Triassic beetle discovery in Dutch Winterswijk


This video from the USA says about itself:

New Evidence Connects Dung Beetle Evolution to Dinosaurs

4 May 2016

Dr. Nicole Gunter, invertebrate zoology collections manager at The Cleveland Museum of Natural History, discusses research that uncovered an evolutionary connection between dinosaurs and dung beetles. The findings place the origin of dung beetles in the Lower Cretaceous period, with the first major diversification occurring in the middle of the Cretaceous.

By Janene Pieters on April 25, 2017 – 12:25:

A very rare fossil of a beetle that lived in the Netherlands 200 million years ago was found in a quarry in Winterswijk, according to a scientific publication in Paläontologische Zeitschrift written by paleontologists from Utrecht University,

From Paläontologische Zeitschrift:

New fossil insects from the Anisian (Lower to Middle Muschelkalk) from the Central European Basin (Germany and The Netherlands)

22 April 2017

Abstract

The Palaeozoic–Mesozoic transition is characterized not only by the most massive Phanerozoic mass extinction at the end of the Permian period, but also its extensive aftermath and a prolonged period of major biotal recovery during the succeeding Middle to Late Triassic.

Particularly, Anisian insect species from units of the Lower to Middle Muschelkalk from the Central European Basin are rare.

The Anisian is from 247.2 million years ago until 242 million years ago. So, older than the ‘200 million years ago’ of the Janene Pieters article.

The specimens described here originated from the Anisian Wellenkalk facies (Lower Muschelkalk), Vossenveld Formation of the Winterswijk quarry, The Netherlands, and from the orbicularis Member (lowermost Middle Muschelkalk, Anisian) of Esperstedt near Querfurt (Saxony-Anhalt).

Thus, the described insect remains from Winterwijk and Esperstedt expand our knowledge about Middle Triassic terrestrial arthropod communities and their palaeodiversity. A new species of Chauliodites (C. esperstedti sp. nov) is introduced.

Ancient sea scorpions, new research


This video says about itself:

13 September 2016

Today we examine the amazingly bizarre group of prehistoric arthropods, the Eurypterids or sea scorpions of the Paleozoic. We answer questions like: Where they really scorpions? How large did they get? And what are they exactly?

From the University of Alberta in Canada:

Sea scorpions: The original sea monster

Sea scorpions used serrated tail spine to dispatch their prey, researchers suggest

April 18, 2017

Summary: Related to both modern scorpions and horseshow [sic: horseshoe] crabs, sea scorpions had thin, flexible bodies. Some species also had pinching claws and could grow up to three metres in length. New research that the sea scorpions had another weapon at their disposal: a serrated, slashing tail spine.

Four hundred and thirty million years ago, long before the evolution of barracudas or sharks, a different kind of predator stalked the primordial seas. The original sea monsters were eurypterids — better known as sea scorpions.

Related to both modern scorpions and horseshow [sic: horseshoe] crabs, sea scorpions had thin, flexible bodies. Some species also had pinching claws and could grow up to three metres in length. New research by University of Alberta scientists Scott Persons and John Acorn hypothesise that the sea scorpions had another weapon at their disposal: a serrated, slashing tail spine.

Armed and dangerous

“Our study suggests that sea scorpions used their tails, weaponized by their serrated spiny tips, to dispatch their prey,” says Scott Persons, paleontologist and lead author on the study.

Sparked by the discovery of a new fossil specimen of the eurypterid Slimonia acuminata, Persons and Acorn make the biomechanical case that these sea scorpions attacked and killed their prey with sidelong strikes of their serrated tail.

The fossil, collected from the Patrick Burn Formation near Lesmahagow, Scotland, shows a eurypterid Slimonia acuminata, with a serrated-spine-tipped tail curved strongly to one side.

Powerful weapons

Unlike lobsters and shrimps, which can flip their broad tails up and down to help them swim, eurypterid tails were vertically inflexible but horizontally highly mobile.

“This means that these sea scorpions could slash their tails from side to side, meeting little hydraulic resistance and without propelling themselves away from an intended target,” explains Persons. “Perhaps clutching their prey with their sharp front limbs eurypterids could kill pretty [well] using a horizontal slashing motion.”

Among the likely prey of Slimonia acuminata and other eurypterids were ancient early vertebrates.

Megatherium giant sloth was vegetarian


This February 2017 video is called 10 Interesting Facts About Sloths.

