Dinosaur age and modern frog discoveries


This 14 June 2018 video says about itself:

Frogs trapped in amber for 99 million years are giving a glimpse of a lost world. The tiny creatures have been preserved in sticky tree resin from the later part of the Age of the Dinosaurs.

From the Florida Museum of Natural History in the USA:

Amber fossils provide oldest evidence of frogs in wet, tropical forests

June 14, 2018

Summary: 99-million-year-old amber fossils from Myanmar provide the earliest evidence of frogs in wet, tropical forests.

About 99 million years ago, a tiny juvenile frog in present-day Myanmar was suddenly trapped in sap with a beetle, perhaps its intended next meal.

Unlucky for the frog, but lucky for science.

An extinct species now named Electrorana limoae, it’s one of four fossils that provide the earliest direct evidence of frogs living in wet, tropical forests and are the oldest-known examples of frogs preserved in amber.

“It’s almost unheard of to get a fossil frog from this time period that is small, has preservation of small bones and is mostly three-dimensional. This is pretty special,” said David Blackburn, study co-author and the associate curator of herpetology at the Florida Museum of Natural History. “But what’s most exciting about this animal is its context. These frogs were part of a tropical ecosystem that, in some ways, might not have been that different to what we find today — minus the dinosaurs.”

The findings and species description were published today in Nature’s Scientific Reports.

Frogs have been around for at least 200 million years, but glimpsing their early heyday is tough. Often small and lightly built, frogs don’t tend to preserve well. The frog fossil record skews toward more robust species from arid, seasonal environments, although the bulk of frog diversity today lives in tropical forests.

“Ask any kid what lives in a rainforest, and frogs are on the list”, Blackburn said. “But surprisingly, we have almost nothing from the fossil record to say that’s a longstanding association.”

The amber deposits of northern Myanmar in Southeast Asia provide a unique record of ancient forest ecosystems, with fossil evidence of mosses, bamboo-like plants, aquatic spiders and velvet worms. The discovery of Electrorana and the other fossils, the first frogs to be recovered from these deposits, help add to our understanding of frogs in the Cretaceous period, showing they have inhabited wet, tropical forests for at least 99 million years.

Frogs in amber are quite rare, with previous examples found in the Dominican Republic and Mexico and dating back only about 40 million and 25 million years, respectively.

Less than an inch long, Electrorana is the most well-preserved of the group. Clearly visible in the amber are the frog’s skull, its forelimbs, part of its backbone, a partial hind limb and the unidentified beetle. The other amber fossils contain two hands and an imprint of a frog that likely decayed inside the resin.

But Electrorana raises more questions than it answers, Blackburn said.

Many characteristics herpetologists use to discern details of a frog’s life history and determine how it’s related to other frogs — wrist bones, the pelvis, hip bones, the inner ear, the top of the backbone — are either missing or were not yet fully developed in the juvenile frog.

The existing bones provide clues about Electrorana’s possible living relatives, Blackburn said, but the results are puzzling: Species that have similar features include fire-bellied toads and midwife toads — Eurasian species that live in temperate, not tropical, ecosystems.

Gathering CT skeletal data for both living and extinct frogs, one of Blackburn’s long-term projects, could help illuminate ancient evolutionary relationships, possibly clarifying how Electrorana fits into the frog tree of life.

In the meantime, Blackburn nurtures the hope that other frogs in amber will be discovered, making Electrorana more than a one-hit wonder.

“We don’t have a lot of single-species frog communities in forests. It seems extremely unlikely that there’s only one. There could be a lot more fossils coming.”

In a new study, researchers have investigated how the endocrine-disrupting substance linuron affects reproduction in the West African clawed frog, Xenopus tropicalis. The scientists found that linuron, which is used as a pesticicide, impaired the males’ fertility, and that tadpoles developed ovaries instead of testicles to a greater extent, which caused a female-biased sex ratio: here.

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At least five new giant salamander species discovery


This video says about itself:

At Least Five New Giant Salamander Species Identified | Nat Geo Wild

3 June 2018

Researchers have found that there is not one, but at least five species of Chinese giant salamander, and possibly up to eight.

Fish-amphibian transition fossils discovered in South Africa


This video from South Africa says about itself:

The Centre of Excellence in Palaeosciences based at the University of the Witwatersrand today announced the discovery of two new Devonian tetrapod species and the first Devonian tetrapods discovered in Africa (8 June 2018). The species have been named Tutusius umlambo (named in honour of Archbishop Emeritus Desmond Tutu) and Umzantsia amazana and were discovered by Dr Rob Gess of the Albany Museum and supported by the Millenium Trust.

Thank you to Rhodes University journalism department for the video clip.

From the Times in South Africa:

Not so fishy: Africa’s first ever fish-with-legs discovered

07 June 2018 – 20:07

By Tanya Farber

An extraordinary find has been made near the university town of Grahamstown in the Eastern Cape.

Up until today‚ when a paper was published in Science‚ it was believed that Devonian tetrapods (fish that had developed four legs as the evolution from aquatic to land animals began) had only existed in the tropics.

