It's still dynamically typed. The dialyzer ("discrepancy analyzer") can detect many kinds of type errors statically by doing dataflow analysis over the possible types yielded by successful execution, but it's an external tool. Like lint, not part of the core language.

For a good overview, check "Gradual Typing of Erlang Programs: A Wrangler Experience " (http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.160....) and/or "Practical type inference based on success typings" (http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.62....).