South American Miocene mammals, new research


This 2013 video is called John Flynn on Extreme [prehistoric] Mammals South America.

From the University of Arizona in the USA:

Climate, grasses and teeth: The evolution of South America mammals

April 29, 2019

Grass-eating mammals, including armadillos as big as Volkswagens, became more diverse in South America about 6 million years ago because shifts in atmospheric circulation drove changes in climate and vegetation, according to a University of Arizona-led research team.

Geoscientists already knew the Earth was cooling 7 to 5.5 million years ago, a period of time known as the Late Miocene.

However, the changes in ocean climate during that time have been better understood than changes in the continental climate, said lead author Barbara Carrapa, professor and head of the UA department of geosciences.

The new research shows that about 7 to 6 million years ago, the global tropical atmospheric circulation known as the Hadley circulation intensified. As a result, the climate of South America became drier, subtropical grasslands expanded and the numbers of mammal species that were good at eating grasses increased.

Carrapa and her colleagues used a computer model to figure out that the Hadley circulation had strengthened in the late Miocene, altering the climate. They then compared the model’s predictions of the past climate with the natural archives of rainfall and vegetation stored in ancient soils. The model’s predictions agreed with the natural archives.

“We found a strong correlation between this big change in late Miocene climate and circulation that affected the ecology — the plants and animals,” she said. “It has implications for ecosystem evolution.”

Carrapa said the new research — an unusual blend of mammalian paleontology, the geochemistry of ancient soils and global climate computer models — provides a new understanding of the late Miocene, a time when near-modern ecosystems became established.

The paper, “Ecological and hydroclimate responses to strengthening of the Hadley circulation in South America during the Late Miocene Cooling,” by Carrapa, Mark Clementz of the University of Wyoming in Laramie and Ran Feng of the University of Connecticut in Storrs is scheduled for publication the week of April 29 in the Proceedings of the National Academy of Sciences. The National Science Foundation funded the research.

Geoscientists use the geochemistry of ancient soils, specifically forms of the elements oxygen and carbon, to infer past precipitation and vegetation. Researchers had thought the precipitation at the time the soil formed was mostly a function of the site’s topography and elevation.

Carrapa wanted to test that idea by looking at the geochemistry of ancient soils on a continental scale. She teamed up with her long-time colleague Clementz, a paleontologist.

The researchers compiled the published data of the oxygen-18/oxygen-16 ratio and carbon-13/carbon-12 ratio from ancient soils covering a wide swath of South America — from 15 degrees South latitude to 35 degrees South latitude, or about the change from La Paz, Bolivia to Buenos Aires, Argentina. Changes in the oxygen ratio provide information on past precipitation, while changes in carbon ratio indicate what plants were growing at the time.

Clementz scoured the published literature and did what Carrapa called .” .. an amazing job of pulling all the data together so we could look at it in a comprehensive way.”

The results were surprising, Carrapa said. The changes in soil geochemistry during the late Miocene changed in latitudinal bands from north to south, indicating an underlying cause spanning much of South America, not just local changes in elevation or topography.

The two researchers thought the systematic shifts in soil geochemistry were related to changes in climate, so they asked Feng to help them by applying the global climate model she used for research.

Feng loaded known information about the Miocene-to-late-Miocene climate, including atmospheric carbon dioxide concentrations and the ocean temperatures, into the computer model and then asked it to simulate three different versions of late Miocene climate — not much cooler, cooler, and much cooler than before. In each case, the simulation indicated what soil geochemistry would have occurred under that climate regime.

The team found the geochemistry of South American ancient soils predicted by the model matches the geochemistry of the actual soil samples.

Feng figured out that the Earth’s Hadley circulation intensified from 7 to 6 million years ago.

“The records compiled by Barbara and Mark could be explained by a significant change in the strength of the Hadley circulation,” she said.

Feng’s work with the global climate model shows how the past climate could have created the patterns the team was seeing in the soil geochemistry, Clementz said.

The carbon ratio from the ancient soils reflects the vegetation of the time and indicates that in the late Miocene, grasslands were expanding as the climate was changing.

“During the late Miocene, things are starting to dry out, particularly in the 25-30 degree South zone,” he said. “There’s also an increase in the numbers of animals with high-crowned or ever-growing teeth.”

