Fossil teeth from Kenya solve ancient monkey mystery

Date:  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.

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Change of teeth causes yo-yo effect in elephants' weight

Date:  January 9, 2019

Source:  University of Zurich

The teeth of most mammals, including humans, are only replaced once in a lifetime, when the milk teeth give way to the permanent teeth. This one change is enough to adapt to the increasing size of the jaw. But elephants increase greatly in size and weight over the course of their lives -- from a starting weight of 100 kilograms to several tons in adulthood. One single change of teeth would not be enough for the enormous growth of the jaw.

Elephants' teeth change five times

That's why the teeth of elephants are replaced a total of five times over their lifespan. On each side of the jaw they have only one single tooth in use at a time which is slowly pushed forwards by a new bigger tooth out of the mouth, breaking off in pieces. If you look inside an elephant's mouth you will see either only one single tooth or pieces of the old tooth behind which part of the new tooth is pushing through, a process that is called molar progression.

As a result of this process, the elephants' chewing surface gets bigger when two teeth are present on one side at the same time, and then smaller again when there is only one tooth on each side. For that reason there are times when it is easier for the animals to eat more or chew the same amount more finely, and hence increase the intake of digestible food.

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Some prehistoric horses were homebodies

Geochemical analysis of fossil teeth shows horses in Florida did not make epic migrations

Date:  December 19, 2018

Source:  University of Cincinnati

Summary:

A strontium analysis of fossilized horse teeth from Florida found that the animals did not travel far from where they were born. Researchers also found evidence that prehistoric horses fed along the coast like wild horses do today at places like Assateague Island National Seashore.

Unlike today's zebras, prehistoric horses in parts of North America did not make epic migrations to find food or fresh water, according to a new study by the University of Cincinnati.

The findings suggest Florida was something of a horse paradise 5 million years ago, providing everything the animals could want in a relatively small area.

The study was published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

Plains zebras and Mongolian wild horses take on epic migrations each year to find water or green grass.

The Mongolian wild horse, also known as a Przewalski's horse, travels as much as 13 miles per day. And Burchell's zebras in southern Africa are known for their seasonal migrations that take them as far as 300 miles and back as they follow the rains to green grass.

But geologists in UC's McMicken College of Arts and Sciences found that prehistoric horses in coastal Florida lived and died within a comparatively small area.

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World's 'first named dinosaur' reveals new teeth with scanning tech

June 7, 2017

Pioneering technology has shed fresh light on the world's first scientifically-described dinosaur fossil - over 200 years after it was first discovered - thanks to research by WMG at the University of Warwick and the University of Oxford's Museum of Natural History.

Professor Mark Williams at WMG has revealed five previously unseen teeth in the jawbone of the Megalosaurus - and that historical repairs on the fossil may have been less extensive than previously thought.

Using state of the art CT scanning technology and specialist 3D analysis software, Professor Williams took more than 3000 X-ray images of the world-famous Megalosaurus jawbone, creating a digital three-dimensional image of the fossil.

In an unprecedented level of analysis, Professor Williams at WMG was able to see inside the jawbone for the first time, tracing the roots of teeth and the extent of different repairs.

Some damage occurred to the specimen when it was removed from the rock, possibly shortly after it was discovered.

Records at the Oxford University Museum of Natural History suggest that some restoration work may have been undertaken by a museum assistant between 1927 and 1931, while repairing the specimen for display - but there are no details about the extent of the repairs or the materials used.

The scans have revealed previously unseen teeth that were growing deep within the jaw before the animal died - including the remains of old, worn teeth and also tiny newly growing teeth.

The scans also show the true extent of repairs on the fossil for the first time, revealing that there may have been at least two phases of repair, using different types of plaster. This new information will help the museum make important decisions about any future restoration work on the specimen.

This research was made possible through a collaboration between Professor Williams' research group at WMG, University of Warwick - including PhD researcher Paul Wilson - and Professor Paul Smith, director of the Oxford University Museum of Natural History.

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These dinosaurs lost their teeth as they grew up

December 22, 2016

 

By comparing the fossilized remains of 13 ceratosaurian theropod dinosaurs known as Limusaurus inextricabilis collected from the Upper Jurassic Shishugou Formation of northwestern China, researchers have been able to reconstruct the dinosaur's growth and development from a young hatchling of less than a year to the age of 10. The findings, reported in Current Biology on December 22, uncovered something unexpected: the dinosaurs had teeth as young juveniles that were gradually lost as they grew up.

