Search

Preservation of digestive structures in trilobites is generally rare; remains of the alimentary tract have been documented in about eighty of more than twenty thousand described species. Several tens of specimens belonging to five Cambrian and nine Ordovician species from the Barrandian area, Czech Republic, have markedly contributed to the knowledge of the trilobite digestive system. Here, we describe seven exceptionally preserved late holaspid trilobite specimens of species of the genus Dalmanitina collected from Upper Ordovician strata of the Barrandian area. All studied specimens are preserved as internal moulds and exhibit a narrow strip-like structure that runs sagitally or sub-sagitally under the axial lobe of the thoracopygon. These strip-like structures are markedly different from scavenger burrows and are interpreted as remains of the alimentary canal. A slightly expanded anterior-most part of the digestive system is preserved in the cephalic shield of six specimens and is interpreted as a remainder of the anterior midgut. A dark area is seen in the glabellar lobes of three specimens. These dark areas do not represent pyrite concentrations in the hypostome-glabellar cavity, because they contain only small amounts of Fe and S. These areas are interpreted as the remainder of cephalic digestive midgut diverticula, or the "perigastric organ". Quantitative chemical analyses show that in species of Dalmanitina the digestive system is preserved as dark matter containing partly digested food particles and most probably also a higher amount of clay minerals. The described specimens constitute the first well-documented example of digestive structures in the subfamily Dalmanitininae. [ABSTRACT FROM AUTHOR]

The first occurrence of trilobites at ca. 520 Ma is an iconic feature of the Cambrian Explosion. Developing a robust evolutionary view on early Cambrian life is generally hindered by large uncertainties in the ages of fossil finds and their global stratigraphic correlation. We developed an astrochronological interpretation for the Tiout section in Morocco that features some of the oldest trilobite fossils. Our novel approach to incorporating individual astronomical cycle durations in an integrated radioisotopic and astrochronological Bayesian age-depth model results in an age estimate of 519.62 Ma (519.70-519.54 Ma 95% highest posterior distribution) for the first occurrence of trilobites in West Gondwana. This level of precise age estimation is exceptional for biological events in deep time and demonstrates the power of our novel approach. [ABSTRACT FROM AUTHOR]

Studies focused on morphological variation are key for chrono- and biostratigraphy. Morphological variability can be induced by biological and taphonomical biases. Their distinction can become a difficult task due to the lack of population control. Here, we analyse three populations belonging to the genus Protoryctocephalus, two populations from China (P. arcticus and P. balangensis) and a third population of P. arcticus from Greenland. Protoryctocephalus balangensis was collected from the lowermost part of the Kaili Formation where fossils are tectonically deformed while P. arcticus from the 'Tsinghsutung' and Greenland specimens are non-deformed. Geometric morphometrics analysis shows that these three populations indeed belong to the same species. However, the large allometry measured in P. balangensis compared with the 'Tsinghsutung' population and the Greenland population, which is represented by meraspid and early holaspid individuals, suggested that the morphological variation is taphonomically controlled and non-biological. The results suggest that Protoryctocephalus arcticus from the 'Tsinghsutung' Formation is suitable for international correlation, and further studies focus on different aspects such as ontogeny, segment development or fluctuating asymmetry and modularity. [ABSTRACT FROM AUTHOR]

Morphological disparity and taxonomic richness are two major aspects of evolution used to understand biodiversity changes. These metrics are often decoupled in time, particularly during the early history of clades. To assess the pervasiveness of this pattern during the post-acme of a clade, both morphological disparity and taxonomic diversity of the well-documented Devonian trilobites from North Africa were analysed. Morphospace occupancy and body size were estimated and compared to genus richness through time. This study highlights that, during the Early Devonian, morphological disparity of the pygidium and the cephalon strongly increased, whereas cranidium disparity remained low. Interestingly, the pygidium and cephalon morphological dynamics were decoupled. Taxonomic diversity also increased. Then, the Middle Devonian anoxic events affected the trilobite communities with simultaneous drastic loss of both morphologies and taxonomic richness. This coupling between diversity and disparity dynamics could be explained by either the intensity of extinctions or strong internal constraints. Finally, the weak Famennian recovery of both disparity and diversity did not reach the Early Devonian levels, thus making trilobites a 'dead clade walking' during their late evolutionary history. Devonian trilobite families are thus identified as 'Bottom-Heavy Clades', characterised by a diversity peak at the end of their history. [ABSTRACT FROM AUTHOR]

Trace fossils can illustrate important palaeobiological interactions within a fossil assemblage that body fossils do not record. A group of trace fossils that showcase feeding ecology, and evidence of predation, are coprolites. Shelly coprolites are useful for documenting records of durophagous predators or scavengers within a substrate. To expand the record of these traces from the lower Paleozoic, here we present 12 shelly coprolites from the Late Ordovician (Katian) Bohdalec Formation of the Czech Republic. These coprolites contain abundant Onnia superba (Bancroft, 1929) fragments with marked breakages across exoskeletal sections. Rarer evidence for gastropods, bivalves, crinoid debris, and another indeterminate shelly material are also observed within the coprolites. While the producer cannot be irrevocably determined, possible options are explored. We propose that larger, co-occurring trilobites and predatory cephalopods likely made the majority of coprolites. Furthermore, large unbiomineralised arthropods, such as phyllocarids and eurypterids are highlighted as possible producers. Continued examination of these trace fossils will highlight when and where similar interactions between trophic levels had occurred. [ABSTRACT FROM AUTHOR]

Problems surrounding the identification and systematics of taxa belonging to the trilobite family Ellipsocephalidae have been discussed for several decades. The ellipsocephalid genus Strenuaeva is revised herein on the basis of material from Spain, including the type material of the identified species together with newly collected specimens from the Ossa-Morena Zone and the Iberian Chains. Two species are recognized as valid for these regions: S. sampelayoi and S. incondita. The species ' S. melendezi ' and ' Ellipsostrenua alanisiana ' from Spain, as well as ' S. marocana ' from Morocco, are considered junior synonyms of S. sampelayoi. Previous assignment of the Spanish species to Issafeniella is rejected. The abundant available material of S. sampelayoi made it possible to evaluate the taphonomical role in the preservation of some characters and to recognize intraspecific variability similar to that described in S. inflata from Baltica, reinforcing its assignment to Strenuaeva. Biostratigraphically, Strenuaeva ranges from uppermost Cambrian Stage 3 to uppermost Cambrian Stage 4. In Iberia, it is restricted to the middle Marianian in the Ossa-Morena Zone, whereas it is known from the lowermost middle Marianian to the lowermost upper Marianian in the Iberian Chains. Strenuaeva is known from Baltica (Scandinavia and Holy Cross Mountains, Poland), Iberia (Spain), Morocco and, possibly, western Avalonia (Newfoundland), hence being a characteristic genus of the Acadobaltic faunal Province. [ABSTRACT FROM AUTHOR]

