How long did it take to hatch a dinosaur egg? 3-6 months

A human typically gives birth after nine months. An ostrich hatchling emerges from its egg after 42 days. But how long did it take for a baby dinosaur to incubate?

Groundbreaking research led by a Florida State University professor establishes a timeline of anywhere from three to six months depending on the dinosaur.

In an article in the Proceedings of the National Academy of Sciences, FSU Professor of Biological Science Gregory Erickson and a team of researchers break down the complicated biology of these prehistoric creatures and explain how embryonic dental records solved the mystery of how long dinosaurs incubated their eggs.

“Some of the greatest riddles about dinosaurs pertain to their embryology — virtually nothing is known,” Erickson said. “Did their eggs incubate slowly like their reptilian cousins — crocodilians and lizards? Or rapidly like living dinosaurs — the birds?”

Scientists had long theorized that dinosaur incubation duration was similar to birds, whose eggs hatch in periods ranging from 11-85 days. Comparable-sized reptilian eggs typically take twice as long — weeks to many months.

Because the eggs of dinosaurs were so large — some were about 4 kilograms or the size of a volleyball — scientists believed they must have experienced rapid incubation with birds inheriting that characteristic from their dinosaur ancestors.

Erickson, FSU graduate student David Kay and colleagues from University of Calgary and the American Museum of Natural History decided to put these theories to the test.

To do that, they accessed some rare fossils — those 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 co-author Darla Zelenitsky, assistant professor of geoscience at University 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 Protoceratops — a sheep-sized dinosaur found in the Mongolian Gobi Desert whose eggs were quite small (194 grams) — and Hypacrosaurus, an enormous duck-billed dinosaur found in Alberta, Canada with eggs weighing more than 4 kilograms.

Erickson and his team ran the embryonic jaws through a CT scanner to visualize the forming dentition. Then, they extracted several of the teeth to further examine them under sophisticated microscopes.

Researchers found what they were looking for on those microscope slides. Growth lines on the teeth showed researchers precisely how long the dinosaurs had been growing in the eggs.

“These are the lines that are laid down when any animal’s teeth develops,” Erickson said. “They’re kind of like tree rings, but they’re put down daily. We could literally count them to see how long each dinosaur had been developing.”

Their results showed nearly three months for the tiny Protoceratops embryos and six months for those from the giant Hypacrosaurus.

“Dinosaur embryos are some of the best fossils in the world,” said Mark Norell, Macaulay Curator for the American Museum of Natural History and a co-author on the study. “Here, we used spectacular fossils specimens collected by American Museum expeditions to the Gobi Desert, coupled them with new technology and new ideas, leading us to discover something truly novel about dinosaurs.”

The implications of long dinosaur incubation are considerable.

In addition to finding that dinosaur incubation was similar to primitive reptiles, the researchers could infer many aspects of dinosaurian biology from the results.

Prolonged incubation put eggs and their parents at risk from predators, starvation and other environmental risk factors. And theories that some dinosaurs nested in the more temperate lower latitude of Canada and then traveled to the Arctic during the summer now seem unlikely given the time frame for hatching and migration.

The biggest ramification from the study, however, relates to the extinction of dinosaurs. Given that these warm-blooded creatures required considerable resources to reach adult size, took more than a year to mature and had slow incubation times, they would have been at a distinct disadvantage compared to other animals that survived the extinction event.

“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,” Erickson said.

This research was supported by the National Science Foundation.

Story Source:

Materials provided by Florida State University. Original written by Kathleen Haughney. Note: Content may be edited for style and length.

Dinosaur Egg Study Supports Evolutionary Link Between Birds and Dinosaurs: How Troodon Likely Hatched Its Young

A small, bird-like North American dinosaur incubated its eggs in a similar way to brooding birds — bolstering the evolutionary link between birds and dinosaurs, researchers at the University of Calgary and Montana State University study have found.

