New taxa and phyletic evolution of the Aeronian (Llandovery, Silurian) Petalocrinidae (Echinodermata, Crinoidea) in Guizhou, South China Block

Abstract

Abstract.-Systematic paleontology of three new species of Petalocrinidae (Crinoidea) are documented from the carbonate-dominated units of the Shihniulan and equivalent Leijiatun formations (Llandovery, Silurian) of the Baisha, Fengxiang, and Shuibatang sections in Guizhou (China). New taxa are from the Upper Yangtze Epicontinental Sea of the South China Block. The new taxa include Petalocrinus stenopetalus new species, Spirocrinus circularis new species, and S. dextrosus new species. They have a narrow spatial and temporal (Aeronian) distribution. Evolutionary patterns of the four genera of Petalocrinidae are outlined based on the specialized characters of the fused arm plates. Phylogenetic analysis was used to assess morphological relationships within the Petalocrinidae. Petalocrinus inferior represents the plesiomorphic condition for the group and nests as a sister group of P. stenopetalus n. sp. and the Spirocrinus species used in this analysis and the clade exclusively comprised of Sinopetalocrinus. The phylogenetic analysis suggests that Petalocrinus, as currently defined, might be a paraphyletic genus.

Pure keratin membrane and fibers from chicken feather

“…3 shows the microstructure of prepared membrane and fiber. It can be seen that the surface and cross section of the membrane is uniform with a roughness on the micro level, which is different from the chitosan membrane prepared by the same method [36]. That is because the introduction of SDS uniformed the complex structure of keratin macromolecular chains, and makes them a cylinder shape with large amount of negative charge, which leads to the strong electrostatic repulsion.…”

Fusion or hypertrophy?: the unusual arms of the Petalocrinidae (Ordovician-Devonian: Crinoidea)

“…Three petalocrinid second brachial plates were embedded in bioplastic, and thin sections were prepared along the long axis of the arm plate. Specimens studied include Petalocrinus inferior Bather, 1898, Leijiatun Formation (Aeronian), Baisha Section, South China Block, China; Petalocrinus stenopetalus Mao et al, 2017, Leijiatun Formation (Aeronian), Fengxiang Section, South China Block, China; and Spirocrinus circularis Mao et al, 2017, Shihniulan Formation (Aeronian), Shuibatang Section, South China Block, China (Fig. 2; see Mao et al, 2017 for stratigraphic and biogeographic details).…”

“…Eopetalocrinus Li, 1993 is the oldest crinoid with this unique arm morphology, and it originated during the Ordovician (Darriwilian; Dawan Formation) on the South China Block. During the early Silurian (Llandovery, Aeronian), the Petalocrinidae diversified, yielding three genera: Petalocrinus Weller and Davidson, 1896; Sinopetalocrinus Mu and Lin, 1987; and Spirocrinus Mu and Wu, 1974 (Mao et al, 2015, 2017). Petalocrinus has ambulacra confined to the oral side of the second brachial plate (Fig.…”

“…Petalocrinus has ambulacra confined to the oral side of the second brachial plate (Fig. 1.1, 1.3), and ambulacra grow over the edges of the second brachial in Sinopetalocrinus so that ambulacra are present on both the oral and aboral side of this arm plate (Mao et al, 2017, fig. 4).…”

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Figure 1.Oral view of petalocrinid second brachial plates. ( 1 ) Petalocrinus inferior Bather, 1898; OSU 54648; ( 2 ) Spirocrinus circularis Mao et al, 2017; OSU 54650; ( 3 ) Petalocrinus stenopetalus Mao et al, 2017; OSU 64649. Scale bar 5.0 mm.

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