On the News | USA | Telling a dinosaur’s sex is no easy task, research shows @ The Columbus Dispatch

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Telling a dinosaur’s sex is no easy task, research shows


Image Credit: Mike Skrepnick

“The images are vivid: mother dinosaurs guarding their nests, males fighting each other for females or territory. But how do you tell the sex of a dinosaur?

Despite many claims to the contrary, recent research published in the journal Paleobiology by Jordan C. Mallon of the Canadian Museum of Nature shows that, for the most part, we can’t.

One exception is the presence of medullary bone.

When a female bird becomes pregnant, she produces a lacework of bone called medullary in the large hollow spaces of her thighbones. Toward the end of pregnancy, the medullary bone is absorbed and its calcium is used to make the shells for her babies.

Fossil medullary bone has been found only a few times, in a Tyrannosaurus rex specimen, in an Allosaurus, in two iguanodontid dinosaurs and in a Mesozoic bird.

That’s it. Five specimens out of thousands that have been studied over the years.

Of course, fossil medullary bone would be extremely rare — it occurs only in females and for only a few weeks during pregnancy.

One of the most famous discoveries of supposed sexual dimorphism (differences in appearance between males and females) among dinosaurs were the hadrosaurs, the so-called “duck-billed” dinosaurs of the Late Cretaceous in western North America.

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Differences in their head crests were thought to indicate whether a specimen was a male or female. That was until better data using rock layers showed that these “males” and “females” lived at different times and probably were different species, not different sexes.” (…) READ MORE

Lurdes Fonseca

Assistant Professor and Researcher at University of Lisbon
Sociologist (PhD), Paleontologist (Researcher in Micropaleontology), Majors in Sociology and Biology, Minor in Geology. Main interests in Paleontology: Microfossils, Molecular fossils, Paleobiology and Paleoecology. (read more about me)