The mystery of why the dinosaurs became extinct after a Cretaceous meteor strike, while birds and mammals thrived, may have been solved.
Paleontologists have discovered that dinosaur young took so long to hatch and mature into adulthood that populations failed to recover quickly enough after the devastating impact 65 million years ago.
In contrast, birds and small mammals took only a few weeks for their offspring to emerge giving them a distinct advantage.
The discovery was made by researchers at Florida State University and the University of Calgary, who realized it was possible to calculate how long it took for dinosaurs to hatch based on marks on the teeth of embryos and babies.
Similar to tree rings growing a new layer each year, teeth grow a new layer each day, which is seen in microscopic lines in the dentine. By counting the daily lines of Von Ebner, scientists found it took dinosaurs between three and six months to hatch.
The lengthy incubation period in the clutches of dinosaur eggs, in comparison to small mammals, made the hatchlings, and their parents, vulnerable to predators and left them struggling to re-establish their species.
“Some of the greatest enigmas about dinosaurs pertain to their embryology; virtually nothing is known,” Dr. Gregory Erickson of FSU said. “We suspect our findings have implications for understanding why dinosaurs went extinct at the end of the Cretaceous period, whereas amphibians, birds, mammals and other reptiles made it through and prospered.”
Because birds are in the same clade with dinosaurs, scientists have long assumed that the duration of dinosaur incubation was similar to birds, whose eggs hatch within 11 to 85 days.
However, similar-sized reptilian eggs typically take twice as long to hatch, ranging from several weeks to many months. To find out where dinosaurs fit in, the team studied the fossils of dinosaur embryos.
“Time within the egg is a crucial part of development, but this earliest growth stage is poorly known because dinosaur embryos are rare,” said Dr. Darla Zelenitsky of the U of Calgary. “Embryos can potentially tell us how dinosaurs developed and grew very early on in life and if they are more similar to birds or reptiles in these respects.”
The two types of dinosaur embryos researchers examined were those from a Protoceratops, (seen below) a goat-sized dinosaur found in the Gobi Desert of Mongolia whose eggs were chicken-egg-sized and Hypacrosaurus, a gigantic duck-billed dinosaur found in Alberta, Canada, with eggs weighing 4 kilograms (9 pounds.)
The researchers ran the embryonic jaws through a CT scanner to visualize the forming dentition. Then, they extracted several of the teeth to examine with a Scanning Electron Microscope (SEM).
Their results showed nearly three months incubation for the small Protoceratops embryos and six months for the embryos from the giant Hypacrosaurus (below).
Dental battery (the complex set of six-layered dinosaur teeth including replacement teeth) and von Ebner lines in fossil dinosaur teeth were first observed and illustrated over 150 years ago by Richard Owen (shown below), the scientist who coined the term Dinosauria or "Terrible Lizard."
I wonder if Dr. Owen would have given his eye teeth to change that moniker to Dinopoulia, Greek for "Terrible Bird."
It's Clutch Time, in more ways than one!
Steph
Paleontologists have discovered that dinosaur young took so long to hatch and mature into adulthood that populations failed to recover quickly enough after the devastating impact 65 million years ago.
In contrast, birds and small mammals took only a few weeks for their offspring to emerge giving them a distinct advantage.
The discovery was made by researchers at Florida State University and the University of Calgary, who realized it was possible to calculate how long it took for dinosaurs to hatch based on marks on the teeth of embryos and babies.
Similar to tree rings growing a new layer each year, teeth grow a new layer each day, which is seen in microscopic lines in the dentine. By counting the daily lines of Von Ebner, scientists found it took dinosaurs between three and six months to hatch.

The lengthy incubation period in the clutches of dinosaur eggs, in comparison to small mammals, made the hatchlings, and their parents, vulnerable to predators and left them struggling to re-establish their species.
“Some of the greatest enigmas about dinosaurs pertain to their embryology; virtually nothing is known,” Dr. Gregory Erickson of FSU said. “We suspect our findings have implications for understanding why dinosaurs went extinct at the end of the Cretaceous period, whereas amphibians, birds, mammals and other reptiles made it through and prospered.”
Because birds are in the same clade with dinosaurs, scientists have long assumed that the duration of dinosaur incubation was similar to birds, whose eggs hatch within 11 to 85 days.
However, similar-sized reptilian eggs typically take twice as long to hatch, ranging from several weeks to many months. To find out where dinosaurs fit in, the team studied the fossils of dinosaur embryos.
