[Palaeontology, Vol. 55, Part 3, 2012, pp. 501–528]

DIVERSE MIDDLE ORDOVICIAN PALAEOSCOLECIDAN WORMS FROM THE BUILTH-LLANDRINDOD INLIER OF CENTRAL WALES by JOSEPH P. BOTTING1, LUCY A. MUIR1, PETER VAN ROY2, DENIS BATES3 and CHRISTOPHER UPTON4 1Nanjing Institute of Geology and Palaeontology, Chinese Academy of Science, No. 39 East Beijing Road, Nanjing 210008, China; e-mails: [email protected], [email protected], [email protected] 2Research Unit Palaeontology, Department of Geology and Soil Science, Ghent University, Krijgslaan 281 ⁄ S8, B-9000 Ghent, Belgium; e-mail: [email protected] 3Institute of Geography and Earth Sciences, University of Wales, Aberystwyth SY23 3DB, UK; e-mail: [email protected] 41 Hamilton Terrace, Shoscombe, Bath BA2 8ND, UK; e-mail: [email protected]

Typescript received 30 March 2011; accepted in revised form 12 September 2011

Abstract: Palaeoscolecidan worms are rare, Early Palaeozoic environments. The new taxa are the following: Radnorscolex fossils with uncertain affinities within the Ecdysozoa. They are bwlchi gen. et sp. nov., Aggerscolex murchisoni gen. et sp. nov., locally abundant in the Cambrian and scattered in the Early Bullascolex inserere gen. et sp. nov., Wernia eximia gen. et sp. Ordovician, but very sparse thereafter. Forty-four specimens nov., Ulexiscolex ormrodi gen. et sp. nov., Pluoscolex linearis have been collected from the Middle Ordovician of the Builth- gen. et sp. nov. and Loriciscolex cuspidus gen. et sp. nov. The Llandrindod Inlier of Mid Wales and include well-preserved high diversity, and the taxonomic separation from known material assigned to seven new genera, with four additional groups described primarily from Cambrian carbonates, implies species in open nomenclature. An additional specimen from that palaeoscolecidans either diversified significantly during the Arenig Pontyfenni Formation of South Wales is also the Ordovician or were taxonomically segregated between car- described in open nomenclature. The total demonstrates much bonate and siliciclastic settings. Palaeobiological findings also greater palaeoscolecid diversity than hitherto suspected for this include confirmation that some palaeoscolecid basal cuticles time. The specimens are preserved as cuticle fragments in were solid and others reticulate, plates (and platelets) could shales and siltstones, often of submillimetre size but in many form by lateral accretion, plates were in part primarily phos- cases with excellent preservation. The level of detail preserved phatic and in part organic and that in at least some groups, in some is equal to that found in Cambrian phosphatized fau- platelet secretion occurred external to plate secretion. nas. The new approach to collecting, and the recognition that this material can yield taxonomically useful information, Key words: cuticle, Nematomorpha, Powys, Priapulida, opens new avenues for palaeoscolecidan research in siliciclastic taphonomy.

P alaeoscolecidans are a group of Palaeozoic (Whittard 1953; Kraft and Mergl 1989), a position that worms that possessed an annulated cuticle with numerous has now been ruled out by the presence of a proboscis. small organic or organo-phosphatic plates. Despite the Some authors (Dzik and Krumbiegel 1989) have postu- rarity of articulated preservation, the plates are widely lated them to be close to the ancestors of onychophorans distributed during the early Cambrian to late Silurian, and hence the arthropods. A recent analysis (Harvey et al. but predominantly in the Cambrian. Whole-body fossils 2010) found them to share features with nematoid and of palaeoscolecidans from the Chengjiang Biota showing scalidophoran worms that were not shared with panar- an evertible proboscis (Hou and Bergstro¨m 1994), and thropods, ruling out a position close to the base of the analyses of palaeoscolecid cuticular organization and Ecdysozoa. structure (Brock and Cooper 1993; Conway Morris 1997) Palaeoscolecidans can be preserved in several different have led to a widely accepted interpretation of the group ways, each of which provides different information. Relat- as ecdysozoans allied to the nematomorphs and ⁄ or pria- ing the taxonomy of taxa preserved in different tapho- pulids. Earlier interpretations, including consideration of nomic styles can be problematic and is discussed below in cuticle structure, suggested an affiliation with annelids the section on Systematic Palaeontology. The majority of

ª The Palaeontological Association doi: 10.1111/j.1475-4983.2012.01135.x 501 502 PALAEONTOLOGY, VOLUME 55 reports relate to isolated plates, following the first pub- Pratt 1996). Post-Cambrian records are very sparse, and lished record of hadimopanellids (Bengtson 1977; Gedik most are from the Early and Middle Ordovician, with a 1977); it was some time before these and related plate decline in their numbers thereafter. In Britain, Tremadoc types were recognized as belonging to palaeoscolecidans palaeoscolecids have been described from Shropshire (Hinz et al. 1990). While some isolated plates can be (Whittard 1953; Conway Morris 1997), Gloucestershire diagnostic for species at our current level of knowledge, (Whittard 1953) and Carmarthenshire (Owens et al. plate and microplate arrangement are more useful for tax- 1982). The youngest (early Ludlow) definite palaeoscoleci- onomic purposes. Some individual plate morphologies dan described was reported from Herefordshire (Bather recur repeatedly, particularly subcircular plates with a 1920; Whittard 1953). cluster or ring of small dorsal tubercles, which appears to The only Middle Ordovician records are a compression have been the most widespread early morphology. Identi- fossil apparently lacking fine detail from Peru (Gutie´rrez- fying convergence from isolated plate material only may Marco and Chacaltana 2006; Garcı´a-Bellido et al. 2008), not be possible. Multiple plate morphologies can also and an important and much more informative fauna occur within one scleritome (e.g. Topper et al. 2010). from the Floian to basal Sandbian of Bohemia (Kraft and Most of the best articulated cuticular material has been Mergl 1989). There are also records of further palaeosco- obtained from acid digestion residues of limestones. Aside lecids from the middle Ordovician of Bohemia (Kraft from fine structural preservation, much of the isolated, et al. 2003), but the material has not yet been described. phosphatic material also shows the plate and interplate Occurrences of ‘Protoscolex’ in the Cincinnatian (Sand- arrangement very clearly and is ideal for taxonomic pur- bian–Katian) of the United States were discussed by poses. Many of the named taxa come from this type of Conway Morris (1977); this material has also not yielded material, but relatively few such exceptional faunas have fine cuticular detail to date. At present, the record is too been described. Little is known about the group’s distri- sparse to draw definite conclusions about diversity bution within siliciclastic settings. changes through the Ordovician. There are relatively few published records describing articulated palaeoscolecidan scleritomes, reflecting the exceptional conditions required for their preservation. GEOLOGICAL SETTING AND Such compression fossils can, however, be extremely LOCALITIES abundant at some levels in the Chengjiang Biota (e.g. Hou and Bergstro¨m 1994; Han et al. 2007a). Several The new material described herein consists of a total of specimens of two genera are also known from the Sirius 44 specimens from the Middle Ordovician of the Builth Passet biota (Conway Morris and Peel 2010) and a fur- Inlier, and one from the Early Ordovician of South ther three named species from the Sinsk Biota of Siberia Wales, yielding seven describable species (all in new gen- (Ivantsov and Wrona 2004). Several undescribed palaeos- era) and five in open nomenclature. The Builth Inlier colecid specimens have been collected from the Tremado- (Fig. 1) is an area of late Middle and basal Late Ordovi- cian-Floian Fezouata formations of Morocco (Van Roy cian sediments and volcanic rocks in central Wales that et al. 2010). Where full soft-tissue preservation occurs in displays the evolution of a volcanic island complex compression fossils, specimens can show anterior mor- (Botting and Muir 2008). The rocks are principally silicic- phology, including the existence of a proboscis with sca- lastics, often with large volumes of reworked pyroclastic lids. However, preservation fidelity of the cuticle tends to deposits as immature sandstones and ashy sediments. The be much reduced relative to isolated material. This makes overall sequence and the distribution of palaeocommuni- it very difficult to assign species to known genera, higher- ties have been discussed in detail elsewhere (Botting and level groups, or even with absolute certainty to the palae- Muir 2005, 2008). Stratigraphy follows Schofield et al. oscolecids themselves. To date, no material shows both (2004) and references to environmental and ecological fine preservation of the cuticle and good detail of the variations in the sequence follow Botting and Muir proboscis, although some soft-tissue material from Chen- (2008). gjiang yields reasonable cuticular detail (Hu et al. 2008). All specimens were recovered from fine siliciclastic sed- iments of Llanvirn (Darriwilian; Didymograptus artus, Didymograptus murchisoni and Hustedograptus? teretiuscu- POST-CAMBRIAN lus biozones) age, except for the one specimen from the PALAEOSCOLECIDAN DIVERSITY type section of the Pontyfenni Formation (Floian of Whitland, Dyfed; Fortey and Owens 1987). The majority of published taxa are Cambrian in age, Palaeoscolecids have been recovered from seven sites in including the most diverse assemblages (Mu¨ller and Hinz- the Builth Inlier. Little Wern Quarry (D. artus Biozone, Schallreuter 1993; Hou and Bergstro¨m 1994; Zhang and Camnant Mudstones Formation; SO11225794; Fig. 2) BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 503

FIG. 1. Location of the Builth Inlier within the United Kingdom and of individual localities within the northern part of the inlier with their relative stratigraphic positions. Numbers indicate the stratigraphic position of the palaeoscolecids described in this article. 1=Loriciscolex cuspidus gen. et sp. nov., 2 = Wernia eximia gen. et sp. nov., 3 = Indeterminate palaeoscolecid A, 4 = Indeterminate palaeoscolecid B, 5 = Radnorscolex bwlchi sp. nov., 6 = Indeterminate palaeoscolecid D, 7 = Aggerscolex murchisoni gen. et sp. nov., 8=Ulexiscolex ormrodi gen. et sp. nov., 9 = Bullascolex inserere gen. et sp. nov., 10 = Pluoscolex linearis gen. et sp. nov., 11 = Indeterminate palaeoscolecid C. exposes approximately 10 m of trilobitic and graptolitic palaeoscolecid cuticle (Lapworth Museum: BI- grey micaceous siltstone and volcanic ashes. This is the RUG.BU2876) was also recovered from locality BG1 (Bot- type locality for Wernia eximia gen. et sp. nov. and Lori- ting 2000). Bailey Einon (middle–upper H.? teretiusculus ciscolex cuspidus gen. et sp. nov. and has also yielded Biozone, Llanfawr Mudstones Formation; SO0870 6186) indeterminate palaeoscolecid A and indeterminate pala- is a riverbank locality consisting of locally derived glacial eoscolecid B. Bwlch-y-Cefn (upper D. artus or lower drift with abundant mudstone and siltstone clasts and has D. murchisoni Biozone, Gilwern Volcanic Formation; yielded Pluoscolex linearis gen. et sp. nov., Bullascolex inse- SO1235 6117) was described by Elles (1939), as the pass rere gen. et sp. nov. and indeterminate palaeoscolecid C. northeast of Bwlch-y-Cefn Farm and is the type locality A single poorly preserved palaeoscolecid fragment (NMW for Radnorscolex bwlchi gen. et sp. nov. and also yielded 2010.47G.37a, b) was collected from further upstream on indeterminate palaeoscolecid D. The single specimen of the River Ithon, near Shaky Bridge (SO08646103). Aggerscolex murchisoni gen. et sp. nov. was collected at locality HB2 of Botting (2000, p. 97) in the Howey Brook Main Feeder (upper D. murchisoni Biozone, Gilwern Vol- MATERIALS AND METHODS canic Formation; SO09175909), a long section on the north side of Gilwern Hill described by Murchison (1839) Specimens were examined in SEM, uncoated. The SEMs and Elles (1939). The extensive Bach-y-Graig section used were Hitachi TM1000 fitted with Oxford Instru- (basal H.? teretiusculus Biozone, Llanfawr Mudstones For- ments Swift-ED-TM EDAX (Energy Dispersive X-ray mation) has yielded numerous poorly preserved palaeo- Spectrometer) operating at 15 keV (fixed) for backscatter scolecids and also Ulexiscolex ormrodi gen. et sp. nov. at images and a Hitachi S-4700 field emission scanning elec- one location (BG2 of Botting 2000; Botting and Muir tron microscope (FESEM). Light photographs were taken in press). A single specimen of very poor, indeterminate using a Nikon D80; Figure 9A was taken using a Sigma 504 PALAEONTOLOGY, VOLUME 55