The lower Cambrian trilobite Eodontopleura Chien and Lin in Yin and Lee 1978 from South China was once thought to be an ancestor of the post-Cambrian trilobite Odontopleurida due to its unique odontopleurid-like glabella. Here, we revise this genus as an oryctocephalid based on the articulated exoskeletons found recently in the Balang Formation (Cambrian Series 2, Stage 4) of South China. Phylogenetic analysis supports that Eodontopleura represents a typical example of trilobite convergent evolution, suggesting that even the most exclusive features may have been repeated in the evolutionary history of trilobites, which additionally reminds us of the universality of convergence and its possible misleading effect on trilobite taxonomic studies. Moreover, our discovery indicates the remarkable specialisation potential of oryctocephalids, which highlights the evolution of early deep-water trilobites. [ABSTRACT FROM AUTHOR]

A new species of bubble-headed trilobite, Staurocephalus oliveae sp. nov., is described from 250 specimens collected from a recently discovered locality in the Sholeshook Limestone Formation (upper Katian, Upper Ordovician; Ashgill, Cautleyan Zone 1 equivalent) in the village of Llanddowror, Carmarthenshire. Although no fully articulated specimens were found, the material is the most abundant and well-preserved of any Ordovician Staurocephalus species known from Britain and Ireland, and enables the complicated 3D structure of its cephalon to be reconstructed. Staurocephalus oliveae sp. nov. is the earliest representative of the genus recorded in Avalonia, following its presumed migration into the area from Laurentia or Baltica. Recognition of this Cautleyan species resurrects the potential usefulness of the long established, widely distributed, Staurocephalus clavifrons as a latest Katian (= Rawtheyan) indicator. [ABSTRACT FROM AUTHOR]

A new species of bubble-headed trilobite, Staurocephalus oliveae sp. nov., is described from 250 specimens collected from a recently discovered locality in the Sholeshook Limestone Formation (upper Katian, Upper Ordovician; Ashgill, Cautleyan Zone 1 equivalent) in the village of Llanddowror, Carmarthenshire. Although no fully articulated specimens were found, the material is the most abundant and well-preserved of any Ordovician Staurocephalus species known from Britain and Ireland, and enables the complicated 3D structure of its cephalon to be reconstructed. Staurocephalus oliveae sp. nov. is the earliest representative of the genus recorded in Avalonia, following its presumed migration into the area from Laurentia or Baltica. Recognition of this Cautleyan species resurrects the potential usefulness of the long established, widely distributed, Staurocephalus clavifrons as a latest Katian (= Rawtheyan) indicator. [ABSTRACT FROM AUTHOR]

• The Floian fauna from SE Sardinia, mostly Trilobites, corresponds to the Raphiophorid biofacies. • Taihungshania genus is a useful tool in Lower Ordovician palaeo(bio)geography. • Chinese affinity is reassessed in SE Sardinia, Montagne Noire, Alborz, Taurides and UAE. • The location of Mediterranean terranes is discussed along the Gondwana margin. A systematic description of the so far unique trilobite fauna and the associated biota from the Arenarie di San Vito Formation, in the outcrops close to the abandoned Tacconis mine (allochthonous nappe zone, Sarrabus, SE Sardinia, Italy), proves the occurrence of Taihungshania shui landayranensis , Ampyx priscus , Asaphellus sp., Merlinia sp., Niobe fourneti? , Geragnostus sp. and Symphysurus sp., accompanied by several taxa of graptolites, ichnofossils and less common bivalves, gastropods, cephalopods and hyolithids. The taphonomical signature, sedimentary structures and "Raphiophorid biofacies" clearly argue for an early Floian age and a median platform (i.e., offshore to shoreface) depositional environment. The occurrence of T. shui landayranensis in Sardinia allows us to determine the age of the Arenarie di San Vito Formation (just below the Sarrabese unconformity) and to discuss the palaeobiogeographical affinities highlighting the value of the " Taihungshania bioprovince". The Tacconis trilobite fauna displays close affinities with Montagne Noire in France, Taurides in Turkey, Alborz in Iran, and south China, placing the SE Sardinia allochthonous area in a global Ordovician palaeogeographic sketch. A brief discussion on relationships and palaeobiogeographical affinities between the Sardinian nappe zone and the autochthonous "foreland" Sulcis-Iglesiente, which are adjacent today, strongly suggests a separation during the Ordovician, although both areas pertain to the Gondwana margin. [ABSTRACT FROM AUTHOR]

The Lower Ordovician Fezouata Shale is renowned for its exceptionally-preserved euarthropod fossils including numerous species of trilobites, some of which show remains of appendages and traces of the digestive system. Herein, we describe the early developmental stages of at least nine trilobite species from the Tremadocian strata of the Fezouata Shale, namely Platypeltoides magrebiensis , Nileus deynouxi , Symphysurus ebbestadi , Asaphellus sp., Megistaspis (Ekeraspis) hammondi , Orometopus sp., Anacheirurus adserai , Bavarilla zemmourensis , Indiligens sp., and several specimens of undetermined protaspides. This study considerably expands our knowledge of the development of early Ordovician trilobites. The preservation of appendages in the early stages of N. deynouxi and S. ebbestadi , and remains of the digestive tract in the latter species, suggests that some immature trilobites had similar morphology and anatomy as the adult individuals. Early developmental stages of Indiligens sp. might have fed and/or hidden on graptolites and demosponges. The extraordinarily large size of the early post-embryonic stages of P. magrebiensis , S. ebbestadi , Orometopus sp., Asaphellus sp., and undetermined protaspides suggests that these trilobites might have hatched from yolk-rich eggs. The presence of several trilobite species with notably large post-embryonic stages in the Fezouata Shale might be explained by seasonal or low productivity in the high-latitude margin of Gondwana. [ABSTRACT FROM AUTHOR]

A poorly diverse trilobite assemblage is described from the Tremadocian strata (Tangissart Member of the Mousty Formation; Chevlipont Formation) of the Brabant Massif. These specimens represent so far the oldest trilobite record from Belgium. The recorded taxa, identified as Platypeltoides cf. croftii , Macropyge ? sp., and Asaphidae indet., resemble contemporaneous trilobites from other parts of Avalonia (e.g., Wales, Shropshire) as well as some others from high-latitude Gondwana (Morocco). The nileid species P. cf. croftii suggests that the Tangissart Member of the Mousty Formation was likely deposited in deeper offshore environments on the open shelf of Avalonia. Morphological similarities between P. cf. croftii from the Brabant Massif, P. croftii from the UK, and P. magrebiensis from Morocco suggest close faunal interchange across the narrow Rheic Ocean. [ABSTRACT FROM AUTHOR]