“Time within the egg is a crucial part of development, but this earliest growth stage is poorly known because dinosaur embryos are rare,” said Dr. Darla Zelenitsky of the U of Calgary. “Embryos can potentially tell us how dinosaurs developed and grew very early on in life and if they are more similar to birds or reptiles in these respects.”
The two types of dinosaur embryos researchers examined were those from a Protoceratops, (seen below) a goat-sized dinosaur found in the Gobi Desert of Mongolia whose eggs were chicken-egg-sized and Hypacrosaurus, a gigantic duck-billed dinosaur found in Alberta, Canada, with eggs weighing 4 kilograms (9 pounds.)
The researchers ran the embryonic jaws through a CT scanner to visualize the forming dentition. Then, they extracted several of the teeth to examine with a Scanning Electron Microscope (SEM).
Their results showed nearly three months incubation for the small Protoceratops embryos and six months for the embryos from the giant Hypacrosaurus (below).
Dental battery (the complex set of six-layered dinosaur teeth including replacement teeth) and von Ebner lines in fossil dinosaur teeth were first observed and illustrated over 150 years ago by Richard Owen (shown below), the scientist who coined the term Dinosauria or "Terrible Lizard."
I wonder if Dr. Owen would have given his eye teeth to change that moniker to Dinopoulia, Greek for "Terrible Bird."
It's Clutch Time, in more ways than one!
Steph
Sanning Electron Microscopes?
ReplyDeleteFixed.
DeleteRelieved.
DeleteFYI, I also added some background information above about Dr. Richard Owen (1804-1892) who was an early observer of von Ebner lines in fossil dinosaur teeth. He also coined the term
DeleteDinosauria; wonder if he wished he'd called them Dinopoulí, or "Terrible Birds" in Greek.
I wonder if there are other fossil markers of incubation time, besides the von Ebner lines, that could confirm this conclusion?
ReplyDeleteI wonder also, jan.
DeleteI enjoyed learning about the von Ebner lines; my dentist and I will now have another interesting topic of conversation. He likes to tell the same, really bad jokes so this will be a welcome departure. ;-)
I can see it now, a panel of dentists questioning a paleontologist holding a fossil tooth -- "What's my von Ebner Line?"
And what accounts for the periodicity in von Ebner's lines in the first place? I.e., how does an embryo know what day it is? Seems to me, it's always dark under a brontosaurus, especially after a big meteorite strike.
DeleteInteresting that they are able to give evidence for incubation; we are your indentured servants. I can't access the full article, but I wonder about the cause and effects leading to extinction:
ReplyDelete1. Size matters: even the smallest dinosaurs were pretty large, the birds were small. In a world with few resources a small animal, requiring less food, seems more likely to survive. Surviving mammals were also small, shrew or mouse size. Those animals also survived Mt St Helens, a few feet underground was enough protection from heat, and they could eke (eek!) out a living on underground seeds, roots, and insects. They can also eat a small bit of food and move to the next spot; seems unlikely that a dinosaur could do that.
Modern birds and mice also have a relatively flexible diet, another necessity with limited food supplies. The little mouse that invaded my office last month started with the cereal boxes on the shelf. After we put those away his final meal at my cafe was soy sauce packets!
So while there is a general correlation between size and incubation period in both birds and reptiles (not absolute), I think size matters for other reasons.
2. Mobility: birds have an enormous advantage here, they can travel several hundred miles in a day, and altitude and sharp vision are definite pluses while searching for food. Modern birds also have excellent location memory, they remember their route of feeding sites. Any ground based animal is in trouble in times of scarcity.
Most birds can live in a variety of habitats, and move to different altitudes fairly easily. Likely an advantage after a devastation.
3. Raising young: Here I partially agree, though it wasn't clear in the article. Brooding and raising young takes enormous energy; faster fledging is a lot easier for the parents. They can also do it all again, sheer numbers are probably an advantage.
eco, some thoughts on your thoughts:
Delete1. Many dinosaurs were chicken-sized.
2. Mobility is definitely a huge advantage for birds, who could also escape the environmental problems on the surface of the earth for long periods.
3. Yes, faster fledging is a distinct advantage for both mobility and number of offspring. Mammals, of course, have the advantage of carrying their incubators internally.
Agreed, though chickens are relatively large on the bird scale (compared to cute little songbirds) and definitely large compared to mice and shrews. I'm not sure birds can escape problems on the surface for "long" periods (albatrosses yes) but they can at least fly to a safer spot to avoid, say, the wildfires.
DeleteI probably could have stated my whole thesis as: Longer brooding times are generally associated with larger animals, and their size, limited mobility, and (perhaps) diet probably led to their demise, not their brooding.
