History Plants and Animals

Pregnant T-Rex Find Connects Dinosaurs to Modern Day Birds

Tyrannosaurus rex
Tyrannosaurus rex

The discovery of a pregnant Tyrannosaurus rex is helping scientists to learn more about the gender differences in dinosaurs and how modern day birds evolved to lay eggs.

It is also being speculated that the remains could contain viable dinosaur DNA, but scientists are urging caution saying that while it is certainly possible, the public shouldn’t expect little dinosaur clones anytime soon.

They say more testing will need to be done to determine what application, if any, dinosaur DNA found in the remains may have. Preliminary testing has revealed that the T-Rex fossil which was dug up in Montana is over 68 million years old.  Upon examination it was discovered that the fossil included medullary bone, which is a type of bone found in modern-day birds, indicating they’re pregnant and about to lay eggs.

pregnant t-rex
Illustration shows a pregnant T-Rex along with another non-pregnant female. (Image Credits: MARK HALLETT)

The medullary bone is a special type of tissue which stores calcium reserves which makes it easier for birds to lay eggs. The medullary tissue means that they don’t have to draw on their regular calcium reserves in order to form their offspring’s shells. Once the eggs have been laid, the medullary bone is usually entirely used up which is why scientists are so confident that the 16-20 year old female T-Rex was in fact pregnant when she  died of unknown causes. The medullary bone was discovered after a chemical analysis was conducted on the dinosaurs femur. While medullary bone has been found in dinosaurs previously, this latest find is one of the most substantial to date. The bone in generally only present for around 4 weeks in pregnant dinosaurs making the odds of finding a dinosaur with medullar tissue incredibly small.

medullary bone
This sample of T-Rex bone shows medullary bone in the middle. (Image Credits: Schweitzer M. H/Scientific Reports)

What’s more, it is very difficult to detect without analyzing the inside of a bone and most paleontologists often aren’t prepared to cut up their dinosaur bones in order to properly test for its presence. The only reason that researchers discovered it this time was that they were testing on a femur bone which had already been broken and was therefore able to be properly analyzed. It is hoped that the find will help scientists better understand the relationship between dinosaurs and their avian descendants.

The discovery will also help scientists study the differences between male and female Tyrannosaurus rexes and better understand how their growth patterns and bone structures differed. Because a large portion of the skeleton was discovered, it’s hoped that we will soon have a clearer picture of what this particular T-Rex looked liked, how she lived and ultimately how she died.

The research has been published in the journal Nature Scientific Reports.