Mammals, Biodiversity of New Discoveries and Descriptions 703 Mammals may be exceptionally well described, as compared with other taxa, but this does not mean that the taxonomy of Mammalia is either complete, or stagnant In the decade 1992–2003, more than 340 new mammal species were described, with many of these being the result of taxonomic revision These are not minor revisions, with 28 of these species belonging to new Genera, and one of them a new, monotypic family Increasingly sophisticated molecular tools, as well as a better understanding of processes of phylogentic divergence, suggest that this pattern of increasing mammalian diversity will continue, and perhaps in the near term accelerate, as Families are revised and new molecular tools applied Most of these species are found in the species-rich tropics, and appear to have a restricted range size (42 m) open-water marine mammals suggests perhaps that 47 species await formal scientific description, that we should continue finding species at a rate of one new species every years, and that we are most likely to find new cetaceans Given the long and intensive history of commercial whaling, such a finding is surprising New species can be named in one of several ways In some cases, specimens collected many decades earlier were neither properly examined nor adequately described Hence, when a systematist revises a taxon, ‘new’ species may be found sitting in a museum drawer Similarly, new forms of evidence from field, laboratory, or genetic studies may force a revision of a species group Molecular genetics has played a large role in this field, forcing scientists to reassess previously assigned taxonomic names Finally, previously unknown forms may be found in nature Patterns of Discovery The Annamites: The Last Frontier for Large Mammals The discovery of a new mammal, even a large mammal, is not such an unusual event In the past 60 years, more than dozen species of large mammals have been described and several others are known but await formal description Mammals in general follow a rate of about 25 new descriptions per year Consideration of the pattern of description of new species of mammals shows that the curve is more or less bell shaped (Figure 3), with the peak of activity in describing mammals coming early in the twentieth century While new mammals continue to be discovered each year, the rate at which these discoveries have occurred has not changed significantly in recent decades If finding new species is not a particularly rare event, can we predict how many species will eventually be discovered? Recent analysis of the discovery and description of large The Annamite mountain range, which forms the border between the Lao People’s Democratic Republic and Vietnam, has yielded a large number of discoveries of new species and rediscoveries of previously described species of large mammals in the past decade The Vietnamese warty pig, Sus bucculentus, long thought to be extinct, was found in a food market in Laos in the early 1990s The field has been particularly rich for discovery of barking deer, primitive deer found throughout the tropics of southern Asia and Southeast Asia In 1994, the giant muntjac was discovered in the forests of the Annamites Large in size and with unusual antlers, the species was thought sufficiently morphologically distinct to deserve its own genus, Megamuntiacus DNA analysis suggested that the species belongs with other muntjacs in the genus Muntiacus (Muntiacus vuquangensis) and not in a genus of its own 5000 # species described 400 1000 300 200 Cumulative # of species 500 100 1800 1850 1900 1950 2000 Year Figure The number of new species described (left-hand scale, histogram) and cumulative number of mammal species (right-hand scale, line) Reproduced from Wilson DE and Reeder DM (1999) Mammal Species of the World, 2nd edn Washington, DC: Smithsonian Institution Press, with permission from Nature