Ring species are often touted as examples of speciation in action — and the Ensatina salamander, which forms a ring around California's Central Valley, is a classic example. Biologists discovered this ring species back in the 1950s, and investigations of Ensatina continue today. Learn more about Ensatina in this research profile of biologist Tom Devitt, on the UCMP's Understanding Evolution website. Tom is a graduate student in Integrative Biology here at UC Berkeley. The profile follows him from the field to the lab, from studying the morphology to investigating the molecules. Tom even does some exciting experiments on Ensatina mating behavior — be sure to check out this research profile!
Posts tagged ‘vertebrates’
Not all fossils are discovered by paleontologists combing the earth on special expeditions. Many fossils are found by accident — particularly during construction projects. Impressive fossils, like whales, mammoths, and sloths, have been found while digging foundations for buildings, leveling land for highways, and excavating subway tunnels. This spring, the UCMP blog will take you on a tour of Bay Area construction sites, past and present, to show you some of the fossils underfoot in the region.
This week, Dave Haasl, a former Museum Scientist at the UCMP, tells us about his work with PaleoResource Consultants, a consulting firm that performs what is known as mitigation paleontology. If fossils are found on public lands during construction, the law requires that they be preserved. The fossils need to be excavated quickly, so that construction can carry on. And, the fossils need to be excavated by trained paleontologists, so they are properly preserved for future scientific study. This is a job for mitigation paleontologists! As Dave explains, "we need to mitigate the impact [of construction] to scientifically important resources. This includes fossils, as well as archaeological specimens."
There are two parts to mitigation paleontology. First, the paleontologists do pre-construction field surveys. "We look at the stratigraphy of the area, and plot the potential fossil localities," says Dave. Then, when those areas are dug up, workers know to be on the lookout for fossils. The second part of paleo mitigation is monitoring, which occurs throughout a construction project. Construction workers may not recognize fossils when they come across them, so it's important to have a trained paleontologist on site. If fossils are found, the monitors halt construction and quickly excavate the fossils. They call in a network of paleontologists, and typically they are able to excavate the fossils within a few days.
Recently, two marine mammal skeletons, a whale and a dolphin, were found during the construction of a sea wall along the California coastline. Santa Cruz County is building a sea wall between Santa Cruz and Capitola, to protect the cliffs and buildings from large waves. However, the sea wall will block access to that section of the coastline, preventing any future paleontological exploration of the area. Paleontologists were asked to survey the area before the wall was built, to see if any fossils were present.
An amateur paleontologist had seen vertebrae protruding from the sandstone — these vertebrae belonged to a small whale that lived in the late Miocene, about 5 million years ago. PaleoResource Consultants excavated the specimen, wrapped it in plaster to protect it during transport, and brought it back to their offices in Auburn, California, where it is now being prepared.
A second skeleton, a dolphin, was found by Robert Boessenecker, a graduate student at Montana State University studying marine vertebrate fossils in California. The dolphin, now extinct, is also from the late Miocene, and is related to the Chinese river dolphin. "Marine mammals were much more diverse at that time," says Dave.
While Dave's career path as a paleo mitigation consultant may seem unusual, there is a real need for trained paleontologists in this field. "There is more paleo work in the West than paleontologists who can do it," he says. "Often, archaeologists do the work, because paleontologists are not available." And this work is important. As a result of big construction projects, fossil material is collected that otherwise would still be in the ground. These specimens are then used in scientific research. Says Dave, "This is our historic heritage. If it's destroyed or sealed off, we're losing something of potential scientific value. Yeah, we need roads, we need power plants. But we're going to try to preserve as much of our past as we can."
Learn more about fossils found during construction projects in upcoming blogs!
It is pretty unusual to see fish in the UCMP. It’s not that we don’t have any fish specimens — we have over a million fossilized fish fragments. It’s just that none of our museum scientists focus on fish, and so the museum’s fish parts tend to stay in the cabinets. But this past summer, Ralph Stearley of Calvin College visited the UCMP, and he did a little fishing.
Ralph pulled some spectacular specimens from the murky depths of the cabinets. The two specimens shown here are exceptional — nearly all the bones are in place, and one of the specimens even has imprints of scales! It is really rare for fish to fossilize like this — most of the time, fish break apart into individual bones and tiny scales.
These two specimens are salmonids. They are related to salmon, char, and trout — their closest living relative is probably the Dolly Varden. They lived 15-10 million years ago, in the ancient lakes that back then dotted Western Nevada. They were collected by UCMP curator Howard Hutchison in 1975, in an area called Stewart Valley. This site contains fossilized vertebrate, insect, fish, and plant material — it is rare to find so much taxonomic diversity in one place. Hutchison and his colleagues really got a sense of the entire fauna that once inhabited the area.
