146 research outputs found
Cambrian ecological complexities: Perspectives from the earliest brachiopod – supported benthic communities in the early Cambrian Guanshan Lagerstätte
No full textThe Cambrian radiation is characterized by the emergence of diverse bilaterian animal phyla and theestablishment of complex marine ecosystems. The Guanshan Biota records an unusual ecological transition from trilobite- to brachiopod-dominated communities during Cambrian Stage 4. This community transition is accompanied by direct evidence of in situ biological interactions such as durophagous pre-dation and kleptoparasitism. Here we describe new material from the Guanshan biota, focusing on an association of palaeoscolecidomorphs and brachiopods with parasitic tube worms that occur on micro-bedding planes. The bedding plane assemblages are dominated by the organophosphatic brachiopod Neobolus wulongqingensis encrusted with kleptoparasitic tube-dwelling worms, along with infaunal palaeoscolecidans. Taphonomic and sedimentological evidence indicates that these specimens are com-monly preserved in life position, and thus the association between individuals represent potential biological interactions. This case study reveals that ecosystems during the early Cambrian exhibited a well-developed system of tiering and a complex trophic network, easily distinguished from the simple communities typical of precursor deposits in the Ediacaran. Brachiopods forming extremely dense concentrations on the sea floor are effectively acting as ecosystem engineers, not only to stabilize the soft-substrate seafloor, but also act as an alternative substrate for the oldest empirically demonstrated kleptoparasites.The in situ biological interactions preserved in the Guanshan Biota are critical for filling gaps in ourknowledge of ecosystem complexity in the Cambrian.This work was financially supported by the National Natural Science Foundation of China (NSFC Nos. 41720104002, 41890844, 41621003 to Zhang Zhifei and 4207020712, 42072003 to Timothy P. Topper), Strategic Priority Research Program of Chinese Academy of Sciences award to the Early Life Institute (grant XDB26000000), 111 Project of Ministry of Education of China (D17013), 1000 Talents Program (41720104002 to Timothy P. Topper and Luke C. Strotz) and Opening Foundation of State Key Laboratory of Continental Dynamics, Northwest University (21LCD02 to Chen Feiyang). </p
Topper et al. Raw coordinates used in ventral valve analyses
No full textRaw landmark coordinates used in ventral valve analyses exported directly from MorphoJ. This data has not been transformed using Generalized Procrustes Analysis
Topper et al. Raw coordinates for dorsal valves
No full textRaw landmark coordinates used in dorsal valve analyses exported directly from MorphoJ. This data has not been transformed using Generalized Procrustes Analysis
The oldest brachiopods from the lower Cambrian of South Australia
Get PDFThe morphology and organophosphatic shell structure of the paterinate brachiopod Askepasma is documented using new and previously collected specimens from the lower Cambrian of South Australia. Lack of adequately preserved material has seen the majority of paterinate specimens previously reported from South Australia referred to the genus Askepasma and treated under open nomenclature. Large collections of paterinates from the lower Cambrian Wilkawillina, Ajax, and Wirrapowie limestones in the Arrowie Basin, South Australia have prompted redescription of the type species Askepasma toddense and the erection of a new species, Askepasma saproconcha sp. nov. Askepasma saproconcha sp. nov. currently represents the oldest known brachiopod from the lower Cambrian successions in South Australia with a FAD in pre-trilobitic (Terreneuvian, Cambrian Stage 2, lower Atdabanian) strata in the basal part of the Wilkawillina and Wirrapowie limestones. Askepasma toddense predominantly occurs in Abadiella huoi Zone equivalent strata (Unnamed Cambrian Series 2, Stage 3, middle-upper Atdabanian) in the upper part of the lower Wilkawillina, Wirrapowie and Ajax limestones. The shell microstructure of Askepasma suggests a proximal stem group position within the Brachiopoda and similarities with tommotiid taxa provides further evidence that the ancestry of crown group brachiopods is firmly entrenched within the Tommotiida
A new name for a classic Cambrian Swedish brachiopod, Tallatella undosa (Moberg)