Grasses contain silica, an abrasive substance, which is why grass-eaters have either high-crowned teeth or teeth that continue to grow. The mammals that became more prevalent in the late Miocene included giant armadillos and rhinoceros-like animals and also smaller mammals, he said.

Carrapa said, “Looking at geological pasts is like looking at different planets. The state of the Earth we see today is very different from the Earth of 10 million years ago, 6 million years ago — it’s a different planet. You have the possibility of looking at a different planet through the lens of time, and with the geological record we can do that.”

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Big prehistoric carnivore discovered in Kenyan museum


This 18 April 2019 video is called Newly Discovered Ancient Carnivore Was Bigger Than a Polar Bear.

From Ohio University in the USA:

Fossils found in museum drawer in Kenya belong to gigantic carnivore

Paleontologists say mammal was larger than a polar bear

April 18, 2019

Paleontologists at Ohio University have discovered a new species of meat-eating mammal larger than any big cat stalking the world today. Larger than a polar bear, with a skull as large as that of a rhinoceros and enormous piercing canine teeth, this massive carnivore would have been an intimidating part of the eastern African ecosystems occupied by early apes and monkeys.

In a new study published in the Journal of Vertebrate Paleontology, the researchers name Simbakubwa kutokaafrika, a gigantic carnivore known from most of its jaw, portions of its skull, and parts of its skeleton. The 22-million-year-old fossils were unearthed in Kenya decades ago as researchers canvassed the region searching for evidence of ancient apes. Specimens were placed in a drawer at the National Museums of Kenya and not given a great deal of attention until Ohio University researchers Dr. Nancy Stevens and Dr. Matthew Borths rediscovered them, recognizing their significance.

“Opening a museum drawer, we saw a row of gigantic meat-eating teeth, clearly belonging to a species new to science,” says study lead author Borths. Borths was a National Science Foundation Postdoctoral Research Fellow with Stevens in the Department of Biomedical Sciences at Ohio University when the research was conducted, and is now Curator of the Division of Fossil Primates at the Duke Lemur Center at Duke University.

Simbakubwa is Swahili for “big lion” because the animal was likely at the top of the food chain in Africa, as lions are in modern African ecosystems. Yet Simbakubwa was not closely related to big cats or any other mammalian carnivore alive today. Instead, the creature belonged to an extinct group of mammals called hyaenodonts.

Hyaenodonts were the first mammalian carnivores in Africa. For about 45 million years after the extinction of the non-avian dinosaurs, hyaenodonts were the apex predators in Africa. Then, after millions of years of near-isolation, tectonic movements of the Earth’s plates connected Africa with the northern continents, allowing floral and faunal exchange between landmasses. Around the time of Simbakubwa, the relatives of cats, hyenas, and dogs began to arrive in Africa from Eurasia.

As the relatives of cats and dogs were going south, the relatives of Simbakubwa were going north. “It’s a fascinating time in biological history,” Borths says. “Lineages that had never encountered each other begin to appear together in the fossil record.”

The species name, kutokaafrika, is Swahili for “coming from Africa” because Simbakubwa is the oldest of the gigantic hyaenodonts, suggesting this lineage of giant carnivores likely originated on the African continent and moved northward to flourish for millions of years.

Ultimately, hyaenodonts worldwide went extinct. Global ecosystems were changing between 18 and 15 million years ago as grasslands replaced forests and new mammalian lineages diversified. “We don’t know exactly what drove hyaenodonts to extinction, but ecosystems were changing quickly as the global climate became drier. The gigantic relatives of Simbakubwa were among the last hyaenodonts on the planet,” remarks Borths.

“This is a pivotal fossil, demonstrating the significance of museum collections for understanding evolutionary history,” notes Stevens, Professor in the Heritage College of Osteopathic Medicine at Ohio University and co-author of the study. “Simbakubwa is a window into a bygone era. As ecosystems shifted, a key predator disappeared, heralding Cenozoic faunal transitions that eventually led to the evolution of the modern African fauna.”

This study was funded by grants from the National Science Foundation (EAR/IF-0933619; BCS-1127164; BCS-1313679; EAR-1349825; BCS-1638796; DBI-1612062), The Leakey Foundation, National Geographic Society (CRE), Ohio University Research Council, Ohio University Heritage College of Osteopathic Medicine, SICB and The Explorers Club.

