Tedesco Pablo auteur aut IRD Bigorne Rémy auteur aut IRD Bogan A. E. auteur aut IRD Giam X. auteur aut IRD Jézéquel Céline auteur aut IRD Hugueny Bernard auteur aut IRD text journalArticle eng text/pdf born digital access Because both descriptions of species and modern human-driven extinctions started around the same time (i.e., eighteenth century), a logical expectation is that a large proportion of species may have gone extinct without ever having been recorded. Despite this evident and widely recognized assumption, the loss of undescribed species has never been estimated. We quantified this loss for several taxonomic groups and regions for which undescribed species extinctions are likely to have occurred. Across a wide range of taxonomic groups, we applied known extinction rates computed from recorded species losses to assumed exponential decay in the proportion of species remaining undiscovered. Because all previous modeling attempts to project total species richness implicitly assumed that undescribed species extinctions could be neglected, we also evaluated the effect of neglecting them. Finally, because we assumed constant description and extinction probabilities, we applied our model to simulated data that did not conform to this assumption. Actual species losses were severely underestimated by considering only known species extinctions. According to our estimates, the proportion of undiscovered extinct species over all extinctions ranged from 0.15 to 0.59, depending on the taxonomic group and the region considered. This means that recent extinctions may be up to twice as large as the number recorded. When species differed in their extinction or description probabilities, our model underestimated extinctions of undescribed species by up to 20%. specialized conservation description curve diversity extinction taxonomy 020 021 28 5 1360-1370 2014 0888-8892 https://www.documentation.ird.fr/hor/fdi:010062586 10.1111/cobi.12285 0888-8892 [F B010062586] https://www.documentation.ird.fr/hor/fdi:010062586 https://www.documentation.ird.fr/intranet/publi/2014/11/010062586.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2014-12-05 2017-08-23 fdi:010062586 fre