Ralph was excited to find these salmonid specimens in our collection — he and his collaborator, Gerald Smith of the University of Michigan, study the biogeographic history of salmonid fish. These specimens provide evidence that salmonids once lived in Western Nevada. For Ralph and Gerald, these fish are definitely keepers.
UCMP graduate student Kaitlin Maguire is working with the Children’s Discovery Museum in San Jose to develop a new exhibit about the life of Lupé, a mammoth fossil that was found in the nearby Guadalupe River. This is the second in a series of blogs about Lupé and the new exhibit. Read Kaitlin’s first Lupé blog here.
Development of the Lupé Story Exhibition is moving along quickly as exhibit ideas come to life in prototyping labs, in which the development team at the Children’s Discovery Museum (CDM) sets up preliminary exhibits and opens them up to the public for feedback. Prototyping labs are an important aspect of developing an exhibition; the prototyping labs show how children interact with the exhibits and if the exhibits are successful in teaching the children something about Lupé, paleontology, and the process of science. Maureen Callanan, a professor at UC Santa Cruz, is also interested in the prototyping labs because it gives her and her graduate students a chance to study how children learn and interact with their parents and caregivers. Maureen and her students then provide additional feedback to the CDM team from a cognitive psychology perspective. Preliminary exhibits in the first prototyping lab included bone puzzles, play dioramas of the Pleistocene, and sifting for fossils. The most popular exhibit in the first prototyping lab was the dig site where some children spent hours using wooden tools to dig out fossils of Pleistocene mammals.
In December, we all got the chance to meet Roger Castillo, the San Jose citizen who found the Lupé fossils as he was walking his puppy along the Guadalupe River. Hearing Roger tell his story about the discovery was inspirational. As a citizen scientist, he is invested in the health of the Guadalupe River and all it has to offer, including fossils. Growing up in San Jose, he has monitored the river his entire life. Specifically, he has looked at salmon populations in the river, changes in the level of the river, and erosion caused by the river.
Upon hearing Roger enthusiastically describe how he discovered the fossils, the CDM team decided to focus on recreating the “discovery moment” for children to experience at the museum. The next prototyping lab will contain exhibits designed to create an experience of discovery, excitement, and curiosity. Children will discover fossils on a riverbank, uncover them, and ask questions about the fossils much in the way Roger did. This prototyping lab will be open through the spring. A third prototyping lab will open in the fall and final production of the exhibition will start afterward leading up to the grand opening in the spring of 2011.
A few weeks ago, we blogged about the discovery of a new species of dinosaur, Tawa hallae. Two UCMP alums, Sterling Nesbitt and Randy Irmis, described this new dino in the journal Science. A few weeks ago, Sterling, Randy, and two of their Tawa co-authors, Nate Smith and Alan Turner, visited the UCMP. They've come from Texas, Utah, Illinois, and New York, to work together and delve into the UCMP's collections. Along with UCMP Faculty Curator Kevin Padian and graduate student Sarah Werning, they are looking at the fossils in old collections — dinosaurs and crocodile relatives that lived around the same time as Tawa, in what is now Arizona and New Mexico.
"We're looking at the old fossils in the context of new ones," says Randy. Many of the fossils were collected by Charles Camp in the 1930s — others were collected even before that. Quite a few were never identified and have not yet been entered in the UCMP’s database. For those specimens that were identified, says Sarah, "we're potentially re-identifying them." There are many new species that were not known when the fossils were last studied. In looking through these old collections, the team could find additional specimens of Tawa, or specimens that represent species that have not yet been described.
Their work in the collections will likely influence their field work plans this summer. They're returning to the Hayden Quarry, in New Mexico, for their 5th full season. They'll also visit nearby areas where fossils from the old collections were found, years ago. "Some of the big discoveries in paleontology have happened when you re-identify fossils that have already been collected, and then you go back to a particular area to look for more," says Nate. For example, Tiktaalik, an important fossil that represents an intermediate form between fish and amphibians, was found when paleontologists re-visited a field site in Nunavut, Canada.
The scientific community will reap some benefits as a result of this week's work. As experts in the field of Triassic dinosaurs, "we play a mini-curatorial role," says Nate. They straighten out the identities of the fossils, and they add the specimens to the database, so other researchers can access this information.
When they're not looking through the collections, the team clusters around their laptops in the Padian lab, drinking coffee and Diet Coke and bouncing ideas off each other. It's great to be all in one place, they say. Online communication is "good for getting things started and wrapping things up," says Alan, "but for the meaty part in the middle it's best to be in one place."
