Nikolay Zverkov

• PhD
• Researcher at Russian Academy of Sciences

Pliosaurid marine reptiles played important roles in marine food chains from the Middle Jurassic to the middle Cretaceous, frequently as apex predators. The evolution of pliosaurids during the later parts of the Early Cretaceous has recently been illuminated by discoveries from Russia (Hauterivian) and Colombia (Barremian). However, knowledge of pl...

Recent study of ophthalmosaurid ichthyosaurs has brought us a number of new taxa; however, the validity of several ophthalmosaurid taxa from the Volgian (Tithonian) of European Russia still remains unclear, complicating comparisons and in some cases affecting taxonomic decisions about new contributions. A revision of the type series of all three sp...

The ichthyosaur genus Arthropterygius Maxwell, 2010 is considered as rare and poorly known. However, considering the existing uncertainty regarding its position in respect to ophthalmosaurid subfamilies in recent phylogenies, it is among the key taxa for understanding the evolution of derived Late Jurassic and Early Cretaceous ichthyosaurs. Recentl...

The Late Jurassic ichthyosaur Nannopterygius is among the poorest known, with the only skeleton, NHMUK PV 46497, on display in the Natural History Museum, London and, therefore, difficult to access. This holotype specimen is here reassessed. The newly obtained data have enabled the identification of several additional specimens of Nannopterygius in...

The first ichthyosaurian specimens discovered from the Upper Triassic of the Russian Arctic (Kotelny Island, New Siberian Islands) are described herein. They include the remains of large-to small-bodied ichthyosaurians originating from six stratigraphic levels spanning the lower Carnian to middle Norian. The material is mostly represented by isolat...

Most polycotylid plesiosaurians have isodont dentition with relatively small and slender conical teeth. However, large and robust caniniform teeth are known for some of their basal late Albian and early Cenomanian representatives, implying greater ecological diversity early in the evolutionary history of the clade. Here we report the first evidence...

Since the discovery of the holotype of Polycotylus sopozkoi in the Southern Urals, several skeletons referable to Polycotylus were collected from the upper Santonian – lower Campanian bone bed at its type locality (Izhberda quarry, Orenburg Region, Russia). Here we describe these new specimens, which together with the holotype constitute an ontogen...

Изучение новых находок мозазаврид из Ижбердинского местонахождения (Южный Урал, Оренбург- ская обл.) позволило впервые установить для верхнего мела Оренбуржья присутствие мозазавров из подсемейств Mosasaurinae, Tylosaurinae и Plioplatecarpinae, в т.ч. представителей родов Mosasaurus, Prognathodon и Clidastes, известных из верхнего мела Северной Аме...

Plesiosaurs of the family Elasmosauridae are widely known for their long necks with a record number of vertebrae. Currently, many genera and species of elasmosaurids are known: from small to gigantic, from super-­long-­necked to secondarily short­necked. Elasmosaurid remains have been described from all regions of the world and are often found in C...

The history of study of the Upper Jurassic Volgian Stage and Lower Cretaceous Ryazanian Stage, their geographic occurrence, and use in world practice, subdivision, and correlation are considered. The data on the occurrence of various groups of macro-and microfossils (ammonites, bivalves, radiolarians, dino-cysts, and marine vertebrates) in the Volg...

Polycotylids are Cretaceous plesiosaurs with a relatively short neck and an elongated snout. For a long time, they were studied mainly based on the fossils from North America. Numerous finds of polycotylids from Russia shed light on their diversity in Late Cretaceous epicontinental seas of Europe. Russian finds demonstrate that some representatives...

Protosphyraena is one of the most widespread Cretaceous actinopterygian genera, with numerous species described primarily from the Upper Cretaceous of North America and Western Europe. However, most of the species are known from fragmentary and anatomically non-overlapping material, making the alpha taxonomy of this genus extremely problematic. Her...

The study of new finds of mosasaurids from the Izhberda locality (Southern Urals, Orenburg Region) has made it possible to record for the first time the presence of mosasaurs from the subfamilies Mosasaurinae, Tylosaurinae, and Plioplatecarpinae from the Upper Cretaceous of the Orenburg Region, including representatives of the genera Mosasaurus, Pr...

