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Making New Out of the Old: Recent Biological Advances on...
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Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles

A special issue of Diversity (ISSN 1424-2818). This special issue belongs to the section "Phylogeny and Evolution".

Deadline for manuscript submissions: closed (31 March 2024) | Viewed by 12604

Image courtesy of Benjamin Waterhouse Hawkins

Special Issue Editor

Dr. Nathalie Bardet

E-Mail Website
Guest Editor
Centre de Recherche en Paléontologie de Paris, UMR 7207 - CNRS, MNHN, SU, Muséum National d’Histoire Naturelle, CP 38 – 57 rue Cuvier, 75005 Paris, France
Interests: systematics; phylogeny; palaeobiogeography; palaeobiology; palaeoecology and science history of Late Cretaceous marine reptiles from the northern and southern margins of the Mediterranean Tethys

Special Issue Information

Dear Colleagues,

A secondary return to aquatic life is a major evolutionary phenomenon in vertebrate history. Although some pioneers returned to aquatic life by the end of the Paleozoic era, this phenomenon is best illustrated during the Mesozoic (with reptiles) and Cenozoic (with mammals) eras.

During the Mesozoic era, about ten clades of reptiles underwent a dramatic return to aquatic life; in doing so, they colonized most marine environments, exhibiting great systematic diversity and astonishing ecological disparity. Many were among the greatest marine predators of their time, and some, such as ichthyosaurs, plesiosaurs and mosasaurs, were iconic clades of large Mesozoic ‘gigantic saurians’ that mirrored terrestrial dinosaurs.

These marine reptiles illustrate a mosaic of morphological, physiological and ecological adaptations to an aquatic lifestyle, some of which are convergent with those found in Cenozoic marine mammals, and others completely unique.

This volume aims to present recent biological advances made through the discovery of exceptionally preserved specimens and/or the use of modern methods. As such, it will focus mainly (but not exclusively) on topics such as locomotion modes and sensory systems, physiology and metabolism, reproduction and predation modes, and soft tissues and colors.

Dr. Nathalie Bardet
Guest Editor

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Keywords

  • Mesozoic
  • marine reptiles
  • biology

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Published Papers (6 papers)

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Research

16 pages, 3588 KiB  
Article
First Virtual Reconstruction of a Mosasaurid Brain Endocast: Description and Comparison of the Endocast of Tethysaurus nopcsai with Those of Extant Squamates
by Rémi Allemand, Michael J. Polcyn, Alexandra Houssaye, Peggy Vincent, Camilo López-Aguirre and Nathalie Bardet
Diversity 2024, 16(9), 548; https://doi.org/10.3390/d16090548 - 5 Sep 2024
Viewed by 1170
Abstract
Paleoneurological studies of mosasaurids are few and limited to old partial reconstructions made from latex casts on Platecarpus and Clidastes. Here, the brain endocasts of three specimens of the early mosasaurid Tethysaurus nopcsai from the Turonian of Morocco are reconstructed for the [...] Read more.
Paleoneurological studies of mosasaurids are few and limited to old partial reconstructions made from latex casts on Platecarpus and Clidastes. Here, the brain endocasts of three specimens of the early mosasaurid Tethysaurus nopcsai from the Turonian of Morocco are reconstructed for the first time by using micro-computed tomography. Comparisons between Tethysaurus and the later Platecarpus and Clidastes show that distinct endocranial organizations have occurred within the clade through time, including differences in the flexure of the endocast and the size of the parietal eye. The physiological consequences of such variability remain unclear and further investigations are required to better interpret these variations. In addition, the endocast of Tethysaurus was compared to those of extant anguimorphs, iguanians, and snakes, using landmark-based geometric morphometrics. The results revealed that Tethysaurus exhibits a unique combination of endocranial features compared to extant toxicoferans. Contrary to previous statements, we find no strong resemblance in endocast morphology between Tethysaurus and varanids. Rather, the endocast of Tethysaurus shows some morphological similarities with each of the clades of anguimorphs, iguanians, and snakes. In this context, while a notable phylogenetic signal is observed in the variability of squamate endocasts, it is premature to establish any phylogenetic affinities between mosasaurids and extant squamates based solely on endocast morphologies. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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Figure 1

