20 Francs Mamenchisaurus

The Mamenchisaurus is a sauropod genus known almost entirely from Chinese fossil sites, with some specimens preserving necks that account for more than half the animal's total body length — among the longest cervical proportions of any known vertebrate. The Democratic Republic of the Congo has issued a sustained run of natural history-themed silver pieces under its numismatic program, which operates essentially as a revenue-generating export product; circulation within the DRC itself is negligible.