The largest arthropod in Earth history: insights from newly discovered Arthropleura remains (Serpukhovian Stainmore Formation, Northumberland, England)

Arthropleura is a genus of giant myriapods that ranged from the early Carboniferous to Early Permian, with some individuals attaining lengths >2 m. Although most of the known fossils of the genus are disarticulated and occur primarily in late Carboniferous (Pennsylvanian) strata, we report here partially articulated Arthropleura remains from the early Carboniferous Stainmore Formation (Serpukhovian; Pendleian) in the Northumberland Basin of northern England. This 76 × 36 cm specimen represents part of an exuvium and is notable because only two comparably articulated giant Arthropleura fossils are previously known. It represents one of the largest known arthropod fossils and the largest arthropleurid recovered to date, the earliest (Mississippian) body fossil evidence for gigantism in Arthropleura, and the first instance of a giant arthropleurid body fossil within the same regional sedimentary succession as the large arthropod trackway Diplichnites cuithensis. The remains represent 12–14 anterior Arthropleura tergites in the form of a partially sand-filled dorsal exoskeleton. The original organism is estimated to have been 55 cm in width and up to 2.63 m in length, weighing c. 50 kg. The specimen is preserved partially in three dimensions within fine sandstone and has been moderately deformed by synsedimentary tectonics. Despite imperfect preservation, the specimen corroborates the hypothesis that Arthropleura had a tough, sclerotized exoskeleton. Sedimentological evidence for a lower delta plain depositional environment supports the contention that Arthropleura preferentially occupied open woody habitats, rather than swampy environments, and that it shared such habitats with tetrapods. When viewed in the context of all the other global evidence for Arthropleura, the specimen contributes to a dataset that shows the genus had an equatorially restricted palaeogeographical range, achieved gigantism prior to late Paleozoic peaks in atmospheric oxygen, and was relatively unaffected by climatic events in the late Carboniferous, prior to its extinction in the early Permian.Supplementary material: Images of 3D mesh model of Arthropleura are available at https://doi.org/10.6084/m9.figshare.c.5715450

Late Ediacaran occurrences of the organic-walled microfossils Granomarginata and flask-shaped Lagoenaforma collaris gen. et sp. nov.

New occurrences of flask-shaped and envelope-bearing microfossils, including the predominantly Cambrian taxon Granomarginata, are reported from new localities, as well as from earlier in time (Ediacaran) than previously known. The stratigraphic range of Granomarginata extends into the Cambrian System, where it had a cosmopolitan distribution. This newly reported Ediacaran record includes areas from Norway (Baltica), Newfoundland (Avalonia) and Namibia (adjacent to the Kalahari Craton), and puts the oldest global occurrence of Granomarginata in the Indreelva Member (< 563 Ma) of the Stáhpogieddi Formation on the Digermulen Peninsula, Arctic Norway. Although Granomarginata is rare within the assemblage, these new occurrences together with previously reported occurrences from India and Poland, suggest a potentially widespread palaeogeographic distribution of Granomarginata through the middle–late Ediacaran interval. A new flask-shaped microfossil Lagoenaforma collaris gen. et sp. nov. is also reported in horizons containing Granomarginata from the Stáhpogieddi Formation in Norway and the Dabis Formation in Namibia, and flask-shaped fossils are also found in the Gibbett Hill Formation in Newfoundland. The Granomarginata–Lagoenaforma association, in addition to a low-diversity organic-walled microfossil assemblage, occurs in the strata postdating the Shuram carbon isotope excursion, and may eventually be of use in terminal Ediacaran biostratigraphy. These older occurrences of Granomarginata add to a growing record of body fossil taxa spanning the Ediacaran–Cambrian boundary.

The largest theropod track site in Yunnan, China: a footprint assemblage from the Lower Jurassic Fengjiahe Formation

Yunnan Province is famous for its diversified Lufeng vertebrate faunas containing many saurischian dinosaur remains. In addition to the body fossil record, dinosaur ichnofossils have also been discovered in Yunnan, and the number of published track sites is on the rise. We report a theropod assemblage from the Lower Jurassic Fengjiahe Formation in Xiyang, central Yunnan. It is the third report and description of dinosaur footprints from the Fengjiahe Formation, and this new track site is the largest in number of footprints for theropods in Yunnan. Over one hundred footprints are preserved on different layers of a claystone-dominated succession close to the Lower-Middle Jurassic boundary. The track area is referred to as a lacustrine shallow-water paleoenvironment. Tracks vary in size, morphology, and preservation. All are tridactyl and digitigrade, and some are identified as undertracks. The best preserved footprints were divided into three morphotypes: morphotype A (>8 cm–<21 cm) resembling Grallator; morphotype B (>27 cm–<30 cm) identified as Kayentapus xiaohebaensis; and morphotype C, an isolated footprint (39 cm) referred to the ichnogenus Kayentapus. Although footprint shape is influenced by many factors, biotic or abiotic, morphological differences among tracks such as size, divarication angles and proportions imply that at least three different kinds of theropods were visiting this site frequently. Theropod body fossils found in the surrounding area, such as Sinosaurus, turn out to be similar in body size to the projected size estimated from footprint lengths at the track site. In Yunnan, discoveries of theropod body fossils are rare. In that respect, the track record is a useful diversity indicator which can help to encompass theropod diversity patterns. Broadly speaking, large predators (five meters long or more) were uncommon in Early Jurassic ecosystems. Accordingly, large tracks are scarce on the track site, but not absent. Trackmakers of all sizes presumably coexisted in this tropical Jurassic ecosystem, and were regularly drawn to the track site in search of water or food resources.

