Mass strandings of marine mammals blamed on toxic algae: Clues unearthed in ancient whale graveyard
Mass strandings of whales have puzzled people since Aristotle. Modern-day strandings can be investigated and their causes, often human-related, identified. Events that happened millions of years ago, however, are far harder to analyze — frequently leaving their cause a mystery. A team of Smithsonian and Chilean scientists examined a large fossil site of ancient marine mammal skeletons in the Atacama Desert of Northern Chile — the first definitive example of repeated mass strandings of marine mammals in the fossil record. The site reflected four distinct strandings over time, indicating a repeated and similar cause: toxic algae. The team’s findings will be published Feb. 26 in the Proceedings of the Royal Society B.
The site was first discovered during an expansion project of the Pan-American Highway in 2010. The following year, paleontologists from the Smithsonian and Chile examined the fossils, dating 6-9 million years ago, and recorded what remained before the site was paved over.
The team documented the remains of 10 kinds of marine vertebrates from the site, named Cerro Ballena — Spanish for “whale hill.” In addition to the skeletons of the more than 40 large baleen whales that dominated the site, the team documented the remains of a species of sperm whale and a walrus-like whale, both of which are now extinct. They also found skeletons of billfishes, seals and aquatic sloths.
What intrigued the team most, however, was how the skeletons were arranged. The skeletons were preserved in four separate levels, pointing to a repeated and similar underlying cause. The skeletons’ orientation and condition indicated that the animals died at sea, prior to burial on a tidal flat.
Effects of Toxic Algae
Today, toxins from harmful algal blooms, such as red tides, are one of the prevalent causes for repeated mass strandings that include a wide variety of large marine animals.
“There are a few compelling modern examples that provide excellent analogs for the patterns we observed at Cerro Ballena — in particular, one case from the late 1980s when more than a dozen humpback whales washed ashore near Cape Cod, with no signs of trauma, but sickened by mackerel loaded with toxins from red tides,” said Nicholas Pyenson, paleontologist at the Smithsonian’s National Museum of Natural History and lead author of the research. “Harmful algal blooms in the modern world can strike a variety of marine mammals and large predatory fish. The key for us was its repetitive nature at Cerro Ballena: no other plausible explanation in the modern world would be recurring, except for toxic algae, which can recur if the conditions are right.”
Harmful algal blooms are common along the coasts of continents; they are enhanced by vital nutrients, such as iron, released during erosion and carried by rivers flowing into the ocean. Because the Andes of South America are iron-rich, the runoff that has occurred along the west coast of South America for more than 20 million years has long provided the ideal conditions for harmful algal blooms to form.
From their research, the scientists conclude that toxins generated by harmful algal blooms most likely poisoned many ocean-going vertebrates near Cerro Ballena in the late Miocene (5-11 million years ago) through ingestion of contaminated prey or inhalation, causing relatively rapid death at sea. Their carcasses then floated toward the coast, where they were washed into a tidal flat by waves. Once stranded on the tidal flat, the dead or dying animals were protected from marine scavengers, and there were no large-land scavengers in South America at this time. Eventually, the carcasses were buried by sand. Because there are four layers at Cerro Ballena, this pathway from sea to land occurred four different times during a period of 10,000 to 16,000 years in the same area.
“Cerro Ballena is the densest site for individual fossil whales and other extinct marine mammals in entire world, putting it on par with the La Brea Tar Pits or Dinosaur National Monument in the U.S.,” Pyenson said. “The site preserves marine predators that are familiar to modern eyes, like large whales and seals. However, it also preserves extinct and bizarre marine mammals, including walrus-like whales and aquatic sloths. In this way, the site is an amazing and rare snapshot of ancient marine ecosystems along the coast of South America.”
3-D Technology at Cerro Ballena
Because the site was soon to be covered by the Pan-American Highway, time was very limited for the researchers. A major solution came in the form of 3-D technology. Pyenson brought a team of Smithsonian 3-D imaging experts to Chile, who spent a week scanning the entire dig site.
Although all the fossils found from 2010 to 2013 have been moved to museums in the Chilean cities of Caldera and Santiago, the Smithsonian has archived the digital data, including the 3-D scans, from the site at cerroballena.si.edu. There, anyone can download or interact with 3-D models of the fossil whale skeletons, scan Google Earth maps of the excavation quarries, look at a vast collection of high-resolution field photos and videos or take 360-degree tours of the site.