A unique, new palaeotaxodont (Protobranchia) genus and species, Yuexiconcha duplicata Zhang, Niu and Johnston, is proposed and described. It is characterized by: a medium-sized, transversely elongated, sub-elliptical shell; heterotaxodont dentition; and posterior tooth row consisting of crowded gradidentate dentition, partially and dorsally overlapped by an additional tooth row that emanates from the beak to form a bitaxodont dentition (new term). Most significantly, a prominent resilifer separates the anterior and posterior tooth rows and shows slight to moderate excavation into the hinge-plate. While a resilifer indicates phylogenetic proximity with Nuculoidea , Yuexiconcha nov. gen. is readily distinguished by its bitaxodont posterior dentition and a more elongate posterior shell lobe and so is provisionally placed in the Family Nuculidae, Order Nuculida. The hinge of Yuexiconcha nov. gen. indicates that a resilifer in palaeotaxodonts first developed in the Ordovician, rather than in the Silurian (Wenlock) as thought previously. Specimens described herein were collected from a fine-grained siliciclastic rock unit in the upper part of the Dongchong Formation in western Guangdong, South China. Other components of the biota occurring with the bivalves are uncommon and include trilobites and brachiopods that indicate a late Middle–early Late Ordovician (late Darriwilian–early Sandbian) age. [ABSTRACT FROM AUTHOR]

The tectonic affinity of the Korean Peninsula in reference to the Permo-Triassic collision of the Sino-Korean Craton (SKC) and the South China Craton (SCC) has been in the center of debates over the last three decades. Since the Imjingang Belt that runs through the middle part of the Korean Peninsula is thought to represent the major tectonic boundary, most part of North Korea, including the "Pyeongnam Basin" in the southern part, has been regarded as part of the SKC. However, differences in stratigraphy and the fossil occurrence have been recognized by local geologists between the southern part of "the Pyeongnam Basin" (SPB) and the northern part of the "Pyeongnam Basin" (NPB), and which have hardly been considered for the paleogeographical affinity of the regions so far. Here we provide a comprehensive review on 1,072 fossil taxa from the Neoproterozoic to middle Paleozoic sedimentary successions of North Korea, and utilize the data for determining tectonic affinity of the regions. Especailly, Cambrian trilobite genera from the SPB and NPB have been quantitatively compared with those of North China (the SKC) and the SCC, using similarity indices, the non-metric multidimensional scaling (NMDS), and PerMANOVA test. The results have revealed that the SPB is tied to the SCC, not to North China (the SKC), whereas the NPB is closely related to North China. The SCC affinity of the SPB is corroborated by stratigraphical features, such as the presence of the Precambrian–Cambrian boundary and the middle Paleozoic strata, which are largely absent in the SKC. Our results demonstrate that the SPB region likely originated from to the SCC, and thus further suggest that the collisional boundary of supracrustal rocks between the SKC and the SCC in the Korean Peninsula corresponds to the boundary of the NPB and the SPB. Accordingly, the extent of the newly-defined Pyeongnam Basin is restricted to the traditional NPB region. The SPB region is included in the extent of the newly-proposed Hwanghae District, which is bounded to the east with the Imjingang Belt by the Ryesonggang Fault. The South China Craton-originated rocks of the Hwanghae District and the Imjingang Belt are collectively termed the South China-affinity terrane (SAT). [ABSTRACT FROM AUTHOR]

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

Parabadiella is considered the earliest trilobite representative in South China and was originally recovered from the mid-upper part of the Guojiaba Formation, in Liangshan section. Previous studies suggested that the earliest brachiopod co-occurred with the oldest trilobite, and the Parabadiella–Eoobolus association from the Xihaoping Member (Cambrian Series 2, Stage 3), in southern Shaanxi was considered the first trilobite–brachiopod assemblage zone in South China. Therein, brachiopods occur together with trilobites recovered in Well JS103 seemingly extending the First Appearance Datum deeply in the lower Cambrian at the central Yangtze Platform. Well JS103 is a shale gas exploration well that targets the lower Cambrian Jiulaodong Formation in southern Sichuan Basin. The uppermost fossiliferous layers are siliciclastic rocks nearly 10 metres thick. Here, two distinct trilobite zones are found, including the lower Parabadiella Zone and the upper Wutingaspis–Eoredlichia Zone. Additionally, the lowermost part of the Guojiaba Formation is poorly fossiliferous, and ranges from 200 to 250 metres in thickness. Thus, the discovery of the brachiopod–trilobite assemblage provides new insights into the biostratigraphy in Sichuan and is of great potentials for biostratigraphic correlation of the siliciclastic rocks in the western margin of the Yangtze Platform. [ABSTRACT FROM AUTHOR]

Pterygotid eurypterids (Chelicerata) were all regarded as active apex nektonic predators, particularly in the Silurian. The chelicerae and lateral eyes of Acutiramus cummingsi were then interpreted as being inconsistent with a predatory lifestyle. Jaekelopterus, Pterygotus and Erettopterus were interpreted as having more acute vision than Acutiramus, but their chelicerae implied they had different ecologies, with not all taxa as top predators. The chelicerae of Acutiramus are here interpreted as being much more robust than was previously assumed, and their eyes as adapted to hunting at depth, at night or in murky water, so neither precludes a predatory lifestyle. Previous models of the mode of life of pterygotid eurypterids are assessed, based on a review of their trace fossils, functional morphology and a new analysis of their biotic associations. All pterygotid taxa are here interpreted as slow swimming vagrant and ambush predators, using their chelicerae to rapidly capture prey, and their more robust coxal gnathobases and metastoma to process it. Slimonia, and Acutiramus with more gracile cutting chelicerae, tend to associate with, and likely specialised on, lightly-armoured phyllocarid crustaceans. Erettopterus and Pterygotus, with more robust chelicerae, tend to associate with more heavily armoured thelodonts and osteostracans, respectively. Jaekelopterus tend to associate with osteicthyans, placoderms and pteraspids. Praedichnia (predation traces) on the pteraspids Lechriaspis and Larnovaspis, eurypterids Eurypterus and Acutiramus and trilobite Spinisscutellum, and their coprolites, provide further evidence for such predatory interactions. The cheliceral morphology, visual acuity, associations and fossil record all support the hypothesis that Acutiramus is actually more basal to Jaekelopterus and Pterygotus, the largest ever arthropods, with Jaekelopterus now estimated at 2.59 m long. [ABSTRACT FROM AUTHOR]