Late Ediacaran organic microfossils from Finland

Here we present a detailed accounting of organic microfossils from late Ediacaran sediments of Finland, from the island of Hailuoto (northwest Finnish coast), and the Saarijärvi meteorite impact structure (~170 km northeast of Hailuoto, mainland Finland). Fossils were recovered from fine-grained thermally immature mudstones and siltstones and are preserved in exquisite detail. The majority of recovered forms are sourced from filamentous prokaryotic and protistan-grade organisms forming interwoven microbial mats. Flattened Nostoc-ball-like masses of bundled Siphonophycus filaments are abundant, alongside Rugosoopsis and Palaeolyngbya of probable cyanobacterial origin. Acritarchs include Chuaria, Leiosphaeridia, Symplassosphaeridium and Synsphaeridium. Significantly, rare spine-shaped sclerites of bilaterian origin were recovered, providing new evidence for a nascent bilaterian fauna in the terminal Ediacaran. These findings offer a direct body-fossil insight into Ediacaran mat-forming microbial communities, and demonstrate that alongside trace fossils, detection of a bilaterian fauna prior to the Cambrian might also be sought among the emerging record of small carbonaceous fossils (SCFs).

Phyllozoon and Aulozoon: key components of a novel Ediacaran death assemblage in Bathtub Gorge, Heysen Range, South Australia

The recognition of fossiliferous horizons both below and above the classical Ediacara levels of the Flinders Ranges, South Australia, significantly expands the potential of this candidate World Heritage succession. Here we document a small window into the biology and taphonomy of the late Ediacaran seafloor within the new Nilpena Sandstone Member of the Rawnsley Quartzite in Bathtub Gorge, northern Heysen Range. A 1 m2 slab extracted from the gorge, now on permanent display at the South Australian Museum, has a death assemblage dominated by the erniettomorph Phyllozoon hanseni Jenkins and Gehling 1978 and a newly named macroscopic tubular body fossil – Aulozoon soliorum gen. et sp. nov. – on its fine sandstone bed sole. The orientations and juxtaposition of these taxa suggest overprinting of an in situ benthic Phyllozoon community by sand-filled tubes of Aulozoon carried in by a storm wave-base surge. Phyllozoon hanseni is a widespread species that is restricted to the Nilpena Sandstone Member of the Rawnsley Quartzite, whereas Dickinsonia costata ranges from the underlying Ediacara Sandstone Member into the Nilpena Sandstone Member. Fundamental differences in the ways these two vendobiont taxa are constructed and preserved may provide insights into their biology and phylogenetic affinities. In the Nilpena Sandstone Member, D. costata is joined by Dickinsonia rex Jenkins 1992, which appears to be confined to the member, and is here re-described to clarify its taxonomic status and stratigraphic distribution.

Possible poriferan body fossils in early Neoproterozoic microbial reefs

Molecular phylogeny indicates that metazoans (animals) emerged early in the Neoproterozoic era1, but physical evidence is lacking. The search for animal fossils from the Proterozoic eon is hampered by uncertainty about what physical characteristics to expect. Sponges are the most basic known animal type2,3; it is possible that body fossils of hitherto-undiscovered Proterozoic metazoans might resemble aspect(s) of Phanerozoic fossil sponges. Vermiform microstructure4,5, a complex petrographic feature in Phanerozoic reefal and microbial carbonates, is now known to be the body fossil of nonspicular keratosan demosponges6–10. This Article presents petrographically identical vermiform microstructure from approximately 890-million-year-old reefs. The millimetric-to-centimetric vermiform-microstructured organism lived only on, in and immediately beside reefs built by calcifying cyanobacteria (photosynthesizers), and occupied microniches in which these calcimicrobes could not live. If vermiform microstructure is in fact the fossilized tissue of keratose sponges, the material described here would represent the oldest body-fossil evidence of animals known to date, and would provide the first physical evidence that animals emerged before the Neoproterozoic oxygenation event and survived through the glacial episodes of the Cryogenian period.

