Jain S. (2008) Integrated Jurassic biostratigraphy: A closer look at nannofossil and ammonite evidences from the Indian subcontinent // Current Science. Vol.95. no.3. P.326-331. Pdf http://www.ias.ac.in/currsci/aug102008/326.pdf
Old and outdated use of ammonite and nannofossil literature indicates that nannofossils are better in defining the Bathonian–Callovian boundary in the Jurassic sediments of Jaisalmer basin, western India. However, globally and with an updated biozonation from more recent literature, it is the other way round. This paradox is an example where standardization is urgently needed. In light of new nannofossil data, age assignments based on nannofossil records are critically assessed and a globally updated composite Bajocian–Callovian biozonation of ammonites and marker nannofossil species is given to encourage use of more updated literature. Some ammonites are figured: fig.3, 1–3. Macrocephalites formosus (Sowerby) [M], 4. Macrocephalites cf. madagascariensis (Sowerby) [M], 5, 6. Macrocephalites triangularis Spath [M], 7,9. Macrocephalites lamellosus (Waagen) [m], 8. Sivajiceras congener (Waagen) [M], 10. Macrocephalites cf. subcompressus (Waagen) [m].