FIG. 2. Simplified stratigraphy and photograph of Little Wern quarry. Marker beds in the column are volcanic ash levels; thin lines are <50 mm thick (minimum of 3 mm), thicker lines are 50–150 mm. The ranges of the two species of trinucleid trilobite at the locality appear to be mutually exclusive, providing a further stratigraphic constraint. Palaeoscolecid-bearing intervals are marked with an asterisk; the most productive level is at W8.

105 mm macro lens combined with 68 mm of extension (Fig. 12B), to exquisitely preserved material including fine tubes and camera-mounted Sunpak flash. detail of the interplate areas (Fig. 8D). In poorly Specimens are deposited in the Lapworth Museum, preserved specimens, the interplate area is typically University of Birmingham (BIRUG) and the National composed of coarse, irregular clay minerals that may be Museum of Wales, Cardiff (NMW). A sample from Bach- primary or recrystallized sediment (Fig. 12B). Secondary y-Graig (locality BG2) containing two additional palaeo- crystal growth is common, including pyrite cubes and scolecids has been placed in the Radnorshire Museum, framboids. In the best preserved material (e.g. the two Llandrindod Wells, Powys, specimen number LLWLM2010: specimens of Wernia eximia gen. et sp. nov.; Fig. 8), alu- 353a ⁄ b. minosilicates also dominate, but crystals are much finer, and pyrite growth is dominated by framboids rather than discrete cubes. This is similar to the patterns described by TAPHONOMY Gabbott et al. (2004) for the Chengjiang Biota. In Wernia gen. nov., pyrite is concentrated in areas of Specimens are either semi-complete worms on bedding cuticular degradation (Fig. 8C), consistent with formation surfaces, up to several centimetres long, or small (often as a result of decay by sulphate-reducing bacteria. This <1 mm) fragments of cuticle assumed to be derived from relatively coarse secondary pyritization is best compared moults. with that found in the Hunsru¨ck Slate and equivalent Preservation of the palaeoscolecidans is very varied, faunas (e.g. Briggs et al. 1996) but was probably wide- although all specimens are compressed and somewhat spread in early Palaeozoic Lagersta¨tten (e.g. Gabbott et al. demineralized partial cuticles. Several specimens have split 2004; Van Roy et al. 2010). In the best material at Little through the midline, showing only the internal surface of Wern (e.g. Fig. 8D), the degradation associated with this the cuticle on both parts and appear in SEM as near-fea- process had barely begun. A complication is that the tureless phosphatic or organic sheets with no more than cuticular mesh shows clear evidence of replacement by faint indications of plate arrangement (e.g. Figs 11F, 13E– micron-scale crystals that appear from EDAX to be alu- F). This applies only where the cuticle has been preserved minosilicates. In some areas, the replacement has obliter- such as at Little Wern, and at other sites, the fossils are ated the original morphology, but in well-preserved areas preserved primarily as internal and external moulds (e.g. there is only an overprint of crystal growth that is largely Figs 3A, 5A). constrained to the original outlines. It appears likely that Specimens exposing the exterior surface range from aluminosilicate growth was also affected by decay pro- badly degraded, showing only poorly preserved plates cesses that induced local pyrite formation. BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 505

A

B C

D E

FIG. 3. Scanning Electron Microscope (SEM) images of Radnorscolex bwlchi gen. et sp. nov. BIRUG:BU2874. A, overall view of latex cast. B–C, detail views showing plate arrangement and interplate areas, and with alternating interplate areas of small (I) and larger (II) microplates demarcated. D, detail of single plate with microplates; E, detail showing morphology of microplates. Scale bars represent 200 lm (A), 50 lm (B, C), 10 lm (D) and 1 lm (E).