From the Senckenberg Research Institute and Natural History Museum in Germany:

Giant sloth was vegetarian: Diet of fossil Megatherium decoded

April 18, 2017

Summary: Scientists have examined the diet of the extinct Giant Sloth Megatherium. Based on analyses of the collagen in the fossil bones, the researchers concluded in their study that Megatherium subsisted on an exclusively vegetarian diet. Until recently, there had been much speculation about the food habits of these elephant-sized, ground-dwelling animals.

Together with an international team, Senckenberg scientists examined the diet of the extinct Giant Sloth Megatherium. Based on analyses of the collagen in the fossil bones, the researchers concluded in their study, which was recently published in the scientific journal Gondwana Research that Megatherium subsisted on an exclusively vegetarian diet. Until recently, there had been much speculation about the food habits of these elephant-sized, ground-dwelling animals.

Sloths may well rank among the world’s most peculiar animals: With their backs pointing downward, they hang in trees and move in slow motion from branch to branch with the aid of their sickle-shaped claws. “Sloths already occurred 10,000 years ago, for example the species Megatherium,” explains Professor Dr. Hervé Bocherens of the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tübingen.

The extinct relatives of the sloths could reach the size of an elephant and were much too heavy to spend a significant amount of time in the trees. Instead, they lived on the ground, where they excavated large burrows. For many years, their dietary habits were an enigma; the long claws on their hands and feet, in particular, gave rise to various speculations. Did the sloths use their claws to dig up subterranean insect colonies? Did the long claws serve as hunting tools, and were the giant animals carnivores? Or did the fossil representatives live on a strictly vegetarian diet, like the recent sloths? “These questions were at the center of our new study,” adds Bocherens.

Normally it is possible to deduce the feeding habits of fossil animals on the basis of the shape and wear of their teeth – however, the teeth of the Giant Sloth are not comparable to those of modern animals. “We therefore had to use a different method, so we measured the composition of carbon isotopes – the ratio of protein and mineral content – in the fossilized sloth bones,” explains Bocherens, and he continues, “Our measurements show that Megatherium lived on an exclusively vegetarian diet.”

In carnivores, the proportion of proteins is significantly higher than in herbivores, which primarily eat food high in carbohydrates. These differences can be documented in the isotopes. In order to reinforce their results, the scientists compared their data with more than 200 bones from modern mammals, whose diet is known, as well as with fossil specimens from both carnivores and herbivores. “Our results show that by using this method, it is possible to reconstruct the feeding habits of animals even several thousand years after their death,” adds the biogeologist from Tübingen.

Knowledge of the sloths’ feeding habits is important in order to understand their role in past ecosystems. “Moreover, the results can help us understand the interactions between Megatherium and the first human inhabitants of America – their habitats overlapped for several thousand years, before the Giant Sloth became extinct,” offers Bocherens as a preview.

Moabosaurus dinosaur discovery in Utah, USA


This video from the USA says about itself:

12 April 2017

BYU [Brigham Young University] professors have discovered a new species of dinosaur Moabosaurus utahensis, named to honor Moab, Utah, which paleontologists consider Utah’s ‘gold mine’.

The bones of the dinosaur were unearthed near Moab, Utah.

The 32-foot herbivore is a relative of the long-necked Brontosaurus and Brachiosaurus.

An assembled skeleton is on display at BYU’s Museum of Paleontology in Provo, Utah.

From Brigham Young University in the USA:

Moabosaurus discovered in Utah‘s ‘gold mine’

April 13, 2017

Summary: Move over, honeybee and seagull: it’s time to meet Moabosaurus utahensis, Utah’s newly discovered dinosaur, whose past reveals even more about the state’s long-term history. The bones of the 125-million-year-old dinosaur were extracted over the course of four decades from a quarry near Arches National Park.

Move over, honeybee and seagull: it’s time to meet Moabosaurus utahensis, Utah’s newly discovered dinosaur, whose past reveals even more about the state’s long-term history.

The Moabosaurus discovery was published this week by the University of Michigan’s Contributions from the Museum of Paleontology. The paper, authored by three Brigham Young University researchers and a BYU graduate at Auburn University, profiles Moabosaurus, a 125-million-year-old dinosaur whose skeleton was assembled using bones extracted from the Dalton Wells Quarry, near Arches National Park.

BYU geology professor and lead author Brooks Britt explained that in analyzing dinosaur bones, he and colleagues rely on constant comparisons with other related specimens. If there are enough distinguishing features to make it unique, it’s new.

