrian Zhangjiagou Lagerstätte of China , preserve microscopic cycloneuralian fossils, generally at the millimeter or sub-millimeter scale. These fossils include embryonic (Dong et al., 2004(Dong et al., , 2005, larval (Maas et al., 2007(Maas et al., , 2009, and possible juvenile stages (Duan et al., 2012;Duan and Dong, 2013;Liu et al., 2014Liu et al., , 2019. ...
... By contrast, the Orsten-type Lagerstätten (Maas et al., 2006), e.g., the lower Cambrian (Topper et al., 2010) and middle Cambrian (Mü ller and Hinz-Schallreuter, 1993;Maas et al., 2007Maas et al., , 2009) of Australia, the middle Cambrian of southern Scandinavia (Streng et al., 2017), the upper Cambrian Wangcun Lagerstätte (Duan et al., 2012) and the lower Cambrian Zhangjiagou Lagerstätte of China , preserve microscopic cycloneuralian fossils, generally at the millimeter or sub-millimeter scale. These fossils include embryonic (Dong et al., 2004(Dong et al., , 2005, larval (Maas et al., 2007(Maas et al., , 2009, and possible juvenile stages (Duan et al., 2012;Duan and Dong, 2013;Liu et al., 2014Liu et al., , 2019. In contrast to the generally completely preserved cycloneuralian adults in the Burgess Shale-type Lagerstätten, the juveniles in the Orsten-type Lagerstätten are in most cases fragmented, representing only the trunk part (sometimes with tail end) or the introvert with a part of the trunk (Liu et al., 2019). ...
In a strict sense, palaeoscolecids are a group of cycloneuralian worms (ecdysozoans) characterized by the tessellation of trunk sclerites, which are differentiated into plates, platelets, and microplates. The Wangcun section in western Hunan, South China, which represents the Furongian Series (upper Cambrian), has yielded a rich and diverse collection of palaeoscolecids. However, there is uncertainty about how the morphology and arrangement of their sclerites change during ontogeny and the potential taxonomic implications of these changes. Here, we report new phosphatized trunk fragments from the Wangcun section, which are assigned to Dispinoscolex decorus, Hunanoscolex campus (= Ornatoscolex hunanensis), and Schistoscolex hunanensis. Trunk fragments of the same species with different diameter indicate the presence of several ontogenetic stages, and careful assessment revealed two types of sclerite growth patterns. One is represented by D. decorus and possibly also by S. hunanensis, in which the worm growth is accompanied mainly by the enlargement of the plates, with almost no change in the median annular zones and annulation boundaries. The other type is represented by H. campus, in which the worm growth is accompanied mainly by the widening of the median annular zones and annulation boundaries inserted with continuously more platelets and microplates. Because the specimens originally assigned to H. campus seem to represent late ontogenetic stages of O. hunanensis, we propose that H. campus is a senior synonym of the latter. This study underscores the importance of ontogenetic variation of sclerites for the taxonomy of palaeoscolecids, and highlights the significance of Orsten-type fossils in the study of metazoan ontogeny.
... It remains uncertain, however, as to what triggered such impregnation, but this exceptional type of cuticle preservation affected so far known only arthropods (example references: Maas et al., 2006;Müller, 1985;Walossek, 1985, 1991;Walossek and Müller, 1992; and nemathelminths (e.g. Maas et al., 2007cMaas et al., , 2009Liu et al., 2014;Shao et al., 2018Shao et al., , 2019Zhang et al., 2018). ...
... Scalidophorans are the second group of chitin-cuticle bearing fossils in Orsten-type fossil assemblages, but small three-dimensionally preserved members of this group have, so far, been reported only from Australia and China (e.g. Pratt, 1996, 2008;Zhang et al., 2006a;Maas et al., 2006Maas et al., , 2007aMaas et al., , 2007cMaas et al., , 2009Maas, 2013;Zhang et al., 2018), but neither from Poland, nor from Sweden. To shed more light on this biased record and clearer exclusion from being candidates for being faeces producers, must await further discoveries. ...
