The South Arabian alphabet is thought to have developed from the Proto-Sinaitic alphabet in about the 9th century BC. It is known from inscriptions found in Eritrea, Babylonia and Yemen dating from between 9th century BC and 7th century AD, and was used to write Sabaean, Qatabanian, Hadramautic, Minaean, Himyarite and proto-Ge'ez, extinct Semitic languages once spoken in southern parts of the Arabian peninsula. It is also known as the Old Yemeni alphabet or المُسند (musnad).
The South Arabian was used for monunmental inscriptions, and was also carved into wooden sticks, which were used as everyday documents.
The top row of letters are written in monumental style, while the bottom row of letters are in cursive style.
Source: http://www.barnard.nl/yemen/mb88.html
Information about the South Arabian alphabet
http://en.wikipedia.org/wiki/South_Arabian_alphabet
http://www.ancientscripts.com/s_arabian.html
Written in Stone: Inscriptions from the National Museum of Saudi Arabia
http://www.mnh.si.edu/epigraphy/
Corpus of South Arabian Inscriptions
http://csai.humnet.unipi.it
Ancient South Arabian Inscriptions in Baynun (Yemen)
http://www.barnard.nl/yemen/
Akkadian, Amharic, Arabic, Aramaic, Argobba, Canaanite, Chaha, Dizin, Ge'ez, Hadhramautic, Hebrew, Himyaritic, Maltese, Mandaic, Nabataean, Phoenician, Qatabanic, Redjang, Sabaean, Sabaic, Silt'e, Syriac, Tigre, Tigrinya, Ugaritic,
Ancient Berber, Arabic, Hebrew, Mandaic, Manichaean, Middle Persian, Nabataean, Parthian, Phoenician, Paleo-Hebrew, Proto-Sinaitic / Proto-Canaanite, Psalter, Punic, Sabaean, Samaritan, Sogdian, South Arabian, Syriac, Tifinagh, Ugaritic