Yinostius major

Zhu, You-An, Zhu, Min & Wang, Jun-Qing, 2016, Redescription of Yinostius major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci, Zoological Journal of the Linnean Society 176 (4), pp. 806-834 : 809

YINOSTIUS MAJOR WANG & WANG, 1984

Holotype: Near-complete head and thoracic armour, slightly displaced but all plates occur on one slab ( IVPP V7142 , Fig. 2 ).

Locality and horizon: Wuding, Yunnan Province, China; Jiucheng Formation, Emsian, Lower Devonian.

Emended diagnosis: Medium to moderately large arthrodire, with the median dorsal plate having an estimated length of 16 cm. The skull roof shows typical heterostiid characters such as anteriorly tapered outline, anterodorsally positioned small orbits and posteriorly positioned posterolateral corners. The neurocranium resembles that of eubrachythoracids in the posteriorly positioned pineal foramen, long and narrow orbitotemporal region, laterally expanded supravagal process, and absence of subnasal shelf. The median dorsal plate is short and broad, with a length/breadth ratio of 0.52. The posterior carinal process of the median dorsal plate is highly developed. The rod-like anteri- or lateral and the anterior dorsolateral plates are completely fused to form a complex, with a spherical glenoid condyle. The dermal ornament consists of coarse tubercles.

Figures

Figure 2. Yinostius major. Holotype IVPP V7142. Scale bar = 5 cm.