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An early arthropod Isoxys curvirostratus (Vannier and Chen, 2000) from the Lower Cambrian Chengjiang biota, South China from Erjie section (A–C, E) and from Jianshan section (D). A. EJ0423; A 1 , complete specimen showing the outline of carapace, lamellae of the exopod; A 2 , camera−lucida drawing of A 1 . B. EJ0424, showing the eye spheres, frontal appendage, trunk and the traces of trunk appendages. C. EJ0422, immature specimen showing 14 trunk somites. D. JS154; D 1 , showing eye spheres, the number of the trunk somites and location of appendages; D 2 , camera−lucida drawing of D 1 . E. EJ0407; E 1 , showing the eye sphere and stalk, appendages in relief and the trunk; E 2 , camera−lucida drawing of E 1 . Abbreviations: es, eye stalk; ex, exopod; fa, frontal appendage; gl, gill lamellae of exopod; le, lateral eye; pr, proximal part of appendage; ps, posterior spine; te, telson; ti, trunk inclusion; 1–14, numbered trunk appendage.
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An updated reconstruction of the body plan, functional morphology and lifestyle of the arthropod Isoxys curvirostratus is proposed, based on new fossil specimens with preserved soft anatomy found in several localities of the Lower Cambrian Chengjiang Lagerstätte. The animal was 2–4 cm long and mostly encased in a single carapace which is folded dor...
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... the gaps between two adjoining appendages (see Fig. 2E 1 ). Accordingly, the number of somites can be estimated at 14 on the basis of limbs which are evident in JS154 and the counterpart of JS0014 (Fig. 2C, D), although the intersomitic boundaries of the trunk are not evident in Isoxys curviro− stratus. Body attachment is highly hypothetical since no direct evidence of adductor muscle scars has been found. Speci− mens preserved in lateral aspect, whose posterior trunk hung down and protruded from the ventral margin of the carapace, while ...
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... in the present material. Eye.-In five specimens, pairs of large lateral eyes are pre− served in life position as dark, round impressions, about one seventh of the valve height in diameter, extending beyond the anterior margin of carapace (Figs. 2B-E, 3A 1 , 4B 1 ). In JS0014, two individual layers can be recognized from a sin− gle eye sphere ( Fig. 3A 2 ); the light external layer probably represents the cornea, and the dark internal core is best inter− preted as the remains of retinulae units. The eye stalk, unseg− mented, is visible in two specimens, unequivocally in EJ0404 (Fig. 4B 1 ). The length of the stalk is equal to the di− ameter of the eye and its width is about one fifth of ...
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... to the dis− tal part. The proximal part of the stalk is located at the pre− sumed cephalon (ocular segment). branes on the right appendage (Fig. 3A 4 ). The proximal seg− ment seems different from the distal ones in shape, possibly representing the basal segment. Stout tooth−like outgrowths are visible in the segments of the left appendage ( Fig. 2A 4 ). In JS0008, five segments of the frontal appendage are also indicated by the indisputable outgrowths (Fig. 3A 1 ). The out− line of the frontal appendage, followed by the eyes, is pre− served in EJ0424 (Fig. 4B). The proximal part of the frontal appendage is present in some specimens, for example in EJ0407, and apparently shows no sign ...
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Citations
... The close packed nature of the soft tissues, their proximal curvature, and the change in angle at the same distance from the dorsal margin of the carapace indicates that these features probably represent thoracic segments with pleurae or ventral appendages. Comparable features, with ventral appendages extending as far or slightly beyond the carapace margin, have been reported from a range of Cambrian euarthropods with bivalved carapaces from different deposits including Balhuticaris voltae (Burgess Shale; [56]), Clypecaris pteroidea (Chengjiang; [57]), Clypecaris serrata (Xiaoshiba; [58]), Isoxys curvirostratus (Chengjiang; [59,60]); Pauloterminus spinodorsalis (Sirius Passet; [61]), Vermontcaris montcalmi (Parker Quarry; [62]). In Tuzoia, appendages do not appear to extend as far as the margin of the carapace (e.g. ...