The study of the remains of marine reptiles from the Callovian (Middle Jurassic) deposits of European Russia highlights the similarity of the herpetofauna of the Middle Russian Sea with the famous fauna of the Oxford Clay Formation of England. The Middle Russian Sea was inhabited by the pliosaurids Liopleurodon and Simolestes ; the cryptoclidid ple...

The history of the study of the Volgian Stage of the Upper Jurassic and Ryazanian Stage of the Lower Cretaceous, their geographical distribution and use in the world practice, subdivision and correlation are considered. The data on the distribution of different groups of macro- and microfossils (ammonites, bivalves, radiolarians, dinocysts, and mar...

Our knowledge of marine reptiles of the Callovian age (Middle Jurassic) is majorly based on the collections from the Oxford Clay Formation of England, which yielded a diverse marine reptile fauna of plesiosaurians, ichthyosaurians, and thalattosuchians. However, outside of Western Europe, marine reptile remains of this age are poorly known. Here, w...

A dorsal vertebra of an ichthyosaur is described from the fluvial deposits of the Kama River (Votkinsk District, Udmurt Republic, Russia). This vertebra belonged to a fairly large ichthyosaur about 5-6 m long, apparently one of the largest ichthyosaurs known from European Russia. The find is redeposited, and it is problematic to establish its exact...

Polycotylids are among the most common plesiosaurians of the Late Cretaceous, however, in Eurasia their findings are rare and fragmentary. In 2016, a partial polycotylid skeleton from the Upper Cretaceous of the Izhberda quarry in the Southern Urals region was described by Efimov et al. as a new species, Polycotylus sopozkoi. Here we revise this ho...

We provide new data on stratigraphy, fossil molluscs and marine reptiles from the Middle and Upper Jurassic outcrops in the Ukhta area (Izhma and Aiyuva rivers). The Bajocian, Bathonian, Callovian and Oxfordian–Volgian key sections are described in detail and discussed. We also refine the characteristics of the Middle–Upper Jurassic Formations and...

В юрских и нижнемеловых отложениях европейской части России найдены ископаемые остатки крокодиломорф талаттозухий (Thalattosuchia). Некоторые из них удалось отнести к родам, известным из других регионов мира. Расчет палеоширот для местонахождений показал, что находки из России расположены преимущественно между 44° и 50° северной широты, следователь...

From the Middle Jurassic to the Early Cretaceous, metriorhynchid crocodylomorphs inhabited marine ecosystems across the European archipelago. Unfortunately, European metriorhynchids are only well known from Germany, France, and the UK, with the Eastern European fossil record being especially poor. This hinders our understanding of metriorhynchid bi...

Pliosaurid plesiosaurians are iconic marine reptiles that regulated marine trophic chains from the Middle Jurassic to the early Late Cretaceous. However, their evolution during the Cretaceous remains poorly documented. Recent discoveries from the Hauterivian–Aptian interval suggest that the radiation of brachaucheniine pliosaurids produced a wide d...

Here we describe the first findings of reptile remains in the Upper Cretaceous marine strata of Siberia, which represent the northernmost occurrences of plesiosaurians, ?mosasaurids and turtles in the Cretaceous of Eurasia (66-72° N palaeolatitudes). The specimens come from the upper Cenomanian, Turonian and Coniacian of the Pyasina River basin, Sa...

Many ichthyosaur researchers consider the Late Jurassic genera Grendelius and Brachypterygius synonymous, but do not take into account species of the genus Otschevia (synonym of Grendelius) described from Russia, which is partly due to their brief initial descriptions. We provide a detailed description and photographs of the bones of Grendelius pse...

Revised definitions of the families Ophthalmosauridae Baur, 1887 and Platypterygiidae Bardet, 1995 are provided. These families are combined into a group Ophthalmosauria Motani, 1999. The families Undorosauridae Efimov, 1999 and Brachypterygiidae Cortes, Maxwell et Larsson 2021 are junior synonyms of Platypterygiidae Bardet, 1995. Phylogenetic entr...

