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Lomax DR, de la Salle P, Perillo M, Reynolds J, Reynolds R, Waldron JF. The last giants: New evidence for giant Late Triassic (Rhaetian) ichthyosaurs from the UK. PLoS One 2024; 19:e0300289. [PMID: 38630678 PMCID: PMC11023487 DOI: 10.1371/journal.pone.0300289] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 02/24/2024] [Indexed: 04/19/2024] Open
Abstract
Giant ichthyosaurs with body length estimates exceeding 20 m were present in the latest Triassic of the UK. Here we report on the discovery of a second surangular from the lower jaw of a giant ichthyosaur from Somerset, UK. The new find is comparable in size and morphology to a specimen from Lilstock, Somerset, described in 2018, but it is more complete and better preserved. Both finds are from the uppermost Triassic Westbury Mudstone Formation (Rhaetian), but the new specimen comes from Blue Anchor, approximately 10 km west along the coast from Lilstock. The more complete surangular would have been >2 m long, from an individual with a body length estimated at ~25 m. The identification of two specimens with the same unique morphology and from the same geologic age and geographic location warrants the erection of a new genus and species, Ichthyotitan severnensis gen. et sp. nov. Thin sections of the new specimen revealed the same histological features already observed in similar giant ichthyosaurian specimens. Our data also supports the previous suggestion of an atypical osteogenesis in the lower jaws of giant ichthyosaurs. The geological age and giant size of the specimens suggest shastasaurid affinities, but the material is too incomplete for a definitive referral. Ichthyotitan severnensis gen. et sp. nov., is the first-named giant ichthyosaur from the Rhaetian and probably represents the largest marine reptile formally described.
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Affiliation(s)
- Dean R. Lomax
- Palaeobiology Research Group, School of Earth Sciences, University of Bristol, Bristol, United Kingdom
- Department of Earth and Environmental Sciences, The University of Manchester, Manchester, United Kingdom
| | - Paul de la Salle
- The Etches Collection – Museum of Jurassic Marine Life, Dorset, United Kingdom
| | - Marcello Perillo
- Paleontology division, Institute of Geosciences, University of Bonn, Bonn, Germany
| | | | | | - James F. Waldron
- Dinosaurs Will Always Be Awesome, DWABA Museum, Orlando, Florida, United States of America
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Miedema F, Bastiaans D, Scheyer TM, Klug C, Maxwell EE. A large new Middle Jurassic ichthyosaur shows the importance of body size evolution in the origin of the Ophthalmosauria. BMC Ecol Evol 2024; 24:34. [PMID: 38493100 PMCID: PMC10944604 DOI: 10.1186/s12862-024-02208-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 01/29/2024] [Indexed: 03/18/2024] Open
Abstract
The Middle Jurassic is an important time period for the evolutionary history of marine reptiles as it represented a transitional phase for many clades. Notably, in ichthyosaurs, many early parvipelvian taxa went extinct. The Middle Jurassic saw the emergence of the derived Ophthalmosauria, ultimately becoming the dominant ichthyosaurian clade by the end of the epoch. Even though this is an important period in the evolutionary history of Ophthalmosauria, our understanding remains limited in terms of morphology and taxonomy due to the scarcity of vertebrate-bearing strata. Here we present a large new ichthyosaur from the Bajocian of Switzerland, represented by an almost complete skull with 3D-preserved bones, the (inter)clavicles and a large portion of the postcranial skeleton. After CT- and surface scanning, we reconstructed the 3D in vivo morphology. Our morphological observations and phylogenetic analyses show that the new taxon named Argovisaurus martafernandezi is nested at the base of the Ophthalmosauria. The holotype and only known specimen of Argovisaurus likely represents an adult individual. Bajocian members of the Ophthalmosauria (Mollesaurus and Argovisaurus) were large-bodied animals, a trait typically associated with the more derived Platypterygiinae. This hints at the importance of a large body size early in ophthalmosaurian evolution.LSID: urn:lsid:zoobank.org:act:C3312628-1544-4B87-BBE3-B12346A30BE3LSID: urn:lsid:zoobank.org:act:23C2BD71-8CF0-4D99-848A-0D631518415B.
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Affiliation(s)
- Feiko Miedema
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, Stuttgart, 70191, Germany.