Backscattered electron mode usually shows the plates to detectable by the EDAX unit available, the plates’ appear- be composed of less electron-dense material than the inter- ance in backscattered electron imaging and dark colouring plate areas (which are aluminosilicates), representing a high in visible light implies that they were largely carbonaceous proportion of carbon. Although carbon was not directly and that phosphate was dominantly in the crowns. The 506 PALAEONTOLOGY, VOLUME 55 undersides of plates are almost invariably less electron- between plate row pairs and platelet ⁄ microplate form and dense than the upper surfaces (e.g. Bullascolex inserere gen. distribution. To this we can add whether the basement et sp. nov.; Fig. 7A), which are sometimes partly mouldic. cuticle is solid or reticulate and whether platelet ⁄ micro- This implies stronger mineralization of the plate surfaces, plate arrays overlap plates. Many of these features require with organic carbon constituting more of the core, consis- detailed preservation of the platelet and microplate arrays, tent with previous work (e.g. Harvey et al. 2010). Internal and in our opinion, this is the minimum requirement structures of plates seen in secondarily phosphatized mate- (combined with clear preservation of plate sculpture) for rial should be interpreted in this light. the recognition of distinct taxa, although ideal material Calcium phosphate was detected on some plates (espe- would include both a growth series and large sections of cially in Pluoscolex gen. nov.), and more strongly within cuticle to show intra-organism variation. Our material creases in the cuticle. In general, it appears to have mostly shows differences in several features between the new spe- dissolved, but to have been much more strongly present cies and genera, such that none of these taxa could be within plates than in interplate regions. In Wernia gen. synonymized with each other, or with other named mate- nov., there is deformation of the reticulate cuticle, suggest- rial from elsewhere. If there is insufficient interplate infor- ing that microplates and cuticle were flexible and therefore mation, we have left the species in open nomenclature. organic (e.g. between the two plates in Fig. 8A). In situ Previous work has taken diverse approaches to this microplates are probably also now composed of alumino- subject. Mu¨ller and Hinz-Schallreuter (1993) erected sev- silicates, but show little evidence of coarse recrystallization. eral taxa on five or fewer well-preserved specimens, In summary, the compression fossils described here, whereas Ivantsov and Wrona (2004), working with rare although superficially similar, include a wide range of compression fossils on bedding planes, erected two spe- taphonomic variations. In some cases, the cuticle is pre- cies on very few specimens (in one case only one); served as simple external moulds, but in others there is a although these specimens were largely complete individu- degree of original mineralogy, combined with recrystalli- als, they preserved only the plate arrays with no detail of zation and overgrowth by pyrite, clay minerals and proba- interplate areas. Fragments of such material would be bly other minerals. The taphonomy of these fossils is unrecognizable, but being able to illustrate plate variation therefore a highly complex area that should be studied in along the length of the specimen adds some credibility to detail for each site, including other taxa, to fully under- the taxons’ validity. Although it is critical to avoid erect- stand the preservation. ing unrecognizable taxa, this must be balanced with the scientific accessibility of rare material and should be assessed on a case-by-case basis. SYSTEMATIC PALAEONTOLOGY In the current material, the specimens identified as dif- ferent taxa cannot be ontogenetic stages of the same spe- The ontogeny of palaeoscolecidans is suspected to be cies. In particular, named co-occurring taxa (Fig. 1) are complex (Brock and Cooper 1993; Topper et al. 2010), clearly distinct. Loriciscolex cuspidus gen. et sp. nov. and and values and measurements given herein refer only to Wernia eximia gen. et sp. nov. occur together with two the specimens and growth stages described. Plate orna- taxa in open nomenclature at Little Wern. Both are ment varies within an individual (e.g. Topper et al. 2010), known from multiple specimens showing near-identical but cannot normally be assessed in the material described features, and they differ radically in plate form and here. Dorsal and ventral plate morphologies can also dif- arrangement, interplate scleritome and cuticle structure. fer significantly (e.g. Ivantsov and Wrona 2004), and such Bullascolex inserere gen. et sp. nov. and Pluoscolex linearis potential deviations from the descriptions should be con- gen. et sp. nov. differ even more radically. The other sidered when comparing with other material. Despite all named taxa each occur as isolated named species at dif- named specimens being placed in new species and genera, ferent horizons and localities, but all are relatively large we have been conservative in erecting new taxa, although fragments of cuticle with flattened diameters of 0.8 mm others (e.g. Topper et al. 2010) might have left all our (Radnorscolex bwlchi gen. et sp. nov.), 0.6–0.7 mm (Agger- material in open nomenclature, because of incomplete scolex murchisoni gen. et sp. nov.) and 0.2 mm (Ulexisco- knowledge of growth series and intraspecific variation. lex ormrodi gen. et sp. nov.). The first two represent While we appreciate this argument, we consider that similar growth stages, but differ substantially in plate approach over-cautious, and have named new taxa where form and spacing, preserved over a substantial length we are confident that they were clearly distinct and that of the trunk and therefore reflect a genuine taxonomic we would recognize further well-preserved specimens. difference. Ulexiscolex ormrodi gen. et sp. nov. is funda- Palaeoscolecidan taxonomy is based on various features mentally different in the interplate scleritome. including the plate form and sculpture, plate arrange- Terminology follows standard usage, in which an annu- ment, presence or absence of a distinct intercalation lus (where present) consists of a distinct pair of plate BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 507 rows, usually recognizable through changes in the inter- Remarks. Radnorscolex is similar to Palaeoscolex piscato- plate scleritome. In some cases, the plates are asymmetric rum in plate morphology and cuticular organization, but (e.g. Wernia gen. nov.), with plates in each row in an differs fundamentally in the nature of the interplate scle- annulus facing in opposite directions. Other taxa (Loricis- rites and the lack of intercalations. The presence of two colex gen. nov.) have plate rows, but the rows are not size orders of microplates, rather than ornamented plate- paired into annuli and all plates face the same direction. lets, is characteristic of a number of existing genera (e.g. Platelets are smaller sclerites that resemble plates in form Rhomboscolex Mu¨ller and Hinz-Schallreuter, 1993), but in and sculpture, whereas microplates are very small, unor- each case there is a clear feature that also separates that namented sclerites. The distinction between platelets and genus from all others (e.g. in Rhomboscolex, the plates microplates may be entirely artificial, but we have opted have a characteristic petaloid tubercle arrangement). In to retain them as useful descriptive terms; in some cases, most articulated taxa where interplate detail is lacking the two forms have distinct distributions. and the generic assignment cannot therefore be assessed with certainty (e.g. Palaeoscolex spinosus Ivantsov and Wrona, 2004), the plate morphology differs substantially Phylum UNCERTAIN from our material, with the tubercles in Radnorscolex Class PALAEOSCOLECIDA Conway Morris and Robison, 1986 much less regularly arranged. An exception is Guandusco- Family PALAEOSCOLECIDAE Whittard, 1953 lex minor Hu et al., 2008, in which plate morphology is very similar, but interplate cuticular detail was lacking. Diagnosis. Palaeoscolecids that have an annulated appear- Their diagnosis, however, does state that it possessed ance because of the arrangement of plates into annuli three rows of plates per annulus, whereas here it is two consisting of pairs of plate rows and with the plates being rows, as shown by the repetition of microplate sizes rounded and tuberculate. (Fig. 3C). Compare also with Aggerscolex murchisoni gen. et sp. nov. Remarks. We restrict the family Palaeoscolecidae to the forms included above to define more precisely the differ- ences between known palaeoscolecid lineages. In the past, Radnorscolex bwlchi sp. nov. the family has been defined very broadly, which has Figures 3, 4D resulted in many distinctly different cuticle types being included. The diagnosis provided here is based around Derivation of name. After Bwlch-y-Cefn, the type locality. The the best known and originally defined taxa, such as Palae- Welsh word refers to a mountain pass, and the specimen was collected from a narrow, fault-influenced stream valley that oscolex piscatorum Whittard, 1953, but encompasses a forms the pass between two hill ranges. Pronunciation: bull-chi large number of more complex morphologies. This with ‘bull’ pronounced as for male cow and ‘ch’ pronounced as includes taxa such as Gamascolex Kraft and Mergl, 1989 in Scottish ‘loch’ or German ‘Ich’. and all taxa erected by Mu¨ller and Hinz-Schallreuter (1993), but excludes forms with a highly modified sclerite Diagnosis. As for genus. arrangement or plate morphology (for comparison, see Wernia gen. nov. and Pluoscolex gen. nov.). For further Holotype. Lapworth Museum (University of Birmingham) speci- discussion of the scope and relationships of the Palaeo- men BIRUG:BU2874; partial trunk in coarse ashy siltstone. Did- scolecidae, see Ivantsov and Wrona (2004). ymograptus murchisoni Biozone (or possibly top of D. artus Biozone), Bwlch-y-Cefn, near Llandegley, Powys. Only known specimen. Genus RADNORSCOLEX gen. nov. Description. Section of length 4 mm, showing rounded posterior Derivation of name. After Radnorshire, the old county of Wales termination (Fig. 3A). Width constant except for rapid terminal that includes the Builth Inlier. Gender masculine. tapering, 0.8 mm in compressed state. Annuli with two plate rows, which are offset by around half the plate spacing. Nor- Type species. Radnorscolex bwlchi sp. nov. mally, 28–32 plates in half-circumference, with plates always sep- arated by microplates. Separation of plates within a row rarely exceeds 20 lm and is often <10 lm (but perhaps reduced dur- Diagnosis. Palaeoscolecids with simple, circular tuberculate ing flattening); longitudinal separation of rows is 10–20 lm plates arranged in annuli but without intercalations. Micro- within an annulus and 20–30 lm between annuli. Plates are typ- plates within an annulus unornamented and separated ically 35–45 lm in diameter, subcircular, shallowly convex and from interannular microplates only on the basis of size; one with prominent, rounded to conical tubercles (Fig. 3B–D). roughly twice the size of the other. Plates with up to 12 Tubercles are arranged in a ring of up to twelve (usually around tubercles, often arranged in a ring with a central node. eight), commonly showing a subrhomboidal pattern rather than 508 PALAEONTOLOGY, VOLUME 55 circular and often with a larger central tubercle (Fig. 3C). In Type species. Aggerscolex murchisoni sp. nov. some plates, there are up to four tubercles in the centre. The remaining plate surface often shows small projections, some- Diagnosis. Plates with tubercles in condensed arrange- times approaching tubercles in size; such projections are typically ment forming one or two irregular central mounds. Inter- concentrated around the plate margins (e.g. Fig. 3D). In a few plate regions covered by hexagonally arranged microplates, examples, as few as four tubercles are seen, usually closer to the each rounded hexagonal in outline. plate centre than to the edge (Fig. 3D). Microplates cover the entire remaining cuticle, consisting of two types defined by a size difference (Fig. 3C). The larger Remarks. The mounded tubercles on the plates of Agger- microplates (presumed to be between plate rows within an scolex distinguish it from all other described species. The annulus from reference to other taxa) are subcircular to form of these mounds cannot be explained by abrasion polygonal with diameter typically 2–3 lm and arranged in a of a more normal plate morphology, as the central subhexagonal array. None show any clear ornamentation, mound shows high relief but the remainder of the plate although many are domed or subconical (Fig. 3E). The smaller surface is much lower; abrasion would have eroded the microplates are distributed between alternate annuli. They are projecting central mound while leaving smaller tubercles morphologically similar to intra-annular microplates, unorna- at its base protected. It could also not have produced l mented and 0.8–1.5 m in diameter, but less regularly regular forms such as the square central mounds. arranged. The larger microplates dominate between the plates Recrystallization similarly cannot explain the position of in any row, making regions of smaller microplates narrower, the irregular mounds always in the centre of the plates, although there is no sharp dividing line between them. Both sizes of microplates are closely packed and no evidence of the nor the repetition of certain consistent morphologies. supporting cuticle is seen. The holotype is a large piece of articulated scleritome, rather than an extensively transported fragment, and the Remarks. The specimen is superficially similar to the more decay-prone microplates are well preserved in large much larger Palaeoscolex piscatorum Whittard, from the parts of the specimen, further implying that the visible Tremadoc of Shropshire, but the latter differs significantly plate morphology is primary rather than artefactual. in the generic characteristic of possessing platelets resem- Aside from the plate morphology, there is a strong simi- bling miniature plates, compared with much smaller larity of the species to Radnorscolex bwlchi gen. et sp. platelets. The plates themselves have tubercles arranged in nov. in the arrangement and nature of sclerites in the an ellipse, and in most cases do not possess a central interplate area, and the two genera are probably closely tubercle. There are other potentially significant differ- related. ences, relating to the wider separation of plates and plate rows in P. piscatorum, but these could potentially be ontogenetic differences. The most fundamental difference, Aggerscolex murchisoni sp. nov. however, is the absence of a structural intercalation in Figures 4E, 5 R. bwlchi gen. et sp. nov., which would be just as clearly visible in this material as it is in the similar preservation Derivation of name. For Sir Roderick Impey Murchison, who of P. piscatorum. The intercalations cannot be hidden described the type locality, now known as Murchison’s Section, on Gelli Hill. by cuticle folding or contraction, as the microplate arrays are clearly preserved over considerable distances (e.g. Diagnosis. As for genus. Fig. 3D). The majority of species placed in Palaeoscolex have Holotype. Lapworth Museum (University of Birmingham) speci- been assigned to this genus on the basis of being an ann- men BIRUG:BU2875, part and counterpart of partial specimen ulated, papillated worm looking superficially similar to from locality HB2 (Abereiddian; D. murchisoni Biozone) of the P. piscatorum. It would not be possible to separate Howey Brook Main Feeder (‘Murchison’s Section’), Gelli Hill, R. bwlchi from a small specimen of Palaeoscolex sp. by near Llandrindod, Powys. Only known specimen. relying only on material that lacks interplate detail, and specimens of that type cannot be compared Description. Uncoiled, U-shaped specimen (part shown in reliably with other taxa for which cuticular detail is Fig. 5A), width 0.6–0.7 mm, length exceeding 9.5 mm, with ter- preserved. minations absent. Width approximately constant over visible length, with slight expansions at irregular intervals of around 0.5–1.0 mm. Approximately 20 plate annuli per millimetre and Genus AGGERSCOLEX gen. nov. 18–20 plates per annulus (extrapolated from compressed half- annulus). Plate annuli represented by pairs of transverse plate Derivation of name. Latin agger, mound; refers to the dense clus- bands (Fig. 5C; also visible in left part of Fig. 5A), but without a ter of tubercles in the centre of the plates. Gender masculine. clear intercalation or other boundary between them. BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 509

FIG. 4. Palaeoscolecid scleritome AB reconstructions. A, Ulexiscolex ormrodi gen. et sp. nov. B, Bullascolex inserere gen. et sp. nov. C, Wernia eximia gen. et sp. nov. D, Radnorscolex bwlchi gen. et sp. nov. E, Aggerscolex murchisoni gen. et sp. nov. Scale bars represent 20 lm (A, E) and 40 lm (B–D).

C D

E

Plates rounded, subcircular and of diameter typically 20– nal keels running from the central mound to the plate margin. 25 lm, but sometimes as little as 15 lm. Plates rows separated Some also show concentric marginal ridges either in the plates by 25–35 lm within an annulus and by 60–70 lm between themselves or in the surrounding microplated cuticle (e.g. annuli. Within an annulus, the two plate rows are offset by half Fig. 5B); this may be a taphonomic effect indicating that plates the distance between plates, and transverse separation is around were elevated above the cuticle prior to compression. 20–30 lm (Fig. 5C). Interplate areas (Fig. 5B) are densely and completely covered by Ornament of plates highly variable (Fig. 5C). Some appear nontuberculate microplates. The microplates are larger between effectively smooth, shallowly convex. Typical plates, however, the plate rows within an annulus, at around 2.5–3 lm, and less show tubercles condensed into a lumpy mound in the plate cen- clearly preserved but around 1.5 lm in diameter between annuli. tre, or frequently two such mounds (Fig. 5C, inset 1); a few dis- Wherever microplate arrangement is preserved clearly, the arrange- play a short ridge instead or are triangular (Fig. 5C, inset 2). In ment is strictly hexagonal, with one axis parallel to the worm axis some cases, both the mound and the plate margin are roughly (Fig. 5B–C, with worm axis subvertical). Microplates themselves four-sided (Fig. 5C, inset 3 and marked 4), although usually are somewhat hexagonal in outline, but strongly rounded. rounded. In such cases, the sides of the square are arranged par- allel and perpendicular to the worm orientation, and in the most Remarks. The plate sculpture is currently unique to this extreme cases (Fig. 5C, marked 4), the plate is marked by diago- species. The only superficially similar isolated plate mor- 510 PALAEONTOLOGY, VOLUME 55

A B

C

FIG. 5. Scanning Electron Microscope (SEM) images of Aggerscolex murchisoni gen. et sp. nov., BIRUG:BU2875. A, overall view of part of specimen; B, detail of latex cast of interplate scleritome; C, detail of latex cast of scleritome showing variation in plate morphology including magnifications of double, triangular and rectangular mounds. Scale bars represent 200 lm (A) and 20 lm (B, C).

