Specimens of Tyrannosaurus and colleagues announced the recovery of soft tissue from the marrow cavity of a fossilized leg bone (a 1.15 m long femur), from a 68-million-year-old "Tyrannosaurus". The bone had been intentionally, though reluctantly, broken for shipping and then not preserved in the normal manner, specifically because Schweitzer was hoping to test it for soft tissue. Designated MOR 1125 (and known informally as B-rex), the dinosaur had been excavated from the Hell Creek Formation. Flexible, bifurcating blood vessels and fibrous but elastic bone matrix tissue were recognized. In addition, microstructures resembling blood cells were found inside the matrix and vessels. The
Connective tissue blood vessels and in certain ligaments, particularly in the ligamenta flava. In hematopoietic and lymphatic tissues, reticular fibers made by reticular cells provide the stroma—or structural support—for the parenchyma—or functional part—of the organ. Mesenchyme is a type of connective tissue found in developing organs of embryos that is capable of differentiation into all types of mature connective tissue. Another type of relatively undifferentiated connective tissue is mucous connective tissue, found inside the umbilical cord. Various types of specialized tissues and cells are classified under the spectrum of connective tissue, and are as diverse as brown and white adipose tissue, blood,