Tag Archives: #paleo

The “Great Dying” (Paleontology)

Rapid Warming and Monsoonal Intensification Contributed to the Abrupt Collapse of Forest-Mire (Glossopteris) Ecosystems in the High Southern Latitudes

The Paleozoic era culminated 251.9 million years ago in the most severe mass extinction recorded in the geologic record. Known as the “great dying,” this event saw the loss of up to 96% of all marine species and around 70% of terrestrial species, including plants and insects.

The consensus view of scientists is that volcanic activity at the end of the Permian period, associated with the Siberian Traps Large Igneous Province, emitted massive quantities of greenhouse gases into the atmosphere over a short time interval. This caused a spike in global temperatures and a cascade of other deleterious environmental effects.

An international team of researchers from the United States, Sweden, and Australia studied sedimentary deposits in eastern Australia, which span the extinction event and provide a record of changing conditions along a coastal margin that was located in the high latitudes of the southern hemisphere. Here, the extinction event is evident as the abrupt disappearance of Glossopteris forest-mire ecosystems that had flourished in the region for millions of years. Data collected from eight sites in New South Wales and Queensland, Australia were combined with the results of climate models to assess the nature and pace of climate change before, during, and after the extinction event.

Outcrop photos are taken T.D. Frank and are from Frazer Beach, New South Wales, Australia. The end Permian extinction and disappearance of Glossopteris flora occurs at the top of the coal (black layer). © T. D. Frank

Results show that Glossopteris forest-mire ecosystems thrived through the final stages of the Permian period, a time when the climate in the region was gradually warming and becoming increasingly seasonal. The collapse of these lush environments was abrupt, coinciding with a rapid spike in temperatures recorded throughout the region. The post-extinction climate was 10–14°C warmer, and landscapes were no longer persistently wet, but results point to overall higher but more seasonal precipitation consistent with an intensification of a monsoonal climate regime in the high southern latitudes.

Because many areas of the globe experienced abrupt aridification in the wake of the “great dying,” results suggest that high-southern latitudes may have served as important refugia for moisture-loving terrestrial groups.

The rate of present-day global warming rivals that experienced during the “great dying,” but its signature varies regionally, with some areas of the planet experiencing rapid change while other areas remain relatively unaffected. The future effects of climate change on ecosystems will likely be severe. Thus, understanding global patterns of environmental change at the end of the Paleozoic can provide important insights as we navigate rapid climate change today.

The article was published today in the Geological Society of America journal, Geology.

Featured image: Glossopteris leaves. Photo by co-author Chris Mays. © Chris Mays


FEATURED ARTICLE: T.D. Frank; C.R. Fielding; A.M.E. Winguth; K. Savatic; A. Tevyaw; C. Winguth; S. McLoughlin; V. Vajda; C. Mays; R. Nicoll; M. Bocking; J.L. Crowley, “Pace, magnitude, and nature of terrestrial climate change through the End-Permian Extinction in southeastern Gondwana”, Geology, 2021.
URL: https://pubs.geoscienceworld.org/gsa/geology/article/doi/10.1130/G48795.1/598763/Pace-magnitude-and-nature-of-terrestrial-climate


Provided by Geological Society of America

Scientists Found Fossil Evidence Of ‘Hibernation-Like’ State In 250-Million-Year-Old Antarctic Animal (Paleontology)

In a recent paper, scientists at the University of Washington and its Burke Museum of Natural History and Culture report evidence of a hibernation-like state in an animal that lived in Antarctica during the Early Triassic, some 250 million years ago.

Life restoration of Lystrosaurus in a state of torpor. Credit: Crystal Shin

The creature, a member of the genus Lystrosaurus, was a distant relative of mammals. Antarctica during Lystrosaurus’ time lay largely within the Antarctic Circle, like today, and experienced extended periods without sunlight each winter.

The fossils are the oldest evidence of a hibernation-like state in a vertebrate animal, and indicates that torpor—a general term for hibernation and similar states in which animals temporarily lower their metabolic rate to get through a tough season—arose in vertebrates even before mammals and dinosaurs evolved.

Lystrosaurus lived during a dynamic period of our planet’s history, arising just before Earth’s largest mass extinction at the end of the Permian Period—which wiped out about 70% of vertebrate species on land—and somehow surviving it. The stout, four-legged foragers lived another 5 million years into the subsequent Triassic Period and spread across swathes of Earth’s then-single continent, Pangea, which included what is now Antarctica.

