Skull of Smallest Known Dinosaur Found in 99-Million-Year Old Amber
In 2016, our colleague Xing Lida held up a small piece of polished, deeply yellow amber. As sunlight shone through the ancient resin, Lida saw the outline of a pristinely preserved, amazingly small skull. There was a prominent eye socket, a dome-shaped crown of the head, a long, tapering snout and even small teeth. It was bird-like, but in a strange and ancient way.
The amber contains the skull of Oculudentavis khaungraae, a newly described dinosaur and one of the smallest ever discovered. Its tiny stature is forcing paleontologists to rethink the lower limits of body size in birds, and the nearly 100-million-year-old fossil is challenging the current understanding of when and how dinosaur giants shrank into the birds of today.
A Mysterious Transformation
Tiny Oculudentavis may have occupied a unique ecological niche in the ancient world. Han Zhixin / CC BY-ND
The evolutionary transition of dinosaurs to modern birds is one of the most astounding transformations in the history of life: large, bipedal and mostly carnivorous dinosaurs morphed into small, flying birds. Famous discoveries like Archaeopteryx and more recently the fossils from the Jehol Biota in China have given researchers some hints about the process. But finds from this evolutionary phase — which researchers think began about 200 million years ago — are rare.
Paleontologists are far from having a complete picture of the evolution of birds, and even farther from a full inventory of Earth's ecosystems in the age of dinosaurs. Our research on the tiny Oculudentavis, published in the journal Nature, adds valuable information to the puzzle of when, how and to what extent dinosaurs shrank.
Clues in Bone
This high-resolution scan allowed us to see the intricacies of a bone structure unlike any before seen in birds or dinosaurs. Xing Lida / CC BY-ND
Our team needed to see the minute details of the skull, and we needed to do it without cracking or ruining the specimen - a difficult task with a skull encased in 99-million-year old amber from Myanmar. To do that, we scanned the skull with high-resolution X-rays and created a digital model with very fine anatomical detail. What emerged was a picture of an overall bird-like anatomy. But in some interesting ways, Oculudentavis is unlike any bird or dinosaur that has ever been found.
The obvious curiosity of the fossil is its size: Oculudentavis rivaled the smallest bird living today, the bee hummingbird, and likely was no more than 1.6 inches (4 centimeters) from beak to tail. We considered whether the skull possibly belonged to a very young animal, but the extent and pattern of bone growth and the proportional size of the eye pointed to a mature bird.
With a total skull length of just about 0.6 inches (1.5 centimeters), Oculudentavis pushes against what is considered the lower limit of size in birds: the head still had to hold functional eyes, a brain and jaws. The small size is especially surprising if one considers that Oculudentavis lived during the same time as giant plant-eating dinosaurs like Argentinosaurus.
Small and Specialized
The small size of Oculudentavis is striking, but to a trained eye there are other extremely unusual features, too.
First of all, the skull seems to be built for strength. The bones show an unusual pattern of fusion and the skull lacks an antorbital fenestra, a small hole often found in front of the eye.
The eyes of Oculudentavis also surprised us. The shape of the bones found within the eye, the scleral ossicles, suggests that it probably had conical eyes with small pupils. This type of eye structure is especially well adapted for moving around in bright light. While daytime activity might be expected for an ancient bird from the age of dinosaurs, the shape of the ossicles is entirely distinct from any other dinosaur and resembles those of modern-day lizards.
Adding to the list of unexpected features, the upper jaw carries at least 23 small teeth. These teeth extend all the way back beneath the eye and are not set in deep pockets, an unusual arrangement for most ancient birds. The large number of teeth and their sharp cutting edges suggest that Oculudentavis was a predator that may have fed on small bugs.
The sum of these traits — a strong skull, good eyesight and a hunter's set of teeth — suggests to us that Oculudentavis led a life previously unknown among ancient birds: it was a hummingbird-sized daytime predator.
One of the Earliest and Tiniest Birds?
Placing Oculudentavis in the tree of life is, given its strange anatomy, challenging. Our phylogenetic analysis — the investigation of its relationships to other dinosaurs — identifies Oculudentavis as one of the most ancient birds. Only Archaeopteryx branched off earlier.
Scientists consider the nectar-feeding hummingbirds — which appeared 30 million years ago — the smallest dinosaurs on record. But if our placement of Oculudentavis holds true, the miniaturization of dinosaurs may have peaked far earlier than paleontologists previously thought. In fact, the largest and the smallest dinosaurs may have walked and flown the same earth nearly 100 million years ago.