phology yet described is the Early Cambrian form species There are sufficient similarities to Radnorscolex bwlchi Hadimopanella staurata Wrona, 2004, in which there is a gen. et. sp. nov. in the microplate form and arrange- dense cluster of four flat-topped nodes forming a cruci- ment, to imply a close relationship. Aggerscolex murchi- form mound in the centre of the plate. The described soni differs dramatically from R. bwlchi in the much material shows none of the variation seen in A. murchi- wider plate separation showing that the differences are soni gen. et sp. nov., and the sharply truncated apex is not purely due to preservational aspects; although plate also distinct, and plates of the two species must be pre- separation is thought to vary ontogenetically (Topper sumed to be convergent. et al. 2010), the degree of difference here would be BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 511 extraordinary. Both holotypes also represent significant half-ring, but annuli not clearly defined (Fig. 6A). Plates subcir- lengths of the trunk at a similar growth stage, showing cular, generally 6–8 lm in diameter and slightly irregular, with that the differences are not ontogenetic forms of the typically 10–11 tubercles of various sizes, but varying more same species, and are very unlikely to represent differ- widely in extreme examples (Fig. 6C). Often three or four tuber- ent parts of the same cuticle. cles are aligned transversely across the centre, but overall tuber- cle arrangement unpredictable. Spacing of plates within an annulus very uneven, ranging from 2–7 lm in observed area (Fig. 6B–C). Genus ULEXISCOLEX gen. nov. Interplate areas are filled by a variety of smaller platelets and microplates, without a clear distinction between the classes Derivation of name. After Latin Ulex, gorse, for the adjacent (Fig. 6B–C). Most are in the range 1–4 lm in diameter and housing estate on the edge of Llandrindod, known as Gorse irregularly shaped, particularly around plate borders, where they Farm. Gender masculine. may become elongated and curved. Many of the more irregular outlines interlock with adjacent platelets, with submicron micro- Type species. Ulexiscolex ormrodi sp. nov. plates filling some gaps between discordant platelet boundaries (Fig. 6C). Tubercles are present on virtually all platelets, three or Diagnosis. No intercalations between irregular plate rows, four on the larger examples and one or two on the smallest, but with plates uneven in size and with typically 9–13 nodes some small microplates are also present. The irregularity of the in irregular distribution. Interplate areas are a continuum interplate sclerites prevents the development of intercalations; of relatively large, pronounced node-bearing platelets to there is no sign of transversely elongated microplate bands or small, smooth microplates. regular size variation across annuli.

Remarks. This is the only specimen of nearly 20 found Remarks. Ulexiscolex shows several unusual features that from BG2 to reveal good details of the cuticle. The other preclude an attribution to existing genera. However, it specimens are much longer fragments and heavily oxidized does show some similarity in plate and platelet after presumed secondary pyritization and are suspected to morphology to the Early Cambrian genera Schistoscolex represent more or less entire worms with soft-tissue pyriti- Mu¨ller and Hinz-Schallreuter (1993) and particularly zation. The preservation of this fragment is sufficiently Shergoldiscolex Mu¨ller and Hinz-Schallreuter, 1993 from good to allow recognition that intercalations were absent Australia. These differ, however, in possessing clear inter- and that the cuticle is not deformed in such a way to calations. Thoracoscolex Mu¨ller and Hinz-Schallreuter obscure them. The large (relative to small plates), orna- (1993), from the same deposits, has less clear intercala- mented microplates are very distinct from all other taxa in tions, but platelets are elongated along the divisions, and this article and as they represent a similar growth stage to the plates are much less highly ornamented (Mu¨ller and both Aggerscolex gen. nov. and Radnorscolex gen. nov. can- Hinz-Schallreuter 1993). not represent ontogenetic variation. Other taxa in this arti- cle are clearly distinct in several ways, including plate Ulexiscolex ormrodi sp. nov. morphology and arrangement. The lack of intercalations Figures 4A, 6 also separates it from other Welsh Basin taxa such as Pal- aeoscolex piscatorum (Conway Morris 1997). Derivation of name. In recognition of the work, over many years, of amateur palaeontologist Tess Ormrod; she collected several of the palaeoscolecid specimens known from the type locality. Family UNCERTAIN Diagnosis. As for genus. Remarks. The new genera described below are in all cases Holotype. NMW 2010.47G.23 (Fig. 4); fragment of presumed sufficiently different from existing taxa that they either moulted cuticle, from locality BG2 (early H.? teretiusculus Bioz- represent small parts of new worms that do not reflect one, Llandeilian) in Bach-y-Graig stream section, Llandrindod, the normal structure (e.g. Bullascolex gen. nov.), or they Powys. Only confirmed specimen. cannot be accommodated into the definitions of existing families. The differences are discussed specifically for each Other material. NMW 2010.47G.36, a large cuticle fragment of genus, but include features such as radically new plate what may be the same species from Bach-y-Graig is tentatively morphologies, reticulate basal cuticle, fused and semi- included. Although it appears well preserved in light microscopy, fused plate rows and isotropic plate arrangement. New little detail beyond rough plate arrangement is seen in SEM. families may be needed in the future to accommodate these taxa, but further material will be required to con- Description. Short length of cuticle, folded, approximately firm this. 0.2 mm in diameter and 1 mm long. Roughly 20 plates in one 512 PALAEONTOLOGY, VOLUME 55

A B

C

FIG. 6. Scanning Electron Microscope (SEM) images of Ulexiscolex ormrodi gen. et sp. nov., NMW 2010.47G.23. A, Overall view of part of cuticle, illustrating the irregular appearance without obvious annuli and only largest plates easily distinguishable; B, detail showing plates and platelets; C, wide view of part of cuticle showing plates in approximate transverse rows and plate and platelet morphology. Scale bars represent 30 lm (A), 20 lm (B) and 10 lm (C).

Genus BULLASCOLEX gen. nov. Diagnosis. Palaeoscolecids with large, multituberculate plates densely arranged without clear rows. Narrow Derivation of name. Latin bulla, button, referring to the appear- interplate areas of tuberculate platelets, with those on ance of unusually large, round plates. Gender masculine. either upper or lower surface distinctly larger than the other. Type species. Bullascolex inserere sp. nov. BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 513

Remarks. Bullascolex cannot easily be accommodated in platelets is seen only from the internal surface, and no ornament any existing family because although it shows character- is visible. istically tuberculate plates, their arrangement is very Plates are large (around 40 lm diameter), flat (except for dense and generally disorganized. The compressed pres- tubercles) and irregularly circular to elliptical. They are arranged ervation does not allow any indication of annular in short rows locally, but long-distance order rapidly degenerates (Fig. 7A), to the degree that the orientation of the fragment can- ridges on the cuticle, but if they existed then they were not be determined. Plates show lateral enlargement by the fusion not marked by plate rows. Such a nonannular arrange- of platelets (Fig. 7B, G). Within some of the plates, tubercles ment of plates is highly unusual; we have been unable even in the subcentral part are surrounded by polygonal ridges, to identify any similar material described previously. as if the plates originated entirely as fused smaller units The only caveat is that some known taxa have small (Fig. 7B). A single plate possesses around 25–30 sharp tubercles regions that lack annuli, for example at the anterior of various sizes. Some of the major tubercles are accompanied (e.g. Harvey et al. 2010). As the fragment is small, we by one or more small spines on their flanks (Fig. 7G). Tubercles cannot rule this possibility out categorically; however, in the compound lateral areas are smaller and more densely the species is clearly distinct in plate morphology from spaced, resembling those of platelets. all described Ordovician taxa, in particular in the Platelets are polygonal, irregular and typically with several enlargement by marginal accretion of platelets. The small, sharp tubercles (Fig. 7B, F–G). The typical maximum dimension of the larger platelets on the primary surface is 6– apparent expansion of plates by incorporating adjacent 7 lm. The tubercles are separated by sharp channels that give platelets was also described for Palaeoscolex lubovae platelets the appearance of having fused from several smaller, Ivantsov and Wrona, 2004 and Hadimopanella antarc- monotuberculate units (Fig. 7D). In some areas, platelets appear tica Wrona, 2004 and appears to be a widespread, if to remain as these smaller units, without fusion (e.g. Fig. 7D, F). rarely reported, phenomenon; however, it is rarely as The underside of the opposite surface shows that platelets were obvious as here. similarly polygonal, but larger (up to 8–10 lm; Fig. 7C); it is Platelet form is also somewhat distinctive in Bullascolex, assumed that they were similarly tuberculate, as suggested by the especially where formed by microplate fusion to create a presence of small hollows on the underside (Fig. 7C). complex outline. The large plate size and high packing Interplate areas are narrow, with irregular plate separation density also separate the new genus from Palaeoscolex and that diminishes to near zero in places; a typical separation is 10– l closely related genera. Finally, the differentiation of plate- 15 m at the narrowest points (Fig. 7E). Platelets are arranged with their long axes mostly parallel to the adjacent edges of the lets between upper and lower surfaces is unusual, interplate channels, giving an overall braided appearance although dorsoventral distinction in ornament is known (Fig. 7D–E). There are no intercalations and no clear organiza- from other taxa (Ivantsov and Wrona 2004; Topper et al. tion within the interplate areas. 2010). These combined features would be sufficient to separate Bullascolex from existing genera even if the disor- ganized array were not representative of the entire trunk. Genus WERNIA gen. nov.

Derivation of name. After Wern Farm, the location of the type Bullascolex inserere sp. nov. locality of Little Wern Quarry. Wern is a Welsh word for an Figures 4B, 7 alder grove or wet meadow. Gender feminine.

Derivation of name. Latin inserere, to incorporate, referring to Type species. Wernia eximia sp. nov. the expanded plate edges through the addition of fixed platelets. Diagnosis. Palaeoscolecids with plates that lack tubercles Diagnosis. As for genus. and have a longitudinal central groove that bifurcates at both ends; plates arranged in annuli but without intercalations. Holotype. NMW 2010.47G.8 (Fig. 4); small (0.6 mm) but well- Microplates dominantly hexagonal but always polygonal, preserved cuticle fragment showing parts of upper and lower tessellating and supported by polygonal reticulate cuticle. surfaces superimposed; from the mid–late H.? teretiusculus Bio- zone (Llandeilian) of Bailey Einon. Only known specimen. Remarks. At present, the distinctiveness of the unique plate morphology precludes a position within the Palaeo- Description. Holotype consists of a small, roughly square frag- scolecidae or other existing families. The closest superfi- ment of cuticle with both upper and lower surfaces visible in different parts (Fig. 7A); the two surfaces differ in platelet size cial resemblance appears to be with the problematic (compare Fig. 7B–C). It is impossible to determine which is the Cambrogeorginidae (Mu¨ller and Hinz 1992), although in upper and which is the lower, but it is assumed that the animal that case there are many radiating ridges, and it is unclear was bilaterally symmetrical and that the difference broadly whether the group is closely related to palaeoscolecidans reflects dorso-ventral differentiation. The surface with larger at all. 514 PALAEONTOLOGY, VOLUME 55

