Fig. 1
From: Fossilization transforms vertebrate hard tissue proteins into N-heterocyclic polymers
Decalcified vertebrate hard tissues (representing a total of 7 specimens). a Paleonisciform ganoid scale (Oxfordian (Jurassic), Xinjiang, China) showing articulated blood vessels (abv) of the dentine and organic matrix with peripheral aligned and ordered (otpn), or unordered (utnp), tubular nerve projections. The left scale bar equals 500 μm, the right one 250 μm. b Blood vessel (bv) fragments from a diplodocid sauropod (Jurassic, Wyoming, US). The basal lamina (bslm) shows original stratification even though the vascular wall is thickened compared to modern archosaur blood vessels. Osteocytes (oc) with dense filipodia (f) are embedded in the originally collagenous extracellular matrix (ecm). Osteocytes adjacent to the blood vessel preserve cellular detail, but elsewhere they have degraded leaving the osteocyte lacunae (ocl) in the organic matrix. The left scale bar equals 100 μm, the right one 25 μm. c Extracellular matrix from an Allosaurus fragilis vertebra (Late Jurassic, Wyoming, US). The originally collagenous matrix fibers are preserved, and osteocytes with filipodia are dark and infilled. The scale bar equals 25 μm. d Extracellular matrix from an Apatosaurus sp. bone (Late Jurassic). Osteocyte lacunae are preserved. Decalcified avian and non-avian dinosaur eggshells. The scale bar equals 25 μm. e (Left) Rhea (modern, in captivity, Montana, US), artificially matured spongy layer. The maturation gradient increases to the right of the image. The original spongy layer is green due to pigmentation, while the matured part is brown. The scale bar equals 500 μm. (Center) Psammornis rothschildi (Holocene, Algeria), degraded spongy layer fragments. The scale bar equals 25 μm. (Right) Oviraptorid Heyuannia huangi (Late Cretaceous, Jiangxi, China) spongy layer. The scale bar equals 25 μm
