Abundant dinosaur footprints in Alaska reveal that high-latitude hadrosaurs preferred tidally influenced habitats, according to a study published in the open-access journal PLOS ONE by Anthony Fiorillo of the Perot Museum of Nature and Science in Texas and colleagues.
Hadrosaur double prints [Credit: Fiorillo et al, 2019]
Dinosaur fossils are well-known from Alaska, most famously from areas like Denali National Park and the North Slope, but there are very few records of dinosaurs from the Alaskan Peninsula in the southwest part of the state. In this study, Fiorillo and colleagues document abundant dinosaur trackways from Aniakchak National Monument, around 670km southwest of Anchorage.
The trackways were preserved in the Chignik Formation, a series of coastal sediment deposits dating back to the Late Cretaceous Period around 66 million years ago. Survey work from 2001-2002 and 2016-2018 identified more than 75 trackway sites including dozens of dinosaur footprints.
Based on the anatomy of the prints, the authors identified two footprints of armored dinosaurs, one of a large predatory tyrannosaur, and a few footprints attributable to two types of birds. The remaining 93% of the trackways belonged to hadrosaurs, highly successful herbivores which are typically the most common dinosaurs in high-latitude fossil ecosystems.
Previous research on skeletal dinosaur remains in northern Alaska has found that hadrosaurs were most abundant in coastal habitats. The trackways documented in this study reveal that the same trend was true in southern Alaska. The authors suggest that understanding habitat preferences in these animals will contribute to understanding of how ecosystems changed through time as environmental conditions shifted and dinosaurs migrated across northern corridors between continents.
Fiorillo adds, "Our study shows us something about habitat preferences for some dinosaurs and also that duck-billed dinosaurs were incredibly abundant. Duck-billed dinosaurs were as commonplace as cows, though given we are working in Alaska, perhaps it is better to consider them the caribou of the Cretaceous."
The first humans in North America arrived from Asia some time before 14,500 years ago. The next major stream of gene flow came about 5000 years ago, and is known to archaeologists as Paleo-Eskimos. About 800 years ago, the ancestors of the present-day Inuit and Yup'ik people replaced this population across the Arctic. By about 700 years ago, the archaeological evidence for the Paleo-Eskimo culture disappeared. Their genetic legacy in living populations has been contentious, with several genetic studies arguing that they made little contribution to later North Americans.
An ancient population of Arctic hunter-gatherers, known as Paleo-Eskimos, made a significant genetic contribution to populations living in Arctic North America today [Credit: Kerttu Majander, Design by Michelle O'Reilly]
In the current study, researchers generated genome-wide data from 48 ancient individuals and 93 modern individuals from Siberia, Alaska, the Aleutian Islands and Canada, and compared this with previously published data. The researchers used novel analysis methods to create a comprehensive model of population history that included many ancient and modern groups to determine how they might be related to each other.
"Our study is unique, not only in that it greatly expands the number of ancient genomes from this region, but because it is the first study to comprehensively describe all of these populations in one single coherent model," states Stephan Schiffels of the Max Planck Institute for the Science of Human History.
The researchers were able to show that a substantial proportion of the genetic heritage of all ancient and modern American Arctic and Chukotkan populations comes from Paleo-Eskimos. This includes people speaking Eskimo-Aleut languages, such as the Yup'ik, Inuit and Aleuts, and groups speaking Na-Dene languages, such as Athabaskan and Tlingit speakers, in Canada, Alaska, and the lower 48 states of the United States.
The excavation of the Middle Dorset individual from the Buchanan site on southeastern Victoria Island, Nunavut, Central Canadian Arctic [Credit: T. Max Friesen]
Based on the researchers' analysis, Paleo-Eskimos interbred with people with ancestry similar to more southern Native peoples shortly after their arrival to Alaska, between 5,000 and 4,000 years ago. The ancestors of Aleutian Islanders and Athabaskans derive their genetic heritage directly from the ancient mixture between these two groups.
The researchers also found that the ancestors of the Inuit and Yup'ik people crossed the Bering Strait at least three times: first as Paleo-Eskimos to Alaska, second as predecessors of the Old Bering Sea archaeological culture back to Chukotka, and third to Alaska again as bearers of the Thule culture. During their stay in Chukotka that likely lasted for more than 1000 years, Yupik and Inuit ancestors also admixed with local groups related to present-day Chukchi and local peoples from Kamchatka.
