WhatsApp beta has been updated to version 2.16.70.
The update brings along a UI change, where the appbar buttons (below) have been removed and replaced with a slightly more dynamic set up.
The update combines the Send key and the Voice Message key. When you are typing (screen shot left) the Send key is available, and otherwise (screen shot right) the button turns into a voice message key. The other buttons have found their home on other parts of the screen, and are part of WhatsApp’s revamp of its UI which has been going on for some months now.
WhatsApp beta is a closed beta, but the improvements should come to the mainstream version of the app in due course.