But‚ in a groundbreaking study that shakes up our entire notion of the moment we adapted to move beyond the water‚ it has now been discovered that that is simply not true.

The newly discovered tetrapods – which would have resembled a cross between a crocodile and a fish‚ with a crocodile-like head‚ stubby legs‚ and a tail with a fish-like fin – were found in the Devonian Waterloo Farm near Grahamstown‚ and were living within the Antarctic circle some 360 million years ago.

The two new species are named Tutusius and Umzantsia. The metre-long Tutusius umlambo‚ named in honour of Archbishop Emeritus Desmond Tutu‚ and the somewhat smaller Umzantsia amazana‚ are both incomplete.

Tutusius is represented by a single bone from the shoulder girdle‚ whereas Umzantsia is known from a greater number of bones‚ but they both appear similar to previously known Devonian tetrapods.

This find represents two dramatic shifts. Firstly, it means the first appearance of tetrapods on African soil shifts to 70-million years earlier than thought‚ but it also means that one of the most fundamental understandings of our shift from the water to the land has to be reassessed.

The evolution of tetrapods from fish during the Devonian period was a major turning point in our ancestry‚ and all research on that turning point has up until now‚ hinged on the fact that this happened (or so we thought) between 30 degrees north and south of the equator. Almost all come from Laurussia‚ a supercontinent that later fragmented into North America‚ Greenland and Europe.

“Whereas all previously found Devonian tetrapods came from localities which were in tropical regions during the Devonian‚ these specimens lived within the Antarctic circle”, explains lead author‚ Dr Robert Gess of the Albany Museum in Grahamstown‚ and co-author Professor Per Ahlberg of Uppsala University in Sweden.

Minister of Science and Technology‚ Mmamoloko Kubayi-Ngubane‚ congratulated Dr Gess‚ saying this groundbreaking discovery places South Africa at the forefront of the study of the evolution of land-living vertebrate animals‚ including the ancestry of all the wildlife we see in the country’s game parks.

The research was supported by the South African DST-NRF Centre of Excellence in Palaeosciences‚ based at the University of the Witwatersrand and the Millennium Trust.

See also here.

Poison dart frogs’ colours, also camouflage


This 2016 terrarium video says about itself:

Dendrobates tinctorius ‘Powder Blue’ Calling.

Male dart frog vocalizing while female (barely seen) climbs the glass attempting to get to him.

From the University of Bristol in England:

Bright warning colors on poison dart frogs also act as camouflage

June 4, 2018

Poison dart frogs are well known for their deadly toxins and bright colours, which have made them a classic example of warning coloration.

The Dyeing Dart Frog, for example, is highly toxic and warns its predators with a bright yellow-and-black pattern.

However, new research led by scientists at the University of Bristol has revealed that the colour pattern does more than simply signal “danger.” Counterintuitively, it also works as camouflage.

Lead author, Jim Barnett completed this research, published today in the journal Proceedings of the National Academy of Sciences, while studying for a PhD at Bristol. He is now based at McGill University in Canada.

He said: “Effective as warning signals are, it’s not necessarily the best strategy to be maximally conspicuous.

Certain predators have evolved tolerance of toxins that would be deadly for humans, and some individual predators may have not encountered the warning signal prey before (a dangerous mistake for the predator, but also for the frog).

“So, colour patterns that could be distinctive close-up, but work as camouflage from a distance, would provide a clear advantage.”

Combining fieldwork in the jungles of French Guiana, computational modelling, and laboratory visual search experiments, Barnett and colleagues from the University of Bristol’s School of Biological Sciences and the School of Experimental Psychology investigated how the Dyeing Dart Frog uses its colours to balance the benefits of effective warning signals with the advantages of concealment.

They found that, despite being highly conspicuous at close range, the particular colours and their arrangement allow the pattern to blend together to form background-matching camouflage when viewed from a distance.

The frog’s pattern, therefore, allows it to get the best of both worlds: high fidelity camouflage until a predator discovers it, at which point its bright, highly salient, warning signal becomes clear.

Co-author Professor Innes Cuthill from the University of Bristol added: “How many other animals use ‘distance-dependent coloration’ to balance competing evolutionary pressures is yet to be explored.

“Being able to signal when close to a would-be mate, whilst remaining inconspicuous to more distant predators would seem beneficial. So too for human applications such as military camouflage, where recognition by allies is as important as concealment from foes. Also, signage that only need be clear at the distance where the information is needed, but might be distracting if detected earlier.”

Oldest amphibians not in freshwater


This 2015 video is called Ancestral Evolution – Ichthyostega to Varanops.

By Carolyn Gramling, 5:29pm, May 30, 2018:

The first land-walking vertebrates may have emerged from salty estuaries

An analysis casts doubt on views that the ancient creatures arose in freshwater

Earth’s earliest land-walking vertebrates didn’t paddle about in freshwater lakes or rivers. Instead, these four-footed creatures, which appeared about 375 million years ago, lived in the brackish waters of an estuary or delta, researchers report online May 30 in Nature.