Floian, Early Ordovician trilobites are systematically described and revised based on new material from the middle part of the Duoquanshan Formation of the Shihuigou area, northern Qinghai Province, northwest China. The fauna that lived on the shallow-water carbonate platform comprises three species belonging to two families, i.e., Tsaidamaspis diarmatus, Zhiyia tsinghaiensis, and Liexiaspis sp. indeterminate. It exhibits a strong endemicity to the Olongbluk terrane. The new isoteline genus Zhiyia is established on the basis of the material from the Olongbluk terrane and South China palaeoplate, and is characterized by its: (i) almost obsolete cephalic and pygidial axial furrows; (ii) flattened anterior border and narrow (sag., exsag.) occipital ring; (iii) bilobed hypostome with a shallow median notch and a small triangular median projection; (iv) subsemicircular pygidium with wide pygidial axis and border. Faunal evidence indicates that the palaeogeographic position of the Olongbluk terrane may have been situated closer to the South China palaeoplate rather than the North China palaeoplate during the Floian. [ABSTRACT FROM AUTHOR]

Floian, Early Ordovician trilobites are systematically described and revised based on new material from the middle part of the Duoquanshan Formation of the Shihuigou area, northern Qinghai Province, northwest China. The fauna that lived on the shallow-water carbonate platform comprises three species belonging to two families, i.e., Tsaidamaspis diarmatus, Zhiyia tsinghaiensis, and Liexiaspis sp. indeterminate. It exhibits a strong endemicity to the Olongbluk terrane. The new isoteline genus Zhiyia is established on the basis of the material from the Olongbluk terrane and South China palaeoplate, and is characterized by its: (i) almost obsolete cephalic and pygidial axial furrows; (ii) flattened anterior border and narrow (sag., exsag.) occipital ring; (iii) bilobed hypostome with a shallow median notch and a small triangular median projection; (iv) subsemicircular pygidium with wide pygidial axis and border. Faunal evidence indicates that the palaeogeographic position of the Olongbluk terrane may have been situated closer to the South China palaeoplate rather than the North China palaeoplate during the Floian. [ABSTRACT FROM AUTHOR]

Chelediscus is reported for the first time from the Cambrian of Western Gondwana. This eodiscide genus is known from the Cambrian Series 2 of England, Newfoundland, New York, Sweden and Russia. An emended diagnosis for the genus is provided, which is here assigned to Calodiscidae, and a new species, Chelediscus garzoni sp. nov. is described. The species comes from Cumbres de San Bartolomé municipality, northern Huelva province (Spain), in the upper part of the 'Cumbres beds' formation. This horizon is assigned to the regional upper Marianian Stage based on the trilobite assemblage (Serrodiscus Zone), correlating with the lowermost Cambrian Stage 4. Chelediscus carus Repina from the Botoman of Siberia and this Spanish occurrence are the earliest appearances of the genus. The new species suggests that a smooth, unlobed glabella is primitive for the genus. Chelediscus in Spain strengthens faunal links with Avalonia, Baltica, Siberia and Laurentia. urn:lsid:zoobank.org:act:32A57670-48E7-470E-B7AD-A0ACACB2E5C6 [ABSTRACT FROM AUTHOR]

The Cambrian (Miaolingian; Wuliuan) Spence Shale Lagerstätte of northern Utah and southern Idaho is one of the most diverse Burgess Shale-type deposits of Laurentia. It yields a diverse fauna consisting of abundant biomineralized and locally abundant soft-bodied fossils, along a range of environments from shallow-water carbonates to deep-shelf dark shales. Panarthropods are the dominant component throughout the deposit, both in time and space, but whereas the trilobites and agnostoids are abundant, most of the soft-bodied taxa are only known from very few specimens. Additionally, the knowledge of soft-bodied panarthropods is currently largely limited to locations in the Wellsville Mountains of northeastern Utah. This contribution describes 21 new soft-bodied panarthropods from six locations, including the first occurrences of soft-bodied panarthropods in the High-Creek, Smithfield Creek, Spence Gulch, and Two-Mile Canyon localities. Additionally, we report the presence of bradoriids— i.e., Branchiocaris pretiosa Resser, 1929, Perspicaris ? dilatus Robison and Richards, 1981, Naraoia ? sp. indet., Thelxiope cf. T. palaeothalassia Simonetta and Delle Cave, 1975, and Tuzoia guntheri Robison and Richards, 1981—for the first time from the Spence Shale Lagerstätte; the first reported occurrence outside of the Burgess Shale for Thelxiope cf. T. palaeothalassia ; and the first Wuliuan occurrence of Tuzoia guntheri. We also report on a new hurdiid carapace element and additional specimens of Buccaspinea cooperi ? Pates et al., 2021, Dioxycaris argenta Walcott, 1886, Hurdia sp. indet., and Tuzoia retifera Walcott, 1912. This new material improves our understanding of the panarthropod fauna of the Spence Shale Lagerstätte and substantially increases our understanding of the distribution of the described taxa in time and space. [ABSTRACT FROM AUTHOR]

The Waukesha Biota (Brandon Bridge Formation Lagerstätte) is a diverse assemblage of early Silurian (437 Ma) shallow marine fossils from Wisconsin, USA. Their exceptional preservation, in finely laminated dolomitic mudstones, was mediated by tidally‐influenced conditions and/or microbial entombment. Shelly biomineralized animals are rare, but soft‐bodied organisms are common. Arthropods dominate, including trilobites, phyllocarids, ostracodes, a thylacocephalan, a synziphosurine and various enigmatic groups. The fauna also includes evolutionary 'holdovers', such as palaeoscolecids and a lobopodian. [ABSTRACT FROM AUTHOR]

Phacopidae were a successful family of the Silurian–Devonian period. Although their diversity trends are well identified, their shape evolution is unknown; their morphology often considered to be conservative. We have quantified these morphologies using geometric morphometrics (landmarks) and investigated their evolution using morphological disparity indices. Results identified morphological variations between the genera, and through time. Phacopids differ from each other by the position of the facial suture linked to the size of the visual complex, the shape of the genal angle and the elongation of both cephalon and pygidium. The morphological disparity of cephala was high from the Silurian, contrary to that of pygidia. Subsequently, the morphological disparity increased in the Early Devonian with the development of narrow cephala and triangular pygidia. Morphological disparity was greater in the Emsian for both cephala and pygidia, more than 50 myr after the origination of phacopids. It constituted a perfect example illustrating that a peak of biodiversity does not necessarily happen in the early history of a clade. Subsequently, a strong decrease of morphological disparity occurred in the Middle Devonian, in conjunction with sea‐level changes and anoxic events. Taxonomic richness and morphological disparity declined strongly in the Givetian, in a non‐random extinction affecting particularly blind genera. The morphological disparity remained low in the Frasnian despite progressive eye reduction influenced by environmental changes. An extensive recovery occurred in the Famennian with an important increase of both taxonomic and morphological diversity. The Hangenberg event caused the final extinction of phacopids. [ABSTRACT FROM AUTHOR]

