Theropod osteohistology.

<p>Diaphyseal sections of high-latitude and lower-latitude theropods. Scale bars, 500 µm. A) Theropod femur diaphyseal section from Victoria (NMV 186323). Note the well-vascularized cortex consisting of rapidly deposited tissue. B) <i>Troodon</i> tibia (MOR 563) from Montana, USA, showing a similarly well-vascularized cortex and rapidly deposited tissue.</p

Data for Australian polar dinosaur fossils included in this study.

<p>Estimates of length indicated by asterisk. NMV: Museum Victoria, Melbourne, Victoria, Australia.</p

Hypsilophodontid ontogenetic bone microstructure.

<p>The bone microstructures observed in hypsilophodontids from Victoria (left column) suggest ontogenetic status, and strongly resemble microstructures observed in hypsilophodontids from lower latitudes (right column; Museum of the Rockies- MOR; Brigham Young University- BYU). Arrows indicate LAGs. Scale bars, 500 µm. A) Femur (NMV 216768) diaphyseal section from a skeletally immature polar hypsilophodontid. Growth marks are absent and tissue consists of rapidly deposited, disorganized woven fibers. This resembles the femoral diaphyseal section in B), from an <i>Orodromeus</i> (MOR 407). C) Diaphyseal section of a femur (NMV 208495) showing one LAG within fast growing woven tissue. LAGs within woven tissue are also observed in D), a femur from a <i>Dryosaurus</i> (BYU 13312). E) Diaphyseal section of a tibia (NMV 228434) consisting of three well-defined LAGs within loosely parallel-fibered cortex, representing a slowly growing individual approaching skeletal maturity. A similar microstructural pattern is observed in F), an <i>Orodromeus</i> tibia (MOR 973) possessing LAGs within a parallel-fibered matrix.</p

Supplementary Figures and Tables

Supplementary Figures 1-3 and Supplementary Tables 1-7

Comparison of the LH PV18 fish centrum (D) to an ellimmichthyiform centrum (A–C) (Horseshoeichthyes) from the Dinosaur Park Formation (Campanian) of Alberta.

<p>The notochordal foramen (NF) in the LH PV18 fish centrum (<b>D</b>) is so small that it cannot be seen from the angle of the photograph. The exact number and positions of mid-dorsal fossae (MDF) and laterodorsal fossae (LDF) are variable within the same taxon <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021376#pone.0021376-Brinkman1" target="_blank">[23]</a>. Photos (<b>A–C</b>) have been rotated to align with the general orientation of the obliquely figured LH PV18 fish centrum. Picture (<b>A</b>) was also flipped horizontally to simulate the right lateral view. Additional abbreviations: NA: neural arch articular pit. (<b>A–C</b>) adapted from Newbrey et al. (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021376#pone.0021376-Newbrey1" target="_blank">[22]</a>, Figure 9h). (<b>D</b>) adapted from Sereno et al. (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0021376#pone.0021376-Sereno1" target="_blank">[14]</a>, Figure S8B).</p