Blau J., Meister C., Schmidt-Effing R., Villaseñor A.B. (2008) A new fossiliferous site of Lower Liassic (Upper Sinemurian) marine sediments from the southern Sierra Madre Oriental (Puebla, Mexico): ammonite fauna, biostratigraphy, and description of Ectocentrites hillebrandti new species // Revista Mexicana de Ciencias Geológicas, v. 25, núm. 3, p. 402-407.
pdf: http://satori.geociencias.unam.mx/25-3/ (03)Blau.pdf
Authors describe ammonites from a newly discovered, fossil-bearing, marine Liassic locality (Lower Jurassic, Huayacocotla Fm.) in the vicinity of the Zongozotla Municipality (southern Sierra Madre Oriental) in the northern part of Puebla State (Mexico). The fossiliferous strata are about 1 m in thickness and yield ammonites and bivalves. The ammonites are Late Sinemurian in age and they represent a biohorizon which is correlated with the Paltechioceras gr. burckhardti horizon reported from the Tenango de Doria area. Ectocentrites hillebrandti n. sp. is described.