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Abstract Detail



Macroevolution

Wang, Xin [1].

Nanjinganthus: A New Evidence of Jurassic Angiosperms and its Implications on Angiosperm Evolution.

According to Arber and Parkin’s hypothesis (1907), the ancestral angiosperms should be Magnolia-like. Although the carpels in Magnoliaceae were hypothesized to be derived from non-existing “megasporophylls” bearing ovules along their margins (Wang and Luo 2013 and Miao et al. 2017), the situation got worse for APG system as there is no rational interpretation for the provenance of Amborella carpels yet. Many palaeobotanists chose to believe that Angiosperms date back only to the Early Cretaceous. This speculation is undermined by increasing fossil evidence. The recognition of Nanjinganthus is based on the observation of more than 200 fossils of flowers. The occurrence of sepals, petals, dendroid formed style, and enclosed ovules inside an inferior ovary suggests that Nanjinganthus is a bona fide angiosperm, despite its Early Jurassic age (>174 Ma). Apparently, the character combination in Nanjinganthus is not expected by any armchair strategies of angiosperm evolution. Re-examination of the former “favoring” evidence farther supports this conclusion. Although Arber and Parkin claimed their hypothesis was based on fossil evidence, Parkin (1925) admitted that such support was lacking. Canright (1960) supported Arber and Parkin with anatomy of magnoliaceous carpels, but he altered the information about ovule insertion in carpels. Archaeanthus (Dilcher and Crane, 1984) were thought related to Magnoliaceae with typical conduplicate carpels with ventrally inserted ovules, but at least some of the ovules are actually inserted along the dorsal veins in Archaeanthus. Similar misinterpretation was repeated in Archaefructus (Sun et al. 1998, 2002), which actually has whorled (rather than the expected helical) arranged carpels with dorsally inserted ovules (Wang and Zheng, 2012). Monetianthus (Friis et al., 2009) were claimed with two integuments, but this claim was not supported by any observation in the paper. All these specious support for Arber and Parkin’s hypothesis actually incurs doubt over the hypothesis, suggesting that the hypothesis was a swindle from the very beginning, and many (if not all) botanists have been swindled and fallen into the pitfall in a century-long period. Resurgent studies on the carpels of Magnoliaceae (Liu et al., 2014; Zhang et al., 2017) suggest that a carpel in Magnoliaceae is composite organ derived from a former branch bearing ovules and its subtending leaf. The carpel derivation of Amborella may be interpreted in a similar way. This interpretation shared between Magnolia and Amborella makes angiosperms not unique among seed plants any more as axillary branching pattern is seen in many seed plants.


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1 - 39 Beijing Dong Road, Nanjing, 210008, China

Keywords:
angiosperms
First flowering date
Phylogenetic origin
Jurassic
carpel
homology
Evolution
Systematics.

Presentation Type: Oral Paper
Session: 18, Macroevolution I
Location: 105/Mayo Civic Center
Date: Tuesday, July 24th, 2018
Time: 8:15 AM
Number: 18002
Abstract ID:182
Candidate for Awards:None


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