The ancient fish Polybranchiaspis liaojiaoshanensis, belonging to the class Galeaspida, Devonian age (about 400 million years ago), was examined by Professor. Dr. Ta Hoa Phuong, found in 1990 in Tung Vai commune, Quan Ba district, Ha Giang province, in sediments of the Khao Loc formation (D1-2 kl). The famous French paleoichthyology – Academician Philippe Janvier has researched and confirmed that the species information is completely accurate.

Representatives of the class Galeaspida have a head shield made of hard bone, which covers the front part of the body and is often preserved in a fossil state. The shield has a flat head, similar in shape to a helmet. In front of the head shield there is a wide round or oval back door, which is where water is absorbed to help with breathing. Two round eye sockets located far on both sides. The top of the shield has deep grooves. The most characteristic is the groove system similar to the lateral line system, in which there is a main groove running along both sides of the shield and many horizontal grooves, in some cases the horizontal grooves continue to have secondary branches. In addition, on the shield there is also a groove connecting the groove system on both sides of the shield, the grooves in front of the eyes, the grooves behind the eyes, etc. The two grooves in front of the eyes are often bunched together at the pineal foramen. The top of the shield is thickly covered with embellishments in the form of grids, rosettes or tabs. The mouth and gill slits are located on the underside of the head shield.

Applying 3D Mapping technology – using images and light to create 3D effects on the surface of the specimen, Hanoi Fossil Museum has vividly recreated the form and life of the fish that was extinct hundreds of millions years ago.