What indication is there that Thorin is the leader of the Dwarves?

Thorin II Oakenshield is a character from 'The Hobbit', a fantasy novel by Author J.R.R. Tolkien about a ragtag group of adventurers who set out in search of a lost Kingdom and a treasure which were seized by a terrifying dragon. Thorin is a descendant of a legendary dynasty of dwarf lords, and at every time he demonstrates why he's the leader of the company, by being the one who chairs all the meetings and the one who makes the most important decisions which affect all of the company, even if these are not really for the best all the time.