This discovery underscores both the importance of supporting innovative uses of fossil collections, as well as the importance of supporting the research and professional development of talented young postdoctoral scientists like Dr. Borths,” said Daniel Marenda, a program director at the National Science Foundation, which funded this research. “This work has the potential to help us understand how species adapt — or fail to adapt in this case — to a rapidly changing global climate.”

Texas Miocene fossils, new study


This July 2013 video from Spain is called Proboscidea: Evolution of elephants (early Miocene): Gomphotherium.

Gomphotherium elephant relatives used to live in Europe as well as North America.

From the University of Texas at Austin in the USA:

Ancient ‘Texas Serengeti‘ had elephant-like animals, rhinos, alligators and more

April 11, 2019

During the Great Depression, some unemployed Texans were put to work as fossil hunters. The workers retrieved tens of thousands of specimens that have been studied in small bits and pieces while stored in the state collections of The University of Texas at Austin for the past 80 years.

Now, decades after they were first collected, a UT researcher has studied and identified an extensive collection of fossils from dig sites near Beeville, Texas, and found that the fauna make up a veritable “Texas Serengeti” — with specimens including elephant-like animals, rhinos, alligators, antelopes, camels, 12 types of horses and several species of carnivores. In total, the fossil trove contains nearly 4,000 specimens representing 50 animal species, all of which roamed the Texas Gulf Coast 11 million to 12 million years ago.

A paper describing these fossils, their collection history and geologic setting was published April 11 in the journal Palaeontologia Electronica.

“It’s the most representative collection of life from this time period of Earth history along the Texas Coastal Plain,” said Steven May, the research associate at the UT Jackson School of Geosciences who studied the fossils and authored the paper.

In addition to shedding light on the inhabitants of an ancient Texas ecosystem, the collection is also valuable because of its fossil firsts. They include a new genus of gomphothere, an extinct relative of elephants with a shovel-like lower jaw, and the oldest fossils of the American alligator and an extinct relative of modern dogs.

The fossils came into the university’s collection as part of the State-Wide Paleontologic-Mineralogic Survey that was funded by the Works Progress Administration (WPA), a federal agency that provided work to millions of Americans during the Great Depression. From 1939 to 1941, the agency partnered with the UT Bureau of Economic Geology, which supervised the work and organized field units for collecting fossils and minerals across the state.

Despite lasting only three years, the survey found and excavated thousands of fossils from across Texas including four dig sites in Bee and Live Oak counties, with the majority of their finds housed in what is now the Texas Vertebrate Paleontology Collections at the Jackson School Museum of Earth History. Over the years, a number of scientific papers have been published on select groups of WPA specimens. But May’s paper is the first to study the entire fauna.

This extensive collection of fossils is helping to fill in gaps about the state’s ancient environment, said Matthew Brown, the director of the museum’s vertebrate paleontology collections.

The emphasis on big mammals is due in large part to the collection practices of the fossil hunters, most of whom were not formally trained in paleontology. Large tusks, teeth and skulls were easier to spot — and more exciting to find — than bones left by small species.

“They collected the big, obvious stuff,” May said. “But that doesn’t fully represent the incredible diversity of the Miocene environment along the Texas Coastal Plain.”

In order to account for gaps in the collection, May tracked down the original dig sites so he could screen for tiny fossils such as rodent teeth. One of the sites was on a ranch near Beeville owned by John Blackburn. Using aerial photography and notes from the WPA program stored in the university’s archives, May and the research team were able to track down the exact spot of an original dig site.

“We’re thrilled to be a part of something that was started in 1939,” Blackburn said. “It’s been a privilege to work with UT and the team involved, and we hope that the project can help bring additional research opportunities.”

Scores of WPA-era fossils in the UT collections are still secured in plaster field jackets, waiting to be unpacked for future research projects. Lab managers Deborah Wagner and Kenneth Bader are supervising their preparation, which includes teaching UT students fossil prep skills so they can pick up where the WPA workers left off.

Wagner said that the advantage of unpacking fossils decades later is that they are able to apply modern research techniques that scientists from past eras wouldn’t have dreamed possible.