This thin-section of the fossilized tusk from an Antarctic Lystrosaurus shows layers of dentine deposited in rings of growth. The tusk grew inward, with the oldest layers at the edge and the youngest layers near the center, where the pulp cavity would have been. At the top right is a close-up view of the layers, with a white bar highlighting a zone indicative of a hibernation-like state. Scale bar is 1 millimeter. Credit: Megan Whitney/Christian Sidor

Paleontologists today find Lystrosaurus fossils in India, China, Russia, parts of Africa and Antarctica. These squat, stubby, creatures—most were roughly pig-sized, but some grew 6 to 8 feet long—had no teeth but bore a pair of tusks in the upper jaw, which they likely employed to forage among ground vegetation and dig for roots and tubers.

Those tusks made Whitney and Sidor’s study possible. Like elephants, Lystrosaurus tusks grew continuously throughout their lives. The cross-sections of fossilized tusks can harbor life-history information about metabolism, growth and stress or strain. Whitney and Sidor compared cross-sections of tusks from six Antarctic Lystrosaurus to cross-sections of four Lystrosaurus from South Africa.

Back in the Triassic, the collection sites in Antarctica were at about 72 degrees south latitude—well within the Antarctic Circle, at 66.3 degrees south. The collection sites in South Africa were more than 550 miles north during the Triassic at 58-61 degrees south latitude, far outside the Antarctic Circle.

The tusks from the two regions showed similar growth patterns, with layers of dentine deposited in concentric circles like tree rings. But the Antarctic fossils harbored an additional feature that was rare or absent in tusks farther north: closely-spaced, thick rings, which likely indicate periods of less deposition due to prolonged stress.

The researchers cannot definitively conclude that Lystrosaurus underwent true hibernation —which is a specific, weeks-long reduction in metabolism, body temperature and activity. The stress could have been caused by another hibernation-like form of torpor, such as a more short-term reduction in metabolism.

Lystrosaurus in Antarctica likely needed some form of hibernation-like adaptation to cope with life near the South Pole. Though Earth was much warmer during the Triassic than today—and parts of Antarctica may have been forested—plants and animals below the Antarctic Circle would still experience extreme annual variations in the amount of daylight, with the sun absent for long periods in winter.

Many other ancient vertebrates at high latitudes may also have used torpor, including hibernation, to cope with the strains of winter, Whitney said. But many famous extinct animals, including the dinosaurs that evolved and spread after Lystrosaurus died out, don’t have teeth that grow continuously.

If analysis of additional Antarctic and South African Lystrosaurus fossils confirms this discovery, it may also settle another debate about these ancient, hearty animals.


References: Whitney, M.R., Sidor, C.A. Evidence of torpor in the tusks of Lystrosaurus from the Early Triassic of Antarctica. Commun Biol 3, 471 (2020). https://doi.org/10.1038/s42003-020-01207-6 link: https://www.nature.com/articles/s42003-020-01207-6

What Did Dinosaurs Sound Like? (Paleontology)

Research paper from 2009’s historical biology attempted to reveal exactly what dinosaurs may have sounded like and let me tell you T-rex probably didn’t roar. Instead, they may ‘hisssss’ or may be nothing at all..

We don’t have any fossilized evidence of dinosaurs voice boxes, because voice boxes are made of flesh so, they don’t fossilized.. But, paleontologist ‘Phil senter’ researched the vocalizations of living dinosaur relatives i.e. Birds and crocodiles..

We all know, 95% DNA of today’s birds evolved from small-dinosaurs not killed by the KT extinction event.. While, 10 million years after that the first shared ancestor of all modern crocodiles evolved..

So, by looking at birds & crocodiles, they figure out what they sounded like.. Well, to roar, animals need a voice box. Crocs have larynx, yeah, just like us, while birds have ‘syrinx’.

But, according to Dr. Julia Clarke, their voice boxes evolved after KT extinction event. Researchers of this study posit dinosaurs couldn’t vocalize at all.. But, this doesnt mean dinosaurs didn’t make noise..

