It's possible to run out of adjectives for describing the platypus. This unique semi-aquatic creature, endemic to Australia, has confounded scientists since its discovery. And while its quirks have helped the platypus rise to global fame, there is still a great deal we don't know about this enigmatic animal.

Here are a few interesting things we do know about the platypus, however. Some make sense and others, frankly, just lead to more questions.

1. People Originally Thought the Platypus Was a Fake Animal

An illustration of the platypus from 'The Naturalist's Miscellany.'. The Naturalist's Miscellany/Wikimedia Commons/CC0 1.0

When the platypus was first described in 1799 in the "Naturalist's Miscellany" by the naturalist George Shaw, he wrote, "So accurate is the similitude that, at first view, it naturally excites the idea of some deceptive preparation by artificial means." Indeed, the platypus's unique appearance — a duck's bill and feet, an otter's body and fur, and a beaver's tail — all but screams hoax. Even though Shaw doubted its authenticity, he still dubbed the creature the "duck-billed platypus" and provided it with a Latin name, Platypus anatinus, or "flatfoot duck." The critter's scientific name is now Ornithorhynchus anatinus, and it is the only living representative of its family and genus.

2. Platypuses Are Venomous Mammals

Very few mammals are venomous. A male platypus delivers venom through ankle spurs (females aren't venomous). The venom is composed of defensin-like proteins, or DLPs, three of which are only found in the platypus, which ups the animal's oddness factor. The venom can severely hurt (but not kill) humans, although it can be lethal to smaller animals. Scientists think the venom, which increases in production during mating periods, is intended to incapacitate rival males. Speaking of reproduction ...

3. Platypuses Are Egg-Laying Mammals

Along with echidnas, the platypus belongs to a small group of egg-laying mammals called monotremes. Eric Chan/Flickr/CC BY 2.0

The platypus isn't the only venomous mammal, and also isn't the only egg-laying mammal (the four species of echidna lay eggs, too), but the trait is unusual. Not much is known about the life cycle of a platypus. Males play no part in rearing the offspring following mating. The female gestates the eggs for two to four weeks followed by another week of incubation, in which the female circles around them bill to tail. Once they hatch, the young suck milk from special mammary hairs for a few months before they become independent.

4. They're at Risk of Extinction

The platypus is listed as near threatened on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Extreme, prolonged drought conditions in Australia have dried up the waterways that make up the platypus's habitat, according to a 2020 study in Biological Conservation. The animals are also threatened by habitat loss due to land clearing and climate change. Recent bushfires have also taken a toll on the species. "There is an urgent need to implement national conservation efforts for this unique mammal by increasing surveys, tracking trends, mitigating threats and improving management of platypus habitat in rivers," the researchers write.

5. Platypus Milk Could Combat Superbugs

The platypus is a bottom feeder, scooping up worms, insects, shellfish, and other prey. John Carnemolla/Shutterstock

Since platypuses don't have a sterile way to deliver milk, they need additional protections against bacteria in the environment. In 2010, scientists discovered that platypuses' milk contained antibacterial properties that could help in the fight against antibiotic resistance. A study published in the journal Structural Biology Communications determined the protein has a ringlet-like structure, so researchers named it the Shirley Temple protein, after the child actor known for her curly locks. This structure is unique, and it could indicate a unique therapeutic function as well.

6. Platypuses Have 10 Sex Chromosomes

Mammals typically have just a single pair of chromosomes that determine sex, but platypuses have five pairs. Odder still is that some of those Y chromosomes share genes with sex chromosomes found in birds. Yes, birds. It's possible that mammal sex chromosomes and bird sex chromosomes evolved at the same time, and the platypus could be the key to figuring it out.

7. Platypuses Don't Have Stomachs

Platypuses nosh on bottom-dwelling invertebrates — worms, insect larvae, shrimp — but that food goes directly to their intestines from their gullets. They don't have a sac of digestive enzymes or acids to break it down. A study published in Genome Biology outlined how several different genes related to digestion and the stomach were deleted or deactivated in the critter. One possible reason for this is that those bottom-dwelling dishes can be high in calcium carbonate, a substance that neutralizes stomach acid. No need for the acid if you're canceling it out all the time.

8. Platypuses Don't Have Teeth, Either

The platypus doesn't have any teeth inside its interesting mouth. Mari_May/Shutterstock

First no stomachs and now no teeth. How do they even eat? When platypuses go diving for food, they also scoop grit and gravel from the seabed. With all of this in their mouths, they surface for air and begin to "chew" by grinding the gravel and their prey together.

9. Platypuses 'See' With Their Bills Underwater

When they dive underwater, platypuses are basically sightless and unable to smell anything. Folds of skin cover their eyes, and their nostrils seal up to become watertight. Their bills, however, have electroreceptors and mechanoreceptors that allow them to detect electrical fields and movement, respectively. But since their mechanoreceptors will be attuned to any movement, electroreceptors are necessary to detect living organisms for eating after they dig through the sea bed.