A

B C D

E F G BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 515

The cuticular reticulation is of uncertain significance, but Description. Holotype consists of a small (<1 mm2) cuticle frag- where published observations for palaeoscolecids are avail- ment, with counterpart; paratype consists of a long cuticle frag- able (Kraft and Mergl 1989; Brock and Cooper 1993, and ment, 0.35 mm wide. Plates arranged in transverse rows l other taxa described here, e.g. Fig. 13E–F), the supporting (Fig. 8E), subcircular and with diameter around 35–40 m. In cuticle is normally a solid, albeit internally structured sheet. the paratype, a plate row consists of a total of 18–20 plates. Each plate shows a single groove network consisting of a longitudinal The peculiar Corallioscolex Mu¨ller and Hinz-Schallreuter, central groove joining the centre of a convergent to straight 1993 also shows a reticulate cuticle, but with the cells hav- transverse groove on one side and two slightly divergent and ing irregular, jagged edges. However, the plates of Corallio- slightly longer grooves on the other that form a shallow ‘V’; the scolex are conservative, and typical of Palaeoscolecidae, typical network is shaped as an arrow (Fig. 8A–C, E). Despite while its platelets form unique coralliomorphic shapes; we some variability in plate morphology, the basic form is moder- suspect that the potential similarity in cuticular structure is ately consistent. In some plates, the transverse elements branch convergent. The only other clear example of cuticular retic- close to the plate margin, and the plate margin may be some- ulation is in the indeterminate palaeoscolecid of Zhang and what lobed between the intersection of the grooves with the Pratt (1996, fig. 3.5, 3.6), in which plates and microplates margin (Fig. 8A–B). Plate rows are paired into annuli, with the are entirely lost, and the remaining cuticle is a mesh that arrow markings on plates pointing outwards, towards annular shows some similarity to that seen in Wernia gen. nov. In boundaries (Fig. 8C, E). Separation of plate rows within an annulus is around 10 lm and 25 lm between annuli. both species, the smaller sclerites appear to have been only The interplate areas were covered by a homogeneous arrange- weakly attached to the cuticle. As there are no plates in ment of small polygonal microplates that are usually hexagonal association with that specimen, it is not possible to assess (retained only locally; Fig. 8C); a few irregular pentagonal or the potential similarity further. heptagonal plates have also been observed. The microplates are Although some cuticles show a reticulate basal layer positioned within a reticulate cuticular mesh that covers the beneath a homogeneous surface layer (Harvey et al. entire interplate area. The inner surface of this cuticle displays 2010), the structure here cannot be explained through circular holes corresponding to the microplate positions, but partial decay exposing a subsurface layer. The reticulation the cuticle narrows externally to form sharp ridges that define in Wernia gen. nov. forms a highly consistent, solid the hexagonal mesh (Fig. 8D). Microplates are inserted onto the polygonal network with clear margins, and at no point is hexagonal spaces and form a precisely articulating array there any remnant of a more continuous surface region (Fig. 8C). Hexagonal spaces in the cuticle are tessellated with contiguous microplate rows aligned transversely and diagonally, that has elsewhere decayed away. In places, the position- rather than longitudinally. Most of the microplates have been ing of microplates onto the reticulate surface also demon- lost, implying only weak attachment to basal cuticle. Microplates strates the pristine condition of the reticulate cuticle. are typically 3–4 lm in diameter (locally up to 6 lm). They are entirely smooth, up to around 1 lm thick, and with sharply defined sides. The external surface appears slightly domed. Wernia eximia sp. nov. Some areas of the mesh appear to be deformed (e.g. Fig. 8C, Figures 4C, 8 upper left and lower middle), as would be expected in a flexible cuticle. However, in these cases, the microplates themselves are Derivation of name. Latin eximius, meaning outstanding; refers frequently elongated and distorted. It is unclear whether this irreg- to the extraordinary preservation of the holotype. ularity in hexagonal form is a fixed feature of each microplate, or whether they were also deformable. The three-dimensional form Diagnosis. As for genus. of the microplates and cuticle would have allowed for a certain degree of flexibility, but a rigid array of precisely articulating and undeformable microplates would have severely limited the flexi- Holotype. NMW 2010.47G.2 (Fig. 4), a moult fragment from the bility of the worm, particularly in relation to transverse bending. Llanvirnian (D. artus Biozone) of Little Wern Quarry, Hundred It is possible instead that the microplates were relatively soft in House, near Llandrindod, Powys. life, and easily deformed along with the cuticular mesh. Paratype. NMW 2010.47G.13; moult fragment from the same locality, bed 8. Remarks. It could be argued that the reticulate cuticle merely represents the impression of the microplates in

FIG. 7. Backscattered Scanning Electron Microscope (SEM) images of Bullascolex inserere gen. et sp. nov., NMW 2010.47G.8. A, overall view of cuticle fragment; B, detail showing plate accretion by incorporation of platelets; C, detail of interplate area showing polygonal platelets; D–E, cuticle area showing superposition of two surfaces, distinguished by electron density of plate surfaces (darker, less dense plates are internal surfaces); F, detail showing compound and monotuberculate platelets, illustrating platelets apparently formed from fusion of smaller units; G, Digitally inverted image showing plate with relict platelet boundaries and tubercles, illustrating accretionary growth. Scale bars represent 100 lm (A), 20 lm (B–C, D–E) and 10 lm (F–G). 516 PALAEONTOLOGY, VOLUME 55

A B

CD

E BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 517 adjacent sediment. However, several features show that it on a much smaller scale than vertebrate dermal armour, is a discrete structure. The sharp contrast everywhere there is no osseous microtexture in this material, and between the reticulate layer and the underlying surface there is no counterpart in vertebrate armour for the inter- seen in backscattered SEM, combined with its local vening platelet areas. Instead, all these features are typical replacement by feathery aluminosilicate crystals (Fig. 8D), for palaeoscolecids, although the specimens represent an indicates that the structure is not a sedimentary mould. entirely novel arrangement of plates. This is confirmed beyond doubt by the presence of iso- The basic structure of Pluoscolex (and to some extent lated sections of the cuticle overlying the edges of plate Loriciscolex gen. nov.) is sufficiently different from surfaces (e.g. arrowed in Fig. 8C). described taxa to indicate a close relationship to each other, but preclude inclusion in our current understand- ing of established families. Some described species, such Genus PLUOSCOLEX gen. nov. as the Hadimopanella-bearing material of Topper et al. (2010) have plates in contact in places, but there they are Derivation of name. After Welsh pluo, feather, for the superficial also in oblique lateral contact and that situation is the appearance of the cuticle. Gender masculine. result of a reduced interplate scleritome, whereas in the new material platelet areas are well developed, but Type species. Pluoscolex linearis sp. nov. restricted in location. The presence of linear sculpture instead of discreet tubercles is a feature of Wernia eximia Diagnosis. Plates fused into presumed transverse linear gen. et sp. nov., as is the homogeneous microplate cover- structures. Ornament consists of tubercles in line along ing of interplate areas, but Wernia plates possessed plate axis, linking across plate boundaries into a continu- grooves rather than ridges and Pluoscolex has a solid ous ridge; in places, individual tubercles no longer dis- rather than reticulate basal cuticle. Relationships to cernible. Platelets between plate ridges extend onto plate known families cannot be established without further taxa surfaces, and typically show a sharp central node. that show a more conservative range of features.

Remarks. The morphology of Pluoscolex gen. nov. is suffi- ciently different to all other palaeoscolecids yet described Pluoscolex linearis sp. nov. that it is reasonable to question whether it is even a pala- Figures 9, 10B eoscolecid. Several features serve to rule out obvious alternative interpretations, however, and support a pala- Derivation of name. Latin linearis, meaning linear, reflecting the eoscolecid affinity. The scleritome fragments show tears dominant fibrous structure. and separation of the mineralized ridges (Fig. 9A) that indicate the species possessed a relatively fragile, continu- Diagnosis. As for genus. ous cuticle on which the mineralized elements were em- placed. Despite demineralization, one specimen yielded a Holotype. NMW 2010.47G.6 (Fig. 9), section of fragmented cuti- substantial phosphorus signal in EDAX analysis, whereas cle showing several plate morphologies, and detail of interplate none has been detected in the surrounding sediment, area. Part and counterpart; from H.? teretiusculus Biozone, implying an originally phosphatic composition. In Llandeilian, Llanvirn, in a loose block at Bailey Einon, near Llan- well-preserved material, plate boundaries are seen within drindod, Powys. one ridge (e.g. Fig. 9H), making these ridges structures composed of phosphatic plates. The presence of discrete Paratypes. NMW 2010.47G.7 and NMW 2010.47G.9, two speci- mens (part and counterpart) showing fragments of cuticle, platelets (Fig. 9B) between the plate ridges rules out a including some morphological features not seen in the holotype. conulariid affinity, and their morphology is very similar Both fragments of cuticle around 10 mm long. Both from the to those of certain palaeoscolecids (such as the smallest type locality. platelets of Bullascolex inserere gen. et sp. nov.). The only other known phosphatic-enhanced cuticle structures in Description. Overall dimensions unknown, but the holotype is the Ordovician are vertebrates, but the structures here are 17 mm long and 6 mm wide, and clearly a small fragment

FIG. 8. Backscattered Scanning Electron Microscope (SEM) images of Wernia eximia gen. et sp. nov., A–D, holotype NMW 2010.47G.2; A–B, typical plate morphology and interplate mesh; C, plate arrangement showing opposite-pointed arrow grooves between adjacent pairs of plate rows; area in small rectangle is enlarged (inset) to show microplate arrangement, and arrow shows cuticle overlying plate surface. Electron-dense (bright) areas are secondary pyrite grains; D, detail of reticulate interplate cuticle, partly replaced by feathery aluminosilicates (inset, enlarging area in rectangle) and with one microplate near upper right (m); E, paratype NMW 2010.47G.13, wide view of cuticle showing plate arrangement and ornament. Scale bars represent 10 lm (A, B, D), 20 lm (C) and 100 lm (E). 518 PALAEONTOLOGY, VOLUME 55

