Ecology of the Mushroom Kingdom — The Yoshi

Throughout history, there have been men and women brave enough to take unpopular stances in the name of scientific progress. Galileo was jailed for his astronomy research. Hypatia was brutally murdered by a mob of fanatics for being a woman highly skilled in mathematics and philosophy. Today, I am humbly prepared to join their ranks if need be, for I am about to remark upon a fact that for far too long has been suppressed and denied by mainstream Mario scholarship.

Yoshi is not a dinosaur.

If yoshis were dinosaurs, they would almost certainly belong to the therapod sub-order, more specifically they resemble the dinosaurs of the coelurosauria clade which includes velociraptors, tyrannosaurus rex, troodon and struthiomimus. Yoshis are bipedal and, at least in their earliest forms, have retrograde forelimbs. These are features they share with coelurosaurs. Their bodies superficially resemble struthiomimus or troodon as well. However, Yoshis are missing one critical feature that all coelurosaurs share: feathers! Nearly every coelurosaur we know of today had feathers. Most recently a tyrannosaurid fossil (Yutyrannus huali) was found with feathers.

Sadly, the feather-less yoshi is most likely not a true dinosaur. That does not mean, however, that yoshi’s fossil record is not prehistoric or fascinating on its own.

All lizards, crocodiles, snakes, dinosaurs and birds belong to the clade known as “diapsids”. Diapsids are named for the two holes along the side of their skulls. While modern lizards have only one hole and modern snakes have no holes, they are still considered to be diapsids because of what they evolved from. While not many examples of yoshi skeletons exist in the Mario games, there are a few clues. The skull of a bone dragon in Yoshi’s Story resembles a yoshi and has only one hole along its side. While I am far from a trained paleontologist, I would place yoshi in the infraclass Lepidosauromorpha, making it a relative of snakes, lizards, tuataras and plesiosaurs. The question is, do yoshis fit into any of those orders or do they deserve their own separate order within Lepidosauromorpha? Considering that they have limbs, I think its safe to say that yoshis do not belong in the same suborder as snakes. Yoshis lack flippers, but more importantly also have completely different shoulder and pelvis joints than plesiosaurs. That leaves lizards and tuatara.

There is another aspect of yoshi biology we haven’t touch upon yet, that of reproduction. Yoshis show no sexual dimorphism, males and females are virtually identical and both are capable of laying eggs. In fact, yoshis may not even have a distinction between male and females of the species. Yoshi reproduction seems to be done through parthenogenesis, a “mother” yoshi will produce and fertilize an egg on its own and create a clone “daughter”. This is not unheard of in reptiles, especially among lizards. The whiptail lizard is completely female, and other species (including the komodo dragon) may go through periods of cyclical parthenogenesis, where members of the species can reproduce either through sexual reproduction or through self-reproduction. This would seem to be evidence that yoshis are an advanced species of lizard, but I would personally classify them within the order of Rhynchocephalia, or tuatara.

Tuatara are a “living fossil” from New Zealand. While they superficially resemble lizards, they are in fact their own order and contain many traits unique among all tetrapods (a group that includes all amphibians, reptiles, birds and mammals). The most intriguing and controversial aspect of the tuatara is most likely its “third eye”, a photoreceptive organ located on its head. The yoshi (Sphenodon dinosauramimus) has an even more advanced and sensitive form of this organ located within its robust snout. While scientists are unsure what the modern day tuatara uses this organ for, the yoshi’s has evolved to become very useful in finding food. Young yoshis are able to detect hidden, underground-growing fruit by “sniffing” the air to detect abnormal heat signatures.

There is more evidence of an ancestral link between yoshis and modern tuatara. Tuatara do not have real teeth, but rather sharp points of bone that stick out of the jawbone. These wear down over time, forcing older tuatara to subsist on softer prey that they can swallow whole. The yoshi does not need teeth at all, and so has lost even these boney points. Yoshis are fully omnivorous, eating both fruit and live prey such as koopas and moles. Whatever the yoshi can grasp with its chameleon-like tongue is fair game. Fruit is the primary food source, but meat is apparently necessary for obtaining the energy and nutrients needed for parthenogenesis. The yoshi’s elastic and powerful throat muscles constrict and suffocate the prey. Yoshis swallow inorganic objects such as rocks, certain blocks, giant keys and springboards that remain in the stomach and help break apart their food. This is similar to the behavior observed in crocodiles and certain birds.

There are at least two species often assumed to be related to the yoshi, the rex and the birdo. Rexes (Longisquama dracoforme) only superficially resemble yoshis and are in fact much closer related to an even older group of enigmatic diapsids. The vestigial “wings” on their back are actually feather-like scale protrusions. There is active debate among paleontologists today where longisquama sits in the fossil record. It may be an ancestor to dinosaurs and birds or an ancestor to pterosaurs.

The birdo is much more difficult to classify. Like the yoshi, it is an apparently genderless diapsid that reproduces through parthenogenesis. But unlike the yoshi its cloaca (the all-purpose reproductive and waste orifice shared by reptiles, birds and some mammals) seems to be attached to its head! This is completely unheard of in any animal today, and scientists are understandably baffled as to how such a feature could have evolved. It apparently serves primarily as a defensive mechanism, allowing the birdo the ability to explosively fire unfertilized eggs and flaming waste at potential predators. The birdo’s face cannon also seems to serve as its mouth. Has birdo evolved some kind of strange, two-way digestive/reproductive orifice!?

While no literature on the internal workings of birdo exists, I would like to propose a simple theory. The birdo’s face cannon is not actually its mouth nor its cloaca, but rather a specialized muscle that leads to both orifices within the birdo’s body. The geographical location known as Yoshi’s Island contains several species that live on stolen yoshi eggs, most notably the nimble and clever rodent known as little mousers. Birdo’s ancestors began carrying their fertilized eggs internally to protect them from thieves. As yoshis often use unfertilized eggs as defensive missiles against larger predators, this adaption still had to include access to unfertilized eggs. Over millions of years, birdos were selected who were able to both protect their fertilized eggs and also retain easy access to unfertilized eggs. This led to the development of an internal cloaca and a single muscle that increased the birdo’s ability to defend itself. The eggs are carried through a passage from the cloaca up to the face where it is then “spring-loaded” forward through the funnel-shaped muscle. As this meant that waste had to be disposed through the same system, birdos were selected that were able to fire caustic waste at attackers in the manner of some modern sea birds. Eventually, this waste became so caustic and volatile that it was able to be ignited as a “fireball”. So while it appears that birdo’s waste/reproduction organ is located on their face, there is actually an internal pathway that carries eggs and waste up to the face-cannon.

If you’ve enjoyed this edition of Ecology of the Mushroom Kingdom, I recommend Tetrapod Zoology for more information on how reptiles, dinosaurs, birds and mammals in the real world evolved. Next time on Ecology of the Mushroom Kingdom, we’ll move away from the animal kingdom and start looking at the unique plant life.