The study on the origin and evolution of sigillid ostracods characteristic of submarine caves

Sigillids是原始的足足介形类动物，有不等长的瓣膜和许多小的内收肌疤痕。作者在太平洋珊瑚礁中发现了4个轮虫属Kasella Tabuki和Hanai 1999，以及A、B和C属3个新属。在本研究中，作者详细地研究了所有剑齿类属的甲壳特征，并试图证明各属之间的系统发育亲缘关系以及滚球型剑齿类的起源和进化。由于纹饰的存在，剑齿类被分为两个分类群：由Cardobairdia、Saipanetta和A属组成的非花饰类，以及Kasella、B属和C属的花饰类，Cardobairdia在右瓣具有原始铰链，与装饰类类很接近。与其他属不同的是，塞帕内门和A属具有“双层铰链”。华丽的B属在侧面轮廓和内收肌痕的形状上更接近于Cardobairdia。C属不仅与Kasella有许多关键的甲壳特征，而且与B属也有许多相似的关键特征。虽然Kasella有许多“高级甲壳特征”，但它表明这些特征可能是所谓的回归所致，例如右瓣膜上的后腹棘也出现在Cardobairdia上，以及类似于健康类动物的原始铰链结构。只有非轮虫类的Cardobairdia和Saipanetta，自侏罗纪以来才有化石记录。这一事实表明，游泳型手语起源于非游游性手语。A属可能来源于Saipanetta或其近缘。B属被认为起源于Cardobairdia或其近缘，C属起源于B属或其近亲，Kasella起源于C属或其近亲。

Sigillids are primitive podocopid ostracods having unequal valves and many small adductor muscle scars. The author found four troglobitic sigillid genera, Kasella Tabuki and Hanai 1999 and three new genera of Genus A, B and C, from coral reefs in the Pacific. In this study, the author taxonomically examined the carapace features of all the sigillid genera in detail and tried to demonstrate the phylogenetic affinities among the genera and the origin and evolution of the troglobitic sigillids.Sigillids are classified into two taxonomical groups for the presence of ornamentation: the non-ornate sigillids composed of Cardobairdia, Saipanetta and Genus A, and the ornate sigillids of Kasella, Genus B and Genus C. Cardobairdia is close to the ornate sigillids in having the 'original hingement' in the right valve. Saipanetta and Genus A differ from the other genera in having the 'two-layered hingement'. The ornate Genus B is closer to Cardobairdia in lateral outline and shape of adductor scar. Genus C shares many key carapace features not only with Kasella, but also with Genus B. While Kasella has many 'advanced carapace features', it shows the features possibly resulted from so-called reversion such as a posteroventral spine on the right valve appeared also in Cardobairdia and a primitive hingement structure similar to that of healdioideans.Only the non-troglobitic sigillids, Cardobairdia and Saipanetta, have the fossil records since the Jurassic. This fact suggests that the troglobitic sigillids derived from the non-troglobitic sigillids. The Genus A possibly derived from Saipanetta or its relatives. Genus B is thought to have originated from Cardobairdia or its relatives, Genus C from Genus B or its relatives and Kasella from Genus C or its relatives.