Among the many mysteries paleontologists have tried to uncover is how dinosaurs hatched their young. Was it in eggs completely buried in nest materials, like crocodiles? Or was it in eggs in open or non-covered nests, like brooding birds?

Using egg clutches found in Alberta and Montana, researchers Darla Zelenitsky at the University of Calgary and David Varricchio at Montana State University closely examined the shells of fossil eggs from a small meat-eating dinosaur called Troodon.

In a finding published in the spring issue of Paleobiology, they concluded that this specific dinosaur species, which was known to lay its eggs almost vertically, would have only buried the egg bottoms in mud.

“Based on our calculations, the eggshells of Troodon were very similar to those of brooding birds, which tells us that this dinosaur did not completely bury its eggs in nesting materials like crocodiles do,” says study co-author Zelenitsky, assistant professor of geoscience.

“Both the eggs and the surrounding sediments indicate only partial burial; thus an adult would have directly contacted the exposed parts of the eggs during incubation,” says lead author Varricchio, associate professor of paleontology.

Varricchio says while the nesting style for Troodon is unusual, “there are similarities with a peculiar nester among birds called the Egyptian Plover that broods its eggs while they’re partially buried in sandy substrate of the nest.”

Paleontologists have always struggled to answer the question of how dinosaurs incubated their eggs, because of the scarcity of evidence for incubation behaviours.

As dinosaurs’ closest living relatives, crocodiles and birds offer some insights.

Scientists know that crocodiles and birds that completely bury their eggs for hatching have eggs with many pores or holes in the eggshell, to allow for respiration.

This is unlike brooding birds which don’t bury their eggs; consequently, their eggs have far fewer pores.

The researchers counted and measured the pores in the shells of Troodon eggs to assess how water vapour would have been conducted through the shell compared with eggs from contemporary crocodiles, mound-nesting birds and brooding birds.

They are optimistic their methods can be applied to other dinosaur species’ fossil eggs to show how they may have been incubated.

“For now, this particular study helps substantiate that some bird-like nesting behaviors evolved in meat-eating dinosaurs prior to the origin of birds. It also adds to the growing body of evidence that shows a close evolutionary relationship between birds and dinosaurs,” Zelenitsky says.

World’s Oldest Dinosaur Embryo Bonebed Yields Organic Remains

Apr. 10, 2013 — The great age of the embryos is unusual because almost all known dinosaur embryos are from the Cretaceous Period. The Cretaceous ended some 125 million years after the bones at the Lufeng site were buried and fossilized.

Led by University of Toronto Mississauga paleontologist Robert Reisz, an international team of scientists from Canada, Taiwan, the People’s Republic of China, Australia, and Germany excavated and analyzed over 200 bones from individuals at different stages of embryonic development.

“We are opening a new window into the lives of dinosaurs,” says Reisz. “This is the first time we’ve been able to track the growth of embryonic dinosaurs as they developed. Our findings will have a major impact on our understanding of the biology of these animals.”

The bones represent about 20 embryonic individuals of the long-necked sauropodomorph Lufengosaurus, the most common dinosaur in the region during the Early Jurassic period. An adult Lufengosaurus was approximately eight metres long.

The disarticulated bones probably came from several nests containing dinosaurs at various embryonic stages, giving Reisz’s team the rare opportunity to study ongoing growth patterns. Dinosaur embryos are more commonly found in single nests or partial nests, which offer only a snapshot of one developmental stage.

To investigate the dinosaurs’ development, the team concentrated on the largest embryonic bone, the femur. This bone showed a consistently rapid growth rate, doubling in length from 12 to 24 mm as the dinosaurs grew inside their eggs. Reisz says this very fast growth may indicate that sauropodomorphs like Lufengosaurus had a short incubation period.

Reisz’s team found the femurs were being reshaped even as they were in the egg. Examination of the bones’ anatomy and internal structure showed that as they contracted and pulled on the hard bone tissue, the dinosaurs’ muscles played an active role in changing the shape of the developing femur. “This suggests that dinosaurs, like modern birds, moved around inside their eggs,” says Reisz. “It represents the first evidence of such movement in a dinosaur.”