A diverse Late Cretaceous vertebrate tracksite from the Winton Formation of Queensland, Australia

The Upper Cretaceous ‘upper’ Winton Formation of Queensland, Australia is world famous for hosting Dinosaur Stampede National Monument at Lark Quarry Conservation Park, a somewhat controversial tracksite that preserves thousands of tridactyl dinosaur tracks attributed to ornithopods and theropods. Herein, we describe the Snake Creek Tracksite, a new vertebrate ichnoassemblage from the ‘upper’ Winton Formation, originally situated on Karoola Station but now relocated to the Australian Age of Dinosaurs Museum of Natural History. This site preserves the first sauropod tracks reported from eastern Australia, a small number of theropod and ornithopod tracks, the first fossilised crocodyliform and ?turtle tracks reported from Australia, and possible lungfish and actinopterygian feeding traces. The sauropod trackways are wide-gauge, with manus tracks bearing an ungual impression on digit I, and anteriorly tapered pes tracks with straight or concave forward posterior margins. These tracks support the hypothesis that at least one sauropod taxon from the ‘upper’ Winton Formation retained a pollex claw (previously hypothesised for Diamantinasaurus matildae based on body fossils). Many of the crocodyliform trackways indicate underwater walking. The Snake Creek Tracksite reconciles the sauropod-, crocodyliform-, turtle-, and lungfish-dominated body fossil record of the ‘upper’ Winton Formation with its heretofore ornithopod- and theropod-dominated ichnofossil record.

Extensive vertebrate tracksite from the Upper Red Formation (middle–late Miocene), west Zanjan, northwestern Iran

An extensive vertebrate tracksite from the middle–late Miocene Upper Red Formation in western Zanjan Province, northwestern Iran, provides new records of paleobiogeographical significance. These are records of common footprints of felids referred to as Felipeda lynxi Panin and Avram, canids referred to as Canipeda longigriffa Panin and Avram and less common bird footprints referred to as Iranipeda abeli Lambrecht. The Canipeda record establishes the late Miocene presence of canids on the Iranian Plateau as part of the Eurasia-wide “Eucyon event”. The Felipeda footprints are consistent with body fossil and footprint records elsewhere in Eurasia that indicate a widespread distribution of felids by late Miocene time. An unusual trace associated with the footprints is a large, shallow grazing or locomotion trace similar to Megaplanolites in some features but distinctive in various features and its occurrence in nonmarine facies, and it will be the subject of further study.

Were all trilobites fully marine? Trilobite expansion into brackish water during the early Palaeozoic

Trilobites, key components of early Palaeozoic communities, are considered to have been invariably fully marine. Through the integration of ichnological, palaeobiological, and sedimentological datasets within a sequence-stratigraphical framework, we challenge this assumption. Here, we report uncontroversial trace and body fossil evidence of their presence in brackish-water settings. Our approach allows tracking of some trilobite groups foraying into tide-dominated estuaries. These trilobites were tolerant to salinity stress and able to make use of the ecological advantages offered by marginal-marine environments migrating up-estuary, following salt wedges either reflecting amphidromy or as euryhaline marine wanderers. Our data indicate two attempts of landward exploration via brackish water: phase 1 in which the outer portion of estuaries were colonized by olenids (Furongian–early late Tremadocian) and phase 2 involving exploration of the inner to middle estuarine zones by asaphids (Dapingian–Darriwilian). This study indicates that tolerance to salinity stress arose independently among different trilobite groups.

Pleistocene golden mole and sand-swimming trace fossils from the Cape coast of South Africa

More than 250 Pleistocene vertebrate trace fossil sites have been identified on the Cape south coast of South Africa in aeolianites and cemented foreshore deposits. These discoveries, representing the epifaunal tracks of animals that moved over these sand substrates, complement traditional body fossil studies, and contribute to palaeo-environmental reconstruction. Not described in detail until now, but also important faunal components, are the infaunal traces of animals that moved within these sandy substrates. Six golden mole burrow trace sites (Family Chrysochloridae) have been identified on the Cape south coast. In addition, three sites, including one on the Cape southeast coast, have been identified that show evidence of sand-swimming, probably by a golden mole with a means of locomotion similar to that of the extant Eremitalpa genus. Such traces have not been described in detail in the global ichnology record, and merit the erection of a new ichnogenus Natatorichnus, with two ichnospecies, N. subarenosa ichnosp. nov and N. sulcatus ichnosp. nov. Care is required in the identification of such traces, and the orientation of the trace fossil surface needs to be determined, to avoid confusion with hatchling turtle tracks. Substantial regional Pleistocene dune environments are inferred from these sand-swimming traces.