Deposits preserving non-biomineralized tissues and animalsprovide an unrivalled opportunity to study the evolution andradiation of early animal life. Numerous sites of Cambrian ageare known from North America (Laurentia) and South China(East Gondwana), which provide a high resolution pictureof the fauna at low latitudes. By contrast, our knowledge ofCambrian animals from higher latitudes is relatively poor.This patchiness in our knowledge of animal life during theradiation of animals in the Cambrian period limits our abilityto understand and detect palaeogeographic trends and doesnot provide a full appreciation of animal diversity at thistime. Here we report a new middle Cambrian (Drumian)site preserving lightly sclerotized euarthropod carapaces,sponges and palaeoscolecids near the village of Mesones deIsuela in the Iberian Chains (Spain). We describe threebivalved euarthropod carapace morphs, two comparable tothose described from the only other high latitude Drumiandeposit, the Jince Formation (Czechia), and one distinct fromprevious discoveries. These new findings highlight theimportance of high latitude Gondwana Konservat Lagerstattenfor understanding the palaeogeographical aspect of theradiation of early animals and suggest that bivalvedeuarthropods at high latitudes were larger than those at lowerlatitudes during the Cambrian.
... Se piensan que podrían ser glándulas venenosas, ya que se asemejan en gran medida a las presentes en arácnidos actuales. Estas estructuras difieren en tamaño y ubicación de las glándulas digestivas, ya que son más pequeñas y se sitúan dentro del cefalón (Fu et al., 2011b). ...
... El veneno podía administrarse por un conducto dentro de los apéndices de agarre. Cuando la presa fuese envenenada hasta la muerte, I. curvirostratus podía bombear enzimas digestivas desde el intestino hacia la presa y luego succionar el fluido hidrolizado, dejando una cáscara casi intacta (Fu et al., 2011b). Estas observaciones además demuestran la presencia de estrategias de caza con veneno ya el Cámbrico inferior (Fu et al., 2011b). ...
... Cuando la presa fuese envenenada hasta la muerte, I. curvirostratus podía bombear enzimas digestivas desde el intestino hacia la presa y luego succionar el fluido hidrolizado, dejando una cáscara casi intacta (Fu et al., 2011b). Estas observaciones además demuestran la presencia de estrategias de caza con veneno ya el Cámbrico inferior (Fu et al., 2011b). ...
Palaeontology is dedicated to the scientific study of the past of life on Earth
through, among other elements, fossils. The fossils are found in several types of
deposits, and of these the Konservat Lagerstätten stand out, where there are
specimens preserved in exceptional conditions. The genus Isoxys is mainly
known thanks Cambrian to deposits of this nature spread all over the world:
China, Greenland, USA... In this period one of the most important biological
events in the history of the Earth took place: the Cambrian radiation. In this
radiation all the animal phyla that we currently have nowadays originated, and
some that have not been preserved to these days. The arthropods, a very
numerous phyla both now and then, are very interesting since there were animals
very different from those we find now. A curious group within the Cambrian
arthropods is that of the bivalve arthropods, to which Isoxys belonged. It had a
characteristic shell with two spines on the front and back each and a specific
pattern of ornamentation. It is known to inhabit well-lit waters and to have had a
cosmopolitan distribution, partially governed by temperature. It should be noted
that, in the Cambrian, there were no continents as we know them now, but there
was a super continent (Gondwana) and several continents scattered in the ocean
(Laurentia, Siberia...).
... 1. Introduction †Isoxys arthropod is a widely distributed taxon of the Cambrian marine ecosystem, with a large bivalved carapace bearing two prominent cardinal spines, which is occurred in Cambrian Series 2 and 3 and has a widespread paleogeographical distribution (Williams et al., 1996;Vannier and Chen, 2000;Stein et al., 2010;Fu et al., 2011;Legg and Vannier, 2013;Liu et al., 2018). Hitherto, up to 22 species of †Isoxys have been recorded from Australia (Glaessner, 1979;García-Bellido et al., 2009a), North America (Simonetta and Delle Cave, 1975;Butterfield and Nicholas, 1994;Williams et al., Frontiers in Ecology and Evolution 1996; Briggs et al., 2008;García-Bellido et al., 2009b), North Greenland (Stein et al., 2010;Nielsen et al., 2017), France (Vannier et al., 2005), Spain (Richter and Richter, 1927;Wang, 2014), Russia (Ivantsov, 1990(Ivantsov, , 2005, and China (Hou, 1987;Shu et al., 1995;Luo et al., 1999Luo et al., , 2006Luo et al., , 2008Zhao et al., 2005Zhao et al., , 2011Wang et al., 2010;Fu et al., 2011Fu et al., , 2014Wen et al., 2015;Liu et al., 2018;Du et al., 2020). ...
