The skull of Triceratops in the palaeontology gallery, Muséum national d'Histoire naturelle, Paris

The specimen of Triceratops calicornis Marsh, 1898 exhibited in the gallery of palaeontology in the Muséum national d’Histoire naturelle of Paris consists of a skull lacking the lower jaw, except for the predentary. It was presented in October 1912, when Marcellin Boule was chairman of the Palaeontology department, and registered as MNHN 1912.20. This specimen, long overlooked in the literature, is described herein for the first time. Since its erection by Marsh in 1889, up to 16 species have been referred to the genus Triceratops. However, during the last 20 years, our comprehension of the biology and variability of large living tetrapods has called into question the validity of these Triceratops species. Although a consensus on this question now seems to emerge, several models have been still discussed recently. The description of MNHN 1912.20 offers an opportunity to discuss these different hypotheses.