Pomatrum

Xidazoon; Temporal range: Cambrian
Scientific classification
Kingdom:	Animalia
Phylum:	Vetulicolia; Shu, et. al. 2001
Class:	Vetulicolida; Chen & Zhou 1997
Family:	Didazoonidae; Shu & Han 2001
Genus:	Xidazoon; Shu, Conway Morris & Zhang 1999

The genus Xidazoon was erected by Shu, et. al. (1999) based on fossils found in the Qiongzhusi (Chiungchussu) Formation, Yu'anshan Member (Eoredlichia zone), Lower Cambrian, Haikou, (Kunming), about 50 km west of Chengjiang, China. It currently consists of the single species Xidazoon stephanus.

The fossils show that the body of the animal was divided into two parts. The anterior part of the body is moderately inflated, with a prominent mouth circlet. It has faint transverse divisions towards the front, but is otherwise smooth. The mouth circlet consists of about 25 plates divided into inner and outer regions. The posterior part of the body tapers towards front and back (diamond-shaped), and is divided into six segments covered in cuticle with three less well-defined segments at the anterior end. There are short spines at the posterior tip. The authors describe an alimentary canal with terminal openings and a rectum with what might be dilator muscles.

References

Shu, D.-G., Conway Morris, S., Zhang, X.-L., Chen, L., Li, Y. and Han, J. 1999. A pipiscid-like fossil from the Lower Cambrian of south China, Nature, 400:746-749. (August 19 1999).
Shu, D.-G., Conway Morris, S., Han, J., Chen, L., Zhang, X.-L., Zhang, Z.-F., Liu, H.-Q., Li, Y., and Liu, J.-N. 2001. Primitive Deuterostomes from the Chengjiang Lagerstätte (Lower Cambrian, China), Nature, 414:419-424. (November 11 2001). [1].