Friday, January 28, 2011

Born This Day: Eugene Dubois

Eugene Dubois (Jan. 28, 1858-Dec. 16, 1940) joined the Dutch Army as a medical officer, and used spare time from his medical duties to search for fossils, first in Sumatra and then in Java. He searched on the banks of the Solo River, with two assigned engineers and a crew of convict labourers to help him. In September 1890, his workers found a human, or human-like, fossil at Koedoeng Broeboes. This consisted of the right side of the chin of a lower jaw and three attached teeth. In August 1891 he found a primate molar tooth.

Two months later and one meter away was found an intact skullcap, the fossil which would be known as Java Man. In August 1892, a third primate fossil, an almost complete left thigh bone, was found between 10 and 15 meters away from the skullcap.

In 1894 Dubois published a description of his fossils, naming them Pithecanthropus erectus (now Home erectus), describing it as neither ape nor human, but something intermediate. In 1895 he returned to Europe to promote the fossil and his interpretation. A few scientists enthusiastically endorsed Dubois' work, but most disagreed with his interpretation. Many scientists pointed out similarities between the Java Man skullcap and Neandertal fossils.

Around 1900 Dubois ceased to discuss Java Man, and hid the fossils in his home while he moved on to other research topics. geology and paleontology. It was not until 1923 that Dubois, under pressure from scientists, once again allowed access to the Java Man fossils. That and the discovery of similar fossils caused it to once again become a topic of debate.

Skull cap (Trinil 2, holotype of Home erectus) from HERE.

Thursday, January 27, 2011

T. rex: Hunter!

Intra-guild competition and its implications for one of the biggest terrestrial predators, Tyrannosaurus rex. 2011. C. Carbone, et al. Proceedings of the Royal Society B, published online in Jan. 26.

Metal Men © DC Comics
Abstract: Identifying tradeoffs between hunting and scavenging in an ecological context is important for understanding predatory guilds. In the past century, the feeding strategy of one of the largest and best-known terrestrial carnivores, Tyrannosaurus rex, has been the subject of much debate: was it an active predator or an obligate scavenger?

Here we look at the feasibility of an adult T. rex being an obligate scavenger in the environmental conditions of Late Cretaceous North America, given the size distributions of sympatric herbivorous dinosaurs and likely competition with more abundant small-bodied theropods.

We predict that nearly 50% of herbivores would have been within a 55–85 kg range, and calculate based on expected encounter rates that carcasses from these individuals would have been quickly consumed by smaller theropods. Larger carcasses would have been very rare and heavily competed for, making them an unreliable food source.

The potential carcass search rates of smaller theropods are predicted to be 14–60 times that of an adult T. rex. Our results suggest that T. rex and other extremely large carnivorous dinosaurs would have been unable to compete as obligate scavengers and would have primarily hunted large vertebrate prey, similar to many large mammalian carnivores in modern-day ecosystems.

Died This Day: Adan Sedgwick

From Today In Science History:

Sedgwick (March 22, 1785 - January 27, 1873) was an English geologist who first applied the name Cambrian to the geologic period of time, now dated at 570 to 505 million years ago. In 1818 he became Woodwardian Professor of Geology at Cambridge, holding a chair that had been endowed ninety years before by the natural historian John Woodward.

He lacked formal training in geology, but he quickly became an active researcher in geology and paleontology. Many years after Sedgwick's death, the geological museum at Cambridge was renamed the Sedgwick Museum of Geology in his honor. The museum is now part of the Department of Earth Sciences at Cambridge University

Wednesday, January 26, 2011

Direct Dating of Dinosaur Fossils

Direct U-Pb dating of Cretaceous and Paleocene dinosaur bones, San Juan Basin, New Mexico. 2011. J. E. Fassett et al., Geology 39 :159-162

Abstract: Vertebrate fossils have been important for relative dating of terrestrial rocks for decades, but direct dating of these fossils has heretofore been unsuccessful. In this study we employ recent advances in laser ablation in situ U-Pb dating techniques to directly date two dinosaur fossils from the San Juan Basin of northwestern New Mexico and southwestern Colorado, United States.

