Histological observation of some primitive euconodonts of Late Cambrian from Liaoning

The histology of some euconodonts of Late Cambrian from Benxi and Fuxian County, Liaoning Province is studied by the oil-immersion technique. The histological characteristics of six primitive species of euconodonts - Proconodontus muelleri， Proconodontus tenuiserratus， Granatodontus ani， Rotundoconus tricarinatus， Teridontus nakamurai and Cordylodus proavus are described in detail. Tubular dentine and atubular (parallel- and wavy-lamellar) dentine are found in the basal bodies of the primitive euconodonts Proconodontus tenuiserratus and Proconodontus muelleri, respectively. The tubular dentine and spherulitic dentine are also recognized from the basal bodies of Granatodontus ani and Rotundoconus tricarinatus. Since the histological characteristics of the studied six species of euconodonts belonging to Proconodontus lineage and Teridontus lineage Sensu Miller (Univ Kansas Paleontol Contr, 1980, 99: 1?39) seems to be almost the same, euconodonts are proposed as possibly monophyletic herein.