Here we report the first ichthyosaurian finds from the Valanginian and Hauterivian of Austria. Based on their tooth morphology, they represent two distinct taxa with probably different feeding ecologies. The Valanginian specimen is a small tooth with a small crown and bulbous root, similar to teeth of Nannopterygius and Sisteronia - it likely was a...

Plesiosaurian marine reptiles evolved a wide range of body shapes during the Jurassic and Cretaceous, including long-necked forms. Many Late Cretaceous members of the clade Elasmosauridae epitomized this part of the plesiosaurian morphological spectrum by evolving extremely long necks through somitogenesis (resulting in an increase in the number of...

A new specimen of the Early Cretaceous pterodactyloid pterosaur Istiodactylus latidens is described. This specimen in the Moscow Vernadsky State Geological Museum represents the associated anterior ends of the rostrum and mandibular symphysis but lacks collection data. It likely comes from the Barremian-Aptian Vectis Formation of southern England b...

Marine reptile occurrences are rare in the Lower Jurassic Series outside of Europe. Here we describe diverse marine reptile faunas from the Lower Jurassic Series (Pliensbachian and Toarcian stages, including the Toarcian–Aalenian boundary interval) of Eastern Siberia. The taxonomic composition of Toarcian marine reptile assemblages of Siberia highl...

An abundant collection of bivalves, belonging to the stratigraphically important genus Retroceramus, has been described for the first time from the Bajocian‒Bathonian beds of the Timan-Pechora region, exposing along the Izhma River and its right tributary, the Dreshchanka River. Totally 7 taxa were found, among which 4 were identified to a species...

Recent progress in the study of Cretaceous ichthyosaurians resulted in significant reevaluation of their diversity. However, there are still problematic mid-Cretaceous ichthyosaurian taxa, among which are ‘Ophthalmosaurus’ cantabrigiensis Lydekker, 1888 from the upper Albian – lower Cenomanian of England, Maiaspondylus lindoei Maxwell & Caldwell, 2...

Plesiosaur specimens from the Upper Jurassic of European Russia are mainly referable to the genus Colymbosaurus Seeley, 1874, based on elongated propodials with extensive posterodistal expansion, and relatively short mid-cervical vertebrae. However, a historical specimen described by Bogolubov (1911) and subsequently revised as Plesiosauria indet....

The first pliosaurid finding in Austria is described from a Lower Cretaceous (Hauterivian) pelagic to hemipelagic limestone succession of the Northern Calcareous Alps (Bajuvaric Langbath Zone). The isolated tooth crown originates from the upper Hauterivian Balearites balearis Zone (Balearites angulicostatus Subzone). The finding sheds light on the...

All current data on the Jurassic and Cretaceous climates of Siberia based on isotope, paleontological, and lithological proxies are summarized. The late Pliensbachian cooling episode, early Toarcian warming, promptly replaced by long-term Middle Jurassic cooling at the end of the Toarcian, and a long-term warm interval in the Late Jurassic are clea...

Recent study of ophthalmosaurid ichthyosaurs has brought us a number of new taxa, however, the validity of several ophthalmosaurid taxa from the Volgian (Tithonian) of European Russia still remains unclear, complicating the comparisons and in some cases affecting taxonomic decisions of new contributions. A revision of the type series of all three s...

A detailed description of the section of the Middle Jurassic terrigenous deposits exposed on the Yarenga River, Arkhangelsk Region, is provided. The section represents a new locality of fossil remains of Jurassic marine reptiles. Among them, the postcranial elements of the plesiosaur Muraenosaurus dominate. Pliosaur and ichthyosaur finds, each repr...

Here we describe plesiosaur remains from Glebovo section, Yaroslavl Region. Although the specimens were found non in situ they are likely Early Cretaceous, Valanginian, in age. One cervical centrum is referable to Elasmosauridae – this is the first find of an elasmosaurid plesiosaur in the Valanginian of Russia.

