Annales Societatis Geologorum Poloniae (2020), vol. 90: 75 – 93 doi: https://doi.org/10.14241/asgp.2020.04 A NEW MIDDLE DEVONIAN (GIVETIAN) PSAMMOSTEID (VERTEBRATA: HETEROSTRACI) FROM POLAND Marek DEC Institute of Palaeobiology, Polish Academy of Sciences, Twarda 51/55, 00-818 Warszawa, Poland; e-mail:
[email protected] Dec, M., 2020. A new Middle Devonian (Givetian) psammosteid (Vertebrata: Heterostraci) from Poland. Annales Societatis Geologorum Poloniae, 90: 75 – 93. Abstract: A new genus and species of psammosteid heterostracan, Psarkosteus mediocris gen. et sp. nov., is de- scribed from the Middle Devonian (Givetian) of the Skały Formation, the Holy Cross Mountains, Poland. The dor- sal plate of Psarkosteus is constricted in its anterior part and the postorbital plate is long and narrow. Both features, along with the morphology and variety of tubercles, distinguish it from other representatives of the group. Most distinctive are big, teardrop-shaped tubercles, each with a flat or slightly concave surface and with its tip directed posteriorly, and a crenulated base, located along the branchial plates. The lateral line system in Psarkosteus is similar to that of Drepanaspis gemuendenensis and confirms earlier reconstructions. Key words: Pteraspidomorphi, Heterostraci, Psammosteidae, Middle Devonian, Holy Cross Mountains. Manuscript received 19 February, 2020 accepted 1 June 2020 INTRODUCTION The fossil record of the Heterostraci is poor in Poland, 2017; Glinskiy, 2018). The main problem is concerned although fossils are known from Upper Silurian, Lower with their relationships within the Pteraspidiformes. The and Middle Devonian deposits. From a core sample of the Psammosteidae were supposed to be (1) a sister group to the Upper Silurian (Přidoli) succession in Mielnik a represen- pteraspids s.l., that is Protopteraspididae + Pteraspididae s.l.