Fig: Lambeosauras

A paper in anatomical records points out, many dinosaurs had nasal cavities, mouths & connective noses.. This connection inside their skull created resonance chambers which allows dinosaurs to create all sorts of sound even without larynx & syrinx..

Lambeosaurus & hadrosaurus had massive resonating crests connected to their breathing tracks which could amplify noises.. Some researchers blew air through them to show they could have produce low frequency sounds just like modern crocodiles. So even though they didn’t roar, dinosaur could have drummed, groan, hiss, gurgles, clicked, rattled & chirped like their modern relatives..


How Did Birds Evolve To Fly? (Paleontology)

You’ve probably heard that birds evolved from dinosaurs, but it’s sometimes hard to understand exactly how that could have happened. Especially the flying part. How does an animal that can’t fly evolve to do so? It’s not like you can take baby steps towards flying; you either can do it or you can’t. Except, maybe that’s not so true. Here’s the story of how birds first took to the sky.

If you’re picturing a six-ton triceratops sprouting little wings, the idea that birds evolved from dinosaurs might sound a little fishy. But when you look at the skeletons of small theropods (given below) and the skeletons of modern chickens, it makes a little more sense.

The most famous proto-bird is probably archaeopteryx, a raven-sized animal that single-handedly demonstrated the link between the two lineages. With its flight-ready wings, full-body plumage, razor-sharp teeth, and long, scaly tail, it’s pretty much the perfect blend of dino and bird — so much so that some people aren’t sure which one it is. The real answer is probably that it’s a little bit of both, or even that every bird is a dinosaur. But all that doesn’t really answer the question of where archaeopteryx came from.

Fig: Paleontologists have long thought that Archaeopteryx fossils, including this one discovered in Germany, placed the dinosaur at the base of the bird evolutionary tree. Recent evidence suggests the beast may have been a birdlike dinosaur.
(Image: © Humboldt Museum für Naturkunde Berlin)

Archaeopteryx seemed to emerge from the fossil record complete with a number of bird-like features, so scientists used to categorize it as a “hopeful monster” — an animal born with major mutations that just so happened to work out well together, in this case, both feathers and wings. But we now know that many dinosaurs had feathers, even big carnivores like yutyrannus. For those dinos, feathers would have been primarily for insulation.

Once you’ve got feathers, bird wings are easy to develop, and the earliest ones took many forms. Just check out the four wings on microraptor. But even before tiny raptors began flying, they likely used small, wing-like limbs for a little extra lift when jumping and for something called wing-assisted incline running, which modern birds still use to get away from predators by speeding up steep inclines. So it wasn’t such a hopeful monster after all, just a series of gradual improvements that led to gliding, which eventually turned into full-fledged flight.

So that’s how dinosaurs started flying. Does it surprise you to learn that pterodactyls don’t have anything to do with it? Here’s something that might blow your mind even more: pterodactyls aren’t even dinosaurs. Leaving that tidbit aside, flight has actually evolved at least three separate times among vertebrates, and there are a few critters that already seem like they might be on their way up as well.

Pterosaurs

The OG fliers. For 140 million years, pterosaurs were pretty much unchallenged in the skies (though birds may have started turning up towards the end). Their wings took the form of a membrane stretched back from their “pinky finger” to their body, with the rest of their digits extending forward from the wing’s central joint. They likely walked on their knuckles, like a gorilla, and would have taken off from the ground instead of launching themselves from trees. Though the most famous pterosaur, pterodactyl, had a wingspan of only 3 feet, these things got huge — quetzelcoatlus was as tall as a giraffe.

Birds

We’ve covered them pretty well already, so we don’t need to go into too much detail. Unlike pterosaurs, birds have wings built around a fused hand, with relatively thick but hollow bones providing their structure. This likely allows birds a greater degree of maneuverability than pterosaurs would have enjoyed, since their wings aren’t restricted due to being attached to the body by a membrane.

Bats

At first glance, bat wings look similar to those of pterosaurs, with a membrane stretching from the tip back to their body (or even their toes). The main difference is that their hand is turned inward, with each finger extending through the membrane to give it more structure. They only started flying about 50 million years ago, meaning they are still the new kids on the aerial block. There are a few up-and-comers on their heels, however.

