Over 400 million year old fish discovered in China


Guiyu oneiros, the newly discovered species

From Talk Rational! forum:

Zhu, M. et al. (2009) The oldest articulated osteichthyan reveals mosaic gnathostome characters. Nature, 458, 469-474.

The evolutionary history of osteichthyans (bony fishes plus tetrapods) extends back to the Ludlow epoch of the Silurian period. However, these Silurian forms have been documented exclusively by fragmentary fossils. Here we report the discovery of an exceptionally preserved primitive fish from the Ludlow of Yunnan, China, that represents the oldest near-complete gnathostome (jawed vertebrate).

The postcranial skeleton of this fish includes a primitive pectoral girdle and median fin spine as in non-osteichthyan gnathostomes, but a derived macromeric squamation as in crown osteichthyans, and substantiates the unexpected mix of postcranial features in basal sarcopterygians, previously restored from the disarticulated remains of Psarolepis. As the oldest articulated sarcopterygian, the new taxon offers insights into the origin and early divergence of osteichthyans, and indicates that the minimum date for the actinopterygiansarcopterygian split was no later than 419 million years ago.

See also here. And here. And here.

Cartoon depictions of the first animals to emerge from the ocean and walk on land often show a simple fish with feet, venturing from water to land. But according to Jennifer Clack, a paleontologist at the University of Cambridge who has studied the fossils of these extinct creatures for more than two decades, the earliest land vertebrates — also known as tetrapods — were more diverse than we could possibly imagine: here.

Harbour seals are back in New York


This video from the USA is called Many seals spotted in New York Harbor.

After more than a century, harbour seals are back in New York City.

This video says about itself:

Canadian Seal Killers & DFO have a lot to hide from the world. Canadian Sealers passed a LAW that stops YOU from getting pictures of their crimes against nature. This video reveals multiple crimes and violations, and they attempted to confiscate it so that You in the world would not see it.

A family who found a baby seal in their back garden in Kent 18 miles from the sea named her Rudolph, saying she was a “brilliant Christmas present”: here.

Canadian Chefs Serve Seal, With a Side of Controversy: here.

Fish which went extinct with the dinosaurs


From Animal Science Blog:

Why those fishes went extinct 65 million years ago

Large size and a fast bite spelled doom for bony fishes during the last mass extinction 65 million years ago, according to a new study to be published March 31, 2009, in the Proceedings of the National Academy of Sciences.

Today, those same features characterize large predatory bony fishes, such as tuna and billfishes, that are currently in decline and at risk of extinction themselves, said Matt Friedman, author of the study and a graduate student in evolutionary biology at the University of Chicago.

“The same thing is happening today to ecologically similar fishes,” he said. “The hardest hit species are consistently big predators”.

Studies of modern fishes demonstrate that large body size is linked to large prey size and low rates of population growth, while fast-closing jaws appear to be adaptations for capturing agile, evasive prey; in other words, other fishes. The fossil record provides some remarkable evidence supporting these estimates of function: fossil fishes with preserved stomach contents that record their last meals.

When an asteroid struck the earth at the end of the Cretaceous about 65 million years ago, the resultant impact clouded the earth in soot and smoke. This blocked photosynthesis on land and in the sea, undermined food chains at a rudimentary level, and led to the extinction of thousands of species of flora and fauna, including dinosaurs.

Scientists had speculated that during that interval large predatory fishes might have been more likely than other fishes to go extinct because they tended to have slowly increasing populations, live more spread out, take longer to mature, and occupy precarious positions at the tops of food chains. Today, ecologically similar fishes appear to be the least able to rebound from declining numbers due to overfishing.

To build the database he needed to test this prediction, Friedman traveled around the world measuring the body size and jaw bones of 249 genera of fossil fishes that lived during the late Cretaceous. These kinds of direct measurements are possible in fossil fishes because many are represented by complete, articulated individuals. This is unlike the fossil record of most other vertebrates, where bones, teeth and other parts of the skeleton are often scattered and found in isolation.

This study is the first to test this theory with hard data and to quantify the relationship between body size, jaw function and vulnerability of fishes during the Cretaceous extinction, according to Friedman.

“Anyway you sliced it, the data showed that if you were a big fish with a fast bite you were toast,” he said.

Ironically, today’s large fishes with fast bites evolved relatively shortly after the end-Cretaceous extinction, apparently filling the functional and ecological roles vacated by the victims of that mass extinction. Although the two groups of fishes are not related to each other, their fates may end up being similar.

The paper is called “Ecomorphological selectivity among marine teleost fishes during the end-Cretaceous extinction” and will appear in issue 13 of PNAS. In it, Friedman describes the results of his study as robust because the large-bodied, predatory fishes that are disproportionately devastated also have the best fossil records. “In other words, we can be convinced that these forms really do die off here, and that their disappearance can’t be chalked up to a lousy fossil record,” Friedman noted.

Nevertheless, fossil fishes are not well studied because paleontologists, as a group, tend to be drawn to other animals, such as dinosaurs. Therefore, many large-scale patterns of fish evolution remain unclear.

The fossil fishes included in the study are diverse in form, and range in length from about 20 feet to less than one inch.

“This study demonstrates that fossil datasets are germane to modern diversity and evolution by allowing us to calibrate what characteristics might relate to extinction vulnerability today,” Friedman said. “Echoes of the end-Cretaceous extinction reverberate 65 million years later”.

Doctors against papal statement on AIDS


From British medical journal The Lancet:

Redemption for the Pope?

The Vatican felt the heat from an unprecedented amount of international condemnation last week after Pope Benedict XVI made an outrageous and wildly inaccurate statement about HIV/AIDS. On his first visit to Africa, the Pope told journalists that the continent’s fight against the disease is a problem that “cannot be overcome by the distribution of condoms: on the contrary, they increase it”.

Vexed question of the Vatican’s appeasement of Hitler will overshadow Benedict’s first visit to Israel: here.