No full textThe brachiopod originally described as Kuturgina undosa Moberg, 1892 from the early Cambrian (Cambrian Series 2, Stage 4) När Shale of Kalmarsund, Sweden, has experienced a long and turbulent history since the original description over 100 years ago. Uncertainties regarding key morphological characters have resulted in the species taxonomically hopping between genera until it wasrecently assigned to the poorly known genus Cryptotreta Pelman, 1977 and subsequently transferred to the problematic paterinate family Cryptotretidae. Despite members of this group representing the oldest brachiopods in the fossil record, they remain enigmatic, both taxonomically and phylogenetically. Theidentification of the brachiopod species from the När Shale as a cryptotretid means that this brachiopod was the first member of the family to be discovered, yet its systematic position is far from certain. Examination of type material in addition to supplementary material acquired from the Skäggenäs Peninsula, Sweden, has elucidated many of the previous ambiguous morphological characteristics of the species. The new morphological information acquired here has resulted in the erection of a new paterinate genus, Tallatella gen. nov., to accommodate the Swedish material previously described as Cryptotreta undosa.Origin and early evolution of major animal clades in the Cambrian Perio
Moulting in the lobopodian Onychodictyon from the lower Cambrian of Greenland
No full textA number of lobopodian taxa from the Cambrian display pairs of sclerotized plates symmetrically positioned along the dorsum of the animal, predominantly above the walking appendages. Most genera were described from complete body fossils exquisitely preserved in the famous Cambrian Lagerstätten, but lobopodian phosphatized plates are found worldwide as typical components of Cambrian small shelly fossil assemblages (SSF). Details regarding intraspecific and ontogenetic variation in lobopod plates are elusive, and the lack of details of ornamentation in Lagerstätte specimens does not minimize the problem. We document here an assemblage of well-preserved isolated plates of Onychodictyon sp. from the Lower Cambrian (Cambrian Series 2, Stage 4) of North Greenland. Two specimens exhibit perfectly conjoined plates from successive moults. Details of ornamentation and the outline and profile of the fixed plates are identical, but width and length of the underlying plate are 24% larger. These specimens boost the body of evidence that lobopodians moulted but also show that plate outline and ornamentation did not vary during ontogeny.This work has been supported by the Carlsberg Foundation (TPT) and Swedish Research Council (JSP)Origin and early evolution of major animal clades in the Cambrian Perio
Keeping a lid on it: muscle scars and the mystery of the Mobergellidae [Elektronisk resurs]
No full textMobergellans were one of the first Cambrian skeletal groups to be recognized yet have long remained one of the mostproblematic in terms of biological function and affinity. Characterized by a disc-shaped, phosphatic sclerite, the mostdistinctive character of the group is a prominent set of internal scars, interpreted as representing sites of former muscleattachment. Predominantly based on muscle scar distribution, mobergellans have been compared to brachiopods,bivalves and monoplacophorans; however, a recurring theory that the sclerites acted as an operculum remains untested.Rather than correlate the number of muscle scars between taxa, here we focus on the percentage of the inner surfaceshell area that the scars constitute. We investigate two mobergellan species, Mobergella holsti and Discinella micans,and compare the Cambrian taxa with the muscle scars of a variety of extant and fossil marine invertebrate taxa to testwhether the mobergellan muscle attachment area is compatible with an interpretation as operculum. The only skeletalelements in our study with a comparable muscle attachment percentage are gastropod opercula. Complemented withadditional morphological information, our analysis supports the theory that mobergellan sclerites acted as an operculumpresumably from a tube-living organism. The paucity of tubes co-occurring with mobergellan sclerites could beexplained by the transportation and sorting of detached opercula, while the corresponding tube remained attached tosubstrata in shallower water. The operculum perhaps performed a similar role to that seen in serpulid annelids and inneritid gastropods sealing the living chamber of the organism to avoid desiccation or for protection.</p
Global Fatigue Life Modelling of Steel Half-pipes Bolted Connections
