Santa Monica startup Gradient X only recently publicly launched its platform for buying and selling mobile ads. But that hasn’t stopped Redwood City ad tech firm Amobee from taking notice.

The two companies announced Thursday that Amobee has acquired Gradient X for an undisclosed price.

Through the acquisition, Amobee is gaining Gradient X founders and ad tech veterans Brian Baumgart, Michael Lum and Julie Mattern. The Gradient X team will remain local and Amobee - which is owned by Singapore's SingTel - will open a sales office in town.

Steve Hoffman, Amobee's chief financial officer, said the company at first considered teaming with Gradient X but decide to make the partnership more permanent.

"Amobee has a comprehensive and advanced mobile platform already, but as technology has evolved, we will either build or buy to keep up," he said. "In this case, the attraction was immense. The technology that Brian and his team have created is the leading technology in this area of mobile advertising."

Gradient X operates a real-time bidding platform for mobile ad transactions. It also provides back-end software so marketers can track the performance of their ads.

Baumgart said the company was looking for a partnership that would help the company scale its platform.

"To be market leading in a competitive landscape, you often need a partner," he said. "Amobee really has a solid history of being able to bring together the right pieces of the technology puzzle at the right time."

Less than two years old, Gradient X had only raised $3.75 million in institutional funding. Local investors include Upfront Ventures, Crosscut Ventures and Siemer Ventures. It publicly launched its platform in June.

Mark Suster, a partner at Upfront Ventures, said Gradient X could have built a large ad tech company on its own, but has found a like-minded owner in Amobee.

"We think they are talented enough to build something super big," he said. "They got out of the gate quickly and built one of the best platforms out there. But they have a shared vision with the Amobee team and working with them, they can build something even bigger."