Trilobites were recovered from four cores of the middle Cambrian Earlie Formation in southwestern Saskatchewan. Fossils occur in silty mudstone with interbedded siltstone and limestone, deposited in the inner detrital belt of the craton interior, under low-energy, subtidal conditions. Taxa identified include Kootenia dawsoni (Walcott 1889), Asaphiscus wheeleri Meek 1873, Blainia gregaria Walcott 1916b, Parehmania princeps Deiss 1939b, Ehmania weedi Resser 1935, Bolaspis labrosa (Walcott 1916a), and corynexochid gen. and sp. indet., indicating an age ranging from the lower to upper Altiocculus subzone of the Ehmaniella Zone, upper Wuliuan Stage. The upper Eldon and lower Pika formations located farther west in subsurface Alberta and the Rocky Mountains are considered to be age equivalent. Biostratigraphy confirms that strata overlying the Basal Sandstone Unit are diachronous and become progressively younger eastward. The trilobite fauna is lower in diversity relative to those in temporally equivalent units in the Rocky Mountains as well as the Great Basin, indicating that it may have experienced some environmental stressors, and that seafloor colonization was sporadic and opportunistic. [ABSTRACT FROM AUTHOR]

The article focuses on the evolutionary significance of enrolment behavior in arthropods, particularly trilobites, highlighting its adaptive role in protecting vulnerable body parts and its connection to the challenges of arthropod growth with rigid exoskeletons. Topics discussed include the various enrolment mechanisms observed in different arthropod groups, the developmental variability in enrolment styles, and the biomechanical modeling of trilobite enrolment behavior.

Encrinurids are common in Ordovician and Silurian strata but whether they survived into the Early Devonian is still controversial. This paper documents the encrinurid Batocara sp. near the Silurian–Devonian boundary in western Junggar, Xinjiang. The highest horizon of Batocara sp. is located above the first appearance datum of the Devonian conodont Caudicriodus , confirming that encrinurids may cross the Silurian–Devonian boundary. The presence of Caudicriodus angustoides bidentatus , Zieglerodina planilingu and plate-type loboliths of scyphocrinoids above the highest horizon of Batocara sp. indicates that encrinurids here extend only into the lower part of the first conodont zone of the Lochkovian (i.e., Caudicriodus hesperius Biozone). Encrinurids are widely distributed and easily recognized, and unlike graptolites and conodonts are not controlled by lithofacies. Therefore, it might be possible to use the highest horizon of encrinurids as indicator fossils to identify the approximate position of the Silurian–Devonian boundary in areas or sections where graptolites and conodonts are not present, and at least in northwest China. [ABSTRACT FROM AUTHOR]

Trilobite moulting behaviour has been extensively investigated. However, exuviae in eodiscid trilobites are poorly known. Here, we report two eodiscid trilobite specimens, Tsunyidiscus niutitangensis and Tsunyidiscus sp., showing Somersault configuration from the Niutitang Formation and Mingxinsi Formation of South China, respectively (Cambrian Series 2, Stage 3). The arrangements of the exoskeletons indicate that the two specimens are the slightly disturbed and undisturbed exuviae. The impression of the lower cephalic unit (LCU) displays the rostral plate in Tsunyidiscus niutitangensis. The exuviae showing the LCU inverted anteriorly under the trunk. The opening of the facial and rostral sutures would have allowed the emergence of the post-ecdysial trilobite with the partial enrolment of exoskeleton. Moreover, our discovery indicates a Somersault configuration which employed the facial and rostral sutures to create an anterior exuvial gape that also exists in eodiscid trilobites besides redlichiid trilobites, corynexochid trilobites and ptychopariid trilobites during the Cambrian. [ABSTRACT FROM AUTHOR]

The Middle Devonian (lower–middle Givetian) Hamilton Group of New York State is an iconic unit in North America, which has contributed many key concepts in stratigraphy, sedimentary geology, paleoecology, and evolution. This interval comprises a 100- to 1200-m-thick clastic wedge, shed westward from the Acadian Mountains, with thin but persistent carbonates. Despite the rich and diverse invertebrate fauna that consists of more than 300 species of corals, bryozoans, brachiopods, mollusks, echinoderms, and trilobites, the age of the Hamilton Group is rather poorly constrained in terms of chronostratigraphy owing to the rarity of biostratigraphically useful conodonts and goniatites. The upper part of the Hamilton Group that is the focus of this paper apparently belongs to the Polygnathus timorensis to middle Polygnathus ansatus Conodont chronozones. The middle to upper Hamilton Group in New York State comprises three formations—the Skaneateles, Ludlowville, and Moscow—each defined as an interval delimited with a sharply based fossiliferous limestone-calcareous siltstone; these formations are interpreted as containing condensed transgressive deposits overlain by thicker highstand to falling-stage shales, mudstones/siltstones, and sandstones. The eastern equivalents of these formations are dominated by fine-grained sandstones and siltstones and include two formations: the Panther Mountain Formation, equivalent to the Skaneateles and Ludlowville formations combined, and the Cooperstown Formation, equivalent to the Moscow Formation. In the present paper, we review, revise and update a hierarchical framework of lithostratigraphic subdivisions of these formations, including 24 members (four new), 50 submembers (more than half newly proposed or redefined; 14 informal at this time), and more than 80 named beds, both formal and informal. This refined lithostratigraphy provides an excellent framework for studying high-resolution sequence stratigraphy. As defined herein, members and most submembers represent high-frequency depositional sequences with basal shell-rich carbonates and abrupt flooding surfaces that mark the bases of highstand deposits. Not only are most of the members and submembers traceable across western and central New York, but also to a lesser extent into adjacent regions that include southern Ontario, Ohio, the Michigan Basin, and northeastern Pennsylvania. Nevertheless, much work on correlation remains to be done in eastern New York and central Pennsylvania, where local progradation of siliciclastics and expansion of successions obscures many of the finer scale features. [ABSTRACT FROM AUTHOR]

The artiopodans, consisting of trilobites and their relatives, were a major euarthropod group in the Paleozoic. Since the first discovery of Naraoia from the Chengjiang fauna, a significant number of artiopodans have been subsequently found in China. Here we describe three new artiopodan species from the lower Cambrian Chengjiang fauna (Cambrian Series 2, Stage 3) at Malong, Yunnan, China. Zhugeia acuticaudata gen. et sp. nov. is defined by a semielliptical cephalon with long genal spines, nine overlapping thoracic tergites, and a pygidium with an elongated needle-like median spine. Its cephalic shield covers multiple anterior thoracic tergites. Tonglaiia bispinosa gen. et sp. nov. is defined by a suboval cephalon, seven thoracic tergites, and a micropygous pygidium with a pair of parallel posteriormost spines. Sidneyia malongensis sp. nov., a new occurrence of Sidneyia from South China, is defined by a crescent-shaped cephalon, eight imbricated tergites, and an abdomen consisting of two cylindrical segments and a tail fluke. The evolutionary affinities of these new taxa are reconstructed and discussed in a phylogenetic context. Phylogenetic analyses resolve Z. acuticaudata among the xandarellids and T. bispinosa gen. et sp. nov. as a trilobitomorph with an uncertain placement, The discovery of three new species improves the biodiversity of artiopodans from the Cambrian and the Chengjiang fauna. [ABSTRACT FROM AUTHOR]

