RESULTS
RIB
Some remodeling processes in the perimedullary and medullary regions were observed, forming cancellous bone which is highlighted by trabeculae and resorption cavities (Fig. 2A, B). Cross-sections have a high level of bone compactness (0.89) with the cortical thickness of approximately 0.9 mm. The cortex is composed of parallel-fibered bone tissue interrupted by four single lines of arrested growth (LAGs) and one double LAG (Fig. 2B). These growth marks become closely spaced toward the periosteal margin(Fig. 2C, E) and these lines divide the cortex into five distinct growth zones, the third being the largest (Fig. 2E). The periosteal cortex shows simple vascular canals and primary osteons, but scattered secondary osteons are also present (Fig. 2D).
HUMERUS
The medullary cavity was infilled with iron oxides during the fossil diagenetic processes (Fig. 3A), also as this bone is fragmented compactness (0.58) must be underrated. Most of the endosteal region shows primary bone with no trace of remodeling (Fig. 3D). The primary bone (cortical thickness approximately 5 mm) appears to be a combination of lamellar and parallel-fibered bone tissue (Fig. 3B). The parallel-fibered bone tissue is highly vascularized and shows longitudinally oriented primary osteons and primary reticular canals branch up to the external bone surface (Fig. 3E).
In the mid-cortex, at least three LAGs are observed (Fig. 3F). The osteocyte lacunae exhibit either flat or globular shapes that are randomly spread out. Towards the outer margin, some Sharpey’s fibers and four LAGs are visible in the outer cortex (Fig. 3C).
ULNA
The ulna contains iron oxides and some cracks derived from taphonomic processes (Fig. 4A). Bone remodeling is visible in the endosteal layer (Fig. 4B, C) and the cortical thickness is approximately 4 mm with a bone compactness of 0.88. This cortex exhibits a poorly organized parallel-fibered arrangement and contains at least five LAGs and the woven bone matrix is visible in some portions (Fig. 4D, E). The vascularization pattern is composed of longitudinally-oriented vascular canals (Fig. 4D) which become radially-oriented toward the external bone surface (Fig. 4E). In the lamellar matrix osteocyte lacunae have a flat aspect distributed in concentric rows.
RADIUS
Remarkably this radius, found in articulation with the previously described humerus and ulna, exhibited a sharply different pattern in bone microstructure. Medullary cavity in the radius is infilled with spongy bone (Fig. 5A) and the cancellous bone is composed of resorption cavities surrounded by thin lamellar bone tissue (Fig. 5B). In the endosteal region, compacted coarse cancellous bone (CCCB) is constituted of sinuous convolutions of lamellae (Fig. 5C). A scalloped and conspicuous resorption line marks the boundary between the compacted coarse cancellous bone and the periosteal cortex (cortical thickness approximately 1 mm; bone compactness is 0.87) (Fig. 5B). The primary lamellar bone tissue is poorly vascularized and growth marks are featured by five LAGs and one double LAG (Fig. 5B, E). Parts of mid-cortex are comprised of woven bone tissue (Fig. 5F). This bone contains flattened and scarce osteocyte lacunae that follow the orientation of collagen fibers.
Publication Date: 2022-05-05