New partial skeletons of Palaeocene Nyctitheriidae and evaluation of proposed euarchontan affinities

Small-bodied, insectivorous Nyctitheriidae are known in the Palaeogene fossil record almost exclusively from teeth and fragmentary jaws and have been referred to Eulipotyphla (shrews, moles and hedgehogs) based on dental similarities. By contrast, isolated postcrania attributed to the group suggest arboreality and a relationship to Euarchonta (primates, treeshrews and colugos). Cretaceous–Palaeocene adapisoriculid insectivores have also been proposed as early euarchontans based on postcranial similarities. We describe the first known dentally associated nyctitheriid auditory regions and postcrania, and use them to test the proposed relationship to Euarchonta with cladistic analyses of 415 dental, cranial and postcranial characteristics scored for 92 fossil and extant mammalian taxa. Although nyctitheriid postcrania share similarities with euarchontans likely related to arboreality, results of cladistic analyses suggest that nyctitheriids are closely related to Eulipotyphla. Adapisoriculidae is found to be outside of crown Placentalia. These results suggest that similarities in postcranial morphology among nyctitheriids, adapisoriculids and euarchontans represent separate instances of convergence or primitive retention of climbing capabilities.     

First mammal of Gondwanan lineage in the early Eocene of India

Based on well-preserved lower dentition, a new adapisoriculid from the Cambay Shale Formation (basal Eocene, ～54.5 Ma) in the open cast lignite mine of Vastan, Gujarat State, western India, is described. Indolestes kalamensis gen. et sp. nov adds significantly to the diversity of basal eutherians from Vastan as it represents a family hitherto not known from the Eocene of the Indian Subcontinent. Phylogenetic analysis suggests that Indolestes is derived relative to Deccanolestes and Afrodon, but primitive relative to the European adapisoriculids Bustylus and Adapisoriculus. The new data from the early Eocene provide evidence for continued survival of a Gondwanan mammal lineage following the Deccan volcanic activity (Cretaceous–Paleogene transition) in the Indian Subcontinent.