econintersect.com
       
  

FREE NEWSLETTER: Econintersect sends a nightly newsletter highlighting news events of the day, and providing a summary of new articles posted on the website. Econintersect will not sell or pass your email address to others per our privacy policy. You can cancel this subscription at any time by selecting the unsubscribing link in the footer of each email.



posted on 14 October 2015

Fossilised Eggshells Help Crack The Mystery Of How Dinosaurs Kept Warm

from The Conversation

-- this post authored by Michael Benton, University of Bristol

We're slowly getting used to the idea that some dinosaurs may have looked more like birds than reptiles. But there's been a long-running debate about what dinosaurs were like on the inside - and specifically on how they kept warm. Were they warm-blooded like modern birds and mammals, or cold-blooded like modern lizards and crocodiles?

Now new evidence has emerged for the case that they were somewhere in between, neither just regulating their body temperature using internal energy (endothermy) nor relying solely on the warmth of their environment (ectothermy). Working out how dinosaurs' bodies worked is very difficult because we usually only have fossils of their bones. Almost all of the soft tissue and organs have usually rotted away. But the new evidence in this instance has come from a surprising place: fossilised eggshells.

Dinosaurs have always elicited wonder because of their great size and their dominance over the land for 170m years. Admittedly, many dinosaurs were turkey-sized, but most of our attention has focused on the giants. Some, like the sauropods Brachiosaurus or Brontosaurus, may have weighed as much 50 tonnes - ten times the mass of the largest living elephant.

Dinosaur physiologists wonder how such vast creatures could have operated. How did they find enough food each day? How did they pump blood up their long necks? How did they manage their body temperature so they neither overheated in summer nor froze in winter?

Titanosaur eggshell Gerald Grellet-Tinner

The thermophysiology debate flared in the 1970s, when a daring young researcher named Bob Bakker proposed that all dinosaurs were full endotherms (warm-blooded), just like their descendants the birds. Initially the debate was hugely polarised, with Bakker's opponents claiming dinosaurs must have shared more with their other living relatives, the crocodiles.

Soon, the physiologists pointed out that much of the argument was unnecessary. Modern vertebrates can vary in many subtle ways between full-scale endothermy and ectothermy. So it's reasonable to believe that dinosaurs could have fallen somewhere in between as well.

Too big to cool

Another theory, known as mass homeothermy, suggests some dinosaurs were so big that their bodies would have maintained a relatively stable temperature. Organisms gain and lose heat in proportion to their cross-sectional area or mass. A small animal like a mouse has to eat far more in proportion to its body mass than a large animal such as an elephant because the mouse radiates heat faster.

A big warm-blooded animal has greater thermal inertia - meaning it cools more slowly at night and warms up more slowly during the day - than a smaller animal of similar shape. When the alternative is eating huge amounts of food to keep the body's furnaces firing, this thermal stabilisation by mass makes sense.

The discovery that some theropod dinosaurs had avian-style feathers helped confirm that the smaller dinosaurs, like birds, probably used some kind of endothermy. The theory was further strengthened when evidence was found for feathers even in early, scaly dinosaurs. Animals that possessed feathers covering their bodies, even simple bristle-like structures, must have been insulated and so must have had some form of endothermy.

Titanosaur eggchunks in the Gobi desert Gerald Grellet-Tinner

The new research, published in Nature Communications, relies on a different kind of evidence from the structure of fossilised dinosaur eggs shells. The researchers, led by Robert Eagle of the University of California, Los Angeles, used a new geochemical technique called clumped isotope analysis. They looked at the kind of oxygen and carbon atoms the shells were formed from and worked out the corresponding temperature at which they were created. They argue the egg shell is formed deep within the mother's oviducts and so records her core body temperature.

By analysing exceptionally preserved eggshells from different types of dinosaur in Mongolia and Argentina, they found that giant sauropods such as Titanosaurus maintained body temperatures around 38℃, similar to modern large mammals. Meanwhile, small to medium-sized, bipedal and lanky oviraptorid theropods such as Oviraptor had temperatures of around 32℃, lower than most modern endotherms but about 6℃ higher than the typical environmental temperature of the time. If these animals maintained their body temperatures above the background environmental temperature, they were by definition endotherms, however they achieved it. But it is most likely that it was via their internal mechanisms.