- Universität Zürich, Paläontologisches Institut, Karl Schmid-Strasse 4, Zürich, 8006, Switzerland.
| | - Dylan Bastiaans
- Universität Zürich, Paläontologisches Institut, Karl Schmid-Strasse 4, Zürich, 8006, Switzerland
- NHMB: Naturhistorisches Museum Basel, Augustinergasse 2, Basel, 4001, Switzerland
| | - Torsten M Scheyer
- Universität Zürich, Paläontologisches Institut, Karl Schmid-Strasse 4, Zürich, 8006, Switzerland
| | - Christian Klug
- Universität Zürich, Paläontologisches Institut, Karl Schmid-Strasse 4, Zürich, 8006, Switzerland
| | - Erin E Maxwell
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, Stuttgart, 70191, Germany
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Klug C, Spiekman SNF, Bastiaans D, Scheffold B, Scheyer TM. The marine conservation deposits of Monte San Giorgio (Switzerland, Italy): the prototype of Triassic black shale Lagerstätten. SWISS JOURNAL OF PALAEONTOLOGY 2024; 143:11. [PMID: 38450287 PMCID: PMC10912274 DOI: 10.1186/s13358-024-00308-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2023] [Accepted: 01/23/2024] [Indexed: 03/08/2024]
Abstract
Marine conservation deposits ('Konservat-Lagerstätten') are characterized by their mode of fossil preservation, faunal composition and sedimentary facies. Here, we review these characteristics with respect to the famous conservation deposit of the Besano Formation (formerly Grenzbitumenzone; including the Anisian-Ladinian boundary), and the successively younger fossil-bearing units Cava inferiore, Cava superiore, Cassina beds and the Kalkschieferzone of Monte San Giorgio (Switzerland and Italy). We compare these units to a selection of important black shale-type Lagerstätten of the global Phanerozoic plus the Ediacaran in order to detect commonalities in their facies, genesis, and fossil content using principal component and hierarchical cluster analyses. Further, we put the Monte San Giorgio type Fossillagerstätten into the context of other comparable Triassic deposits worldwide based on their fossil content. The results of the principal component and cluster analyses allow a subdivision of the 45 analysed Lagerstätten into four groups, for which we suggest the use of the corresponding pioneering localities: Burgess type for the early Palaeozoic black shales, Monte San Giorgio type for the Triassic black shales, Holzmaden type for the pyrite-rich black shales and Solnhofen type for platy limestones.
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Affiliation(s)
- Christian Klug
- Universität Zürich, Paläontologisches Institut, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
| | | | - Dylan Bastiaans
- Universität Zürich, Paläontologisches Institut, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
| | - Beat Scheffold
- Universität Zürich, Paläontologisches Institut, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
| | - Torsten M. Scheyer
- Universität Zürich, Paläontologisches Institut, Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland
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Miedema F, Bindellini G, Dal Sasso C, Scheyer TM, Maxwell EE. Ontogenetic variation in the cranium of Mixosaurus cornalianus, with implications for the evolution of ichthyosaurian cranial development. SWISS JOURNAL OF PALAEONTOLOGY 2023; 142:27. [PMID: 37810205 PMCID: PMC10556136 DOI: 10.1186/s13358-023-00289-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 08/27/2023] [Indexed: 10/10/2023]
Abstract
Relatively complete ontogenetic series are comparatively rare in the vertebrate fossil record. This can create biases in our understanding of morphology and evolution, since immaturity can represent a source of unrecognized intraspecific variation in both skeletal anatomy and ecology. In the extinct marine reptile clade Ichthyopterygia, ontogenetic series were widely studied only in some Jurassic genera, while the ontogeny of the oldest and most basal members of the clade is very poorly understood. Here, we investigate cranial ontogeny in Mixosaurus cornalianus, from the Middle Triassic Besano Formation of the Swiss and Italian Alps. This small-bodied taxon is represented by a wealth of material from multiple size classes, including fetal material. This allows us to assess ontogenetic changes in cranial morphology, and identify stages in the ontogenetic trajectory where divergence with more derived ichthyosaurs has occurred. Early ontogenetic stages of Mixosaurus show developmental patterns that are reminiscent of the presumed ancestral (early diverging sauropsid) condition. This is prominently visible in the late fetal stage in both the basioccipital, which shows morphology akin to basal tubera, and in the postorbital, which has a triradiate head. The ontogenetic trajectory of at least some of the cranial elements of Mixosaurus is therefore likely still very akin to the ancestral condition, even though the adult cranium diverges from the standard diapsid morphology. Supplementary Information The online version contains supplementary material available at 10.1186/s13358-023-00289-z.
