Skeletomuscular anatomy of the harvestman Leiobunum aldrichi (Weed, 1893) (Arachnida: Opiliones: Palpatores) and its evolutionary significance

被引:22
作者
Shultz, JW [1 ]
机构
[1] Univ Maryland, Dept Entomol, College Pk, MD 20742 USA
关键词
Arthropoda; Chelicerata; Gagrellidae; morphology; muscle; phylogeny; homology; comparative anatomy;
D O I
10.1111/j.1096-3642.2000.tb01522.x
中图分类号
Q95 [动物学];
学科分类号
071002 ;
摘要
Skeletal muscles of the North American harvestman Leiobunum aldrichi are exhaustively surveyed and compared with other chelicerates to clarify the evolutionary morphology and phylogenetic relationships of arachnids. Representatives of 101 muscle groups are described and illustrated, and their possible functions are proposed. Comparisons of the feeding apparatus of L. aldrichi with that of other opilions, especially Sire (Cyphophthalmi) and Acromares (Laniatores), and two scorpion genera (Centruroides, Pandinus) indicate that the pharyngeal apparatus in L. aldrichi is derived and that its ability to accommodate large food particles is a secondary rather than primitive condition. Comparisons reveal several possible synapomorphies between Opiliones and Scorpiones suggesting that these orders may be sister groups. Apparently unique synapomorphies include an extrinsic cheliceral muscle that arises from the carapace and inserts on the second cheliceral article (deutomerite); an epistome divided into distal and proximal parts by a transverse sulcus; pharyngeal dilator muscles supported by a peripharyngeal skeleton formed by one dorsomedial and two ventrolateral epistomal processes, the latter also with muscular attachments to the endosternite; a specialized preoral chamber (stomotheca) derived from extensions (coxapophyses) of the coxae of the pedipalp and first two leg pairs; internal processes associated with the coxapophyses that serve, in part, as an attachment for muscles operating the coxa-trochanter joints, and lateral endosternal suspensor muscles that insert on the arthrodial membrane between the leg coxae. These are the first observations providing explicit support for an Opiliones-Scorpioncs clade. (C) 2000 The Linnean Society of London.
引用
收藏
页码:401 / 438
页数:38
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