Paleocene fishes from Palenque, Chiapas, southeastern Mexico

Abstract

This paper provides the first geological and paleontological data on two Mexican Paleocene fossil localities, the División del Norte and the Belisario Domínguez quarries, recently discovered near Palenque, State of Chiapas. Both are part of the marine outcrops previously known as the Tenejapa (toward the West) and the Lacandón formations (toward the East and in Guatemala). Since the limits of these formations remain unclear in the Palenque area, the geological association of these localities is referred to as the Paleocene Tenejapa-Lacandón Unit. The fossil fishes are particularly abundant and well preserved in these sites; they represent taxa previously known from Eocene localities around the world, whose strata were deposited under continental and marine conditions. This new assemblage is peculiar because it includes potential new species of Pycnodontiformes, Osteoglossiformes, Anguillifromes, Clupeiformes, and "serranids" that might expand their temporal and paleogeografical distribution worldwide and therefore become important elements to understand the evolution of these groups. These 63 my fish localities are the closest, temporally and geographically, sites to the Chicxulub Crater, a crater intimately associated to the Mass Extinction Event at the Cretaceous-Paleogene boundary (K/P). These newly localities represent an important paleontological scenario that will contribute to achieve a better understanding of the marine vertebrate communities throughout this important geological event.

Eekaulostomus cuevasae gen. and sp. nov., an ancient armored trumpetfish (Aulostomoidea) from Danian (Paleocene) marine deposits of Belisario Domínguez, Chiapas, southeastern Mexico

“…The División del Norte quarry is another small quarry near Palenque that bears similar fossils on strata that also belong to this geological unit. The fish assemblage recovered in these quarries includes eels, herrings, pycnodonts, "serranids", osteoglossids, gonorynchiforms, and other still unidentified teleostean fishes Alvarado-Ortega, 2008, 2009;Alaniz-Galvan and Alvarado-Ortega, 2011;Solano-Templos and Alvarado-Ortega, 2013;Alvarado-Ortega et al, 2015;.…”

The first occurrence of a fresh water percomorph fish (Actinopterygii: Teleostei) in the Ixtapa Formation (Miocene), Chiapas, southeastern Mexico

“…Cenozoic freshwater fish localities containing spiny-rayed fishes are scarce in Mexico. Most of the fossil beds with percomorph fossil records represent marine environments and belong to the Paleogene of Chiapas or to the Neogene of the Baja California peninsula (González-Rodríguez et al, 2013;Alvarado-Ortega et al, 2015;Guzmán, 2015). Inside the Paleogene strata, currently, are known flute-mouth fishes, sea basses, and some undetermined percomorphs (Alvarado-Ortega et al, 2015;Cantalice and Alvarado-Ortega, 2017;Cantalice et al, 2018).…”

“…Most of the fossil beds with percomorph fossil records represent marine environments and belong to the Paleogene of Chiapas or to the Neogene of the Baja California peninsula (González-Rodríguez et al, 2013;Alvarado-Ortega et al, 2015;Guzmán, 2015). Inside the Paleogene strata, currently, are known flute-mouth fishes, sea basses, and some undetermined percomorphs (Alvarado-Ortega et al, 2015;Cantalice and Alvarado-Ortega, 2017;Cantalice et al, 2018). The body shape and the presence of three spines on the anal fin of the fossil herein described resembles the serranid Paleoserranus lakamhae; however, the anal spines of this last species are stouter, and the second anal fin spine is the biggest.…”

Peer Review #2 of "A quantitative approach to determine the taxonomic identity and ontogeny of the pycnodontiform fish Pycnodus (Neopterygii, Actinopterygii) from the Eocene of Bolca Lagerstätte, Italy (v0.1)"

“…However, the assignment of the name Pycnodus to this fish is dubious, since it lacks the post-parietal process typical of the Pycnodontidae (personal observation JJC, 2018). A more complete specimen of Pycnodus was found in the Palaeocene rocks of Palenque, Mexico (Alvarado-Ortega et al, 2015), which solely differs from the Eocene specimens from Bolca by having a greater number of ventral and post-cloacal ridge scales, less dorsal-and anal-fin pterygiophores and a large or regular-sized posteriormost neural spine.…”

“…not valid (all Jurassic and Cretaceous Pycnodus specimens being other taxa) and with the majority of Palaeogene Pycnodus being represented by isolated dentition it seems that the only definitive articulated skeletal remains attributed to the genus Pycnodus are Pycnodus apodus from the Bolca Lagerstätte and Pycnodus sp. from south-eastern Mexico (Alvarado-Ortega et al, 2015). Future studies should analyse other problematic pycnodontiform taxa such as the widely distributed Gyrodus from the Middle Jurassic to the Early Cretaceous (Kriwet & Schmitz, 2005) to investigate if intraspecific variation might partially explain the supposed diversity of species this genus contains.…”