Researchers examining a giant femoris excavate in Montana bring out that it belong to a pregnantTyrannosaurus rexthat experience 68 million age ago . The femoris contain a gender - specific tissue paper , and it could help with sexual urge determination of fossils in the future , according to new finding print inScientific Reportsthis hebdomad . This is the first time researchers have been able to canvass a dinosaur fogy that unquestionably belonged to a female .
Birds are the living descendant of carnivorous dinosaur called bird-footed dinosaur , and many of today ’s bird metal money have a gender - specific generative tissue called the medullary osseous tissue . Only mature distaff wench have it and only right before or during egg place . While this short - lived bony tissue is typically establish in farseeing pearl ( like femurs ) , it does n’t leave much structural support . Rather , it ’s an easily mobilized source of atomic number 20 for eggshell .
Since extinct bird-footed dinosaur also lay eggs , researchers hypothesized that medullary bone would be present in those toothy predators as well . In fact , four dinosaurs have been antecedently aim to have this estrogen - qualified tissue paper – includingT. rex , base on a femur fragment make out as MOR 1125 . However , some pathologies are have it away to mimic the appearance of medullary bone even under the microscope , so a chemical diagnosing is postulate to know for sure .
Medullary pearl is chemically distinct from other case of bone such as densecortical os , which makes up the verboten layer of our bones . In birds , the bone - form cells of medullary bone have receptor on their nuclei for estrogen , so it can be rapidly deposit when estrogen degree get gamy after ovulation . Also , medullary bone does n’t have as much collagen . rather , it integrate a meaning called keratan sulfate , which is n’t found in the matrix of any other off-white character .
A squad pass byMary Schweitzerof North Carolina State University equate dinosaur tissue with that of an Struthio camelus and a chicken , and then CT scan and chemical substance tests were channel to study the difference between their medullary bone and cortical os .
Sure enough , their analysis confirm the presence of medullary ivory in the MOR 1125T. rexfemur . It seems the unique chemical composition of medullary ivory in bird was retained from their theropod root , and it may be used to identify sexual urge and reproductive status in fossils .
" It ’s a contaminating secret , but we know next to nothing about sex - linked trait in extinct dinosaurs , " study joint author Lindsay Zanno also of NC State say in astatement . " Dinosaurs were n’t diffident about intimate signaling , all those bells and whistle , horn , crests , and ruff , and yet we just have n’t had a reliable way to secernate male person from female . Just being able to place a dinosaur definitively as a female give up a whole new world of possibilities . "
