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2009-03-17 – Trappola mortale per i piccoli dinosauri (Sinornithomimus herd)

Sulla rivista “Acta Palaeontologica Polonica”

Trappola mortale per i piccoli dinosauri

I resti suggeriscono che gli individui ancora immaturi venissero lasciati badare a loro stessi mentre gli adulti erano occupati nella costruzione del nido o nella cova delle uova

Un branco di giovani dinosauri simili a uccelli hanno trovato la morte nei fangosi margini di un lago circa 90 milioni di anni fa, secondo quanto annunciato da un gruppo di paleontologi cinesi e statunitensi che hanno scavato in un sito del Deserto del Gobi, nella parte occidentale della Mongolia interna.

L’improvvisa morte degli animali in una trappola di fango fornisce una rara istantanea del loro comportamento sociale. Composto soltanto da esemplari giovani di una singola specie di dinosauri ornitomimidi (Sinornithomimus dongi), il branco suggerisce che gli individui ancora immaturi venissero lasciati badare a loro stessi mentre gli adulti erano occupati nella costruzione de nido o nella cova delle uova.

“Non c’erano adulti intorno, questi cuccioli scorrazzavano da soli”, ha spiegato Paul Sereno, professore dell’Università di Chicago ed esploratore del National Geographic e coautore dell’articolo apparso sulla rivista “Acta Palaeontologica Polonica”.

Le prime ossa vennero scoperte da un geologo cinese nel 1978 alla base di una piccola collina in una desola regione del Deserto del Gobi e circa 20 anni fa un gruppo sino-giapponese estrasse i primi scheletri, battezzando il dinosauro Sinornithomimus (“che somiglia a un uccello cinese”).

Sereno e colleghi hanno seguito lo scavo di uno scheletro dopo l’altro fino a penetrare in profondità nella base della collina. Complessivamente, sono stati estratti 25 individui di età compresa tra uno e sette anni, come determinato dagli anelli di crescita annuale delle loro ossa.

Il gruppo ha poi registrato in meticolosamente la posizione di tutte le ossa e i dettagli degli strati di roccia per cercare di comprendere in che modo cosi tanti individui di una stessa specie siano periti nello stesso luogo. Gli scheletri mostrano un ottimo stato di conservazione e il fatto che siano tutti nella stessa direzione fa supporre che siano morti anche entro un arco temporale molto breve.

I dettagli forniscono le prove di una piccola tragedia. “Gli animali hanno subito una morte lenta in una trappola di fango, e la loro agitazione è servita solo ad attrarre predatori o animali che si nutrivano di carogne”, ha concluso Sereno. Di solito gli eventi atmosferici, l’azione di altri animali o il trasporto di ossa cancellano qualunque prova diretta delle cause di morte. Perciò questo sito è unico per ricchezza di dettagli sugli animali e sulla loro morte.” (fc)

fonte: lescienze

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Photo: “Teen” Dinosaurs Roamed in Herds, Mass Grave Suggests

Young Sinornithomimus dinosaurs may have wandered in packs (illustrated at top), fending for themselves while adults were busy nesting, according to a recent report.
Two juvenile Sinornithomimus skeletons (photo at bottom) died when they were a little over one year old. In their rib cages are stomach stones and the carbonized remains of the last plants they consumed.

Illustration by Todd Marshall, courtesy Project Exploration; photograph by Mike Hettwer, courtesy Project Exploration

Illustration by Todd Marshall, courtesy Project Exploration; photograph by Mike Hettwer, courtesy Project Exploration

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MSU paleontologist authors paper on social behavior among adolescent dinosaurs

March 16, 2009 — By Michael Becker, MSU News Service

BOZEMAN — A Montana State University researcher is the lead author of a recently published paper that sheds new light on the behaviors of dinosaur families and gives a rare glimpse into the social life — and death — of a herd of dinosaurs.
David Varricchio, an assistant professor and paleontologist in the Department of Earth Sciences, and colleagues from the University of Chicago and China wrote the paper after a 2001 expedition to the Gobi Desert. It was published in December in the journal Acta Palaeontologica Polonica.
The paper describes the team’s work at a 90-million-year-old dry lake bed in western Mongolia. Over the past decade, paleontologists have recovered more than two dozen fossilized skeletons of the dinosaur Sinornithomimus.
All of the skeletons belonged to animals between one and seven years old and were well-preserved. Most of skeletons were facing the same direction, suggesting that they died together in a short period of time, Varricchio said.
“Normally there are a lot of post-mortem effects that transpire between when a dinosaur died and when it was buried,” he said. “This site really provides, in my mind, better evidence than any other dinosaur locality of how the dinosaurs perished, and that’s pretty rare for any fossil vertebrate.”

Varricchio believes that the dinosaurs probably became mired in the mud around a partially dry lakebed during the Cretaceous Period. During times of drought, as were common in the region at the time, these oases likely attracted many animals, he said.

Many of those animals were probably weak from starvation and dehydration, which could explain why so many of them became trapped in the mud. It’s a phenomenon that’s still seen around dry desert lakes today, he said.

The fact that so many young dinosaurs of the same species died at roughly the same time and in the same place tells paleontologists something about the social behavior of the animals, Varricchio said. It may be that young dinosaurs — too old for the nest but not yet old enough to fend for themselves — roamed together in social herds, he said.

“We get a snapshot-like view of what a herd of these animals looked like back in the Cretaceous Period,” Varricchio said. “That snapshot gives us a glimpse into their biology and their behavior.”

Past studies have theorized that dinosaurs had strong and complicated parenting relationships with their young, Varricchio said. Female — and even male — dinosaurs were tied to a nesting spot for the breeding portions of the year while they took care of their eggs, he said.

The fact that the parent dinosaurs were busy with the eggs could explain why a group of adolescent dinosaurs was roaming together without adult supervision, Varricchio said. These and most dinosaurs would take several years, at least, to fully mature. Groups of juveniles would consist of those individuals too old to be cared for by parents, but too young to breed, he said.

“This site argues that this might be a general trend among dinosaurs,” and is further evidence of the theory that dinosaurs were dedicated parents, he said.

Varricchio’s collaborators include Paul Sereno from the University of Chicago, Tan Lin from he Department of Land and Resources of Inner Mongolia and Zhao Xijin from the Chinese Academy of Sciences. Also on the team were Jeffrey Wilson from the University of Michigan and Gabrielle Lyon from Project Exploration.

The work was funded by the National Geographic Society and the David and Lucile Packard Foundation.

 

 

 

 

Contact: David Varricchio at 406-994-6907 or djv@montana.edu.
 
 Hi-Resolution Image or PDF Available:
[View or Download] 1. MSU’s David Varricchio examines fossils in his laboratory in the basement of Traphagen Hall. (MSU photo by Kelly Gorham)

source: http://www.montana.edu/cpa/news/nwview.php?article=6951

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Teen dinosaurs hung out, got into trouble

MSNBC – ‎17 ore fa‎
Like teenagers today, some juvenile dinosaurs used to hang out together, according to research announced today. Also like teens, the dinos sometimes hung
Boston Globe

 

Frozen in time: Dinosaur herd’s mass grave unearthed

ABC Online – ‎5 ore fa‎
In the rocky desert of Inner Mongolia, an international team of palaeontologists has unearthed a mass grave of young dinosaurs. The 25 birdlike dinosaurs
Montana State University

marzo 17, 2009 - Posted by | - R. Dinosauri, - Teropodi, 1 Cretaceo, An. Vertebrates, Asia, Bl - Top posts, Mesozoic, P - Paleoetologia, P - Preservazione eccezionale, P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , ,

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