Emmanuel Robert

Proposition d’une nouvelle biozonation par ammonites de l’Albien du Bassin andin (Pérou)

Proposition for a new ammonite biochronology of the Albian series of the Andean Basin (Peru). The study of the ammonite fauna of the Albian formations allows a major revision of its biostratigraphic frame in northern and central Peru. A carving in ammonite biozones is proposed for the Inca, Chulec and Pariatambo Formations and the Pulluicana group. The Lower Albian is represented by the Nicholsoni Biozone (subdivided into the umbilicostatus, and nicholsoni biohorizons, followed by an interval subzone) and by the Raimondii Biozone (carved in three subzones: Haasi, Raimondii - itself subdivided into the ebrayi and alternum biohorizons - and Mathewsi, including the pseudolyelli biohorizon). The Middle Albian is characterised by the Carbonarium Biozone, carved in the Ulrichi and Carbonarium Subzones. The base of Upper Albian is represented by the Cristatum Subzone. To cite this article: E. Robert et al., C. R. Palevol 1 (2002) 267-275.

ALBIAN AMMONITE FAUNAS FROM PERU: THE GENUS NEODESHAYESITES CASEY, 1964

Our understanding of the Cretaceous ammonite succession of Peru is mainly based on the reference work of Benavides Caceres (1956) that updates the descriptive paleontological papers by Gabb (1877), Sommermeier (1910), and Knechtel et al. (1947), among others. New fossil collections made in the course 1995 and 1999 in northern and central Peru provide the basis for a revision of the Albian ammonite faunas of this country. In contrast to our predecessors, our collections are based on sections that have been sampled bed by bed. The present study concentrates on the Early Albian ammonites from the Inca Formation of northern Peru. These forms were previously described as Parahoplites nicholsoni Benavides Caceres, 1956, P. inti Benavides Caceres, 1956, and P. quilla Benavides Caceres, 1956. Comparison of the Peruvian specimens with material from Colombia has convinced us that these taxa should be placed in Neodeshayesites Casey, 1964. As interpreted herein, Neodeshayesites is a representative of Acanthohoplitinae that also includes species from Texas previously assigned to Hypacanthoplites Spath, 1923 and Parahoplites Anthula, 1899 (Scott, 1940; Young, 1974). The paleogeographic distribution of the genus is restricted to the New World and includes Colombia, Venezuela, Texas, and Peru. The newly collected Neodeshayesites come from the Banos del Inca and Tamberia Oeste sections in the department of Cajamarca in northern Peru. The first section is situated north of Banos del Inca, 10 km east of the city of Cajamarca, in the direction of Quebrada Otuzco. The second lies northwest of Algodon, near the Hacienda Tamberia, 20 km west of Aguas Calientes and near the junction of the Cajamarca and Crisnejas rivers (Fig. 1). Figure 1 —Map of geographic positions of the Banos del Inca and Tamberia Oeste localities. Details extracted from the 1/250,000 Topographic Map of …

New insights on the genus Prolyelliceras SPATH, 1930 and the identity of Acanthoceras gevreyi JACOB, 1907 (Cephalopoda, Ammonitina)

Acanthoceras gevreyi JACOB, 1907 originates from a condensed Albian horizon at La Perte du Rhone, Bellegarde (Ain, France). This species is still very poorly known and its taxonomic interpretation in the literature is most often erroneous. New and abundant material from SE France, North Africa and South America allows the revision of this taxon and shows that Lyelliceras flandrini DUBOURDIEU, 1953, is one of its minor subjective synonyms. As a consequence the systematic position, stratigraphic range and palaeobiogeographic distribution of Acanthoceras gevreyi JACOB are discussed. Prolyelliceratidae fam. nov. is proposed.