Pliosaurid plesiosaurians played important roles in marine food chains from the Middle Jurassic to the mid Cretaceous, frequently as apex predators. All hitherto described pliosaurid species of the Kimmeridgian to the Hauterivian possess trihedral and subtrihedral teeth with a smooth labial surface, while Aptian–Turonian pliosaurids have exclusivel...

An incomplete skeleton of the ichthyosaur Ophthalmosaurus icenicus Seeley, 1874 excavated in the Oxfordian-Kimmeridgian beds south of the town of Syzran (Samara Region) is described. Members of the genus Ophthalmosaurus are characterized by a unique combination of characters, most of which are well-pronounced in the specimen described here: the ext...

Описан неполный скелет ихтиозавра Ophthalmosaurus icenicus Seeley, 1874, обнаруженный в оксфордско-кимериджских отложениях южнее г. Сызрани (Самарская область). Представители рода Ophthalmosaurus характеризуются уникальной комбинацией признаков скелета, бóльшая часть из которых выражена у описываемого экземпляра: basioccipitale с редуцированной, но...

Here we describe incomplete plesiosaur skeleton from the Upper Santonian of Saratov Region (Russia), referable to Polycotylidae Williston, 1908. Hitherto remains of polycotylids from Saratov Region were known only from the Cenomanian, Campanian and Maastrichtian deposits. Polycotylid skeleton was found earlier in the Santonian deposits of Penza reg...

Marine reptile remains from the Jurassic of Moscow area were at first described in the year 1845, since then considerable materials from the Callovian, Oxfordian and Volgian (Tithonian) strata were accumulated. Here we review all available Jurassic marine reptile materials from Moscow area stored in museums and private collections. Callovian marine...

Here we report the first find of marine reptile tooth crown from the Upper Jurassic (Middle to Upper Oxfordian) of Crimean Mountains near Yalta. The crow is slender and circular in cross section; it is ornamented by fine longitudinal ridges by its entire circumference. This crown likely belongs to a plesiosaur, however, it also shows similarities t...

Plesiosaurs were the longest-surviving group of secondarily marine tetrapods, comparable in diversity to today’s cetaceans. During their long evolutionary history, which spanned the Jurassic and the Cretaceous (201 to 66 Ma), plesiosaurs repeatedly evolved long- and short-necked body plans [1,2]. Despite this postcranial plasticity, short-necked pl...

Zverkov, N.G., Averianov, A.O. & Popov E.V., April 2017. Basicranium of an elasmosaurid plesiosaur from the Campanian of European Russia. Alcheringa March. ISSN 0311-5518 The braincase of elasmosaurid plesiosaurs is poorly known. Here, we describe the exceptionally well-preserved elasmosaurid basicranium from the Rybushka Formation (lower Campanian...

The limbs of marine reptiles lack some function and characteristics essential for most amniotes: they do no more support body weight in terrestrial conditions but are modified into fins to steer or stabilize underwater motion, and into flippers , primary propulsive organs. Thereby their structure was partially reorganized in order to serve new func...

The braincase of elasmosaurid plesiosaurs is poorly known despite numerous relatively complete and well-studied skeletons. Thereby a new find of an elasmosaurid basicranium from the Rybushka Formation (mid-Campanian) of Saratov Region, Russia, is of great interest. The specimen, attributed to an elasmosaurid plesiosaur, possess an elongated plate-l...

Until recently, Tholodus, a rare ichthyosaur with spherical tooth crowns of the pressing–crushing type, has only been known from the Middle Triassic (Anisian) beds of Western Europe. A record of Tholodus remains in the Karazin Formation (Middle Anisian) of southern Primorye (Russian Far East) significantly expands the range of these reptiles.

Tholodus – редкий ихтиозавр со сферическими коронками зубов давяще-дробящего типа, известный до недавнего времени лишь из среднетриасовых (анизийских) отложений Западной Европы. Находка остатков толодуса в отложениях каразинской свиты (средний анизий) Южного Приморья значительно расширяет известный ареал этих рептилий.