The enormous wealth of fossils that the team examined represents only a fraction of the potential at Cerro Ballena, which remains unexcavated. The scientists conservatively estimate that the entire area preserves several hundred fossil marine mammal skeletons, awaiting discovery. Pyenson’s colleagues at the Universidad de Chile in Santiago are actively working to create a research station near the fossils of Cerro Ballena so that those that have been collected and those still covered by sediments can be protected for posterity.
Remains of Extinct Giant Camel Discovered in High Arctic
Mar. 5, 2013 — A research team led by the Canadian Museum of Nature has identified the first evidence for an extinct giant camel in Canada’s High Arctic. The discovery is based on 30 fossil fragments of a leg bone found on Ellesmere Island, Nunavut and represents the most northerly record for early camels, whose ancestors are known to have originated in North America some 45 million years ago.
The fossils were collected over three summer field seasons (2006, 2008 and 2010) and are about three-and-a-half million years old, dating from the mid-Pliocene Epoch. Other fossil finds at the site suggest this High Arctic camel lived in a boreal-type forest environment, during a global warm phase on the planet.
The research by Dr. Natalia Rybczynski and co-authors including Dr. John Gosse at Dalhousie University, Halifax and Dr. Mike Buckley at the University of Manchester, England is described in the March 5, 2013 edition of the online journal Nature Communications.
“This is an important discovery because it provides the first evidence of camels living in the High Arctic region,” explains Rybczynski, a vertebrate paleontologist with the Canadian Museum of Nature, who has led numerous field expeditions in Canada’s Arctic. “It extends the previous range of camels in North America northward by about 1,200 km, and suggests that the lineage that gave rise to modern camels may been originally adapted to living in an Arctic forest environment.”
The camel bones were collected from a steep slope at the Fyles Leaf Bed site, a sandy deposit near Strathcona Fiord on Ellesmere Island. Fossils of leaves, wood and other plant material have been found at this site, but the camel is the first mammal recovered. A nearby fossil-rich locality at Strathcona Fiord, known as the Beaver Pond site, has previously yielded fossils of other mammals from the same time period, including a badger, deerlet, beaver and three-toed horse.
Determining that the bones were from a camel was a challenge. “The first time I picked up a piece, I thought that it might be wood. It was only back at the field camp that I was able to ascertain it was not only bone, but also from a fossil mammal larger than anything we had seen so far from the deposits,” explains Rybczynski, relating the moment that she and her team had discovered something unusual.
Some important physical characteristics suggested the fossil fragments were part of a large tibia, the main lower-leg bone in mammals, and that they belonged to the group of cloven-hoofed animals known as arteriodactyls, which includes cows, pigs and camels. Digital files of each of the 30 bone fragments were produced using a 3D laser scanner, allowing for the pieces to be assembled and aligned. The size of the reconstituted leg bone suggested it was from a very large mammal. At the time in North America, the largest arteriodactyls were camels.
Full confirmation that the bones belonged to a camel came from a new technique called “collagen fingerprinting” pioneered by Dr. Mike Buckley at the University of Manchester in England. Profiles produced by this technique can be used to distinguish between groups of mammals.
Minute amounts of collagen, the dominant protein found in bone, were extracted from the fossils. Using chemical markers for the peptides that make up the collagen, a collagen profile for the fossil bones was developed. This profile was compared with those of 37 modern mammal species, as well as that of a fossil camel found in the Yukon, which is also in the Canadian Museum of Nature’s collections.
The collagen profile for the High Arctic camel most closely matched those of modern camels, specifically dromedaries (camels with one hump) as well as the Yukon giant camel, which is thought to be Paracamelus, the ancestor of modern camels. The collagen information, combined with the anatomical data, allowed Rybczynski and her colleagues to conclude that the Ellesmere bones belong to a camel, and is likely the same lineage as Paracamelus.
“We now have a new fossil record to better understand camel evolution, since our research shows that the Paracamelus lineage inhabitated northern North America for millions of years, and the simplest explanation for this pattern would be that Paracamelus originated there,” explains Rybczynski. “So perhaps some specializations seen in modern camels, such as their wide flat feet, large eyes and humps for fat may be adaptations derived from living in a polar environment.”
