The Cleveland Shale fauna represents a unique view of the time after a major Devonian extinction event

(Frasnian–Famenian) with the recovery of arthrodires (Placodermi) best represented by this most specious

North American fauna. This time was followed by an additional event (Hangenberg Biocrisis) leading to the

extinction of arthrodires (and all other placoderms). An understanding of the diversity and interrelationships of

North American arthrodires can aid our understanding of this critical time in vertebrate evolution. A new aspinothoracid

arthrodire Hlavinichthys jacksoni gen. et sp. nov. is described from the Late Devonian of northern

Ohio, U.S.A., which adds to our knowledge of this group. It provides a point of comparison to other members

of the fauna whose interrelationships are poorly known. A phylogenetic analysis supports an assignment of

Hlavinichthys jacksoni gen. et sp. nov. among the aspinothoracid arthrodires. This work has drawn attention to

the continued need for descriptive and phylogenetic analyses of this unique fauna. Decades old species descriptions

need revision along with preparation and description of new taxa. The work on Hlavinichthys jacksoni

gen. et sp. nov. here is one step in that process.

Ophiuroids from the Upper Jurassic marine deposits (upper Oxfordian–lower Kimmeridgian) of southern and north-western Poland have been studied in two sections: Zalas quarry in the Kraków-Częstochowa Upland in southern Poland and Wapienno/Bielawy quarries in the Kuyavia region of north-western Poland. Described herein are nine taxa belonging to five genera (one new to science): Alternacantha Thuy and Meyer, 2013; Dermocoma Hess, 1964; Ophiobartia Loba gen. nov.; Ophioderma Müller and Troschel, 1840; Ophiotreta Verrill, 1899, and three families: Ophiacanthidae and Ophiodermatidae (both of Ljungman, 1867), and Ophiotomidae Paterson, 1985. Only a few representatives of some of these taxa have previously been reported from the Jurassic of Poland. One species, Ophiobartia radwanskii Loba, is established as new. The ophiuroid material recognized from both Polish localities is close to those described from Western Europe at family or even genus level. Both studied ophiuroid assemblages from Zalas and Wapienno/Bielawy show similarities, being dominated by the cosmopolitan species Ophioderma spectabile Hess, 1966, and by different species of Dermocoma. The recognized ophiuroid assemblages represent a rather shallow-water environment.