During the Cretaceous, dome-headed pachycephalosaurs roamed through what is now the Hell Creek Formation, covering parts of Montana, Wyoming, and North and South Dakota. But UCMP Curator Mark Goodwin and Museum of the Rockies Curator Jack Horner argue that there were fewer pachycephalosaur species than we thought. Mark and Jack suggest that two species, Dracorex hogwartsia and Stygimoloch spinifer, are actually juveniles and teenagers of the species Pachycephalosaurus wyomingensis. Learn about this modern day dinosaur extinction — read Mark and Jack's paper, published this week in the open access journal PLoS ONE, read the UC Berkeley News press release on the study, and watch this video!
Archive for October 2009
Sometimes, the study of basic biology can lead to technological advances, and a recent discovery about the vision of mantis shrimp is a perfect example, providing insight that could help us improve the technology inside DVD players. What is the connection? Circularly polarized light!
You're probably familiar with linearly polarized light. Fishermen often wear polarized sunglasses to reduce the glare from the water and make it easier to see the fish. Typically a ray of light vibrates randomly in all planes, referred to as e-vectors. When light reflects off water at a certain angle, only waves with certain e-vectors are reflected. A linear polarizing filter can be oriented to block those waves, allowing us to see the rest of the light that has passed through the water and is reflected by the fish below. But light can also be circularly polarized, travelling like a corkscrew, twisting either clockwise or counter-clockwise. We can’t see this property of light, but there is one animal that can!
Odontodactylus scyllarus is a stomatopod, or mantis shrimp, living in the Great Barrier Reef. Stomatopods have the most complex eyes in the animal kingdom. About a year ago, UCMP Director and Faculty Curator Roy Caldwell was part of a team of scientists who discovered that when light bounces off the hard exoskeleton of some stomatopods, that light is circularly polarized. What was particularly surprising was that the stomatopods responded to that light — they were capable of seeing circularly polarized light! What eluded Roy and others was how.
Now colleagues have discovered that the stomatopods don't see the circularly polarized light directly. Special photoreceptor cells in their eyes, called R8 cells, filter/convert the circularly polarized light into linearly polarized light, which can then be sensed by other photoreceptor cells below it. The R8 cell is quite remarkable and might serve as a model for tiny manmade dual-function microsensors.
Manmade filters that convert polarized light are called quarter-wave retarders and are effective only across a very narrow band of wavelengths. The R8 cell (acting like a quarter-wave retarder) can filter light across a wide band of wavelengths, spanning the entire visual spectrum, into the UV spectrum.
There are lots of applications for a highly effective quarter-wave retarder, including DVD players. As DVD technology advances, people are already using circularly polarized light to create 3D movies — one eye sees the clockwise corkscrews of light, and the other eye sees the counter-clockwise corkscrews (Roy received some prototype 3D glasses using this technology and used them to verify that the stomatopods were producing circularly polarized signals!). Digital cameras along with many other optical devices also include quarter-wave retarders in their sensors.
We can learn a lot about optics from the stomatopod eye, and apply this knowledge to new technologies.
Want to learn more about stomatopods? Watch the UCMP video Field notes: Collecting collecting stomatopods on the Great Barrier Reef. And check out Secrets of the Stomatopod: An Underwater Research Adventure.
Daniel Fortier visited the UCMP for two weeks this summer, investigating the taxonomy of South American crocodilians — crocodiles, caymans, and gharials. Daniel is from Brazil, where crocodiles are fairly common. He is a Ph.D. student at the Universidade Federal Do Rio Grande Do Sul in Porto Alegre, and is spending the year at the University of Iowa, in Iowa City. He is using fossils and modern skeletal materials to learn about crocodilian evolutionary history, places of origin, dispersal routes, speciation, and extinction events.
During the Miocene (from about 23 to 5 million years ago), Columbia was home to great crocodilian diversity. The UCMP has the best collection of Columbian crocodilian fossils. “Actually,” says Daniel, the UCMP “is the only one with Columbian fossils.”
This is a fossil gharial skull. Gharials (also called gavials) are a group of crocodilians with long, narrow jaws. They lived in South America during the Miocene, but are now extinct in South America. Gharials still live in parts of India. Daniel is trying to learn more about their evolution, biogeography, and extinction.