“It’s like looking at a piece of a car,” Britt said. “You can look at it and say it belongs to a Ford sedan, but it’s not exactly a Focus or a Fusion or a Fiesta. We do the same with dinosaurs.”

Moabosaurus belongs to a group of herbivorous dinosaurs known as sauropods, which includes giants such as Brontosaurus and Brachiosaurus, who had long necks and pillar-like legs. Moabosaurus is most closely related to species found in Spain and Tanzania, which tells researchers that during its time, there were still intermittent physical connections between Europe, Africa and North America.

Moabosaurus lived in Utah before it resembled the desert we know — when it was filled with large trees, plentiful streams, lakes and dinosaurs. “We always think of Moab in terms of tourism and outdoor activities, but a paleontologist thinks of Moab as a gold mine for dinosaur bones,” Britt said.

In naming the species, Britt and his team, which included BYU Museum of Paleontology curator Rod Scheetz and biology professor Michael Whiting, decided to pay tribute to that gold mine. “We’re honoring the city of Moab and the State of Utah because they were so supportive of our excavation efforts over the decades it’s taken us to pull the animal out of the ground,” Britt said, referencing the digs that began when he was a BYU geology student in the late ’70s.

A previous study indicates that a large number of Moabosaurus and other dinosaurs died in a severe drought. Survivors trampled their fallen companions’ bodies, crushing their bones. After the drought ended, streams eroded the land, and transported the bones a short distance, where they were again trampled. Meanwhile, insects in the soils fed on the bones, leaving behind tell-tale burrow marks.

“We’re lucky to get anything out of this site,” Britt said. “Most bones we find are fragmentary, so only a small percentage of them are usable. And that’s why it took so long to get this animal put together: we had to collect huge numbers of bones in order to get enough that were complete.”

BYU has a legacy of collecting dinosaurs that started in the early 1960s, and Britt and colleagues are continuing their excavation efforts in eastern Utah. Moabosaurus now joins a range of other findings currently on display at BYU’s Museum of Paleontology — though, until its placard is updated, it’s identified as “Not yet named” (pronunciation: NOT-yet-NAIM-ed).

“Sure, we could find bones at other places in the world, but we find so many right here in Utah,” Britt said. “You don’t have to travel the world to discover new animals.”

Triassic dinosaur predecessors, new research


This video says about itself:

Meet Teleocrater, a Croc-Like Early Dinosaur Relative

12 April 2017

A 245-million-year-old creature with crocodilian-like legs is an early relative of dinosaurs.

From Virginia Tech in the USA:

Early dinosaur cousin had a surprising croc-like look

Paleobiologist’s latest discovery of Teleocrater rhadinus has overturned popular predictions

April 12, 2017

Summary: Teleocrater and other recently discovered dinosaur cousins show that these animals were widespread during the Triassic Period and lived in modern day Russia, India, and Brazil. Furthermore, these cousins existed and went extinct before dinosaurs even appeared in the fossil record.

For decades, scientists have wondered what the earliest dinosaur relatives looked like. Most assumed that they would look like miniature dinosaurs, be about the size of a chicken, and walk on two legs.

A Virginia Tech paleobiologist’s latest discovery of Teleocrater rhadinus, however, has overturned popular predictions. This carnivorous creature, unearthed in southern Tanzania, was approximately seven to 10 feet long, with a long neck and tail, and instead of walking on two legs, it walked on four crocodylian-like legs.

The finding, published in the journal Nature April 12, fills a critical gap in the fossil record. Teleocrater, living more than 245 million years ago during the Triassic Period, pre-dated dinosaurs. It shows up in the fossil record right after a large group of reptiles known as archosaurs split into a bird branch (leading to dinosaurs and eventually birds) and a crocodile branch (eventually leading to today’s alligators and crocodiles). Teleocrater and its kin are the earliest known members of the bird branch of the archosaurs.

“The discovery of such an important new species is a once-in-a-lifetime experience,” said Sterling Nesbitt, an assistant professor of geosciences in the College of Science.

He and Michelle Stocker, a co-author and also an assistant professor of geosciences in the College of Science, will give a free public talk with the fossils at 7 p.m. Thursday, April 13, 2017 at the Virginia Tech Museum of Geosciences on the second floor of Derring Hall.

Teleocrater fossils were first discovered in Tanzania in 1933 by paleontologist F. Rex Parrington, and the specimens were first studied by Alan J. Charig, former Curator of Fossil Reptiles, Amphibians and Birds at the Natural History Museum of London, in the 1950s.