Didn't Hamlet's brooding lead to his demise? [Sorry, couldn't resist.]
DeletePaul, haha, it certainly was a clutch scene for the "old" bird.
DeleteWhat's all this I read in PEOTS Comments about dutch scenes? I thought this was a blog about science!
DeleteOoh, it's not "dutch scenes"? It's "clutch scenes"?
Never mind.
LegoLitella
OWL BY MYSELF: a bird minute.
ReplyDeleteVery cute, unless you're a bug or a mouse.
DeleteI went to Cornell, and worked for an architecture firm in town after graduation; they did several projects for the school. One day (April 1, in fact) we had the secretary leave a note on one of the partner's desk that "Mr. Boyd" from the Lab of Ornithology had called.
"Are you sure there's no Mr. Boyd there?" A little bit of back and forth between him and the Lab's receptionist to figure it out....
"The discovery was made by researchers at Florida State University..."
DeleteFSU are the Seminoles. Florida are the GATORS... much more reptilian, should have an advantage in such prehistoric studies dionosaur and dino-soars.
When chemists analyze the elemental make-up of vonEbner and Owen dental lines in prehistoric boyds, do they use a beaker?
LegoWhoIsJustTalkingThroughHisFeatheredCapAsHeMarshallsMaterialsForHisOwnBlog
The Merlin Bird ID app from the Cornell Lab of Ornithology is great; have you tried it?
DeleteI only went to Ithaca once, to visit a friend in grad school. It was very gray.
The Mr. Boyd AFJ must have caused quite a flap! ;-)
Are those parrots in your thumbnail this week, eco?
Lego, I thought you were more prescient than usual when you posted about boyds, but realized you posted in between eco and my posts.
DeleteA big feather in your cap, then! Do we know your capsize? ;-)
I haven't tried the Merlin Bird or any other app, no cell phone in my existence. Yes, Ithaca can be gray, though the summers were wonderful, warm and rarely too hot.
DeleteYears ago there was an offshoot tribe of The Wild Parrots of Telegraph Hill, and a few of them used to hang out by my office. Not quite tame, but they were certainly comfortable around people, and they were good posers. I've since moved my office, and haven't seen them for several years. Sadly, I heard the flock was waning.
Wild Parrots is such a delight!
DeleteNo cell phone. That could be refreshing some days. Though my daughter uses it almost exclusively to text. "Why talk to someone when you can make it perfect in text? No awkward pauses, mom. . ."
From the Wild Parrots Storyline on IMDb:
DeleteThrough his own words, we learn of his life as a frustrated, homeless musician and how he came to live in the area where he decided to explore the nature around him. That lead him to discovering the parrot flock and the individual personalities of it.
Too be, or knot two bee ...
Ithaca, in the summer, is, as they say, gorges.
DeleteI've used the Merlin app only a few times; seems to work well.
Loved Wild Parrots. When visiting Istanbul a few years ago, enjoyed the many wild parrots and nesting cranes in beautiful Gülhane Park, in the middle of the old city.
That pesky lead, Paul. Confounding things here, there, and in Flint, MI.
DeleteThe lead author of this study is on NPR's Science Friday right now (in Colorado, at least).
ReplyDeletePeroxyZen: plant-based hydrogen peroxide: and what a perfect name for their product, H^2O^2!The patent is held by two Brown U PhD's who are in their 20's.
ReplyDeleteSupposing is good. . . Check out the twisted Scanning Electron Microscope (SEM) image!
ReplyDeleteYet another map projection
ReplyDeleteCreate your own Pangea
Deletejan, excellent!
DeletePaul, the plug-in is not supported on my device. Looks like a cool idea, though.
More on the Antikythera mechanism.
ReplyDeleteThat Lego block recreation of Antikythera: mind blown. Thanks for the link, jan.
DeleteIt finally happened! {11 seconds}
ReplyDeleteAnd I hear they finally did the experiment with 1000 apes and 1000 typewriters. They haven't typed a single page of Shakespeare yet, but they've gotten Twilight three times so far.
Deletejan, ever think of doing stand-up? That made me guffaw!
DeleteI can't take credit for that. I heard 40 years ago, and just updated the book from Valley of the Dolls. (Besides, what's a typewriter?)
Deletejan, you are a stand up guy ;-).
DeleteNew post on "The Ellipsis--Hot, Hot, Hot, Dot, Dot, Dots. . . And the Solar Eclipse of August 21, 2017" is now, at long last, up. Thanks for your patience!
ReplyDelete