Our work demonstrates how little scientists know about the little things in the history of life. Scientists' snapshot of fossil ecosystems in the dinosaur age is incomplete and leaves so many questions unanswered. But paleontologists are eager to take on these questions. What other tiny species were out there? What was their ecological function? Was Oculudentavis the only visually guided bug hunter? To better understand the evolution of the diversity of life we need more emphasis and recognition of the small.
Amber holds strong potential to fill that gap. Maybe one day a scientist will hold up another piece, and let sunshine reveal a complete Oculudentavis, or even a previously unknown species. More finds in amber will help illuminate the world of the tiny vertebrates in the age of dinosaurs.
Reposted with permission from The Conversation.
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EcoWatch Daily Newsletter
By Jake Johnson
In a move that environmentalists warned could further imperil hundreds of endangered species and a protected habitat for the sake of profit, President Donald Trump on Friday signed a proclamation rolling back an Obama-era order and opening nearly 5,000 square miles off the coast of New England to commercial fishing.
Why You Should Wash Fresh Produce<p>Global pandemic or not, properly washing fresh fruits and vegetables is a good habit to practice to minimize the ingestion of potentially harmful residues and germs.</p><p>Fresh produce is handled by numerous people before you purchase it from the grocery store or the farmers market. It's best to assume that not every hand that has touched fresh produce has been clean.</p><p>With all of the people constantly bustling through these environments, it's also safe to assume that much of the <a href="https://www.healthline.com/nutrition/fresh-vs-frozen-fruit-and-vegetables" target="_blank">fresh produce</a> you purchase has been coughed on, sneezed on, and breathed on as well.</p><p>Adequately washing fresh fruits and vegetables before you eat them can significantly reduce residues that may be left on them during their journey to your kitchen.</p><p><strong>Summary</strong></p><p><strong></strong>Washing fresh fruits and vegetables is a proven way to remove germs and unwanted residues from their surfaces before eating them.</p>
Best Produce Cleaning Methods<p>While rinsing fresh produce with water has long been the traditional method of preparing fruits and veggies before consumption, the current pandemic has many people wondering whether that's enough to really clean them.</p><p>Some people have advocated the use of soap, <a href="https://www.healthline.com/nutrition/white-vinegar" target="_blank">vinegar</a>, lemon juice, or even commercial cleaners like bleach as an added measure.</p><p>However, health and food safety experts, including the Food and Drug Administration (FDA) and Centers for Disease Control (CDC), strongly urge consumers not to take this advice and stick with plain water.</p><p>Using such substances may pose further health dangers, and they're unnecessary to remove the most harmful residues from produce. <a href="https://www.healthline.com/health/chlorine-poisoning" target="_blank">Ingesting commercial cleaning chemicals</a> like bleach can be lethal and should never be used to clean food.</p><p>Furthermore, substances like lemon juice, vinegar, and produce washes have not been shown to be any more effective at cleaning produce than plain water — and may even leave additional deposits on food.</p><p>While some research has suggested that using neutral electrolyzed water or a baking soda bath can be even more effective at removing certain substances, the consensus continues to be that cool tap water is sufficient in most cases.</p><p><strong>Summary</strong></p><p><strong></strong>The best way to wash fresh produce before eating it is with cool water. Using other substances is largely unnecessary. Plus they're often not as effective as water and gentle friction. Commercial cleaners should never be used on food.</p>
How to Wash Fruits and Vegetables With Water<p>Washing fresh fruits and vegetables in cool water before eating them is a good practice when it comes to health hygiene and food safety.</p><p>Note that fresh produce should not be washed until right before you're ready to eat it. Washing fruits and vegetables before storing them may create an environment in which bacterial growth is more likely.</p><p>Before you begin washing fresh produce, <a href="https://www.healthline.com/health/how-long-should-you-wash-your-hands" target="_blank">wash your hands well</a> with soap and water. Be sure that any utensils, sinks, and surfaces you're using to prepare your produce are also thoroughly cleaned first.</p><p>Begin by cutting away any bruised or visibly rotten areas of fresh produce. If you're handling a fruit or vegetable that'll be peeled, such as an orange, wash it before peeling it to prevent any surface bacteria from entering the flesh.</p><p>The general methods to wash produce are as follows:</p><ul><li><strong>Firm produce.