کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4750389 1642515 2012 11 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
A polyxylic Cycad trunk from the Middle Jurassic of western Liaoning, China, and its evolutionary implications
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فسیل شناسی
پیش نمایش صفحه اول مقاله
A polyxylic Cycad trunk from the Middle Jurassic of western Liaoning, China, and its evolutionary implications
چکیده انگلیسی

A new fossil cycad stem Sinocycadoxylon liianum gen. et sp. nov. is described based on a well-preserved petrified specimen collected from the Middle Jurassic of Beipiao, Liaoning Province, China. The stem is composed of a small pith, a polyxylic vascular cylinder and cortex. The pith is parenchymatous with medullary vascular bundles, transfusion cells and mucilage canals. The polyxylic vascular cylinder consists of sixteen centrifugal rings and one centripetal vascular ring, all with distinct growth rings in secondary xylem. The presence of polyxyly with growth rings distinguishes this new genus from all fossil and extant Cycadales. The primary xylem is mesarch. Secondary xylem tracheids have araucarioid radial pitting. The rays are uni- or multiseriate and the latter are usually accompanied by mucilage canals and transfusion cells. This polyxylic stem is believed to be related to the Encephalartoideae of Zamiaceae. The new find provides new insights into cycad evolution which is consistent with former phylogenetic analyses indicating that Cycadales originated form Medullosales.


► A polyxylic cycad stem discovered from the Middle Jurassic of China.
► Cylindrical vascular system consist of seventeen vascular rings surrounding pith.
► The first vascular ring is centripetal and others are centrifugal.
► Their secondary xylem with distinct growth rings.
► It provides a new insight into cycad evolutionary.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Review of Palaeobotany and Palynology - Volume 183, 1 September 2012, Pages 50–60
نویسندگان
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