Looks like your system uses some kind of external bar to "clip" PCI cards in place. Not sure how to remove it. Maybe it slides straight up to unclip from the cards' end plate lip. At any rate, looks like you need to remove that bar first. Once removed, I expect you'll find one of these situations:
(a) The card has a screw on the end plate that was hidden by the bar-clip thing (unscrew it), or
(b) There is no screw at all as it was held in place by the bar-clip thing. (nothing more to do).
Then, assuming you took care of the tab at the end of the lci slot, just pull the card straight out.