A Cretaceous dinosaur bone collected from just below the Cretaceous-Paleogene interface yielded a U-Pb date of 73.6 ± 0.9 Ma, in excellent agreement with a previously determined 40Ar/39Ar date of 73.04 ± 0.25 Ma for an ash bed near this site.

The second dinosaur bone sample from Paleocene strata just above the Cretaceous-Paleogene interface yielded a Paleocene U-Pb date of 64.8 ± 0.9 Ma, consistent with palynologic, paleomagnetic, and fossil-mammal biochronologic data.
This first successful direct dating of fossil vertebrate bone provides a new methodology with the potential to directly obtain accurate dates for any vertebrate fossil.

Mystery In Space © DC Comics

Born This Day: Roy Chapman Andrews

Photo from Parade of Life Through The Ages, by Charles Knight, Nat. Geo., Feb. 1942.

From the American Museum of Natural History web site:

Adventurer, administrator, and Museum promoterAndrews (Jan. 26, 1884 – March 11, 1960) spent his entire career at the American Museum of Natural History, where he rose through the ranks from departmental assistant, to expedition organizer, to Museum director.

He became world famous as leader of the Central Asiatic Expeditions, a series of expeditions to Mongolia that collected, among other things, dinosaur eggs. Although on these expeditions, Andrews himself found few fossils, and during his career he was not known as an influential scientist, he instead filled the role of promoter, creating immense excitement and successfully advancing the research and exhibition goals of the museum.

Learn about the Roy Chapman Andrews Society HERE.

Read his comic book bio

Tuesday, January 25, 2011

Linhenykus monodactylus: First Single-Fingered Dinosaur

A monodactyl nonavian dinosaur and the complex evolution of the alvarezsauroid hand. 2011. X. Xu, et al. PNAS, Published online before print January 24

A new species of parrot-sized dinosaur, the first discovered with only one finger, has been unearthed in Inner Mongolia, China. Linhenykus monodactylus is named after the nearby city of Linhe.
The new dinosaur belongs to the Alvarezsauroidea, a branch of the carnivorous dinosaur group Theropoda. Theropods gave rise to modern birds and include such famous dinosaurs as Tyrannosaurus and Velociraptor.

The fossil comes from the Upper Cretaceous Wulansuhai Formation (84-75Ma), located near the border between Mongolia and China. The authors uncovered a partial skeleton from the site, which included bones of the vertebral column, the forelimb, a partial pelvis and nearly complete hind limbs.

The new theropod is unusual in having just one large claw, which may have been used to dig into insect nests, on each of its hands. The presence of only one finger in Linhenykus shows that these vestigial fingers were not present in all members of the group. The reasons for the loss of the two outer fingers in Linhenykus are unclear, and their disappearance may simply reflect the fact that they were no longer being actively maintained by natural selection. link

Born This Day: Theodosius Dobzhansky

Dobzhansky (Jan.25, 1900–Dec. 18, 1975) is noted for being one of the architects of the modern Synthetic Theory of evolution. During the first 20 years of the 20th century, Darwin's theory of natural selection had fallen out of favor among scientists. Many thought it insufficient to explain the origin of adaptations, while new discoveries of gene mutations seemed to them to be incompatible with Darwinian models of change.

But in 1937 Dobzhansky published his book, Genetics and the Origin of Species, that was the first systematic overview view encompassing organic diversity, variation in natural populations, selection, isolating mechanisms (a term he coined) and species as natural units.

Later, working with Sewall Wright, he went on to demonstrate how evolution can produce stability and equilibrium in populations rather than constant directional change. link. image.

Eodramaeus: Dawn Runner

A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea. R. Martinez, et al. Science 331: 206-210.

