Prickly Pear Cactus (Opuntia engelmannii)
Location: Saguaro National Park, Arizona, USA
The Prickly Pear (Opuntia engelmannii) is another common cactus found in Arizona's Saguaro National Park. Unlike the Giant Saguaro, which grows very tall, the Prickly Pear grows in shrubby clumps. Its spines are long and straight, like needles*. In the spring, the Prickly Pear bears bright yellow flowers.
* Here's a macro photo of the Prickly Pear, showing its long spines.