Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in Archaeopteryx
Figure 8
Femoral histology of the basal birds Jeholornis and Sapeornis viewed with polarized microscopy.
(A) In Jeholornis (IVPP 13353), parallel-fibered bone matrix similar to that of Archaeopteryx makes up the cortex. However porosity is greater as in Mahakala. A growth line that locally varies between a line of arrested growth and an annulus is shown (arrow). (B) In the larger Sapeornis (LPM B00166), the matrix is primarily woven-fibered and shows a mix of longitudinal and reticular vascularization. Avascular parallel-fibered bone brackets a line of arrested growth (arrow) in this sub-adult specimen. Scale bar = 0.15 mm