Abstract: Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and bracket the formation with 40Ar/39Ar ages. Some 230 million years ago in the Late Triassic (mid Carnian), the earliest dinosaurs were the dominant terrestrial carnivores and small herbivores in southwestern Pangaea. The extinction of nondinosaurian herbivores is sequential and is not linked to an increase in dinosaurian diversity, which weakens the predominant scenario for dinosaurian ascendancy as opportunistic replacement.

Plus: Researchers have discovered a new dinosaur, Eodramaeus, which lived during the dawn of the dinosaur era, about 230 million years ago. The Eodramaeus' fossils were discovered in the Ischigualasto formation in northeastern Argentina, where paleontologists have found other important dinosaur fossils.

Eoraptor, generally considered a theropod as well, is in fact an early ancestor of the sauropod lineage, which includes the giant, long-necked herbivores, the researchers say.

Eodramaeus had more theropod-like features in its skull, such as an opening near the end of the snout called the promaxillary fenestra, as well as other theropod-like features in its trunk pelvis and limbs, the authors report. Eoraptor not only lacked those features but also had more sauropod-like features, including enlarged nostrils and an inset first lower tooth.

Nonetheless, both species were less than 2 meters long and ran on two legs, and these general similarities suggest that the three principal groups of dinosaurs (the ornithischians, the sauropodomorphs and the theropods) did share an overall body plan in the late Triassic, before the dinosaurs rose to dominance in the early Jurassic, according to Dr. Martinez and his colleagues. link

Monday, January 24, 2011

Darwinopterus With An Egg

An Egg-Adult Association, Gender, and Reproduction in Pterosaurs. 2011. Junchang Lü, et al. Science 331: 321-324.

Male (right) and female Darwinopterus. Art: Mark Witton
A specimen of the pterosaur genus Darwinopterus preserved with an egg links gender with sexually dimorphic characters.
The new discovery, christened "Mrs T" (a contraction of "Mrs Pterodactyl") by the research team, was made in Jurassic rocks of Liaoning Province in northeast China and seems to represent a tragic accident. The well developed shell shows that Mrs T was just about ready to lay her egg (below) when she was killed in an accident that broke her left forearm, possibly the result of a storm, or perhaps even a volcanic eruption, which were common in this part of China around 160 million years old.

The fossil shows two features that distinguish it from male individuals of Darwinopterus. She has relatively large hips, to accommodate the passage of eggs, but no head crest. Males, on the other hand, can be assumed to have relatively small hips and a well developed head crest.

The egg is relatively small and had a soft shell. This is typical of reptiles, but completely different from birds which lay relatively large hard-shelled eggs. This discovery is not surprising though, because a small egg would require less investment in terms of materials and energy – a distinct evolutionary advantage for active energetic fliers such as pterosaurs and perhaps an important factor in the evolution of gigantic species such as the 10 meter wingspan Quetzalcoatlus."

The Smoking Gun For The Permian Extinction

Catastrophic dispersion of coal fly ash into oceans during the latest Permian extinction. 2011. S. E. Grasby. Nature Geoscience, published online Jan 23.
23 January 2011

About 250 million years about 95 per cent of life was wiped out in the sea and 70 per cent on land. Researchers have now discovered evidence to support massive volcanic eruptions burnt significant volumes of coal, producing ash clouds that had broad impact on global oceans.

Unlike end of dinosaurs, 65 million years ago, where there is widespread belief that the impact of a meteorite was at least the partial cause, it is unclear what caused the late Permian extinction. Previous researchers have suggested massive volcanic eruptions through coal beds in Siberia would generate significant greenhouse gases causing run away global warming.

Grasby and colleagues discovered layers of coal ash in rocks from the extinction boundary in Canada's High Arctic.

"This could literally be the smoking gun that explains the latest Permian extinction," says Dr. Steve Grasby.

The location of volcanoes, known as the Siberian Traps, are now found in northern Russia, centred around the Siberian city Tura and also encompass Yakutsk, Noril'sk and Irkutsk. They cover an area just under two-million-square kilometers, a size greater than that of Europe. The ash plumes from the volcanoes traveled to regions now in Canada's arctic where coal-ash layers where found. link

Premiered This Day (1956): The Animal World

“2 Billion Years in the Making!”

