Newbie ex-Oracle person's question: Oracle ROWID = PSQL OID, Orac le ROWNUM = PSQL ???

Oracle has a ROWNUM pseudo column that works like this ...
TEST>select callid, rownum from cs_calls where rownum < 5;
   CALLID     ROWNUM
---------- ----------     7806          1     7807          2     7809          3     6443          4

4 rows selected.

... which can be quite handy.

Is there something like this in PSQL?

By the way, having used Oracle since 1987 it's a pleasure to use PSQL.
Someone actually thinks about the implemented features.
For example, Oracle's implementation of ROWNUM gives them in the order the
rows were BEFORE the ORDER BY, which is not of much use as adding an ORDER
BY jumbles them up.  Duh!

Thanks in advance for any responses.