The Furongian Słowińska Formation in Poland yielded minute three-dimensionally preserved, phosphatic fossils. Based on shape and structure, two distinct types are identified. The first type comprises sinuously folded, coiled, or spiral string-shaped specimens, interpreted as faecal material, coprolites. The specimens measure between less than one and two mm, the strings being long and against their subcircular to circular cross-section (60–150 μm). Many strings are folded in few to more than 30 regular loops, in this exceptional complexity unknown from any comparable fossil or extant faeces. Fully stretched, such strings may have an estimated length of more than three cm, suggesting continuous production of such faeces and resistance very a longer period after defecation until fossilization. Modelling similar strings indicates that the loops were produced by sidewards swinging of the body end of the producer during forward move. EDS analysis of the strings revealed low silica content, but high amounts of phosphate pointing to a organic-rich muddy bottom, which the producers swallowed and eventually became phosphatized as faeces. The producers of this faeces might have been few millimeter long and benthic, not infaunal worms, yet, none of the putative coprolites can be unquestionably ascribed to a particular animal group. The second type of fossils comprises between 100 and 220 μm long ellipsoidal to spherical forms with a smooth but wrinkled surface. They are interpreted as collapsed and deformed eggs or embryos lacking the egg shell, rather than coprolites made of digested and squeezed remains of possibly phosphatocopid crustaceans, the most abundant component of the Polish and Baltoscandian Orsten-type fossil assemblages. The spheres also have a smooth surface, which in all cases is partly broken off, uncovering an internal mass. This ranges from a small hump of possibly embryonic material in a large void, to a completely round body possibly presenting a late shield-bearing embryo filling the entire space underneath the egg shell. We interpret this second type of fossils as the first evidence of eggs in Orsten-type preservation, most likely belonging to phosphatocopid crustaceans.
... Some free-living forms of Palaeoscolecidae even closely resemble some Nematomorpha (Hou and Bergström 1994), but they are usually interpreted as being early offshoots of the lineage towards Priapulida (Harvey et al. 2010). Shergoldana australensis from the Cambrian of Queensland resembles nematomorph larvae to some degree (Maas et al. 2007), and probably also lived in the meiofauna, similar to kinorhynch cycloneuralians (Nagler and Haug 2015). ...
The fossil record of parasitic helminths is often stated to be severely limited. Many studies have therefore used host constraints to constrain molecular divergence time estimates of helminths. Here we review direct fossil evidence fossil evidence for several of these parasitic lineages belong to various phyla (Acanthocephala, Annelida, Arthropoda, Nematoda, Nematomorpha, Platyhelminthes). Our compilation shows that the fossil record of soft-bodied hel-minths is patchy, but more diverse than commonly assumed. The fossil record provides evidence that ectoparasitic helminths (e.g., pentastomids) have been around since the early Paleozoic, while endoparasitic helminths arose at least during, or possibly even before the late Paleozoic. Nematode lineages parasitizing terrestrial plant and animal hosts have been in existence at least since the Devonian and Triassic, respectively. All major phyla (Acanthocephala, Annelida, Platyhelminthes. Nematoda, Nematomorpha) had evolved endoparasitic lineages at least since the Mesozoic. Interestingly, although parasitism is considered derived within Metazoa, the oldest evidence for Nematoda and Platyhelminthes includes body fossils of parasitic representatives. Furthermore, the oldest fossil evidence of these parasitic lin-eages often falls within molecular divergence time based on host co-evolution suggesting the fossil record of helminths themselves might be just as good or at least complementary (and less circular in justification) to calibration based on host associations. Data also provide evidence for obvious host switches or extinctions,
... Some free-living forms of Palaeoscolecidae even closely resemble some Nematomorpha (Hou and Bergström 1994), but they are usually interpreted as being early offshoots of the lineage towards Priapulida (Harvey et al. 2010). Shergoldana australensis from the Cambrian of Queensland resembles nematomorph larvae to some degree (Maas et al. 2007), and probably also lived in the meiofauna, similar to kinorhynch cycloneuralians (Nagler and Haug 2015). ...
