Comparative anatomy and systematic implications of the turbinal skeleton in Lagomorpha (Mammalia)

In order to elucidate the systematic relevance of the turbinal skeleton in Lagomorpha the ethmoidal regions of 6 ochotonid, 21 leporid, and 2 outgroup species (Sciurus vulgaris, Tupaia sp.) species were investigated by high-resolution computed tomography (μCT). Number and shape of turbinals correspond to major clades and to several genera. All Lagomorpha under study have a deeply excavated nasoturbinal that is continuous with the lamina semicircularis; a feature likely to be an autapomorphy of lagomorphs. In particular, the olfactory turbinals (frontoturbinals, ethmoturbinals, and interturbinals) provide new systematic information. The plesiomorphic lagomorph pattern comprises two frontoturbinals, three ethmoturbinals, and one interturbinal between ethmoturbinal I and II. Ochotonidae are derived from the lagomorph goundplan by loss of ethmoturbinal III; an interturbinal between the two frontoturbinals is an autapomorphy of Leporidae. Pronolagus is apomorphic in having a very slender first ethmoturbinal, but shows a puzzling pattern in decreasing the number of turbinals. Pronolagus rupestris and Romerolagus diazi have independently reduced their turbinals to just two fronto- and two ethmoturbinals, which is the lowest number among the sampled lagomorphs. In contrast, the more derived leporid genera under study (Oryctolagus, Caprolagus, Sylvilagus, and Lepus) show a tendency to increase the number of turbinals, either by developing an ethmoturbinal IV (Caprolagus hispidus, Lepus arcticus) or by additional interturbinals. Intraspecific variation was investigated in Ochotona alpina, Oryctolagus cuniculus, and Lepus europaeus and is restricted to additional interturbinals in the frontoturbinal recess of the two leporids.