A new genus of ionoscopiform fish (Halecomorphi) from the Lower Cretaceous (Albian) lithographic limestones of the Tlayúa Quarry, Puebla, Mexico

Abstract

Quetzalichthys perrilliataen. gen. and sp. is described based on five specimens from Lower Cretaceous (Middle-Upper Albian) limestones of the Tlayúa Quarry, near Tepexi de Rodríguez, Puebla, Mexico. This new taxon displays the diagnostic characters of Ionoscopiformes, which consequently designate it as a new member of this order of Mesozoic fishes. Additionally,Quetzalichthysn. gen. shares several derived characters withIonoscopusandOshunia, including the presence of more than 15 supraneurals, solid and well-ossified monospondylous vertebrae with two lateral longitudinal oval fossae, thin scales of the amioid type, and the ventral surface of some circumorbital bones being intensely pitted.Quetzalichthys perrilliataeis characterized by three unique characters: 26 abdominal centra, 21 principal dorsal fin rays, and two supraorbitals. Additionally, its unpaired fins and tail show conditions intermediate to those found inIonoscopusandOshunia.A cladistic analysis of Ionoscopiformes, including both taxa found in the Tlayúa Quarry (QuetzalichthysandTeoichthys), identifies two monophyletic families within the order, Ophiopsidae (includingOphiopsis, Macrepistius, Teoichthys) and Ionoscopidae (involvingIonoscopus, Oshunia, andQuetzalichthys).