Aptian and Albian (Early Cretaceous) ammonites from Lampazos and the Bisbee groups (Sonora State, northwest Mexico)
Résumé
A taxonomic study was carried out of 34 ammonites collected from the Agua Salada and Nogal formations (Lampazos Group) and the Mural Limestone (Bisbee Group) in the Sonora State, northwest of Mexico. Twenty-one taxa are described, with 13 being endemic of the Central Atlantic province: Puzosia (Anapuzosia) sp. juv. cf. tucuyensis, Parasilesites cf. bullatus, Beudanticeras parandieri, \textquotedblleftBeudanticeras\textquotedblright newtoni, Beudanticeras sp., Desmoceras (Pseudouhligella) cf. vetus (en=endemic), Engonoceras complicatum (en), Engonoceras stolleyi, Protengonoceras gabbi (en), Protengonoceras neolobitoides (en), \textquotedblleftEodouvilleiceras cf. adkinsi\textquotedblright (en), Huastecoceras? sp. (en), Hypacanthoplites sp., Immunitoceras immunitum (en), Immunitoceras cf. trinitensis (en), Kazanskyella minima (en), Kazanskyella spathi (en), Quitmanites ceratitosus (en), Quitmanites fosteri (en), and Quitmanites sp. (en), between them we erected one new species: Protengonoceras neolobitoides. The record of Aptian-Albian ammonites in Sonora is scarce, therefore the ammonites herein studied are valuable due to the number of endemic taxa that could be used in future biostratigraphic works. In addition, these taxa allow a revision of the stratigraphic frame: The Agua Salada Formation is now considered from late Aptian to early Albian; the Nogal Formation is confined to late Albian; the Cerro Las Conchas succession is limited to middle Albian; and the age of the Cerro La Ceja Member is late Aptian. (C) 2018 Elsevier Ltd. All rights reserved.