My name is Aleksandr Mironenko, I am a paleontologist and paleobiologist. I have been interested in nature and fossils since my childhood. Although for most kids the dinosaurs are the most popular ancient creatures, I always have been more interested in invertebrate fossils such as fossilized seashells. The first fossil seashells for my collection (they were Devonian brachiopods) I found in gravel on the roads of Moscow, my hometown, when I was about 10 years old.
Nevertheless, my way to the paleontological science was long and winding and for a long time paleontology was only my hobby. I graduated from university in 2003 with a BA and specialist degree (analogue of a masters degree in the old Russian system) in environmental sciences. In the first year in the university, the training included a short course of geology with elements of paleontology and with excursions to various fossil localities. After I found out where well-preserved fossils can be collected, I became an active fossil collector and amateur paleontologist. A large number of easily accessible localities of the Jurassic age in the vicinity of Moscow and in the city itself influenced the choice of my main object of collecting and later of my research - ammonites. A few years later, while still an amateur paleontologist, I completed a bachelor's degree in computer sciences. For several years I worked as a web-programmer and in my spare time made two paleontological web-sites: Paleometro.ru, dedicated to fossils which are located in the wall decorating material of the stations of Moscow Metro, and Ammonit.ru – mix of a forum, social network and a fossil record database for amateurs and specialists in the paleontology.
Collecting ammonites and fossil nautiloids led me to reading paleontological literature - I tried to read all the articles and books on cephalopod paleobiology (especially on ammonoid paleobiology) which I could find. Thanks to the Internet and help of my friends - professional paleontologists, I had access to both classic books and modern journal articles and gradually realized that among ammonites in my collection there are some paleobiological features that had not been described in literature. Since 2014 I began to describe these findings in my own publications. Thus I went from being a reader to a writer of scientific articles and became a self-educated paleontologist.
Currently, I work at the Geological Institute of the Russian Academy of Sciences (ginras.ru) as a researcher. My professional interests concentrate mainly on Jurassic and Cretaceous ammonoids, but cover all fossil cephalopods, including various Paleozoic nautiloids. I am interested in various aspects of the evolution, paleoecology, and paleobiology of the fossil nautiloids and ammonoids: the structure and evolution of their jaw apparatus, muscular system, and siphuncle tissues, their growth, reproduction, sexual dimorphism, etc. I like to go and take part in excavations and to find cephalopod shells for future research. I alternate between the writing of scientific papers and popular publications and maintains my websites.
Jaws of ammonites which inhabited the Panboreal Superrealm during the Jurassic and Cretaceous are poorly known in comparison to those of Tethyan ammonoid faunas. This paucity may be explained by limited thickness, or even absence of an outer calcitic layer, in lower jaw elements (aptychi) of Boreal ammonites. Here we describe, for the first time, the jaws (both lower and upper) of ammonites of the Boreal family Polyptychitidae, of Early Cretaceous (Valanginian) age. Polyptychitid lower jaws are of the aptychus type, but have an unusual pointed and convex shape. However, lower jaws of Late Jurassic ancestors of polyptychitids (Craspeditidae) as well as Middle Jurassic cardioceratids (Pseudocadoceras) have a near-identical shape, as do previously described aptychi of the Late Cretaceous genera Neogastroplites and Placenticeras (Hoplitoidea). The close resemblance of lower jaws of evolutionarily distant ammonites may be linked to a similar lifestyle, but more data are needed to substantiate this. Upper jaws of polyptychitid are closely similar to previously described upper jaws of Jurassic ammonites, which indicates the conservatism of this part of the jaw apparatus. Together with shells and jaws of the Valanginian ammonites described herein, jaws of coleoids (likely belemnites) as well as arm hooks (onychites) have been found.More >>>
Ammonoids – cephalopod molluscs with external shells that existed from the Early Devonian up to the end of the Cretaceous – had well-developed jaws. During ammonoid evolution, several different types of their jaw apparatus arose, the study of which is of undoubted interest since it allows researchers to draw conclusions about the feeding strategies of ammonoids and their position in trophic chains. However, there is a lack of findings relating to the evolution of ammonoid jaws during the Permian. Here we describe a collection of almost thirty of cephalopod jaws from the Divjinskian Formation (Artinskian Stage, Cisuralian, Lower Permian), from the Sverdlovsk region of Russia. Most likely, these jaws belong to goniatitid ammonoid Uraloceras, the most abundant cephalopod mollusc in the Divjinskian (Divya) Formation. Uraloceras lower jaws are typical ammonoid anaptychi which have a rounded, wide and convex shape with smooth or slightly ribbed surface. They have a large inner lamella with a trapezoidal platform in the central part. One of the jaws bears a possible bite trace of a predator or scavenger. The upper jaws, described here for the first time, are slightly smaller than the lower jaws, their shape is narrow and pointed. Originally, both jaws were completely organic without calcareous elements. The absence of sculpture, consisting of frequent ribs and growth lines, characteristic of the more ancient Carboniferous goniatitid jaws, makes the jaws of the Uraloceras closer to the structure of the jaw apparatus of Triassic ammonoids. Judging by the pointed shape of the tips of both jaws, Uraloceras were active predators.More >>>