Paleo-Eskimo ancestry is particularly widespread today in Na-Dene language speakers, which includes Athabaskan and Tlingit communities from Alaska and northern Canada, the West Coast of the United States, and the southwest United States.
Attu Island, Aleutian Islands, Alaska [Credit: Jason Rogers]
"For the last seven years, there has been a debate about whether Paleo-Eskimos contributed genetically to people living in North America today; our study resolves this debate and furthermore supports the theory that Paleo-Eskimos spread Na-Dene languages," explains David Reich of Harvard Medical School and the Howard Hughes Medical Institute.
"One of the most striking case examples from our study is the ancient DNA we generated from the ancient Athabaskan site of Tochak McGrath in interior Alaska, where we worked in consultation with the local community to obtain data from three approximately seven hundred year old individuals. We found that these individuals, who lived after the time when the Paleo-Eskimo archaeological culture disappeared across North America, are well modeled as a mixture of the same two ancestry components as those found in Athabaskans today, and derived more than 40% of their ancestry from Paleo-Eskimos.
The researchers hope that the paper will provide an example of the value of genetic data, in the context of archaeological knowledge, to resolve long-standing questions.
"Determining what happened to this population was not possible from the archaeological record alone," explains Pavel Flegontov of the University of Ostrava. "By analyzing genetic data in concert with the archaeological data, we can meaningfully improve our understanding of the prehistory of peoples of this region. We faced challenging analytical problems due to the complex sequence of gene flows that have shaped ancestries of peoples on both sides of the Bering Strait. Reconstructing this sequence of events required new modelling approaches that we hope may be useful for solving similar problems in other regions of the world."
A mass die-off of seabirds in the Bering Sea may be partially attributable to climate change, according to a new study publishing in the open-access journal PLOS ONE by Timothy Jones of the citizen science program COASST at University of Washington, Lauren Divine from the Aleut Community of St Paul Island Ecosystem Conservation Office, and colleagues. The birds appeared to have died from the effects of starvation.
Credit: Public Domain Pictures
Tufted puffins breeding in the Bering Sea, off the coast of Alaska, feed on fish and marine invertebrates, which in turn feed on ocean plankton. Elevation of sea temperatures has led to major changes in ocean ecosystems, and has been linked to previous mass mortality events in marine birds. Beginning in 2014, increased atmospheric temperatures and decreased winter sea ice led to declines in energy-rich prey species in the Bering Sea, as well as a shift of some species more northward, diminishing puffin food resources in the southern portion of the sea.
In the current study, Jones and colleagues documented a four-month-long die-off of puffins and a second species, the Crested auklet, on St. Paul Island, one of the Pribilof Islands in the southern Bering Sea, about 300 miles east of the mainland. Beginning in October 2016, tribal and community members recovered over 350 severely emaciated carcasses, mostly adults in the process of molting, a known nutritional stressor during the avian life cycle.
Nineteen tufted puffins found on North Beach, St. Paul, Pribilof Islands, Alaska, on Oct. 19, 2016 [Credit: Aleut Community of St Paul Island Ecosystem Conservation Office]
A reduction in food resources before entering molt may have prevented many birds from surviving, the authors suggest. Using wind data to model beachings, they calculated between 3,150 and 8,500 birds could have died in the event. Tufted puffins comprised 87% of this total, or 40-100% of the Pribilofs Islands' population, making it highly likely that affected birds originated from colonies throughout the Bering Sea. In comparison, puffins have made up less than 1% of recovered carcasses in the region in prior years.
The authors suggest that climate-driven shifts in prey abundance and/or distribution, combined with the onset of molt, may have caused this puffin die-off, and note that further climate variability in this region is probable. Further research and observation will show whether seabirds can remain resilient in an increasingly variable environment.
Divine adds: "This paper is a successful application of citizen science in the real world. Island residents collected high quality data in real time and provided COASST with a detailed context for their analysis. Without the positive and mutually beneficial relationship built over years of collaboration, this massive die-off of Tufted Puffins would have gone unreported in the scientific community."
The first artifact - a wooden mask - was discovered in 2007 by a child who stumbled upon it while playing on the beach near his home in Quinhagak, a village in western Alaska that sits by the Bering Sea.
