Fig. 2. Dinosaur and ratite comparative views. (A) Freshly broken fragment of MOR 1125 shows laminar ELB separating CB and MB. Bone tissues decrease in density internal to the ELB, because of increased vascularity. (B) Emu tibia, midshaft section. Erosion rooms extending into ELB are secondarily filled by MB. (C) Ostrich bone, mid­ shaft. MB is distinct from CB, but no obvious ELB is visible and several large vascular sinuses are seen. (D) Higher magnification of MB region of MOR 1125, showing increased porosity and more random orientation of MB than CB or ELB. (E) Emu, stained (14) to distinguish bone from infiltrating marrow fat. MB is more vascular than overlying CB and exhibits a random, whorled pattern. (F) Ostrich MB, showing relationship of bony spicules to invading blood sinuses, colored red from remnant blood. (G) Ground section of MOR 1125. Dense cortical Haversian bone shows second- and third-generation remodeling. ELB separates Haversian bone from more vascular MB. (H) Similar orientation of emu femur shows dense CB, distinct ELB, and a thin layer of MB. (I) Ostrich MB appears more laminar than in (C) or (F) because of the longitudinal orientation of tubelike medullary spicules.