San Diego-based Underground Elephant, a startup focused on the CPA-based, performance based advertising market, said today that it has opened up an office in Santa Monica. The firm said it is looking to tap the talent in the Los Angeles are in the affiliate ad network industry. As part of the new office, the firm said it has hired Jennifer Horwood, who the firm worked previously at another ad network, and Derek Chew, previously at Pricegrabber.com and Yahoo. Underground Elephant is headed by Jason Kulpa. The firm said a number the hires were enabled by recruiting firm Neohire.