Monday, May 21 9:59 am
A close-up of a Phacops rana milleri trilobite, showing its compound eye. Courtesy of Flickr/Striving to a goal. Click to enlarge.
In the late 1960s, Curator Emeritus Niles Eldredge was a graduate student with a passion for trilobite eyes. He had been taught to expect slow and steady change between the specimens of these Devonian arthropods he collected for his dissertation. Only his trilobites were doing one of two things: staying the same, or evolving in leaps.
Several years later, Eldredge turned his observations into a theory known as “punctuated equilibria”: the idea that species stay relatively the same, or at equilibrium, throughout the fossil record save for rare bursts of evolutionary change. This year marks the 40th anniversary of the landmark 1972 paper on the theory, Punctuated Equilibria: An Alternative to Phyletic Gradualism, which Eldredge wrote with the late Stephen Jay Gould, a noted evolutionary biologist who also served as the Museum’s Frederick P. Rose Honorary Curator in Invertebrates starting in the early 1990s.
The theory was over a century in the making. In On the Origin of Species, Charles Darwin argued that species evolve slowly and gradually. With this view of evolution’s pace, he was haunted by how spotty the fossil record seemed, with its many “missing links” and lack of soft transitions between species.
Eldredge and Gould disagreed with Darwin on this point, arguing that many of the fossil record’s “gaps” reveal how evolution really works. Read more »
Wednesday, May 16 9:19 am
This CT scan of Cordylus marunguensis shows the lizard’s osteoderms, tiny bony plates of armor in the animal’s scales. © AMNH/E. Stanley. Click to enlarge.
Museum graduate student Edward Stanley recently used high-resolution x-ray images of tiny “armor” bones to help an international team of scientists discover a new species of lizard from remote, war-torn mountains in Central Africa. The lizard, Cordylus marunguensis, was found on the Marungu Plateau in the southeastern Democratic Republic of the Congo. It is described in the African Journal of Herpetology.
The new lizard was discovered on an expedition led by Eli Greenbaum, assistant professor of evolutionary genetics at the University of Texas at El Paso, and Chifundera Kusamba, a research scientist from the Centre de Recherche en Sciences Naturelles in the Congo. Suspecting that the lizard represented a new species, Greenbaum sent DNA samples and a specimen to Stanley, a third-year student in the Museum’s Richard Gilder Graduate School—the first museum program in the Western Hemisphere with the authority to grant the Ph.D. degree. Read more »
Friday, May 11 9:33 am
Jim Hellemn's photography was used to create an interactive coralscape in Creatures of Light. The brilliant patches of red, green, and orange above come from corals, fishes, and sea anemones that are fluorescent. The vivid colors only appear when the animals are illuminated by specific wavelengths of light. © Jim Hellemn, portraitofacoralreef.com
Museum Research Associate David Gruber, assistant professor at The City University of New York (CUNY), describes a diving trip in 2011.
We wanted to include a panoramic image of a magnificent coralscape in Creatures of Light: Nature’s Bioluminescence, and Bloody Bay Wall [off Little Cayman Island] was the perfect place.
But capturing Ansel Adams-like vistas are impossible under water, where sections of the light spectrum—especially reds—are absorbed within a meter. We need to get in very close to our subject and use flash photography to capture the reef ’s true color. We have to repeat this process hundreds of times over the wall face. Then, the small consecutive images are painstakingly stitched together to create a life-sized, true-color view.
Underwater photographer Jim Hellemn developed this process to create a 20-foot by 70-foot true-color image of the Bloody Bay Wall in 1999. Returning to the wall 12 years later (with the support of a National Science Foundation Connecting Research to Public Audiences grant) allowed us to overlay the images and really see the way a coral wall ages. Some of the corals are disappearing, some of the sponges have gotten huge, and some new things have taken up residence on the wall. It’s amazing.
We also wanted to apply Jim’s methods to photograph the coralscape at night to capture a phenomenon few people encounter in person or in photographs: marine biofluorescence. Read more »
Friday, May 04 9:19 am
Japanese photographer Tsuneaki Hiramatsu combined slow-shutter speed photos for stunning images of flashing fireflies. © T. Hiramatsu of digitalphoto.cocolog-nifty.com
Firefly larvae are voracious predators, feeding on snails, slugs, and earthworms and keeping ecosystems in delicate balance. Many are stocking up on food for their whole adulthood, throughout which they will never eat. Some climb trees in pursuit of arboreal snails. Others have gills like fish that allow them to dive for aquatic snails, whose shells they then use for protection like hermit crabs. In parts of Asia, a large mollusk called an apple snail has ravaged important crops such as rice, and firefly larvae are being explored as a potential form of biocontrol to protect those nations’ food supply.
“Just think how poetic it could be if we had fireflies control snails in these agricultural systems as larvae and produce entertainment as a byproduct as adults,” says Marc Branham, an entomologist at the University of Florida.
Researchers are still investigating whether firefly numbers are dwindling. “If you ask anybody out there, they will tell you that it seems like there aren’t as many fireflies out now as there were 10 or 20 or 40 years ago,” explains Branham. The lack of data on older population numbers makes verifying their decline difficult. “But it’s pretty clear that there are some locations where people used to see many fireflies, and now you don’t see any.” Read more »
Tuesday, May 01 11:01 am
Tyrannosaurus rex is part of the carnivorous groups of dinosaurs that, according to new research, maintained a stable level of biodiversity leading up to the mass extinction at the end of the Cretaceous. © AMNH/J. Brougham
Were dinosaurs already undergoing a long-term decline before an asteroid hit at the end of the Cretaceous about 65.5 million years ago? A new study led by Museum scientists gives a multifaceted answer.
The findings, published online today in the journal Nature Communications, suggest that in general, large-bodied, “bulk-feeding” herbivores were declining during the last 12 million years of the Cretaceous Period. But carnivorous dinosaurs and mid-sized herbivores were not.
“Few issues in the history of paleontology have fueled as much research and popular fascination as the extinction of non-avian dinosaurs,” said lead author Steve Brusatte, a Columbia University graduate student affiliated with the Museum’s Division of Paleontology. “Did sudden volcanic eruptions or an asteroid impact strike down dinosaurs during their prime? We found that it was probably much more complex than that, and maybe not the sudden catastrophe that is often portrayed.”
The research team, which includes Brusatte; Mark Norell, chair of the Museum’s Division of Paleontology; and scientists Richard Butler of Ludwig Maximilian University of Munich and Albert Prieto-Márquez from the Bavarian State Collection for Palaeontology, both in Germany, is the first to look at dinosaur extinction based on “morphological disparity”—the variability of body structure within particular groups of dinosaurs. Read more »
Tags: Cretaceous Period, Dinosaurs, Division of Paleontology, duck-billed dinosaur, Extinction, Mark Norell, Nature Communications, Steve Brusatte
Category: AMNH News, Biodiversity, Science, Video
