Palaeoscolecid Worms Research Articles

Polar gigantism and remarkable taxonomic longevity in new palaeoscolecid worms from the Late Ordovician Tafilalt Lagerstätte of Morocco

ABSTRACT The Late Ordovician Tafilalt Biota of the Moroccan Anti-Atlas includes a diverse range of soft-bodied organisms, including palaeoscolecids, paropsonemid eldonioids, graptolites and cheloniellid arthropods, as well as a rich assemblage of mineralised taxa, among them conulariids, trilobites and echinoderms, often found as articulated skeletons. The new fossil locality, not far from the original Bou Nemrou site, has produced two new palaeoscolecid taxa, the new genus and species Anguiscolex africanus and the new species Wronascolex superstes. They are preserved as compression fossils in fine-grained mudstones, where the original phosphatic sclerites have been diagenetically substituted by pyrite and later weathered to iron oxides, giving them a characteristic rusty colour. This area of Gondwana was located adjacent to the Late Ordovician South Pole and both Anguiscolex africanus gen. et sp. nov. and Wronascolex superstes sp. nov. present a degree of polar gigantism, which has been suggested for other taxa in such high palaeolatitudes such as bryozoans, conulariids, trilobites and radiodonts. Lastly, the occurrence of Wronascolex extends the distribution of this typically Cambrian taxon into the Late Ordovician, indicating a total range for the genus exceeding 60 million years, more than any other palaeoscolecid genus described to date. urn:lsid:zoobank.org:pub:6FD5F086-FBC6-465C-B5B7-D29EF9A6B8FB

Re-description of the Spence Shale palaeoscolecids in light of new morphological features with comments on palaeoscolecid taxonomy and taphonomy

The middle Cambrian (Miaolingian Series; Wuliuan Stage) Spence Shale of Utah and Idaho preserves a diverse assemblage of biomineralized and soft-bodied taxa. Among the rarest specimens of this fauna are palaeoscolecid worms. Until recently, only one specimen was known from the Spence Shale, the holotype specimen of Palaeoscolex ratcliffei Robison, 1969, later included in the genus Wronascolex. This specimen is preserved as part and counterpart but missing both the posterior and anterior terminations. A new specimen, discovered by Riley Smith, preserves an everted proboscis with spines. Based on new data collected using scanning electron microscopy and energy dispersive X-ray spectrometry (SEM–EDS), and optical microscopy, the species is thought to represent a new genus, Utahscolex gen. nov., rather than a species of Palaeoscolex or Wronascolex as previously suggested. The new genus differs from the other two genera in the lack of node ornamentation of the plates, as well as the absence of microplates and platelets. Based on this case study, it is recommended that future revisions of palaeoscolecid taxonomy require knowledge of plate, platelet, and microplate ornamentation, as well as the arrangement of the plates, platelets, and microplates on the cuticle. In addition to the improved morphological information provided by the new specimen, it also advances our knowledge of the taphonomic pathways in the Spence Shale and in palaeoscolecid worms in general. The preservation of the plates of the two specimens of this species differ in elemental composition and somewhat in quality. While both the holotype and new specimen show localized magnesium and phosphorus within the plates, the holotype has a substantial iron component, whereas the new specimen instead shows elevated calcium. In addition, kerogenization, pyritization, aluminosilicification, and phosphatization can be observed throughout the specimen. The preservation varies not only between the specimens, but also within, demonstrating the high variability of preservational pathways within a Burgess Shale-type deposit, and providing insights into the circumstances that lead to soft-bodied preservation in the Spence Shale.

A cryptic record of Burgess Shale‐type diversity from the early Cambrian of Baltica

AbstractExceptionally preserved ‘Burgess Shale‐type’ fossil assemblages from the Cambrian of Laurentia, South China and Australia record a diverse array of non‐biomineralizing organisms. During this time, the palaeocontinent Baltica was geographically isolated from these regions, and is conspicuously lacking in terms of comparable accessible early Cambrian Lagerstätten. Here we report a diverse assemblage of small carbonaceous fossils (SCFs) from the early Cambrian (Stage 4) File Haidar Formation of southeast Sweden and surrounding areas of the Baltoscandian Basin, including exceptionally preserved remains of Burgess Shale‐type metazoans and other organisms. RecoveredSCFs include taxonomically resolvable ecdysozoan elements (priapulid and palaeoscolecid worms), lophotrochozoan elements (annelid chaetae and wiwaxiid sclerites), as well as ‘protoconodonts’, denticulate feeding structures, and a background of filamentous and spheroidal microbes. The annelids, wiwaxiids and priapulids are the first recorded from the Cambrian of Baltica. The File HaidarSCFassemblage is broadly comparable to those recovered from Cambrian basins in Laurentia and South China, though differences at lower taxonomic levels point to possible environmental or palaeogeographical controls on taxon ranges. These data reveal a fundamentally expanded picture of early Cambrian diversity on Baltica, and provide key insights into high‐latitude Cambrian faunas and patterns ofSCFpreservation. We establish three new taxa based on large populations of distinctiveSCFs:Baltiscalida njordagen. et sp. nov. (a priapulid),Baltichaeta jormungandagen. et sp. nov. (an annelid) andBaltinema ranagen. et sp. nov. (a filamentous problematicum).