Figure 1
<p>Mosasaurid brain endocasts. Brain endocasts of <span class="html-italic">Clidastes propython</span> UCMP 34535 in dorsal view (<b>a</b>) and <span class="html-italic">Platecarpus</span> sp. UCMP 34781 in left lateral view (<b>b</b>), modified from Camp [<a href="#B28-diversity-16-00548" class="html-bibr">28</a>] (no scale bar available). (<b>c</b>–<b>h</b>) Brain endocasts of <span class="html-italic">Tethysaurus nopcsai</span> specimen SMU 76335 (<b>c</b>,<b>d</b>), SMU 75486 (<b>e</b>,<b>f</b>), and MNHN GOU 1 (<b>g</b>,<b>h</b>) in dorsal (<b>c</b>,<b>e</b>,<b>g</b>) and left lateral (<b>d</b>,<b>f</b>,<b>h</b>) views. Scale bars equal 10 mm. (<b>i</b>) Virtual reconstructions of the frontal and parietal bones in SMU 76335 in ventral view. Grey areas on the endocasts represent regions that could not be reconstructed. Abbreviations: 1, cephalic flexure; 2, pontine flexure; cart., cartilaginous bridge; ch, cerebral hemispheres; dienc, ventral diencephalon; Fr, frontal; fr.c, frontal cranial crests; mo, medulla oblongata; mvm, mesencephalic ventral margin; ob, olfactory bulbs; oc, optic chiasm; op, olfactory peduncles; Os, orbitosphenoid; ot, optic tectum; Pa, parietal; pa.c, parietal cranial crests; pa.e, parietal eye; pa.f, parietal foramen; V, trigeminal nerve; VII, facial nerve; X,XI, vagus and accessory nerves; XII, hypoglossal nerves.</p> Full article ">Figure 2
<p>Morphospaces of endocast shape between <span class="html-italic">Tethysaurus</span> and extant squamates. The two first principal component axes PC1-PC2 are visualized. The wireframes represent the difference in landmark position between the most extreme endocranial morphologies along PC1 and PC2 (figured in black) as compared to the average (figured in orange), in dorsal (<b>top</b>) and lateral (<b>bottom</b>) views. Abbreviations of the species names are in <a href="#diversity-16-00548-t001" class="html-table">Table 1</a>.</p> Full article ">Figure 3
<p>Linear Discriminant Analysis of endocranial shape variation in toxicoferans squamates, constructed from DF1 and DF2. Area of distribution of iguanians, anguimorphs, and snakes are figured in red, black, and green, respectively. The inverted blue triangle indicates the position of the mosasaurid <span class="html-italic">Tethysaurus nopcsai.</span></p> Full article ">
16 pages, 15119 KiB  
Article
Skin Anatomy, Bone Histology and Taphonomy of a Toarcian (Lower Jurassic) Ichthyosaur (Reptilia: Ichthyopterygia) from Luxembourg, with Implications for Paleobiology
by Ida Bonnevier Wallstedt, Peter Sjövall, Ben Thuy, Randolph G. De La Garza, Mats E. Eriksson and Johan Lindgren
Diversity 2024, 16(8), 492; https://doi.org/10.3390/d16080492 - 12 Aug 2024
Viewed by 1663
Abstract
A partial ichthyosaur skeleton from the Toarcian (Lower Jurassic) bituminous shales of the ‘Schistes Carton’ unit of southern Luxembourg is described and illustrated. In addition, associated remnant soft tissues are analyzed using a combination of imaging and molecular techniques. The fossil (MNHNL TV344) [...] Read more.
A partial ichthyosaur skeleton from the Toarcian (Lower Jurassic) bituminous shales of the ‘Schistes Carton’ unit of southern Luxembourg is described and illustrated. In addition, associated remnant soft tissues are analyzed using a combination of imaging and molecular techniques. The fossil (MNHNL TV344) comprises scattered appendicular elements, together with a consecutive series of semi-articulated vertebrae surrounded by extensive soft-tissue remains. We conclude that TV344 represents a skeletally immature individual (possibly of the genus Stenopterygius) and that the soft parts primarily consist of fossilized skin, including the epidermis (with embedded melanophore pigment cells and melanosome organelles) and dermis. Ground sections of dorsal ribs display cortical microstructures reminiscent of lines of arrested growth (LAGs), providing an opportunity for a tentative age determination of the animal at the time of death (>3 years). It is further inferred that the exceptional preservation of TV344 was facilitated by seafloor dysoxia/anoxia with periodical intervals of oxygenation, which triggered phosphatization and the subsequent formation of a carbonate concretion. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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<p>Geological map of Luxembourg and its surroundings, with the study area indicated by a green star (modified from <a href="#diversity-16-00492-f001" class="html-fig">Figure 1</a> in Ref. [<a href="#B11-diversity-16-00492" class="html-bibr">11</a>]). White lines indicate national borders.</p> Full article ">Figure 2
<p>TV344, a partial ichthyosaur from the ‘Schistes Carton’ unit of Luxembourg. (<b>A</b>): Photograph taken under polarized light. The sample site for the petrographic sections is marked with a red rectangle, whereas the samples used in our molecular analyses are demarcated by a green rectangle. The scale bar represents 5 cm. (<b>B</b>): Sketch map outlining the different components of the fossil and its surrounding matrix.</p> Full article ">Figure 3
<p>Petrographic section produced from a set of ribs on the left-hand side of TV344. (<b>A</b>): Upper part of the section, showing a more proximally located section through a rib. Scale bar represents 1 mm. (<b>B</b>): Lower part of the petrographic slide, showing a distal cross-section of a rib. Scale bar represents 500 µm. (<b>C</b>): Magnification of (<b>B</b>), as indicated by red frame. Cortical bone, cancellous bone and the medullary cavity are all indicated. Circumferential lines in the cortex are highlighted by arrowheads. Lacunae are indicated by white lines. Scale bar represents 50 µm.</p> Full article ">Figure 4
<p>Detailed photographs of TV344. (<b>A</b>): Ribs from the left side of the fossil covered by rippled skin (indicated by an arrowhead). (<b>B</b>): Close-up view of skin covering the ribs, showing the transition between the epidermis and underlying ridged layer (indicated by arrowheads).</p> Full article ">Figure 5
<p>FEG-SEM and EDX micrographs of TV344 integument. Back-scattered electron image to the left and EDX elemental maps to the right. Note dermal ridges protruding into the phosphatized epidermis, and localized concentrations of iron and sulfur in the ridges. Scale bars represent 50 μm.</p> Full article ">Figure 6
<p>Pigmentation in ichthyosaur fossils. (<b>A</b>): Epidermis of TV344 displaying dark, branching bodies (highlighted by arrowheads) with a diameter of ~10–20 μm. Scale bar represents 100 μm. (<b>B</b>): Epidermis of <span class="html-italic">Stenopterygius</span> specimen MH 432 similarly displaying dark, branching melanophores (see [<a href="#B3-diversity-16-00492" class="html-bibr">3</a>]). Melanophores highlighted by arrowheads. Scale bar represents 200 μm. (<b>C</b>,<b>D</b>): FEG-SEM micrographs of demineralized TV344 integument showing remnant melanosomes embedded in amorphous organic matter. Scale bars represent 1 μm.</p> Full article ">Figure 7
<p>Principal sketch of the inferred layering of the integument in TV344.</p> Full article ">Figure 8
<p>Model for the taphonomic conditions that enabled the fossilization of TV344. The carcass is covered by a microbial mat containing both sulphate-oxidizing and sulphate-reducing bacteria. During brief oxygenated periods (upper left half of figure), sulphate-oxidizing bacteria (black ovals) locally lower the pH, thereby enabling ions in the seawater and sediment to form a sheet of calcium phosphate on top of the carcass. During dysoxic/anoxic periods (upper right half of figure), sulphate-reducing bacteria (white ovals) locally elevated the pH, thereby facilitating the formation of a calcium carbonate nodule from ions in the seawater and sediment.</p> Full article ">Figure A1
<p>TV344 photographed under ultraviolet light.</p> Full article ">Figure A2
<p>(<b>A</b>): ToF-SIMS images of negative ions taken at Sample Point #5 on the right-hand side of the fossil (see <a href="#diversity-16-00492-f002" class="html-fig">Figure 2</a>A), representative of nitrogen-containing organics (CN<sup>−</sup>), epoxy (C<sub>4</sub>H<sub>5</sub>O<sub>2</sub><sup>−</sup>), silica (SiO<sub>2</sub><sup>−</sup>) and sulfate (SO<sub>3</sub><sup>−</sup>), respectively. The two panels in the bottom row depict an overlay of epoxy, CN<sup>−</sup> and silica together with the total signal intensity distribution. (<b>B</b>): ToF-SIMS images of positive ions acquired at Sample Point #5 on the right-hand side of the fossil (see <a href="#diversity-16-00492-f002" class="html-fig">Figure 2</a>A), representative of amino acid-containing organics (C<sub>x</sub>H<sub>y</sub>N<sup>+</sup>), aliphatic hydrocarbons (C<sub>x</sub>H<sub>y</sub><sup>+</sup>), potassium (K<sup>+</sup>) and silica (SiOH<sup>+</sup>). The two panels in the bottom row include an overlay of aliphatic hydrocarbons, potassium and silica, and the total signal intensity distribution.</p> Full article ">Figure A3
<p>Overview of a complete petrographic section obtained from TV344. Scale bar represents 5 mm.</p> Full article ">Figure A4
<p>FEG-SEM micrograph of TV344 integument, showing oblong microbodies clustered near the inner termination of the epidermis. Scale bar represents 2 μm.</p> Full article ">
12 pages, 6664 KiB  
Article
Bone Connectivity and the Evolution of Ichthyosaur Fins
by Marta S. Fernández, Lisandro Campos, Agustina Manzo and Evangelos Vlachos
Diversity 2024, 16(6), 349; https://doi.org/10.3390/d16060349 - 17 Jun 2024
Viewed by 1956
Abstract
After the end-Triassic extinction, parvipelvian ichthyosaurs diversified and became dominant elements of marine ecosystems worldwide. By the Early Jurassic, they achieved a thunniform body plan that persisted for the last 100 m.y.a of their evolution. Diversification and extinctions of thunniform ichthyosaurs, and their [...] Read more.
After the end-Triassic extinction, parvipelvian ichthyosaurs diversified and became dominant elements of marine ecosystems worldwide. By the Early Jurassic, they achieved a thunniform body plan that persisted for the last 100 m.y.a of their evolution. Diversification and extinctions of thunniform ichthyosaurs, and their swimming performance, have been studied from different perspectives. The transformation of limbs into hydrofoil-like structures for better control and stability during swimming predates thunniform locomotion. Despite their importance as control surfaces, fin evolution among thunnosaurs remains poorly understood. We explore ichthyosaur fin diversity using anatomical networks. Our results indicate that, under a common hydrofoil controller fin, the bone arrangement diversity of the ichthyosaur fin was greater than traditionally assumed. Changes in the connectivity pattern occurred stepwise throughout the Mesozoic. Coupled with other lines of evidence, such as the presence of a ball-and-socket joint at the leading edge of some derived Platypterygiinae, we hypothesize that fin network disparity also mirrored functional disparity likely associated with different capabilities of refined maneuvering. The ball-and-socket articulation indicates that this local point could be acting like a multiaxial intrafin joint changing the angle of attack and thus affecting the maneuverability, similar to the alula of flying birds. Further studies on large samples and quantitative experimental approaches would be worthy to test this hypothesis. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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Figure 1

