Abstract
Lagomorphs (a group that consists of pikas, hares, rabbits and allies) are notable for their conservative morphology retained for most of their over 50 million years evolutionary history. On the other hand, their remarkable morphological uniformity partly stems from a considerable number of homoplasies in cranial and dental structures that hamper phylogenetic analyses. The premolar foramen, an opening in the palate of lagomorphs, has been characterized as an important synapomorphy of one clade, Ochotonidae (pikas). Within Lagomorpha, however, its phylogenetic distribution is much wider, the foramen being present not only in all ochotonids but also in leporids and stem taxa; its morphology and incidence also varies considerably across the order, even intraspecifically. In this study, we provide a broad survey of the taxonomic distribution of the premolar foramen in extant and fossil Lagomorpha and describe in detail the morphological variation of this character within the group. Micro-computed tomography was used to examine the hard palate and infraorbital groove morphology in Poelagus (Leporidae) and Ochotona. Scans revealed the course and contacts of the canal behind the premolar foramen and structural differences between the two crown clades. We propose that the premolar foramen has evolved independently in several lineages of Lagomorpha, and we discuss development and function of this foramen in the lagomorph skull. This study shows the importance of comprehensive studies on phylogenetically informative non-dental characters in Lagomorpha.
Highlights
Lagomorpha is a mammalian order [1] and clade [2] known from the Eocene to Recent of Asia and North America, the Oligocene to Recent of Europe, the Miocene to Recent of Africa and the Pliocene to Recent of South America [1]
There is no cranial material of Arnebolagus, Gripholagomys, Hypsimylus, and Tachylagus, Albertona, Bellatonoides, Marcuinomys and Paludotona, or Aluralagus, Aztlanolagus, Paranotolagus and Pronotolagus for us to make any inference on the premolar foramen
The premolar foramen should not be mistaken for the palatine foramina (Figs. 2, 3, 4), which mainly occur more distally, either at the maxillopalatine suture (Figs. 3, 4A, B, D) or within the palatine portion (Figs. 1, 4C) of the hard palate [15,30] and are known in most of crown mammalian clades
Summary
Lagomorpha is a mammalian order [1] and clade [2] known from the Eocene to Recent of Asia and North America, the Oligocene to Recent of Europe, the Miocene to Recent of Africa and the Pliocene to Recent of South America [1]. Lagomorphs are generally considered to be the sister clade to Rodentia in the cohort Glires and originated in Asia, where their earliest fossil representatives are known from the Early Eocene of China [3], India [4], Kyrgyzstan [5] and Mongolia [6]. The status of the premolar foramen as an ochotonid synapomorphy is put in doubt by its presence in some species of Desmatolagus [16] Some authors assigned this speciose and diverse genus to the Ochotonidae [1,7,17], while others placed it in the Leporidae [16,18,19,20]. We consider Desmatolagus a stem group that is most probably paraphyletic
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
