Several species have gone extinct over the course of the 20th century, largely due to habitat loss, pollution, over-exploitation, and other human-induced factors. Some notable examples include:

1. **Passenger Pigeon (Ectopistes migratorius):** Once one of the most numerous bird species in North America, the last known individual died in captivity in 1914.

2. **Thylacine (Thylacinus cynocephalus):** Also known as the Tasmanian Tiger, the last known thylacine died in captivity in 1936.

3. **Carolina Parakeet (Conuropsis carolinensis):** Native to the southeastern United States, the last confirmed sighting was in 1918, and the species was declared extinct in 1939.

4. **Pinta Island Tortoise (Chelonoidis abingdoni):** Lonesome George, the last known individual of this species, died in 2012.

5. **Spix’s Macaw (Cyanopsitta spixii):** This Brazilian parrot species became extinct in the wild in the early 2000s due to habitat loss.

These are just a few examples, and unfortunately, there are many more species that have been lost during the 20th century. Conservation efforts are ongoing to prevent further extinctions and protect endangered species.