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2008-12-23 – I dinosauri e le cure parentali (Dinosaurs and parental care)

 

DINOSAURI I PRIMI BABYSITTER

2008-12-19 19:06
 
Fare il babysitter è un lavoro antichissimo, preistorico addirittura, come mostrano le uova di dinosauro che 75 milioni di anni fa erano covate da maschi. Secondo uno studio americano pubblicato questa settimana su Science, i maschi dei terribili velociraptor, i dinosauri carnivori onnipresenti nel romanzo e nel film “Jurassic Park”, erano degli ottimi babysitter.

Come accade oggi in moltissime specie di uccelli, erano i maschi ad occuparsi del nido, a sorvegliare, difendere e accudire le uova. “Si ritiene comunemente che le femmine si concentrassero nel deporre le uova e nel procacciare il cibo e stanno diventando sempre più numerose le evidenze che additano i maschi come coloro che effettivamente si prendevano cura delle uova”, osserva il coordinatore della ricerca, Jason Moore, dell’università del Texas. In collaborazione con le università del Montana e della Florida e con il Museo Americano di Storia Naturale di New York, Moore ha scoperto e studiato sei nidi di dinosauro nello Stato americano del Montana e in Mongolia. I nidi risalgono a a circa 75 milioni di anni fa, sono in buono stato di conservazione e ognuno di essi contiene da 22 a 30 uova.

Sui nidi e attorno ad essi si trovano numerosa ossa i individui adulti. I ricercatori hanno scoperto che uova e ossa appartengono almeno a tre specie di dinosauri: troodonti, oviraptor e citipati, parenti dei velociraptor resi celebri da “Jurassic Park”. Nelle tre le specie, tutte fortemente imparentate con i moderni uccelli, le ossa trovate in prossimità dei nidi appartenevano a maschi. Sono infatti prive delle cavità che si formavano all’interno delle ossa delle femmine quando deponevano le uova. “Le ossa che abbiamo trovato più vicine alle uova – rileva Moore – non mostrano alcuna caratteristiche che indichi l’appartenenza a femmine di dinosauro”.

Di qui la conclusione dei ricercatori che in alcune specie di dinosauri erano i maschi a prendersi cura delle uova e a sorvegliarle, proprio come oggi accade negli uccelli, nei quali i maschi partecipano alle cure parentali per il 90% del tempo. Nei mammiferi, invece, i maschi si prendono cura della prole solo nel 5% delle specie. Per i ricercatori la scoperta dei dinosauri-babysitter è un punto di partenza per studiare comportamenti analoghi in altre specie animali.

 
 

ANSA

DINOSAURI I PRIMI BABYSITTER
ANSA – 2 ore fa
Secondo uno studio americano pubblicato questa settimana su Science, i maschi dei terribili velociraptor, i dinosauri carnivori onnipresenti nel romanzo e nel film “Jurassic Park”, erano degli ottimi babysitter. Come accade oggi in moltissime specie di
dinosauri i primi babysitter L’Unione Sarda
e altri 6 articoli simili »

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Florida State researcher Erickson ties rare bird behavior to dinosaur ancestors

Sure, they’re polygamous, but male emus and several other ground-dwelling birds also are devoted dads, serving as the sole incubators and caregivers to oversized broods from multiple mothers. It is rare behavior, but research described in the Dec. 19 Science found that it runs in this avian family, all the way back to its dinosaur ancestors. 

Gregory Erickson

Gregory Erickson

 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.

By Libby Fairhurst

source: http://www.fsu.edu/news/2008/12/18/rare.bird/


Canada.com

Dinosaur day care dads
Science News – 3 ore fa
New analyses of fossilized dinosaur eggs and bones suggest that male dinosaurs likely sat on nests and cared for their young, similar to the parental division of labor seen in some modern birds.
Daddy day-care: dinosaur fathers guarded the eggs Reuters
Dinosaur Dads Played “Mr. Mom”? National Geographic
eFluxMedia – Discover Magazine – FOXNews – eFluxMedia
e altri 56 articoli simili »


Scientist Live

Polygamy, Paternal Care In Birds Linked To Dinosaur Ancestors
Science Daily (press release) – 18 dic 2008
19 Science found that it runs in this avian family, all the way back to its dinosaur ancestors. Scientists had long wondered about the origins of polygamy and paternal care patterns among modern-day Paleognathes — an ancient avian lineage that
Odd bird fathering styles may come from dinos World Science
Avian Paternal Care Had Dinosaur Origin Science Magazine (subscription)
ScienceBlogs – United Press International
e altri 19 articoli simili »

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Scientific article:

Avian Paternal Care Had Dinosaur Origin

David J. Varricchio, Jason R. Moore, Gregory M. Erickson, Mark A. Norell, Frankie D. Jackson, and John J. Borkowski
Science 19 December 2008: 1826-1828.
The large egg clutches of troodontid and oviraptor dinosaurs and evidence that fossils of brooding dinosaurs were males shows that paternal care was ancestral to birds.
Abstract »   Full Text »   PDF »   Supporting Online Material »  

dicembre 23, 2008 - Posted by | - R. Dinosauri, - Teropodi, - Uccelli / Birds, 1, Articolo sc. di riferimento, Lang. - Italiano, P - Paleoetologia, Paleontology / Paleontologia, X - Science | , , , , ,

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