The Taiwanese members of the team also discovered organic material inside the embryonic bones. Using precisely targeted infrared spectroscopy, they conducted chemical analyses of the dinosaur bone and found evidence of what Reisz says may be collagen fibres. Collagen is a protein characteristically found in bone.

“The bones of ancient animals are transformed to rock during the fossilization process,” says Reisz. “To find remnants of proteins in the embryos is really remarkable, particularly since these specimens are over 100 million years older than other fossils containing similar organic material.”

Only about one square metre of the bonebed has been excavated to date, but this small area also yielded pieces of eggshell, the oldest known for any terrestrial vertebrate. Reisz says this is the first time that even fragments of such delicate dinosaur eggshells, less than 100 microns thick, have been found in good condition.

“A find such as the Lufeng bonebed is extraordinarily rare in the fossil record, and is valuable for both its great age and the opportunity it offers to study dinosaur embryology,” says Reisz. “It greatly enhances our knowledge of how these remarkable animals from the beginning of the Age of Dinosaurs grew.”

Four Dinosaur Egg Species Identified in Lleida, Spain

Mar. 12, 2013 — A study headed by the Miquel Crusafont Catalan Palaeontology Institute has for the first time documented detailed records of dinosaur egg fossils in the Coll de Nargó archaeological site in Lleida, Spain. Up until now, only one type of dinosaur egg had been documented in the region
The archaeological site in Coll de Nargó containing dinosaur eggs lies some 8 kilometres to the west of the town that bears the same name in the province of Lleida. This region is home to different types of geological formations, including the Areniscas de Arén Formation and the Tremp Formation, which have provided a rich and varied yield of dinosaur fossils through the entire Pyrenees region.

“Eggshells, eggs and nests were found in abundance and they all belong to dinosaurs, sauropods in particular. Up until now, only one type of dinosaur egg had been documented in the region: Megaloolithus siruguei. After analysing more than 25 stratus throughout the Tremp Formation, a minimum of four different additional types were identified: Cairanoolithus roussetensis, Megaloolithus aureliensis, Megaloolithus siruguei and Megaloolithus baghensis,” as explained by Albert García Sellés from the Miquel Crusafont Catalan Palaeontology Institute and lead author of the study.

One of the main problems faced by palaeontologists when studying fossil remains is determining the age of the sediments that contain them. There are fossils known as “guide fossils” whose characteristics allow for the age of rocks to be deduced. However, these fossils are frequent in marine sediments but more scarce and difficult to find in land sediments.

“It has come to light that the different types of eggs (oospecies) are located at very specific time intervals. This allows us to create biochronological scales with a precise dating capacity. In short, thanks to the collection of oospecies found in Coll de Nargó we have been able to determine the age of the site at between 71 and 67 million years,” ensures the expert.

The paleontological sites in the south of Europe containing dinosaur remains have a high scientific value since they allow us to understand and thus reconstruct the ecosystems at the end of the Mesozoic Era.

The latest scientific investigations show that the dinosaur fauna of the European Continent living for a short time before the great extinction some 66 million years ago can be found exactly on the southern side of the Pyrenees.

A connection between French and Spanish dinosaurs

The discovery of Cairanoolithus fossils in this area is an important finding. Given that this type of eggs is only known in the south of France, they are the first of their kind found in the Iberian Peninsula.

According to García Sellés, this discovery constitutes a new proof of the connection between dinosaur fauna in France and in the Iberian Peninsula some 70 million years ago.

Furthermore, finding dinosaur eggs and nests in more than 25 stratigraphic levels provides clear evidence that these sauropods used the Coll de Nargó region as a nesting area for millions of years.

“We had never found so many nests in the one area before. In addition, the presence of various oospecies at the same level suggests that different types of dinosaurs shared the same nesting area,” concludes the scientist.