|
The story of life on Earth is extraordinarily rich, diverse and complex. In this issues of Notes From the Biosphere, we've collected a series of interesting pieces of information having to do with the process of evolution. As you will see, not only has much happened in the past to create familiar species, the dynamic, life-shaping process of evolution is still busy creating new ones! - Editors.
A representation of the ancestral turtle species,Odontochelys semitestacea, with only half a shell. Painting by: Marlene Donnelly
How Turtles Got Their Shells...
The discovery of Odontochelys semitestacea, found in sediments deposited in China's Nanpanjiang Trough Basin, dates back 220 million years. This is around 14 million years older than previous fossils. The unique find helps to shed light on the evolution of the turtle's familiar appearance.
Chun Li of the Chinese Academy of Sciences described a new ancestral turtle species that was most probably aquatic and had teeth rather than a beak. While that may be interesting, what distinguishes this unusual find is the fact that represents an intermediary stage in turtle shell evolution. This species only had half a shell.
Odontochelys semitestacea, had a fully formed tummy shell or plastron. However, instead of the signature back shell or carapace, the species had bony extensions of the spine and broader ribs.
These photos clearly show the ancestral fossil's front with plastron and back with widened ribs. Photo credit IVPP.
This fossil find suggests that the previously held theories of the turtle's evolutionary process were incorrect. It had been theorized that ancient turtles had bony plates on their skin that are similar to modern crocodiles, which eventually fused to form the shell. The Odontochelys semitestacea fossil shows that the turtle's shell actually evolved from internal, skeletal changes.
Researchers back up this argument by referring to a modern turtle's embryonic development. In a modern turtle embryo, the carapace or back shell begins to form in the embryo through a extension of the backbone and widening of the ribs that looks remarkably similar to the Odontochelys semitestacea fossil.
Sources:
The Journal of Nature, www.nature.com
The New York Times, www. nytimes.com
For a beautiful Native American myth that describes another "theory" about how Turtle got its shell, go to: http://www.firstpeople.us/FP-Html-Legends/TurtleAndTheSkyBowl-Unknown.html - Editors.
______________
Fossils of female Maiacetus inuus with her near-term fetus still in utero delineated in blue. Credit: University of Michigan
Early Whales Gave Birth On Land
A recent fossil discovery in Pakistan uncovered skeletons of extinct pregnant female whale and male of the same species. The 47.5 million-year-old fossils, discovered in Pakistan in 2000 and 2004, are described in a paper published Feb. 4, 2009, in the online journal PLoS.
Male Maiacetus inuus with opaque skelton overlay. Credit: John Klausmeyer and Bonnie Miljour, University of Michigan
"This stunning discovery reinforces the belief that modern cetaceans* originated from terrestrial ancestors," said H. Richard Lane, program director in the National Science Foundation's Division of Earth Sciences, which funded the research.
This fossil find is the first discovery of a fetal skeleton of an extinct whale in the group known as Archaeoceti, and the find represents a new species dubbed, Maiacetus inuus.
Unlike modern whales who give birth tail first, the whale fetus of Maiacetus inuus is positioned for head-first delivery, like terrestrial mammals. This further suggests that these whales still gave birth on land.
Another clue to the whales' lifestyle is the well-developed set of teeth in the fetus, suggesting that Maiacetus newborns were equipped to fend for themselves, rather than being helpless in early life.
The whales' big teeth, well-suited for catching and eating fish, suggest the animals made their living in the sea, probably coming onto land only to rest, mate and give birth, said paleontologist Philip Gingerich of the University of Michigan, who led the team that made the discoveries.
Like other primitive archaeocetes, Maiacetus had four legs modified for foot-powered swimming, and although these whales could support their weight on their flipper-like limbs, they probably couldn't travel far on land.
"They clearly were tied to the shore," Gingerich said. "They were living at the land-sea interface and going back and forth."
Compared with previous fossil whale finds, the fossil, Maiacetus reveals an intermediary step on the evolutionary path of whales. Over time these full-time land dwellers eventually spent time in both realms prior to becoming exclusively ocean dwellers.
Source:
The National Science Foundation, www.nsf.org
Public Library of Science, www.plos.org
*The term "cetacean," refers to organisms in the taxonomic order, Cetacea. It is the order of organisms that includes whales, porpoises and dolphins. The designation of their place in the family tree of life would be: Phylum Chordata -> Subphylum Vertebrata -> Class Mammalia -> Order Cetacea. - Editors.
-----------------------
A female apple maggot fly, Rhagoletis pomonella, implants an egg into an apple. Wasps that attack the flies and eat their larvae appear to be changing on a genetic level in the same way that the flies themselves appear to be changing genetically. Photo credit, Rob Oakleaf.
North American Apples Prompt Evolutionary Changes in Insects
University of Notre Dame biologist, Jeff Feder and his colleagues say the introduction of apples to America almost 400 years ago ultimately may have changed the behavior of a fruit fly, leading to its modification and the subsequent modification of a parasitic wasp that feeds on it. Their findings were published in the journal Science in February. The result has been a chain reaction of biodiversity.
For almost 250 years after the introduction of apples to North America, insects referred to as hawthorn flies, Rhagoletis pomonella, continued to meet on the small, red fruit of hawthorn trees to mate and lay eggs. Then, in the mid-1800s, some of these "hawthorn flies" began to mate and lay eggs on apples instead. According to Feder, the flies attracted to apples eventually became genetically differentiated from the flies attracted to hawthorns, and so did the wasps that live on the flies' larvae.
"What is startling is how fast populations can ecologically adapt to new habitats and begin to evolve into different species in front of our eyes," Feder said.
Feder says the research is important because it provides insights into the origins of new species. "Clues can be found right before us as we sit on our deck chairs barbecuing and drinking pop. All we have to do is open our eyes and we can see new life forms coming into being in that scraggly old apple tree in our backyard."
This finding gives further support to the necessity for preserving biodiversity on plant Earth. "Biodiversity in essence is the source for new biodiversity," said Feder
Source:
The National Science Foundation, www.nsf.org
This discovery certainly provides encouraging news about Nature's resilience. - Editors.
Do you have news that would be right for Notes From The Biosphere? Let us know at: editors@spiritliving.org.
|
