Paleonews

Il blog dedicato ai Paleontologi !!!!

2009-02-03 – La tartaruga fossile e il polo “tropicale” (Turtle fossil and tropical Artic)

CLIMA: CANADA; FOSSILE TARTARUGA PROVA ANTICO EFFETTO SERRA

L’Artide 90 milioni di anni fa era un posto molto piu’ temperato: senza ghiacci e con passaggio migratorio degli animali preistorici. Lo sostengono alcuni scienziati dopo la scoperta di un fossile di tartaruga asiatica nell’Artide canadese. Secondo i ricercatori, tra cui Donald Brinkman del Royal Tyrell Museum dell’Alberta, la tartaruga tipica della Mongolia, chiamata ‘tartaruga aurora’, con il guscio quasi perfettamente rotondo, esistente all’epoca dei dinosauri e da tempo estinta, avrebbe percorso migliaia di chilometri dal suo habitat originario nelle acque dolci dell’Asia passando non dall’Alaska ma direttamente dal polo Nord. Questo proverebbe che nel polo Nord le temperature in passato erano molto piu’ temperate, al punto da rendere l’Artide un percorso migratorio delle creature preistoriche. Secondo i ricercatori un ‘super effetto serra’, forse originato da eruzioni vulcaniche, causo’ 90 milioni di anni fa un’enorme emissione di anidride carbonica scaldando i poli ed aprendo nuovi passaggi per gli animali migratori, comprese le tartarughe. (ANSA). COR-DI
02/02/2009 19:47

fonte: http://www.ansa.it/ambiente/notizie/notiziari/natura/20090202194734816739.html

——————————————————————–

Turtle fossil shows how ‘super-greenhouse effect’ created tropical Arctic

The discovery of a fossilised ancient turtle reveals the North Pole was once “extremely” warm and tropical, scientists said.

Turtle fossil shows how 'super-greenhouse effect' created tropical Arctic
The North Pole: “extremely” warm and tropical millions of years ago Photo: GETTY IMAGES

Animals migrated from Asia to North America directly across the formerly frost-free Arctic Ocean, new evidence shows.

Geologists made the breakthrough after discovering the fossil of a freshwater Asian turtle – dating back millions of years – in Canada.

John Tarduno, a US-based professor of geophysics at the University of Rochester, said: “We’ve known there’s been an interchange of animals between Asia and North America in the late cretaceous period, but this is the first example we have of a fossil in the High Arctic region showing how this migration may have taken place.

“We’re talking about extremely warm, ice-free conditions in the Arctic region, allowing migrations across the pole.”

Numerous rivers from the adjacent continents would have poured fresh water into the ancient Arctic sea, he said.

Fresh water, which is lighter than marine water, may have rested on top of the salty ocean water allowing animals such as the turtle to migrate with relative ease.

The professor, who published his findings in the journal Geology, added: “We found this turtle right on top of the last flood basalts – a large stretch of lava from a series of giant volcanic eruptions.

“That leads us to believe that the warming may have been caused by volcanoes pumping tremendous amounts of carbon dioxide into the Earth’s atmosphere.

“There is evidence that this volcanic activity happened all around the planet – not just the Arctic.

“If it all happened on a short-enough timescale, it could cause a super-greenhouse effect.”

The research team plans to return to the Arctic to look for more fossils.

source: http://www.telegraph.co.uk/earth/environment/climatechange/4419843/Turtle-fossil-shows-how-super-greenhouse-effect-created-tropical-Arctic.html

Annunci

febbraio 3, 2009 Posted by | - Rettili, 1 Cretaceo, An. Vertebrates, Antartide, Lang. - Italiano, Mesozoic, P - Paleoclimatologia, Paleontology / Paleontologia | , , , , , , , , , | Lascia un commento

2008-10-22 – Nuove ipotesi su migrazione dei Dinosauri polari (Polar dinosaurs, migration)

Uno studio condotto con un approccio di tipo fisiologio (ad es. energia necessaria) ha evidenziato che non tutti i dinosauri erano in grado di sostenere lunghe migrazioni da e verso i poli, ritenendo dunque plausibile che essi fossero invece adattati alla vita e al clima alle basse latitudini.

——————————————————————–

Polar dinosaurs may have taken shorter treks

Phil Bell holding a vertebra of a 70-million-year-old Saurolophus.

October 21, 2008 – Edmonton-Contrary to popular belief, polar dinosaurs may not have traveled nearly as far as originally thought when making their bi-annual migration.

University of Alberta researchers Phil Bell and Eric Snively have suggested that while some dinosaurs may have migrated during the winter season, their range was significantly less than previously thought, which means their treks were shorter. Bell and Snively’s findings were recently published in Alcheringa: An Australasian Journal of Paleontology.

The idea that these animals may have travelled distances nine times further than mule deer or four times those of wildebeest would have made them the greatest migrators in history. “There are strong opinions regarding dinosaur migration, but we decided to take a different approach, looking at variables such as energy requirements,” said Bell. Their research led them to suggest that migrating dinosaurs could have travelled up to 3,000 kilometres in a round trip-lasting perhaps up to six months-half of the distance suggested previously.

According to Bell, the notion of migrating polar dinosaurs is not new; however, previously-held beliefs were that the animals followed the centrally shifting sunlight, or latitudinal “sun line,” as part of their migration and would travel as far as 30 degrees of latitude, or 3,200 kilometres, in order to survive. Given their size and physiology, Bell and Snively have concluded that dinosaurs would have been incapable of sustaining the effort needed to make the trip. “When we looked at the energy requirements needed to support a three-tonne Edmontosaurus over this distance, we found it would have to be as energy efficient as a bird. No land animal travels that far today,” said Bell.

Bell does not dispute the evidence of migration and points to discoveries of large bone beds as evidence that many dinosaurs also traveled. In order to sustain the herd, “it seemed to make sense that they would be moving to and from the poles,” he said.

While this view of migration is feasible for some species of polar dinosaurs, it does not hold for all, Bell noted. “Many types of dinosaurs were surviving in polar latitudes at the time, and getting along quite fine,” said Bell. “They were not physically able to remove themselves from the environment for a variety of reasons and had to adapt to the cold, dark winters just as the rest of us mammals do today.”

 Related Internal Links

University of Alberta Department of Biological Sciences:
http://www.biology.ualberta.ca/

source: http://www.expressnews.ualberta.ca/article.cfm?id=9693
Other links: http://www.sciencedaily.com/releases/2008/10/081021185205.htm
————————————————————————————-
original article:
Alcheringa: An Australasian Journal of Palaeontology, Volume 32 Issue 3 2008 271 – 284
Authors: Phil R. Bell; Eric Snively
DOI: 10.1080/03115510802096101

Abstract

Cretaceous polar dinosaur faunas were taxonomically diverse, which suggests varied strategies for coping with the climatic stress of high latitudes. Some polar dinosaurs, particularly larger taxa such as the duckbill Edmontosaurus Lambe, 1917, were biomechanically and energetically capable of migrating over long distances, up to 2600 km. However, current evidence strongly suggests many polar dinosaurs (including sauropods, large and small theropods, and ankylosaurs of New Zealand) overwintered in preference to migration. Certain groups also appear more predisposed to overwintering based on their physical inability (related to biomechanics, natural history, or absolute size) to migrate, such as ankylosaurs and many small taxa, including hypsilophodontids and troodontids. Low-nutrient subsistence is found to be the best overwintering method overall, although the likelihood that other taxa employed alternative means remains plausible. Despite wide distribution of some genera, species-level identification is required to assess the applicability of such distributions to migration distances. Presently, such resolution is not available or contradicts the migration hypothesis.
Keywords: Alaska; Albian; Aptian; Australia; Campanian; Cretaceous; Dinosaur Cove; endothermy; migration; New Zealand; polar dinosaurs

ottobre 22, 2008 Posted by | - R. Dinosauri, 1 Cretaceo, America Northern, Antartide, Articolo sc. di riferimento, Oceania, P - Paleoetologia, Paleontology / Paleontologia | , , , , , , , , , , , | Lascia un commento

Tracce fossili di escavazione nel Triassico dell’Antartide

Articolo tratto da www.hindu.com (link):

Pre-dinosaur era burrows discovered in Antarctica

New York (PTI): Paleontologists have discovered pre-dinosaur era burrows in Antarctica, which they claim were probably dug up by tetrapods — any land vertebrates with four legs — about 245 million years ago. The largest burrow is about 35 centimetres long and six centimetres wide — it was preserved when a flood washed sand into it.

Though no animal remains were found inside the burrow casts, the hardened sediment in each burrow preserved a track made as the animals entered and exited, according to the paleontologists. “In addition, scratch marks from the animals’ initial excavation were apparent in some places. We have got evidence that these burrows were made by land-dwelling animals rather than crayfish,” Christian Sidor of Washington University, who led the team, said.

Despite the absence of fossil bones, the burrows’ relatively small size prompted the US team to speculate that their owners might have been small lizardlike reptiles called Procolophonids or an early mammal relative called Thrinaxodon.

giugno 9, 2008 Posted by | - Mammiferi, - Rettili, 3 Triassico, Antartide, P - Impronte, P - Ritrovamenti fossili, Paleontology / Paleontologia | , , , , , | Lascia un commento