Resolving the systematic and phylogenetic position of isolated ovules: a case study on a new genus from the Permian of China MURICOSPERMA GUIZHOUENSIS GEN. & SP. NOV.
Resolving the systematic and phylogenetic position of isolated ovules: a case study on a new genus from the Permian of China MURICOSPERMA GUIZHOUENSIS GEN. & SP. NOV.
复制标题
解析离体胚珠的系统发育和系统发育位置：以中国二叠纪MURICOSPERMA GUIZHOUENSIS GEN.一新属为例。
DOI：
10.1111/j.1095-8339.2010.01069.x
复制
发表时间：
2010
影响因子：
2.4
通讯作者：
SEYFULLAH L
中科院分区：
文献类型：
--
作者：
SEYFULLAH L
孤立的胚珠出现在许多化石植物组合中，它们为种子植物多样性和进化提供了重要的见解。然而，在许多情况下，胚珠不能归因于种子植物的单个群体，限制了可以从其他特征良好的化石分类群中进行的系统和进化评估。本文描述了在贵州省宣威组凝灰质沉积物中发现的一种新的胚珠。胚珠具有180°旋转对称性，珠被由1/2厚的肉种皮、均匀厚的核种皮和均匀薄的内种皮组成。珠心至少基部附着于珠被，并含有一个塌陷的种子大孢子;珠心顶端缺席。珠被和珠心都由胚珠主平面上的成对维管束进行血管化;珠被维管束比珠心维管束大得多，珠心维管束从圆锥形的维管垫中出现。基于连续果皮的三维重建的生成揭示了胚珠的总体形态和组织，并突出显示了与心果类胚珠（胚珠形状，珠被的组织学特征）一致的特征的存在，以及更典型的lagenostomalean和trigonocarpalean型胚珠（大珠被束，珠心束的存在）的特征。为了评估胚珠的亲和力和进化意义，它已被列入cardiocarpalean，lagenostomalean和trigonocarpalean型胚珠的分支矩阵。结果将胚珠内的cardiocarpalean组胚珠已知已产生的几个植物群，包括科达的针叶植物，pteridosperms和古生代针叶树。支序拓扑学支持本种属级的区分，需要建立Muricosperma guizhouensisSeyfullah & J. Hiltongen。nov. Hydrasperman pteridosperms产生的Lagenostomalean胚珠形成一个基本的并系级，而由有髓的pteridosperms产生的trigonocarpalean胚珠形成一个单系群，其中Stephanospermum相对于Rhynchosperma和Pachytesta是并系的。因此，M。bulbosumis转移到新属WhitadderaSeyfullah & J.希尔顿as W.作者单位Author Agencies：J.
Isolated ovules occur in many fossil plant assemblages, where they provide important insights into seed-plant diversity and evolution. However, in many cases, the ovules cannot be attributed to individual groups of seed plants, restricting systematic and evolutionary assessments that can be made from otherwise well-characterized fossil taxa. In the present paper, we describe a new kind of ovule discovered in tuffaceous sediments from the Permian-aged Xuanwei Formation in Guizhou Province, China. This ovule has 180° rotational symmetry and an integument comprising a variably thick sarcotesta, a uniformly thick sclerotesta and a uniformly thin endotesta. The nucellus is attached to the integument at least basally and contains a collapsed seed megaspore; a nucellar apex is absent. Both the integument and nucellus are vascularized by paired bundles in the major plane of the ovule; the integumentary bundles are considerably larger than the nucellar bundles and the nucellar bundles emerge from a conical vascular pad. Generation of a three-dimensional reconstruction based on serial peels revealed the gross morphology and organization of the ovule and highlighted the presence of features consistent with cardiocarpalean-type ovules (ovule shape, histological features of the integument) and also features more typical of lagenostomalean- and trigonocarpalean-type ovules (large integumentary bundles, presence of nucellar bundles). To assess the affinity and evolutionary significance of the ovule, it has been included in a cladistic matrix of cardiocarpalean-, lagenostomalean- and trigonocarpalean-type ovules. Results place the ovule within the cardiocarpalean group of ovules known to have been produced by several plant groups, including cordaitean coniferophytes, pteridosperms and Palaeozoic conifers. The cladistic topology supports generic level distinction of the present species, requiring the establishment ofMuricosperma guizhouensisSeyfullah & J.Hiltongen. & sp. nov. Lagenostomalean ovules produced by hydrasperman pteridosperms form a basal paraphyletic grade, whereas trigonocarpalean ovules produced by medullosan pteridosperms form a monophyletic group in whichStephanospermumis paraphyletic with respect toRhynchospermaandPachytesta.The results also place the Mississippian ovuleMitrospermum bulbosumapart from all of the Pennsylvanian species ofMitrospermumthat form a strongly supported clade. Consequently,M. bulbosumis transferred to the new genusWhitadderaSeyfullah & J.Hilton asW. bulbosa(Long) Seyfullah & J.Hilton.