Figure 1 in Growth patterns, sexual dimorphism, and maturation modeled in Pachypleurosauria from Middle Triassic of central Europe (Diapsida: Sauropterygia)

Figure 1. Details of medulla, bone tissue, and vascularization of Dactylosaurus from the early Anisian (Lower Muschelkalk; Germanic Basin) and aff. N. pusillus from the late Ladinian (Lower Keuper; Germanic Basin). (a) Medullary region distally to midshaft in Dactylosaurus humerus MB.R. 801.2. consisting of small round erosion cavities surrounded by endosteal bone and embedded in a matrix of calcified cartilage. The medullary region is surrounded by a sharp line (arrow). (b) Medullary region closer to midshaft in Dactylosaurus humerus MB.R. 771.5 displaying a small free cavity, a few small erosion cavities surrounded by endosteal bone and calcified cartilage at the border to the periosteal region all encompassed by a sharp line (arrow). Around the medullary cavity slow-deposited (i.e., highly organized) hatchling bone tissue is visible. (c) The medullary region and inner cortex in aff. N. pusillus humerus SMNS 50372b is nearly completely filled by endosteal bone. The area is surrounded by the sharp line (arrow), although the sample was taken nearly at the midshaft. Scattered longitudinal primary osteons occur in this sample. (d) Cross section of aff. N. pusillus humerus SMNS 58025a which shows an irregular medullary region and remodeling in form of erosion cavities scattered into the periosteal bone. (e) Medullary region and inner cortex of aff. N. pusillus humerus SMNS 50372c. The medullary region consists of few small erosion cavities and endosteal bone. The innermost cortex is made of fast-deposited hatchling bone tissue, which is surrounded by a distinct annulus. (f) Medullary region and inner cortex of aff. N. pusillus humerus SMNS 92125. The medullary region consists of a small cavity surrounded by a thick layer of endosteal bone, which are encompassed by a sharp line and calcified cartilage. The innermost cortex is made of a slow-deposited hatchling bone tissue. (g) Cross section of N. pusillus humerus PIMUZ T 3975. The medullary region is completely filled by endosteal bone. The area is surrounded by some erosion cavities. (h) Medullary region and inner cortex at midshaft in Dactylosaurus humerus MB.R. 776.2 showing a free cavity surrounded by a thick layer of endosteal bone. On the right side are remains of preserved fast-deposited (i.e., less organized) hatchling bone tissue. On the right side, the layer of horizontally oriented fine fibers is visible (arrow). (i) Medullary region and inner cortex in Anarosaurus humerus Wijk 13-194. The relatively large, free medullary cavity is surrounded by a thin, and in this sample incomplete, layer of endosteal bone. The innermost cortex is made of a fast-deposited (i.e., highly organized) hatchling bone tissue, which is surrounded by a distinct annulus. A second annulus is clearly visible in the lower part of the picture. Distance between annuli changes considerably towards the preaxial bone side (arrows mark spilt). Abbreviations: cc, calcified cartilage; eb, endosteal bone; ec, erosion cavity; htb, hatchling bone tissue; ffho, fine fibers horizontally oriented; mc, medullary cavity; mr, medullary region; po, primary osteon. All pictures are in polarized light. Scale bar is 0.5 mm if not labeled otherwise.