“We are able to preserve more detailed anatomy and answer questions that require higher resolution data,” she said.

May said that he plans to continue to study the fossils as more are prepared.

Miocene giant extinct animals in Italy


This 5 March 2019 video from the USA, about Gargano, formerly an island, now an Italian mainland peninsula, says about itself:

The Island of Huge Hamsters and Giant Owls

Back in the late Miocene epoch, there was an island–or maybe a group of islands– in the Mediterranean Sea that was populated with fantastic giant beasts. It’s a lesson in the very strange, but very real, powers of natural selection.

Prehistoric monkey discovery in Kenya


This August 2017 video from Kenya says about itself:

Nengo et al. New infant cranium from the African Miocene sheds light on ape evolution. Nature 10 August 2017.

From the University of Texas at Austin in the USA:

Fossil teeth from Kenya solve ancient monkey mystery

March 11, 2019

The teeth of a new fossil monkey, unearthed in the badlands of northwest Kenya, help fill a 6-million-year void in Old World monkey evolution, according to a study by U.S. and Kenyan scientists published in the Proceedings of the National Academy of Sciences.

The discovery of 22-million-year-old fossilized monkey teeth — described as belonging to a new species, Alophia metios — fills a void between a previously discovered 19-million-year-old fossil tooth in Uganda and a 25-million-year-old fossil tooth found in Tanzania. The finding also sheds light on how their diet may have changed the course of their evolution.

“For a group as highly successful as the monkeys of Africa and Asia, it would seem that scientists would have already figured out their evolutionary history,” said the study’s corresponding author John Kappelman, an anthropology and geology professor at The University of Texas at Austin. “Although the isolated tooth from Tanzania is important for documenting the earliest occurrence of monkeys, the next 6 million years of the group’s existence are one big blank. This new monkey importantly reveals what happened during the group’s later evolution.”

Since the time interval from 19 to 25 million years ago is represented by a small number of African fossil sites, the team targeted the famous fossil-rich region of West Turkana to try to fill in that blank.

“Today, this region is very arid,” said Benson Kyongo, a collections manager at the National Museums of Kenya. “But millions of years ago, it was a forest and woodland landscape crisscrossed by rivers and streams. These ancient monkeys were living the good life.”

While in the field, the team uncovered hundreds of mammal and reptile jaws, limbs and teeth ranging from 21 million to more than 24 million years old, including remains of early elephants. The newly discovered monkey teeth are more primitive than geologically younger monkey fossils, lacking what researchers referred to as “lophs”, or a pair of molar crests, thus earning the new species its name, Alophia, meaning “without lophs.”

“These teeth are so primitive that when we first showed them to other scientists, they told us, “Oh no, that isn’t a monkey. It’s a pig”, said Ellen Miller, an anthropology professor at Wake Forest University. “But because of other dental features, we are able to convince them that yes, it is in fact a monkey.”

The success of Old World monkeys appears to be closely tied to their unique dentition, researchers said. Today, the configuration of cusps and lophs on the molar teeth enable them to process the wide range of plant and animal foods encountered in the diverse environments of Africa and Asia.

“You can think of the modern-day monkey molar as the uber food processor, able to slice, dice, mince and crush all sorts of foods,” said Mercedes Gutierrez, an anatomy professor at the University of Minnesota.

“How and when this unique dentition evolved is one of the unanswered questions in primate evolution,” said James Rossie, an anthropology professor at Stony Brook University. The researchers speculated that Alophia’s primitive dentition was adapted to a diet that consisted of hard fruits, seeds and nuts, and not leaves, which are more efficiently processed by the more evolved dentition of fossil monkeys dating from after 19 million years ago.

“It is usually assumed that the trait responsible for a group’s success evolved when the group originated, but Alophia shows us this is not the case for Old World monkeys,” said Samuel Muteti, a researcher at the National Museums of Kenya. “Instead, the characteristic dentition of modern monkeys evolved long after the group first appeared.”

The researchers hypothesized that the inclusion of leaves in the diet is what later drove monkey dental evolution.

