A New Voltzian Seed Cone from the Early Cretaceous of Mongolia and Its Implications for the Evolution of Ancient Conifers
A New Voltzian Seed Cone from the Early Cretaceous of Mongolia and Its Implications for the Evolution of Ancient Conifers
复制标题
DOI：
10.1086/683060
复制
发表时间：
2015-08
影响因子：
2.3
通讯作者：
Fabiany Herrera;G. Shi;A. Leslie;Patrick Knopf;N. Ichinnorov;Masamichi Takahashi;P. Crane;P. Herendeen
中科院分区：
文献类型：
--
作者：
Fabiany Herrera;G. Shi;A. Leslie;Patrick Knopf;N. Ichinnorov;Masamichi Takahashi;P. Crane;P. Herendeen
研究的优先权。大量的化石和分子证据表明，所有现存的针叶树科都是在早白垩世建立的。然而，对导致这些现存家族进化的世系的认识和理解仍然不完整。晚古生代到早中生代Voltziales针叶树-也被称为过渡针叶树，通常具有多裂的胚珠鳞片-被假设为现代冠状针叶树的干谱系之一。本文描述了一个精美保存的伏茨种子从蒙古的Aptian-Albian引进新的分类多样性和形态数据到复杂的模式针叶树进化的球果。方法论从Tevshiin Govi地区收集的大量褐煤样品在水中分解，用盐酸和氢氟酸清洗，洗涤并风干。使用LM、SEM和X射线显微断层扫描检查化石。初步结果。蒙古沙芥属新种（Krassilovia mongolica gen. et sp. nov.）的球果具螺旋状排列、覆瓦状、紧密互锁的苞片鳞片复合体。每个成熟的苞片鳞片复合体由一个不明显的苞片部分融合到一个五裂鳞片的柄。其中三个叶位于远侧（总是指向远离锥体基部），而另外两个叶位于近侧（总是指向锥体基部）。多达5个倒生翅的种子存在于胚珠鳞片的正面。晚古生代到早白垩世多裂胚珠鳞片的系统回顾，连同形态分支分析支持放置在一个新属内Voltziales Voltzian分支的蒙古材料。结论. Krassilovia mongolica提供了证据，证明已经灭绝的伏茨期针叶树的额外多样性，并表明在早白垩世，有些针叶树仍然生活在东亚的森林沼泽环境中。新的化石分类群还显示了苞片鳞片复合体和圆锥体的新形态适应（即，叠瓦状和互锁），用于保护胚珠/种子，这与新昆虫和其他动物摄食策略的出现大致同时发生。
Premise of research. Abundant fossil and molecular evidence suggests that all extant conifer families were established by the Early Cretaceous. However, the recognition and understanding of the lineages that lead to the evolution of these extant families remain incomplete. Late Paleozoic to Early Mesozoic Voltziales conifers—also known as transitional conifers, usually with multilobed ovuliferous scales—have been hypothesized to be among the stem lineages of modern crown conifers. This article describes an exquisitely preserved voltzian seed cone from the Aptian-Albian of Mongolia that introduces new taxonomic diversity and morphological data into the complex pattern of conifer evolution. Methodology. Bulk lignite samples collected from the Tevshiin Govi locality were disaggregated in water, cleaned with hydrochloric and hydrofluoric acids, washed, and dried in air. Fossils were examined using LM, SEM, and X-ray microtomography. Pivotal results. Krassilovia mongolica gen. et sp. nov. has seed cones with helically arranged, imbricated, and tightly interlocked bract-scale complexes. Each mature bract-scale complex consists of an inconspicuous bract partially fused to the stalk of a five-lobed scale. Three of the lobes are distal (always pointing away from the cone base), while the other two are proximal (always pointing toward the cone base). Up to five inverted winged seeds are present on the adaxial side of the ovuliferous scales. A systematic review of Late Paleozoic to Early Cretaceous multilobed ovuliferous scales—together with a morphological cladistic analysis—supports the placement of the Mongolian material in a new genus within the voltzian clade of the Voltziales. Conclusions. Krassilovia mongolica provides evidence of the additional diversity of extinct voltzian conifers and shows that some persisted to inhabit forest-moor swamp environments in eastern Asia during the Early Cretaceous. The new fossil taxon also shows novel morphological adaptations of the bract-scale complexes and the cone (i.e., imbrication and interlocking) for the protection of the ovules/seeds that are broadly concurrent with the appearance of new insect and other animal feeding strategies.