"We found a very rare, very interesting phenomenon in a ceratosaurian dinosaur whereby toothed jaws in juvenile individuals transition to a completely toothless beaked jaw in more mature individuals during development," says Shuo Wang of Capital Normal University in Beijing, China.

The findings make Limusaurus the first known reptile with the characteristic known as ontogenetic edentulism (meaning tooth reduction or loss in development). Together with other evidence, they led the researchers to conclude that the toothed juveniles were probably omnivorous meat-eaters. The beaked adults most likely transitioned to a plant-based diet.

Wang and colleagues first reported on this ceratosaurian back in 2001. At that point, they had collected just one fossilized juvenile, and they didn't yet know what it was. Over the course of the next several years, more specimens were found. But it wasn't clear that they all belonged to the same species.

"Initially, we believed that we found two different ceratosaurian dinosaurs from the Wucaiwan Area, one toothed and the other toothless, and we even started to describe them separately," Wang says.

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Hippo teeth reveal environmental change

Changed plant types associated with loss of elephants in Ugandan national park

Date: September 12, 2016

Source: University of Utah

Loss of megaherbivores such as elephants and hippos can allow woody plants and non-grassy herbs and flowering plants to encroach on grasslands in African national parks, according to a new University of Utah study, published Sept. 12 in Scientific Reports. The study used isotopes in hippopotamus teeth to find a shift in the diet of hippos over the course of a decade in Uganda's Queen Elizabeth National Park following widespread elephant poaching in the 1970s.

Study first author and U postdoctoral scholar Kendra Chritz says that her method of using hippo enamel isotopes could help scientists reconstruct past changes in vegetation in Africa's national parks, areas with relatively little ongoing scientific observation. The results could give ecologists an idea of what could happen to Africa's grasslands if elephants, whose populations are steeply declining, went extinct or reached near-extinction.

"We have a window into what these environments could look like without megaherbivores, and it's kind of grim," Chritz says.

Competing plant classes

Grasslands are an important ecosystem in Africa, hosting many animals and serving as corridors for wildlife movement. Lowland tropical grasses, such as those in elephant ecosystems, are part of the C4 class of plants, a reference to the enzyme used to process carbon dioxide into sugars during photosynthesis. Corn and sugarcane are also C4 plants. C3 plants, which use a different enzyme, include trees, shrubs, flowering plants and herbs. C3 plants compete for resources with C4 grasses in African savannas, including sunlight. Elephants and other megaherbivores help keep woody plant encroachment in check by browsing seasonally on shrubs and trees. But without that herbivore control, C3 plants can advance on grasslands unimpeded.

The presence of shrubs and trees, which can be seen in aerial photographs, give only a partial picture of the balance of power between C3 and C4 plants. Observing herbs and flowering plants requires ground-level observation, and records of such observations in Uganda's Queen Elizabeth National Park, and many national parks in Africa, is sparse.

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How do shark teeth bite? Reciprocating saw, glue provide answers

Date: September 8, 2016

Source: University of Washington

Sharks have a big reputation for their teeth. The ocean predators use their buzz saw mouths to efficiently dismantle prey, ranging from marine mammals and sea turtles to seabirds and -- as Hollywood likes to remind us -- an occasional human.

There are more than 400 species of sharks in the world and each has a unique tooth shape. Some are simple triangles, while others are deeply notched or spear-shaped. But despite this variety, scientists haven't detected a difference in how different shark teeth cut and poke tissue.

A recent University of Washington study sought to understand why shark teeth are shaped differently and what biological advantages various shapes have by testing their performance under realistic conditions. The results appeared in August in the journal Royal Society Open Science.

"When you have all these different tooth shapes, there should be some functional reason. That issue was fundamentally troubling to me," said senior author Adam Summers, a UW professor of biology and of aquatic and fishery sciences. "It seemed likely what we were missing is that sharks move when they eat."

Sharks shake their heads rapidly when they bite their prey, so evaluating how teeth perform while in a side-to-side motion was critical to the study tests, which took place during a summer marine biology course at the UW's Friday Harbor Laboratories on San Juan Island.

Summers and his collaborators affixed three different types of shark teeth to the blade of a reciprocating power saw, then cut through thick slices of Alaska chum salmon at a speed that mimicked the velocity of head-shaking as a shark devours its prey.

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