A B

C D

E F

G H BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 519

(Fig. 9A), consisting of many parallel lines of plates. It is assumed ridges would instead be prone to breakage on flexing of that the plate ridges were transverse; it is possible, however, that the trunk. This interpretation of transverse ridges, how- the plate ridges were longitudinal or even oblique, although this ever, implies a large size, with a flattened diameter proba- would cause problems for movement (see Remarks). In all speci- bly of at least 10 mm. mens, plate ridges occasionally end or new ridges appear in gaps, but not in a consistent direction (e.g. Fig. 9E). Plate ridges consist in most cases of elongate plates fused at Genus LORICISCOLEX gen. nov. both ends to adjacent plates (Fig. 9G–H). Plate boundaries are marked, where visible, by constrictions in the plate outline and Derivation of name. From Latin lorica, chain-mail, referring to also in the axial sculpture. The constrictions are occasionally visi- the appearance arising from the platelets that cover the entire ble as narrow regions of interplate cement (e.g. Fig. 9G) forming a surface. Gender masculine. meniscate linkage between somewhat rounded plate terminations. In many cases, plate boundaries are obscured by recrystallized Type species. Loriciscolex cuspidus sp. nov. cracks (Fig. 9D, F) that cut across several plate rows, presumably as a result of sedimentary compaction acting on the weakest points. Typical observed plate width 40 lm, with some areas con- Diagnosis. Palaeoscolecidans with plates possessing pro- sistently 30 lm. Length of plates often unclear, but appears to be nounced, sharp, sinuous, transverse ridge; plates locally in variable, mostly within the range 70–100 lm. Those plates of lateral contact but not entirely fused, arranged in rows width 30 lm are more typically 50 lm long, giving an approxi- but all facing the same direction and not paired into ann- mately constant ratio of plate length:width in observed specimens ulae. Interplate areas with homogeneous microplate cover of around 1.7, but with very significant variation. that extends over plate surface. Plate surface is mostly smooth on lateral surfaces, but the midline shows a series of tubercles or a narrow, slightly undulat- Remarks. The affinities of this unusual taxon are not ing ridge (Fig. 9G). In many cases, there is a ridge with superim- obvious, but certain features are shared with Pluoscolex posed tubercles. The tubercles, where present, vary from small gen. nov. (see discussion of this genus, above). In particu- projections to substantial, ellipsoidal mounds occupying around a third of the plate width (Fig. 9G–H). There appears to be a lar, the interplate area is entirely covered by an array of ⁄ tendency for the axial ridge to be more clearly and consistently small microplates and or platelets, which extend over the defined where tubercles are absent. The ridge generally fades at outer surface of the plates and obscure most of the upper plate boundaries, but in some areas is continuous and sharp surface. The plates of Loriciscolex are in many cases across several plate lengths, indicating either a closer plate sculpted by a sinuous ridge, although the ridge shows no fusion, without meniscate cement separations, or extremely elon- indication of being formed from fused tubercles. In gated individual plates (e.g. Fig. 9C). It is unclear whether the places, however, the plates are somewhat fused (or at least plates are flat either side of the ridge, or slope away from it. positioned adjacently) laterally into transverse rows Interplate areas, as preserved, vary dramatically in width from (Fig. 11E). While it is possible that the platelet ⁄ microplate l virtually zero to over 50 m. Interplate cuticle is uniformly cov- array and plate fusion are convergent in the two genera, ered by an irregular, pseudo-polygonal array of platelets ranging we consider it more likely that these taxa represent a level from 5 to 15 lm in maximum dimension (Fig. 9D, F). The platelets frequently show ornament of small, sharp tubercles; in of divergence within a shared cuticle type and that Pluo- many cases, there is a single central tubercle, either subcircular scolex and Loriciscolex are closely related. or somewhat elongate (Fig. 9B). Other platelets show few or sev- The plates of L. cuspidus in many cases show the ridge eral small tubercles, irregularly distributed over the surface. extended outwards into a single spine of uncertain length. The platelet array at least locally overlies the upper surfaces of Superficially, such a central spine can be compared with plates, reaching close to the axial ridge, and perhaps even cover- several described plate morphologies assigned to ‘Hadimop- ing it (Fig. 9F). anella’ apicata. The name H. apicata was originally applied to isolated plates with a tall central spine, and similar forms Remarks. The plate ridges are assumed to be transverse have now been recovered widely from Early Cambrian acid owing to implications for movement; if transversely digestion residues (e.g. Peel and Larsen 1984; Wrona 2004; arrayed, the cuticle between the ridges would be flexible Topper et al. 2010). Articulated cuticle fragments including without damaging the structure. Longitudinal or oblique this plate morphology have recently been described (Top-

FIG. 9. Light (A) and backscattered Scanning Electron Microscope (SEM) (B–H) images of Pluoscolex linearis gen. et sp. nov. A–F, holotype NMW 2010.47G.1; A, overall view of specimen showing characteristic fibrous appearance of the cuticle; B, detail of microplate arrangement, showing many examples with central tubercles; C–F details of the cuticle showing ridged plate rows, variable inter-row spacing and ornament and variations in microplate array; G–H, paratype NMW 2010.47G.7, details showing plate boundaries and ornament with ridge consisting of linear array of tubercles. Scale bars represent 2 mm (A); 10 lm (B), 100 lm (C–E) and 20 lm (F–H). 520 PALAEONTOLOGY, VOLUME 55

AB

FIG. 10. Palaeoscolecid scleritome reconstructions, with lower left part with surface scleritome removed to reveal plates. A, Loriciscolex cuspidus gen. et sp. nov. B, Pluoscolex linearis gen. et sp. nov. Scale bars represent 40 lm. per et al. 2010) and show that the entire cuticle contained a Holotype. NMW 2010.47G.12 (Fig. 10), well-preserved cuti- variety of plate morphologies. This demonstrates that the cle fragment with platelet detail from the Llanvirnian name H. apicata constitutes a form species rather than a (D. artus Biozone) of Little Wern Quarry, near Llandrindod, biological one. There is also a significant diversity of plate Powys. forms that have been assigned to that name, based solely on the presence of a large central spine, but with wide varia- Paratypes. NMW 2010.47G.4, NMW 2010.47G.14, NMW 2010.47G.15 and NMW 2010.47G.16; cuticle fragments from the tion in the detailed plate morphology. type locality. Despite theoretically being able to apply tentatively the name H. apicata to some plates of Loriciscolex, our mate- Other material. Specimen NMW 2010.47G.1, also from the type rial is not closely allied with the H. apicata-bearing scle- locality, is a poorly preserved fragment that shows enough of the ritomes described by Topper et al. (2010). It differs plate arrangement to be recognizable, but which yields no fur- dramatically in the interplate scleritome, and most occur- ther information. rences of the H. apicata plate morphology probably relate to that type of scleritome. Description. Specimens are preserved in a variety of ways, with some showing the spines broken through in cross-section, and others (including the holotype) showing plate surfaces and ⁄ Loriciscolex cuspidus sp. nov. microplate platelet arrangement. In some fragments, the form of the spines ⁄ ridges on plates is obscured by adhering mate- Figures 10A, 11 rial, either broken from the counterpart or representing min- eralogical infill of the sculpture. Plates are arranged regularly Derivation of name. After the distinctive cuspate morphology of in rows and columns, in most cases slightly separated but some plates. with some plates effectively in contact; and in one specimen (NMW 2010.47G.15a; Fig. 11E), plates have fused along edges Diagnosis. As for genus. to form continuous lines; in this case, the plates are relatively

FIG. 11. Backscattered Scanning Electron Microscope (SEM) images of Loriciscolex cuspidus gen. et sp. nov. A–B, D, G, holotype NMW 2010.47G.12; A–B, wide-scale views showing appearance of well-preserved cuticle; D, detail of cuticle showing microplate array over plate and interplate surfaces; G, detail showing microplates; C, paratype NMW 2010.47G.14, backscattered view of poorly preserved specimen with plate projections seen in cross-section and represented by electron-light material (probably carbonaceous); E, paratype NMW 2010.47G.15, showing area in which plates are almost fusing laterally into continuous lines; F, paratype NMW 2010.47G.16, showing internal surface of cuticle with only plate bases visible. Scale bars represent 100 lm (A–C, F), 20 lm (D–E) and 10 lm (G). BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 521 small and short (40 lm wide by 35 lm long), and it may wide by 50–60 lm long. Plates are broadly rounded except represent either a terminal region of the worm or a younger when in contact with each other, where they become more specimen. In the holotype, plate diameter is around 45 lm square-edged.

A B

C D

E F G 522 PALAEONTOLOGY, VOLUME 55

Plates show a gradation in sculpture, from blunt, sinuous to subcubic form of the microplates is pyrite, but pyrite at nearly straight ridges into extended ridged spines (Fig. 11A, D). this locality occurs dominantly as framboids or isolated When spines are seen in cross-section (Fig. 11C), they often appear cubes (e.g. Fig. 8C). cuspate, with one (presumed anterior-facing) side convex and Spinose plates resembling those of Loriciscolex are rounded, and the other two concave, leading to a (presumed pos- known only from the ‘Hadimopanella’ apicata form spe- terior-facing) cusp. The maximum length of these spines is not cies; they are known widely, but the form taxon includes known, nor whether their termination is sharply pointed or ridged. In the less prominently sculpted plates, a curved, roughly lin- a wide range of morphologies, including different forms ear ridge is present instead; the ridge is much steeper on the in the same scleritome (Topper et al. 2010). The speci- convex (presumed anterior) side than on the concave side. It is mens described there did not possess triangular, cuspate unclear whether the ridge curves anteriorly or posteriorly away spines, and their detailed morphology is quite different. from the surface. Of the isolated material of H. apicata described to date, In one small cuticle fragment showing clear spines, plates that of Wrona (1982) included triangular spines that at show some evidence of segregation across the cuticle, with two least partly resemble those seen here. In the absence of morphological types occurring in distinct regions, apparently articulated type material of that organism, it is not possi- separated dorso-ventrally. Cuspate spines, as described, are the ble to show whether the two forms are at all closely dominant form in one area. Plates in the remaining observed related. No other taxa currently described show the sinu- part of the cuticle have somewhat wider, rounded spines in ous ridge typical of many plates of Loriciscolex. cross-section. The spine sections are broadly elliptical, up to twice as long as wide, without any indication of a clear cusp but in some cases with a sharp posterior or anterior end. It is Indeterminate palaeoscolecid A unclear whether these apparent differences are real or due to dif- Figure 12 ferences in the plane of section through the spine bases. Interplate areas are dominated by a densely packed, regular array Material. NMW 2010.47G.20; poorly preserved fragment of cuti- l of minute (1–2 m diameter) microplates and platelets (a few have cle from the Llanvirnian (D. artus Biozone) of Little Wern a short central spine). The plates are polygonal, never significantly Quarry. elongated, and nearly as thick as wide; this gives the appearance of tessellated cubes in some areas (Fig. 11G). The platelets cover the Description. A single fragment showing closely spaced, rhomboi- outer parts of the plate surfaces and become fainter towards the dal plates with a V-shaped ridge or protuberance rising to a dis- base of the spine or ridge. The texture is continuous from inter- tinct central point or spine. Plate arrangement is a regular plate areas onto the plate surfaces, and no other taxa show similar square grid and without obvious pairing of rows into annuli. textures on the plates, either from this locality or others. The pat- The plates are oriented with the sculpture facing the same direc- tern becomes progressively fainter until it vanishes, suggesting thin- tion, with the apex of the spine often obscured. The plates ning of the microplates towards the plate apex. appear to be in lateral contact in some regions but always slightly separated longitudinally. No evidence of the structure of Remarks. The small size of the microplates makes recog- the interplate areas can be seen. nition of the fine cuticular structures difficult, with potential for misidentification of inorganic structures. Remarks. As far as can be judged from the poor preserva- However, the only likely inorganic interpretation of the tion, this specimen is perhaps closely related to Loriciscolex

