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Browsing by Author "Muscente, A. D."

Now showing 1 - 5 of 5
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    Armored kinorhynch-like scalidophoran animals from the early Cambrian.
    Zhang, H.; Xiao, S.; Liu, Y.; Yuan, X.; Wan, B.; Muscente, A. D.; Shao, T.; Gong, H.; Cao, G. (2015-11-26)
    Morphology-based phylogenetic analyses support the monophyly of the Scalidophora (Kinorhyncha, Loricifera, Priapulida) and Nematoida (Nematoda, Nematomorpha), together constituting the monophyletic Cycloneuralia that is the sister group of the Panarthropoda. Kinorhynchs are unique among living cycloneuralians in having a segmented body with repeated cuticular plates, longitudinal muscles, dorsoventral muscles, and ganglia. Molecular clock estimates suggest that kinorhynchs may have diverged in the Ediacaran Period. Remarkably, no kinorhynch fossils have been discovered, in sharp contrast to priapulids and loriciferans that are represented by numerous Cambrian fossils. Here we describe several early Cambrian (~535 million years old) kinorhynch-like fossils, including the new species Eokinorhynchus rarus and two unnamed but related forms. E. rarus has characteristic scalidophoran features, including an introvert with pentaradially arranged hollow scalids. Its trunk bears at least 20 annuli each consisting of numerous small rectangular plates, and is armored with five pairs of large and bilaterally placed sclerites. Its trunk annuli are reminiscent of the epidermis segments of kinorhynchs. A phylogenetic analysis resolves E. rarus as a stem-group kinorhynch. Thus, the fossil record confirms that all three scalidophoran phyla diverged no later than the Cambrian Period.
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    Exceptionally preserved fossil assemblages through geologic time and space
    Muscente, A. D.; Schiffbauer, J. D.; Broce, J.; Laflamme, M.; O'Donnell, K.; Boag, T. H.; Meyer, M.; Hawkins, A. D.; Huntley, J. W.; McNamara, M.; MacKenzie, L. A.; Stanley, G. D.; Hinman, N. W.; Hofmann, M. H.; Xiao, S. (2017-08)
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    Spiculogenesis and biomineralization in early sponge animals
    Tang, Qing; Wan, Bin; Yuan, Xunlai; Muscente, A. D.; Xiao, Shuhai (Springer Nature, 2019-07-26)
    Most sponges have biomineralized spicules. Molecular clocks indicate sponge classes diverged in the Cryogenian, but the oldest spicules are Cambrian in age. Therefore, sponges either evolved spiculogenesis long after their divergences or Precambrian spicules were not amenable to fossilization. The former hypothesis predicts independent origins of spicules among sponge classes and presence of transitional forms with weakly biomineralized spicules, but this prediction has not been tested using paleontological data. Here, we report an early Cambrian sponge that, like several other early Paleozoic sponges, had weakly biomineralized and hexactine-based siliceous spicules with large axial filaments and high organic proportions. This material, along with Ediacaran microfossils containing putative non-biomineralized axial filaments, suggests that Precambrian sponges may have had weakly biomineralized spicules or lacked them altogether, hence their poor record. This work provides a new search image for Precambrian sponge fossils, which are critical to resolving the origin of sponge spiculogenesis and biomineralization.
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    Systematic paleontology, acritarch biostratigraphy, and delta C-13 chemostratigraphy of the early Ediacaran Krol A Formation, Lesser Himalaya, northern India
    Xiao, Shuhai; Jiang, Ganqing; Ye, Qin; Ouyang, Qing; Banerjee, Dhiraj M.; Singh, Birendra P.; Muscente, A. D.; Zhou, Chuanming; Hughes, Nigel C. (Cambridge University Press, 2022)
    Acritarch biostratigraphic and delta C-13 chemostratigraphic data from the Krol A Formation in the Solan area (Lesser Himalaya, northern India) are integrated to aid inter-basinal correlation of early-middle Ediacaran strata. We identified a prominent negative delta C-13 excursion (likely equivalent to EN2 in the lower Doushantuo Formation in the Yangtze Gorges area of South China), over a dozen species of acanthomorphs (including two new species-Cavaspina tiwariae Xiao n. sp., Dictyotidium grazhdankinii Xiao n. sp.), and numerous other microfossils from an interval in the Krol A Formation. Most microfossil taxa from the Krol A and the underlying Infra-Krol formations are also present in the Doushantuo Formation. Infra-Krol acanthomorphs support a correlation with the earliest Doushantuo biozone: the Appendisphaera grandis-Weissiella grandistella-Tianzhushania spinosa Assemblage Zone. Krol A microfossils indicate a correlation with the second or (more likely, when delta C-13 data are considered) the third biozone in the lower Doushantuo Formation (i.e., the Tanarium tuberosum-Schizofusa zangwenlongii or Tanarium conoideum-Cavaspina basiconica Assemblage Zone). The association of acanthomorphs with EN2 in the Krol Formation fills a critical gap in South China where chert nodules, and thus acanthomorphs, are rare in the EN2 interval. Like many other Ediacaran acanthomorphs assemblages, Krol A and Doushantuo acanthomorphs are distributed in low paleolatitudes, and they may represent a distinct paleobiogeographic province in east Gondwana. The Indian data affirm the stratigraphic significance of acanthomorphs and delta C-13, clarify key issues of lower Ediacaran bio- and chemostratigraphic correlation, and strengthen the basis for the study of Ediacaran eukaryote evolution and paleobiogeography. UUID: http://zoobank.org/5289fdb2-0e49-4b3b-880f-f5b21acab371.
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    Taphonomy And Biological Affinity Of Three-Dimensionally Phosphatized Bromalites From The Middle Ordovician Winneshiek Lagerstätte, Northeastern Iowa, USA
    Hawkins, Andrew D.; Liu, Huaibao P.; Briggs, Derek E. G.; Muscente, A. D.; McKay, Robert M.; Witzke, Brian J.; Xiao, Shuhai (2018-01-09)
    The Winneshiek Lagerst¨atte occurs within an Ordovician meteorite impact structure beneath part of the city of Decorah, Iowa. The Lagerst¨atte has yielded an atypical marine fauna including phyllocarid crustaceans, eurypterids, conodonts, linguloid brachiopods, and jawless fish. Associated with these taxa are vermiform fossils: elongate, morphologically variable, and often three-dimensionally preserved bromalites of uncertain organisms. The preservational state of these bromalites is significantly different from that of other components of the Winneshiek biota. Here we present a compositional and microstructural analysis of the vermiform fossils in order to elucidate their taphonomy and biological affinities. The majority of studied specimens are preserved three-dimensionally and composed of calcium phosphate, while a minority are preserved as carbonaceous compressions. Winneshiek bromalites exhibit important similarities to examples documented from both older and younger sediments. They provide independent evidence of predation in the Winneshiek assemblage during the Great Ordovician Biodiversification Event.