(Reuters) - Blank-check firm Big Sky Growth Partners Inc on Friday filed for an initial public offering of up to $300 million on the Nasdaq, it said in a regulatory filing. The company is co-founded by Mark Vadon, former chairman of online pet products retailer Chewy Inc, who is currently the chief executive officer of Big Sky Growth. Special purpose acquisition companies, or SPACs, are shell companies that raise money in an IPO to pursue an acquisition at a later date. They serve as an alternative to a traditional IPO for companies looking to enter public markets. Big Sky Growth filed for an IPO of up to $300 million, a placeholder amount that is expected to change. It plans to list its common shares on the Nasdaq Capital Market under the symbol “BSKYU”.