Canonical decided not to do an earlier beta of Ubuntu 13.04 while other *buntu derivatives still followed the older release schedule/process. Announced today was the second and final 13.04 beta, or the first and only beta for Ubuntu itself.
Steve Langasek announces:
The Ubuntu team is pleased to announce the final beta release of Ubuntu 13.04 Desktop, Server, Cloud, and Core products.The various flavors of Ubuntu 13.04 in their latest beta state can be downloaded here.
Codenamed "Raring Ringtail", 13.04 continues Ubuntu's proud tradition of integrating the latest and greatest open source technologies into a high-quality, easy-to-use Linux distribution. The team has been hard at work through this cycle, introducing new features and fixing bugs.
Together with Ubuntu 13.04, Kubuntu, Edubuntu, Lubuntu, Xubuntu and Ubuntu Studio also reached Final Beta status today. We also welcome two new flavors, Ubuntu Gnome and UbuntuKylin, which are participating in the Ubuntu release process for the first time this cycle.
The final release of Ubuntu 13.04 is expected on the 25th of April.