Figure 1
<p><span class="html-italic">Ichthyosaurus somersetensis</span> holotype from the Hettangian of England modified from [<a href="#B21-diversity-16-00349" class="html-bibr">21</a>] (<b>A</b>). Left forefin on dorsal view (<b>B</b>). Anatomical network model of the forefin (<b>C</b>).</p> Full article ">Figure 2
<p>Principal component analysis (PCA) scatter diagram showing morphospace occupation defined by the first two PCAs explaining 77.288% of the variation. Red dashed lines represent the convex hull morphospace occupied by the three ichthyosaurs previously analyzed [<a href="#B15-diversity-16-00349" class="html-bibr">15</a>]. See <a href="#app1-diversity-16-00349" class="html-app">Table S2</a> for details on network properties of analyzed taxa.</p> Full article ">Figure 3
<p>Ichthyosauria forefin morphospace plotted separately to aid comparison of morphospace occupancy through time. This is a second PCA using only data from ichthyosaurs. If we focus on the Ichthyosauria forefin morphospace occupancy over time derived from the second PCA (<a href="#diversity-16-00349-f003" class="html-fig">Figure 3</a>), from Late Triassic represented by <span class="html-italic">Mixosaurus</span> up to the Albian (Late Cretaceous) represented by <span class="html-italic">Platypterygius hercynicus</span>, there were no major shifts in the fin morphospace occupation but an overall trend toward better integrated and more modular fins. Thus, this long-term tendency spanned for approximately 137 million years comprising most of the evolutionary history of the Ichthyosauriomorpha.</p> Full article ">Figure 4
<p>Fin evolution of Ichthyosauria. Changes in the connectivity pattern through phylogeny. On cladogram, in gray, non-Ichthyosauria ichthyosauromorphs were added for comparison; in green, 1–3, major evolutionary events related to swimming. Bottom: stepwise pattern of connectivity changes, each network property is illustrated separately to aid visualization. Abbreviations of network properties as for <a href="#diversity-16-00349-t001" class="html-table">Table 1</a>.</p> Full article ">
48 pages, 65909 KiB  
Article
Callovian Marine Reptiles of European Russia
by Nikolay Zverkov, Maxim Arkhangelsky, Denis Gulyaev, Alexey Ippolitov and Alexey Shmakov
Diversity 2024, 16(5), 290; https://doi.org/10.3390/d16050290 - 10 May 2024
Cited by 1 | Viewed by 1809
Abstract
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 [...] Read more.
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, we survey marine reptiles from the Callovian stage of European Russia. The fossils collected over more than a century from 28 localities are largely represented by isolated bones and teeth, although partial skeletons are also known. In addition to the previously described rhomaleosaurid and metriorhynchids, we identify pliosaurids of the genera Liopleurodon and Simolestes; cryptoclidid plesiosaurians, including Cryptoclidus eurymerus, Muraenosaurus sp., and cf. Tricleidus, and ophthalmosaurid ichthyosaurians, including the iconic Ophthalmosaurus icenicus. These findings expand the ranges of several Callovian marine reptile taxa far to the Eastern Europe, and support the exchange of marine reptile faunas between Western and Eastern European seas in the middle to late Callovian. However, some specimens from the lower Callovian of European Russia show differences from typical representatives of the middle Callovian Oxford Clay fauna, possibly representing the earlier stages of evolution of some of these marine reptiles not yet recorded in Western Europe or elsewhere. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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<p>Localities of known marine reptile fossils from the Callovian of European Russia shown by red asterisks (<b>B</b>). Blue colorations on the map show outlines of the Middle Russian Sea during the Callovian, based on [<a href="#B71-diversity-16-00290" class="html-bibr">71</a>]. The upper left (<b>A</b>) shows Callovian paleogeography of Europe (after [<a href="#B72-diversity-16-00290" class="html-bibr">72</a>]; modified according to the data of [<a href="#B69-diversity-16-00290" class="html-bibr">69</a>,<a href="#B71-diversity-16-00290" class="html-bibr">71</a>]), with red dots showing the main localities of Callovian marine reptiles in Europe (i.e., numerous localities with the Oxford Clay Formation in England [<a href="#B4-diversity-16-00290" class="html-bibr">4</a>,<a href="#B5-diversity-16-00290" class="html-bibr">5</a>,<a href="#B6-diversity-16-00290" class="html-bibr">6</a>,<a href="#B7-diversity-16-00290" class="html-bibr">7</a>,<a href="#B8-diversity-16-00290" class="html-bibr">8</a>,<a href="#B9-diversity-16-00290" class="html-bibr">9</a>,<a href="#B10-diversity-16-00290" class="html-bibr">10</a>,<a href="#B11-diversity-16-00290" class="html-bibr">11</a>,<a href="#B73-diversity-16-00290" class="html-bibr">73</a>], localities in Northern and Southern France [<a href="#B12-diversity-16-00290" class="html-bibr">12</a>,<a href="#B13-diversity-16-00290" class="html-bibr">13</a>,<a href="#B14-diversity-16-00290" class="html-bibr">14</a>,<a href="#B15-diversity-16-00290" class="html-bibr">15</a>,<a href="#B16-diversity-16-00290" class="html-bibr">16</a>,<a href="#B17-diversity-16-00290" class="html-bibr">17</a>,<a href="#B18-diversity-16-00290" class="html-bibr">18</a>,<a href="#B19-diversity-16-00290" class="html-bibr">19</a>,<a href="#B20-diversity-16-00290" class="html-bibr">20</a>,<a href="#B21-diversity-16-00290" class="html-bibr">21</a>,<a href="#B74-diversity-16-00290" class="html-bibr">74</a>], Spain [<a href="#B75-diversity-16-00290" class="html-bibr">75</a>], Switzerland [<a href="#B76-diversity-16-00290" class="html-bibr">76</a>], Northern Germany [<a href="#B22-diversity-16-00290" class="html-bibr">22</a>,<a href="#B23-diversity-16-00290" class="html-bibr">23</a>,<a href="#B24-diversity-16-00290" class="html-bibr">24</a>,<a href="#B25-diversity-16-00290" class="html-bibr">25</a>,<a href="#B26-diversity-16-00290" class="html-bibr">26</a>], and Poland [<a href="#B77-diversity-16-00290" class="html-bibr">77</a>,<a href="#B78-diversity-16-00290" class="html-bibr">78</a>]). Dashed contour on (<b>A</b>) shows the area depicted in (<b>B</b>).</p> Full article ">Figure 2
<p>Stratigraphic sections of the Callovian marine reptile localities in the Unzha River basin (Kostroma Region) and distribution of marine reptile remains. Abbreviations of ammonite zones and subzones: Call/Callov, Calloviense; Curt/Curtilob, Curtilobum; En/Enod/Enodat, Enodatum; G/Gal, Galilaeii; J, Jason.</p> Full article ">Figure 3