?Holoconularia rossica sp. nov. is described from interstratified shale and siltstone beds in the Dashkovka Member of the Upper Mississippian (early Serpukhovian) Gurovo Formation in the Moscow Basin, Central Russia. The status of the genus Holoconularia, originally described from the Devonian of Germany, is discussed, and it is argued that at least one species previously assigned to it may belong in Paraconularia instead. Another species, P. mosquensis from the Middle Pennsylvanian of Central Russia, may be more closely related to ?H. rossica than to species in Paraconularia. Comparisons are also made with Conularia, Ctenoconularia, and Tasmanoconularia, three genera that are very similar to certain species in Holoconularia. The well-preserved periderm of ?H. rossica sp. nov. exhibits microscopic circular pores (micropores) and (in one specimen) malformed, cleft or scalloped ornamentation. The micropores in this and other conulariids appear to be primary anatomical features that may have housed an extremely slender, very short pillar of non-mineralized (organic) periderm connecting successive microlamellae composed predominantly of organic material. Cleft and scalloped features may represent healed injuries inflicted by predators, possibly nautiloids and/or gnathostomes.More >>>
A single, atypical conchorhynch (calcitic tip of a cephalopod lower jaw), recovered from the uppermost Meerssen Member (Maastricht Formation, upper Maastrichtian) at the former ENCI-HeidelbergCement Group quarry, south of Maastricht, is described as a new parataxon, Conchorhynchus illustris sp. nov. The specimen can be differentiated from all previous conchorhynch records on account of its large size, elongated shape and, in particular, of the structure of its apical part which is smooth and forwardly elongated. During the Late Cretaceous, conchorhynchs formed part of the jaw apparatus of nautilids and of two ammonoid suborders, Phylloceratina and Lytoceratina. Since conchorhynchs are most often found separated from jaws, establishing to which group of cephalopods their bearer belonged can be complicated. Here, for the first time, we propose a set of morphological criteria to differentiate clearly between nautiloid and ammonoid conchorhynchs. Although Conchorhynchus illustris sp. nov. is distinct from all currently known nautilid conchorhynchs, the sum of its morphological features is indicative of assignment to that cephalopod group. The upper portion of the Maastricht Formation in the Maastricht area (Nekum and Meerssen members) has yielded internal and external moulds of shells of the nautilid Eutrephoceras and the hercoglossid Cimomia. The new conchorhynch type described herein most likely belonged to one of these shell-based taxa. Judging from its unusual shape, the feeding strategy of its bearer must have differed from that of modern nautilids, in that it held and pierced prey rather than crushed sturdy shells.More >>>
Comments are provided on a published paper on Middle Jurassic Laevaptychus from central Mexico [C.EsquivelMacías, P.Zell, J.A.Moreno-Bedmar and K.Flores-Castro, Giant Middle Jurassic Bathonian) cf. Laevaptychus sp. of the Aztl´ an section, Hidalgo State, central Mexico, Journal of South American Earth Sciences, 110, 103302]. This article describes an interesting finding of large-sized ammonite lower jaws (aptychi referred to Laevaptychus paragenus), claimed as the largest Jurassic aptychi ever known. However, the age of these specimens was erroneously defined due to misidentification of an associated ammonite specimen as Bathonian Procerites. Although poorly preserved, this ammonite shows typical features of the Kimmeridgian genus Idoceras. The Kimmeridgian age of these occurrences is in agreement with findings of Laevaptychus, as this is one of few aptychi formal genera, which belongs to a single ammonite family (Aspidoceratidae). Aspidoceratids appeared in the late Callovian and during the evolution of this lineage maximum sizes of adult specimens and the relative whorl height gradually increased up to Kimmeridgian - Tithonian; only prior to their extinction in early Berriasian, aspidoceratids became uncommon and smaller in size. Laevaptychi are thick-valved aptychi, which have high preservation potential while compared with other aptychi of Jurassic ammonites and their host shells. Giant laevaptychi reported in previous publications (the largest of which reaches 35 cm in length) are briefly reviewed. In adult aspidoceratids the maximum length of aptychi is slightly less than the maximum whorl height. Thus, taking into account the size of the largest aspidoceratid ammonites (up to 85 cm in diameter), the estimated length of the largest laevaptychi can be expected to be ~35–40 cm, which is close to their known record.More >>>
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