Recent excavations in Asia unearthed a pristine, three-dimensional fossil of a tiny dinosaur tail with preserved feathers and soft tissues (presumably skin). In 2016, investigators in northern Myanmar (Burma) recovered a piece of Cretaceous-era amber (Fig. 1) containing an approximately 99-million-year-old feathered tail from a theropod dinosaur. (Theropods are carnivorous bipedal saurischian reptiles that first appeared in the Upper Triassic and culminated in the uppermost Cretaceous.) Although the size of the tail measures only 37 mm (1.46 in.), eight vertebrae can be identified, and the morphological structure of the plumage is clearly observable. See also: Amber; Cretaceous; Dinosauria; Fossil; Saurischia

Mucus produced by the common garden snail (Helix aspersa) is green. The slime is not actually green in color but is “green” in terms of its environmentally friendly chemistry. It turns out that this snail’s mucus has chemical properties as a reducing agent for producing gold nanoparticles that promote wound healing and for use in other biomedical applications, according to researchers reporting in the journal Soft Matter (November 2020). The idea of using snail slime in medicine is not that farfetched, as snail slime was used by ancient Greeks to treat skin inflammation, and snail slime protein is currently used in cosmetics—although with the snootier name of “snail secretion filtrate hydrates”—for its skin-hydrating properties and to treat acne. See also: Gastropoda; Gold; Green chemistry; Inflammation; Nanoparticle; Skin; Skin disorders

Macular degeneration is the most prevalent cause of vision impairment and loss among people aged 55 years and older. Also termed age-related macular degeneration (AMD), this serious eye condition damages the macula, which is the most sensitive part of the retina of the eye. Located near the center of the retina, the macula consists of millions of light-sensing cells that provide sharp, central vision, enabling objects that are straight ahead of the eye to be seen. Normally, photoreceptors in the retina convert light entering the eye into electrical signals that are sent through the optic nerve to the brain, which interprets them as visual images. However, when the macula deteriorates and undergoes atrophy, the center of a person's field of view appears distorted, blurry, or dark, which hampers or eliminates fine vision, including the detailed vision necessary for such important activities as reading a book, threading a needle, and recognizing faces. See also: Brain; Color vision; Eye (vertebrate); Eye disorders; Light; Perception; Photoreception; Vision; Visual impairment

In many animals, including humans, the sense of smell performs an important threat-detection function by helping to identify potential sources of harm, such as rotting food and toxic fumes. Little is known, however, about the initial neural mechanisms of the olfactory system when, in concert with other brain regions, one judges a scent to represent danger. Such a judgment triggers a physical avoidance response, familiar to us as the recoiling we experience upon sniffing moldy vegetables or other malodorous substances. A new study has now shed light on this process. The study has demonstrated that reactions to malodors are involuntary and rapid, rather than being a conscious, cognitive process as had long been presumed. The findings also show that the processing of unpleasant smells is prioritized over the processing of pleasant, non-threatening smells. Broadly speaking, these results offer insights into avoidance responses in animals related to the perception of chemicals in a local environment. See also: Brain; Consciousness; Olfaction

Molting (shedding or ecdysis) of the outer cuticular layer of the body is a process vital to arthropods, including insects and crustaceans. This profound endocrinological and physiological process has undoubtedly helped ensure the evolutionary success of the Arthropoda, which comprise the largest phylum in the animal kingdom. See also: Arthropoda; Crustacea; Insecta

Over thousands of years of study of the human body through dissection and, more recently, modern-day imaging techniques, scientists have observed and analyzed various glands—that is, structures or organs that produce and secrete a substance or substances essential for proper physiological functioning. Remarkably, a previously unknown pair of salivary glands—termed tubarial salivary glands—has been discovered in the human nasopharynx region. This region is the space between the posterior nasal openings, above a horizontal plane through the lower margin of the palate. Physicians made the discovery during routine positron emission tomography (PET) and computed tomography (CT) scans with prostate-specific membrane antigen (PSMA) ligands performed on a male patient with prostate cancer. Subsequent imaging studies carried out on another 99 male patients, 1 female patient, and 2 cadavers (1 male and 1 female) confirmed the presence of tubarial glands. Thus, tubarial glands are considered to be a newly identified anatomical component of the salivary gland system in humans. See also: Computerized tomography; Gland; Ligand; Medical imaging; Pharynx

Obesity is an excessive accumulation of body fat that confers a variety of health risks, including diabetes, cardiovascular disorders, arthritis, and some types of cancerous tumors. The risk to health is determined by the amount of body fat, the distribution of body fat, and the presence of other risk factors. Obesity has long been considered to be a public health problem, but a significant step was taken when the American Medical Association, the largest physician organization in the United States, officially classified obesity as a disease that requires a range of medical interventions to advance treatment and prevention. In particular, because more than one-third of adults and approximately one-fifth of children in the United States are recognized as obese, the designation of obesity as a disease is expected to prompt the medical community and public policy makers to support further interventions and research into obesity prevention and treatment. See also: Diabetes; Disease; Epidemic of obesity; Obesity; Public health

Humans' contributions to global warming through burning fossil fuels and other actions (for example, detrimental land-use practices) have resulted in sharp increases in the levels of atmospheric carbon dioxide (CO₂). These rising levels of CO₂ also affect the world's oceans. When CO₂ from the atmosphere is absorbed by and dissolved in seawater, it acidifies the water by forming carbonic acid. This process then decreases the pH of the water, potentially endangering numerous marine ecosystems. Now, a study investigating the effects of elevated CO₂ levels on the olfaction of the European bass (Dicentrarchus labrax, order Perciformes) has indicated a dramatic result—namely, the loss of the fish's sense of smell. Researchers are troubled by this outcome and are fearful that the survival of many marine fish species may be at risk because of compromised olfactory mechanisms. See also: Basses; Biogeochemistry; Carbon dioxide; Ecosystem; Global climate change; Global warming; Marine ecology; Ocean acidification; Olfaction; Perciformes; pH; Seawater

Osteoprotegerin (OPG) is a protein that plays a central role in the regulation of bone mass. Also known as osteoclastogenesis inhibitory factor (OCIF), this naturally occurring protein [a soluble decoy receptor protein that belongs to the tumor necrosis factor (TNF) receptor superfamily] inhibits both the formation of osteoclasts (bone-resorbing cells) and the activity of these cells when they are mature. Because of this dual function, osteoprotegerin is believed to have great potential as a therapeutic agent for a number of bone and joint disorders, including rheumatoid arthritis, cancer-induced bone diseases, and osteoporosis (a metabolic condition in which decreases in bone mass and reductions in the amount of bone tissue increase the likelihood of fracture). In particular, because osteoprotegerin is able to block the development of osteoclasts, the administration of this protein is seen as a possible means to halt age-associated bone resorption and loss, to protect bone strength, and to decrease the chance of bone fracture. See also: Arthritis; Bone; Bone disorders; Cancer; Connective tissue; Joint disorders; Oncology; Osteoporosis; Protein

The prominent, spiraling tusk that emerges from the head of the unusual whales called narwhals may serve a variety of uses for these animals, including acting as a water-salinity detector, according to recent studies.