Gliders

There are a few vertebrates that can’t quite fly yet, but they can glide. Basically, that means that their wings can’t take them up, but they can fall slower and move while they do it. Flying squirrels are probably the most famous example, and not just because of their symbiotic relationship with mooses. But there are tons of others, and they’re not just mammals. We already told you about flying snakes, which slither their way through the air like it’s solid ground. There are also gliding frogs, which use their webbed feet as parachutes, and flying fish and flying rays represent the aquatic set. Who knows? In a couple million years, the skies might be full of flying animals from every kingdom.


How Do We Know, What Colors Dinosaurs Were? (Paleontology)

It’s just common sense that you can’t tell what color dinosaurs were, right? After all, it’s not like you’ll be able to see greens and oranges on fossilized bones (and even if you could, that would just tell you what color their bones were). Sure, there are also skin imprints that tell us if they were scaly, like Triceratops, or feathered, like Velociraptor, but those are just shapes in the mud. They aren’t enough to tell you what they really looked like.

But in 2010, a close examination of the feathers of Sinosauropteryx resulted in a surprising reveal. Discovered in 1996, Sinosauropteryx was the first dinosaur we found with feathers. When examined under a microscope, however, those feathers were found to have surviving melanosomes: the tiny, cellular organelles that generate melanin, and thus, pigment.

Even so, big deal, right? After all, we could have assumed that those dinos had melanosomes — it’s not as if we assumed they were colorless. But the whole reason they decided to look at Sinosauropteryx’s feathers in the first place was a discovery that made the color-producing process a lot less mysterious.

You’ll find melanosomes in pretty much every animal, but it wasn’t until 2008 that a team of researchers from Yale began looking for them in fossilized birds as well. They did so with an eye toward comparing them to modern birds, and what they found indicated the relationship between the physical shape of the melanosomes and the pigment that they would produce. One 40-million-year-old specimen, for example, was found to have iridescent qualities, since differently-shaped melanosomes were found arranged in a staggered pattern that would appear different depending on what angle they were viewed from.

Fig: An artistic interpretation of Sinosauropteryx in the likely open habitat in which it lived 130 million years ago in the early Cretaceous period.(Robert Nicholls)

So what color were dinosaurs? For now, we can’t answer that question for every dino, but when it comes to Sinosauropteryx, the picture is nearly complete. And very raccoon-like. These little beasts, which were only about a meter (three feet) long, had a robber mask around their eyes, dark, reddish coloration on their backs, a pale belly, and long striped tails.

In its own way, it’s not too surprising that a dinosaur would bear such a close resemblance to a living animal it has no relation to — color patterns evolve because they work, and because they work, they evolve more than once. So the next time you think of dinosaurs, picture your raptors with leopard prints, your duckbills with zebra stripes, or your ornithomimuses with bright blue peacock plumage.


Evolution Of Bird Skull Slowed Down After The Extinction Of The Dinosaurs (Paleontology)

The evolutionary radiation of birds has produced incredible morphological variation, including a huge range of skull form and function. It has been, often hypothesized to be the result of a sudden hastening of evolution following the mass extinction that killed their non-avian dinosaur cousins at the end of the Cretaceous 66 million years ago. But, this is not the case according to a new study. In the most detailed study yet of bird skull morphology, Felice and colleagues showed that the rate of evolution actually slowed in birds compared to non-avian dinosaurs.

The researchers used high-dimensional 3-D geometric morphometrics to map the shape of 354 living and 37 extinct avian and non-avian dinosaurs in unprecedented detail and performed phylogenetic analyses to test for a shift in the pace of evolution after the origin of birds. They found that all regions of the skull evolved more rapidly in non-avian dinosaurs than in birds, but certain regions showed rapid pulses of evolution in particular lineages.

Fig. Phenotypic difference between each specimen for each landmark in the 11-module dataset and the mean skull shape. For each specimen, the mean landmark configuration is plotted with points coloured relative to the Procrustes distance between the position of that point in the mean shape and in that specimen. Warmer colours denote landmarks having higher displacement from the mean, and cooler colours are more similar to the mean shape.

For example, in non-avian dinosaurs, rapid evolutionary changes in the jaw joint were associated with changes in diet, while accelerated evolution of the roof of the skull occurred in lineages that sported bony ornaments such as horns or crests. In birds, the most rapidly evolving part of the skull was the beak, which the authors attribute to adaptation to different food sources and feeding strategies.