As more and more species go extinct, biologists wonder whether we are on the verge of the earth's sixth mass extinction. A new study, by Marc Carrasco and Tony Barnosky of the UCMP and Russell Graham of Pennsylvania State University, uses the fossil record to examine mammal biodiversity in North America over the past 30 million years. Carrasco and his collaborators used data from two fossil databases, MioMap and Faunmap, to determine the baseline of mammal diversity before humans arrived in North America. Their results, published in the journal PLoS ONE, show that the arrival of humans 13 thousand years ago coincided with a 15 to 42% decline in mammal diversity. These data show that humans had a negative impact on mammals long before we factor in the effects of current industrialization and global climate change. Now that a pre-human baseline of North American mammal diversity has been established, we can compare current diversity to the continent's "normal" diversity level — an important comparison as we plan and evaluate conservation efforts in the future.
Last week, two University of California Museum of Paleontology alums, Sterling Nesbitt and Randall Irmis, described a new species of dinosaur in the journal Science. The new species, Tawa hallae, sheds light on early dinosaur evolution — and the importance of the UCMP's collections.
Tawa's bones were first found by hikers in Ghost Ranch, New Mexico, in 2004. Around that time, Sterling and Randy were doing fieldwork at the nearby Petrified Forest National Park in northern Arizona, excavating fossils from rock layers from the Late Triassic — the same rock formation where the new fossils were found. That fall, park paleontologist Alex Downs approached Sterling and Randy at a scientific meeting and asked them if they'd be interested in excavating and describing what appeared to be a novel species. At that time, Randy was a graduate student at Berkeley, and Sterling had finished his undergrad at Berkeley and begun graduate school at Columbia. They decided to collaborate with Alex to describe the specimens and made plans to start fieldwork during the summer of 2006.
"Three weeks before our first major expedition," says Sterling, "the provost at the American Museum of Natural History called and asked if I'd like to be accompanied by an NSF-funded IMAX movie crew." They wanted to film the excavation of the fossils for a movie, Dinosaurs Alive!. Sterling was a little worried that the filming would interfere with his fieldwork, but he agreed. The film crew followed Sterling, Randy, and the rest of the team for a week and a half. Sterling needn't have worried about having enough time to do his research — there was plenty of down time. "IMAX film is expensive," he says, and the film crew spent a lot of time setting up each shot. During some of this down time, Sterling was excavating the area where the hikers had found the fossils. "That's when I hit the ankle bone of the articulated leg of what became the holotype."
Other early dinosaur fossils are not as complete or as well preserved as those of Tawa hallae. Sterling, Randy, and the team found two nearly complete skeletons, as well as bones from several other individuals. Some of the bones are so well preserved that you can see very fine details, like the places where the muscles once attached. The neck vertebrae and the bones of the braincase have small depressions with raised rims — suggesting that there were air sacs adjacent to these bones. The air sacs filled up the depressions. Modern birds have air sacs attached to their bones, which they use for respiration. As Sterling and Randy write in their paper (co-authored by Nate Smith, Alan Turner, Alex Downs, and Mark Norell), we can't know if Tawa's air sacs served a similar function. However, we do know that Tawa is the earliest dinosaur with a pneumatic skeleton.
Tawa is particularly important because it fills a gap between early carnivorous dinosaurs, found in South America (where dinosaurs are thought to have originated), and later carnivorous dinosaurs found throughout the world. Randy, Sterling, Nate, and Alan figured out where Tawa fit by comparing it to other specimens, many of which were in the UCMP's collection. "The UCMP collection was instrumental in helping us understand what was at Ghost Ranch," says Randy. Sterling also points out the importance of the museum's collections, both in this study and in his paleontological education. "I came to Berkeley for the paleo," he says. As an undergrad, "I was in the collections a couple times a week, learning anatomy, learning what the fossil record is really like."
"This project really had its genesis when we were all graduate students," says Randy. "This study speaks to what a fantastic program we have at Berkeley, that we can have such fantastic research coming out of a graduate student-led project."
Randy is now an Assistant Professor at the University of Utah, and Sterling is a post-doc at the University of Texas Austin. Both intend to continue working at Ghost Ranch — "I plan to go back for many years to come," says Randy. "It's an amazing site." And, they plan to continue working in the UCMP collections – they'll be back in January. Check the UCMP blog for an update!
Sterling and Randy are currently collaborating with UCMP graduate student Sarah Werning, Kevin Padian, Nate Smith, and Alan Turner, to examine the growth and bone histology of early dinosaurs (including Tawa) and their relatives from Ghost Ranch. Stay tuned for an upcoming blog about dinosaur bone histology in the New Year.
Sterling and Randy's work was funded by a National Geographic grant to UCMP Faculty Curator Kevin Padian and by grants from Integrative Biology, UCMP’s Welles Fund, and the UCMP Graduate Student Research Award. Learn how you can support graduate student research at the UCMP.
There has been some great news coverage about Tawa hallae. To learn more, check the National Science Foundation's Special Report: Tawa hallae – it includes an audio slide show, a press conference, and lots of photos. There is an interview with Sterling in this Science magazine podcast, and an interview with Randy in this blog from the Utah Museum of Natural History. Also check out this article from the San Francisco Chronicle.
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!
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.