... 1. Introduction †Isoxys arthropod is a widely distributed taxon of the Cambrian marine ecosystem, with a large bivalved carapace bearing two prominent cardinal spines, which is occurred in Cambrian Series 2 and 3 and has a widespread paleogeographical distribution (Williams et al., 1996;Vannier and Chen, 2000;Stein et al., 2010;Fu et al., 2011;Legg and Vannier, 2013;Liu et al., 2018). Hitherto, up to 22 species of †Isoxys have been recorded from Australia (Glaessner, 1979;García-Bellido et al., 2009a), North America (Simonetta and Delle Cave, 1975;Butterfield and Nicholas, 1994;Williams et al., Frontiers in Ecology and Evolution 1996; Briggs et al., 2008;García-Bellido et al., 2009b), North Greenland (Stein et al., 2010;Nielsen et al., 2017), France (Vannier et al., 2005), Spain (Richter and Richter, 1927;Wang, 2014), Russia (Ivantsov, 1990(Ivantsov, , 2005, and China (Hou, 1987;Shu et al., 1995;Luo et al., 1999Luo et al., , 2006Luo et al., , 2008Zhao et al., 2005Zhao et al., , 2011Wang et al., 2010;Fu et al., 2011Fu et al., , 2014Wen et al., 2015;Liu et al., 2018;Du et al., 2020). It is widely distributed in the continental shelf, as well as in deep-water slope areas, recovered from deposits ranging between 30° N and 30° S paleolatitude (Vannier and Chen, 2000;Vannier et al., 2009;Huang and Wang, 2014;Liu et al., 2018). ...
... The morphological terms used for the description of †Isoxys minor are in general accordance with those used by previous authors to describe the morphology of Isoxys (Williams et al., 1996;Vannier and Chen, 2000;García-Bellido et al., 2009a;Fu et al., 2011;Aria and Caron, 2015). ...
†Isoxys is a worldwide distributed bivalved arthropod known almost exclusively from Cambrian Burgess Shale-type Lagerstätten. Outline analyses using 34 specimens of the iconic large bivalved arthropod †Isoxys minor from the Cambrian Stage 3 (~518 Ma) Qingjiang biota and the Cambrian Stage 4 Guanshan biota, interpret that they are the same species and there is a very slight difference in the shape of the outlines of the carapaces between the two biotas. This suggests that environment might be driving intraspecific variation. Quantitative analysis of shape changes during growth using 51 specimens of †I. minor from the Qingjiang biota, reveals that its valves gradually elongate and the ratio of cardinal spines and spherical eyes relative to the valve length significantly decreases during postembryonic development. †I. minor has proportionally large cardinal spines and eyes in the earliest stages, and this allometric growth is beneficial for self-protection and foraging, which may have improved the survival rate of individuals with these characters. In addition, two of the specimens document the evidence of brood care in †I. minor, and the egg cluster occupies almost the entire dorsal region under the carapace. Compared to other early Paleozoic egg-carrying arthropods, †I. minor broods have the highest number (~300 per clutch) of small (Ø, ~0.5 mm) eggs. Since the ovigerous individuals are almost half the size of the adults, †I. minor may have possessed reproductive ability during the early life stage. The results indicate that spines played an antipredatory role for †I. minor, and that it followed an r-strategy of reproducing with many individuals at an early stage. †I. minor also represents the earliest diverging arthropod from which brood care has been documented.