The artiopodans, consisting of trilobites and their relatives, were a major euarthropod group in the Paleozoic. Since the first discovery of Naraoia from the Chengjiang fauna, a significant number of artiopodans have been subsequently found in China. Here we describe three new artiopodan species from the lower Cambrian Chengjiang fauna (Cambrian Series 2, Stage 3) at Malong, Yunnan, China. Zhugeia acuticaudata gen. et sp. nov. is defined by a semielliptical cephalon with long genal spines, nine overlapping thoracic tergites, and a pygidium with an elongated needle-like median spine. Its cephalic shield covers multiple anterior thoracic tergites. Tonglaiia bispinosa gen. et sp. nov. is defined by a suboval cephalon, seven thoracic tergites, and a micropygous pygidium with a pair of parallel posteriormost spines. Sidneyia malongensis sp. nov., a new occurrence of Sidneyia from South China, is defined by a crescent-shaped cephalon, eight imbricated tergites, and an abdomen consisting of two cylindrical segments and a tail fluke. The evolutionary affinities of these new taxa are reconstructed and discussed in a phylogenetic context. Phylogenetic analyses resolve Z. acuticaudata among the xandarellids and T. bispinosa gen. et sp. nov. as a trilobitomorph with an uncertain placement, The discovery of three new species improves the biodiversity of artiopodans from the Cambrian and the Chengjiang fauna. [ABSTRACT FROM AUTHOR]

The Roquemaillère site on the southeastern margin of the French Massif Central is one of the rare localities along the Northern Gondwana margin from which Silurian odontopleurid trilobites have been recovered. Revision of M.-C. Chaubet's collections from this site, presented in her monograph (1937), together with additional new records revealed the presence of Kettneraspis Prantl & Přibyl, 1949 with 5 species [K. acanthifrons sp. nov., K. cf. juengeri Santel, 2001, K. rojanensis sp. nov., K. anteflexa sp. nov., K. aff. parkini (Siveter, 1989)], Eoleonaspis Sheng, 1974 with E. maeander sp. nov., Radiaspis Richter & Richter, 1917 with Radiaspis sp., Laethoprusia Ramsköld, 1991 with L. augur sp. nov., and Ceratocephalina Whittington, 1956 with C. angustifurcata sp. nov. Evidence from associated graptolites, brachiopods, bivalves and conodonts assigns the trilobites to the late Wenlock Homerian stage. The diverse fauna is dominated, both in specific diversity and number of individuals by Kettneraspis. The absence of the closely related Leonaspis regarded as characterising Gondwana-related terranes from the late Silurian onwards, confirms the pre-Ludlow age of the Roquemaillère fauna. [ABSTRACT FROM AUTHOR]

The Vinařice Limestone (Praha Formation; Central Bohemia) of Pragian age contains a moderate diverse lingulate brachiopod fauna including a new species of discinid, Acrosaccus robustus sp. nov., associated with several other poorly preserved discinids including the trematid Schizocrania, one species of the biernatid Havlicekion and fragments of an obolid. Lingulate brachiopods are associated with diverse rhynchonelliformean brachiopods mainly strophomenoids and rhynchonelloids. Brachiopods, trilobites and other fauna confirm the presence of a shallow, rough-water environment that existed before the origin of the coral-stromatoporoid-algal Koněprusy reef in the area. The lingulate brachiopod assemblage described herein differs from the local Emsian (Suchomasty Limestone) and Eifelian (Acanthopyge Limestones) lingulate brachiopod assemblages by absence of the discinid Chynithele. Presence of Schizocrania sp. indicates derivation of the fauna from the Lochkovian brachiopod assemblage. An Oichnustype drilling trace in the brephic shell is documented in the discinid Praeohlertella? sp. [ABSTRACT FROM AUTHOR]

The Cambrian (Jiangshanian, Sunwaptan) Honey Creek Formation in the Wichita Mountains region of Oklahoma yielded a new fauna dominated by Monocheilus Resser, 1937 (senior synonym of Stigmacephalus Resser, 1937) in association with Ptychaspis Hall, 1863. It occupies the same stratigraphic position as similar faunas in the Upper Mississippi Valley and Alberta, lying a little above an interval characterized by species of Taenicephalus Ulrich and Resser in Walcott, 1924 and Orygmaspis Resser, 1937. Revision of Ptychaspis bullasa Lochman and Hu, 1959 from type material from Idaho and sclerites attributed to the species from Texas reveals a plexus of pseudocryptic species that share tuberculate sculpture on the cranidium. New species are Monocheilus reginae, Monocheilus richardi, Ptychaspis occulta, and Ptychaspis matuszaki. UUID: www.zoobank.org/c2771c63-db4b-434a-ae58-3e3fda19ecb0 [ABSTRACT FROM AUTHOR]

The suborder Phacopina, characterized by schizochroal eyes, is among the most common groups of trilobites in Devonian strata. The marine sediments of the Famennian in western Junggar, Xinjiang, contain abundant low-disparity phacopids, which have previously been designated to Omegops accipitrinus mobilis, Phacops circumspectans tuberculosus, and Omegops cornelius on the basis of small numbers of poorly preserved specimens. In this study, these phacopids were identified as two new species of Omegops, O. honggulelengensis n. sp. and O. xiangi n. sp., on the basis of nearly 200 well-preserved specimens. The intraspecific variations of eye lenses of these specimens were quantitatively analyzed. On the basis of differences in the total number, number of dorsoventral files, and arrangement of the eye lenses, the absence of lenses in the middle part of the visual surface, and asymmetry of the number and/or arrangement of lenses in the two eyes, it was concluded that the reasons for intraspecific variation in eye lenses of Late Devonian Omegops from western Junggar were different from previously described factors but were likely genetic or embryological malfunctions or abnormalities caused by pathological conditions. Diversity of lenses in the schizochroal eyes shows that the number and arrangement of eye lenses was not stable in Phacopina. Therefore, many specimens are needed for quantitative study to determine the true characteristics of the number or arrangement of eye lenses when these features are used in the systematic taxonomy of Phacopina. UUID: http://zoobank.org/6bd14390-05fe-45ad-8eeb-3bf397a46a68 [ABSTRACT FROM AUTHOR]