<p>Stratigraphic sections of the Callovian marine reptile localities in Moscow and Ryazan regions and distribution of marine reptile remains. For lithology and other symbols of the legend see <a href="#diversity-16-00290-f002" class="html-fig">Figure 2</a>. Abbreviations of ammonite zones and subzones: Athl, Athleta; C/Curt, Curtilobum; Call/Callov, Calloviense; Cor, Coronatum; Cordat, Cordatum; Enod/Enodat, Enodatum; Gal, Galilaeii; Gow, Gowerianum; Gr/Gross, Grossouvrei; Hen, Henrici; J/Jas, Jason; K/Koen, Koenigi; Ku, Kuklikum; L/Lamb, Lamberti; M/Med, Medea; O/Obd, Obductum; Ph, Phaeinum; Pr, Proniae. Mikhaylovcement section modified after [<a href="#B79-diversity-16-00290" class="html-bibr">79</a>]; Peski after [<a href="#B80-diversity-16-00290" class="html-bibr">80</a>]; Alpatyevo after [<a href="#B81-diversity-16-00290" class="html-bibr">81</a>].</p> Full article ">Figure 4
<p>Stratigraphic sections of the Callovian marine reptile localities in Ryazan and Nizhny Novgorod regions, Republic of Mordovia, and Saratov Region. For lithology and other symbols of the legend, see <a href="#diversity-16-00290-f002" class="html-fig">Figure 2</a>. Abbreviations of ammonite zones and subzones: Athl, Athleta; C, Curtilobum; Call/Callov, Calloviense; Cor, Coronatum; Enod, Enodatum; G, Gowerianum; Galil, Galilaeii; Gr– Grossouvrei; Jas, Jason; K, Koenigi; M, Medea; O/Obd, Obductum; Ph, Phaeinum; Pr, Proniae; Praecord, Praecordatum; Scarbur, Scarburgense. Yelatma locality section modified after [<a href="#B82-diversity-16-00290" class="html-bibr">82</a>,<a href="#B83-diversity-16-00290" class="html-bibr">83</a>,<a href="#B84-diversity-16-00290" class="html-bibr">84</a>]; Uzhovka and Trofimovshchina-2 originally drawn herein based on A.I.’s field descriptions; CHP-5 after [<a href="#B85-diversity-16-00290" class="html-bibr">85</a>]; Dubki after [<a href="#B86-diversity-16-00290" class="html-bibr">86</a>,<a href="#B87-diversity-16-00290" class="html-bibr">87</a>].</p> Full article ">Figure 5
<p>Teeth of <span class="html-italic">Liopleurodon ferox</span> from the Callovian of European Russia. Mesial (“caniniform” type) teeth PIN R-3573 (<b>A</b>–<b>D</b>) from the middle Callovian of Ryazan Region, and SGM 2007-7 (<b>M</b>) from the lower Callovian of Makariev, Kostroma Region. Distal (“ratchet” type) teeth SGM 1807 (<b>E</b>–<b>I</b>) and SGM 2007-6 (<b>J</b>–<b>L</b>) from the lower Callovian of Makariev, Kostroma Region. Views: anterior or posterior (<b>D</b>,<b>E</b>,<b>G</b>,<b>L</b>), lingual (<b>C</b>,<b>F</b>,<b>K</b>), labial (<b>B</b>,<b>H</b>,<b>J</b>), and apical (<b>D</b>,<b>I</b>).</p> Full article ">Figure 6
<p>Postcranial skeleton of <span class="html-italic">Liopleurodon ferox</span>, SGM 1807. Right coracoid (<b>A</b>–<b>D</b>) in dorsal (<b>A</b>), glenoidal (<b>B</b>), mesial symphysial (<b>C</b>), and anterior (in articulation with the medial portion of left coracoid) (<b>D</b>) views. Partial right hindlimb in ventral view (<b>E</b>); right femur in dorsal (<b>F</b>), posterior (<b>G</b>), proximal (<b>H</b>), and distal (<b>I</b>) views. Phalanges (<b>J</b>). Interclavicle (?) in dorsal (<b>K</b>) and anterior (<b>L</b>) views. Left ischium in dorsal (<b>M</b>), acetabular (<b>N</b>), and mesial, symphysial (<b>O</b>) views. Cervical ribs (<b>P</b>–<b>V</b>) in dorsal (<b>P</b>,<b>R</b>), ventral (<b>Q</b>,<b>S</b>), anterior (<b>T</b>), posterior (<b>U</b>), and proximal (<b>V</b>) views. Dorsal ribs (<b>W</b>–<b>Y</b>) and sacral rib (<b>Z</b>,<b>Z’</b>). Reconstructed outlines of broken parts are shown in gray.</p> Full article ">Figure 7
<p>Pliosaurid remains. Left maxilla of <span class="html-italic">Simolestes</span> sp. SGM 574-01 (<b>A</b>–<b>C</b>), in lateral (<b>A</b>) and ventral (<b>B</b>) views. (<b>C</b>) Position of the element in the skull (in orange). Femur of <span class="html-italic">Simolestes</span> sp. SGM 569-1 (<b>D</b>–<b>G</b>), in dorsal (<b>D</b>), posterior (<b>E</b>), proximal (<b>F</b>), and distal (<b>G</b>) views. Proximal portion of a large propodial (likely femur), NNGASU 147/2080 (<b>H</b>–<b>K</b>), in anterior or posterior (<b>H</b>), dorsal (<b>I</b>), and proximal (<b>J</b>) views. (<b>K</b>) Position of the fragment (in orange). Articular portion of the vertebral centrum, YSPU M/F-45, in (?) dorsal (<b>L</b>) and articular (<b>M</b>) views. Pliosaurid sacral vertebra, TsNIGR 157a/649, in articular (<b>N</b>) and right? lateral (<b>O</b>) views. Abbreviations: 1–9, positions of maxillary alveoli; na, external nares; tub, dorsal trochanter/tuberosity.</p> Full article ">Figure 8
<p>Pliosaurid teeth from the Callovian of European Russia. Pliosauridae cf. <span class="html-italic">Simolestes</span> PIN R-3589 (<b>A</b>–<b>C</b>) from the middle Callovian of Gzhel; Pliosauridae indet., PIN 5818/8 (<b>D</b>–<b>G</b>) from the middle Callovian of Rechitsy; Pliosauridae indet. PIN R-3574 (<b>H</b>–<b>K</b>) from the middle Callovian of Nikitino; Pliosauridae indet. PIN R-3575 (<b>L</b>–<b>N</b>) from the upper Callovian of Dubki; lost holotype of “<span class="html-italic">Thaumatosaurus calloviensis</span>” (<b>O</b>,<b>P</b>), referred to <span class="html-italic">Simolestes</span> sp. herein, from the middle Callovian of Rechitsy, reproduced from Bogolubov [<a href="#B33-diversity-16-00290" class="html-bibr">33</a>] (pl. II, figs. 1 and 6); Pliosauridae indet. SGM 2007-5 (Q) from the lower Callovian of Mikhalenino, Kostroma Region. Views: labial (<b>A</b>,<b>E</b>,<b>H</b>,<b>L</b>), lingual (<b>D</b>,<b>I</b>), mesial or distal (<b>B</b>,<b>F</b>,<b>G</b>,<b>J</b>,<b>M</b>,<b>P</b>,<b>Q</b>), apical (<b>C</b>,<b>K</b>,<b>N</b>), and oblique labial from the apex (<b>O</b>).</p> Full article ">Figure 9
<p>Postcranial elements of <span class="html-italic">Cryptoclidus eurymerus</span>, PIN R-3600, from the middle Callovian of Nikitino, Ryazan Region. Left humerus in articulation with the radius in dorsal (<b>A</b>) and anterior (<b>B</b>) views; reconstruction of their position in the limb (in orange), left humerus in ventral (<b>C</b>) and distal (<b>D</b>) views. Right radius in dorsal view (<b>E</b>). Partial pubis in dorsal view (<b>F</b>). Left femur in ventral (<b>G</b>), anterior (<b>H</b>), dorsal (<b>I</b>), and distal (<b>J</b>) views. Partial right femur in dorsal view (<b>K</b>). Two gastralia (<b>L</b>), dorsal rib in anterior view (<b>M</b>), and in articulation with dorsal vertebra (<b>N</b>).</p> Full article ">Figure 10
<p>Vertebrae of <span class="html-italic">Cryptoclidus eurymerus</span> PIN R-3600, from the middle Callovian of Nikitino, Ryazan Region. Cervical vertebrae (<b>A</b>–<b>F</b>) in anterior (<b>A</b>,<b>D</b>), left lateral (<b>B</b>,<b>E</b>), and ventral (<b>C</b>,<b>F</b>) views. Pectoral vertebra (<b>G</b>–<b>I</b>) in anterior (<b>G</b>), right lateral (<b>H</b>), and ventral (<b>I</b>) views. Dorsal vertebra in anterior (<b>J</b>) and left lateral (<b>K</b>) views.</p> Full article ">Figure 11