New Localities and Palaeoscolecid Worms from the Cambrian (Stage 4, Series 2) Guanshan Biota in Kunming, Yunnan, South China

AbstractThe Guanshan Biota from the Cambrian Stage 4 Wulongqing Formation is a typical Burgess‐shale type Lagerstätte that had witnessed the Cambrian explosion. Here we report two new localities of the Guanshan Biota, which is located at Baimei village, south of Kunming and Xinglong village, Wuding County, Yunnan Province respectively. Both localities produce soft‐body fossils and several new taxa, e.g. a new species of palaeoscolecidans (Palaeoscolex xinglongensis sp. nov.) reported herein. The comparative study of the new species with similar form not only indicates that there is a diversification of palaeoscolecid species in Guanshan Biota, but also strengthens the ties between the older Chengjiang Biota and the younger Kaili Biota (and also the coeval Burgess Shale community). Three paleoecological features, including high diversity, little disparity and richness of palaeoscolecid worms, are summarized as a case study to represent the differences between Guanshan and Chengjiang Biota.

Distinctive Scleritome with Marginal Tubercles of a New Palaeoscolecid Worm from the Shipai Fauna (Cambrian Epoch 2) at Three Gorges, South China

AbstractSEM analysis of trunk ornamentation on a compressed palaeoscolecid fossil from the Shipai fauna, Cambrian Series 2 and Stage 4 at Three Gorges, South China, allows a reassignment of the material to a new taxon, Sanxiascolex papillogyrus gen. et sp. nov. The preserved body is entirely annulated. Each annulus is ornamented by four rows of irregularly alternating plates and each plate bears numerous tubercles at the marginal region and a variable number (zero to six) of nodes at its central part. These features are unique among known palaeoscolecids. Comparative analyses with other compressed palaeoscolecid macrofossils and phosphatized material on the pattern of trunk ornamentation indicates that a detailed examination of the cuticle ornament weighs heavily in analyses of their taxonomic distinctions. A similar sclerite pattern to that of S. papillogyrus has been found in some phosphatized palaeoscolecid cuticle fragments as well as in isolated sclerites. The upper series of nodes and tubercles of these sclerites suggest an accretional mode of sclerite growth. The considerable variation in node number observed across the plates of S. papillogyrus demonstrates that phosphatic palaeoscolecid taxonomy based on relatively minor variations in the number of sclerite nodes should perhaps be reconsidered. As the origins of the phosphatized specimens are quite diverse, a large variety of isolated sclerites from the Early Palaeozoic may not reflect actual biodiversity.

Palaeoscolecid worms from the Lower Ordovician Fezouata Lagerstätte, Morocco: Palaeoecological and palaeogeographical implications

The Lower Ordovician Fezouata Lagerstätte from Morocco (central Anti-Atlas, Zagora area) has yielded abundant and diverse soft-bodied fossils. Most described taxa were epibenthic or pelagic, so that little is known about the endobenthic components of the fauna. Here we report the discovery of a locally abundant element of the biota, a palaeoscolecid worm, which may have played an important ecological role in the community. Palaeoscolecids had a long, annulated body with an eversible tooth-bearing pharynx. They probably represent stem priapulids, but unlike them, they were protected by biomineralized (phosphatic) microscopic plates covering most of the body. These sclerites are commonly found isolated within SSF assemblages, thus considerably extending the fossil record of the group that ranges from the Cambrian Series 2 (Stage 3) to the upper Silurian. Like priapulids, palaeoscolecids might have been important bioturbators, contributing to the substrate colonization in the lower Palaeozoic. The discovery of abundant material (38 specimens) in the Fezouata Shale (Lower Ordovician, Morocco) allows us to reconsider their possible lifestyle, habitat and feeding habits. All the specimens belong to Palaeoscolex? tenensis, a species previously only known from a fragment of cuticle from the Floian of Bohemia (Czech Republic). Some exhibit remains of the gut and aboral spines, features that are highly informative with regard to the ecology of these extinct organisms, but rarely preserved. The phosphatic nature of the plates is demonstrated by compositional analyses and interpreted with regard to the diagenetic context of the Fezouata Shale as primary. We also hypothesize that (at least) some palaeoscolecids were makers of Tomaculum-type ichnofossils, which are elongate clusters of faecal pellets, and show that they ingested a notable amount of sediment during the normal course of feeding. The presence of Palaeoscolex? tenensis in the Lower Ordovician of Morocco further documents the great faunal similarities between Perunica and northern Gondwana at that time.