Recent excavations at the site of Vermont's historically important Parker Quarry, long considered worked out where fossils were concerned, have yielded not only spectacular lower Cambrian trilobites but also soft‐bodied animals including the early chordate Emmonsaspis cambrensis and a new multi‐segmented bivalved arthropod Vermontcaris montcalmi. The first radiodont specimen from the locality indicates the presence of one of these apex predators more than 30‐cm long. New discoveries from this Burgess Shale‐type deposit add to our knowledge of the geographical diversity of animals that evolved during the Cambrian explosion. [ABSTRACT FROM AUTHOR]

Three-dimensional models reveal how the mechanics of exoskeletal enrolment changed during the development of a model organism for insights into ancient arthropod development, the 429-million-year-old trilobite Aulacopleura koninckii. Changes in the number, size and allocation of segments within the trunk, coupled with the need to maintain effective exoskeletal shielding of soft tissue during enrolment, necessitated a transition in enrolment style about the onset of mature growth. During an earlier growth phase, enrolment was sphaeroidal, with the venter of the trunk fitting exactly against that of the head. In later growth, if lateral exoskeletal encapsulation was to be maintained trunk length proportions did not permit such exact fitting, requiring an alternative, non-sphaeoridal enrolment style. Our study favours the adoption of a posture in later growth in which the posterior trunk extended beyond the front of the head. This change in enrolment accommodated a pattern of notable variation in the number of mature trunk segments, well known to characterize the development of this species. It suggests how an animal whose early segmental development was remarkably precisely controlled was able to realize the marked variation in mature segment number that was related, apparently, to life in a physically challenging, reduced oxygen setting. [ABSTRACT FROM AUTHOR]

The relative sizes of body segments are a major determinant of the shape and functionality of an animal. Developmental biases affecting this trait can therefore have major evolutionary implications. In vertebrates, a molecular activator/inhibitor mechanism, known as the inhibitory cascade (IC), produces a simple and predictable pattern of linear relative size along successive segments. The IC model is considered the default mode of vertebrate segment development and has produced long-term biases in the evolution of serially homologous structures such as teeth, vertebrae, limbs, and digits. Here we investigate whether the IC model or an IC-like model also has controls on segment size development in an ancient and hyperdiverse group of extinct arthropods, the trilobites. We examined segment size patterning in 128 trilobite species, and during ontogenetic growth in three trilobite species. Linear relative segment size patterning is prominent throughout the trunk of trilobites in the adult form, and there is strict regulation of this patterning in newly developing segments in the pygidium. Extending the analysis to select stem and modern arthropods suggests that the IC is a common default mode of segment development capable of producing long-term biases in morphological evolution across arthropods as it does in vertebrates. [ABSTRACT FROM AUTHOR]

Efficient extraction of oxygen from ambient waters played a critical role in the development of early arthropods. Maximizing gill surface area enhanced oxygen uptake ability but, with gills necessarily exposed to the external environment, also presented the issue of gill contamination. Here we document setae inserted on the dorsal surface of walking legs of the benthic-dwelling middle Cambrian Olenoides serratus and on the gill shaft of the Late Ordovician Triarthrus eatoni. Based on their physical positions relative to gill filaments, we interpret these setae to have been used to groom the gills, removing particles trapped among the filaments. The coordination between setae and gill filaments is comparable to that seen among modern crustaceans, which use a diverse set of setae-bearing appendages to penetrate between gill filaments when grooming. Grooming is known relatively early in trilobite evolutionary history and would have enhanced gill efficiency by maximizing the surface area for oxygen uptake. [ABSTRACT FROM AUTHOR]

Trilobites from the upper Guzhangian of the southern Argentine Precordillera, preliminarily described by Carlos Rusconi in the 1950s, are revised herein. The specimens studied were collected from an allochthonous limestone block of La Cruz Olistoliths at 200 m northwest of Estancia San Isidro locality (San Isidro area, Mendoza). Taxa comprise Kormagnostus seclusus (Walcott, 1884), Cedaria prolifica Walcott, 1924, C. puelchana Rusconi, 1954, Tricrepicephalus texanus (Shumard, 1861), Meteoraspis metra (Walcott, 1890), Coosia conicephala (Rusconi, 1954) new combination, Coosella texana? Resser, 1942, Nasocephalus cf. N. nasutus Wilson, 1954, and Olenoides proa (Rusconi, 1954) new combination. The North American genera Meteoraspis Resser, 1935 and Nasocephalus Wilson, 1954 are reported confidently from South America for the first time. This assemblage is representative of the Cedaria prolifica Zone, which correlates with the lower Crepicephalus Zone of the traditional North American genus-based zonation. Most of the genera and species identified were previously described exclusively from Canada, the United States, and northwestern Mexico, a fact that provides new support to an allochthonous Laurentian origin of the Argentine Precordillera. [ABSTRACT FROM AUTHOR]

The western Mongolian Lake Zone was a Neoproterozoic to early Paleozoic volcanic arc where tuffs, lavas, fossiliferous siliciclastics, and carbonates accumulated during the early Cambrian. An uppermost Cambrian Series 2 (upper Stage 4) trilobite assemblage is described here from the Burgasutay Formation representing a continuous lower Cambrian succession at the Seer Ridge of the Great Lake Depression. The new assemblage is dominated by dorypygids and consists of 13 trilobite genera belonging to nine families including Catinouyia heyunensis new species. These fossils comprise the youngest and richest lower Cambrian trilobite assemblage in Mongolia. The composition of the Lake Zone fauna suggests its biogeographic affinity with the Siberian Platform and Altay-Sayan Foldbelt, but the presence of inouyiids also implies a connection of this region with East Gondwana. UUID: http://zoobank.org/fb0ebe23-144f-46ed-9543-7df9eea85fbc [ABSTRACT FROM AUTHOR]