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Affiliation(s)
- Feiko Miedema
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany
- Hohenheim University, Schloss Hohenheim 1A, 70599 Stuttgart, Germany
| | - Gabriele Bindellini
- Dipartimento di Scienze della Terra, Università degli Studi di Milano, Milan, Italy
- Dipartimento di Scienze della Terra, Sapienza Università di Roma, Rome, Italy
| | | | - Torsten M. Scheyer
- Universität Zürich, Paläontologisches Institut, Karl Schmid-Strasse 4, 8006 Zürich, Switzerland
| | - Erin E. Maxwell
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart, Germany
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Laboury A, Scheyer TM, Klein N, Stubbs TL, Fischer V. High phenotypic plasticity at the dawn of the eosauropterygian radiation. PeerJ 2023; 11:e15776. [PMID: 37671356 PMCID: PMC10476616 DOI: 10.7717/peerj.15776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2023] [Accepted: 06/29/2023] [Indexed: 09/07/2023] Open
Abstract
The initial radiation of Eosauropterygia during the Triassic biotic recovery represents a key event in the dominance of reptiles secondarily adapted to marine environments. Recent studies on Mesozoic marine reptile disparity highlighted that eosauropterygians had their greatest morphological diversity during the Middle Triassic, with the co-occurrence of Pachypleurosauroidea, Nothosauroidea and Pistosauroidea, mostly along the margins of the Tethys Ocean. However, these previous studies quantitatively analysed the disparity of Eosauropterygia as a whole without focussing on Triassic taxa, thus limiting our understanding of their diversification and morphospace occupation during the Middle Triassic. Our multivariate morphometric analyses highlight a clearly distinct colonization of the ecomorphospace by the three clades, with no evidence of whole-body convergent evolution with the exception of the peculiar pistosauroid Wangosaurus brevirostris, which appears phenotypically much more similar to nothosauroids. This global pattern is mostly driven by craniodental differences and inferred feeding specializations. We also reveal noticeable regional differences among nothosauroids and pachypleurosauroids of which the latter likely experienced a remarkable diversification in the eastern Tethys during the Pelsonian. Our results demonstrate that the high phenotypic plasticity characterizing the evolution of the pelagic plesiosaurians was already present in their Triassic ancestors, casting eosauropterygians as particularly adaptable animals.
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Affiliation(s)
- Antoine Laboury
- Evolution & Diversity Dynamics Lab, Université de Liège, Liège, Belgium
| | | | - Nicole Klein
- Institute of Geosciences, Paleontology, University of Bonn, Bonn, Germany
| | - Thomas L. Stubbs
- School of Life, Health & Chemical Sciences, Open University, Milton Keynes, United Kingdom
| | - Valentin Fischer
- Evolution & Diversity Dynamics Lab, Université de Liège, Liège, Belgium
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Miedema F, Klein N, Blackburn DG, Sander PM, Maxwell EE, Griebeler EM, Scheyer TM. Heads or tails first? Evolution of fetal orientation in ichthyosaurs, with a scrutiny of the prevailing hypothesis. BMC Ecol Evol 2023; 23:12. [PMID: 37072698 PMCID: PMC10114408 DOI: 10.1186/s12862-023-02110-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 03/21/2023] [Indexed: 04/20/2023] Open
Abstract
According to a longstanding paradigm, aquatic amniotes, including the Mesozoic marine reptile group Ichthyopterygia, give birth tail-first because head-first birth leads to increased asphyxiation risk of the fetus in the aquatic environment. Here, we draw upon published and original evidence to test two hypotheses: (1) Ichthyosaurs inherited viviparity from a terrestrial ancestor. (2) Asphyxiation risk is the main reason aquatic amniotes give birth tail-first. From the fossil evidence, we conclude that head-first birth is more prevalent in Ichthyopterygia than previously recognized and that a preference for tail-first birth likely arose in derived forms. This weakens the support for the terrestrial ancestry of viviparity in Ichthyopterygia. Our survey of extant viviparous amniotes indicates that fetal orientation at birth reflects a broad diversity of factors unrelated to aquatic vs. terrestrial habitat, further undermining the asphyxiation hypothesis. We propose that birth preference is based on parturitional mechanics or carrying efficiency rather than habitat.
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Affiliation(s)
- Feiko Miedema
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191, Stuttgart, Germany.