<p>Isolated cryptoclidid teeth from the lower Callovian of Kostroma (<b>A</b>–<b>J</b>, <b>N</b>–<b>Z’</b>) and Ryazan (<b>K</b>–<b>M</b>) regions. <span class="html-italic">Muraenosaurus</span> sp. SGM 2007-3/1 (<b>A</b>–<b>E</b>), SGM 2007-3/2 (<b>F</b>–<b>J</b>), SGM 2007-3/3 (<b>N</b>–<b>Q</b>), PIN 5819/3 (<b>S</b>–<b>V</b>). <span class="html-italic">Cryptoclidus</span> sp. PIN R-3621 (<b>K</b>–<b>M</b>). cf. <span class="html-italic">Tricleidus</span> SGM 2007-4 (<b>W</b>–<b>Z’</b>). Views: mesial or distal (<b>A</b>,<b>C</b>,<b>G</b>,<b>I</b>,<b>K</b>,<b>N</b>,<b>P</b>,<b>S</b>,<b>W</b>,<b>Y</b>), labial (<b>D</b>,<b>J</b>,<b>L</b>,<b>Q</b>,<b>U</b>,<b>Z</b>), lingual (<b>B</b>,<b>H</b>,<b>M</b>,<b>O</b>,<b>X</b>), apical (<b>E</b>,<b>F</b>,<b>R</b>,<b>V</b>,<b>Z’</b>). Occlusal wear facets are visible at the tooth root on (<b>C</b>) and (<b>G</b>,<b>H</b>). K–M are SEM photographs with the bottom row magnified x2 relative to the top row and schematic cross-section of the crown with apicobasal lingual grooves shown below.</p> Full article ">Figure 12
<p>Cervical vertebrae of cf. <span class="html-italic">Muraenosaurus</span> (Morphotype 1). Anterior cervical vertebra SGM 1358-37 from the (?)lower Callovian of Alpatyevo (<b>A</b>–<b>C</b>), originally described by Bogolubov [<a href="#B33-diversity-16-00290" class="html-bibr">33</a>]. Anterior cervical vertebra SGM 1891-08 (<b>D</b>–<b>F</b>) from the lower Callovian of Mikhalenino. Posterior cervical vertebrae SGM 1891-10 (<b>G</b>–<b>J</b>) and SGM 1891-9 (<b>K</b>–<b>N</b>) from the lower Callovian of Mikhalenino. Middle to posterior cervical vertebra PIN R-3590 (<b>O</b>–<b>Q</b>) from the upper Callovian of Peski. Posterior cervical vertebra PIN R-3595 (<b>R</b>–<b>T</b>) from the middle Callovian of Mihailovcement. Views: anterior articular (<b>A</b>,<b>D</b>,<b>G</b>,<b>K</b>,<b>R</b>), lateral (<b>B</b>,<b>E</b>,<b>J</b>,<b>N</b>,<b>Q</b>,<b>T</b>), ventral (<b>C</b>,<b>F</b>,<b>I</b>,<b>M</b>,<b>P</b>,<b>S</b>), and dorsal (<b>H</b>,<b>L</b>).</p> Full article ">Figure 13
<p>Plesiosauroid vertebrae from the Callovian of European Russia. Cervical vertebrae of short-necked cryptoclidids (Morphotype 2) (<b>A</b>–<b>H</b>); juvenile PIN R-3591 (<b>A</b>–<b>D</b>) and osteologically mature PIN R-3670 (<b>E</b>–<b>H</b>). Anterior dorsal vertebra of osteologically mature small cryptoclidid collected in association with <span class="html-italic">Liopleurodon</span> skeleton SGM 1807. Dorsal vertebra cf. <span class="html-italic">Muraenosaurus</span> TsNIGR 144/1712 (<b>L</b>–<b>N</b>). Dorsal vertebra cf. <span class="html-italic">Cryptoclidus</span> YSPU M/F-44 (<b>O</b>,<b>P</b>). Dorsal centrum of osteologically immature plesiosaurian SGM 1891-05 (<b>Q</b>–<b>T</b>). Pectoral PIN R-3709 (<b>U</b>–<b>X</b>), sacral PIN R-3606 (<b>Y</b>–<b>B’</b>), and caudal PIN R-3201(<b>C’</b>–<b>E’</b>) and PIN R-3596(<b>F’</b>–<b>I’</b>) vertebrae. Views: articular (<b>A</b>,<b>E</b>,<b>I</b>,<b>L</b>,<b>O</b>,<b>Q</b>,<b>U</b>,<b>Y</b>,<b>C’</b>,<b>F’</b>), dorsal (<b>B</b>,<b>G</b>,<b>J</b>,<b>S</b>,<b>W</b>,<b>E’</b>,<b>H’</b>), ventral (<b>C</b>,<b>H</b>,<b>K</b>,<b>T</b>,<b>X</b>,<b>B’</b>,<b>I</b>), lateral (<b>D</b>,<b>F</b>,<b>M</b>,<b>P</b>,<b>V</b>,<b>Z</b>,<b>D’</b>,<b>G’</b>), cross-section (<b>A’</b>).</p> Full article ">Figure 14
<p><span class="html-italic">Ophthalmosaurus</span> specimens from the lower Callovian of the Republic of Mordovia. Partial skeleton of <span class="html-italic">Ophthalmosaurus</span> cf. <span class="html-italic">calloviensis</span> PSM 3999-4004 (<b>A</b>–<b>M</b>) from Rybkino locality. Sclerotic ring (<b>A</b>). Dentigerous bone fragment (likely maxilla) in lateral (<b>B</b>) and ventral (<b>C</b>) views. Magnified teeth (<b>D</b>,<b>E</b>). Caudal preflexural (<b>F</b>,<b>G</b>), apical (<b>H</b>,<b>I</b>) and postflexiral, “fluke” (<b>J</b>,<b>K</b>), centra in articular (<b>F</b>,<b>I</b>,<b>J</b>) and lateral (<b>G</b>,<b>H</b>,<b>K</b>) views. Radius and ulna in proximal (<b>L</b>) and dorsal/ventral (<b>M</b>) views. Skull of a partial skeleton of <span class="html-italic">Ophthalmosaurus</span> sp. (<b>N</b>) from the lower Callovian of Sinyakovo locality reported by [<a href="#B38-diversity-16-00290" class="html-bibr">38</a>], in oblique anterolateral view. Isolated radius of <span class="html-italic">Ophthalmosaurus</span> cf. <span class="html-italic">calloviensis</span> (SGM 1891-06) from Trofimovshchina-2 locality in dorsal/ventral (<b>O</b>) and proximal (<b>P</b>) views. Abbreviations: faae, facet for anterior accessory element; fe, free surface; fim, facet for intermedium; fre, facet for radiale.</p> Full article ">Figure 15
<p>Ophthalmosaurids from the Callovian of Saratov Region. Holotype forelimb of <span class="html-italic">Ophthalmosaurus calloviensis</span> SSU 104a/27 (<b>A</b>–<b>E</b>) in dorsal (<b>A</b>), ventral (<b>B</b>), anterior (<b>C</b>), posterior (<b>D</b>), and proximal (<b>E</b>) views. Fragments of a partial skeleton SSTU MEZ 3/4 (<b>F</b>–<b>W</b>). Articulated nasals in dorsal view (<b>F</b>), partial premaxilla (<b>G</b>) and dentary (<b>H</b>) in lateral views. Right scapula (with associated rib fragments and distal limb elements) in dorsal (<b>I</b>), ventral (<b>J</b>), and proximal (<b>K</b>) views. Anterior dorsal (<b>L</b>,<b>M</b>), and posterior dorsal to anterior caudal (<b>N</b>–<b>Q</b>) centra in articular (<b>L</b>,<b>N</b>,<b>P</b>) and lateral (<b>M</b>,<b>O</b>,<b>Q</b>) views. Intermedium in dorsal/ventral (<b>R</b>) and proximal (<b>S</b>) views. Anterior accessory element in dorsal/ventral (<b>T</b>) and posterior (<b>U</b>) views. Phalanges in dorsal/ventral view (<b>V</b>,<b>W</b>).</p> Full article ">Figure 16
<p>Cranial elements of <span class="html-italic">Ophthalmosaurus icenicus</span>, SGM 1961, from the middle Callovian of Perebory, Yaroslavl Region. Ventral portion of the left quadrate in posteromedial (<b>A</b>), condylar (<b>B</b>) and dorsal (<b>C</b>) views. Partial left angular in anterior cross-sectional (<b>E</b>), lateral (<b>D</b>), posterior (<b>F</b>), dorsal (<b>G</b>), and medial (<b>H</b>) views. Abbreviations: fqj, facet for quadratojugal; fspl, facet for splenial; fst, facet for stapes; fsur, facet for surangular.</p> Full article ">Figure 17
