Ancient herring from the Tlayْa Quarry (Cretaceous, Albian) near Tepexi de Rodيguez, Puebla State, central Mexico, closing the gap in the early diversification of Clupeomorpha

Ranulfoichthys dorsonudum gen. and sp. nov. is described based on well-preserved specimens collected in the marine Albian limestones of Tlayْa Quarry, Puebla State, Mexico. This new species shows the diagnostic characters of the Superorder Clupeomorpha, its hypural 2 is fused with the first ural centrum whereas the hypural 1 is autogenous, its supratemporal commissural sensory canal passes through the parietals and supraoccipital, and the abdominal border of its trunk is completely covered with spiny scutes. Ranulfoichthys gen. nov. also shares primitive characters with the Order Ellimmichthyiformes, including the contact between the parietals, the absence of the recessus lateralis, and the presence of the beryciform foramen in the anterior ceratohyal; however, this new species has unmodified scales along its predorsal border while Ellimmichthyiformes have a distinctive predorsal series composed of scutes with expanded lateral wings. Additionally, this new species differs from other clupeomorphs because its interfrontal suture is deeply sinuous just posterior to the orbit and its first uroneural is so long that it almost reaches the posterior edge of preural centrum 3. This new species is not the oldest clupeomorph fossil so far known but it clearly differs from Ellimmichthyiformes, Clupeiformes, Armigatus and Ornategulum; and it represents a basal clupeomorph that contributes to our understanding of the early diversification of the Clupeomorpha.