Most non-legendary Pokemon have an evolution line of some sort. There were a handful of Generation 1 Pokemon that didn't have an evolution line whatsoever, but that was mostly rectified with Generation 2's baby Pokemon and Generation 4's new evolutions. One Gen 1 Pokemon that has yet to receive any kind of evolution or baby form is the Wild Bull Pokemon Tauros, so one Pokemon fan has taken matters into their own hands.
Pokemon fan and Reddit user xSilentWalrusx has created fan art designing their own regional variant of Tauros, giving that regional variant an evolution in the process. This regional variant of Tauros turns the Normal-type Pokemon into a Rock/Ground-type, tweaking his color scheme and adding rocks to his body. This version of Tauros evolves into Steeros, which swaps the rocks for steel, making it a Steel/Ground-type Pokemon.
Regional variants, for those who haven't been following the Pokemon franchise closely in recent years, is a relatively new concept that was introduced in Pokemon Sun and Moon. The basic concept is that certain Pokemon can take on different appearances and types based on the regions they're found in. For example, while most Pokemon fans know Vulpix as a Fire-type Pokemon, the Alolan Vulipx variant is an Ice-type Pokemon instead.
This concept of a regional variant and evolution for Tauros is just the latest take. Pokemon fan Bearys_Cave also designed a regional variant for Tauros, though their version is much darker than the one presented by xSilentWalrusx. Bearys_Cave designed a Ghost/Steel-type version of Tauros that doubles as a criticism of bullfighting practices in Spain, with their version of Tauros stuck with steel javelins.
It will be interesting to see if Nintendo and Game Freak wind up introducing their own regional variant for Tauros in the upcoming Pokemon Scarlet and Violet games. After all, the Pokemon Scarlet and Violet region is believed to be based on Spain, a country that has big cultural ties to bulls. If the theory that the Pokemon Scarlet and Violet region is based on Spain pans out, one has to imagine that a regional variant for Tauros would be in the cards, or alternatively, that the Pokemon is featured in the game in its current form. Then again, when one considers the controversies surrounding bullfighting, it may be best for Game Freak and Nintendo to avoid making reference to it.
Hopefully more information on Pokemon Scarlet and Violet's region comes to light sooner rather than later. While E3 2022 is canceled, it's possible Nintendo will be hosting its usual June Nintendo Direct regardless, and if so, one has to imagine that Pokemon Scarlet and Violet would likely be featured at the event.