AB

FIG. 12. Backscattered Scanning Electron Microscope (SEM) images of indeterminate palaeoscolecid A, NMW 2010.47G.20. A, overall view of cuticle fragment with regular plate array; B, detail of several plates with consistent sculpture. Scale bars represent 100 lm (A) and 10 lm (B). BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 523 cuspidus gen. et sp. nov. It is possible that it represents a culus Biozone, Llandeilian, Llanvirn, in a loose block at Bailey different part or moult stage of the scleritome of L. cuspi- Einon, Powys. dus, but there are differences, particularly in the V-shaped rather than sinuous spine. Given the consistency of this fea- Description. Cuticle section 17 mm long and 3.5 mm wide, pre- ture in the material of L. cuspidus, we prefer to keep the served as a phosphatic sheet and displaying only internal surface specimen separate under open nomenclature. The primary of cuticle. Plates are regularly spaced, arranged in clear trans- features of taxonomic significance are the regular, square verse rows, but their external form and outlines are not visible. arrangement (contrast with Radnorscolex gen. nov. and Ag- Infilling of the plate bases by subcircular patches of crystalline gerscolex gen. nov., in which plates are offset in adjacent material indicates significant relief, but this is consistent with standard Palaeoscolex-type plating; there is no evidence of sub- rows) of closely packed plates with a single sharp, curved stantial spines. Although the plate diameter is unknown, the spine and the apparent absence of row pairing. Without spacing between basal concavities suggests that the plates were evidence of the interplate areas, however, it is not possible separated by clear regions of platelets and ⁄ or microplates. to be certain of its affinity. Remarks. The specimen clearly represents a different spe- Indeterminate palaeoscolecid B cies from the others known at this level (Pluoscolex line- Figure 13A–D aris gen. et sp. nov., Bullascolex inserere gen. et sp. nov.) and shows that at least three genera of palaeoscolecids are Material. NMW 2010.47G.10, NMW 2010.47G.11 and NMW present at Bailey Einon. The plate arrangement here is 2010.47G.22; three cuticle fragments showing similar features, typical of Palaeoscolecidae sensu stricto, but information but without sufficient fine detail to allow a full description. All from the external surface of the cuticle is essential for fur- from the Llanvirnian (D. artus Biozone) of Little Wern Quarry. ther interpretation. Description. Cuticle fragments include some reasonably large areas. These show that the plate arrangement is irregular; in parts the plates form regular transverse rows, but ordering is intermit- Indeterminate palaeoscolecid D tently lost across the cuticle, perhaps taphonomically. Plate sepa- Figure 14 ration is small in most areas of regular arrangement (perhaps in places nonexistent), but wide in other areas. Plates are poorly pre- Material. Lapworth Museum (University of Birmingham) speci- served, but appear to be extremely variable in sculpture. Some men BIRUG:BU2874b-1; single fragment, from the basal D. mur- have a single ridge (Fig. 13C), but others show a short, stellate chisoni Biozone of Bwlch-y-Cefn, Powys. ridge arrangement (Fig. 13B), or discrete tubercles. Within one specimen, plates range from near circular to irregularly triangular Description. Specimen is a cuticle fragment that has been torn in or polygonal and with the longest dimension ranging from 40 to several places along plate rows. Plates are small (around 10 lm 70 lm. Details of interplate areas unknown. diameter), subcircular and very densely packed together. Separa- tion between plates in a row, and between rows, is typically Remarks. This species is remarkable for the local diversity <5 lm and in many places touching. Pairs of plate rows are dif- of plate morphology, size and arrangement. Where seen ficult to recognize consistently. Plates appear to be generally tu- clearly (Fig. 13C) the plates seem reasonably well pre- berculate, but preservation is insufficient to recognize specific served, with no evidence for recrystallization to a degree patterns, or details of the interplate sclerites. sufficient to change the form of the plates. The ridged plates suggest an affiliation with Wernia gen. nov., or per- Remarks. This problematic specimen is sufficiently poorly haps Loriciscolex gen. nov., but other plates are quite dif- preserved that it invites comparison with groups other ferent, and details of the interplate area are entirely that palaeoscolecids. However, it does show a large num- unknown. It is possible that the irregularity of plate ber of subequal-sized circular structures that have uneven arrangement is due to an extremely fragile or unmineral- (probably tuberculate) surfaces (Fig. 14B). These are ized interplate cuticle, which has introduced some variabil- arranged in rows, forming a closely packed array. In ity into the material post-mortem. It clearly differs from places the rows are separated, implying a torn, delicate other species described (herein or elsewhere), despite at cuticle (Fig. 14A). As with the discussion of Pluoscolex least superficial similarities in isolated plate morphology. gen. nov., this does not fit a vertebrate dermal armour interpretation, nor any other known organism to our Indeterminate palaeoscolecid C knowledge, whereas all observed features are consistent Figure 13E–F with a palaeoscolecidan. The very close spacing of the plates is unlike any other Material. NMW 2010.47G.24, a reasonably large folded cuticle material known from the Builth Inlier, but there is insuf- fragment (17 mm long), poorly preserved, from the H.? teretius- ficient information in the specimen to enable a detailed 524 PALAEONTOLOGY, VOLUME 55

A B

C D

E F

FIG. 13. Backscattered (A–D) and secondary electron (E–F) Scanning Electron Microscope (SEM) images of indeterminate palaeoscolecids. A–D, indeterminate palaeoscolecid B; A–B, specimen NMW 2010.47G.22, showing plate arrangement and variation in plate sculpture; C, specimen NMW 2010.47G.11, individual plate with single ridge sculpture; D, specimen NMW 2010.47G.10, region with apparent folded cuticle that yielded a strong phosphorus signature; E–F, indeterminate palaeoscolecid C, NMW 2010.47G.24, regular plate arrangement as seen on internal surface of cuticle, with patches of mineralization infilling plate bases. Scale bars represent 50 lm (A, E–F), 20 lm (B, D) and 10 lm (C). BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 525

A B

FIG. 14. Indeterminate palaeoscolecid D (BIRUG:BU2874b-1). A, overall view of torn cuticle fragment, with detail (inset) showing separation of plate rows from main plate array; B, detail of cuticle showing densely packed plates. Scale bars represent 100 lm (A) and 10 lm (B). comparison with described taxa from elsewhere. Closely Description. Superficially well-preserved fragment, but retaining packed plates are seen in a range of taxa including the few details. Plates are large (70 lm diameter), subcircular and unnamed palaeoscolecids of Topper et al. (2010) and apparently nearly flat without prominent tubercles. Plates are Schistoscolex imbricatus Mu¨ller and Hinz-Schallreuter preserved as moulds with poorly preserved external surfaces that (1993). Even allowing for the limitations of poor preser- show no trace of tubercles, but with some structure preserved on the underside. A pseudo-polygonal pattern of dots in the vation, however, neither have plates that closely resemble centre of the plate and an unmarked rim around the edge could those seen here. indicate the presence of multiple small tubercles on the upper surface. There are no structures that could indicate marginal platelet accretion, and the plate margins are generally smooth. Indeterminate palaeoscolecid E The plates are arranged locally into parallel, perhaps transverse Figure 15 rows, but this regularity is lost across the worm’s diameter. Plate separation is typically only 10–20 lm and variable. No details of Material. NMW 2010.47G.38, a cuticle fragment from the type the interplate area are preserved. section of the Arenig Pontyfenni Formation (B. rushtoni Bioz- one, Fennian), at Pont-y-Fenni, Dyfed (SN23791690; Fortey and Remarks. The plate arrangement and general form are Owens 1987). similar to those of Bullascolex inserere gen. et sp. nov.,