The authors say that overall slower pace of evolution in birds compared to non-avian dinosaurs calls into question a long-standing hypothesis that the diversity seen in modern birds resulted from rapid evolution as part of an adaptive radiation following the end-Cretaceous extinction event.


References: Felice RN, Watanabe A, Cuff AR, Hanson M, Bhullar B-AS, Rayfield ER, et al. (2020) Decelerated dinosaur skull evolution with the origin of birds. PLoS Biol 18(8): e3000801. doi.org/10.1371/journal.pbio.3000801 link: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3000801

Silurian Trilobite Had Modern Type of Compound Eye (Paleontology)

Paleontologists have found, Aulacopleura koninckii, a species of trilobite that lived around 429 million years ago i.e. during Silurian period, was equipped with a fully modern type of visual system — “compound eye”— comparable to that of living bees, dragonflies and others.

Fig: Left eye of Aulacopleura koninckii. Image credit: Choenemann & Clarkson, doi: 10.1038/s41598-020-69219-0.

Trilobites are extinct marine arthropods that used to live during Paleozoic era (542-251 million years ago).

From the very beginning of their appearance they were equipped with compound eyes, which during the Cambrian explosion and later differentiated into highly diverse visual systems.

The most basic type, and still very common among diurnal insects and crustaceans, is the apposition compound eye.

It consists of up to 30,000 individual, more or less identical receptor units, so-called ommatidia, optically isolated from each other by a set of screening pigment cells.

In a new study, University of Cologne’s Dr. Brigitte Schoenemann and Dr. Euan Clarkson from the University of Edinburgh used digital microscopy to examine apposition compound eyes of a small trilobite called Aulacopleura koninckii.

This extinct species was first described in 1846 by the French-Czech paleontologist Joachim Barrande, a pioneer of trilobite research, from specimens collected at several paleontological sites near Loděnice in the Czech Republic.

Fig: The 429-million-year-old specimen of Aulacopleura koninckii investigated by Choenemann & Clarkson. Scale bar – 2.5 mm. Image credit: Choenemann & Clarkson, doi: 10.1038/s41598-020-69219-0.

The excellently-preserved specimen studied by the study authors is 1-2 mm high and has two protruding semi-oval eyes on the back of its head, one of which has broken off.

They identified a number of internal structures that are similar to those of the compound eyes of many modern insects and crustaceans, including their ommatidia (measuring 35 μm in diameter) that contain eight light-detecting cells grouped around a transparent tube called a rhabdom.

Each visual unit is topped with a thick lens and the remains of what the paleontologists suggest is a flat crystalline cone that light passed through before being focused onto the rhabdom.

The small size of its visual units indicates that Aulacopleura koninckii lived in bright, shallow waters and was probably active during the day, as smaller diameter lenses are efficient at capturing light under bright conditions.

The presence of pigment cell barriers between visual units suggests that the trilobite had mosaic vision with each visual unit contributing a small portion of the overall image, similar to the compound eyes of many modern insects and crustaceans.

The researchers also think that Aulacopleura koninckii likely was a translucent trilobite, comparable to modern shrimps and other smaller aquatic crustaceans with translucent shells, providing an excellent camouflage in water.


References: B. Choenemann & E.N.K. Clarkson. 2020. Insights into a 429-million-year-old compound eye. Sci Rep 10, 12029; doi: 10.1038/s41598-020-69219-0 ; link: https://www.nature.com/articles/s41598-020-69219-0

Antarctica Was Once Covered In Forests And We Have The Fossils To Prove it (Paleontology / Botany)

As far as vacation destinations go, Antarctica isn’t much. Most of its surface is covered by a layer of ice a mile thick, and it experiences the lowest temperatures ever recorded on Earth. But millions of years ago, it was a tropical paradise — compared to now, at least. At that point, it was covered not by ice, but by trees, and scientists are uncovering the fossil evidence of those long-dead forests today.

600 million years ago, you wouldn’t have recognized our planet. Instead of seven continents, all of the dry land existed in one supercontinent we now call Pangaea. The climate was different too, with higher temperatures and sultry humidity. Over hundreds of millions of years, the southern part of the supercontinent, called Gondwana, began to break away from the northernmost Laurasia until it sat near where Antarctica is today.

