A New Intriguing Teleost from the Albian Muhi Quarry, Central Mexico, and Early Euteleostean Diversification

The Albian Muhi Quarry of Central Mexico has produced a variety of fishes, among which the teleosts are the most diversified, including representatives of stem groups together with a variety of crown groups. A new genus and species, †Xeneichthys yanesi, is described based on a unique combination of characters, such as a dorsoventral elongation and narrowing of infraorbitals 2 and 3, preopercle, opercle, and cleithrum; absence of some bones, such as the infraorbital 5, interopercle, and pelvic plate and fin; presence of an elongated urostyle and a membranous outgrowth or stegural on the first uroneural; and cycloid and ctenoid scales on the flanks. Due to its combination of characters, †Xeneichthys yanesi is interpreted as belonging to a new extinct family, †Xeneichthyidae, which is considered as an Euteleostei or Euteleosteomorpha incertae sedis. The fish faunas of another Albian quarry, Tlayúa of Tepexi de Rodriguez, Puebla, and Muhi Quarry are compared, and although both contain taxa that can be assigned to stem teleosts (e.g., †ichthyodectiforms and †crossognathiforms), both also contain crown teleosts (e.g., elopomorphs, clupeomorphs, and euteleosts)—all of which are endemic to their respective quarries and make them important centers of diversification of fish faunas during the Early Cretaceous.