Early tetrapods, such as Ichthyostega and Acanthostega, lived an amphibious existence between land and sea: They had feet, but also gills and tails made for swimming. A new study by paleontologist Jean Goedert of Université Lyon in France and colleagues suggests that the animals also could have tolerated rapid changes in salinity, such as is found in an estuary.

The researchers analyzed sulfur and oxygen isotopes — forms of these elements with the same number of protons, but different masses — in 51 fossilized tetrapod bones from locations in what’s now Greenland and China. Compared with freshwater, seawater has a higher ratio of the sulfur-34 isotope relative to sulfur-32. The tetrapod bones tended to show elevated sulfur-34, the researchers report, suggesting that the creatures spent at least some time in seawater. But oxygen isotope analyses of the bones show that freshwater was also present, arguing against a purely salty environment such as an ocean.

The results challenge a long-held view that the earliest tetrapods emerged from freshwaters, such as rivers or lakes. In 1929, the first Ichthyostega fossils were found in a series of red sandstone layers in eastern Greenland that geologists once thought had been deposited in a freshwater environment. But later discoveries of tetrapod fossils found associated with known marine species suggested that the early walkers may have lived in saltier waters than once thought.

An ability to tolerate different salinity environments could have helped tetrapods — a group that includes today’s amphibians, reptiles and mammals — survive a mass extinction of ocean-dwellers that occurred by the end of the Devonian Period about 359 million years ago, the researchers say.

Threatened giant Chinese salamander not one, but five species


This video says about itself:

15 December 2015

Scientists have found an ancient giant salamander alive. Experts say it may be 200 years old. The enormous 4.5-foot-long and 115-pound amphibian was lurking in a cave near Chongqing, China.

Read more here.

From ScienceDaily:

Giant Chinese salamander is at least five distinct species, all heading toward extinction

May 21, 2018

With individuals weighing in at more than 140 pounds, the critically endangered Chinese giant salamander is well known as the world’s largest amphibian. But researchers reporting in the journal Current Biology on May 21 now find that those giant salamanders aren’t one species, but five, and possibly as many as eight. The bad news as highlighted by another report appearing in the same issue is that all of the salamanders — once thought to occur widely across China — now face the imminent threat of extinction in the wild, due in no small part to demand for the amphibians as luxury food.

The discoveries highlight the importance of genetic assessments to properly identify the salamanders, the researchers say. It also suggests that the farming and release of giant salamanders back into the wild without any regard for their genetic differences is putting the salamanders’ already dire future at even greater risk. In fact, some of the five newly identified species may already be extinct in the wild.

“We were not surprised to discover more than one species, as an earlier study suggested, but the extent of diversity — perhaps up to eight species — uncovered by the analyses sat us back in our chairs”, says Jing Che from the Kunming Institute of Zoology, Chinese Academy of Sciences. “This was not expected.”

“The overexploitation of these incredible animals for human consumption has had a catastrophic effect on their numbers in the wild over an amazingly short time span”, adds Samuel Turvey, from ZSL (Zoological Society of London. “Unless coordinated conservation measures are put in place as a matter of urgency, the future of the world’s largest amphibian is in serious jeopardy.”

The researchers were surprised to learn just how much movement of salamanders has already occurred due to human intervention. Salamander farms have sought to “maximize variation” by exchanging salamanders from distant areas, without realizing they are in fact distinct species, Che explains. As a result, she says, wild populations may now be at risk of becoming locally maladapted due to hybridization across species boundaries.

The researchers including Ya-Ping Zhang and Robert Murphy suspected Chinese giant salamanders might represent distinct species despite their similar appearances. That’s because the salamanders inhabit three primary rivers in China, and several smaller ones, they explain. Each runs independently to sea.

Given that giant salamanders can’t move across the land, they suspected that salamanders living in different river systems might have had opportunity to diverge over time into what should now be recognized as distinct species. And, indeed, that’s exactly what the genetic evidence now suggests.

In the second study, Turvey and colleagues conducted field surveys and interviews from 2013 and 2016, in an effort that was possibly the largest wildlife survey ever conducted in China. The data revealed that populations of this once-widespread species are now critically depleted or extirpated across all surveyed areas of their range, and illegal poaching is widespread. The researchers were unable to confirm survival of wild salamanders at any survey site.

While the harvesting of wild salamanders is already prohibited, the findings show that farming practices and existing conservation activities that treat all salamander populations as a single species are potentially doing great damage, the researchers say.

“Conservation strategies for the Chinese giant salamander require urgent updating”, Che says. She says it is especially critical to reconsider the design of reserves to protect the salamanders and an effort that has already released thousands of farm-started baby salamanders back into the wild.

“Together with addressing wider pressures such as poaching for commercial farms and habitat loss, it’s essential that suitable safeguards are put in place to protect the unique genetic lineage of these amazing animals”, says Fang Yan, also at the Kunming Institute.