Micrometric detail in palaeoscolecid worms from Late Ordovician sandstones of the Tafilalt Konservat-Lagerstätte, Morocco

The late Ordovician Tafilalt Biota of Morocco is a recently discovered Konservat-Lagerstätte that provides abundant paropsonemid eldonioids – resembling those from the Cambrian Burgess Shale and Chengjiang biotas, or other paropsonemid occurrences from the Ordovician to Silurian of the US and Australia – large discoidal ?holdfasts, non-biomineralised cheloniellid arthropods, rare vermiform fossils and articulated skeletons of echinoderms and trilobites. Exceptional preservation of soft-bodied organisms occurs in medium- to coarse-grained sandstones, in a style reminiscent of the soft-bodied Ediacaran fossils of the White Sea Assemblage. Here, we describe the first articulated scleritomes of a large palaeoscolecid worm from Africa. In addition to the mineralised sclerites, the specimens also exhibit extensive soft-tissue preservation down to micron-scale, including fine detail of annuli with their plate, platelet and microplate arrangement on a reticulate cuticle. Compression fossils of the new species Gamascolex vanroyi are represented by external moulds with remains of phosphatised cuticular structure, secondarily weathered into strontian crandallite. Partial foregut fossilisation is seen in one specimen, and phosphatised digestive structures are also reported in three co-occurring trilobite genera at the Bou Nemrou locality. From a palaeogeographic point of view, these North African palaeoscolecids represent the highest palaeolatitudinal occurrence of this Palaeozoic group in Gondwana, being described for the first time in cold-water areas adjacent to the Late Ordovician South Pole. It also provides a palaeobiogeographic link to the original distribution of the genus Gamascolex in a central European Peri-Gondwanan terrane.

New palaeoscolecid worms from the Furongian (upper Cambrian) of Hunan, South China: isMarkueliaan embryonic palaeoscolecid?

Abstract: Three‐dimensional fragments of palaeoscolecid cuticle have been recovered from the Furongian (upper Cambrian) of Hunan, South China. Extraordinary preservation of the fossils shows exquisite surface details indicating a three‐layered structure of the cuticle. One new genus and two new speciesDispinoscolex decorusgen. et sp. nov. andSchistoscolex hunanensissp. nov. are described. The co‐occurrence of these palaeoscolecid remains with those ofMarkuelia hunanensisallowed us to test the hypothesis thatMarkuelia, known hitherto only from embryonic remains, is an embryonic palaeoscolecid. The comparative anatomy ofMarkueliaand the co‐occurring palaeoscolecids shows a number of distinctions, particularly in the structure of the tail; all similarities are scalidophoran or introvertan (cycloneuralian) symplesiomorphies. The available evidence does not support the interpretation ofMarkueliaas an embryonic palaeoscolecid.

Cambrian stratigraphy and biostratigraphy of the Flinders Ranges and the north coast of Kangaroo Island, South Australia

The lower Cambrian sediments of the Flinders Ranges, South Australia can be divided into three sequence sets. They rest unconformably on the Ediacaran succession. Sequence set ϵ1 comprises lower clastic units overlain by a carbonate dominated marine succession that shows marked lateral and vertical facies changes. Sequence sets ϵ2 and ϵ3 together comprise a largely clastic dominated succession of marginal marine to non-marine sediments with subordinate shallow marine carbonates. Sequence set ϵ1 is richly fossiliferous at some levels with biostratigraphy established for trilobites, archaeocyaths, brachiopods, small shelly fossils, acritarchs and molluscs. The Emu Bay Shale Lagerstatte (Cambrian Series 2) from the north coast of Kangaroo Island occurs within a clastic-rich shelf succession dominated by conglomerate and sandstone. The fossil content is dominated by trilobites in terms of relative abundance and currently over 50 taxa are known including, Anomalocaris, the bivalved arthropods Isoxys and Tuzoia, the nektaspids Emucaris and Kangacaris, the megacheiran Oestokerkus amongst a variety of other arthropods. Other common taxa include palaeoscolecid worms, Myoscolex, sponges, hyoliths, brachiopods, a vetulicolian and several other enigmatic forms. The oldest known well preserved complex arthropod eyes occur in this biota.