... The phylogenetic placement of Fengzhengia mamingae in the parsimony analysis is supported by the absence of circumoral structures in a radial arrangement, the presence of post-ocular tergal sclerotisation in the head, the absence of posteriormost lateral processes with lanceolate tips, the presence of arthropodised trunk appendages, and the presence of jointed legs or endopodites-characters 37, 75, and 146, 167, and 249, respectively . The Bayesian analysis, which reconstructs F. mamingae in an intermediate position between the earliest branching deuteropod, K. zhangi, and all other deuteropods, is supported by the absence of frontal-most appendages with endites bearing well-developed auxiliary spinescharacter 198 , which are present in radiodonts, K. zhangi, and megacheirans, but absent in isoxyids (e.g., Fu et al., 2011a;Legg and Vannier, 2013) and other Cambrian euarthropods (Hou et al., 2017). ...
We describe Fengzhengia mamingae gen. et sp. nov., a new euarthropod from the lower Cambrian (Series 2, Stage 3) Chengjiang Lagerstätte, Southwest China. Fengzhengia mamingae possesses prominent frontal appendages, stalked, circular eyes, a simple, sub-triangular head shield, and a trunk with 15 tergites, the anterior nine each bearing a single medial axial spine. Limited evidence suggests biramous trunk appendages with paddle-shaped exopods. At the posterior end is a sub-triangular region, possibly a pygidium, articulated with a tail fan. The frontal appendage of F. mamingae resembles those of certain ‘great appendage’ arthropods and Isoxys. We test the affinities of F. mamingae by parsimony and Bayesian analyses and tentatively suggest that it is an early branch of Deuteropoda. We suggest that F. mamingae may have been a nektobenthic scavenger or predator, and its dorsal exoskeleton is notable for exhibiting defensive spines.
... Early euarthropod evolution involved a major transition from lobopodian-like taxa [03, 04, 05] to organisms featuring a fully sclerotized trunk (arthrodization) and limbs (arthropodization) [02, 06, 07, 08]. However, the precise origin of arthropodization remains controversial because some of the earliest branching euarthropods possess a broad dorsal carapace that obscures critical details of the trunk and appendage organization [09,10,11,12,13,14,15]. Here, we demonstrate the presence of fully arthropodized ventral appendages in the upper stem-group euarthropod Isoxys curvirostratus from the early Cambrian Chengjiang biota in South China. ...
... Each biramous limb bears an endopod with more than 12 well-de ned podomeres, and an exopod consisting of a slender shaft carrying approximately a dozen paddle-shaped lamellae. Our ndings clarify the enigmatic appendicular organization of Isoxys, one of the most ubiquitous euarthropods in Cambrian Burgess Shale-type deposits worldwide [01,10,11,12,14,15, 16,17, 18]. Critically, our new material shows that the trunk of I. curvirostratus was not arthrodized. ...
... Among this paraphyletic grade of Cambrian bivalved euarthropods, the isoxyids have been repeatedly compared with radiodonts based on the presence of a pair of raptorial frontal appendages [07, 14,15,19,20]. Despite exceptional soft-tissue preservation in isoxyids including the stalked eyes and paired gut diverticulae, the detailed morphology of their body and biramous appendages remains poorly understood, generally obscured by the dorsal carapace covering the entire body [10,11,12,14,15,17,18,26]. The Burgess Shale Surusicaris has some of the bestpreserved biramous trunk appendages in isoxyids described to date [15], interpreted as weakly sclerotized and simple, annulated limbs with an elongate exopod bearing marginal setae. ...
