School of Earth, Atmospheric and Environmental Sciences and The Manchester X-Ray Imaging Facility, School of Materials, The University of Manchester, Manchester M13 9PL, UK.
Division of Invertebrate Zoology, American Museum of Natural History, Central Park West at 79(th) Street, New York, NY 10024, USA.
Curr Biol. 2014 May 5;24(9):1017-23. doi: 10.1016/j.cub.2014.03.039. Epub 2014 Apr 10.
Successfully placing fossils in phylogenies is integral to understanding the tree of life. Crown-group Paleozoic members of the arachnid order Opiliones are indicative of ancient origins and one of the earliest arthropod terrestrialization events [1, 2]. Opiliones epitomize morphological stasis, and all known fossils have been placed within the four extant suborders [3-5]. Here we report a Carboniferous harvestman species, Hastocularis argusgen. nov., sp. nov., reconstructed with microtomography (microCT). Phylogenetic analysis recovers this species, and the Devonian Eophalangium sheari, as members of an extinct harvestman clade. We establish the suborder Tetrophthalmi subordo nov., which bore four eyes, to accommodate H. argus and E. sheari, the latter previously considered to be a phalangid [6-9]. Furthermore, embryonic gene expression in the extant species Phalangium opilio demonstrates vestiges of lateral eye tubercles. These lateral eyes are lost in all crown-group Phalangida, but are observed in both our fossil and outgroup chelicerate orders. These data independently corroborate the diagnosis of two eye pairs in the fossil and demonstrate retention of eyes of separate evolutionary origins in modern harvestmen [10-12]. The discovery of Tetrophthalmi alters molecular divergence time estimates, supporting Carboniferous rather than Devonian diversification for extant suborders and directly impacting inferences of terrestrialization history and biogeography. Multidisciplinary approaches integrating fossil and neontological data increase confidence in phylogenies and elucidate evolutionary history.
成功地将化石纳入系统发育是理解生命之树的关键。蛛形纲目 Opiliones 的古生代冠群成员是古老起源的指示物，也是最早的节肢动物陆生化事件之一[1,2]。Opiliones 是形态停滞的缩影，所有已知的化石都被归入四个现存的亚目[3-5]。在这里，我们报告了一种石炭纪 harvestman 物种，Hastocularis argusgen. nov., sp. nov.，它是通过微断层扫描（microCT）重建的。系统发育分析恢复了该物种以及泥盆纪的 Eophalangium sheari，它们是一个已灭绝的 harvestman 分支的成员。我们建立了一个新的亚目 Tetrophthalmi subordo nov.，它有四只眼睛，容纳了 H. argus 和 E. sheari，后者以前被认为是 phalangid[6-9]。此外，现存物种 Phalangium opilio 的胚胎基因表达表明存在侧眼节的痕迹。这些侧眼在所有冠群 Phalangida 中都丢失了，但在我们的化石和外群蛛形纲目中都观察到了。这些数据独立地证实了化石中存在两对眼睛的诊断，并证明了现代 harvestmen 中保留了具有不同进化起源的眼睛[10-12]。Tetrophthalmi 的发现改变了分子分歧时间估计，支持现生亚目的石炭纪而不是泥盆纪多样化，并直接影响对陆生化历史和生物地理学的推断。整合化石和现代数据的多学科方法增加了对系统发育的信心，并阐明了进化历史。