<p>Vertebral centra of <span class="html-italic">Ophthalmosaurus icenicus</span>, SGM 1961, from the middle Callovian of Perebory, Yaroslavl Region. Atlas–axis complex in anterior (<b>A</b>) and posterior (<b>B</b>) views; articulated with the third centrum in left lateral (<b>C</b>), dorsal (<b>D</b>), and ventral (<b>E</b>) views. Third centrum in anterior articular view (<b>F</b>). Anterior dorsal (<b>G</b>–<b>M</b>), posterior dorsal (<b>N</b>–<b>T</b>), and caudal (<b>U</b>–<b>G’</b>) centra, in articular (<b>G</b>,<b>K</b>,<b>N</b>,<b>R</b>,<b>U</b>,<b>Y</b>,<b>C’</b>,<b>D’</b>), lateral (<b>H</b>,<b>L</b>,<b>O</b>,<b>S</b>,<b>V</b>,<b>Z</b>,<b>E’</b>), dorsal (<b>I</b>,<b>M</b>,<b>P</b>,<b>T</b>,<b>W</b>,<b>A’</b>,<b>F’</b>), and ventral (<b>J</b>,<b>Q</b>,<b>X</b>,<b>B’</b>,<b>G’</b>) views.</p> Full article ">Figure 18
<p>Forelimb remains of <span class="html-italic">Ophthalmosaurus</span>. Partial right forelimb of <span class="html-italic">Ophthalmosaurus icenicus</span>, SGM 1961, in dorsal view (<b>A</b>). Humerus of SGM 1961 in ventral (<b>B</b>), anterior (<b>C</b>), posterior (<b>D</b>), distal (<b>E</b>), and proximal (<b>F</b>) views. Ulna of SGM 1961 in posterior view (<b>G</b>), and proximal surfaces of the ulna and radius (<b>H</b>). Partial left forelimb of <span class="html-italic">Ophthalmosaurus icenicus</span> PIN R-4956 (<b>I</b>–<b>N</b>) from the upper Callovian of Zmeinka Quarry, Ryazan Region, in dorsal (<b>I</b>) and ventral (<b>K</b>) views. Humerus of PIN R-4956 in anterior (<b>J</b>), posterior (<b>L</b>), proximal (<b>M</b>), and distal (<b>N</b>) views. Anterior accessory epipodial element (?) of cf. <span class="html-italic">Ophthalmosaurus</span> PIN R-2516 (<b>O</b>,<b>P</b>), from the upper Callovian of Mikhaylovcement Quarry, Ryazan Region in dorsal/ventral (<b>O</b>) and anterior (<b>P</b>) views.</p> Full article ">Figure 19
<p>Ophthalmosaurid cranial remains from the Callovian of the Unzha River basin, Kostroma Region. Partial mandible with teeth SGM 1891-20 (<b>A</b>–<b>D</b>), on (<b>B</b>–<b>D</b>) magnified teeth. Isolated tooth SGM 2007-8 (<b>E</b>–<b>H</b>) and tooth crown PIN 5819/4 (<b>I</b>,<b>J</b>) in labial (<b>E</b>,<b>J</b>), anterior or posterior (<b>F</b>,<b>C</b>), lingual (<b>B</b>,<b>G</b>,<b>D</b>), and apical (<b>H</b>,<b>I</b>) views. Left quadrate, SSU uncatalogued, (<b>K</b>–<b>M</b>) in posteromedial (K), posterior (<b>L</b>), and condylar (<b>M</b>) views. Left jugal SGM 1891-22 in lateral (<b>N</b>) and medial (<b>O</b>) views. Left premaxilla SGM 2000-1 (<b>P</b>–<b>R</b>), in dorsal (<b>P</b>), lateral (<b>Q</b>), and ventral (<b>R</b>) views.</p> Full article ">Figure 20
<p>Ichthyosaurian veretebral centra from the Callovian of European Russia. Anterior dorsal centra SGM 1891-02 (<b>A</b>–<b>C</b>) and IG 93/13 (<b>D</b>). Middle dorsal centra ZIN PH 1/215 (<b>E</b>–<b>G</b>) and SGM 1891-04 (<b>I</b>–<b>K</b>). Posterior dorsal centra PIN R-3200 (<b>H</b>), SGM 1891-25 (<b>N</b>–<b>P</b>), SGM 1891-15 (<b>Q</b>–<b>S</b>). Anterior caudal centrum SGM 1891-19 (<b>L</b>,<b>M</b>). Posterior preflexural caudal centra SGM 1891-14 (<b>T</b>–<b>V</b>), PIN R-3593 (<b>W</b>–<b>Z</b>) and SGM 1891-24 (<b>A’</b>–<b>D’</b>). Series of postflexural (fluke) vertebrae SGM 1891-21 (<b>E’</b>,<b>F’</b>). Views: articular (<b>A</b>,<b>D</b>,<b>G</b>,<b>H</b>,<b>I</b>,<b>L</b>,<b>N</b>,<b>Q</b>,<b>T</b>,<b>W</b>,<b>A’</b>,<b>F’</b>), lateral (<b>B</b>,<b>F</b>,<b>J</b>,<b>O</b>,<b>R</b>,<b>U</b>,<b>X</b>,<b>B’</b>,<b>E’</b>), dorsal (<b>C</b>,<b>E</b>,<b>K</b>,<b>V</b>,<b>Y</b>,<b>C’</b>), ventral (<b>M</b>,<b>P</b>,<b>S</b>,<b>Z</b>,<b>D’</b>).</p> Full article ">Figure 21
<p>Metriorhynchid cervical vertebra SGM 2007-02 from the Callovian of Mikhaylovcement Quarry in anterior (<b>A</b>), posterior (<b>B</b>), left lateral (<b>C</b>), ventral (<b>D</b>), and dorsal (<b>E</b>) views. Thalattosuchian metacarpal or metatarsal SGM 1891-01 (<b>F</b>–<b>J</b>) from the lower Callovian of Mikhalenino.</p> Full article ">Figure 22
<p>Stratigraphic distribution of marine reptiles in Western Europe (<b>left</b>) and European Russia (<b>right</b>). Ammonite zones/subzones highlighted in gray are the main levels with marine reptile fossils. For Western Europe, data on stratigraphic distribution of reptiles follow [<a href="#B8-diversity-16-00290" class="html-bibr">8</a>,<a href="#B9-diversity-16-00290" class="html-bibr">9</a>,<a href="#B73-diversity-16-00290" class="html-bibr">73</a>,<a href="#B122-diversity-16-00290" class="html-bibr">122</a>,<a href="#B139-diversity-16-00290" class="html-bibr">139</a>,<a href="#B142-diversity-16-00290" class="html-bibr">142</a>], and partially follow [<a href="#B78-diversity-16-00290" class="html-bibr">78</a>,<a href="#B143-diversity-16-00290" class="html-bibr">143</a>] for thalattosuchians. Occurrences with some uncertainties are shown in boxes with dashed margins; light shades indicate potential ranges based on ambiguous evidence or uncertainties in the age of specimens. Some ranges for early and late Callovian plesiosaurians in Western Europe are expanded according to Bardet [<a href="#B19-diversity-16-00290" class="html-bibr">19</a>,<a href="#B20-diversity-16-00290" class="html-bibr">20</a>] and Sachs and Nyhuis [<a href="#B25-diversity-16-00290" class="html-bibr">25</a>].</p> Full article ">
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Article
Exceptional In Situ Preservation of Chondrocranial Elements in a Coniacian Mosasaurid from Colombia
by María Eurídice Páramo-Fonseca, José Alejandro Narváez-Rincón, Cristian David Benavides-Cabra and Christian Felipe Yanez-Leaño
Diversity 2024, 16(5), 285; https://doi.org/10.3390/d16050285 - 10 May 2024
Cited by 1 | Viewed by 2174
Abstract
The first record of well-preserved chondrocranial elements in mosasaurids is here described. These elements are preserved in situ in a Coniacian skull found in north-central Colombia, inside a calcareous concretion. Based on a 3D model generated from computed tomography scans, we identified elements [...] Read more.
The first record of well-preserved chondrocranial elements in mosasaurids is here described. These elements are preserved in situ in a Coniacian skull found in north-central Colombia, inside a calcareous concretion. Based on a 3D model generated from computed tomography scans, we identified elements of the nasal and orbitotemporal regions. Our descriptions show that in this specimen, the chondrocranium was reduced, more so than in most lacertilians (including their closest recent relatives, the varanids), but not as severely as in snakes or amphisbaenians (which have an extremely reduced chondrocranium and limbs). The new evidence suggests that the reduction in the chondrocranium in mosasaurids could be related to modification of their limbs when adapting to aquatic environments, but also that in mosasaurids, the olfactory tract was reduced, and the optic muscle insertions occurred mainly in the interorbital septum. The exceptional preservation of the chondrocranial elements in the specimen is facilitated by a gray mineralization covering them. XRD analysis and thin section observations indicated that this mineralization is composed of microcrystalline quartz and calcite. We infer that this material was produced by a partial silicification process promoted by lower pH microenvironments associated with bacterial breakdown of non-biomineralized tissues during early diagenesis. Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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Figure 1