The fossil record of parasitic helminths is often stated to be severely limited. Many studies have therefore used host constraints to constrain molecular divergence time estimates of helminths. Here we review direct fossil evidence for several of these parasitic lineages belong to various phyla (Acanthocephala, Annelida, Arthropoda, Nematoda, Nematomorpha, Pentastomida, Platyhelminthes). Our compilation shows that the fossil record of soft-bodied helminths is patchy, but more diverse than commonly assumed. The fossil record provides evidence that ectoparasitic helminths (e.g., worm-like pentastomid arthropods) have been around since the early Paleozoic, while endoparasitic helminths (cestodes) arose at least during, or possibly even before the late Paleozoic. Nematode lineages parasitizing terrestrial plant and animal hosts have been in existence at least since the Devonian and Triassic, respectively. All major phyla (Acanthocephala, Annelida, Platyhelminthes. Nematoda, Nematomorpha) had evolved endoparasitic lineages at least since the Mesozoic. Interestingly, although parasitism is considered derived within Metazoa, the oldest evidence for Nematoda and Platyhelminthes includes body fossils of parasitic representatives. Furthermore, the oldest fossil evidence of these parasitic lineages often falls within molecular divergence time estimates based on host co-evolution suggesting the fossil record of helminths themselves might be just as good or at least complementary (and less circular in justification) to calibration based on host associations. Data also provide evidence for obvious host switches or extinctions, which cautions against models of pure co-divergence where use of host calibrations to constrain divergence time estimates may be considered.
... The introvert and pharynx of Mafangscolex thus provide the first clear indication of proboscis morphology in Palaeoscolecida sensu stricto, establishing a six-fold symmetry and a construction that conforms to the wider ground plan shared by the majority of Cambrian ecdysozoan worms (Conway Morris, 1977): an introvert with multiple circlets of posterior-directed hooks, a ring of coronal spines, an unarmoured proximal pharynx and quincuncially arranged teeth with a gradation of morphology in the distal pharynx. The single circlet of introvert hooks reconstructed in Scathascolex (Smith, 2015) is thus not representative of palaeoscolecids more broadly, and conceivably connects this taxon to nematomorph-like taxa with a single ring of introvert teeth (Maas et al. 2007). In view of the faint preservation of the coronal spines in our material, we postulate that the reported absence of equivalent structures in Guanduscolex (Hu et al. 2008) (and the type material of Mafangscolex) likely represents a lack of preservational fidelity rather than a genuine absence; this would leave the problematic Ancalagon as the only Cambrian ecdysozoan worm to lack coronal spines. ...
... Because six-fold symmetry is not inherent to the function of the introvert, this detail is less straightforward to attribute to convergence. A hexaradially arranged introvert was likely the primitive condition for Ecdysozoa: not only does it characterize all ecdysozoans from the Fortunian (earliest Cambrian) period (Liu et al. 2014(Liu et al. , 2019, but its vestiges are apparent in the majority of extant phyla, including stem-and crown-group loriciferans (Sørensen et al. 2008;Peel et al. 2013), nematomorphs, larval nematodes (despite the lack of introvert armature) (Maas et al. 2007) and certain panarthropods, in the form of the six oral papillae of Aysheaia (Whittington, 1978) and the six oral plates of tardigrades (Boesgaard & Kristensen, 2001;Biserova & Kuznetsova, 2012;Guidetti et al. 2013). ...
Palaeoscolecid worms are widespread in the Palaeozoic period, and are of key importance to understanding the emergence of moulting animals (superphylum Ecdysozoa). However, palaeoscolecids lack a diagnostic set of morphological characters, and as such are unlikely to form a natural (monophyletic) group. Consequently, detailed anatomical study of individual taxa is necessary in order to evaluate the phylogenetic significance of palaeoscolecids. New specimens of Mafangscolex from the Cambrian Stage 3 Xiaoshiba Lagerstätte in Kunming, China, provide the first detailed account of a proboscis in Palaeoscoelcida sensu stricto , a core group of palaeoscolecids characterized by having a tessellating scleritome of phosphatic plates and platelets. The eversible mouthparts of Mafangscolex comprise an armoured, hexaradially symmetrical introvert, a ring of coronal spines and quincuncially arranged pharyngeal armature, with a range of tooth morphologies. Taken together, this configuration strikingly resembles the proboscis arrangement inferred for the ancestral ecdysozoan. The six-fold symmetry represents an important difference from the pentaradial priapulan proboscis. The retention of key aspects of the ancestral ecdysozoan body plan suggests that palaeoscolecids represent a useful window on the earliest stages of ecdysozoan evolution.