Monkeys originated at a time when Africa and Arabia were joined as an island continent, with its animals evolving in isolation until docking with Eurasia sometime between 20 million and 24 million years ago. It was only after docking that the mammals today typically considered “African” — antelope, pigs, lions, rhinos, etc. — made their entry onto the continent. So, researchers asked: Could this event and possible competition between the residents and the newly arrived Eurasian species have driven monkeys to exploit leaves, or did changing climates serve to make leaves a more attractive menu entrée?

“The way to test between these hypotheses is to collect more fossils,” Kappelman said. “Establishing when, exactly, the Eurasian fauna entered Afro-Arabia remains one of the most important questions in paleontology, and West Turkana is one of the only places we know of to find that answer.”

The team intends to be back in the field later this year.

Extinct Miocene giant animals of the Amazon


This 2017 video is called National Geographic Documentary – Secrets in the Amazon Rainforest – Wild Amazon.

From the Fundação de Amparo à Pesquisa do Estado de São Paulo in Brazil:

Giant animals lived in Amazonian mega-wetland

Lake systems existing in regions over 10 million years ago survived the Amazon River reversal due to Andean uplift

February 25, 2019

A land of giants. This is the best definition for Lake Pebas, a mega-wetland that existed in western Amazonia during the Miocene Epoch, which lasted from 23 million to 5.3 million years ago.

The Pebas Formation was the home of the largest caiman and gavialoid crocodilian ever identified, both of which were over ten meters in length, the largest turtle, whose carapace had a diameter of 3.5 meters, and rodents that were as large as present-day buffaloes.

Remains of the ancient biome are scattered over an area of more than 1 million square meters in what is now Bolivia, Acre State and western Amazonas State in Brazil, Peru, Colombia and Venezuela. The oldest datings in this biome are for fossils found in Venezuela and show that Lake Pebas existed 18 million years ago.

Until recently, scientists believed that the mega-swamp dried up more than 10 million years ago, before the Amazon River reversed course. During most of the Miocene, this river flowed from east to west, opposite to its present direction. The giant animals disappeared when the waters of Pebas receded.

While investigating sediments associated with vertebrate fossils from two paleontological sites on the Acre and Purus Rivers, Marcos César Bissaro Júnior, a biologist affiliated with the University of São Paulo’s Ribeirão Preto School of Philosophy, Science and Letters (FFCLRP-USP) in Brazil, obtained datings of 8.5 million years with a margin of error of plus or minus 500,000 million years.

There is evidence that the Amazon was already running in its present direction 8.5 million years ago, draining from the Peruvian Andes into the Atlantic Ocean. By then, the Pebas system must have no longer resembled the magnificent wetlands of old. Rather, the system resembled a floodplain similar to the present-day Brazilian Pantanal. This is the view of Annie Schmaltz Hsiou, a professor in the Biology Department at FFCLRP-USP and supervisor of Bissaro Júnior’s research, which is described in a recently published article in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

The study was supported by São Paulo Research Foundation -FAPESP and Brazil’s National Council for Scientific and Technological Development (CNPq). The participants also included researchers from the Federal University of Santa Maria (UFSM), the Zoobotanic Foundation’s Natural Science Museum in Rio Grande do Sul, São Paulo State University (UNESP), the Federal University of Acre, and Boise State University in Idaho (USA).

The Pebas system encompasses several geological formations in western Amazonia: the Pebas and Fitzcarrald Formations in Peru and Brazil, the Solimões Formation in Brazil, the Urumaco and Socorro Formations in Venezuela, the La Venta Formation in Colombia, and the Quebrada Honda Formation in Bolivia.

“While the Solimões Formation is one of the best-sampled Neogene fossil-bearing stratigraphic units of northern South America, assumptions regarding deposition age in Brazil have been based largely on indirect methods,” Bissaro Júnior said.

“The absence of absolute ages hampers more refined interpretations on the paleoenvironments and paleoecology of the faunistic associations found there and does not allow us to answer some key questions, such as whether these beds were deposited after, during or before the formation of the proto-Amazon River.”

To answer these and other questions, Bissaro Júnior’s study presents the first geochronology of the Solimões Formation, based on mineral zircon specimens collected at two of the region’s best-sampled paleontological sites: Niterói on the Acre River in the municipality of Senador Guiomar and Talismã on the Purus River in the municipality of Manuel Urbano.

