Revision of the mollisoniid chelicerate(?) Thelxiope, with a new species from the middle Cambrian Wheeler Formation of Utah

被引:7
|
作者
Lerosey-Aubril, Rudy [1 ,2 ]
Skabelund, Jacob
Ortega-Hernandez, Javier [1 ,2 ]
机构
[1] Harvard Univ, Dept Organism & Evolutionary Biol, Cambridge, MA 02138 USA
[2] Harvard Univ, Museum Comparat Zool, Cambridge, MA 02138 USA
来源
PEERJ | 2020年 / 8卷
关键词
Exceptional preservation; Chelicerata; Mollisoniida; Mollisoniidae; Tagmosis; Miaolingian; Tremadocian; BURGESS SHALE; STEPHEN FORMATION; ARTHROPOD; LAGERSTATTE; ASSEMBLAGE; COMMUNITY; TAGMOSIS; HOUSE;
D O I
10.7717/peerj.8879
中图分类号
O [数理科学和化学]; P [天文学、地球科学]; Q [生物科学]; N [自然科学总论];
学科分类号
07 ; 0710 ; 09 ;
摘要
The recent re-interpretation of the Lower Palaeozoic euarthropod group Mollisonia as belonging to Chelicerata has triggered a renewed interest for the poorly known family Mollisoniidae. In this contribution, we revise the anatomy, taxonomic diversity, and systematics of Thelxiope, the sister-taxon of Mollisonia. This mollisoniid genus comprises four species, and is characterized by the presence of one cephalic, seven thoracic (one per tergite), and three pygidial long sagittal spines. The type species, T. palaeothalassia Simonetta & Delle Cave, is a rare taxon in the Wuliuan Burgess Shale Formation of Canada, which can be recognized by the hypertrophy of a single of its sagittal spines, the posteriomost one. T. spinosa (Conway Morris & Robison)-a species originally assigned to a distinct genus 'Ecnomocaris' herein synonymised with Thelxiope-is known from a single specimen found in the Drumian Wheeler Formation of the House Range of Utah. It differs from the type-species in the hypertrophy of both the anteriormost (cephalic) and the posteriormost (third pygidial) sagittal spines. The same Wheeler strata have also yielded a single specimen of a new taxon, T. holmani sp. nov., which lacks hypertrophied sagittal spines and features blunt thoracic tergopleural tips. A putative fourth species, referred to Thelxiope sp. nov. A, extends the stratigraphical range of Thelxiope to the Lower Ordovician (Tremadocian), and its palaeographic range to West Gondwana. Currently under study, this relatively common component of the lower Fezouata Shale fauna is only briefly discussed. Features characterizing the genus Thelxiope and its components almost exclusively pertain to the sagittal spines, for the scarcity and inconsistent preservation of the Cambrian materials as-yet available preclude a confident assessment of the variability of other morphological features. The pygidium in Thelxiope and Mollisonia is not composed of four, but three tergites essentially similar to thoracic ones, except for the lack of articulations.
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页数:29
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