The longest known rhino horn from the permafrost of Yakutia offers insights into woolly rhinoceros morphology, palaeoecology and sexual dimorphism

In this study, we examine the dimensions of the nasal horns of woolly rhinoceroses and describe the longest rhino horn known to date, which was recently discovered in the permafrost of Yakutia. The extinct woolly rhinoceros is an iconic representative of the Late Pleistocene mammoth fauna of Eurasia, characterized by two huge keratinous horns. The nasal horn is considerably longer than the frontal one; it is laterally flattened and has a saber‐like shape, which is unparalleled among modern‐day rhinoceroses. The nasal horns of adult woolly rhinoceroses range in length along the anterior curvature from 68.5 to 134 cm (101.7 cm on average). Their mass varies between 2.5 and 11.4 kg (6 kg on average). Both of these values exceed those of all extant rhinoceroses. The record‐breaking nasal horn discovered in Yakutia last year reaches 164.7 cm along the anterior curvature and weighs ~9 kg. The relatively small size of the skull in this specimen indicates that it probably belonged to a rhinoceros female. This suggests that Coelodonta antiquitatis may have had the longest horns in females, similar to modern‐day African rhinoceroses. The number of periodic transverse bands (each of which consists of two, darker and lighter, keratin zones) along the length of the horn suggests that the discovered horn belonged to the oldest known woolly rhinoceros with an individual age of ≥40 years. Thus, this discovery not only provides insights into the morphological features of woolly rhinoceroses but also offers valuable information about their palaeoecology and sexual dimorphism.