No full textAbstractA steel hybrid structural solution for onshore wind turbine towers was proposed in the European project SHOWTIME. This solution is used in the lattice structure for the lower portion of the tower. Recently, a procedure for fatigue life estimation of steel half-pipes bolted connections applied in global structural models using multiaxial Smith-Watson-Topper (SWT) criteria was proposed by Öztürk et al. In this paper a procedure for design S-N curve modelling of steel half-pipes bolted connections is proposed. This procedure is based on a local approach using multiaxial fatigue criteria together with an elastoplastic analysis using the finite element method. The materials to be used in this analysis are the S355 and S690 steels. This evaluation to be performed is calibrated with experimental results of fatigue tests of the connection under consideration
Deep origin of the crossed‐lamellar microstructure in early Cambrian molluscs
No full textAragonitic crossed-lamellar (CL) is one of themost commonly formed and extensively studied molluscanshell microstructures, yet its origin and early evolution within the Mollusca remains poorly understood. Here, a primitive CL microstructure from one of the oldest gastropods,Pela-giella madianensis, and the problematic hyolith Cupitheca sp. of the Cambrian Series 2 Xinji Formation on the North China Platform, was investigated. In P. madianensis, detailed characterization has revealed a typical four-ordered hierarchical orga-nization of aragonitic crystallites, and a thick layer of organic membranes surrounding its first-order lamellae. A transitional fibrous microstructure was observed between the outer CL and inner foliated aragonite structural layers. In Cupitheca sp.,only the first and second-order lamellae were visible due to preservation limitations, and the first-order lamellae were extremely irregular in shape and size, which is consistent with modern representatives. This study demonstrates that the capability to construct highly-mineralized intricate shells was acquired in early Cambrian stem-group gastropods. The CL microstructure first emerged in the early Cambrian and as a basal synapomorphic trait in total-group molluscs. Moreover, presence of the CL microstructure in problematic lophotrochozoans (i.e.hyoliths) is confirmed. This study contributes to a more complete picture of the evolutionary origin andarchitectural diversity of biomineralized mollusc shells during the Cambrian explosion, and strengthens the phylogenetic links between hyoliths and molluscs.This research was funded by the National Natural Science Foundation of China (Grant nos. 41930319, 41890845, 42102012, 41621003 and 42072003); Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB26000000), 111 Project (Grant No. D17013), Swedish Research Council (Grant nos. VR2016-04610 and VR2017-05183) a Young Thousand Talents Plan of China (Grant No. 41720104002) and China Postdoctoral Science Foundation (Grant No. 2022M712987). </p
The dawn of a dynasty: life strategies of Cambrian and Ordovician brachiopods
Get PDFBrachiopods are among the first animal phyla to emerge from the Cambrian Explosion, rapidly diversifying to all major palaeocontinental blocks within 20 million years. The group underwent another steep rise in diversity during the Ordovician, and their relative abundance and diversity made them one of the most successful invertebrate groups during the entire Palaeozoic. During this time, brachiopods lived in a range of environments and represented a significant component of marine ecosystems, yet information regarding their modes of life and ecology is somewhat limited. Recent studies, primarily from the Chengjiang and Burgess Shale Lagerstätten, have revealed that by the Middle Cambrian (Series 3, Stage 5) brachiopods from across the phylum had already developed a range of ecological strategies and life modes. Cambrian brachiopods occupied distinct trophic niches on soft and hard substrates and exhibited at least five types of lifestyles: pedicle attachment, pedicle anchoring, cemented, free‐lying and semi‐infaunal. Comparisons with Ordovician benthic assemblages show that despite the explosion of brachiopod taxa witnessed in the Ordovician, with the exception of the appearance of burrowing brachiopods, life strategies of brachiopods remained largely the same. Indicating that the majority of life modes observed in brachiopods had rapidly evolved and was already in place prior to the Great Ordovician Biodiversity Event.Funding via a Marie Curie COFUND Research Fellowship (Durham University) is acknowledged (Topper); Harper thanks the Leverhulme Trust for a research fellowship and the Wenner‐Gren Foundation for support.Peer reviewe
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