The Cambrian fossil record has produced remarkable insights into the origin of euarthropods, particularly the evolution of their versatile body plan of segments bearing specialized, jointed appendages for different functions including feeding and locomotion [01, 02]. Early euarthropod evolution involved a major transition from lobopodian-like taxa [03, 04, 05] to organisms featuring a fully sclerotized trunk (arthrodization) and limbs (arthropodization) [02, 06, 07, 08]. However, the precise origin of arthropodization remains controversial because some of the earliest branching euarthropods possess a broad dorsal carapace that obscures critical details of the trunk and appendage organization [09, 10, 11, 12, 13, 14, 15]. Here, we demonstrate the presence of fully arthropodized ventral appendages in the upper stem-group euarthropod Isoxys curvirostratus from the early Cambrian Chengjiang biota in South China. Micro-computed tomography reveals the detailed three-dimensional structure of the biramous appendages in I. curvirostratus for the first time. In addition to the raptorial frontal appendages I. curvirostratus also possesses two batches of morphologically distinct biramous limbs, with the first batch consisting of four pairs of short cephalic appendages bearing prominent endites with a feeding function, followed by a second batch of elongate trunk appendages for locomotion. Each biramous limb bears an endopod with more than 12 well-defined podomeres, and an exopod consisting of a slender shaft carrying approximately a dozen paddle-shaped lamellae. Our findings clarify the enigmatic appendicular organization of Isoxys, one of the most ubiquitous euarthropods in Cambrian Burgess Shale-type deposits worldwide [01, 10, 11, 12, 14, 15, 16, 17, 18]. Critically, our new material shows that the trunk of I. curvirostratus was not arthrodized. The phylogenetic position of isoxyiids as possibly the earliest branching members of Deuteropoda [01, 02, 07, 15, 19], suggests that arthropodized biramous appendages evolved before the pattern of full trunk arthrodization that characterizes most extant and extinct members of this successful animal phylum.
... However, while Isoxys carapaces appear to show adaptations for hydrodynamic streamlining, interspecific differences in both carapace asymmetry and spine lengths (e.g. figure 2), as well as soft parts, suggest that different species may have occupied distinct niches, including some much closer to the seafloor [21]. ...
... We chose to undertake a two-dimensional analysis to conserve computational resources and minimize errors in the modelled geometries (the exact three-dimensional shape is unknown for most taxa). This is justified because undeformed Isoxys specimens preserved in dorsal view show a narrow profile [16,21,27,28]. Propulsion during swimming derived from movement of the ventral appendages, and not from flapping of the bivalve carapace [15,27]. ...
... Isoxys taxa clustering with Surusicaris ( figure 3) generate positive lift, but do not generate negative lift ( figure 4). This supports suggestions of previous workers that these Isoxys species may have occupied a hyperbenthic (1-10 m above the seafloor) and/or nektobenthic [21] niche, perhaps moving vertically short distances in the water column [15,19,35]. Vertical movement would be achieved by altering the angle of attack to produce lift force greater than (ascent), equal to (horizontal swimming), or less than (descent) the impact of their negative buoyancy. ...
The biological pump is crucial for transporting nutrients fixed by surface-dwelling primary producers to demersal animal communities. Indeed, the establishment of an efficient biological pump was likely a key factor enabling the diversification of animals over 500 Myr ago during the Cambrian explosion. The modern biological pump operates through two main vectors: the passive sinking of aggregates of organic matter, and the active vertical migration of animals. The coevolution of eukaryotes and sinking aggregates is well understood for the Proterozoic and Cambrian; however, little attention has been paid to the establishment of the vertical migration of animals. Here we investigate the morphological variation and hydrodynamic performance of the Cambrian euarthropod Isoxys . We combine elliptical Fourier analysis of carapace shape with computational fluid dynamics simulations to demonstrate that Isoxys species likely occupied a variety of niches in Cambrian oceans, including vertical migrants, providing the first quantitative evidence that some Cambrian animals were adapted for vertical movement in the water column. Vertical migration was one of several early Cambrian metazoan innovations that led to the biological pump taking on a modern-style architecture over 500 Myr ago.
... However, Duplapex has a spinose ventral margin, which is not present in Isoxys. Its eye stalks are fleshy and annulated, whereas those of Isoxys are slender and smooth (Fu et al. 2011). The micro-reticulation ornamentation on Duplapex is larger than that on Isoxys (e.g. ...
