Professor talks dinosaur eggs

MONTANA LIVING — A Montana State University paleontologist lent his expertise in fossilized dinosaur eggs to a Jan. 2 New York Times story that highlighted the research of an MSU alumnus.

Written by James Gorman, the story, “Some dinosaur eggs took six months or more to hatch,” includes comments from David Varricchio, associate professor of paleontology in the MSU Department of Earth Sciences in the College of Letters and Science, about a study that found that some dinosaur eggs had incubation periods lasting half a year or longer. Varricchio was one of the scientists who reviewed the study, which was led by Gregory M. Erickson, a professor at Florida State University who earned his master’s degree in earth sciences from MSU in 1991.

 

The paper, published Monday in the Proceedings of the National Academy of Science, offers new information on the embryology of non-avian dinosaurs that were closely related to reptiles, such as crocodiles, and details how the eggs of these non-avian dinosaurs took twice as long to hatch as bird eggs of a similar size.

 

Gorman wrote: “The findings of the long incubation times complicate thinking about dinosaur behavior. While some kinds of dinosaurs may have tended their eggs and young, for others the difficulty of hanging around for most of a year to watch buried eggs would have been too much. And long incubation times mean slow reproduction, a definite disadvantage when a comet or asteroid slams into the planet, as happened 65 million years ago, leading to the extinction of dinosaurs and many other species. But not birds.”

In Gorman’s story, Varricchio said that the research used a new line of evidence — embryonic tooth age — and that the technique could prove valuable in future studies.

 

“Scientific opinions have varied on incubation times,” Gorman wrote. “Dr. Varricchio and other scientists had studied how porous fossilized eggshells were, which led them to conclude that the vast majority of dinosaur eggs were buried. And that behavior, similar to living reptiles, suggested long incubation times, (Varricchio) said.”

 

In his story, Gorman explained how Erickson and his colleagues used teeth from rare fossil embryos and fossilized eggs that were about to hatch, counting daily growth markers in the teeth and calculating that tooth growth accounted for 40 percent of incubation time.

 

“Dr. Erickson said the information from embryo teeth was the first direct evidence of how many days non-avian dinosaurs took to hatch,” Gorman wrote.

 

One question these long incubation periods raised for the researchers, Gorman wrote, included how dinosaurs would have been able to migrate, as some scientists have suggested, if they spent most of a year with their eggs.

 

“Do we expect them to have parental care?’ Dr. Varricchio said in Gorman’s story.

 

“(Varricchio) said that although there is evidence for parental care among some dinosaurs, those species had smaller eggs and most likely shorter incubation times,” Gorman wrote. “The very long incubation times would have meant dinosaur parents staying in one place for a whole year defending eggs and young.”

 

Erickson pointed out in Gorman's story that long incubation times would have been just one factor in the dinosaurs’ demise.

 

Gorman wrote: “'These animals were profligate wasters of energy,'” (Erickson) said. “They were big and warm-blooded and ‘even the smallest dinosaurs took over a year to mature,’ including time after hatching.

 

"'The dinosaurs found themselves holding some bad cards,'" (Erickson) said. “'They had a dead man’s hand.'”