The steep decline in share price was triggered by the news, released a day earlier, that Senk had resigned from Urban on Monday and had been replaced by its president and board chairman, Richard A. Hayne, 64, who founded the company in 1970.
"We have known and respected Glen for more than a decade - as much for his creative vision and inspired leadership as for his exceptional management and operational ability," the Yurmans said. "His arrival will allow us to truly focus on what we love doing - designing - while we collectively build an even greater global brand and the company we've always wanted."
Senk had recently shaken up Urban's management in a nearly yearlong battle against lackluster sales of mostly women's apparel at its Anthropologie and Urban Outfitters retail divisions. A series of apparent fashion misses had dragged down sales and profit by forcing the company to clear merchandise at deep discount over successive quarters.
Investors had been puzzled by the timing of Senk's departure, given that he had predicted the company would rebound with new spring inventory offerings.
In 18 years with Urban Outfitters, Senk helped launch its Anthropologie chain and became a close aide to Hayne, who remained active in the corporation's day-to-day affairs even after the board created the CEO position in 2007 and chose Senk to be the first to fill it.
Senk did not return messages Wednesday seeking comment. The company, with headquarters at the Philadelphia Navy Yard, has said Senk would remain on board for a while during the transition.
Contact staff writer Maria Panaritis at 215-854-2431,
or @panaritism on Twitter.