The genera that never were: The impact of Janeia and Janacekia on phyletic and taxonomic relations within the Solemyidae (Bivalvia: Protobranchia)

IF 2 4区地球科学 Q1 Earth and Planetary Sciences

Palaeontologia Electronica Pub Date : 2021-03-29 DOI:10.26879/945

J. Bailey

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引用次数: 1

Abstract

Proposed taxonomies of the Solemyoidea remain conflicted, particularly regarding the familiar genera, Solemya and Acharax, whose close phyletic kinship has been obscured by: 1) imperfect understanding of the chronological morphogenesis of diagnostically important ligament support structures, and 2) misconceptions triggered by two problematic Paleozoic genera, Janeia and Janacekia, including the prevalent mischaracterization that the primary ligament in Janeia was located in an internal chondrophore. Whereas Janacekia and certain Janeia are synonyms of Acharax, other alleged Janeia are shown to be clinopisthins such as Dystactella and Clinopistha. Morphological analysis supports DNA studies suggesting Acharax and Solemya are monophyletic, thereby challenging recent taxonomies placing them in separate families or superfamilies. The primary ligaments of Acharax and Solemya are basically similar (opisthodetic, parivincular, attached at nymphae), the main differences being placement: external in Acharax but slightly internal (submarginal) in Solemya. Character analyses suggest the external nymphae of Acharax are plesiomorphic, arising by the Early Devonian, whereas the submarginal placement of the nymphae in Solemya is shown to be a Mesozoic apomorphy involving depression and secondary enclosure of the ligament and nymphae by a shelly outer layer. Nymphal enclosure has had two concomitant effects: 1) dorsal occlusion of the posterior adductor muscle; 2) fusion of the nymphae to internal buttresses that plesiomorphically functioned as simple reinforcement for the anterior margin of the posterior adductor muscles whereas, by exaptation, they become apomorphically modified to serve as supporting braces for the submarginal nymphae by dorsally uniting with them. Jack Bowman Bailey. Department of Earth, Atmospheric and Geographic Information Sciences Western Illinois University, 1 University Circle, Macomb, IL 61455 USA. jb-bailey@wiu.edu

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从未是的属：Janeia和Janacekia对Solemyidae（双壳纲：原鳃亚目）的系统和分类学关系的影响

Solemyoidea的拟议分类法仍然存在冲突，特别是关于熟悉的属Solemya和Acharax，它们的密切亲缘关系被以下因素所掩盖：1）对诊断上重要的韧带支撑结构的时间形态发生的不完全理解，以及2）两个有问题的古生代属Janeia和Janacekia引发的误解，包括普遍存在的Janeia初级韧带位于内部软骨团的错误描述。尽管Janacekia和某些Janeia是Acharax的同义词，但其他被指控的Janeia被证明是单倍体，如Dystactella和Clinopistha。形态学分析支持DNA研究，表明Acharax和Solemya是单系的，从而挑战了最近将它们分为单独的科或超科的分类法。Acharax和Solemya的初级韧带基本相似（opisthodetic，parvincular，附着在若虫处），主要区别在于位置：Acharax的外侧韧带，Solemya稍微内侧（亚边缘）韧带。特征分析表明，Acharax的外部若虫是由早泥盆纪产生的蛇颈虫，而若虫在Solemya的亚边缘位置被证明是中生代的变形，包括凹陷和韧带和若虫被贝壳外层次级包围。睡莲被包围有两个共同的影响：1）后内收肌的背侧闭塞；2）若虫与内支的融合，内支在形态上起到了后内收肌前边缘的简单加固作用，而通过扩张，它们经过变形修饰，通过与它们的背部结合，成为亚边缘若虫的支撑支架。杰克·鲍曼·贝利。地球、大气和地理信息科学系，西伊利诺伊大学，1 University Circle，Macomb，IL 61455 USA。jb-bailey@wiu.edu

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来源期刊

Palaeontologia Electronica 地学-古生物学

CiteScore

3.60

自引率

0.00%

发文量

审稿时长

>12 weeks

期刊介绍： Founded in 1997, Palaeontologia Electronica (PE) is the longest running open-access, peer-reviewed electronic journal and covers all aspects of palaeontology. PE uses an external double-blind peer review system for all manuscripts. Copyright of scientific papers is held by one of the three sponsoring professional societies at the author''s choice. Reviews, commentaries, and other material is placed in the public domain. PE papers comply with regulations for taxonomic nomenclature established in the International Code of Zoological Nomenclature and the International Code of Nomenclature for Algae, Fungi, and Plants.