<p>(<b>A</b>) Schematic diagram of a lizard-like chondrocranium in right lateral view (redrawn and modified from [<a href="#B2-diversity-16-00285" class="html-bibr">2</a>,<a href="#B3-diversity-16-00285" class="html-bibr">3</a>]) adapted to a mosasaur-like skull silhouette. (<b>B</b>–<b>E</b>) IGMp879524 skull showing the preserved in situ chondrocranial elements. (<b>B</b>,<b>C</b>) Photographs of the skull in (<b>B</b>), right lateral and (<b>C</b>) dorsal views. (<b>D</b>) Opaque 3D model of the skull in right lateral view (3D Slicer option CT-AAA). (<b>E</b>) Transparent 3D model of the skull in dorsal view (3D Slicer option CT-X-ray). The preserved chondrocranial elements are highlighted in blue. Part of the mandible and the braincase are not included in the 3D model. <b>Abbreviations</b>: <b>bpl</b>, basal plate; <b>c</b>, coronoid; <b>d</b>, dentary; <b>f</b>, frontal; <b>ios</b>, interorbital septum; <b>j</b>, jugal; <b>Mc</b>, Meckel’s cartilage; <b>mx</b>, maxilla; <b>nca</b>, nasal capsules; <b>ns</b>, nasal septum; <b>oa</b>, occipital arch; <b>or</b>, orbit; <b>orc</b>, orbital cartilage; <b>otc</b>, otic capsule; <b>p</b>, parietal; <b>pof</b>, postorbitofrontal; <b>prf</b>, prefrontal; <b>pls</b>, planum supraseptale; <b>ps</b>, parasphenoid; <b>q</b>, quadrate; <b>sa</b>, surangular; <b>tr</b>, trabeculae cranii. Scale bars: 100 mm.</p> Full article ">Figure 2
<p>Location of the chondrocranial elements in IGMp879524 skull. (<b>A</b>–<b>E</b>) Three-dimensional model (left) and cross-section scans (right) of the skull without the complete mandible. The chondrocranial elements are highlighted in blue. The black planes and arrows in the 3D models indicate the position and orientation of the cross-sections shown on the right side. (<b>F</b>) Detail of the interorbital septum in its left side showing its porous texture. <b>Abbreviations</b>: <b>f</b>, frontal; <b>ios</b>, interorbital septum; <b>lnc?</b>, probable element of the left nasal capsule; <b>pl</b>, palatine; <b>pns?</b>, probable element of the posterior region of the nasal septum; <b>pof</b>, postorbitofrontal; <b>prf</b>, prefrontal; <b>ps</b>, parasphenoid rostrum; <b>pss</b>, planum supraseptale; <b>rnc?</b>, probable element of the right nasal capsule; <b>tc</b>, trabeculae comunis. Scale bars: (<b>A</b>–<b>E</b>) 50 mm; (<b>F</b>) 30 mm.</p> Full article ">Figure 3
<p>Three-dimensional model of the chondrocranial elements and contacting bones of IGMp879524 in (<b>A</b>) dorsal, (<b>B</b>) posterior, (<b>C</b>) right lateral, (<b>D</b>) anterior, and (<b>E</b>) ventral views. <b>Abbreviations</b>: <b>ans?</b>, probable element of the anterior region of the nasal septum; <b>ch</b>, cartilago hypochiasmatica; <b>f</b>, frontal; <b>ios</b>, interorbital septum; <b>lnc?</b>, probable element of the left nasal capsule; <b>pns?</b>, probable element of the posterior region of the nasal septum; <b>prf</b>, prefrontal; <b>ps</b>, parasphenoid rostrum; <b>psf</b>, posterior septal fenestra; <b>psr</b>, parasphenoid rostrum; <b>pss</b>, planum supraseptale; <b>rnc?</b>, probable element of the right nasal capsule; <b>tc</b>, trabeculae comunis; <b>tm</b>, taenia medialis. Scale bar: 50 mm.</p> Full article ">Figure 4
<p>(<b>A</b>,<b>B</b>) Gray mineralization in the IGMp879524 skull. (<b>A</b>) Left lateral view of the skull within the concretion before acid preparation. (<b>B</b>) Left lateroventral view of the skull and concretion during chemical preparation. (<b>C</b>) Diffractogram of the gray mineralization; <b>Abbreviations</b>: <b>gm</b>, gray mineralization. Scale bar in (<b>A</b>,<b>B</b>): 10 cm.</p> Full article ">Figure 5
<p>Thin section microphotographs. (<b>A</b>,<b>B</b>) With plane polarized light PPL (left) and crossed polarized light XPL (right). (<b>A</b>) Gray mineralization showing microcrystalline quartz with a smaller proportion of microcrystalline calcite; (<b>B</b>) calcareous matrix showing microcrystalline calcite with scattered clusters of microcrystalline quartz. (<b>C</b>) Contact between the gray mineralization rich in quartz (left) and the matrix rich in <b>calcite</b> (right) (XPL). (<b>D</b>) Dinoflagellate cysts in the gray mineralization (PPL); (<b>E</b>) phosphatic bone with sparitic calcite crystals filling its pores (PPL). (<b>F</b>) Microcrystalline quartz filling veins in the calcareous matrix (XPL). <b>Abbreviations</b>: <b>b</b>, bone; <b>dc</b>, dinoflagellate cyst; <b>mc</b>, microcrystalline calcite; <b>mq</b>, microcrystalline quartz; <b>mqc</b>, microcrystalline quartz cluster.</p> Full article ">
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Article
How Elongated? The Pattern of Elongation of Cervical Centra of Elasmosaurus platyurus with Comments on Cervical Elongation Patterns among Plesiosauromorphs
by José Patricio O’Gorman
Diversity 2024, 16(2), 106; https://doi.org/10.3390/d16020106 - 7 Feb 2024
Viewed by 2959
Abstract
Elasmosaurids comprise some of the most extreme morphotypes of plesiosaurs. Thus, the study of their neck and vertebrae elongation patterns plays a crucial role in understanding the anatomy of elasmosaurids. In this study, the taphonomic distortion of the holotype of Elasmosaurus platyurus and its [...] Read more.
Elasmosaurids comprise some of the most extreme morphotypes of plesiosaurs. Thus, the study of their neck and vertebrae elongation patterns plays a crucial role in understanding the anatomy of elasmosaurids. In this study, the taphonomic distortion of the holotype of Elasmosaurus platyurus and its effects on the vertebral length index (VLI) values are evaluated, and a new index to describe the neck is proposed (MAVLI = mean value of the vertebral elongation index of the anterior two-thirds of neck vertebrae). The results provide a strong foundation for a new scheme of neck elongation patterns that divide the diversity of the neck elongation of plesiosauriomorphs into three categories: not-elongate (MAVLI < 95 and Max VLI < 100), elongate (125 > MAVLI > 95 and 100 < Max VLI < 135), and extremely elongated (MAVLI > 125 and Max VLI > 135). Full article
(This article belongs to the Special Issue Making New Out of the Old: Recent Biological Advances on Mesozoic Marine Reptiles)
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Figure 1