The clumped isotope method is controversial - and critics may reject the exact values obtained in this study. But the researchers are at pains to justify their values, rejecting cases in which the eggshell has been altered by later physical processes and comparing measurements with those from surrounding carbonate rocks. They have also calibrated these fossil eggshell measurements with measurements from the eggshells of modern reptiles and birds.

What's particularly surprising about the results is that they suggest oviraptorid dinosaurs, which had feathers and so were probably more similar to modern birds, had lower body temperatures than the more reptilian sauropods. This means they probably used an intermediate, less-developed mode of endothermy to keep warm, whereas modern birds tend to be fully endothermic. The sauropods probably kept their temperature stable using their large mass, but why they were hotter is still a mystery.

The ConversationMichael Benton, Professor of Vertebrate Palaeontology, University of Bristol

This article was originally published on The Conversation. Read the original article.

>>>>> Scroll down to view and make comments <<<<<<

Click here for Historical News Post Listing










Make a Comment

Econintersect wants your comments, data and opinion on the articles posted.  As the internet is a "war zone" of trolls, hackers and spammers - Econintersect must balance its defences against ease of commenting.  We have joined with Livefyre to manage our comment streams.

To comment, using Livefyre just click the "Sign In" button at the top-left corner of the comment box below. You can create a commenting account using your favorite social network such as Twitter, Facebook, Google+, LinkedIn or Open ID - or open a Livefyre account using your email address.



You can also comment using Facebook directly using he comment block below.





Econintersect Contributors


search_box

Print this page or create a PDF file of this page
Print Friendly and PDF


The growing use of ad blocking software is creating a shortfall in covering our fixed expenses. Please consider a donation to Econintersect to allow continuing output of quality and balanced financial and economic news and analysis.


Take a look at what is going on inside of Econintersect.com
Main Home
Analysis Blog
Joan Robinson’s Critique of Marginal Utility Theory
The Truth About Trade Agreements - and Why We Need Them
News Blog
How To Stop Using Filler Words Like Um And Uh
02 December 2016: ECRI's WLI Growth Index Improvement Continues
Preliminary December 2016 Michigan Consumer Sentiment Highest Since Early 2015
October 2016 Wholesale Sales Improved
Rail Week Ending 03 December 2016: Finally A Positive Month
November 2016 CBO Monthly Budget Review: Total Receipts Up by 1 Percent in the First Two Months of Fiscal Year 2017
Infographic Of The Day: Copyright - Illegal Download
Early Headlines: Asia Stocks Mixed, Oil Steady, Bank Mafia, Trump To Remain TV Producer, US Life Expectancy Down, India Stocks Suffering, Park Impeached, China Struggles To Support Yuan And More
Heavy Metal And Hard Rock Albums That Went Certified Diamond Status
Down The Drain: Wastewater With The Most Cocaine
Apple's App Store Set For 5 Million Apps By 2020
How Can The UK Government Meet Its Legal Air Pollution Targets?
Most Gun Deaths In The United States Have A Tragic Motive
Investing Blog
Are Your Trade Entries Patient Enough?
Investing.com Technical Summary 08 December 2016
Opinion Blog
Looking At Everything: Trump's $1 Trillion Infrastructure Plan
The Global Financial Mess Is Due To Political Failure
Precious Metals Blog
Silver Prices Rebounded Today: Where They Are Headed
Live Markets
09Dec2016 Market Update: New Highs, New Correction Concerns Loom, Short-term Indicators Remain Bullish
Amazon Books & More






.... and keep up with economic news using our dynamic economic newspapers with the largest international coverage on the internet
Asia / Pacific
Europe
Middle East / Africa
Americas
USA Government



Crowdfunding ....






























 navigate econintersect.com

Blogs

Analysis Blog
News Blog
Investing Blog
Opinion Blog
Precious Metals Blog
Markets Blog
Video of the Day
Weather

Newspapers

Asia / Pacific
Europe
Middle East / Africa
Americas
USA Government
     

RSS Feeds / Social Media

Combined Econintersect Feed
Google+
Facebook
Twitter
Digg

Free Newsletter

Marketplace - Books & More

Economic Forecast

Content Contribution

Contact

About

  Top Economics Site

Investing.com Contributor TalkMarkets Contributor Finance Blogs Free PageRank Checker Active Search Results Google+

This Web Page by Steven Hansen ---- Copyright 2010 - 2016 Econintersect LLC - all rights reserved