Bone Microvasculature Tracks Red Blood Cell Size Diminution in Triassic Mammal and Dinosaur Forerunners  Adam K. Huttenlocker, C.G. Farmer  Current Biology  Volume 27, Issue 1, Pages 48-54 (January 2017) DOI: 10.1016/j.cub.2016.10.012 Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 1 Variation in RBC and Canal Sizes in Cortical Bone of Selected Extant Tetrapods (A and B) Comparison of RBCs and femoral cortical bone tissues in an amphibian, Lithobates catesbeianus (A), and a mammal, Oryctolagus cuniculus (B) (direction of periosteum is top). See Figure S1 for detailed sampling scheme. (C) Frequency histograms of cortical canal caliber in selected extant tetrapods sampled for this study. Note that the minimum caliber in anurans and non-avian reptiles typically fell above eight microns and with broader distributions overall, whereas those of mammals and birds were confined to the left-hand portion of histospace. Separate examples are included in Figure S2. Green bars, anurans; blue bars, non-avian reptiles; indigo bars, birds; red bars, mammals. Current Biology 2017 27, 48-54DOI: (10.1016/j.cub.2016.10.012) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 2 Bar Chart Showing Bayesian Posterior Distributions for RBC Size Estimates in Fossil Tetrapods Shown are RBCwidth (gray bars) and RBCarea (black bars) in fossil non-mammalian synapsids, sauropsids, and a temnospondyl amphibian (Micropholis). Whiskers represent one standard deviation of the posterior distribution of estimates. Gray dashed line represents the observed upper RBCwidth and black dashed line the upper RBCarea for a fully terrestrial mammal in the Animal Cell Size Database (http://www.genomesize.com/cellsize/). Note that estimates for several therapsids (Cynognathus, Bienotherium, Ictidosuchoides, Diademodon, Tetracynodon, Thrinaxodon, and Trirachodon) and a silesaurid dinosauromorph fall below both of those values. See also Figure S3 and Tables S1–S4. Current Biology 2017 27, 48-54DOI: (10.1016/j.cub.2016.10.012) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 3 Optimization of Ancestral RBC Sizes on a Time-Calibrated Phylogeny of Tetrapods Cynodonts and some other non-mammalian therapsids (therocephalians) exhibit mammal-like RBC sizes by the Permian-Triassic transition. RBC sizes for fossil taxa were estimated from the multiple regression models and ancestral values reconstructed using squared-change parsimony in Mesquite v.2.75 [13]. See also Figure S3 and Table S4. All silhouettes borrowed from the open source graphics site PhyloPic (http://phylopic.org). Abbreviations are as follows: C, Carboniferous; Cz, Cenozoic; J, Jurassic; K, Cretaceous; Ng, Neogene; P, Permian; Pg, Paleogene; Tr, Triassic. Current Biology 2017 27, 48-54DOI: (10.1016/j.cub.2016.10.012) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 4 Relative Heart Mass Correlates Inversely with Cell and Nuclear Sizes in Non-sauropsid Tetrapods—Dashed Line—and Sauropsids—Solid Line (A–C) The data in (A) are from Vinogradov and Anatskaya [32], whereas (B) and (C) represent a subset of those species having published RBC diameters plus extant species sampled in the present study (see Data S1). RBCwidth, non-sauropsids: r2 = 0.713; p < 0.001; RBCwidth, sauropsids: r2 = 0.460; p < 0.001; RBCarea, non-sauropsids: r2 = 0.698; p < 0.001; RBCarea, sauropsids: r2 = 0.556; p < 0.001. Green open diamonds, amphibians; blue solid squares, non-avian reptiles; indigo solid circles, birds; red open triangles, mammals. Fossil species (black squares) fitted to the models in (C) are approximate and based on the Bayesian posterior distributions of estimated RBCarea. See also Figure S3. Abbreviations are as follows: Il, Ictidosuchoides longiceps; Ms, Micropholis stowi; Pb, Prolacerta broomi; Sf, Sphenacodon ferocior; Ssp, Silesauridae sp.; Tb, Trirachodon berryi; Td, Tetracynodon darti; Tl, Thrinaxodon liorhinus. Current Biology 2017 27, 48-54DOI: (10.1016/j.cub.2016.10.012) Copyright © 2017 Elsevier Ltd Terms and Conditions