Largely because the first specimen lacked crucial bones, such as the ankle bones, Charig could not determine whether Teleocrater was more closely related to crocodylians or to dinosaurs. Unfortunately, he died before he was able to complete his studies. The new specimens of Teleocrater, found in 2015, clear those questions up. The intact ankle bones and other parts of the skeleton helped scientists determine that the species is one of the oldest members of the archosaur tree and had a crocodylian look.

Nesbitt and co-authors chose to honor Charig’s original work by using the name he picked out for the animal, Teleocrater rhadinus, which means “slender complete basin” and refers to the animal’s lean build and closed hip socket.

“The discovery of Teleocrater fundamentally changes our ideas about the earliest history of dinosaur relatives,” said Nesbitt. “It also raises far more questions than it answers.”

“This research sheds light on the distribution and diversity of the ancestors of crocodiles, birds, and dinosaurs,” says Judy Skog, program director in the National Science Foundation’s Division of Earth Sciences, “and indicates that dinosaur origins should be re-examined now that we know more about the complex history and traits of these early ancestors.”

Teleocrater and other recently discovered dinosaur cousins show that these animals were widespread during the Triassic Period and lived in modern day Russia, India, and Brazil. Furthermore, these cousins existed and went extinct before dinosaurs even appeared in the fossil record.

The team’s next steps are to go back to southern Tanzania this May to find more remains and missing parts of the Teleocrater skeleton. They will also continue to clean the bones of Teleocrater and other animals from the dig site in the paleontology preparation lab in Derring Hall.

“It’s so exciting to solve puzzles like Teleocrater, where we can finally tease apart some of these tricky mixed assemblages of fossils and shed some light on broader anatomical and biogeographic trends in an iconic group of animals,” said Stocker.

Stocker and Nesbitt are both researchers with the Global Change Center at Virginia Tech. Other co-authors on the paper include: Richard J. Butler with the University of Birmingham; Martin D. Ezcurra with Museo Argentino de Ciencias Naturales; Paul M. Barrett with the Natural History Museum of London; Kenneth D. Angielczyk with the Field Museum of Natural History; Roger M. H. Smith with the University of the Witwatersrand and Iziko South African Museum; Christian A. Sidor with the University of Washington; Grzegorz Niedzwiedzki with Uppsala University; Andrey G. Sennikov with Borissiak Paleontological Institute and Kazan Federal Univeristy; and Charig.

The research was funded by the National Science Foundation, National Geographic Society, a Marie Curie Career Integration Grant, a National Geographic Society for Young Explorers grant, and the Russian Government Program of Competitive Growth of Kazan Federal University.

See also here.

Ancient saber-toothed cat skull discovery in Germany


This video says about itself:

12 August 2015

“Homotherium” is an extinct genus of machairodontine saber-toothed cats, often termed “scimitar-toothed cats”, that ranged from North America, South America, Eurasia, and Africa during the Pliocene and Pleistocene epochs.

It first became extinct in Africa some 1.5 million years ago. In Eurasia it survived until about 30,000 years ago. In South America it is only known from a few remains in the northern region, from the mid-Pleistocene. The most recent remains of Homotherium date to 28,000 years BP.

Homotherium” reached 1.1 m at the shoulder and weighed an estimated 150 [kilogram] – and was therefore about the size of a male African lion. Compared to some other machairodonts, like “Smilodon” or “Megantereon”, “Homotherium” had shorter upper canines, but they were flat, serrated and longer than those of any living cat. Incisors and lower canines formed a powerful puncturing and gripping device. Among living cats, only the tiger has such large incisors, which aid in lifting and carrying prey. The molars of “Homotherium” were rather weak and not adapted for bone crushing. The skull was longer than in “Smilodon” and had a well-developed crest, where muscles were attached to power the lower jaw. This jaw had down-turned forward flanges to protect the scimitars. Its large canine teeth were crenulated and designed for slashing rather than purely stabbing.

It had the general appearance of a cat, but some of its physical characteristics are rather unusual for a large cat. The limb proportions of “Homotherium” gave it a hyena-like appearance. The forelegs were elongated, while the hind quarters were rather squat with feet perhaps partially plantigrade, causing the back to slope towards the short tail. Features of the hind limbs indicate that this cat was moderately capable of leaping. The pelvic region, including the sacral vertebrae, was bear-like, as was the short tail composed of 13 vertebrae—about half the number of long-tailed cats.

