Maastrichtian cephalopods from Cerralvo, north‐eastern Mexico

Abstract

Sediments of the Méndez Formation near Cerralvo, north-eastern Mexico, yield an abundant and diverse Maastrichtian ammonite assemblage. A total of 23 species referred to 18 genera are described, in addition to the possible coleoid Naefia neogaeia. The assemblage is considered to be of early Maastrichtian age on the basis of ammonite occurrences and has been dated to the lower Maastrichtian biozone CF 7 by planktic foraminifera. None of the ammonite species has been reported previously from the Méndez Formation and most species are recorded from Mexico for the first time. In addition to faunal elements known from other Gulf of Mexico localities [Baculites ovatus, Nostoceras (N.) alternatum, N. (N.) colubriformis, N. (N.) rugosum, Solenoceras reesidei] the assemblage is characterized by cosmopolitan (e.g. Anagaudryceras politissimum, Desmophyllites diphylloides, Diplomoceras cylindraceum, Gaudryceras kayei, Phyllopachyceras forbesianum, and Pseudophyllites indra) and Tethyan elements [e.g. Brahmaites (Anabrahmaites) vishnu, Fresvillia constricta, Hauericeras rembda, Solenoceras texanum, Tetragonites superstes]. Some ammonite species have been known from the Indopacific region a [e.g. Fresvillia aff. F. teres, Neophylloceras (Hypophylloceras) hetonaiense, Zelandites varuna] and are clearly cold-water species. The composition of the assemblage contrasts with other Gulf of Mexico faunas which is related to bathymetry.

The Upper Campanian – lower Maastrichtian cephalopod fauna of Botellos, Nuevo León: a key to understand faunal turnover across the Campanian–Maastrichtian boundary in NE Mexico

“…The majority of specimens were collected loose from the desert pavement. All specimens are preserved as Fe-oxide internal moulds, comparable to Maastrichtian molluscan assemblages described earlier from the Méndez Formation (Ifrim et al 2004;.…”

“…A formal description of most of the Botellos taxa can be found in earlier publications on late Campanian-Maastrichtian cephalopods with similar preservation (Ifrim et al 2004;2015b; and is therefore not repeated here. Instead, the systematic palaeontology is abbreviated to a list of species and the numbers of specimens found and their occurrence, summarized in Text- fig.…”

“…Order Coleoidea Bather, 1888 Longibelus sp., (= Naefia neogaeia by Ifrim et al 2004, re-discussed by Fuchs et al 2013) Order Ammonoidea von Zittel, 1884 Ifrim et al 2004;Ifrim et al 2005;Ifrim et al 2015b) and worldwide (grey) in localities mentioned in the text. The ranges of the Botellos taxa are marked in blue, the one of the upper Campanian Saucedas assemblage in streaks.…”

“…1). An early Maastrichtian ammonite collection of 1002 specimens was reported from the south of Cerralvo by Ifrim et al (2004). With 1076 specimens, the new Botellos collection is the richest ever found in this region.…”

“…Each assemblage provided insight into faunal dynamics during isolated time slices of the late Campanian and early Maastrichtian of NE Mexico. The Upper Cretaceous of the region turned out to be a "crossroad" between major ammonite provinces (Ifrim et al 2004(Ifrim et al , 2005(Ifrim et al , 2015bStinnesbeck 2007, 2008) and regarding other marine organisms (Ifrim and Stinnesbeck 2007;Vega et al 2007;Fuchs et al 2010;Giersch et al 2011;2014).…”