It's possible to run out of adjectives when it comes to describing the platypus. This unique creature, endemic to Australia, has confounded scientists since its discovery. We still don't know a great deal about the semi-aquatic animal, or the secrets that it holds.

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

1. People originally thought the platypus was a fake animal. 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.

An illustration of the platypus from 'The Naturalist's Miscellany' An illustration of the platypus from 'The Naturalist's Miscellany.' (Photo: The Naturalist's Miscellany)

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 but it can be lethal to smaller animals. Scientists think that the venom, which increases in production during mating periods, is intended to incapacitate rival males. Speaking of reproduction ...

3. Platypuses are egg-laying mammals. The platypus isn't the only venomous mammal, and it isn't the only egg-laying mammal (the four species of echidna also lay eggs). 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 between two to four weeks and then 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.

A platypus swims underwater with a worm in its bill Platypus eat small, bottom-welling invertebrates, like worms. (Photo: John Carnemolla/Shutterstock)

4. Platypus milk could combat superbugs. Since platypuses don't have a sterile away to deliver milk, it would need to provide additional protections against bacteria in the environment. In 2010, scientists discovered that platypuses' milk contained antibacterial properties that could help us in the fight against antibiotic resistance. A 2018 study published in the journal Structural Biology Communications determined that 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 among proteins, and it could indicate a unique, therapeutic function as well.

5. Platypuses have 10 sex chromosomes. Mammals typically just have a single pair of chromosomes that determine sex, but platypuses have five pairs, a real rarity in mammals. For mammals, two chromosomes is all you need to determine sex, but for the platypus, it's always 10 chromosomes that make up their sex. 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.

6. 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 2008 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.

Platypus swimming in water When platypuses go diving, they make themselves basically waterproof. (Photo: worldswildlifewonders/Shutterstock)

7. Platypuses don't have teeth, either. 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.

8. Platypuses 'see' with their bills underwater. When they dive underwater, platypuses are basically sightless and are 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.