From the Senckenberg Research Institute and Natural History Museum in Germany:

Skull of saber-toothed cat found almost complete

Third individual saber-toothed cat was discovered in Schöningen

April 12, 2017

Summary: An excavation team found the remains of a saber-toothed cat at the archeological site in Schöningen. An examination of the skull fragments revealed the animal to be a representative of the European saber-toothed cat, Homotherium latidens. The recent discovery constitutes the third example of this large predatory cat from Schöningen.

Led by scientists of the Senckenberg Research Institute and the University of Tübingen, the excavation team found the remains of a saber-toothed cat at the archeological site in Schöningen. An examination of the skull fragments at the Dutch University of Leiden revealed the animal to be a representative of the European saber-toothed cat, Homotherium latidens. The recent discovery constitutes the third example of this large predatory cat from Schöningen.

Long claws, razor-sharp, curved canine teeth and the size of a fully grown lion: the saber-toothed cat (Homotherium latidens) was a competitor as well as a dangerous predator that even posed a risk to the humans of its time. “In the course of our excavation in May 2015, we came across conspicuous bone fragments,” explains Dr. Jordi Serangeli, a scientist at the University of Tübingen and the excavation leader at the approximately 300,000-year-old archeological site, and he continues, “In total, there are three individuals of Homotherium present in these relatively young sediment layers.

Until the first discovery of a saber-toothed cat in 2012 at the Schöningen excavation site in Lower Saxony it had been assumed that the large cats were already extinct about 200,000 years earlier, i.e., around 500,000 years ago. “Our findings show that 300,000 years ago, the saber-toothed cats were not as rare as previously thought,” adds Serangeli.

During a restoration in 2016, André Ramcharan and Ivo Verheijen at the University of Leiden were able to reassemble the eleven bone fragments into an almost complete neurocranium. “We then compared the reconstructed skull with recent and already extinct species of large carnivores and were thus able to demonstrate that the remains represented the head of a European saber-toothed cat,” explains Professor Dr. Thijs van Kolfschoten of the University of Leiden.

The third saber-toothed cat specimen that was discovered offers a great potential: thanks to the excellent level of preservation at the Schöningen dig, the interior of the skull reflects the shape and structure of the Homotherium brain. By examining the detailed brain structures, the team of scientists hopes to gain insights into the visual and hearing abilities as well as the feeding habits of the large cats. “The third Homotherium from Schöningen is invaluable for our understanding of the European saber-toothed cat,” summarizes Professor Nicholas Conard of the Senckenberg Centre for Human Evolution and Palaeoenvironment and head of the Institute for Early Prehistory and Quaternary Ecology at the University of Tübingen.

In the near future the international team from the Schöningen project intends to publish the results of its interdisciplinary studies regarding the three saber-toothed cats discovered to date. “Moreover, we expect that future digs will produce additional Homotherium finds,” offers Serangeli as a preview.

The dig in Schöningen keeps a team of ten members employed full-time — and during the main excavation season, the team is joined by five to ten students, who support the scientific excavation. Worldwide, about 50 scientists from 30 institutions and a wide variety of disciplines are involved in researching the discoveries from Schöningen. The dig is financed by the State of Lower Saxony.

The spectacular new discovery is put on display for the public at the palaeon in Schöningen as part of the special exhibition “The Ice Age Huntress.” Thanks to the close cooperation between Senckenberg, the international partners and the der palaeon GmbH, it is possible to make spectacular scientific findings available to the public in a timely manner.

Fossil marsupials discovery in Bolivia


This video says about itself:

24 April 2015

The Evolution Of Mammals

Description: The word “mammal” is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from the Latin mamma (“teat, pap”). All female mammals nurse their young with milk, which is secreted from special glands, the mammary glands.

According to Mammal Species of the World, 5,416 species were known in 2006. These were grouped in 1,229 genera, 153 families and 29 orders.[1] In 2008 the IUCN completed a five-year, 1,700-scientist Global Mammal Assessment for its IUCN Red List, which counted 5,488 accepted species at the end of that period.[2] In some classifications, the mammals are divided into two subclasses (not counting fossils): the Prototheria (order of Monotremata) and the Theria, the latter composed of the infraclasses Metatheria and Eutheria. The marsupials constitute the crown group of the Metatheria and therefore include all living metatherians as well as many extinct ones; the placentals likewise constitute the crown group of the Eutheria.

