Fossil biogenic phosphate of fast-growing primary bone tissue of
dinosaurs can preserve a histologic and isotopic time-series of annual
seasonality in temperature variations, similar to tooth enamel and other
accretionary skeletal phases such as corals or wood. On two bone
fragments from sympatric dinosaurs with different histologic patterns of
bone growth, high-resolution oxygen isotope profiles were analyzed along
the radial direction of bone growth. The investigated specimens are from
the Jurassic Shishugou Formation in the Junggar Basin, NW China and have
distinct patterns of compositional variation. A fibrolamellar dinosaur
bone with multiple lines of arrested growth (LAGs) and periodic growth
cycles of decreasing bone laminae thickness displays a cyclic intra-bone
variation in delta(18)O values of about 2parts per thousand
corresponding with the LAGs. These growth cycles in fast-growing
fibrolamellar bone provide evidence for seasonal growth of dinosaurs in
lower latitudes ( similar to 45degreesN), possibly influenced by a
monsoon-type paleoclimate. Seasonal changes in temperature and water
supply are consistent with the oxygen isotope composition measured in
dinosaur bone phosphate as well as with growth rings in contemporaneous
fossil conifer wood from the same locality. In contrast, a plexiform
sympatric sauropod bone displays continuous growth, free of LAGs and has
a lower intra-bone variation of less than or equal to 0.8parts per
thousand. Differences in bone histology are also reflected in the oxygen
isotopic composition and its intra-bone variability, indicating
different physiological responses to external climatic stress between
sympatric dinosaur species. Seasonal intra-bone oxygen isotope
variations combined with bone histology may thus yield new insights into
species-specific response to climatic stress and its influence on
dinosaur growth, formation of growth marks, growth rates, as welt as
dinosaur thermophysiology. (C) 2004 Elsevier B.V All rights reserved.