在蒙古南戈壁的Bayan KhoshuuRuins剖面原归入到志留系Mandalovoo组尕屋 (Gavuu)段的地层中发现了牙形刺Caudicrioduswoschimidtiwoschmidti,这是泥盆纪最早期牙形刺带化石在蒙古的首次发现。尕屋 (Gavuu)段的下部属志留系 ,但其上部 ,即采集牙形刺样品M 9～M 12的层位肯定属下泥盆统 (下洛霍考夫阶 ) ,而不是下志留统。Mandalovoo组应当改为Mandalovoo群 ,它的三个段应提升为三个组 The genus Caudicrioduswoschimidtiwoschmidti is found in the strata of the Bayavan Khoshuu Muins in the southern Gobi area of ​​Mongolia, originally found in the Gavuu section of the Silurian Mandalovoo Formation, the first discovery of the first Devonian fossil from the Devonian in Mongolia . The lower part of the Gavuu section belongs to Silurian, but the upper part of the upper part of the Gypsophila sample, M 9 ~ M 12, must belong to the Lower Devonian (lower Lohkauf) rather than the lower part Retained. Mandalovoo group should be changed to Mandalovoo group, its three paragraphs should be promoted to three groups