One of the oldest fish found from Lagerstatte (remarkable fossil locality) located in Haikou area of Yunnan Province, southwest of China, by a research team of the Northwest University headed by Professor Shu Degan. It is now grouped into Agnatha. Its length is as short as 2 to 3 cm, but vertebral elements and eyes on the head can be recognized. It also has a dorsal fin and developed myotome with 6 to 9 gill slits. Fossils often contain several individuals and thus they may have been schooling when alive. It was published in the journal Nature in 1999 together with Myllokunmingia. In 2003, another agnathan Zhongjianichthys were found. Three species of fish have now been recovered from the same strata.

Marine animal published in Nature in the year 2001. Its body is covered by cuticle and divided into two parts, i.e. anterior segmented region and posterior flattened region. Anterior part is divided into 5 segments. The segments have gill sacs. Gill slits can also be seen under the gill sacs. It is speculated that Vetulicola took sea water and organic matter through anterior mouth and discharged them through gill slits to absorb oxygen and nutrients in sea water. The posterior part is flattened and probably segmented into 7 parts. Posterior end has a rounded shape. As such features are not seen in any other animals, a new phylum Vetulicolia, exclusive for Vetulicola, was proposed.

The Cambrian Explosion and Vertebrates

Until the very end of previous century, vertebrates were thought to have appeared in Ordovician period which began about 490 million years ago. However, predating fish fossils have been found in strata from 530 million years ago in the Yunnan Province of China. It thus became evident that fish are one of the various animal groups that appeared during the Cambrian explosion. All animals having back bones, including humans, are grouped into vertebrates to which fish also belong. The oldest vertebrates were primitive fish of several cm in length and did not have a jaw. How they appeared and what kind of process generated them during the Cambrian explosion, which lasted no more than 10 million years, no one can say.

Quest for the Pathway from oldest Deuterosotmia to the Vertebrates

All triploblasts are classified into Protostomia and Deuterostomia according to the difference in the embryogeny process. Many groups including arthropods and molluscs belong to Protostomia. On the other hand, echinoderms and vertebrates belong to Deuterostomia. It is clear that vertebrates and echinoderms branched from the most primitive ancestor of Deuterostomia at some stage during the Cambrian explosion.

At this moment the most primitive Deuterostomia is thought to be Vetulicolians. They have only been found from the strata Qiongzhusi Formation in Yu’anshan Member of 530 million years ago. They are thought to be primitive Deuterostomia which share some charactaristics with Protostomia, i.e. they have features of Protostomia including cuticle-like structures and segmentation found in arthropods. But they have five pairs of gill sacs and gill slits inward and thereof are similar to that of Deuterosomia. When originally found, Vetulicola, typical Vetulicolians, were classified into arthropods. In the same strata, fossils of Echinoderms, Hemichordates and Cephalochordates were also found. Haikouichthys, Myllokunmingia and Zhongjianichthys were also found from Qiongzhusi Formation. Detailed research of these fossils enables us to speculate the evolutionary process from Vetulicolians to vertebrates. Professor Shu Degan of the Northwest University of China is now approaching a solution to the outstanding questions concerning vertebrate evolution by studying these fossils.

Chengjiang and Haikou of Yunnan Province, China, are wonderful Lagerstatten (remarkable fossil localities). Fossils from strata of shales still keep three dimensional structures, such as gill slits below cuticles of Vetulicola and the nerve cord of Hemichordata. With the support of Professor Shu, who is also the discoverer of the oldest fish, GNHM exhibits 8 specimens of fossil including Vetulicolians and the oldest fish. Professor Shu Degan is an honary director of GNHM.