Figure 1
<p>Cervical vertebrae of <span class="html-italic">Elasmosaurus platyurus</span> (ANSP 10081). (<b>a</b>) The 3–5th cervical vertebrae in left lateral view, (<b>b</b>) 3rd cervical vertebra in posterior view, and (<b>c</b>) 3–5th cervical centra in ventral view. (<b>d</b>–<b>f</b>) The 11th cervical centra in (<b>d</b>) left lateral, (<b>e</b>) posterior, and (<b>f</b>) ventral views. (<b>g</b>–<b>i</b>) The 27th cervical centra in (<b>g</b>) left lateral, (<b>h</b>) posterior, and (<b>i</b>) ventral views. (<b>j</b>–<b>l</b>) The 33rd cervical vertebra in (<b>j</b>) left lateral, (<b>k</b>) posterior, and (<b>l</b>) ventral views. (<b>m</b>–<b>o</b>) The 68–69th cervical vertebrae in left lateral view. (<b>n</b>) The 69th cervical vertebra in posterior view. (<b>o</b>) The 68–69th cervical vertebrae in ventral view. Scale bar = 50 mm. cr, cervical rib, nc, neural canal.</p> Full article ">Figure 2
<p>Values of length (L), height (H), and width (B) of cervical centra of the holotype of <span class="html-italic">Elasmosaurus platyurus</span> (ANSP 10081). Black arrow indicate the vertebral range with the main taphonomical distortion.</p> Full article ">Figure 3
<p>Values of VLI (vertebral length index = 100*L/((H + B)/2) of cervical centra of the holotype of (ANSP 10081) <span class="html-italic">Elasmosaurus platyurus</span>. (<b>a</b>) comparison of original VLI values and thse obtained after correction of taphonomic distortion; (<b>b</b>), Comparison of VLI values after [<a href="#B8-diversity-16-00106" class="html-bibr">8</a>,<a href="#B16-diversity-16-00106" class="html-bibr">16</a>] and this paper after retrodeformation.</p> Full article ">Figure 4
<p>VLI of cervical region of elasmosaurids. (<b>a</b>) <span class="html-italic">Callawayasaurus colombiensis</span> (UCPM 38349), (<b>b</b>) <span class="html-italic">Thalassomedon haningtoni</span> (DMNS 1588), (<b>c</b>) <span class="html-italic">Vegasaurus molyi</span> (MLP 93-I-5-1), (<b>d</b>) <span class="html-italic">Tuarangisaurus</span> sp. (MC Zfr 115), (<b>e</b>) <span class="html-italic">Hydrotherosaurus alexandrae</span> (UCPM 33912), and (<b>f</b>) <span class="html-italic">Styxosaurus</span> sp. (AMNH 5835). Data taken from [<a href="#B4-diversity-16-00106" class="html-bibr">4</a>,<a href="#B8-diversity-16-00106" class="html-bibr">8</a>,<a href="#B15-diversity-16-00106" class="html-bibr">15</a>,<a href="#B19-diversity-16-00106" class="html-bibr">19</a>]. Diamond indicate individual vertebra, dotted line indicate vertebral length index = 100.</p> Full article ">Figure 5
<p>VLI of cervical region of plesiosauromorphs. (<b>a</b>) <span class="html-italic">Plesiosaurus dolichodeirus</span>; (<b>b</b>) <span class="html-italic">Microcleidus tournemirensis</span>; (<b>c</b>), <span class="html-italic">Seeleyosaurus guilelemiimperatosis</span>; (<b>d</b>) <span class="html-italic">Ophthalmothule cryostea</span>; (<b>e</b>) <span class="html-italic">Spitrasaurus wensaasi</span>; (<b>f</b>) <span class="html-italic">Spitrasaurus larseni</span>; (<b>g</b>) <span class="html-italic">Picrocleidus</span>; and (<b>h</b>) <span class="html-italic">Tricleidus seeleyi</span>. Data taken from [<a href="#B27-diversity-16-00106" class="html-bibr">27</a>,<a href="#B28-diversity-16-00106" class="html-bibr">28</a>,<a href="#B30-diversity-16-00106" class="html-bibr">30</a>,<a href="#B31-diversity-16-00106" class="html-bibr">31</a>,<a href="#B32-diversity-16-00106" class="html-bibr">32</a>,<a href="#B33-diversity-16-00106" class="html-bibr">33</a>]. Diamond indicate individual vertebra, dotted line indicate vertebral length index = 100.</p> Full article ">Figure 6
<p>VLI of cervical region of plesiosauromorphs: (<b>a</b>) <span class="html-italic">Abysossaurus nataliae</span>; (<b>b</b>) <span class="html-italic">Muraenosaurus leedsi</span>; and (<b>c</b>) <span class="html-italic">Brancasaurus brancai</span> [<a href="#B4-diversity-16-00106" class="html-bibr">4</a>,<a href="#B33-diversity-16-00106" class="html-bibr">33</a>,<a href="#B36-diversity-16-00106" class="html-bibr">36</a>]. Diamond indicate individual vertebra, dotted line indicate vertebral length index = 100.</p> Full article ">
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