Since the 1980s, many Miocene fossils have been found at the Niterói site, including crocodilians, fishes, rodents, turtles, birds, and xenarthran mammals (extinct terrestrial sloths). Miocene fossils of crocodilians, snakes, rodents, primates, sloths, and extinct South American ungulates (litopterns) have been found in the same period at the Talismã site.

As a result of the datings, Bissaro Júnior discovered that the rocks at the Niterói and Talismã sites are approximately 8.5 million and 10.9 million years old (maximum depositional age), respectively.

“Based on both faunal dissimilarities and maximum depositional age differences between the two localities, we suggest that Talismã is older than Niterói. However, we stress the need for further zircon dating to test this hypothesis, as well as datings for other localities in the Solimões Formation,” he said.

Drying up of Pebas

Lake Pebas was formed when the land rose in the proto-Amazon basin as a result of the Andean uplift, which began accelerating 20 million years ago. At that time, western Amazonia was bathed by the Amazon (which then flowed toward the Caribbean) and the Magdalena in Colombia. The Andes uplift that occurred in what is now Peru and Colombia eventually interrupted the flow of water toward the Pacific, causing water to pool in western Amazonia and giving rise to the mega-wetland.

However, the Andes continued to rise. The continuous uplifting of land in Amazonia had two effects. The proto-Amazon, previously pent up in Lake Pebas, reversed course and became the majestic river we now know. During this process, water gradually drained out of the Pebas mega-swamp.

The swamp became a floodplain full of huge animals, which still existed 8.5 million years ago, according to new datings by Bissaro Júnior. Unstoppable geological forces eventually drained the remains of the temporary lagoons and lakes in western Amazonia. This was the end of Pebas and its fauna.

“The problem with dating Pebas has always been associating datings directly with the vertebrate fauna. There are countless datings of rocks in which invertebrate fossils have been found, but dating rocks with vertebrates in Brazil was one of our goals,” Schmaltz Hsiou said.

The new datings, she added, suggest that the Pebas system — i.e., the vast wetland — existed between 23 million and 10 million years ago. The Pebas system gave way to the Acre system, an immense floodplain that existed between 10 million and 7 million years ago, where reptiles such as Purussaurus and Mourasuchus still lived.

“The Acre system must have been a similar biome to what was then Venezuela, consisting of lagoons surrounding the delta of a great river, the proto-Orinoco,” she said.

Giant rodents

Rodents are a highly diversified group of mammals that inhabit all continents except for Antarctica. Amazonia is home to a large number of rodent species.

“In particular, a rodent group known scientifically as Caviomorpha came to our continent about 41 million years ago from Africa,” said Leonardo Kerber, a researcher at UFSM’s Quarta Colônia Paleontological Research Support Center (CAPPA) and a coauthor of the article published in Palaeogeography, Palaeoclimatology, Palaeoecology.

“In this period, known as the Eocene Epoch, Africa and South America were already totally separated, with at least 1,000 kilometers between the closest points of the two continents, so there couldn’t have been any biogeographical connections enabling terrestrial vertebrates to migrate between the two land masses,” Kerber said. “However, the ocean currents drove dispersal by means of natural rafts of tree trunks and branches blown into rivers by storms and swept out to sea. Some of these rafts would have borne away small vertebrates. An event of this kind may have enabled small mammals such as Platyrrhini monkeys, as well as small rodents, to cross the ocean, giving rise to one of the most emblematic groups of South American mammals, the caviomorph rodents.”

According to Kerber, the continent’s caviomorph rodents have undergone a long period of evolution since their arrival, becoming highly diversified as a result. In Brazil, the group is currently represented by the paca, agouti, guinea pig, porcupine and bristly mouse, as well as by the capybara, the world’s largest rodent.

“In Amazonia, above all, we now find a great diversity of bristly mice, porcupines, agoutis and pacas. In the Miocene, however, the Amazonian fauna was very different from what we can observe now,” Kerber said.

“In recent years, in addition to reporting the presence of many fossils of species already known to science, some of which had previously been recorded in the Solimões Formation and others that were known from other parts of South America but recorded in Solimões for the first time, we’ve described three new medium-sized rodent species (Potamarchus adamiae, Pseudopotamarchus villanuevai and Ferigolomys pacarana — Dinomyidae) that are related to the pacarana (Dinomys branickii).”

