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. 2009 Oct 9;4(10):e7390. doi: 10.1371/journal.pone.0007390

Figure 1. Long bone histology of a non-avialan dinosaur and a Mesozoic bird viewed with polarized microscopy.

Figure 1

(A) The femoral microstructure of the small alvarezsaurrid, Shuvuuia deserti (IGM 100–99) is compared to the tibial histology (B) of the Early Cretaceous avialan, Confuciusornis sanctus (IVPP V11521). Both show well-vascularized bone owing to the presence of numerous primary vascular canals (large black structures), and woven fibered matrix characterized by oblong, randomly oriented osteocyte lacunae (numerous small black structures). Arrows point to growth lines in the form of a line of arrested growth (left) and an annulus (right). Scale bars  = 0.5 mm (A) and 0.1 mm (B).