1.Dinosaurs had vascularized bones very similar to bird bone structure and unlike ectothermic reptilian bone
Horner teamed up with Armand de Ricqles in an effort to investigate bone structure as a means to differentiate among endotherms and ectotherms (Morell 1987: pg11). The two scientists did studies that analyzed differences in bone structure during the growth series of a dinosaur, from embryo to adult. Through comparative anatomical studies of micro-thin sections of bone from dinosaurs, modern birds, and reptiles, the men found that both the dinosaur bones and the modern bird bones contained vascular canals within the bone, for blood vessels. This evidence suggested that there is a very significant similarity among bird and dinosaur bone, which indicated that dinosaurs had fast-growing bone. According to Horner, rapid growth and vascular bone development are characteristics of endothermic animals. Cold-blooded reptiles are marked with "arrest lines", which exhibit slow growing bone that lacks the many vascular canals (Morell 1987: pg11).
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