The eldest grandmother, late Miocene †<i>Jenynsia herbsti</i> sp. nov. (Teleostei, Cyprinodontiformes), and the early diversification of the Anablepidae
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The Anablepidae are a family of mostly livebearing cyprinodontiform fishes with few living representatives, but an increasingly diverse fossil record. According to recent contributions, an important part of their evolution can be traced back to Miocene remains in Central and Northwestern Argentina. In this article we describe the oldest known fossil species of <i>Jenynsia</i>, the most diverse genus of the family, from upper Miocene lacustrine deposits in Catamarca, Argentina. The new taxon is herein described based on many specimens of both females and sexually dimorphic males and a phylogenetic hypothesis is provided. The new species was recovered as the sister group of the remaining taxa of the nominal subgenus <i>Jenynsia</i> in our final hypothesis. However, it was also recovered as forming a clade with the extinct †<i>Sachajenynsia pacha</i>, and this clade as sister group of the subgenus <i>Jenynsia</i>, under one of the explored analytical conditions. The evolutionary history of <i>Jenynsia</i> was related in the literature to marine transgressions and the species radiation was dated through evolutionary model-based methods. Our findings and interpretations challenge the mostly marine-driven diversification of <i>Jenynsia</i> and the new taxon is older than predicted by the published estimations. This study reinforces the hypothesis that sexual reproduction by means of internal fertilization was already well-established in the Miocene for anablepids.
四眼鱼科（Anablepidae）是一类多数为胎生的鳉形目（Cyprinodontiformes）鱼类，现生类群稀少，但化石记录愈发丰富。根据最新研究成果，该类群演化历程中的重要阶段可追溯至阿根廷中部与西北部的中新世地层化石遗存。本文记述了该科物种多样性最高的詹氏鳉属（*Jenynsia*）目前已知最古老的化石物种，其化石产自阿根廷卡塔马卡省的晚中新世湖相沉积地层中。本新类群的描述基于大量雌性与具性二型特征的雄性标本，并给出了系统发育假说。在我们的最终系统发育假说中，该新种被聚类为命名亚属詹氏鳉（*Jenynsia*）其余类群的姊妹群。但在所尝试的其中一种分析条件下，该新种与已灭绝的†萨氏詹氏鳉（*Sachajenynsia pacha*）共同构成一个演化支，且该演化支为詹氏鳉亚属的姊妹群。以往文献中将詹氏鳉属的演化历史与海侵事件相关联，并通过基于演化模型的方法对其物种辐射演化时间进行了定年。本研究的发现与解读对“詹氏鳉属的多样化主要由海侵驱动”这一观点提出了挑战，且该新类群的地质时代早于已发表研究的预测时间。本研究进一步佐证了“中新世时期四眼鱼科（Anablepidae）类群已普遍确立体内受精的有性生殖方式”这一假说。