A siliciclastic succession is exposed at the Faraghan mountain, northern Persian Gulf, southeastern Iran. A detailed, high-resolution palynological analysis was performed on the Zardkuh, Seyahou, Dargaz, and Sarchahan formations to verify the exact age and palaeogeographic position of the High Zagros Mountains. Two hundred surface samples from this succession were collected and analysed. Most samples yielded abundant and well-preserved chitinozoans, acritarchs, scolecodonts, and cryptospores. Fifty-three chitinozoan species (21 genera) were identified that permitted to establish the Eremochitina brevis, Desmochitina ornensis, Belonechitina henryi, Siphonochitina formosa, Belonechitina robusta, Tanuchitina fistulosa, Acanthochitina barbata, Armoricochitina nigerica, Ancyrochitina merga, Tanuchitina elongata, Spinachitina oulebsiri, and Spinachitina fragilis biozones in ascending stratigraphic order as was previously established for the North Gondwana Domain. These results indicate that the Zagros Mountain Belt of Iran was part of the North Gondwana palaeo-province during the Ordovician-Silurian. On the other hand, these chitinozoan biozones and other associated fauna (e.g. graptolites, trilobites, brachiopods, and conodonts) suggest a late Early Ordovician (Floian) to Early Silurian (Rhuddanian) age range, with unconformities, for this succession. Based on chitinozoan biozones, a distinctive hiatus is present between the Zardkuh and Seyahou formations at Faraghan mountain, which corresponds to the absence of jenkinsi-tanvillensis chitinozoan biozones, encompassing the latest Middle Ordovician (latest Darriwilian: stage slice Dw3) and the early Late Ordovician (Sandbian: the stage slices Sa1 to Sa2 and time slices 5a to 5b). Two chitinozoan species were erected: Belonechitina bifurcaspina sp. nov., Angochitina persianense sp. nov., and Eremochitina cf. brevis was left in open nomenclature. Siliciclastic deposits of the Faraghan mountain yielded rich chitinozoan assemblages. Fifty-three identified chitinozoan species resulted in 12 chitinozoan biozones. Kerogenous black shales contain both the S. oulebsiri and N. persculptus biozones. A hiatus was identified, corresponding to the Dw3 and Sa1–Sa2 stage slices. Two new taxa: B. bifurcaspina and A. persianense, are proposed. [ABSTRACT FROM AUTHOR]

Trilobites were notably flexible in the moulting behaviours they employed, producing a variety of moult configurations preserved in the fossil record. Investigations seeking to explain this moulting variability and its potential impacts are few, despite abundant material being available for study. We present the first quantitative study on moulting in a single trilobite species using a dataset of almost 500 moult specimens of Estaingia bilobata from the Cambrian (Series 2, Stage 4) Emu Bay Shale, South Australia. Specimens were categorized by moulting mode (Salter's or Sutural Gape) and their associated configurations, and their body proportions measured from both a museum collection (including a bycatch sample) and a randomly‐collected field sample. This enabled analysis of the proportion of E. bilobata specimens displaying the Sutural Gape and Salter's modes of moulting and their different configurations, and tests for association between moulting behaviour and body proportions. The results show a wide range of E. bilobata moulting configurations in all samples, suggesting that configurations represent definable instances in a largely continuous spectrum of variation. Analyses comparing body proportions of specimens showing the two modes of moulting were non‐significant, suggesting there is no true association between moulting behaviour and body proportion, except for a single significant result for body length. All results were relatively consistent between the museum and field samples. However, removing accessioned specimens from the museum sample brought results even further in line with the field sample, supporting the need for consideration of museum collection bias in palaeontological analyses. [ABSTRACT FROM AUTHOR]

Malformed trilobite specimens present important insight into understanding how this extinct arthropod group recovered from developmental or moulting malfunctions, pathologies, and injuries. Previously documented examples of malformed trilobite specimens are often considered in isolation, with few studies reporting on multiple malformations in the same species. Here we report malformed specimens of the ellipsocephaloid trilobite Estaingia bilobata from the Emu Bay Shale Konservat-Lagerstätte (Cambrian Series 2, Stage 4) on Kangaroo Island, South Australia. Ten malformed specimens exhibiting injuries, pathologies, and a range of teratologies are documented. Furthermore, five examples of mangled exoskeletons are presented, indicative of predation on E. bilobata. Considering the position of malformed and normal specimens of E. bilobata in bivariate space, we demonstrate that the majority of malformed specimens cluster among the larger individuals. Such specimens may exemplify larger forms successfully escaping predation attempts, but could equally represent individuals exhibiting old injuries that were made during earlier (smaller) growth stages that have healed through subsequent moulting events. The available evidence from the Emu Bay Shale suggests that this small, extremely abundant trilobite likely played an important role in the structure of the local ecosystem, occupying a low trophic level and being preyed upon by multiple durophagous arthropods. Furthermore, the scarcity of malformed E. bilobata specimens demonstrates how rarely injuries, developmental malfunctions, and pathological infestations occurred within the species. [ABSTRACT FROM AUTHOR]

The Skyberg Biota is a new early Cambrian Konservat-Lagerstätte, documented from a 7.5-m-thick succession of the Skyberg Member, Ringstranda Formation, in the classical Mjosa area of Norway. It displays a high species diversity and contains: algae; sponges; brachiopods; hyoliths; bivalved arthropods; trilobites; palaeoscolecids and other vermiform organisms; weakly sclerotized fragments of unknown affinity; several tubicolous fossils; the enigmatic genus Lapworthella; and a number of additional problematica together with infrequent trace fossils consisting of burrows and faecal pellets. This novel macro-biota encloses the most diverse fossil assemblage known from the Cambrian Series 2 locally in the Mjosa area, and regionally in Baltoscandia, and currently includes around 50 species of 10 major animal groups and macro-algae. The Skyberg Biota contains taxa previously unknown from Norway, several are new to Baltoscandia and also includes a range of new species. The Skyberg biota offers a rare glimpse into the biodiversity of Baltoscandia just prior to the large faunal turnover at the late-middle Cambrian transition. [ABSTRACT FROM AUTHOR]

The advent of new and powerful mathematical methods allows us to carry out multidimensional analyses of traits. Regarding disparity the number of methods to measure morphological variation within a taxonomical group is vast and the choice of a single disparity index can limit the interpretation of the results. The use of two disparity indexes, the sum of ranges and the sum of variances by Hopkins (2022) enriched the work by Suárez & Esteve (2021). The interpretation of the results of any sort is based on the analysed data, in this case our ecomorphological dataset. We point out the importance of an accurate ecomorphological dataset, as taxonomic mistakes or ecological misinterpretations are unavoidable and continuous updating is therefore mandatory. The updated ecomorphological dataset, using appropriate indexes and resampling, provides new and exciting results which show us a new complex scenario in the evolution of trilobites throughout the Palaeozoic. [ABSTRACT FROM AUTHOR]

The new scutelluid trilobite genus Mitroplax, with type species M. enormis (Etheridge, 1894), occurs in Pragian to early Emsian strata at several localities in Victoria, Australia. The genus is characterized by a remarkably long and flat anterior cephalic border, a glabella that expands almost uniformly forward from the occipital furrow, a subcircular S2 discrete from S1, and a pygidium with the well-rounded paired pleural ribs and the posterior bifurcations of the postaxial rib tapering almost to a point distally. The type species grew to exceptional size, as indicated by the dimensions of the largest pygidia. Another scutelluid from the Lochkovian of Victoria, ‘Goldius’ greenii Chapman, 1914, is revised and assigned to Spiniscutellum Šnajdr, 1960. This species and a related one from the Lochkovian of the Bungonia district of south-eastern New South Wales are the first records of Spiniscutellum from eastern Gondwana. Spiniscutellum (Lochkovopeltis) Hörbinger, 2004 is regarded as a junior synonym of Spiniscutellum. [ABSTRACT FROM AUTHOR]