... Of these, only worms of the long, worm-like form have trunk annuli. Accordingly, it is proposed here that the Cambrian small-bodied cycloneuralians can also be divided into four groups: loricate form (Maas et al., 2009;Harvey and Butterfield, 2016), kinorhynch-like form (Zhang et al., 2015), nematomorph larva-like form (Maas et al., 2007b), and priapulid-like form Liu et al., 2014bLiu et al., , 2019Dong et al., 2010;Shao et al., 2016). The priapulid-like form can be compared with the long, worm-like cycloneuralians from the Maotianshan Shale biota (Maas et al., 2007a), because they both have a relatively high body length to width ratio (> 10), with dozens or even hundreds of homonomous trunk annuli (microannuli). ...
Kinorhyncha is a cycloneuralian phylum with about 240 extant species, and it was not until 2015 that the first and only fossil kinorhynch species Eokinorhynchus rarus was reported. Here, we describe a new scalidophoran animal, Zhongpingscolex qinensis gen. et sp. nov., from the Cambrian Fortunian Kuanchuanpu Formation at Zhangjiagou section, southern Shaanxi Province, South China. The holotype and only specimen possesses morphology comparable to that of E. rarus. They both possess heterogeneous trunk annuli, and compared with E. rarus, Z. qinensis gen. et sp. nov. lacks a neck. Phylogenetic analysis resolves Z. qinensis gen. et sp. nov. as the sister group of E. rarus, both constituting stem-lineage derivatives of Kinorhyncha. The evolutionary scenario from the last common ancestor of crown-group Scalidophora to the last common ancestor of total-group Kinorhyncha includes the acquisition of a much shortened body with a relatively low body length to width ratio, heterogeneous trunk annuli, and macroannuli with simple armatures. The spines, large spinose sclerites, and annular rings of rectangular plates are autapomorphic to E. rarus, and segments (zonites) with independent cuticular plates as in crown-group kinorhynchs were evolved later.
... The onychophoran lobopods (also called oncopods) resemble those of Cambrian lobopodians in several respects, including their fleshy and unjointed nature, the overall shape, the presence of distal claws and the existence of ventral pads functioning as walking soles [9,23,29,30]. These similarities suggest that the functional morphology of walking limbs in Cambrian lobopodians may have been indeed comparable to that of extant onychophorans [5,19]. ...
Segmental, paired locomotory appendages are a characteristic feature of Panarthropoda—a diversified clade of moulting animals that includes onychophorans (velvet worms), tardigrades (water bears) and arthropods. While arthropods acquired a sclerotized exoskeleton and articulated limbs, onychophorans and tardigrades possess a soft body and unjointed limbs called lobopods, which they inherited from Cambrian lobopodians. To date, the origin and ancestral structure of the lobopods and their transformation into the jointed appendages are all poorly understood. We therefore combined high-resolution computed tomography with high- speed camera recordings to characterize the functional anatomy of a trunk lobopod from the onychophoran Euperipatoides rowelli. Three-dimensional reconstruction of the complete set of muscles and muscle fibres as well as non- muscular structures revealed the spatial relationship and relative volumes of the muscular, excretory, circulatory and nervous systems within the leg. Locomotory movements of individual lobopods of E. rowelli proved far more diverse than previously thought and might be governed by a complex interplay of 15 muscles, including one promotor, one remotor, one levator, one retractor, two depressors, two rotators, one flexor and two constrictors as well as muscles for stabilization and haemolymph control. We discuss the implications of our findings for understanding the evolution of locomotion in panarthropods.
