Soft tissues and internal skull morphology in South-American squirrels (genera Guerlinguetus, Hadrosciurus, Microsciurus and Simosciurus)

Abstract

Despite the ecological importance of the family Sciuridae, the taxonomy and systematics of several groups, particularly those inhabiting Neotropical forests, is still very controversial and lacks broad and robust revisionary studies. The Neotropical squirrels remained forgotten by systematists for a long time, and only recent efforts have been made trying to fill this large gap. Vivo and Carmignotto (2015) published a taxonomic proposal based on morphological data and recognized two species within the genus Guerlinguetus: G. aestuans and G. brasiliensis. Subsequently, Abreu-Jr et al. (2020) investigated the molecular diversity of this group and found support for the recognition of at least four putative species within Guerlinguetus. Likewise, analyses of cranio-dental morphometric data, that I conducted in my main project [Geographical variation in squirrels of the genus Guerlinguetus (Rodentia: Sciuridae) in South America], show large geographical variation within and among populations, especially from the Amazon region, supporting the hypothesis of larger diversity within this group. The results I obtained with morphometric data, however, must be explored with other sets of characters (particularly qualitative ones) in order to better elucidate the morphological geographic variation of Guerlinguetus. Therefore, in the present proposal I intend to carry out refined analyses on the morphological variation of soft tissues and internal structures of the skull of Guerlinguetus using high-resolution X-ray microtomography (CTscan). I will also examine representatives of other South-American genera in a comparative qualitative approach, aiming to find new diagnostic traits for Guerlinguetus. The application of this new technique will provide an unexplored set of morphological characteristics that might be of great relevance for future taxonomic and evolutionary studies of Neotropical squirrels. (AU)