贵州台江凯里组的遗迹化石Treptichnus

Ichnofossil Treptichnus from the Kaili Formation at Taijiang County,Guizhou Province

贵州台江下—中寒武统凯里组中产有丰富的、保存良好的Treptichnus Miller,计5个遗迹种(其中包括2个新遗迹种):T.bif urcus Miller,T.pedum(Seilacher),T.pollardi Buatois and Mángano,T.arcus n.ichnosp和T.taijiangensis n.ichnosp.,并与节肢动物的觅食迹、爬行迹和游泳迹等共生,属Cruziana遗迹相。产于凯里组的Treptichnus可能为节肢动物的居住迹。随着造迹生物身体的增长和沉积物的增厚,造迹生物在原潜穴的基础上不断地开拓新的潜穴,而构成三维空间复杂的潜穴系统。

Abundant and well-preserved ichnofossil Treptichnus Miller, including T. bifurcus Miller, T. pedum （Seilacher）, T. pollardi Buatois et Mángano, T. arcus n. ichnosp, and T. taijiangensis n. ichnosp, are found in the Lower Middle Cambrian Kaili Formation at Taijiang County, Guizhou Province, China. They usually occur together with the resting, crawling, walking, swimming and feeding traces produced by arthropods, such as Rusophycus, Cruzian, Diplichnites, Dimorphichnus, Beaconichnus and Monomorphichnus. So the sedimentary environment belongs to Cruziana ichnofacies of Seilacher （1964, 1967）. The maker of Treptichnus from the Kaili Formation may be a domichnia produced by arthropods. When the body of the maker grew and lengthened and the deposits thickened, the maker would exhume a new burrow based on original burrow, and built a complex three-dimensional burrow system. Description of New Ichnospecies Ichnogenus Treptichnus Miller, 1889 Treptichnus arcus n. ichnosp. P1,Ⅱ-2, 3; Fig. 3-4 Holotype： GK7122, P1. Ⅱ-2 Description： Three-dimensional burrow system. The horizontal and bow-shaped burrow segments branch regularly off near the top of the bow; tube surface smooth or small tumors. Infullings essentially differ from surrounding rock in lithology. The segments are 14 to 20 mm long; the cylindrical tubes are 1.8 to 2.2 mm in diameter. Discussion： The new ichnospecies is similar to Treptichnus （Phycodes） pedurn Seilacher in branching mode, but the former segments are longer, bow-shaped, and curved upwards near open. The bow-shaped and longer burrow segments of T. arcus are main characteristics to distinguish from others of Treptichnus. Occurrence： Kaili Formation （Lower--Middle Cambrian） at Taijiang County, Guizhou Province, China. Treptichnus taijiangensis n. ichnosp. P1.Ⅱ-3-6; Fig. 3-5 Holotype： GK7119; P1.Ⅱ-5 Description： Zigzag, straight or curve three-dimensional burrow system. U-shaped burrow segments perpendicular or oblique to planes and arranged regularly at an angle to the axis of the trace. Burrow surface is smooth. Near the mouths bedding of the segment, the segments with wall strongly curve to the bedding plane is hook-like. The fillings in the tubes differ from surrounding rock in lithology. The angles between segments and the axis of the trace vary from 30 to 50; the segments are 15 to 21 mm long; the tubes are 1.8 to 2.2 mm in diameter. Discussion： The new ichnospecies differs from Treptichnus bifurcus Miller in the longer and U-shaped burrow segments, strongly curved and hooked the tubes near the mouths. It differs from T. triplex Palij in that the latter has three narrow ridges on the burrow surface. Occurrence： Kaili Formation （Lower-Middle Cambrian） at Taijiang County, Guizhou Province, China.