</strong> Fruits with firmer skins like apples, lemons, and pears, as well as <a href="https://www.healthline.com/nutrition/root-vegetables" target="_blank">root vegetables</a> like potatoes, carrots, and turnips, can benefit from being brushed with a clean, soft bristle to better remove residues from their pores.</li><li><strong>Leafy greens.</strong> Spinach, lettuce, Swiss chard, leeks, and cruciferous vegetables like Brussels sprouts and bok choy should have their outermost layer removed, then be submerged in a bowl of cool water, swished, drained, and rinsed with fresh water.</li><li><strong>Delicate produce.</strong> Berries, mushrooms, and other types of produce that are more likely to fall apart can be cleaned with a steady stream of water and gentle friction using your fingers to remove grit.</li></ul><p>Once you have thoroughly rinsed your produce, dry it using a clean paper or cloth towel. More fragile produce can be laid out on the towel and gently patted or rolled around to dry them without damaging them.</p><p>Before consuming your fruits and veggies, follow the simple steps above to minimize the amount of germs and substances that may be on them.</p><p><strong>Summary</strong></p><p><strong></strong>Most fresh fruits and veggies can gently be scrubbed under cold running water (using a clean soft brush for those with firmer skins) and then dried. It can help to soak, drain, and rinse produce that has more dirt-trapping layers.</p>
The Bottom Line<p>Practicing good food hygiene is an important health habit. Washing fresh produce helps minimize surface germs and residues that could make you sick.</p><p>Recent fears during the <a href="https://www.healthline.com/coronavirus" target="_blank">COVID-19 pandemic</a> have caused many people to wonder whether more aggressive washing methods, such as using soap or commercial cleaners on fresh produce, are better.</p><p>Health professionals agree that this isn't recommended or necessary — and could even be dangerous. Most fruits and vegetables can be sufficiently cleaned with cool water and light friction right before eating them.</p><p>Produce that has more layers and surface area can be more thoroughly washed by swishing it in a bowl of cool water to remove dirt particles.</p><p>Fresh fruits and vegetables offer a number of healthy nutrients and should continue to be eaten, as long as safe cleaning methods are practiced.</p>
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By Jacob L. Steenwyk and Antonis Rokas
From the mythical minotaur to the mule, creatures created from merging two or more distinct organisms – hybrids – have played defining roles in human history and culture. However, not all hybrids are as fantastic as the minotaur or as dependable as the mule; in fact, some of them cause human diseases.
When Looking Through a Microscope Isn’t Close Enough.<p>For the last few years, <a href="http://www.rokaslab.org/" target="_blank">our team at Vanderbilt University</a>, <a href="https://www.researchgate.net/lab/Gustavo-Goldman-Lab" target="_blank">Gustavo Goldman's team at São Paulo University in Brazil</a> and many other collaborators around the world have been collecting samples of fungi from patients infected with different species of <em>Aspergillus</em> molds. One of the species we are particularly interested in is <a href="https://doi.org/10.1006/rwgn.2001.0082" target="_blank"><em>Aspergillus nidulans</em>, a relatively common and generally harmless fungus</a>. Clinical laboratories typically identify the species of <em>Aspergillus</em> causing the infection by examining cultures of the fungi under the microscope. The problem with this approach is that very closely related species of <em>Aspergillus</em> tend to look very similar in their broad morphology or physical appearance when viewing them through a microscope.</p><p>Interested in examining the varying abilities of different <em>A. nidulans</em> strains to cause disease, we decided to analyze their total genetic content, or genomes. What we saw came as a total surprise. We had not collected <em>A. nidulans</em> but <em>Aspergillus latus</em>, a close relative of <em>A. nidulans</em> and, as we were to soon find out, <a href="https://doi.org/10.1016/j.cub.2020.04.071" target="_blank">a hybrid species that evolved through the fusion of the genomes</a> of two other <em>Aspergillus</em> species: <em>Aspergillus spinulosporus</em> and an unknown close relative of <em>Aspergillus quadrilineatus</em>. Thus, we realized not only that these patients harbored infections from an entirely different species than we thought they were, but also that this species was the first ever <em>Aspergillus</em> hybrid known to cause human infections.</p>
Several Different Fungal Hybrids Cause Human Disease.<p>Hybrid fungi that can cause infections in humans are well known to occur in several different lineages of single-celled fungi known as yeasts. Notable examples include multiple different species of <a href="https://doi.org/10.1002/yea.3242" target="_blank">yeast hybrids</a> that cause the human diseases <a href="https://rarediseases.info.nih.gov/diseases/6218/cryptococcosis" target="_blank">cryptococcosis</a> and <a href="https://www.cdc.gov/fungal/diseases/candidiasis/index.html" target="_blank">candidiasis</a>. Although pathogenic yeast hybrids are well known, our discovery that the <em>A. latus</em> pathogen is a hybrid is a first for molds that cause disease in humans.</p>
