网状遗迹—新属——Neurodictyon n.ichnogen.

NEURODICTYON:A NEW NETWORK ICHNOGENUS

新遗迹属Neurodictyon n.ichnogen.发现于陕西富平中奥陶统金粟山组。遗迹为不规则网状,穴道有主次之分,主、次穴道大致平行。可能是一种居住兼进食的系统潜穴构造,造迹生物可能是微小的蠕虫类(?)。

A new network ichnogenus Neurodictyon was discovered from the Middle Ordovician deep-water deposits of the Jinshushan Formation of Fuping County, Shaanxi Province. A brief description of the ichnogenus is as follows: Neurodictyon n.lchnogen. Type lchnospectes Neurodictyon shaanxiensis n. ichnosp. Derivation or name From the combination of Greek neuro, vein. and dictyo. net. Diagnosis Irregular quadrilateral networks; composed of primary and secondary tun- nels. with each of them broadly parallel, respectively; primary tunnel connection may oc- cur occasionally. Discussion The new ichnogenus can be easily distinguished from other networks by the grading of its network tunnels and the quadrilateral net shapes. But the net shapes of some regular networks, such as Squamodictyon and Paleodictyon. are scale-shaped and hexagonal respectively; as to the Ramidictyon Seilacher 1977, it belongs to hexagonal nets with regular vertical outlets in prescribed positions. Preliminary analysis suggests that Neurodictyon n. ichnogen. is probably not true agrichnion, its trace-maker may be sediment-feeder to a certain extent. Occurrencc Ordovician. Neurodictyon shaanxiensis n.ichnosp. (Pl. I. fig. 1-6; text-fig. 2) Derivation of name. From shaanxi Province. Holotype. Pl. I, fig. 2. Description Primary tunnels are generaly longer than secondary ones, being 1. 3-2 and 0. 6mm respectively. and the net diameter changes greatly, from 3 to 13mm. Occurrence Middle Ordovician Jinshushan Formation. Fuping County. Shaanxi. China.