UV Autofluorescence Microscopy of Dinosaur Bone Reveals Encapsulation of Blood Clots within Vessel Canals
Mark H. Armitage* and Jim Solliday DSTRI, Inc., 325 East Washington Street #170, Sequim, WA 98382
*
micromark@juno.com
Abstract: Remarkable discoveries such as condensed chromatin in duckbill dinosaur cartilage and newly presented discoveries of dinosaur vascular veins, venule valves, and nerve fibers (this report) warrant study of global dinosaur remains for preserved soft tissue (dST). Dinosaur osteocytes feature dendritic projections (filipodia) of lengths up to 18 µm, while osteocytes collected from a Triceratops horn have lengths of 25 µm or longer. While preservation methods for dST involve the degradation of sugars into glycation end products and the employment of highly oxidative hydroxyl radicals to “fix” tissues, we note that lengthy and narrow osteocyte filipodia show no signs of hydroxyl radical infiltration into the lacuna-canalicular network. More- over, our ultraviolet fluorescence (UVFL) study of Triceratops horn, rib, vertebra, and frill thin sections shows extensive clotting in most vessel canals, probably as a result of asphyxia while drowning. Further UVFL autofluorescence study of dinosaur bone sections is vital for charac- terization of dinosaur blood clots.
Keywords: dinosaur, soft autofluorescence
Introduction Dinosaur
tissue, blood clots, tissue preservation, Microscopic venous valves (Figures 1–3) in humans reveal exceptionally preserved dinosaur
remains, especially fossil bone, continue to soſt tissues (dST)
including endogenous osteocytes, chondrocytes, intact vessels, collagen, and other soſt tissues that have been widely reported from dinosaur compact bone fossils [1–8]. Recently, condensed chromatin within chondrocyte nuclei undergoing chondrop- tosis-mimicking cellular metaphase was reported from duck- bill dinosaur fossil material recovered in the late 1980s at the Two Medicine Formation in Montana [3]. Another study of 19 museum bone specimens,
including 15 dinosaur bones,
selected from the paleontology collection at the University of Alberta, showed that all specimens yielded soſt tissues [9]. Tese striking discoveries, from specimens collected decades ago (3 in the case of the condensed chromatin specimen) pro- vide strong justification for ongoing examination of dinosaur bones for dST. Dinosaur blood vessels have been described and analyzed
at length [5–7,10,11], but dinosaurian veins, with character- istic venous valves, have not been reported. It would not be surprising to find veins and venous valves along with dino- saur osteocytes, blood vessels, and even intact nerves, post decalcification. Here we present new findings of these novel dinosaur soſt tissue structures; venous valves, veins, and nerve fibers, from Triceratops horridus bone specimens (HCTH-02, 03, horn, HCTR-11 rib, and HCTV-22 vertebra) collected pre- viously [1] (Figures 1–6). Tese tissue elements were liberated simultaneously and are shown here, suggesting that dinosaur neurovascular bundles travel as a triad of veins, vessels, and nerve fibers, as in other vertebrates [12].
30 doi:10.1017/S1551929520001340
are well characterized in the literature [13–16]. Tey ensure that blood flow continues to move forward (with each heart pulse) as blood flows to the heart. Valves in human dermis are 25 µm or less in diameter, and the thin leaflets (cuspids) that make up the (usually) bicuspid valves are typically 1 µm thick [15]. Transmission electron microscopy (TEM) has shown that valve leaflets are delicate membranes of connective tis- sue (elastin and collagen) with layers of endothelial cells lin- ing each leaflet. Tese thin cuspids of venule valves prevent backflow, therefore it is reasonable to expect that postmortem blood would be held in direct contact with venule valves for extended periods of time aſter death. Pooling at such sites via gravitational settling into dependent or lower portions of the body begins within 20 minutes of death and is characterized by clotting and permanence aſter 7 hours [17]. Blood might also pool in place in the veins and vessels of bone. Over time, if blood cells lyse, iron is freed from the hemoglobin and gen- erates copious amounts of hydroxyl radicals, which would be expected to damage ultrathin valve cuspids (see Soſt Tis- sue Preservation Methods below). We observed no damage to cuspids in this study; in fact, we observed standing vein valves that retained aqueous solutions via closed cuspids that trapped bacteria (unpublished data). Veins were usually flattened and delicate, averaging
20–55 µm in diameter (Figure 4). Although clumps of very small veins that autofluoresced brightly under blue light were observed, most veins were elongated and flattened. Vein branching patterns and branching angles were observable even though the three-dimensional conformation of these elements was flattened by liberation from the bone. Nerves recovered from T. horridus (HCTV-22, Figures
5–6) exhibited birefringence in polarized light [18,19]. Polar- ized light examination of extant vertebrate nerves reveals an undulating or zig-zagging sub-structure called “Bands of Fontana,” a feature characteristic of vertebrate nerves [18,20]. Tese white bands are also seen in the dinosaur nerve fiber on the right side of Figure 6 (arrows).
Dinosaur Bone Cells Dinosaur osteocytes have been broadly reported, whether
liberated into solution or observed on surfaces of partially decalcified compact bone, as being anchored by distinctive filipodia, which are the long dendritic processes characteris- tic of bone cells [1,2,5–9,11,21,22]. Most bone cells reside in crystalline bone matrix where they are trapped during early bone growth and remodeling. Tey create a broad arrange- ment of three-dimensional connections via the extension of
www.microscopy-today.com • 2020 September
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