Those higher temperatures meant that plants could live, if not thrive — the continent was still on the South Pole, so vegetation had to withstand four to five months of darkness followed by four to five months where the sun never set. That meant that while modern plants take months to transition from season to season, plants on Gondwana had to transition in as little as a month if they were going to survive the rapid change in light and temperature.

Fig: Erik Gulbranson, palaeoecologist and assistant professor at University of Wisconsin-Milwaukee, studies some of the fossilized tree he brought from Antarctica

The kings of the Gondwanan forest during the Permian Period were towering trees belonging to the Glosspteris genus. They grew from 65 to 131 feet (20 to 30 meters) tall and had huge, flat leaves longer than your forearm. But around 251 million years ago, disaster struck. The Permian-Triassic mass extinction killed off as much as 95 percent of Earth’s species. Scientists still aren’t sure what caused it, but many think that greenhouse gas emissions from volcanoes raised the planet’s temperatures to hazardous levels and caused the oceans to acidify.

In reaction, the forests of Gondwana quickly fossilized. “The fungi in the wood itself were probably mineralized and turned into stone within a matter of weeks, in some cases probably while the tree was still alive,” researcher Erik Gulbranson told National Geographic. “These things happened incredibly rapidly. You could have witnessed it firsthand if you were there.”

That’s bad news for Permian forests, but great news for us. Today, we have fossilized wood fragments and even tree trunks from the forests that once covered our coldest continent. Who needs to imagine exotic environments on other planets? We had them right here all along.


New Species of Ancient Giant Alligator Identified (Paleontology)

A new species of crocodilian related to modern alligators has been identified from fossils found in Mississippi and Alabama, the United States. Named Deinosuchus schwimmeri, it lived between 75 and 82 million years ago (Cretaceous period) and had teeth the ‘size of bananas,’ capable to take down even the very largest of dinosaurs.

Fig: An illustration of Deinosuchus. Image credit: Tyler Stone, tylerstoneart.wordpress.com.

Deinosuchus is a genus of giant (over 10 m, or 33 feet, in length) crocodylians from the Late Cretaceous of North America.

These creatures were the largest semiaquatic predators in their environments, longer and heavier than their predatory competitors, and are known to have fed on large vertebrates, including contemporaneous dinosaurs.

Two Deinosuchus species, Deinosuchus hatcheri and Deinosuchus riograndensis, lived in the west of America, ranging from Montana to northern Mexico.

The newly-described species, Deinosuchus schwimmeri, lived along the Atlantic coastal plain from New Jersey to Mississippi.

Fig: Deinosuchus schwimmeri skull: (A) dorsal view, (B) ventral view, (C) lateral view of braincase elements, (D) lateral view of otic region elements, (E) posterior view of skull. Abbreviations: bo – basioccipital, CNV – cranial nerve V, eao – external auditory opening, ect – ectopterygoid, eo – exoccipital, f – frontal, itf – infratemporal fenestra, j – jugal, l – lacrimal, ls – laterosphenoid, mx – maxilla, n – nasal, og – ophthalmic groove, orb – orbit, pa – parietal, pal – palatine, pas – paranasal air sinus, pf – prefrontal, po – postorbital, pot – prootic, pt – pterygoid, ptf – posttemporal fenestra, q – quadrate, qj – quadratojugal, so – supraoccipital, sq – squamosal, stf – supratemporal fenestra. Scale bar – 5 cm. Image credit: Cossette & Brochu, doi: 10.1080/02724634.2020.1767638.

Dr. Cossette and his colleague, University of Iowa’s Professor Christopher Brochu, studied new and previously found material to review species-level systematics of Deinosuchus and help refine its phylogenetic placement among crocodilians.

Based on its enormous skull, Deinosuchus looked like neither an alligator nor a crocodile.

Its snout was long and broad, but inflated at the front around the nose in a way not seen in any other crocodylian, living or extinct. The reason for such enlarged nose is unknown.


References: (1) Adam P. Cossette & Christopher A. Brochu. A systematic review of the giant alligatoroid Deinosuchus from the Campanian of North America and its implications for the relationships at the root of Crocodylia. Journal of Vertebrate Paleontology, published online July 29, 2020; doi: 10.1080/02724634.2020.1767638 (2) https://www.amnh.org/exhibitions/crocs/ancient-crocs (3) http://documents.irevues.inist.fr/handle/2042/28152