<i>Cipactlichthys</i><i> scutatus</i>, gen. nov., sp. nov. a New Halecomorph (Neopterygii, Holostei) from the Lower Cretaceous Tlayua Formation of Mexico

Based on specimens from the Lower Cretaceous Tlayua Formation of Mexico, we describe a new genus and species of Halecomorphi, Cipactlichthysscutatus gen. et sp. nov, which exhibits several diagnostic characters such as the dermal bones and the scales with ganoin and highly ornamented by numerous tubercles and ridges; parietal slightly longer than wide with approximately the same length as the frontal; jaws extending far, below the posterior orbital margin, reaching the posterior third of the postorbital plate; maxilla with a convexly rounded posterior margin; pectoral fin margins slightly convex; first ray of pectoral fin very long, reaching the posterior edge of the pelvic fin; about 37 preural vertebrae and 7 Ural centra; a series of hypertrophied scales just posterior to the cleithrum; arrangement of flank scales with two rows of deep scales; a series of dorsal and ventral scutes forming the dorsal and ventral midline, between the dorsal and anal fins and the caudal fin. A phylogenetic analysis including two outgroups and eleven neopterygians confirmed the monophyly of the Holostei as well as the monophyly of the Halecomorphi, although this last clade is weakly supported. Cipactlichthysscutatus was hypothesised as the sister-group of the (Ionoscopiformes + Amiiformes).本研究基于墨西哥下白垩统特拉瓦亚组（Tlayua Formation）的标本，记述了弓鳍鱼亚纲（Halecomorphi）一新属新种Cipactlichthys scutatus gen. et sp. nov.。该新类群具有多项鉴别特征：皮骨与鳞片覆有硬鳞质，且被大量瘤突与脊强烈纹饰；顶骨略长于宽，长度与额骨大致相当；颌骨延伸甚远，达眶后缘下方，直至眶后板的后三分之一区域；上颌骨后缘呈凸圆形；胸鳍边缘略呈凸形；第一胸鳍鳍条极长，延伸至腹鳍后缘；具约37枚尾前椎与7枚尾椎椎体；匙骨后方具一系列肥大鳞片；体侧鳞片呈两行深陷排列；背鳍、臀鳍与尾鳍之间的背、腹中线处，分别具有一系列背侧与腹侧骨板。本研究开展了包含2个外类群与11种新鳍鱼类的系统发育分析，结果证实全骨鱼总目（Holostei）为单系群，弓鳍鱼亚纲亦为单系群，但后者的单系支持度较弱。系统发育假说显示，Cipactlichthys scutatus为（离子鱼目（Ionoscopiformes）+弓鳍鱼目（Amiiformes））的姊妹群。