Yupik Eskimo artifacts found at an excavation site near Quinhagak, a village in western Alaska that sits by the Bering Sea [Credit: Mark Ralston/AFP]
Over the following months, hundreds of similar objects -- baskets, finely carved harpoon shafts, lip plugs, wooden dolls, ivory tattoo needles -- emerged from the earth as melting permafrost and erosion driven by climate change revealed a Yupik Eskimo settlement dating back to the 1600s.
Today, more than a decade after the first find, an extraordinary collection of some 100,000 prehistoric Yupik artifacts -- the largest such collection in the world -- sits in a small newly opened museum in Quinhagak, home to an indigenous community of about 700 people.
"This is by far the highlight of everything I've ever excavated in my 40-year-career -- and I've worked on some pretty spectacular sites," said Rick Knecht, an archaeologist with the University of Aberdeen in Scotland.
For the past 10 years Knecht has led a team racing to save as many items as possible at the excavation site about three miles (4.8 kilometers) from Quinhagak and dubbed Nunalleq, which means Old Village in the Yupik language.
Archaeologist Rick Knecht has spent 10 years racing to save as many items as possible at the Nunalleq excavation site in western Alaska that revealed a Yupik Eskimo settlement dating back to the 1600s [Credit: Mark Ralston/AFP]
"Almost everything we know about Yupik prehistory comes from this site," said Knecht, an affable man with a grizzled beard, as he surveyed the area recently with an AFP team.
"If we'd lost it, the people here would have lost their past and a tangible link to that past, which would have been an unbelievable tragedy."
But while Knecht marvels at the trove of artifacts discovered at Nunalleq and the clues these objects have provided to traditional Yupik culture, he is also horrified that similar sites across Alaska are probably disappearing as the frozen ground that has preserved them for centuries thaws and erosion sweeps them away.
"As the permafrost melts, you can see that the soil liquefies. It's like a box of ice cream," Knecht said, pointing to the gooey mud along the fast-eroding shoreline in Quinhagak and large clumps of earth ready to topple into the sea."
An extraordinary collection of some 100,000 prehistoric Yupik artifacts - the largest such collection in the world - sits in a small newly opened museum in Quinhagak, Alaska home to an indigenous community of about 700 people [Credit: Mark Ralston/AFP]
"We've only saved this one site but tens of thousands like it are being lost right now while we're talking because of climate change," he said. "In some places in the Arctic, the coastline has gone back more than a mile. And since I've been here in Quinhagak, it's gone back 10 to 20 meters in merely 10 years."
Knecht became involved with the excavation project in 2009 after Warren Jones, a village leader, contacted him, desperate to salvage what remains of his people's past.
Based on carbon dating of organic material at Nunalleq, experts believe the site dates back to a time historians call the Bow and Arrow Wars, when Yupik communities were engaged in fierce warfare and before Russian explorers discovered Alaska in the early 1800s.
"This was our heritage and we had to preserve it," recalls Jones. "We couldn't let it get lost at sea."
Local Yupik Eskimo children look at artifacts from their ancestors, found at the Nunalleq excavation site in western Alaska [Credit: Mark Ralston/AFP]
But getting village elders who believe ancestral sites should not be disturbed to agree was no easy task.
"It took Warren Jones two years to talk the village, person by person, into allowing an archaeological project," Knecht said. "They thought long and hard about it and some of the elders who were reluctant are now our strongest supporters."
Many village residents now volunteer every summer to join Knecht and his crew of fellow archaeologists and students as they sift through the earth to save what they can.
"You get this terrible feeling of working against time and you realize the full scope of the cultural tragedy that is part of climate change," said Knecht. "It's grim, it really is grim. It's a horror show.
Based on carbon dating, experts believe the Nunalleq site dates back to a time historians call the Bow and Arrow Wars, when Yupik communities were engaged in fierce warfare and before Russian explorers discovered Alaska in the early 1800s [Credit: Mark Ralston/AFP]
"For every beautifully preserved mask lifted out of the ground, there are thousands falling to the sea in other still undiscovered sites that no one will ever see."
But against the grim backdrop of climate change, one positive side effect has been renewed interest among the Yupik people in the practices and traditions of their ancestors.
A number of villagers in Quinhagak are carving replicas of the artifacts found at Nunalleq, students at the local school have set up a traditional dance troupe and many have started to learn the Yupik language.