Produced and directed by Irwin Allen, whose long career included such TV hits as Lost In Space and Voyage To The Bottom Of The Sea, and movies like The Poseidon Adventure and The Towering Inferno.

The Animal World was one of the first films to present dinosaurs in the quasi-nature documentary so beloved by the Discovery Channel today. Rarely seen now, it featured about 10 minutes of great dinosaur stop-animation by Ray Harryhausen with Willis O’Brien. The entire sequence was released as an extra on the 2003 DVD release of The Black Scorpion.

Tuesday, January 11, 2011

Ammonites Dined On Plankton

The Role of Ammonites in the Mesozoic Marine Food Web Revealed by Jaw Preservation. I. Kruta, et al. Science 331: 70-72.

Powerful new synchrotron scans of Baculites fossils suggests that the extinct group of marine invertebrates to which they belong, the ammonites, had jaws and teeth adapted for eating small prey floating in the water.
One ammonite also provided direct evidence of a planktonic diet because it died with its last meal in its mouth—tiny larval snails and crustacean bits.
Ammonites are extinct relatives of the squid and octopus; the Nautilus is similar in appearance to many ammonites but is a more distant relative. Ammonites appeared about 400 million years ago (the Early Devonian) and experienced an explosive radiation in the early Jurassic.

Ammonite jaws lie just inside the body chamber. New scans of Baculites, a straight ammonite found worldwide, confirms older research that ammonites had multiple cusps on their radula, a kind of tongue covered by teeth that is typical of mollusks. The radula can now be seen in exquisite detail: the tallest cusp is 2 mm high, tooth shape varies from saber to comb-like, and teeth are very slender. The jaw is typical of the group of ammonites (the aptychophorans) to which Baculites, belongs.

"Our research suggests several things. First, the radiation of aptychophoran ammonites might be associated with the radiation of plankton during the Early Jurassic," says Landman. "In addition, plankton were severely hit at the Cretaceous-Tertiary boundary, and the loss of their food source probably contributed to the extinction of ammonites." link

Thursday, January 06, 2011

Born This Day: George Ledyard Stebbins

From the U Calif., Berkeley:

Along with Dobzhansky (1900 - 1975), animal systematist Ernst Mayr, and paleontologist George Gaylord Simpson (1902 - 1984), Stebbins (Jan. 6, 1906 - Jan. 19 2000) is considered one of the "architects" of the modern evolutionary synthesis of the 1930s and 1940s, an intellectual watershed and historic turning point that brought together research in cytology, genetics, systematics, paleontology into a common evolutionary framework. This synthesis, which had the effect of reconciling the often opposing views of laboratory-oriented geneticists and natural history oriented systematists, made Charles Darwin's theory of evolution by natural selection the centerpiece of the new discipline of evolutionary biology.

In this role, Stebbins is credited with bringing a modern framework to the study of plant evolution, and he is perhaps best known for his book Variation and Evolution in Plants, published by Columbia University Press (NY) in 1950. In the 1940s, Stebbins also played an important role in organizing the nascent Society for the Study of Evolution, of which he became the third president in 1948, and used his position to speak out for the botanical side of evolutionary studies, a field that had been dominated by zoologists. Photo .

Died This Day: Gregor Mendel

From Today In Science History:

Mendel (July 22, 1822 – Jan. 6, 1884) was an Austrian pioneer in the study of heredity. He spent his adult life with the Augustinian monastery in Brunn, where as a geneticist,
botanist and plant experimenter, he was the first to lay the mathematical foundation of the science of genetics, in what came to be called Mendelism.

Over the period 1856-63, Mendel grew and analyzed over 28,000 pea plants. He carefully studied for each their plant height, pod shape, pod color, flower position, seed color, seed shape and flower color. He made two very important generalizations from his pea experiments, known today as the Laws of Heredity. Mendel coined the present day terms in genetics: recessiveness and dominance.