The skull of Microtia, an extinct burrowing murine rodent of the late Neogene Gargano palaeoisland

The Neogene Gargano paleoisland (southern Italy) has yielded numerous fossil vertebrates, some of them showing extraordinary morphological peculiarities. Among these endemic species, the rodent genus Microtia Freudenthal, 1976, is represented by three main lineages that evolve toward gigantism. This genus is the most significant and abundant rodent represented in the Gargano palaeofaunas. Its evolutionary trends reveal an increase of size, accompanied by a complication of molar structure. Before carrying out a study on the Gargano rodent community, its structure and its evolution, it was necessary to characterize Microtia's ecological adaptations. Microtia was adapted to burrowing life, which appears to be a unique adaptation for a murine rodent, since European burrowing Plio-Pleistocene and extant rodents are only represented by arvicolids. Therefore, the extinction of Microtia is likely to be due to competition with arvicolids after the breakdown of isolation, since they occupied very similar ecological niches.     

High-level phylogeny of early Tertiary rodents: dental evidence

Major crown‐groups of rodents were well established in the early Tertiary, and fossils provide an invaluable window into their evolutionary history. The main focus of this project was to perform a cladistic assessment of the dental evidence for early Tertiary rodent cladogenesis – the masticatory apparatus and teeth are the most frequently preserved anatomical features in the fossil record. We focused on groups that existed in a period corresponding to their early history, combining fossils belonging to extinct lineages and to stem‐groups leading to modern lineages. While the monophyly of some groups is not systematically explored, our results have important implications for high‐level rodent relationships and systematics. These results are consistent with those of recent molecular phylogenies and reliably congruent with the stratigraphic record, thus enhancing the pertinence of dental characters for phylogenetic inference. Our approach provides evidence of a fundamental dichotomy in early rodent history. Two major clades have been identified: (1) the earliest ‘ctenodactyloid’ (Ctenodactylidae, Chapattimyidae, Yuomyidae, Diatomyidae) and hystricognathous (Tsaganomyidae, Baluchimyinae, ‘phiomorphs’, ‘caviomorphs’) rodents, and (2) the earliest ‘ischyromyoid’ rodents with their closest relatives (Muroidea + Dipodoidea + Geomyoidea + Anomaluroidea + Castoroidea + Sciuravidae + Gliroidea, and Sciuroidea + Aplodontoidea + Theridomorpha). This topology has led us to endorse Ctenohystrica as the first clade and propose a new taxon, Ischyromyiformes, for the second. Although minimized in our working hypothesis, the homoplasy in dental characters remains significant. However, a number of homoplasic characters reveal structuring in their internal distribution, allowing us to discern evolutionary morphological patterns, notably the pentalophodonty of molars, zygomasseteric complex and incisor enamel microstructure. © 2004 The Linnean Society of London, Zoological Journal of the Linnean Society, 2004, 142 , 105–134.     

The Female-specific Protein (Vitellogenic Protein) in Crustacea with Particular Reference to Orchestic gammarella (Amphipoda)

Comparative electrophoretic studies of male and female hemolymphin Crustacea have led to the discovery of a lipoglycoproteinfraction present in females and absent from males. The female-specificprotein fraction also contains a pigment which has been identifiedin a small number of species and appears to be a carotenoid.Further observations indicated that the presence of this fractionis coincident with the presence of maturing ovocytes in theovary. The major protein component of the vitellus is also alipoglycocarotenoprotein complex. Comparative analyses haveshown that the female-specific protein fraction present in hemolymphand the major protein component of the vitellus are electrophoreticallyand immunochemically identical. Moreover, in the Amphipod Orchestiagammarella both components appear to have the same molecularweight, estimated as approximately 3 x 10⁵ by Sephadex G 200gel filtration. Although there is ample evidence to supportthe idea that the female-specific protein is synthesized externallyto the ovary, the site of synthesis still remains unknown. Experimentallyinduced sex reversal in O. gammarella indicates that the synthesisof the female specific protein is under ovarian control.