The demosponge Leptomitus cf. L. lineatus,first occurrence from the Middle Cambrian of Spain(Murero Formation, Western Iberian Chain)

The Middle Cambrian Murero Formation in the Iberian Chain (NE Spain) has yielded a small collection of softbodied fossils (palaeoscolecid worms, onychophorans, algae), a host of fossils from organisms with mineralized skeletons such as trilobites and brachiopods, and some trace fossils. This paper deals with the description of the only specimen of the demosponge Leptomitus known so far from Spain and its association with the brachiopod Micromitra, showing a probable case of commensalism by the latter over the former. The taphonomical study indicates that there was little or no disarticulation of the sponge spicules and suggests that a rather complex series of alteration processes has occurred since these organisms were buried.

Sclerite fusion in the problematic early Cambrian spine-like fossil Stoibostrombus from South Australia

New collections of the problematic spine like fossil Stoibostrombus crenulatus Conway Morris & Bengtson from the Mt. Scott Range and Wilkawillina Gorge in the central Flinders Ranges, South Australia contain fused sclerite composites. In each fused specimen the spines are merged along their lateral margins and the orientation of the spines is almost identical. These new specimens confirm that Stoibostrombus spines were dermal sclerites, arranged in lateral pairs or transverse rows. The nature of the animal secreting the spines remains elusive, but available evidence suggest that it was an ecdysozoan animal, possibly a palaeoscolecid worm.

Microborings in Early Cambrian phosphatic and phosphatized fossils

A small proportion of phosphatic and phosphatized fossils, mostly microfossils, extracted from Lower Cambrian (Qiongzhusian) lime mudstones of deeper water aspect, belonging to the Yu'anshan and Shuijingtuo formations of South China, is perforated by microborings. These microborings are present in bradoriid and phosphatocopine arthropod carapaces, lingulid brachiopod valves, Microdictyon plates and tommotiid sclerites. Their absence in co-occurring phosphatized eodiscid trilobite exoskeletons and palaeoscolecid worm trunk fragments indicates a substrate specificity that suggests the boring microorganism was heterotrophic, extracting particular residual organic compounds present in only certain bioclast types. Microborings occur as meandering tunnels and grooves on bioclast surfaces, and most are 10–20 µm wide and circular in cross-section. The euendoliths were thus able to live partly exposed as well as within the substrate. Tunnel and groove walls bear a distinct longitudinal sculpture of straight striae separated by cuspate ridges 1–2 µm apart that parallel the microboring, never twisting. The microborings accord with the ichnotaxon Microptychoites fuquanensis Dong in Dong et al. (Dong, Y., Ji, Q., Wang, S., 1984. The discovery of microscopic trace fossils in the Sinian Doushantuo Formation in southwestern China. Scientia Geologica Sinica 346–347 [in Chinese]). The fluted sculpture appears to have no modern analogue, but may have arisen by localized secretions at the tip of a bundle of filaments. This kind of microboring had been previously reported from phosphatic substrates of Ediacaran, earliest Cambrian, Middle Cambrian and probably Early Devonian age, but appears to have no Recent counterpart.

Probable microvertebrates, vertebrate-like fossils, and weird things from the Wisconsin Ordovician

Phosphatic microfossils including probable microvertebrates occur in the Early and Middle Ordovician rocks of Wisconsin. The eight types described here include the probable ostracoderm Anatolepis, and six unidentified but possible vertebrate fragments as well as the palaeoscolecid worm Milaculum. These fossils are rare, but at two localities several specimens per kg were recovered over significant stratigraphic intervals. The high concentration of certain fossils in the lower part of the Galena Group suggests that there is stratigraphic value in their description. Identification of similar material or of articulated assemblages of these fossils may eventually lead to identification of biologic affinities.

Palaeoscolecid worms may be nematomorphs rather than annelids

Lower Palaeozoic palaeoscolecid worms have usually been referred to the phylum Annelida, albeit often with a question-mark, The find of palaeoscolecids with armed proboscis in the Lower Cambrian Chengjiang fauna from Yunnan, southwest China, provides evidence that these worms were aschelminths. They are similar to the Nematoda, Priapulida, and Nematomorpha and presumably closest to the latter, although not parasitic. The palaeoscolecids appear to be just one of several ‘armoured-worm’ radiations among the earliest representatives of modem phyla, as suggested by the plentitude of ‘small shelly fossils’ in the Lower Cambrian. ***Aschelminthes, Cambrian, Chengjiang fauna, Nematomorpha, Palaeoscolecida.