1,721,035 research outputs found
Early evolution of body size in bats
No full textSize is the single most important factor affecting physiology, locomotion, ecology, and behavior of mammals. Understanding evolution of size is especially important in groups like bats which exhibit many unique or energetically expensive behaviors (e.g., powered flight, echolocation, torpor and hibernation, long-distance migration). In addition, bats have the most diverse array of dietary habits of any mammalian Order. Most bat species are small: the central tendency in size in extant bats, as estimated by the median value, is around 14 g. However, bat size spans three orders of magnitude, with a few species exceeding one kilogram. Variation is not evenly distributed across groups, and there is no specific hypothesis accounting for size variation in bats. In search of evolutionary patterns, we first estimated mass in key Eocene fossils via allometric relationships. Least midshaft diameter of limb bones yielded accurate models of variation in size (body mass) in extant bats at the interspecific level (error <2%), thus providing a solid basis for size estimation in fossils. We then mapped size on current bat phylogenies including Eocene fossils. On these phylogenies, mass decreased along stem chiropteran nodes until a range of 14 -17 g was achieved in the crown clade including Palaeochiropteryx and extant bats (or microbats, depending on the topology). Remarkably, this estimated range includes the median of size for extant bats and was conserved since the Early Eocene along the backbone of all major bat clades with minor variations, strongly suggesting that an efficient combination of factors, including energy expenditure and cost of transport, was achieved at the base of the crown clade and was maintained through the evolutionary history of bats. Departures from this range were reconstructed as nested within bat families and were associated with major changes in diet, particularly carnivory and frugivory.Fil: Giannini, Norberto Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Gunnell, Gregg F.. University of Duke; Estados UnidosFil: Habersetzer, Jorg. Senckenberg Research Institute; AlemaniaFil: Simmons, Nancy B.. American Museum of Natural History; Estados Unido
Fig. 4 in Fossil Evidence and the Origin of Bats
No full textFig. 4. Distribution of Eocene bats in North America. Note that the single middle Eocene taxon (Wallia) has been tentatively identified as a molossid although its true affinities remain to be determined.Published as part of Gunnell, Gregg F. & Simmons, Nancy B., 2005, Fossil Evidence and the Origin of Bats, pp. 209-246 in Journal of Mammalian Evolution 12 (1) on page 218, DOI: 10.1007/s10914-005-6945-2, http://zenodo.org/record/783765
Fig. 3 in Fossil Evidence and the Origin of Bats
No full textFig. 3. Specimen of Hassianycteris messelensis (SMF ME 1414a) from Messel Oil Shale, middle Eocene, Germany (photo courtesy of J. Habersetzer, imagine taken by E. Pantak).Published as part of Gunnell, Gregg F. & Simmons, Nancy B., 2005, Fossil Evidence and the Origin of Bats, pp. 209-246 in Journal of Mammalian Evolution 12 (1) on page 217, DOI: 10.1007/s10914-005-6945-2, http://zenodo.org/record/783765
FIGURE 4 in A New Family of Large Omnivorous Bats (Mammalia, Chiroptera) from the Late Eocene of the Fayum Depression, Egypt, with Comments on Use of the Name "Eochiroptera"
No full textFIGURE 4. Photograph of the holotype of Aegyptonycteris knightae (CGM 83740) in occlusal view. Scale = 4 mm.Published as part of Simmons, Nancy B., Seiffert, Erik R. & Gunnell, Gregg F., 2016, A New Family of Large Omnivorous Bats (Mammalia, Chiroptera) from the Late Eocene of the Fayum Depression, Egypt, with Comments on Use of the Name "Eochiroptera", pp. 1-44 in American Museum Novitates 2016 (3857) on page 11, DOI: 10.1206/3857.1, http://zenodo.org/record/536866
FIGURE 15 in Bats (Chiroptera) from Olduvai Gorge, Early Pleistocene, Bed I (Tanzania)
No full textFIGURE 15. Right distal humerus of extant Miniopterus schreibersi (NHMUK 19.7.7.2417) compared with fossil Miniopterus cf. M. schreibersi (NMT.011A/Bat) in A, anterior, B, posterior, C, medial, and D, lateral views.Published as part of Gunnell, Gregg F., Butler, Percy M., Greenwood, Marjorie & Simmons, Nancy B., 2015, Bats (Chiroptera) from Olduvai Gorge, Early Pleistocene, Bed I (Tanzania), pp. 1-35 in American Museum Novitates 2015 (3846) on page 25, DOI: 10.1206/3846.1, http://zenodo.org/record/459831
FIGURE 1 in Quaternary Bat Diversity in the Dominican Republic
No full textFIGURE 1. Flooded floor of Oleg's Bat Cave in eastern Dominican Republic, where numerous bat cranial and postcranial remains can be observed. Photograph courtesy of the Dominican Republic Speleological Society and Phillip Lehman.Published as part of Velazco, Paúl M., O'Neill, Hannah, Gunnell, Gregg F., Cooke, Siobhán B., Rimoli, Renato, Rosenberger, Alfred L. & Simmons, Nancy B., 2013, Quaternary Bat Diversity in the Dominican Republic, pp. 1-20 in American Museum Novitates 2013 (3779) on page 2, DOI: 10.1206/3779.2, http://zenodo.org/record/536440
Fig. 1. A in Fossil Evidence and the Origin of Bats
No full textFig. 1. A strict consensus of four equally parsimonious trees (791 steps each) derived from analysis of our new morphological dataset. Numbers above the branches are decay values; those below the branches are bootstrap values. In each pair of numbers, the first number represents the support value calculated using the complete dataset; the second number represents the support value calculated in an analysis including all taxa except Tanzanycteris, a relatively poorly known fossil. Most decay and bootstrap values were generally unaffected by removal of Tanzanycteris. However, support for some nodes in the middle of the tree increased markedly when Tanzanycteris was removed (i.e., for the crown group Microchiroptera the decay value increased from one to four, and the bootstrap from 37 to 76%).Published as part of Gunnell, Gregg F. & Simmons, Nancy B., 2005, Fossil Evidence and the Origin of Bats, pp. 209-246 in Journal of Mammalian Evolution 12 (1) on page 215, DOI: 10.1007/s10914-005-6945-2, http://zenodo.org/record/783765
FIGURE 6. Chiropteran humeri. A in Quaternary Bat Diversity in the Dominican Republic
No full textFIGURE 6. Chiropteran humeri. A. Mormoops blainvillei (extant, ROM 89973), B. Mormoops megalophylla (extant, AMNH 25589), C. †Mormoops magna, D. †Mormoops magna (mirror image), E. Pteronotus macleayii (mirror image), F. Brachyphylla nana (mirror image), G. Erophylla bombifrons (mirror image), H. Monophyllus redmani (mirror image), I. Phyllonycteris poeyi. Scale bar = 10 mm.Published as part of Velazco, Paúl M., O'Neill, Hannah, Gunnell, Gregg F., Cooke, Siobhán B., Rimoli, Renato, Rosenberger, Alfred L. & Simmons, Nancy B., 2013, Quaternary Bat Diversity in the Dominican Republic, pp. 1-20 in American Museum Novitates 2013 (3779) on page 14, DOI: 10.1206/3779.2, http://zenodo.org/record/536440
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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