Decapod crustaceans from the Mesozoic of Madagascar have been studied by a number of authors during the last century. One of the largest sets of specimens was collected by the French General Maurice Collignon between 1930 and 1950; this was subsequently studied by Secretan (1964) who described numerous species of macrurans, brachyurans, and axiideans. These crustaceans originate from the Upper Jurassic and the Upper Cretaceous of the Mahajanga Basin (NW Madagascar) and, especially, from the Morondava Basin (central-SW Madagascar). The purpose of the present study is twofold: to furnish an update of the stratigraphy and geology of the studied areas and, above all, to revise the Secretan's species, employing current systematic nomenclature, supplying for each detailed geographic and stratigraphic data since such were either cursory or incomplete in previous papers. The present revision considers 13 species recorded by Secretan as valid, namely: Enoploclytia collignoni Secretan, 1964, Eryma granuliferum Secretan, 1964, Pustulina spinulata (Secretan, 1964) (all Erymidae Van Straelen, 1925); Hoploparia collignoni (Van Straelen, 1949), H. c Secretan, 1964 (both Nephropidae Dana, 1852 sensu Tshudy & Babcock 1997); Ctenocheles madagascariensis Secretan, 1964 (Ctenochelidae Manning & Felder, 1991); Schlueteria menabensis Secretan, 1964 (Axiidae Huxley, 1879); Linuparus bererensis Secretan, 1964 (Palinuridae Latreille, 1802); Dromiopsis pulchella Secretan, 1964 (Dynomenidae Ortmann, 1892); Caloxanthus simplex (Secretan, 1964) (Etyidae Guinot & Tavares, 2001); "Xanthosia" robertsi Secretan, 1982 (nomen novum pro Xanthosia elegans Secretan, 1964, non Roberts, 1962), Titanocarcinus mamillatus Secretan, 1964 (both Xanthoidea incertae sedis); and Secretanella arcuata (Secretan, 1964) (indeterminate family). The three species described by Secretan (1964) as belonging to the raninid genus Notopocorystes McCoy, 1849, N bituberculatus, N australis and N. denisae will be revised in a forthcoming paper. Our comparative studies have also revealed a number of synonymous taxa, as follows: Eryma granuliferum Secretan, 1964 (junior synonym: E. madagascariensis Secretan, 1964); Linuparus bererensis Secretan, 1964 (junior synonym: L. bererensis multispinosus Secretan, 1964); Hoploparia collignoni (Van Straelen, 1949) (junior synonym: H. intermedia Secretan, 1964 and H. sculpta Secretan, 1964); Schlueteria menabensis Secretan, 1964 (junior synonym: S. tuberculosa Secretan, 1964). Lastly, we have doubts about the systematic validity of Enoploclytia armata Secretan, 1964, Eryma australe (Secretan, 1964), and Coleia incerta Secretan, 1964, because of the absence of main diagnostic features, useful for their systematic ascription.
