Featured Research

from universities, journals, and other organizations

New theory emerges for where some fish became four-limbed creatures

Date:
December 29, 2011
Source:
University of Oregon
Summary:
A small fish crawling on stumpy limbs from a shrinking desert pond is an icon of can-do spirit, emblematic of a leading theory for the evolutionary transition between fish and amphibians. This theorized image of such a drastic adaptation to changing environmental conditions, however, may, itself, be evolving into a new picture.

Romer's desert hypothesis, left, and Retallack's flooded woodland, right.
Credit: Image courtesy of University of Oregon

A small fish crawling on stumpy limbs from a shrinking desert pond is an icon of can-do spirit, emblematic of a leading theory for the evolutionary transition between fish and amphibians. This theorized image of such a drastic adaptation to changing environmental conditions, however, may, itself, be evolving into a new picture.

Related Articles


University of Oregon scientist Gregory J. Retallack, professor of geological sciences, says that his discoveries at numerous sites in Maryland, New York and Pennsylvania suggests that "such a plucky hypothetical ancestor of ours probably could not have survived the overwhelming odds of perishing in a trek to another shrinking pond."

This scenario comes from the late Devonian, about 390 million years ago to roughly 360 million years ago. Paleontologist Alfred Romer, who died in 1973 after serving on the faculties at the University of Chicago and Harvard University, saw this time as a period of struggle and escape -- and important in fish-tetrapod transition -- to ensure survival.

Reporting in the May 2011 issue of the Journal of Geology, Retallack, who also is co-director of paleontological collections at the UO's Museum of Natural and Cultural History, argues for a very different explanation. He examined numerous buried soils in rocks yielding footprints and bones of early transitional fossils between fish and amphibians of Devonian and Carboniferous geological age. What he found raises a major challenge to Romer's theory.

"These transitional fossils were not associated with drying ponds or deserts, but consistently were found with humid woodland soils," he said. "Remains of drying ponds and desert soils also are known and are littered with fossil fish, but none of our distant ancestors. Judging from where their fossils were found, transitional forms between fish and amphibians lived in wooded floodplains. Our distant ancestors were not so much foolhardy, as opportunistic, taking advantage of floodplains and lakes choked with roots and logs for the first time in geological history."

Limbs proved handy for negotiating woody obstacles, and flexible necks allowed for feeding in shallow water, Retallack said. By this new woodland hypothesis, the limbs and necks, which distinguish salamanders from fish, did not arise from reckless adventure in deserts, but rather were nurtured by a newly evolved habitat of humid, wooded floodplains.

The findings, he said, dampen both the desert hypothesis of Romer and a newer inter-tidal theory put forth by Grzegorz Niedbwiedzki and colleagues at the University of Warsaw. In 2010, they published their discovery of eight-foot-long, 395-million-year-old tetrapods in ancient lagoonal mud in southeastern Poland, where Retallack also has been studying fossil soils with Polish colleague Marek Narkeiwicz.

"Ancient soils and sediments at sites for transitional fossils around the world are critical for understanding when and under what conditions fish first walked," Retallack said. "The Darwin fish of chrome adorning many car trunks represents a particular time and place in the long evolutionary history of life on earth." UO Academic Support Funds supported Retallack's research.


Story Source:

The above story is based on materials provided by University of Oregon. Note: Materials may be edited for content and length.


Journal Reference:

  1. Gregory J. Retallack. Woodland Hypothesis for Devonian Tetrapod Evolution. The Journal of Geology, 2011; 119 (3): 235 DOI: 10.1086/659144

Cite This Page:

University of Oregon. "New theory emerges for where some fish became four-limbed creatures." ScienceDaily. ScienceDaily, 29 December 2011. <www.sciencedaily.com/releases/2011/12/111227142628.htm>.
University of Oregon. (2011, December 29). New theory emerges for where some fish became four-limbed creatures. ScienceDaily. Retrieved November 27, 2014 from www.sciencedaily.com/releases/2011/12/111227142628.htm
University of Oregon. "New theory emerges for where some fish became four-limbed creatures." ScienceDaily. www.sciencedaily.com/releases/2011/12/111227142628.htm (accessed November 27, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Thursday, November 27, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Classic Hollywood Memorabilia Goes Under the Hammer

Classic Hollywood Memorabilia Goes Under the Hammer

Reuters - Entertainment Video Online (Nov. 26, 2014) The iconic piano from "Casablanca" and the Cowardly Lion suit from "The Wizard of Oz" fetch millions at auction. Sara Hemrajani reports. Video provided by Reuters
Powered by NewsLook.com
Pet Dogs to Be Used in Anti-Ageing Trial

Pet Dogs to Be Used in Anti-Ageing Trial

Reuters - Innovations Video Online (Nov. 26, 2014) Researchers in the United States are preparing to discover whether a drug commonly used in human organ transplants can extend the lifespan and health quality of pet dogs. Video provided by Reuters
Powered by NewsLook.com
From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

From Popcorn To Vending Snacks: FDA Ups Calorie Count Rules

Newsy (Nov. 25, 2014) The US FDA is announcing new calorie rules on Tuesday that will require everywhere from theaters to vending machines to include calorie counts. Video provided by Newsy
Powered by NewsLook.com
Feast Your Eyes: Lamb Chop Sent Into Space from UK

Feast Your Eyes: Lamb Chop Sent Into Space from UK

Reuters - Light News Video Online (Nov. 25, 2014) Take a stab at this -- stunt video shows a lamb chop's journey from an east London restaurant over 30 kilometers into space. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins