The genealogy of the Seigneurs de Semur, included in the cartulary of Marcigny-sur-Loire and dated to , names "Dalmace" as son of "Jaufrois qui eut la fille de Dalmas Vicomte de Briode". His paternity is deduced from the charter of "Gaufredus" dated  which names "patris mei Dalmatii [et] avi Gausfredi" as well as "Tetbaldus comes avunculus ipsorum" (referring to Geoffroy and Dalmas, sons of this Dalmas).
He succeeded his father in  as Seigneur de Semur.
[Dalmas] married Aramburge, daughter of ---. The genealogy of the Seigneurs de Semur, included in the cartulary of Marcigny-sur-Loire and dated to , names "Aremburge qui fut sœur du comte Tetbauld" as wife of "Dalmace". It is uncertain to whom this refers, but if it is Thibaut Comte de Chalon the entry is an error as he was her husband's brother. A manuscript now lost records "Aremburgis de Vergy" as wife of "Dalmatii…de Sinemuro". "Gaufredus" donated property to the abbey of Marcigny-sur-Loire for souls of "genitoris mei Dalmatii et genitricis meæ Aremburgis" by charter dated to [1055/80] which refers to "Cluniacensis monasterii ubi domnus Hugo frater meus præest".
The Vita S Hugonis records that "Dux Burgundie, gener eius" killed the father of St Hugues (abbot of Cluny) by his own hand. 1