The Cambrian Burgess Shale–type fossil Lagerstätten play a crutial role in revealing the origin and early evolution of arthropods. Tuzoiidae, one of the important bivalved arthropod groups, occupied a very important ecological niche in the Cambrian marine ecosystem. Here we describe a new taxon, Duplapex anima gen. et. sp. nov., in the family Tuzoiidae, on the basis of four exceptionally preserved specimens from the early Cambrian (Stage 3) Qingjiang biota of Hubei, South China. Duplapex is characterized by an ornament bivalved carapace, the ventral notch (vno) and doublure spine (dsp) of the valve, a pair of compound eyes connected by the fleshy annulated eye stalks. Despite having an unusual morphology for the group, the new taxon is recognized as a tuzoiid arthropod and indicates that these problematic euarthropods possessed a greater degree of morphological disparity than previously considered. D. anima , as well as the new reported Tuzoia. sp. from the Fandian biota, represent the oldest occurrence of Tuzoiidae, extending its stratigraphic range to Cambrian stage 3 and expanding the palaeobiographic distribution of the group to the northern border of Yangtze Platform.
Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosion
... 1c, 2g and Extended Data Figs. 1d, e, 2b, d, f, i, 4a-g) are features of megacheirans 14 (Fig. 2j and Extended Data Fig. 7a-f, h), great-appendage bivalved euarthropods 15 and isoxyids 16,17 (Extended Data Fig. 7j-o). The presence of auxiliary enditic spines on the frontalmost appendages of radiodonts (arrowheads in Fig. 2e, f), Kylinxia (arrowheads in Fig. 2h, i) and megacheirans (Fig. 2k-m and Extended Data Fig. 7d-i) strengthens the morphological similarities of the frontalmost appendages among these taxa, because such auxiliary enditic spines are absent in isoxyids 16,17 and other Cambrian euarthropods 18 (Extended Data Fig. 7j-o). ...
... 1d, e, 2b, d, f, i, 4a-g) are features of megacheirans 14 (Fig. 2j and Extended Data Fig. 7a-f, h), great-appendage bivalved euarthropods 15 and isoxyids 16,17 (Extended Data Fig. 7j-o). The presence of auxiliary enditic spines on the frontalmost appendages of radiodonts (arrowheads in Fig. 2e, f), Kylinxia (arrowheads in Fig. 2h, i) and megacheirans (Fig. 2k-m and Extended Data Fig. 7d-i) strengthens the morphological similarities of the frontalmost appendages among these taxa, because such auxiliary enditic spines are absent in isoxyids 16,17 and other Cambrian euarthropods 18 (Extended Data Fig. 7j-o). ...
... It is notable that the antennae in some artiopodans 18,27 ('E1' in Fig. 3a and Extended Data Fig. 7p, q) and hymenocarines 28 ('E3' in Fig. 3a) possess paired needle-shaped enditic spines and these have been interpreted to have a predatory function. However, almost identical antennal forms are present in isoxyids such as Isoxys volucris and Isoxys auritus 17,29 ('D3' in Fig. 3a and Extended Data Fig. 7l-o), whereas the frontalmost appendages of other isoxyids exhibit less antenniform features 16,17,30 ('D1' and 'D2' in Fig. 3a and Extended Data Fig. 7j, k). Given the intermediate position of Isoxyida between the deuteropods with raptorial frontalmost appendages and those with typical antennae on our trees ( Fig. 3a and Extended Data Fig. 9), the remarkable morphological variations shown by isoxyid frontalmost appendages indicate that the first antennae of Mandibulata might have been derived from raptorial prototypes resembling those in Isoxyida ('D1'-'D3' in Fig. 3a). ...
