Reconstruction of the multielement apparatus of the earliest Triassic conodont, Hindeodus parvus, using synchrotron radiation X-ray micro-tomography

Abstract

Earliest Triassic natural conodont assemblages preserved as impressions on bedding planes occur in a claystone of the Hashikadani Formation, which is part of the Mino Terrane, a Jurassic accretionary complex in Japan. In this study, the apparatus of Hindeodus parvus (Kozur and Pjatakova, 1976) is reconstructed using synchrotron radiation micro-tomography (SR - μCT). This species has six kinds of elements disposed in 15 positions forming the conodont apparatus. Carminiscaphate, angulate, and makellate forms are settled in pairs in the P1, P2, and M positions, respectively. The single alate element is correlated with the S0 position. The S array is a cluster of eight ramiforms, subdivided into two inner pairs of digyrate S1-2 and two outer pairs of bipennate S3-4 elements. The reconstruction is similar to a well-known ozarkodinid apparatus model. In addition, the μCT images show that the 'anterior' and 'posterior' processes of the S1-2 elements faced the caudal and rostral ends of the living conodont body, respectively.