Not to mention the immense pride felt by the locals at having a spectacular collection that would be the envy of world-class museums.
"This has had a lot of impact on this small community," Jones said. "And it's important the collection stay in Quinhagak," he added. "These objects belong to the community. But we're willing to share and send them out to museums on loan so that other people learn about us."
Hundreds of harbor seals live in Iliamna Lake, the largest body of freshwater in Alaska and one of the most productive systems for sockeye salmon in the Bristol Bay region.
One of the Iliamna Lake seals seen just off a gravel beach on the east end of the lake, the seals' primary habitat [Credit: Jason Ching/University of Washington]
These lake seals are a robust yet highly unusual and cryptic posse. Although how the seals first colonized the lake remains a mystery, it is thought that sometime in the distant past, a handful of harbor seals likely migrated from the ocean more than 50 miles (80 kilometers) upriver to the lake, where they eventually grew to a consistent group of about 400. These animals are important for Alaska Native subsistence hunting, and hold a top spot in the lake's diverse food web.
Scientists now know these "colonizing" seals must have found the lake suitable enough to stay and raise their offspring. Generations later, the lake-bound seals appear to be a genetically distinct population from their ocean-dwelling cousins -- even though they are still managed as part of the larger Eastern Pacific harbor seal population.
But if the lake seals are distinct and show signs of local adaptation to their unique ecological setting, this would mean that their conservation -- especially in the face of the rapidly changing climate of western Alaska and proposed industrial developments -- should differ from that of nearby marine populations.
Lifelong chemical records stored in their sequentially growing canine teeth show that the Iliamna Lake seals remain in freshwater their entire lives, relying on food sources produced in the lake to survive. In contrast, their relatives in the ocean are opportunistic feeders, moving around to the mouths of different rivers to find the most abundant food sources, which includes a diverse array of marine food items in addition to the adult salmon returning to Bristol Bay's nine major watersheds. These findings are described in a paper published online in Conservation Biology.
Five seals rest on the frozen surface of Iliamna Lake in Alaska [Credit: Dave Withrow]
"We clearly show these seals are in the lake year-round, throughout their entire lives," said lead author Sean Brennan, a postdoctoral researcher at the University of Washington's School of Aquatic and Fishery Sciences. "This gives us critical baseline information that can weigh in on how we understand their ecology, and we can use that information to do a better job developing a conservation strategy."
This new study comes at a time when federal agencies are considering whether to permit mining activities in Bristol Bay, a region teeming with wildlife, including Alaska sockeye salmon. Iliamna Lake, and the seals and other animals that live there, is located in the heart of the proposed Pebble Mine project.
The U.S. Army Corps of Engineers this spring released a draft environmental impact statement that analyzes the project's proposal, presents alternative plans and gives the public a chance to comment. Ultimately, the document will help decide whether the controversial mine is approved.
Because of their current conservation status, the Iliamna Lake harbor seals aren't assessed as a distinct and ecologically significant population in the project's draft environmental impact analysis. If the seals are determined to be a distinct population, that has important implications for how the Iliamna Lake system is managed, the study's authors said. The lake and its resident fishes would then be considered critical habitat for seals.
Iliamna Lake, Alaska's largest freshwater lake, is situated in the Bristol Bay region. The islands on the east end of the lake are the seals' primary habitat [Credit: Jason Ching/University of Washington]
Separately, federal regulators have considered whether the lake seals should be named a distinct population, but scientists have been unable to agree on whether the seals are both distinct, and ecologically and evolutionarily significant, mainly because little is known about their ecology -- including whether adult lake seals potentially migrate to the ocean to feed each year.
Brennan was a doctoral student at the University of Alaska Fairbanks when he heard about early efforts to evaluate whether the lake seals were a distinct population. Chemical tracing methods he was using to track the life patterns of salmon could also work for the seals, he realized.
"The light just went off in my head," Brennan said. "What I was doing for salmon was directly applicable to this population of seals."
Brennan and collaborators at the UW, University of Utah and University of Alaska Anchorage looked at the chemical signatures present in the teeth of lake seals during each year of their life to better understand where they moved and what they ate. Specifically, the scientists drilled into the growth lines of the seals' canine teeth, then measured the ratio of heavy and light isotopes of carbon, oxygen, and strontium present in each growth layer.