Resolving the early evolution of euarthropods is one of the most challenging problems in metazoan evolution1,2. Exceptionally preserved fossils from the Cambrian period have contributed important palaeontological data to deciphering this evolutionary process3,4. Phylogenetic studies have resolved Radiodonta (also known as anomalocaridids) as the closest group to all euarthropods that have frontalmost appendages on the second head segment (Deuteropoda)5–9. However, the interrelationships among major Cambrian euarthropod groups remain disputed1,2,4,7, which impedes our understanding of the evolutionary gap between Radiodonta and Deuteropoda. Here we describe Kylinxia zhangi gen. et. sp. nov., a euarthropod from the early Cambrian Chengjiang biota of China. Kylinxia possesses not only deuteropod characteristics such as a fused head shield, a fully arthrodized trunk and jointed endopodites, but also five eyes (as in Opabinia) as well as radiodont-like raptorial frontalmost appendages. Our phylogenetic reconstruction recovers Kylinxia as a transitional taxon that bridges Radiodonta and Deuteropoda. The most basal deuteropods are retrieved as a paraphyletic lineage that features plesiomorphic raptorial frontalmost appendages and includes Kylinxia, megacheirans, panchelicerates, ‘great-appendage’ bivalved euarthropods and isoxyids. This phylogenetic topology supports the idea that the radiodont and megacheiran frontalmost appendages are homologous, that the chelicerae of Chelicerata originated from megacheiran great appendages and that the sensorial antennae in Mandibulata derived from ancestral raptorial forms. Kylinxia thus provides important insights into the phylogenetic relationships among early euarthropods, the evolutionary transformations and disparity of frontalmost appendages, and the origin of crucial evolutionary innovations in this clade.
... These include taxa with soft anatomy preservation that are instrumental to elucidating early euarthropod evolution (e.g., Hou and Bergstrӧm, 1997;Stein and Selden, 2011;Chen et al., 2019). Among these, arthropods with a grasping appendage, the so-called great or frontal appendages, are iconic animals of the Chengjiang biota (e.g., Chen et al., 2004;Liu et al., 2007;Fu et al., 2011;Legg and Vannier, 2013;Cong et al., 2014). ...
Bushizheia yangi gen. et sp. nov. is a euarthropod species from the Cambrian (Series 2, Stage 3) Chengjiang Lagerstätte, Southwest China. Sclerotised dorsal terg-ites, sclerotisation of post-frontal head limb appendages, and no isolated cephalic sclerite support the euarthropod affinities of B. yangi gen. et sp. nov. However, the frontal head limbs resemble in morphology the anteroventral raptorial appendage of radi-odonts. Although, due to the absence of critical soft anatomy, we cannot elucidate the exact segmental affinities of these raptorial appendages, the possession of ‘great appendage’-like frontal head limbs is important for assessing the range of limb morphology evolved by early euarthropods.
... Yet, some authors have pointed out that in some species, such as I. auritus and I. volucris, the morphologies of the dorsal shield and appendages suggest more limited swimming capabilities, and possibly nekto-benthic lifestyles (Stein et al. 2010;Fu et al. 2011). Such doubts about the life mode of I. longissimus are easily dispelled by consideration of its functional morphology. ...
The Drumian Wheeler Konservat-Lagerstätte of the House Range of Utah (Wheeler-HR) has yielded one of the most diverse exceptionally-preserved Cambrian biotas of North America. The discovery of soft-bodied fossils invariably provides precious insights on this biota, for most of its non-biomineralizing components are known from very few specimens. This contribution describes some 30 new exceptionally-preserved fossils of Wheeler panarthropods. Two new species are recognized, the radiodont Hurdia sp. nov. A and the megacheiran Kanoshoia rectifrons gen. et sp. nov. Along with a species of Leanchoilia, K. rectifrons represent the first confident megacheiran record in these strata. The presence of the radiodont genus Amplectobelua and the isoxyid species Isoxys longissimus are reported outside of the Burgess Shale in Laurentia. New specimens of Caryosyntrips serratus, Naraoia compacta, Messorocaris magna, and Mollisonia symmetrica provide insights on the phylogenetic affinities, local spatial distribution, and morphological variation of these species hitherto known by single specimens in the Wheeler-HR. The same is true of new materials of the more common Pahvantia hastata and Perspicaris? dilatus. Formal descriptions of the order Mollisoniida ord. nov. and family Mollisoniidae fam. nov. are also provided. Lastly, the preservation of body structures other than the dorsal exoskeletons is illustrated for the first time in two common components of the fauna: the agnostid Itagnostus interstrictus and the bivalved euarthropod Pseudoarctolepis sharpi. The new material substantially improves our understanding of the diversity of the Wheeler-HR biota, and provides new evidence of its distinctiveness relative to the Wheeler biota of the Drum Mountains.