From Case Western Reserve University in the USA:

Three new species of extinct South American marsupials discovered

Findings show the family, Palaeothentidae, was once widespread across the continent but add to extinction doubts

April 11, 2017

The discovery of three extinct species and new insights to a fourth indicates a little-known family of marsupials, the Palaeothentidae, was diverse and existed over a wide range of South America as recent as 13 million years ago. Fossils of the new species were found at Quebrada Honda, a high elevation fossil site in southern Bolivia, and are among the youngest known palaeothentid fossils.

The discovery of three extinct species and new insights to a fourth indicates a little-known family of marsupials, the Palaeothentidae, was diverse and existed over a wide range of South America as recent as 13 million years ago.

The finding, however, complicates the question: why did these animals go extinct?

“It was previously assumed this group slowly went extinct over a long time period, but that’s probably not the case,” said Russell Engelman, a biology MS student at Case Western Reserve and lead author of a new study on the group. “They were doing very well at the time they were supposedly on death’s door.”

Discovering new fossil sites may be the only way to learn the answer, researchers say.

Engelman; along with Federico Anaya, professor of geological engineering at Universidad Autónoma Tomás Frías, in Potosí, Bolivia; and Darin Croft, anatomy professor at Case Western Reserve School of Medicine, describe the animals, where they fit in the family, and their paleoecology and paleobiology in the Journal of Systematic Palaeontology.

Fossils of the new species were found at Quebrada Honda, a high elevation fossil site in southern Bolivia. They are about 13 million years old (from the middle Miocene epoch), placing them among the youngest known palaeothentid fossils.

Fossil remains of other members of the family, and other relatives within the order Paucituberculata, have been found at sites of similar age in southwestern Colombia and possibly southern Argentina, geographically spanning almost the entire continent.

“The only close relatives of palaeothentids alive today are shrew opossums, small, poorly-known, ground-living marsupials that live in and near the Andes,” Croft said. “Palaeothentid marsupials once included a diversity of species that filled a variety of roles in ancient ecosystems. During their heyday in the Miocene, they were abundant.”

The new species, Palaeothentes serratus, Palaeothentes relictus, and Chimeralestes ambiguus, all had long snouts but differed in diet and body size and other features.

The researchers suggest P. serratus — serratus means saw-like — was an insectivore, with well-developed slicing premolars. The researchers estimate the mouse-size marsupial weighed about 3.5 ounces.

P. relictus had large, well-developed grinding molars. The animal probably ate fruits, seeds and insects, and weighed about five ounces.

C. ambiguus, as the name indicates, has attributes of a number of family members, making its evolutionary relationships with the group uncertain. The animal was about the same size as P. serratus and its limited dental remains indicate its diet was likely similar to that of P. relictus.

The most common member of the family found at Quebrada Honda is Acdestis maddeni. The species was named 14 years ago, but the researchers are the first to find and analyze its lower jaw.

These lower jaw fossils, combined with reexamination of other specimens, show that the skull of Acdestis was different from other palaeothentids. A. maddeni’s snout is short and its canines are relatively large, followed by large, shearing middle teeth and molars well developed for grinding.

“All this indicates it was a generalist,” Engelman said. “Although it could eat fruits and insects like its relatives it could also catch small vertebrates and dismember them… It probably ate anything, like a hedgehog or Norway rat does.”

The animal was rat-size and weighed about a pound, the researchers estimate.

The fossil record indicates the Palaeothentidae and much of the order Paucituberculata abruptly went extinct about 12 million years ago, leaving only the lineage leading to modern shrew-opossums.

“Most species threatened with extinction are like giant pandas: highly specialized, live only in a certain area and eat only certain things,” Engelman said. Due to their diversity and wide range, “the Palaeothentidae didn’t fit the pattern of extinction.”

Previous hypotheses that palaeothentids were done in by climate change or competition lack support, the researchers say.

For example, fossils found at high latitudes in Argentina and Bolivia after the Middle Miocene Climatic Optimum indicate they withstood the dramatic cooling of the period. The family and opossums, which may have been competitors, appear to have overlapped for nearly 10 million years. Yet opossums didn’t become abundant until 3 million to 4 million years after the family went extinct.

But, the hypothesis cannot be completely ruled out, the researchers said. And, there is a possibility the decline of the family was slow.

The reason for the quandary is that fossils have been well collected in the southern end of South America but the middle and northern parts of the continent remain largely unexplored.

“It’s as if all the fossils in the U.S. came from Florida — you don’t get the full picture,” Engelman said.

If new fossil sites are found in the northern two-thirds of the continent, “it will be interesting to see whether we find younger members of the group,” Croft said. “That will help us understand their extinction.”