Looking at user_menu() to check the answer for another question, I noticed the function contains the following definition.
$items['admin/people/create'] = array( 'title' => 'Add user', 'page arguments' => array('create'), 'access arguments' => array('administer users'), 'type' => MENU_LOCAL_ACTION, );
The page callback is not explicitly defined.
Reading the definition of
MENU_LOCAL_ACTION given in hook_menu(), I read the following:
MENU_LOCAL_ACTION: Local actions are menu items that describe actions on the parent item such as adding a new user or block, and are rendered in the action-links list in your theme.
That doesn't explain which is the involved page callback that is called to handle that menu item.
Which is the page callback that is called to handle a
MENU_LOCAL_ACTION menu item? Is there any other property that is necessary to define such menu items?