(Left) Candida yeasts live on parts of the human body. Imbalance of microbes on the body can allow these yeasts, some of which are hybrids, to grow and cause infection. (Right) Cryptococcus yeasts, including ones that are hybrids, can cause life-threatening infections in primarily immunocompromised people. Centers for Disease Control and Prevention<p><a href="https://doi.org/10.1371/journal.ppat.1008315" target="_blank">Why certain <em>Aspergillus</em> species are so deadly</a> while others are harmless remains unknown. This may in part be because <a href="https://doi.org/10.1016/j.fbr.2007.02.007" target="_blank">combinations of traits, rather than individual traits</a>, underlie organisms' ability to cause disease. So why then are hybrids frequently associated with human disease? Hybrids inherit genetic material from both parents, which may result in new combinations of traits. This may make them more similar to one parent in some of their characteristics, reflect both parents in others or may differ from both in the rest. It is precisely this mix and match of traits that hybrids have inherited from their parental species that <a href="https://www.nytimes.com/2010/09/14/science/14creatures.html" target="_blank">facilitates their evolutionary success</a>, including their ability to cause disease.</p>
The Evolutionary Origin of an Aspergillus Hybrid.<p>Multiple evolutionary paths can lead to the emergence of hybrids. One path is through mating, just as the horse and donkey mate to create a mule. Another path is through the merging or fusion of genetic material from cells of different species.</p><p>It is this second path that appears to have been taken by our fungus. <em>A. latus</em> appears to have two of almost everything compared to its parental species: twice the genome size, twice the total number of genes and so on. But unlike other hybrids, which are often sterile like the mule, we found that <em>A. latus</em> is capable of reproducing both asexually and sexually.</p><p>But how distinct were the parents of <em>A. latus</em>? By comparing the parts contributed by each parent in the <em>A. latus</em> genome, we estimate that its parents are approximately 93% genetically similar, which is about as related as we humans are with lemurs. In other words, <em>A. latus</em>, an agent of infectious disease, is the fungal equivalent of a human-lemur hybrid.</p>
How A. Latus Differs From its Parents.<p>Elucidating the identity of closely related fungal pathogens and how they differ from each other in infection-relevant characteristics is a key step toward reducing the burden of fungal disease. For example, we found that <em>A. latus</em> was three times more resistant than <em>A. nidulans</em>, the species it was originally identified as using microscopy-based methods, to one of the most common antifungal drugs, <a href="https://www.drugbank.ca/drugs/DB00520" target="_blank">caspofungin</a>. This result provides a clear example of the potential importance of accurate identification of the <em>Aspergillus</em> pathogen causing an infection.</p><p>We also examined how <em>A. latus</em> and <em>A. nidulans</em> interact with cells from our immune system. We found that immune cells were less efficient at combating <em>A. latus</em> compared to <em>A. nidulans</em>, suggesting the hybrid fungus may be trickier for our immune systems to identify and destroy.</p><p>In the midst of the COVID-19 pandemic, our quest to understand <em>Aspergillus</em> pathogens is becoming more urgent. Growing evidence suggests that <a href="https://doi.org/10.1111/myc.13096" target="_blank">a fraction of COVID-19 patients are also infected with <em>Aspergillus</em>.</a> More worrying is that these <a href="https://doi.org/10.3201/eid2607.201603" target="_blank">secondary <em>Aspergillus</em> infections</a> can worsen the clinical outcomes for those infected with the novel coronavirus. That being said, we stress that little is known about <em>Aspergillus</em> infections in COVID-19 patients due to a lack of systematic testing, and none of the infections identified so far appear to have been caused by hybrids.</p><p>So, when it comes to hybrids, some are fantastic (the minotaur), some are helpful (the mule) and some are dangerous (<em>Aspergillus latus</em>). Understanding more about the biology of <em>Aspergillus latus</em> may help in our understanding of how microbial pathogens arise and how to best prevent and combat their infections.</p>
This Saturday, June 6, marks National Trails Day, an annual celebration of the remarkable recreational, scenic and hiking trails that crisscross parks nationwide. The event, which started in 1993, honors the National Trail System and calls for volunteers to help with trail maintenance in parks across the country.
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