Palaeozoic fern-like plants show great diversity in their morphology and/or anatomy. Within this group, a novel taxon, Xinhangia spina gen. et sp. nov., is now reported from the Upper Devonian (Famennian) Wutong Formation of Anhui Province, China. The primary and secondary branches are borne alternately and sometimes in a triseriate pattern. Spines are evident on the main axes or stems and on the primary branches. Vegetative ultimate appendages with recurved tips are alternate, usually dichotomous 1–2 times, and sometimes as an aphlebia located at the base of primary or secondary branches. Fertile ultimate appendages are alternate, usually dichotomous 1–2 times, and terminate in elongated and paired sporangia. The stele has a clepsydroid-like primary xylem with each end bearing a protoxylem strand. The secondary xylem surrounding the primary xylem illustrates uniseriate rays. With rare divisions in both the vegetative and fertile ultimate appendages, Xinhangia represents a morphologically primitive plant. It is of uncertain affinity at the class or order level. The stelar architecture suggests that the clepsydroid stele may not be emphasized in discussing the relationship among fern-like plants such as rhacophytaleans.
The amount of zircon U-Pb geochronological data for China has grown rapidly in recent years. Nearly 410,000 items of zircon U-Pb geochronological data, representing more than 7,000 relevant articles in the Elsevier Science Database, have been collected to a database in this research. Statistics on the ages and absolute errors of these collated data, yielded smallest standard errors for ( 206 Pb/ 238 U), ( 207 Pb/ 235 U), and ( 207 Pb/ 206 Pb) ages within respective time intervals of < 1388.96 Ma, 1388.96-3282.52 Ma, and > 3282.52 Ma. The ages and their absolute errors were determined using three main geochronology methods, based on laser ablation inductively coupled mass spectrometer (LA-ICP -MS), sensitive high-resolution ion microprobe (SHRIMP), and secondary ion mass spectrometer (SIMS) measurements. We compared the influence of these different methods on errors for each age interval. In addition, using a Gaussian model of multi-peak fitting of zircon U-Pb age frequencies, we identified seven growth peaks in zircons from the
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