Crinoid specimens with cups were found in two dark greenish gray, lenticular laminated shale slabs which are considered to have been derived from the Middle Ordovician Jigunsan Formation, South Korea.The slabs were collected near the outcrops of the formation and contain disarticulated sclerites of trilobites typical of the formation such as Dolerobasilicus.Most crinoid specimens have cup, arm and column preserved as external molds.Taxonomic study in progress indicates that one specimen belongs to the Diplobathrida of the Camerata and the remaining specimens which all occur in a single slab to the Disparida.The diplobathrid specimen is characterized by a large-sized, subglobular cup with strong stellate median ray ridges, pentagonal structure at the cup base, uniserial and pinnulate arms, and circular stem with circular lumen.These morphological features are similar to those of Pararchaeocrinus or Trochocrinites（the family Rhodocrinitidae）.The shape of the radial and interradial plates allows us to assign the specimen to Pararchaeocrinus.The Camerata is divided into two groups, the Diplobathrida and Monobathrida.It is the presence or absence of infrabasal plates that distinguishes one from the other; the diplobathrids have the infrabasal plates（dicyclic） whereas the monobathrids lack them（monocyclic）.Like Pararchaeocrinus or Trochocrinites, the infrabasal plates are considered to be hidden by the pentagonal structure at the cup base.Of the disparid specimens, four have a well preserved cup.The cup is small and monocyclic, and the arms are uniserial, which are typical of the Disparida.The two specimens have a spirally coiled anal tube and one specimen have the superradial and infraradial plate and the fused radial plate in between.These features allow us to assign these specimens to the Family Heterocrinidae.In other specimens without a poorly-preserved cup, these features are not well preserved, but the spirally coiled anal tube is observed in the two specimens.The diplobathrids have been reported from the Middle Ordovician strata of North America, Spain, and Wales, and the disparids from those of North America, Oman, South China and Morocco.This is the first report of the Middle Ordovician diplobathrid and disparid crinoids from the Sino-Korean platform of North China Block.
类型: 国际会议
作者: Hyeonmin PARK,Dong-Chan LEE,Seung-Bae LEE
来源: 第一届亚洲古生物学大会—暨中国古生物学会成立90周年纪念 2019-11-17
年度: 2019
分类: 基础科学
专业: 生物学,地质学
单位: Chungbuk National University, Earth Science EducationKorea Insitute of Geoscience and Mineral Resources,Geological Museum
分类号: Q91;P534.42
页码: 47
总页数: 1
文件大小: 101k
下载量: 1
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