The UCMP has hosted several Flat Stanleys this year, as part of the Year of Science 2009. Flat Stanley is a fictional character from a children’s book, written by Jeff Brown in 1964. In the original story, Stanley is a little boy who is flattened when a bulletin board above his bed falls on top of him. He finds that, in his new flattened state, he is able to have many great adventures by being mailed from place to place in an envelope. Inspired by this story, the Flat Stanley project began as a classroom exercise in an elementary school in Canada and has now grown into a communication network among primary school students around the world. In a variation of this idea, students in Piedmont, California made paper Flat Stanleys and sent them to Berkeley to learn about scientific research on campus. Three of these Stanleys came to visit the UCMP.
The first Stanley to visit in 2009 was hosted by Kaitlin Maguire, a member of the Barnosky lab. Kaitlin showed Stanley the skull of a Columbian mammoth from the Pleistocene of California, and took Stanley’s photo next to one of the mammoth’s teeth. You can check out Stanley’s full adventure with Kaitlin and the mammoth here.
The next Stanley was hosted by Jann Vendetti, a member of the Hickman Lab. Jann took Stanley with her to one of the classes taught in Integrative Biology, called Principles in Paleontology. Stanley got to see a lot of invertebrate fossils, and learned how paleontologists measure the size and shape of animals in the fossil record. See Stanley’s full adventure with Jann here .
The last Stanley to visit the UCMP was hosted by Susumu Tomiya, who is also a member of the Barnosky lab. Susumu introduced Stanley to Flat Darwin, whose real-life counterpart would have celebrated his 200th birthday this year! Flat Darwin took Stanley on a grand tour of the UCMP collections, with a special emphasis on the fossil mammals of South America. One of the highlights was the glyptodont, a giant, extinct relative of the armadillo. You can read about Stanley’s visit with Susumu, Flat Darwin, and the mammals of South America here.
This isn’t the first time Flat Stanley has visited the UCMP — to read about his previous adventures, click here.
UCMP Assistant Director Mark Goodwin's research on Triceratops is featured on National Geographic Channel's video of the week. Triceratops are named for the three horns that protrude from the skull — and as Mark and his colleague Jack Horner have discovered, those three horns tell a fascinating story about the growth and development, and potentially the behavior, of these dinosaurs. The National Geographic video is an excerpt from an hour-long television program, Dinosaurs Decoded. Be sure to catch it on the National Geographic Channel on Sunday, October 11 at 9pm, and on Tuesday, October 13 at 9pm. And check out a preview of the video, along with photos and fun facts, here.
UCMP and the other Berkeley Natural History Museums are well represented on a new exhibit in the Bancroft Library — Darwin and the Evolution of a Theory. We had a special tour of the exhibit last week thanks to UCMP Faculty Curator – and exhibit co-curator – Kevin Padian.
The exhibit is stunning. There are rare books and manuscripts from the Bancroft Library and other campus collections, as well as numerous specimens, including a South American ground sloth fossil from the UCMP, Galapagos tortoise shells and finches from the Museum of Vertebrate Zoology, plant specimens from the Jepson Herbaria… the list goes on. Check out the exhibit's catalog to see more of the specimens included in the exhibit.
Kevin explained that only Berkeley could put on an exhibit like this. Only Berkeley has libraries and natural history museums with the rich collection of books, manuscripts, and specimens required to put on an exhibit of this depth. If you're in the Bay Area, make the trip to the Bancroft Library — the exhibit is open Monday through Friday from 10am – 4pm, and will be on view until December 23, 2009.
Want to learn more about Darwin? Kevin Padian will be part of a panel discussion, "Darwin's Enduring Legacy," on Wednesday, November 4 at 7pm. Look here for more information.
This week's big paleo story centers on Ardipithecus ramidus, a species of hominid that lived in the woodlands of Ethiopia, 4.4 million years ago. UCMP Faculty Curator and Human Evolution Research Center (HERC) director Tim White is co-director of the Middle Awash Project, the team of researchers that excavated and studied the fossils. The team includes UCMP Faculty Curator and HERC Associate Faculty member Leslea Hlusko. Find out more about the discovery:
Tim and his colleagues found a lot of fossil material — over 125 pieces from the skeleton of a single individual (nicknamed Ardi), as well as specimens from nearly three dozen other individuals. The teeth provide clues about the species' social structure, and the pelvis, hand, and foot bones indicate how it may have walked and climbed.
If you're on the Berkeley campus, be sure to check out HERC's exhibit on human evolution, on the second floor of the Valley Life Sciences Building at UC Berkeley. There is a new section of the exhibit about Ardipithecus ramidus.