Mironenko A., Giusberti L., Serafini G., Zorzin R. & Bannikov A.F. (2024) The first Cenozoic octopod: a Lower Eocene record from Bolca, northeastern Italy. Rivista Italiana di paleontologia e stratigrafia , 130(3), 603-612.

To date, soft-tissue remains of extinct incirrate octopods have been described exclusively from Upper Cretaceous deposits. Here, three specimens of an incirrate octopodid with well-preserved soft tissue imprints are described for the frst time from Paleogene strata. This material originates from the upper Ypresian (lower Eocene) fsh-bearing levels of the Bolca Konservat-Lagerstätte in the Pesciara of Bolca in north-eastern Italy. Previously, these specimens had tentatively been interpreted as teuthids. Based on a detailed study of their anatomical structure, a new genus and species of octopodid, Bolcaoctopus pesciaraensis, belonging to the extant family Octopodidae, are here erected. Bolcaoctopus gen. nov. may be distinguished from the Late Cretaceous genus Styletoctopus by the presence of long and thin arms and an elongated body shape with a narrowed apical end and covered by longitudinal wrinkles. Although fnds of fossil octopuses in the Bolca Konservat-Lagerstätte remain extremely rare, it is worth noting that Cenozoic marine vertebrate localities constitute an important potential source of additional fnds of coleoid cephalopods, the study of which may shed light on a poorly understood period in the evolutionary history of these molluscs.

Vinn, O., Mironenko, A.A., and Wilson, M.A. (2024) New parasitic organisms in a productid brachiopod Eomarginifera lobata from the lower Carboniferous of the Moscow Basin, Russia. Acta Palaeontologica Polonica , 69 (3), 403-410

Bioclaustrations are among the best ways that parasitic associations are preserved. A new bioclaustration, Haplorygma productidophilia csp. nov., is here described from the ventral interior of the Carboniferous productid brachiopod Eomarginifera lobata. The location and morphology of the structures in the ventral valve differ from the structure in the dorsal valve, suggesting that two different organisms infested the shells of Eomarginifera lobata. It is possible that whether it was ventral or dorsal valve was an important selection criterion for the infesting organisms, which were likely parasites. The proportion of infested productids was low in the population (5.8%). This low infestation rate could indicate that productids had effective methods for resisting parasites, or that the parasites were ineffective in spreading through the brachiopod population.

Mironenko Aleksandr, Smurova Irina (2024) Cameral membranes in the phragmocones of Jurassic ammonites . PALAIOS, 39(5), 145-160.

A complex system of three-dimensional cameral membranes is known from the phragmocones of several ammonoid genera—both Paleozoic and Mesozoic. The origin and functions of these membranes remain mysterious, and their study is complicated by the absence of identical structures in modern cephalopods. Current hypotheses about the origin of cameral membranes and other organic structures of the phragmocone are mainly based on the study of Paleozoic, Triassic, and Cretaceous ammonoids. This paper examines the membranes of Subboreal Jurassic ammonites. The spatial arrangement and complexity of these membranes differ from those described earlier. It was previously assumed that three-dimensional membranes only appeared late in ammonoid ontogeny, at the end of the neanic stage. However, in the ammonites studied herein, such membranes are present starting from the second phragmocone chamber. In addition to membranes, we report other initially organic phragmocone structures of Jurassic ammonites: pseudosutures and drag lines. The discovery of a unique structure in the last phragmocone chamber of one specimen, which likely represents a fossilized set of pseudosepta, has led to a new hypothesis, that can explain the formation of all types of membranes and other initially organic phragmocone structures. According to this idea, all types of cameral sheets despite their different shapes, were formed during merging and subsequent dehydration of organic pseudosepta. Pseudosutures and drag lines are imprints of the pseudosepta margins.

Mironenko, A., Rogov, M., Ippolitov, A., Smurova, I., & Zakharov, V. (2024) Ammonoid and coleoid jaws from the Upper Cretaceous of northern Siberia (Nizhnyaya Agapa River sections). Cretaceous Research, 161, 105918.

The jaws of cephalopods, ammonites and especially coleoids, are rarely met in fossil state. The localities with diversified jaws, belonging to various groups of fossil cephalopods are even less common. We describe a diversified complex of cephalopod jaws from the upper Cenomanianemiddle Turonian of Northern Siberia, which include the upper and lower jaws of Placenticeras ammonites (the oldest placenticeratid jaws known to date) and large-sized jaws of octobrachian coleoids. Although the lower jaws of Placenticeras belong to the aptychus type of ammonoid jaw apparatuses, they are characterized by the thickening of an inner organic layer in their anterior part, with a shape resembling a calcified conchorhynch known in the anterior portion of the lower jaws of Mesozoic nautilids and lytoceratid and phylloceratid ammonoids. The presence a conchorhynch-like structure supports the assumption that the feeding function in placenticeratid lower jaws most likely prevailed over the protective one. The upper jaws of Placenticeras show structure, typical for the jaws of aptychophoran ammonites: an inner lamella, divided into two wings, and a pointed outer lamella. Large-sized upper jaws of octobrachian coleoids demonstrate close affinities with the jaws of Octopoda suggesting that they could have belonged to representatives of this order, probably to large-sized gladius-bearing teudopseins. Judging by the jaws' size, both ammonites and octobrachians, which inhabited the marine basin in the Northern Siberia, were characterized by large body size. The cephalopod assemblage remained unchanged throughout the end of the Cenomanian and the first half of the Turonian.

Mitta Vasiliy, Mironenko Aleksandr (2024) An exceptionally large upper jaw of Lytoceratoidea from the Upper Bajocian (Middle Jurassic) of the Northern Caucasus. Paleontological Journal, 58(4), 426-433.

A large-sized upper jaw of an ammonite from the Niortense Zone of the Upper Bajocian of the Kuban basin (Karachay-Cherkessia) is described. In its anterior part a pointed calcified structure (rhyncholite) is located. Judging by its shape and size, the upper jaw belonged to a species of the genus Lytoceras (family Lytoceratidae), the lower jaw of which was already described from the same area immediately below in the section. The presence of a rhyncholite allows us to attribute the new finding to the rhynchaptychus type of ammonoid jaws. This is the earliest known complete jaw of this type and, to date, the only known upper jaw of Lytoceratina. Probably, calcification of the anterior part of the jaw apparatus of ammonoids of the suborders Lytoceratina and Phylloceratina was a normal process occurring as the mollusk matured.

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