Rainbow trout (front) and sockeye salmon are seen in Iliamna Lake. The new study shows that the diverse resident fish community in the lake are the principal prey of seals [Credit: Jason Ching/University of Washington]
Because of the young bedrock geology of the Kvichak (QUEE-jak) River watershed, which encompasses Iliamna Lake, strontium isotope levels in the ocean are consistently much higher than in the lake. Unlike other elements, strontium signatures in mammal teeth directly reflect what animals assimilate from their environment, in particular, what they eat. Therefore, by looking at the strontium isotope ratios over the course of a seal's life, the researchers saw that the ratios were consistent with lake signatures -- meaning these seals only live in Lake Iliamna, depend principally on fish produced within the lake, and do not migrate to the ocean.
They also determined that young seals eat very little adult sockeye salmon. But later in life, the seals shift to supplement their diets with the seasonally abundant sockeye salmon that return each summer to the lake.
The researchers say this method could be used to better understand the life patterns of other elusive mammals around the world, such as river dolphins in the Amazon or the Mekong Basin. Broadly, marine mammals in coastal regions are among the most endangered animals on Earth, Brennan said.
"In terms of the broader picture of aquatic mammal conservation across the globe, I think we show that strontium isotopes can be really powerful because they collapse a lot of uncertainty. This method is completely underutilized across the world," Brennan said.
Evidence of historic marine life present in Alaskan permafrost is helping scientists reconstruct ancient changes in the ice cover over the Arctic Ocean.
A section of an ice wedge extracted from the northern Alaskan tundra is providing insight on the region's geological history [Credit: Yoshinori Iizuka, Hokkaido University]
Hokkaido University researchers and colleagues have found that the Beaufort Sea, on the margin of the Arctic Ocean, was not completely frozen over during the coldest summers of the late Ice Age, some 12,800 years ago. Their methodology, using ice wedges from the Alaskan permafrost, could help scientists further reconstruct historic sea-ice conditions in the Arctic Ocean, and thus improve forecasts for the future.
Scientists have long studied ice core samples from large permanent ice masses in the Antarctic ice sheet around the South Pole, and in Greenland near the North Pole. These samples contain relics from our climate's distant past, such as ions, dust particles, sea salts, volcanic ash and air bubbles, which can give us information on how Earth's climate has changed over thousands and thousands of years.
Now, a research team led by Yoshinori Iizuka of Hokkaido University's Institute of Low Temperature Science has found a way to investigate the geological history of areas near the north Arctic sea, which had previously been difficult using standard methods.
This map shows the current sea level around the Arctic region, with BIWS indicating the location of the ice wedges near Barrow, Alaska. Map provided by the Japan consortium for Arctic Environmental Research [Credit: Iizuka Y. et al. 2019]
Permafrost is a layer of frozen ground present under the tundra of high northern latitudes in areas such as Russia, Canada, and Alaska. It contains massive wedges of ice that form when meltwater freezes in underground cracks. Iizuka and his team investigated ion concentrations in an ice wedge sample collected near the city of Barrow in northern Alaska. Another group dated this ice wedge back in 2010 to belonging to the late Pleistocene period, which represents the latter end of the last Ice Age some 14,400 to 11,400 years ago.
The team tested the levels of several ions in the ice wedge, including calcium sulphate, sodium, chloride, and bromide. Significantly, they determined that methanesulfonate (MS) ions in the wedge reliably indicated marine life activity, as they originated from oxidized dimethyl sulphide, a compound produced by plankton and ice algae attached to seasonal sea ice in the summer.
MS ion concentrations were high in the parts of the wedge representing the coldest periods of the late Pleistocene, from 12,900 to 12,700 years ago. This indicates that, even during these coldest periods of the late Ice Age, the near-shore region of the Beaufort Sea near Barrow may not have been completely filled by permanent ice, and that some open water existed in this area during the summers.
The team concludes in their study in the journal Earth and Planetary Science Letters that further studies of MS, bromide and sodium concentrations in other permafrost ice wedges could help scientists reconstruct past Arctic sea-ice conditions. In addition, according to Dr. Iizuka, "Understanding the mechanisms behind fluctuations in the Arctic sea ice provides a useful foundation for developing future strategies related to the Arctic region."
