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. 2014 Feb 27;9(2):e89165. doi: 10.1371/journal.pone.0089165

Figure 15. Aenigmastropheus parringtoni, an early archosauromorph from the middle Late Permian of Tanzania.

Figure 15

Paleohistological slices of possible left humerus (UMZC T836, holotype). Overview of the bone section in normal light (A) and cross-polarized light with lambda compensator (B); upper left quadrant showing the complete section of the cortex, in which the medullary cavity is to the lower right of the image, in normal (C) and cross-polarized light (D); lower left quadrant showing the complete section of the cortex in cross-polarized light with lambda compensator (E); and close-up of the outer part of the periosteal cortex in cross-polarized light with lambda compensator (F). White arrows in (F) indicate lines of arrested growth (LAGs). Abbreviations: lpo, longitudinal primary osteons; lzb, lamellar-zonal bone; mc, medullary cavity; pfb, parallel-fibred bone; po, primary osteons; pvc, primary vascular canal; rpo, reticular primary osteons; so, secondary osteons; tb, trabecular bone; wb, woven bone.