Atraktoprionidae Kielan-Jaworowska, 1966

Szaniawski, Hubert & Drygant, Daniel, 2014, Early Devonian scolecodonts from Podolia, Ukraine, Acta Palaeontologica Polonica 59 (4), pp. 967-983 : 978

Family Atraktoprionidae Kielan-Jaworowska, 1966 Genus Atraktoprion Kielan-Jaworowska, 1966

Type species: Atraktoprion cornutus Kielan-Jaworowska, 1962 , erratic boulder; Ordovician , Poland .

Remarks. —Isolated MI of this genus were in older literature usually assigned to Arabellites Hinde, 1879 . Sylvester

1959) designated A. hamatus Hinde, 1879 as the lectotype. However, the status of the genus has been discussed later in several publications (for the summary see Eriksson 2008). The latter author reviewed all preserved specimens assigned by Hinde (1879) to Arabellites and presented their modern illustrations. However, he reserved his judgment concerning the important problem of the relationship of Arabellites to Atraktoprion, Kielan-Jaworowska, 1962 explaining that it “will be discussed in detail elsewhere” ( Eriksson 2008: 629). The relationship problem is not easy to solve because the lectotype of Arabellites represents the left MI, which is very similar to the corresponding elements of three later established genera Atraktoprion Kielan Jaworowska, 1962 , Skalenoprion Kielan-Jaworowska, 1962 , and Leptoprion Kielan-Jaworowska, 1966 , while some other elements of the three genera are significantly different. Because of this Kielan-Jaworowska (1966) assigned the genera to three different families. This means, that after morphology only, it is difficult to determine their isolated left MI even to the family level. Because of that, in our opinion, all the “species” of Arabellites based on singular specimens of the left MI have to remain undetermined in the sense of biological systematics, as long as we do not know other elements of apparatuses to which they belonged. In the case of their co-occurrence with other elements the numerical data can help to solve the problem.

Hinde (1879: 377) establishing the genus Arabellites stated: “I propose to include in this genus jaws of widely different forms which have a general resemblance to those of the existing genus Arabella Grube ”. The idea was generally correct because the author did not treat each element of jaw apparatus as a separate taxon, as many later authors did. However, in that time he did not know that many fossil polycheates possessed a very different structure of jaw apparatuses from modern forms. Right MI of Paleozoic apparatuses similar in shape to Recent Arabella Grube, 1850 possess usually either bight or basal plate, what means they are significantly different from the MI of Recent Arabella . Therefore it is understandable that most of the species of Arabellites based by Hinde (1879, 1880, 1882) on the MI are left jaws. Two of the three species based by the author on the right MI, the Arabellites extensus Hinde, 1880 and Arabellites spicatus Hinde, 1880 possess bight characteristic for MI of Atraktoprionidae , while the third species Arabellites fastigatus Hinde, 1882 possess basal ridge and shape characteristic for the right MI of Skalenoprionidae .