Kerber said an article to be published shortly in the Journal of Vertebrate Paleontology will recognize Neoepiblema acreensis, an endemic Brazilian Miocene neoepiblemid rodent that weighed some 120 kg as a valid species.

“The species was described in 1990 but was considered invalid at the end of the decade. These fossil records of both known and new species help us understand how life evolved in the region and how its biodiversity developed and experienced extinctions over millions of years in the past,” Kerber said.

Prehistoric weasel relative research


A reconstruction of the head of Leptarctus primus attacking the Miocene rodent Cupidinimus. Credit: AMNH/N. Wong

From the American Museum of Natural History in the USA:

Extinct weasel relative with confounding skull likely ate meat with a side of veggies

New biomechanical study finds that the strangely shaped skull of Leptarctus is most similar to the American badger

February 22, 2019

New research on an extinct weasel relative reveals what it might have eaten when it lived in North America and Asia about 20 million years ago. The oddly shaped skull of Leptarctus primus has long led to conflicting theories about its diet. But the new work, based on biomechanical modeling and published this week in the Journal of Vertebrate Paleontology, shows that Leptarctus was likely a carnivorous predator, with capability for omnivory and a broader diet when prey was scarce, and had a skull that functioned similarly to that of the living American badger.

Leptarctus primus, which lived in the Miocene and was just a little larger than a housecat, has intrigued researchers because of its unusual and extremely robust skull.

“For a mammal, its skull is really strange,” said co-author Z. Jack Tseng, a research associate at the American Museum of Natural History and an assistant professor of pathology and anatomical sciences at the Jacobs School of Medicine and Biomedical Science at the University at Buffalo. “It’s heavily built — like a tank — with very thick zygomatic cheek bones. The top of its head looks like it’s wearing a helmet.”

Strikingly, Leptarctus primus has two parallel ridges that line the top of the head (other carnivorans typically have a single central ridge or have smooth skulls). For many years, paleontologists have debated the ecological niche of Leptarctus based on conflicting interpretations of the strong parallel skull ridges, distinctive skull shape, and the shape of its teeth and chewing wear. Previous interpretations of their feeding lifestyle ranged widely, across virtually every type of known feeding behavior in carnivorans (dogs, cats, hyaenas, bears, seals, and weasels and their relatives), including herbivore, carnivore, insectivore, and omnivore. But because of the lack of quantitative research into how Leptarctus skulls functioned, the question of their diets remained unanswered.

In this study, led by Alixandra Prybyla, who was a student in the Museum’s National Science Foundation Summer Research Experience for Undergraduates program while at Columbia University, the researchers took an engineering approach. The team compared an almost complete fossil skull of Leptarctus primus with 18 species of modern carnivorans with known diets as well as to other fossil species, using bite simulations based on CT scans of the skulls and virtual modeling of feeding mechanics.

According to John Flynn, study co-author, research team leader, and Frick curator of fossil mammals in the Museum’s Division of Paleontology, “Traditional methods of studying skull, tooth, and skeleton anatomy are still essential for understanding how fossil species lived. But high-resolution x-ray CT images and sophisticated computerized engineering modeling tools have completely transformed our ability to accurately reconstruct feeding habits in extinct animals.”

They found that among the other species analyzed, the skull of Leptarctus is mechanically most similar to the skull of the American badger. Despite some differences in their skull appearances, the computer simulations indicate that the badger is the best living biomechanical analog for understanding the dietary lifestyle of Leptarctus. Based upon those comparisons, the team determined that it was primarily a carnivore and an active predator, but that it could also have been an omnivore feeding on a wider range of plant and insect foods when necessary.

“It was probably hunting down prey and taking in whatever it had access to most of the time,” Tseng said.

Prybyla added: “This complete skull of Leptarctus represents an untapped wellspring of information on the history of ancient relatives of weasels, otters, badgers, and skunks. It’s wonderful what one specimen can illuminate for researchers. To spearhead a project of this magnitude as an undergraduate student was extremely empowering.”

The researchers will conduct future studies using similar engineering modeling tools to look at variations in skull feeding mechanics among other species in the leptarctine group, to determine how many different types of feeding adaptations may have existed among these unusual extinct predators.