Comments on: Secret of the Dinosaur Sexes Locked in Bone

By: Herman Diaz

Herman Diaz — Mon, 04 Mar 2013 16:34:35 +0000

Switek: “Such studies made me wonder if medullary bone could help paleontologists finally detect sexual dimorphism among non-avian dinosaurs. By picking a highly-ornamented species and searching for traces of medullary bone within those dinosaurs, researchers would be able to see whether the females all shared any distinctive anatomical structures or looked just like the males. The process wouldn’t identify all the females, but, if the attempt identified any at all, the investigation might help researchers determine whether there was any conspicuous features to distinguish the sexes.”

Don’t forget that that’s what Larson 2008 did w/T.rex, showing that the robust morphs (including Sue) were probably females (See the Galton quote). Otherwise, good summary (as usual).

Quoting Galton ( http://www.amazon.com/Bernissart-Dinosaurs-Cretaceous-Terrestrial-Ecosystems/dp/0253357217/ref=sr_1_1?s=books&ie=UTF8&qid=1357084950&sr=1-1 ): “In the theropod dinosaur Tyrannosaurus rex, there is also a femoral sexual dimorphism (Larson, 2008), with the robust morph identified as female based on pelvic dimensions and fused caudal vertebrae. Analyses for the presence of medullary bone in this same series of femora showed a significant clustering with the robust forms (Schweitzer et al., 2005). This indicates that the robust morph was probably female because female birds form medullary bone as a calcium reservoir to aid in egg shell formation (Dacke et al., 1993).”

By: Jack Heiss

Jack Heiss — Sat, 26 Jan 2013 21:12:56 +0000

In 2004, Dr. Mary Schweitzer at NC State discovered cellular features in a 68 mya T.rex fossil supplied to her by Dr. John Horner Museum of the Rockies. She was able to use the medullary bone of an ostrich to determine that the fossil was also female. This was reported in Smithsonian , May 2006.

By: Timothy Larson

Timothy Larson — Fri, 25 Jan 2013 15:25:47 +0000

I submitted a comment on January 24 to this article, please remove my post. thank you.

By: Timothy Larson

Timothy Larson — Thu, 24 Jan 2013 22:35:52 +0000

We are currently researching an isolated T. rex femur that was found with egg shell, the only egg shell which can be associated with T. rex as far as we are aware. We are currently testing some interesting internal structures on the fossil femur to see if they are or aren’t medulary bone. I am very excited at what the prospects might yield. FYI: the femur is of the robust morphotype (like SUE).

By: BJ Nicholls

BJ Nicholls — Wed, 23 Jan 2013 22:55:17 +0000

Looking at the preparation of this specimen, I wonder how such a sharp boundary for removal of the surface matrix was determined? It doesn’t appear that there’s any significant thickness to the tail feathers, yet the prep defines a very tight boundary. I’d love to see one of these “in the flesh”.

By: Zach Miller

Zach Miller — Wed, 23 Jan 2013 22:23:18 +0000

What a wonderful find. I’m surprised nobody did this earlier, given how many specimens of Confuciusornis are known. But you’re right that Microraptor and Anchiraptor, which both have plenty of specimens, might also be “sexed.” Anyway, great writeup, boss.