Paleontologists from Hokkaido University in Japan, in cooperation with paleontologists from the Perot Museum of Nature and Science in Dallas, Texas, have discovered the first-confirmed occurrence of a lambeosaurine (crested 'duck-billed' dinosaur) from the Arctic - part of the skull of a lambeosaurine dinosaur from the Liscomb Bonebed (71-68 Ma) found on Alaska's North Slope. The bonebed was previously known to be rich in hadrosaurine hadrosaurids (non-crested 'duck-billed' dinosaurs).
Paleontologists from Hokkaido University in Japan, in cooperation with paleontologists from the Perot Museum of Nature and Science in Dallas, Texas, have discovered the first-confirmed occurrence of a lambeosaurine (crested 'duck-billed' dinosaur) from the Arctic - part of the skull of a lambeosaurine dinosaur from the Liscomb Bonebed (71-68 Ma) found on Alaska's North Slope. The discovery proves for the first time that lambeosaurines inhabited the Arctic during the Late Cretaceous [Credit: Masato Hattori]
The discovery proves for the first time that lambeosaurines inhabited the Arctic during the Late Cretaceous. In addition, the numeric abundance of hadrosaurine fossils compared to the lambeosaurine fossils in the marine-influenced environment of the Liscomb Bonebed suggests the possibility that hadrosaurines and lambeosaurines had different habitat preferences.
"This new discovery illustrates the geographic link between lambeosaurines of North America and the Far East," said Takasaki. "Hopefully, further work in Alaska will reveal how closely the dinosaurs of Asia and North America are connected."
The newly discovered fossil, which is housed in the collections of the Perot Museum of Nature and Science, is a supraoccipital, one of the bones that forms the braincase. The new supraoccipital differs from those of hadrosaurines by the presence of large supraoccipital bosses and it's short, front-to-back length. Since these features are commonly seen in other members of Lambeosaurinae, the newly discovered supraoccipital was assigned to that group.
"This first definitive evidence of a crested hadrosaur in the Cretaceous Arctic tells us that we still have much to learn about the biodiversity and the biologically productive environments of the ancient north, and that the story these fossils tell us is continually evolving," adds Dr. Fiorillo.
Background. The Arctic is an extreme environment that is low in temperature, lacks sunlight during winters, and has seasonally limited food resources. Though it was warmer during the Late Cretaceous, the Arctic was surely one of the most challenging places to live for large vertebrates at the time. The Prince Creek Formation on the North Slope of Alaska is a world-famous rock unit for studying dinosaurs of the ancient Arctic. Because the dinosaurs found there lived in the ancient Arctic, rather than tropical or sub-tropical conditions, these dinosaurs challenge much of what we think we know about dinosaurs. The Liscomb Bonebed (71-68 Ma), which was deposited near the ancient Arctic shoreline, is especially rich in dinosaur bones, with more than 6,000 bones collected from it thus far.
More than 99% of dinosaur fossils known from the Liscomb Bonebed are hadrosaurs, a group of large, duck-billed herbivorous dinosaurs who lived during the Late Cretaceous and were found throughout much of the northern hemisphere. All of the hadrosaur fossils from the Liscomb Bonebed were long considered to belong to a hadrosaurine duck-billed dinosaur called Edmontosaurus. Up until now, all of the hadrosaurids known from across the Arctic, including those from the Liscomb Bonebed, were considered to belong to crest-less hadrosaurines.
The discovery of a fossil from a lambeosaurine hadrosaurid in the Liscomb Bonebed is historically important for Japanese paleontologists. The first "Japanese" dinosaur, Nipponosaurus, is a lambeosaurine hadrosaur. Based on the new discovery, Hokkaido University and the Perot Museum together used this discovery to further investigate the ecology of the Arctic hadrosaurids.
Significance
1. The first Arctic lambeosaurine. The new discovery indicates Arctic inhabitance and adaptation of lambeosaurines for the first time. In addition, the fossil's morphological similarities to the same bone in the skull of southern Canadian lambeosaurines suggest faunal interactions between the Arctic and the mid-latitudes.
2. Implication on habitat preferences. While the Liscomb Bonebed is known for numerous hadrosaurine fossils, the newly discovered bone represents the only definite lambeosaurine fossil from the site. The same trend is also known in mid-latitude localities of North America and eastern Asia, which were also deposited in near-shore environments. On the other hand, more lambeosaurine fossils are found in deposits laid down in inland environments. Therefore, we hypothesize that lambeosaurines favored inland environments, while hadrosaurines preferred coastal environments, a trend likely to have been independent of latitude. Different habitat preferences might have been a strategy to avoid excessive competition between the two groups of 'duck-billed' dinosaurs.
