Tyrannosaurus rex

[johnny rex]

According to the latest study on soft tissues in Tyrannosaurus fossils, onlinelibrary.wiley.com/doi/10.1111/joa.13388 Keratan sulfate as a marker for medullary bone in fossil vertebrates, the so-called "medullary bone" inside the bones of Tyrannosaurus especially MOR 1125 a.k.a B-rex may be turned out to be unrelated to eggshell formation at all.

"Implications for sex determination in extinct archosaurs

Several researchers have reflected on a set of criteria to confidently identify medullary bone and distinguish this reproductive tissue from other bone tissue types in the fossil record (see Chinsamy et al., 2016; O'Connor et al., 2018 and the recent review in Canoville et al., 2020a). However, the confident identification of this tissue in fossil specimens remains problematic. The development of definitive morphological criteria for medullary bone in extinct species is complicated by the structural variation observed within living birds (Canoville et al., 2020a; O'Connor et al., 2018), the possibility that the morphology of medullary bone varied during its early evolution (Canoville et al., 2020a) and may not be consistent with what is observed in extant birds, and the fact that medullary bone shares microstructural characteristics with certain pathological tissues (Beresford, 1981; the present study). Here we demonstrate similar challenges in medullary bone identification that result from chemical overlap with pathological tissues. In the absence of preservation or treatment biases (a particular problem for fossil materials), our results indicate that the absence of keratan sulfate can be used to reject a hypothesis of medullary bone (i.e., all medullary bone contains keratan sulfate) and conversely, that the presence of keratan sulfate is inadequate to rule out the alternative hypothesis of pathological origin for potential medullary bone tissues in fossil vertebrates (i.e., keratan sulfate is present in medullary bone and also in some pathological bone, particularly those containing chondroid bone). Confident identifications of medullary bone in fossil vertebrates currently require multiple morphological, developmental, chemical, and location-based (e.g., skeletal distribution patterns, inverse relationships with pneumaticity) criteria to amass a preponderance of evidence (e.g., Canoville et al., 2020a; Chinsamy et al., 2016; O'Connor et al., 2018). No single criterion can be used to reject a hypothesis of pathological origin for endosteal tissues in fossil vertebrates." Reply