... As cuticle-bearing animals, cycloneuralians have relatively strong fossilisation potential relative to other taxa with simple epidermis, and thus not surprisingly left abundant fossils in the Cambrian Konservat-Lagerstätten (Maas, 2013). Previously reported Cambrian cycloneuralians occur mainly in Stage 3 and younger strata (Maas, 2013), such as the typical Burgess Shale-type Lagerstätten (Conway Morris, 1977;Briggs et al., 1994;Hou et al., 2017) and the Orsten-type Lagerstätten (Liu et al., 2014a(Liu et al., , 2019Maas et al., 2007a;Shao et al., 2018;Zhang et al., 2015Zhang et al., , 2018, with minor occurrences as Small Carbonaceous Fossils (Harvey and Butterfield, 2017;Slater et al., 2018). In Stage 2, only a single species, known exclusively from embryos, was reported (Bengtson and Yue, 1997). ...
... lacks loricae at this ontogenetic stage, it is different from the loricate Eolorica deadwoodensis Harvey and Butterfield, 2017. Shergoldana australiensis Maas et al., 2007a from the middle Cambrian of Australia is known only from its small, possibly earliest larval semaphoront/larval stage, measuring no more than 120 µm in length. Its subdivision into (intruded) pharynx and four more body regions sets it off until now from the new species and all other described Cambrian fossils assigned to Cycloneuralia, but its shared features like the sclerites with spines and bifid trunk end make it clearly an interesting form for future discussions of the basic set of features of this group and further evolutionary developments of its ingroup taxa. ...
Although morphology-based phylogenetic analyses and molecular data suggested that the cycloneuralians might have emerged in the Ediacaran Period, the oldest known fossil remains of cycloneuralians were first reported from the Cambrian Fortunian Stage of South China, and to date four genera and species as well as nine in- determinate forms have been described. Here, we report the latest discoveries of cycloneuralians from the Fortunian Kuanchuanpu Formation at Zhangjiagou Lagerstätte, Dahe Village, Xixiang County, southern Shaanxi Province, South China. A new genus and species Dahescolex kuanchuanpuensis n. gen. n. sp. is described, and a previously reported genus and species Eopriapulites sphinx is re-described. Dahescolex kuanchuanpuensis n. gen. n. sp. is suggested to be a stem-lineage derivative of Scalidophora, whereas E. sphinx may represent a stem-lineage derivative of Cycloneuralia. From the fragments discovered, the new specimens are suggested to have reached millimeters in dimension, and the original individuals are estimated to have dimensions in centimeter, hence falls within the size range of macrobenthos. Therefore, at least some of the Fortunian cycloneuralians can be considered macrobenthic, and it is suggested here that the Cycloneuralia may have originated in the Fortunian macrobenthos.
... Among the known fossils from Orsten-type Lagerstätten are numerous larval specimens of arthropods, mainly early crustaceans and eucrustaceans (e.g. Haug, J. T. et al. 2009a; recent summary in Haug, C. et al. 2014), but also of cycloneuralian worms (Maas et al. 2007Haug, J. T. et al. 2009b;Haug, J. T. & Haug, C. 2015). While most of these forms could be unequivocally treated systematically (due to a lack of possible adult forms), some of them described as species (or "higher" monophyletic taxa) may indeed be larval representatives of species already known from other fossils (e.g. ...
Early post-embryonic stages of arthropods are rarely found in the fossil record. They seem even more rarely reported in literature, possibly as it is more difficult to establish new species based on these specimens. Here we report two immature specimens of polyxenidan myriapods (Diplopoda, Polyxenida) preserved in Saxonian amber (Eocene). Specimen 1 represents a stage I individual with only three pairs of trunk appendages, the collum and three additional tergites. It is interpreted as a representative of the polyxenidan ingroup Polyxenidae. Specimen 2 represents a stage II individual with four pairs of trunk appendages, the collum and three well-sclerotised tergites. It is interpreted as a representative of the polyxenidan ingroup Synxenidae. We additionally discuss the challenges of further systematically interpreting immatures and fossil polyxenidans in general. We also discuss how the further exploration of data of immature polyxenidans, extant and fossil, has the potential to improve our understanding of their evolution and biology.
