Scientists had long wondered about the origins of polygamy and paternal care patterns among modern-day Paleognathes -- an ancient avian lineage that branched off soon after birds evolved from dinosaurs and includes ostriches, emus and tinamous.
No such reproductive behavior exists among the vast majority of other vertebrates. Males contribute to parental care in less than 5 percent of mammal and non-avian reptile species, and while more than 90 percent of bird species co-parent to some degree, it is only among the Paleognathes that both polygamy and paternal care rule.
Now, in a groundbreaking paper (“Avian Paternal Care Had Dinosaur Origin”), paleobiologist Gregory M. Erickson of The Florida State University and researchers from three other institutions connect the evolutionary dots linking the polygamous, paternal reproductive patterns of extant (living) birds to the behavior of their extinct dinosaur kin.
“In those cases where adult dinosaurs have been found on top of nests, we found that the volume or mass of the egg clutch (total number of eggs in the nest) is very large relative to the size of the nesting animals,” Erickson said. “This suggests multiple females contributed the eggs and the male guarded them. Notably, the ratio of egg volumes to the nesting animal’s size is consistent with those in living birds where the male is the sole or primary nest attendant.”
The researchers now had their link from the theropod dinosaurs (omnivores and carnivores that walked on two hind legs with bird-like feet) to the polygamy and nesting scenarios exhibited by their avian descendants, according to David Varricchio of Montana State, the study’s principal investigator.
But to test the theory, Varricchio needed to determine the sex of the brooding dinosaurs whose bones have been found atop those communal nests.
For that, he turned to Erickson at Florida State, a renowned expert in dinosaur paleobiology.
Erickson examined the bone microstructure of tibiae (shin bones), femora (thigh bones) and metatarsus (ankle bones) from oviraptorids and deinonychosaurs (Jurrasic Park “raptors”) -- small theropod dinosaurs whose adult skeletons have been repeatedly discovered in brooding postures atop nests containing dozens of large eggs.
The key was what he didn’t find in the bones: They showed no signs whatsoever of the maternal and reproductively associated microscopic features common to living non-Paleognath bird groups, extinct non-avian dinosaurs or living reptiles.
“I found no evidence of medullary bone (the extra bone laid down by breeding female birds and dinosaurs to make eggs) or extensive bone resorbtion (the means by which female reptiles such as crocodiles acquire mineral salts to make eggs),” Erickson said. “This is consistent with the brooding dinosaurs being males.”
Thus, the researchers had confirmation that the dinosaurs found in nests with large egg clutches were polygamistic males and the source of the peculiar avian behavior.
Moreover, those brooding dinosaurs were fathers -- and today’s emus, rheas and tinamous owe their paternal care model to them.
Co-authors of “Avian Paternal Care Had Dinosaur Origin” -- accessible via the journal Science Web site at www.sciencemag.org/current.dtl -- are Florida State’s Erickson, associate professor of anatomy and vertebrate paleobiology in the Department of Biological Science; Varricchio, Frankie D. Johnson and John J. Borkowski of Montana State University; Jason R. Moore of Texas A&M University; and Mark A. Norell of New York City’s American Museum of Natural History.
Show me your leaves - Health check for urban trees
12.12.2017 | Gesellschaft für Ökologie e.V.
Liver Cancer: Lipid Synthesis Promotes Tumor Formation
12.12.2017 | Universität Basel
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
12.12.2017 | Physics and Astronomy
12.12.2017 | Earth Sciences
12.12.2017 | Power and Electrical Engineering