ИСТИНА

In contrast with most extant animal phyla that have representatives in the early Cambrian (e.g. Chengjiang fauna from China), the origin and early evolutionary evolution of Phoronida lacks convincing fossil evidence. Iotuba and Eophoronis from the Chengjiang fauna, were tentatively interpreted as primitive phoronids based on poorly preserved specimens. Alternatively, Eophoronis was compared with Louisella, a priapulid from the middle Cambrian Burgess Shale. Exceptionally well-preserved specimens allow here the first detailed description of Eophoronis. It has a ca 4 cm long cylindrical worm-like body. The surface of its trunk bears transverse ripples and dense setae (or cilia ?). The gut has a U-shape with a conspicuous expanded gastric area. Rows of tentacles form a horseshoe-shaped structure around the epistome in the anterior part of the body. Undetermined organic detritus attached to these tentacles suggest the presence of mucous secretion. The slit-shape mouth and the anus both open in the anterior region. A putative juvenile penetrates the body wall of the adult as seen in extant phoronids. One complete specimen is encrusted with tiny sand grains or organic debritus. This external and internal morphologies are typical of extant phoronids. Other features observed in the posterior part of Eophoronis are interpreted as possible ovaries (oocytes) and testis (sperm) attached separately along the intestine. This configuration is typical of hermaphroditic extant phoronids. In conclusion, Eophoronis is considered here as the earliest representative of Phoronida with anatomical features and encrusting habits comparable with modern forms.