Just a Thought

Hey there every peoples!

Just wanted to chime in on some random thought i have had as i sit here looking up random stuff. As you may or may not know, in the last 20 years there has been an explosion in specimens of Tyrannosaurus rex. One of the most famous of these specimens is Jane. Jane was discovered by the Burpee Museum in the Hellcreek formation of Montana. She helped launch the Burpee Museum to stardom and launch their now blossoming paleontology program ( that such a small museum could have such success has been a big inspiration for me). Jane is important because she is a juvenile. Standing 7.5 feet at the hips, stretching 20 feet long, and weighing 1500 pounds, she would have been quite the bully at the playground. Estimated to be 11 years old, she is an important part in our understanding of T. rex growth.

Cast of Jane's skeleton at the Cleveland Museum of Natural History, Ohio (photo from flickr user statePaige)

But wait a minute. We have all heard this stuff time and time again. You’re probably wondering why I’m babbling about her. Well the answer has to do with another T. rex. His name is Thomas. Like Jane he was discovered in the badlands of Montana but by the Natural History Museum of  Los Angeles County. Thomas is a juvenile like Jane but estimated to be 13 years old. Thomas is set to appear as part of a T. rex growth series in the LA Museum’s new Dinosaur Mysteries hall which opens next year. He was quite hefty for a teenager standing 10 feet at the hips, 30 feet from nose to tail, and weighing in at 8,000 pounds.

Reconstruction of Thomas' skeleton with body outline

That’s all well and good, but what do these two have to do with each other and why are they getting a post? Here’s a hint: look at their sizes. It strikes me as odd that these two members of the same species who are only a couple years have such a huge gap in their size. Now I have often read that T. rex went through a freakish growth spurt when growing up: almost 5 pounds a day! Now if Jane was growing at that rate, she would have weighed 5,150 pounds when she reached Thomas’ age. That’s more than half of Thomas’ weight but almost 1 and a half tons short. Now I’m no expert (in dinosaurs or math) but that sounds like such an incredible disparity in size. Was Thomas eating something that helped him put on weight faster? Was Jane simply a runt? Was T. rex like some modern raptors where the female is larger than the male, making Thomas “Tanya” and Jane “Joe”? Or most provocatively, was one a different species than the other? Only time, more fossils, and more research will tell. Just thought I’d share that with all of you.

Till next time!

4 thoughts on “Just a Thought

  1. Five pounds a day is nothing. Blue whales apparently gain around 200 lbs/day during the first year, and average about 80 lbs/day over the first 10 years. Since they’re weaned after the first year, most of the 10-year growth rate is accomplished while only feeding half the year (most baleen whales don’t eat while migrating). So, I don’t have much difficulty believing that Tyrannosaurus could gain at that rate.

    • excellent points. However, 7500 pounds in 2 years sounds very fast for a predatory reptile. Whales (and elephant seals) are able to put on so much in their early life because of their mothers fat-rich milk. I know elephant seal milk is like 51% fat. Also those whale feed on high energy krill (If only dinosaurs had those two things). I simply used 5 pounds because that’s the rate i keep reading. I have heard a figure of 1300 pounds a year for T. rex but even at that rate Jane would still be far short of Thomas.

      Weeeeeee! Discussion is fun!

  2. Im native centralcoast(pismobeach)and I love all the prehistoric/paleontology info I can get! i am a paleofiction writer so please contact me w/anything cuz i am your fan!!! respectfully,KENNEYSILLS

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