Future plans. Although the new discovery reveals Arctic inhabitance by lambeosaurines, more specific taxonomic status and potential functional adaptations to the severe Arctic environment remain unknown due to incompleteness of the specimen. Additional excavation and further research will help answer these questions.
A research team has discovered a previously unknown species of marsupial that lived in Alaska's Arctic during the era of dinosaurs, adding a vivid new detail to a complex ancient landscape.
This portrait of northern Alaska’s landscape and animals about 70 million years ago features a small mammal. The creature, though not necessarily Unnuakomys hutchisoni, illustrates scientists’ conclusion that mammals lived among the dinosaurs [Credit: James Havens]
The thumb-sized animal, named Unnuakomys hutchisoni, lived in the Arctic about 69 million years ago during the late Cretaceous Period. Its discovery, led by scientists from the University of Colorado and University of Alaska Fairbanks, is outlined in an article published in the Journal of Systematic Palaeontology.
The discovery adds to the picture of an environment that scientists say was surprisingly diverse. The tiny animal, which is the northernmost marsupial ever discovered, lived among a unique variety of dinosaurs, plants and other animals.
Alaska's North Slope, which was at about 80 degrees north latitude when U. hutchisoni lived there, was once thought to be a barren environment during the late Cretaceous. That perception has gradually changed since dinosaurs were discovered along the Colville River in the 1980s, with new evidence showing the region was home to a diverse collection of unique species that didn't exist anywhere else.
A 3D rendering shows fossilized teeth and jaws belonging to Unnuakomys hutchisoni, a newly discovered marsupial
that lived on Alaska's North Slope 69 million years ago. Scientists found its tiny teeth, which are about the size
of a grain of sand, at a site along the Colville River [Credit: University of Colorado at Boulder]
Finding a new marsupial species in the far north adds a new layer to that evolving view, said Patrick Druckenmiller, the director of the University of Alaska Museum of the North.
"Northern Alaska was not only inhabited by a wide variety of dinosaurs, but in fact we're finding there were also new species of mammals that helped to fill out the ecology," said Druckenmiller, who has studied dinosaurs in the region for more than a decade. "With every new species, we paint a new picture of this ancient polar landscape."
Marsupials are a type of mammal that carries underdeveloped offspring in a pouch. Kangaroos and koalas are the best-known modern marsupials. Ancient relatives were much smaller during the late Cretaceous, Druckenmiller said. Unnuakomys hutchisoni was probably more like a tiny opossum, feeding on insects and plants while surviving in darkness for as many as four months each winter.
Scientists excavate a dinosaur bone bed along the Colville River [Credit: Patrick Druckenmiller]
The research team, whose project was funded with a National Science Foundation grant, identified the new marsupial using a painstaking process. With the help of numerous graduate and undergraduate students, they collected, washed and screened ancient river sediment collected on the North Slope and then carefully inspected it under a microscope. Over many years, they were able to locate numerous fossilized teeth roughly the size of a grain of sand.
"I liken it to searching for proverbial needles in haystacks -- more rocks than fossils," said Florida State University paleobiologist Gregory Erickson, who contributed to the paper.
Jaelyn Eberle, curator of fossil vertebrates at the University of Colorado Museum of Natural History, led the effort to examine those teeth and a few tiny jawbones. Their analysis revealed a new species and genus of marsupial.
The Colville River flows across Alaska's North Slope. The bluffs on the left bank are made of the 70-million-year-old Prince Creek Formation and contain bones and teeth of dinosaurs and tiny mammals [Credit: Patrick Druckenmiller]
Mammal teeth have unique cusps that differ from species to species, making them a bit like fingerprints for long-dead organisms, said Eberle, the lead author of the study.
"If I were to go down to the Denver Zoo and crank open the mouth of a lion and look in -- which I don't recommend -- I could tell you its genus and probably its species based only on its cheek teeth," Eberle said.
The name Unnuakomys hutchisoni combines the Iñupiaq word for "night" and the Greek word "mys" for mouse, a reference to the dark winters the animal endured, and a tribute to J. Howard Hutchison, a paleontologist who discovered the fossil-rich site where its teeth were eventually found.
