As you may know, the platypus and the echidna are kind of the oddballs in the mammal family. They are the only mammals that lay eggs instead of giving live birth.
The platypus is also thought of by some as one of the strangest animals in the animal kingdom due its duck bill, beaver tail, otter feet, and capacity to inject venom into threatening animals.
The platypus genome is actually pretty fascinating. When platypus DNA was compared to the DNA of other mammals, it turns out certain genes were actually missing. These genes were for protein cutting enzymes called proteases, which are made only in the stomach.
Even more interesting was how these genes were actually present, but disabled by virus-like pieces of DNA. Several other stomach related genes are also missing from platypus DNA.
So what’s so strange about that? Just about every vertebrate has a stomach, but the platypus has actually lost its stomach over the years. The stomach for the platypus is a useless tube connecting the esophagus to the intestines. This means that over the years, the platypus has actually evolved out of its stomach.