The Upper Jurassic ichthyosaurs, characterized by the intermedium/humeral contact are known from several localities in Europe and North America. However, they are often described either briefly, or based on fragmentary material, resulting in a taxonomic tangle in most overviews. Grendelius McGowan, 1976 was previously synonymized with Brachypterygi...

During the Middle and Late Jurassic, pliosaurid plesiosaursevolved gigantic body size and a series of craniodental adaptations that have been linked to the occupation of an apex predator niche. Cretaceous pliosaurids (i.e. Brachaucheninae) depart from this morphology, being slightly smaller and lacking the macrophagous adaptations seen in earlier f...

Supplementary material. Includes: pictures of a bivalve associated with YKM 68249/1-10, stratigraphic age data for all taxon incorporated in the phylogeny, revised phylogenetic coding for Anguanax zignoi, additional figures of strict consensus topologies, detailed results from the ancestral state reconstruction and R scripts. -Nexus files. With cha...

A jaw fragment of the rare ichthyosaur Tholodus is found for the first time in the Middle Triassic deposits of the Karazin Formation (South Primorye, Russian Far East). An analysis of the cephalopod systematics (Acrochordiceras kiparisovae Zharnikova, A. korobkovi Zharnikova, Acrochordiceras pacificum (Zharnikova), Stenopopanoceras? russkiense sp....

Here we describe a specimen from the Lower Callovian of Kostroma region, referable to the short‐snouted pliosaurian genus Simolestes Andrews, 1909. This finding expands geographic distribution of the genus Simolestes, and deepens our understanding of the Callovian herpetofauna of the Russian Sea, which was apparently similar to that of Western Euro...

For the first time a specimen referred to Pliosaurus is described from the Lower Cretaceous (Lower Valanginian), represented by a single tooth from Mount Sheludivaya in Crimea. This specimen demonstrates that two pliosaurian lineages crossed the Jurassic – Cretaceous boundary: the typically Cretaceous subfamily Brachaucheninae Benson et Druckenmill...

Here we gave a brief description of an ichthyosaurian remains from the Lower Valanginian of the European Russia (Kirov region) referable to the family Ophthalmosauridae Baur, 1887. The record of ichthyosaurs from the Berriasian–Barremian interval is extremely limited so even fragmental remains are of great interest. This finding confirms the assump...

During the Late Jurassic, important palaeogeographic events occurred in Eurasia, North America and Gondwana. Continental rift, subduction and orogeny produced different levels of marine inundation of terrestrial systems, with rising sea level. Shallow epicontinental seaways started to separate North America from Eurasia, Gondwana, and also between...

Rhomaleosaurid plesiosaurians were a common and ecologically significant component of Early Jurassic marine faunas, primarily as large-bodied predators. They declined in abundance and made their last fossil appearance in the Middle Jurassic. However, the geographic pattern of rhomaleosaurid extinction has thus far been obscured by spatial bias in t...

An ichthyosaurian skeletal remains assigned to the genera Arthropterygius and Ophthalmosaurus are described from the Volgian deposits of the Komi Republic and Nenets Autonomous Region (Okrug) (Russia). These specimens along with findings from Svalbard provide an opportunity to draw some preliminary conclusions on the distribution of ichthyosaurs du...

A new species of ichthyosaur genus Undorosaurus from the Volgian stage of Moscow is described based on an incomplete forelimb. It differs from congeners basically in the form and position of pisiforme. With the application of cladistic method the phylogenetic position of two genera Undorosaurus and Paraophthalmosaurus in the system of Ichthyosaurid...

Tholodus is rare ichthyosaur with durophagous dentition, until recently known only from the Anisian deposits of Western Europe. Finding of Tholodus remains in the Anisian deposits (Karazinskaya suite formation) of Primorsky Kray significantly expands our understanding of the area of distribution of these reptiles and confirms previously suggested a...

Дан краткий обзор истории изучения, систематики и образа жизни ихтиозавров — необычных морских рептилий мезозоя. // The brief review of history of studying, systematics and habitats of ichthyosaurs, uncommon marine reptiles of Mesozoic is given.