ABC

FIG. 15. Indeterminate palaeoscolecid E, NMW 2010.47G.38. A, overall view of specimen showing non-annular organization; B–C, detail of several plates (internal moulds). Scale bars represent 200 lm (A), 20 lm (B) and 10 lm (C). 526 PALAEONTOLOGY, VOLUME 55 including the plates being arranged isotropically rather the false appearance of low diversity during the Ordovi- than in rows. However, Bullascolex shows irregular plate cian and Silurian. margins reflecting the incorporation of platelets, whereas Palaeoscolecid cuticles have been recovered from seven those in this indeterminate form are more smoothly cir- locations in the area, six of which are ashy shales or cular, with no indication of the existence of mineralized immediately overlying volcanic ash beds, and in two cases, platelets. With no interplate detail preserved, nor confir- both. At the remaining locality (Bailey Einon), specimens mation of the existence of external tubercles, it is not are hosted in loose blocks of fine siltstone in a glacial possible to confirm a close relationship. Because of these deposit, and the exact stratigraphic context of the beds is uncertainties, as well as the difference in age and location, unknown. In contrast, several sites with fossiliferous black we keep this specimen in open nomenclature. mudstones that have been studied over many years have not yielded any palaeoscolecid specimens. There thus appears to be a genuine bias towards slightly coarser sedi- DISCUSSION AND CONCLUSIONS ment, particularly ashy silt and fine sand. At several locali- ties, there is undisturbed lamination preserved in the The faunas described here, despite their limitations, pro- sediment, but rare burrows occur at sediment-ash inter- vide a new perspective on Ordovician palaeoscolecid faces at Wern and Bach-y-Graig, of a diameter consistent diversity. At least 11 species (four in open nomenclature) with the palaeoscolecidan taxa found at each site. Despite are known to be present in the area, from only around 25 reasonably high palaeoscolecidan abundance at some loca- specimens showing sufficient detail to distinguish taxa. tions, these burrows appear as rare, discrete events that No species is recorded from more than one locality, probably reflect either a different organism, or an aberrant implying very low sampling saturation; as well as having behaviour for the group. Our impression is that palaeo- sampled only a proportion (probably small) of the diver- scolecidans preferred relatively coarse, stable, silty sub- sity at each site, this implies that we have sampled only a strates and were dominantly epibenthic. This agrees with small proportion of communities. Assuming a usual hol- the conclusion of Ivantsov and Wrona (2004) based on low curve distribution of taxon abundance, the true material from Siberia. At Bach-y-Graig, palaeoscolecidans diversity of palaeoscolecids in the Builth Inlier sequence is sometimes occur in small clusters; they may have been likely to be several times greater. gregarious, or formed temporary groups owing to, for Those new species that are describable show few simi- example, scavenging behaviour. Where data are available larities to previously known taxa, which are dominantly on the taxonomic composition of a fauna, several species Cambrian. None could be placed into an existing genus, of palaeoscolecidan are present, with one or more com- and four species cannot be placed into existing families, mon species and several rarer ones. Given their low pres- and their taxonomy is left open at family level; the ervation potential, it is likely that they represented a remaining three can be accommodated by the large family significant component of the ecosystem, probably as detri- Palaeoscolecidae. This suggests a rapid diversification of tivores or scavengers (e.g. Han et al. 2007b). palaeoscolecids during the Ordovician (perhaps as part of The various taxa described here show a diverse range the Ordovician Radiation). Alternatively, previously pub- of structures that improve our understanding of palaeos- lished faunas may be biased against certain groups, given colecid palaeobiology. Cuticle fragments isolated by acid that most good material so far described has been digestion are typically phosphatized, but it is unclear what extracted from limestones by acid digestion. If the groups proportion of this is secondary, and what primary bio- represented here dominantly inhabited siliciclastic facies, mineralization. Some structures within plate crowns have they may have been overlooked. been considered suggestive of a primary phosphatic com- All the species in this study appear to be relatively position (Bengtson 1977; Bendix-Almgreen and Peel, small, with the possible exception of Pluoscolex linearis 1988; Hinz et al. 1990), but it is not clear whether this gen. et sp. nov. Whilst specimens <1 mm in diameter applies across a wide range of taxa. The apparent lack of have been recovered from acid digestion of carbonates taphonomic phosphatization in the new material makes (e.g. Mu¨ller and Hinz-Schallreuter 1993), those recorded observations of apparent composition and structure more from siliciclastics so far have generally been much larger reliable. The cuticle in some cases has yielded strong (e.g. Kraft and Mergl 1989; Conway Morris 1997). Those traces of calcium phosphate by EDAX, especially in described so far from these settings are usually assigned creases in the cuticle where dissolution in diagenesis or to the Palaeoscolecidae sensu stricto; it is possible that weathering was incomplete. This offers strong support for many species in this family were larger than those in the idea that plates and perhaps in some species also other families, and their obviousness in comparison with platelets ⁄ microplates were partly phosphatized in life. The the type of material described here may also have led to undersides of plates are normally preserved as electron- BOTTING ET AL.: ORDOVICIAN PALAEOSCOLECIDAN WORMS 527 light material, representing carbon (see Taphonomy sec- partially by the Project-Oriented Hundred Talents Programme tion, above). (grant no. KZCX2-YW-BR-23). We can also demonstrate that some palaeoscolecids possessed a solid basal cuticle and others a reticulate one. Editor. Philip Donoghue Both have previously been described in the literature, but the taxonomically consistent presence of both at the same site in this fauna implies that the difference is genuine REFERENCES and not preservational. The difference may represent a deep division in palaeoscolecid phylogeny, but a reticulate BATHER, F. A. 1920. Protoscolex latus, a new ‘worm’ from cuticle could potentially be convergent; more information Lower Ludlow beds. Annals and Magazine of Natural History, Series, 9 (5), 124–133. is needed. BENDIX-ALMGREEN, S. E. and PEEL, J. S. 1988. Hadim- Plate formation is also confirmed to involve in some opanella from the Lower Cambrian of North Greenland: struc- cases the incorporation of marginal platelets into a solid ture and affinities. Bulletin of the Geological Society of structure (seen in Bullascolex inserere gen. et sp. nov.). In Denmark, 37, 83–103. addition, platelets in that species show evidence of form- BENGTSON, S. 1977. Early Cambrian button-shaped phos- ing by fusion of smaller platelets, blurring the distinction phatic microfossils from the Siberian Platform. Palaeontology, between platelets and microplates. The fused platelet 20, 751–762. structures seen in Bullascolex inserere gen. et sp. nov. BOTTING, J. P. 2000. Palaeoecology and systematics of Ordo- appear to imply that the zone of biomineralization was in vician biotas from Welsh volcaniclastic deposits. Unpublished some cases extended into the regions surrounding the PhD Thesis, University of Birmingham, 368 pp. plates. Alternatively, the structures could have been —— and MUIR, L. A. 2005 (for 2004). The fossil history of the Builth Inlier: insights from a classic area. Transactions of secreted during the early stages of ecdysis as compound the Radnorshire Society, 74, 50–84. organic plates prior to biomineralization. It is currently —— —— 2008. Unravelling causal components of the Ordovi- unclear to what extent the initially secreted organic cuticle cian Radiation: the Builth Inlier (central Wales) as a case possessed the structures seen in the final cuticle. If the study. Lethaia, 41, 111–125. biomineralization process created the plates and platelets BOTTING, J. P. and MUIR, L. A. in press. Fauna and ecol- from a homogeneous organic cuticle, then we should not ogy of the Holothurian Bed, Llandrindod, Wales, UK (Darri- see evidence for plate incorporation. However, we do see wilian, Middle Ordovician), and the oldest articulated fully-formed platelets fused onto the plate edges during holothurian. Palaeontologia Electonica. secretion, which implies that biomineralization was BRIGGS, D. E. G., RAISWELL, R., BOTTRELL, S. H. and focused onto pre-existing organic structures. It is not pos- HATFIELD, D. E. 1996. Controls on the pyritization of sible to say at this stage whether the platelets were exceptionally preserved fossils: an analysis of the Lower Devo- nian Hunsru¨ck Slate of Germany. American Journal of Science, secreted separately and then fused, or whether a single 296, 633–663. zone of biomineralization covering the final compound BROCK, G. A. and COOPER, B. J. 1993. Shelly fossils from plate margins was predefined. the Early Cambrian (Toyonian) Wirrealpa, Aroona Creek, and The level of preservation obtained from the best speci- Ramsay limestones of South Australia. Journal of Paleontology, mens here rivals that of exceptionally preserved, phospha- 67, 758–787. tized material from Cambrian carbonates. They may not CONWAY MORRIS, S. 1977. Fossil priapulid worms. Special be chemically extractable, but it is nonetheless possible to Papers in Palaeontology, 20, 103 pp. collect palaeoscolecid cuticle fragments deliberately at cer- ——1997. The cuticular structure of the 495-Myr-old type species tain sites. We highlight this material as a new source of of the fossil worm Palaeoscolex, P. piscatorum (?Priapulida). 119 information on what appears to have been a much more Zoological Journal of the Linnaean Society, , 69–82. successful Ordovician group than has previously been rec- —— and PEEL, J. S. 2010. New palaeoscolecidan worms from the lower Cambrian: Sirius Passet Fossil-Lagersta¨tte (North ognized. Greenland), Latham Shale (California), and Kinzers Shale (Pennsylvania). Acta Palaeontologica Polonica, 51, 141–156. Acknowledgements. We are grateful to the various landowners —— and ROBISON, R. A. 1986. Middle Cambrian priapulids who have allowed access to sites, but most particularly to Mag- and other soft-bodied fossils from Utah and Spain. The Uni- gie and Mike Ballard of Little Wern; it was they who suggested versity of Kansas Paleontological Contributions, 117, 1–22. we investigate the quarry on their premises. We are also grateful DZIK, J. and KRUMBIEGEL, G. 1989. The oldest ‘ony- for invaluable fieldwork assistance from Tess Ormrod and Vivian chophoran’ Xenusion: a link connecting phyla? Lethaia, 22, Stevens, and to Christian B. Skovsted and an anonymous referee 169–182. for thorough, constructive reviews. JPB is supported by the Chi- ELLES, G. L. 1939. The stratigraphy and faunal succession in nese Academy of Sciences Fellowships for Young International the Ordovician rocks of the Builth-Llandrindod Inlier, Rad- Scientists Grant No. 2010Y2ZA03. This study was supported 528 PALAEONTOLOGY, VOLUME 55

norshire. Quarterly Journal of the Geological Society, London, ——BUDIL, P., CHLUPA´ Cˇ , I., FATKA, O., KRAFT, J., 95, 338–445. MIKULA´ Sˇ , R., MERGL, M. and BRUTHANSOVA´ ,J. FORTEY, R. A. and OWENS, R. M. 1987. The Arenig Series 2003. Fossil assemblages from the Middle Ordovician Sˇa´rka in South Wales. Bulletin of the British Museum, Natural His- Formation at Praha – Cˇ erveny´ vrch Hill (Prague Basin, Bar- tory (Geology), 41, 69–307. randian area). Bulletin of Geosciences, 78, 99–101. GABBOTT, S. E., HOU, X.-G., NORRY, M. and SIVET- MU¨ LLER, K. J. and HINZ, I. 1992. Cambrogeorginidae fam. ER, D. J. 2004. Preservation of Early Cambrian animals of the nov., soft-integumented Problematica from the Middle Chengjiang biota. Geology, 32, 901–904. Cambrian of Australia. Alcheringa, 16, 333–353. GARCI´ A-BELLIDO, D. C., GUTIE´ RREZ-MARCO, J. C. —— and HINZ-SCHALLREUTER, I. 1993. Palaeoscolecid and CHACALTANA, C. A. 2008. First soft-bodied fossil worms from the Middle Cambrian of Australia. Palaeontology, from the Ordovician of Peru. Alcheringa, 32, 313–320. 36, 549–592. GEDIK, I. 1977. Conodont biostratigraphy in the Middle Tau- MURCHISON, R. I. 1839. The Silurian System. John Murray, rus. Bulletin of the Geological Society of Turkey, 20, 34–48. London, 768 pp. GUTIE´ RREZ-MARCO, J. C. and CHACALTANA, C. A. OWENS, R. M., FORTEY, R. A., COPE, J. C. W., 2006. Primer fo´sil de organismo de cuerpo blando en el RUSHTON, A. W. A. and BASSET, M. G. 1982. Trema- Ordovı´cico de Peru´ . XIII Congreso Peruano de Geologı´a, doc faunas from the Carmarthen district, South Wales. Geo- Resu´ menes Extendidos. Sociedad Geolo´gica del Peru´, Publica- logical Magazine, 119, 1–112. cio´n Especial, 7, 627–630. PEEL, J. S. and LARSEN, N. H. 1984. Hadimopanella apicata HAN, J., LIU, J., ZHANG, Z., ZHANG, X. and SHU, D. from the Lower Cambrian of western North Greenland. 2007a. Trunk ornament on the palaeoscolecid worms Rapport Grønlands Geologiske Undersøgelse, 121, 89–96. Cricocosmia and Tabelliscolex from the Early Cambrian SCHOFIELD, D. I., DAVIES, J. R., WATERS, R. A., WIL- Chengjiang deposits of China. Acta Palaeontologica Polonica, BY, P. R., WILLIAMS, M. and WILSON, D. 2004. 52, 423–431. Geology of the Builth Wells district – a brief explanation of the —— ZHANG, Z., LIU, J. and SHU, D. 2007b. Evidence of geological map. Sheet Explanation of the British Geological priapulid scavenging from the Early Cambrian Chengjiang Survey. 1:50 000 Sheet 196 Builth Wells (England and Wales), deposits, southern China. Palaios, 22, 691–694. 34 pp. HARVEY, T. H. P., DONG, X. and DONOGHUE, P. C. J. TOPPER, T. P., BROCK, G. A., SKOVSTED, C. B. and 2010. Are palaeoscolecids ancestral ecdysozoans? Evolution and PATERSON, J. R. 2010. Palaeoscolecid scleritome fragments Development, 12, 177–200. with Hadimopanella plates from the early Cambrian of South HINZ, I., KRAFT, P., MERGL, M. and MU¨ LLER, K. J. Australia. Geological Magazine, 147, 86–97. 1990. The problematic Hadimopanella, Kaimanella and Utah- VAN ROY, P., ORR, P. J., BOTTING, J. P., MUIR, L. A., phospha identified as sclerites of Palaeoscolecida. Lethaia, 23, VINTHER, J., LEFEBVRE, B., EL HARIRI, K. and 217–221. BRIGGS, D. E. G. 2010. Ordovician faunas of Burgess Shale HOU, X. and BERGSTRO¨ M, J. 1994. Palaeoscolecid worms type. Nature, 465, 215–218. may be nematomorphs rather than annelids. Lethaia, 27, WHITTARD, W. F. 1953. Palaeoscolex piscatorum gen. et sp. 11–17. nov., a worm from the Tremadocian of Shropshire. Quarterly HU, S., LI, Y., LUO, H., FU, X., YOU, T., PANG, J., LIU, Journal of the Geological Society, London, 109, 125–135. Q. and STEINER, M. 2008. New record of palaeoscolecids WRONA, R. 1982. Early Cambrian phosphatic microfossils from the early Cambrian of Yunnan, China. Acta Geologica from southern Spitsbergen (Horsund region). Palaeontologia Sinica, 82, 244–248. Polonica, 43, 9–16. IVANTSOV, A. Yu. and WRONA, R. 2004. Articulated —— 2004. Cambrian microfossils from glacial erratics of King palaeoscolecid sclerite arrays from the Lower Cambrian of George Island, Antarctica. Acta Palaeontologica Polonica, 49, eastern Siberia. Acta Geologica Polonica, 54, 1–22. 13–56. KRAFT, P. and MERGL, M. 1989. Worm-like fossils (Palaeos- ZHANG, X.-G. and PRATT, B. R. 1996. Early Cambrian pala- colecida; ?Chaetognatha) from the Lower Ordovician of Bohe- eoscolecid cuticles from Shaanxi, China. Journal of Paleontol- mia. Sbornik Geologicky Veˇd Paleontologie, 30, 9–36. ogy, 70, 275–279.