Boreognathus pogorevichi, a remarkable new polychaete annelid from the lower Permian of the Pechora Basin, Russia

Abstract

The sclerotized jaw elements (scolecodonts) of polychaete annelids are rarely preserved as articulated jaw apparatuses. Here we describe a morphologically unusual, rather large, and symmetrical jaw apparatus, assigned to the new taxon Boreognathus pogorevichi gen. et sp. nov., from the Kungurian (lower Permian) of the Pechora Coal Basin, northern Cis-Urals, Russia. Whereas the specimen is mainly preserved as a three-dimensional external mould of the nearcomplete dorsal maxillary apparatus, some organic matter comprising the original jaw wall is also retained. The new taxon combines edentate, pincer-like first maxillae (MI) typical of the extant Labidognatha apparatus type with long slender carriers common in the Prionognatha type. Unlike the smooth MI, MII are consistently and prominently denticulated. The new genus represents a hitherto unknown type of polychaete jaw apparatus and is assigned to the Palaeozoic family Atraktoprionidae.

Jaw morphology and function in Drilonereis cf. filum (Oenonidae, Annelida)

“…This is probably due to the fact that all these species are small, interstitial forms (Paxton & Åkesson, 2007, 2010). A possible exception to this rule is the recently described fossil Boreognathus (Shcherbakov et al, 2022), which has large, strong and widely curved maxillae 1 and long and slender carriers, positioned in the same way as Mx1 in the Ophryotrocha species with K‐type maxillae.…”

“…Therefore, data on the fine structure and functional morphology of the jaws of modern Prionognatha—Oenonidae—are helpful for the interpretation of fossil materials which are often incomplete. The most difficult issue for a comparative analysis of modern and fossil jaws is the functional interpretation of jaw apparatus structure as a whole and in its individual parts (Sherbakov et al, 2022). In this regard, the work of Clemo & Dorgan (2017) is important, as it presents experimental data and observations on the jaw apparatus mechanics of the Labidognatha and Symmetrognatha types (Eunicida).…”

“…Thus, of the seven extant families of the order Eunicida, jaw fine structure is still unknown in Lumbrineridae, Hartmanniellidae, and Oenonidae. The latter family is of particular interest, since representatives of Oenonidae have a jaw apparatus of the prionognath type, which is characteristic of some fossil forms, namely Atraktoprionidae and Skalenoprionidae (Kielan‐Jaworowska, 1966; L. A. Parry et al, 2019; Sherbakov et al, 2022). Therefore, data on the fine structure and functional morphology of the jaws of modern Prionognatha—Oenonidae—are helpful for the interpretation of fossil materials which are often incomplete.…”

“…Scolecodonts, elements of the jaw apparatus of worms of the order Eunicida, have been known since the Paleozoic (Ehlers, 1868; Kielan‐Jaworowska, 1968; Kielan‐Yavorowska, 1966; Kozłowski, 1956; Pander, 1856; L. Parry et al, 2014; L. A. Parry et al, 2019). Naturally, there is great interest in the evolutionary interpretation of this data compared to the jaws of extant Eunicida, since this is the only group of marine annelids currently widely represented that also has extensive paleontological material (Corradini et al, 1974; Kielan‐Jaworowska, 1968; Kielan‐Yavorowska, 1966; Mierzejewski, 1984; Orensanz, 1990; L. Parry et al, 2014; L. A. Parry et al, 2019; Paxton, 2009; Shcherbakov et al, 2022; Szaniawski and Wrona, 1987; Tzetlin, 1980).…”

“…Boreognathus (Shcherbakov et al, 2022), which has large, strong and widely curved maxillae 1 and long and slender carriers, positioned in the same way as Mx1 in the Ophryotrocha species with K-type maxillae.…”