The scientific paper also reports for the first time an accurate age of both the Fyles Leaf Bed site and the Beaver Pond site — at least 3.4 million years old. This was determined by Dr. John Gosse at Dalhousie University using a sophisticated technique that involves dating the sands found associated with the bone. The date is significant because it corresponds to a time period when Earth was 2ºC à 3ºC warmer than today, and the Arctic was 14ºC à 22ºC warmer. The bones of the High Arctic camel are housed in the Canadian Museum of Nature’s research and collections facility in Gatineau, Quebec on behalf of the Government of Nunavut.
New Fossils of Crocodilian, Hippo-Like Species from Panama
Mar. 5, 2013 — University of Florida paleontologists have discovered remarkably well-preserved fossils of two crocodilians and a mammal previously unknown to science during recent Panama Canal excavations that began in 2009.
The two new ancient extinct alligator-like animals and an extinct hippo-like species inhabited Central America during the Miocene about 20 million years ago. The research expands the range of ancient animals in the subtropics — some of the most diverse areas today about which little is known historically because lush vegetation prevents paleontological excavations — and may be used to better understand how climate change affects species dispersal today. The two studies appear online today in the same issue of the Journal of Vertebrate Paleontology.
The fossils shed new light on scientists’ understanding of species distribution because they represent a time before the formation of the Isthmus of Panama, when the continents of North and South America were separated by oceanic waters.
“In part we are trying to understand how ecosystems have responded to animals moving long distances and across geographic barriers in the past,” said study co-author Jonathan Bloch, associate curator of vertebrate paleontology at the Florida Museum of Natural History on the UF campus. “It’s a testing ground for things like invasive species — if you have things that migrated from one place into another in the past, then potentially you have the ability to look at what impact a new species might have on an ecosystem in the future.”
The research was funded by the National Science Foundation Panama Canal Partnerships in International Research and Education project, which supports paleontological excavation of the canal during construction expected to continue through 2014.
“We’re very fortunate we could get the funding for PIRE to take advantage of this opportunity — we’re getting to sample these areas that are completely unsampled,” said Alex Hastings, lead author of the crocodilian study and a visiting instructor at Georgia Southern University who conducted the research for the project as a UF graduate student.
Researchers analyzed all known crocodilian fossils from the Panama Canal, including the oldest records of Central American caimans, which are cousins of alligators. The more primitive species, named Culebrasuchus mesoamericanus, may represent an evolutionary transition between caimans and alligators, Hastings said.
“You mix an alligator and one of the more primitive caimans and you end up with this caiman that has a much flatter snout, making it more like an alligator,” Hastings said. “Before this, there were no fossil crocodilian skulls known from Central America.”
Christopher Brochu, an assistant professor of vertebrate paleontology in the department of geoscience at the University of Iowa, said “the caiman fossil record is tantalizing,” and the new data shows there is still a long way to go before researchers understand the group.
“The fossils that are in this paper are from a later time period, but some of them appear to be earlier-branching groups, which could be very important,” said Brochu, who was not involved with the study. “The problem is, because we know so little about early caiman history, it’s very difficult to tell where these later forms actually go on the family tree.”
The new mammal species researchers described is an anthracothere, Arretotherium meridionale, an even-toed hooved mammal previously thought to be related to living hippos and intensively studied on the basis of its hypothetical relationship with whales. About the size of a cow, the mammal would have lived in a semi-aquatic environment in Central America, said lead author and UF graduate student Aldo Rincon.
“With the evolution of new terrestrial corridors like this peninsula connecting North America with Central America, this is one of the most amazing examples of the different kind of paths land animals can take,” Rincon said. “Somehow this anthracothere is similar to anthracotheres from other continents like northern Africa and northeastern Asia.”
Researchers also name a second crocodilian species, Centenariosuchus gilmorei, after Charles Gilmore, who first reported evidence of crocodilian fossils collected during construction of the canal 100 years ago. The genus is named in honor of the canal’s centennial in 2014.
Researchers will continue excavating deposits from the Panama Canal during construction to widen and straighten the channel and build new locks. The project is funded by a $3.8 million NSF grant to develop partnerships between the U.S. and Panama and engage the next generation of scientists in paleontological and geological discoveries along the canal.
Study co-authors include Bruce MacFadden of UF and Carlos Jaramillo of the Smithsonian Tropical Research Institute.