- Institut für Biologie, Fachgebiet Paläontologie, Hohenheim University, Wollgrasweg 23, 70599, Stuttgart, Germany.
| | - Nicole Klein
- Paläontologisches Institut, Universität Zürich, Karl Schmid-Strasse 4, Zurich, CH-8006, Switzerland
- Abteilung Paläontologie, Institut für Geowissenschaften, Universität Bonn, Nußallee 8, 53115, Bonn, Germany
| | - Daniel G Blackburn
- Dept. of Biology and Electron Microscopy Facility, Trinity College, Hartford, CT, 06106, USA
| | - P Martin Sander
- Abteilung Paläontologie, Institut für Geowissenschaften, Universität Bonn, Nußallee 8, 53115, Bonn, Germany
- Dinosaur Institute, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, CA, 90007, USA
| | - Erin E Maxwell
- Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191, Stuttgart, Germany
| | - Eva M Griebeler
- Institut für Organismische und Molekulare Evolution, Universität Mainz, Hanns-Dieter- Hüsch-Weg 15, 55128, Mainz, Germany
| | - Torsten M Scheyer
- Paläontologisches Institut, Universität Zürich, Karl Schmid-Strasse 4, Zurich, CH-8006, Switzerland
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Scheyer TM, Oberli U, Klein N, Furrer H. A large osteoderm-bearing rib from the Upper Triassic Kössen Formation (Norian/Rhaetian) of eastern Switzerland. SWISS JOURNAL OF PALAEONTOLOGY 2022; 141:1. [PMID: 35250843 PMCID: PMC8866377 DOI: 10.1186/s13358-022-00244-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 01/21/2022] [Indexed: 06/14/2023]
Abstract
An important component of the Alpine vertebrate record of Late Triassic age derives from the Kössen Formation, which crops out extensively in the eastern Alps. Here, we present an isolated and only partially preserved large rib, which carries an osteoderm on a low uncinate process. Osteological comparison indicates that the specimen likely belongs to a small clade of marine reptiles, Saurosphargidae. Members of the clade are restricted to the western (today Europe) and eastern margins of the Tethys (today China) and were so far known only from the Anisian stage of the Middle Triassic. The assignment of the new find to cf. Saurosphargidae, with potential affinities to the genus Largocephalosaurus from the Guanling Formation of Yunnan and Guizhou Provinces, China, would extend the occurrence of the clade about 35 million years into the Late Triassic.
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Affiliation(s)
- Torsten M. Scheyer
- Universität Zürich, Paläontologisches Institut und Museum, Karl Schmid-Strasse 4, CH-8006 Zürich, Switzerland
| | - Urs Oberli
- Waldgutstrasse 21, CH-9010 St.Gallen, Switzerland
| | - Nicole Klein
- Universität Zürich, Paläontologisches Institut und Museum, Karl Schmid-Strasse 4, CH-8006 Zürich, Switzerland
| | - Heinz Furrer
- Universität Zürich, Paläontologisches Institut und Museum, Karl Schmid-Strasse 4, CH-8006 Zürich, Switzerland
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Laboury A, Bennion RF, Thuy B, Weis R, Fischer V. Anatomy and phylogenetic relationships of Temnodontosaurus zetlandicus (Reptilia: Ichthyosauria). Zool J Linn Soc 2022. [DOI: 10.1093/zoolinnean/zlab118] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Abstract
Parvipelvia is a major clade of ichthyosaurians that diversified during the Triassic-Jurassic transition. The interrelationships of early parvipelvians remain unclear and many genera are loosely diagnosed, such as Temnodontosaurus, an ecologically important genus from the Early Jurassic of Western Europe. One taxon concentrates many taxonomic issues: ‘Ichthyosaurus’ acutirostris was previously assigned to Temnodontosaurus and for which ‘Ichthyosaurus’ zetlandicus represents a junior synonym. We redescribe the holotype of ‘Ichthyosaurus’ zetlandicus (CAMSM J35176) and a new specimen probably attributable to this taxon (MNHNL TU885) from the Toarcian of Luxembourg. We find that Temnodontosaurus zetlandicus comb. nov. is a valid species that should be referred to the genus Temnodontosaurus, sharing a number of traits with Temnodontosaurus nuertingensis and Temnodontosaurus trigonodon, despite having a distinct cranial architecture. Our phylogenetic analyses under both implied weighting maximum parsimony and Bayesian inference recover T. zetlandicus as closely related to several species currently assigned to Temnodontosaurus. Species included in Temnodontosaurus form a polyphyletic yet well-clustered group among basal neoichthyosaurians, demonstrating that the monophyly of this genus needs to be thoroughly investigated.
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Affiliation(s)
- Antoine Laboury
- Evolution & Diversity Dynamics Lab, University of Liège, 14 Allée du 6 Août, Liège 4000, Belgium
| | - Rebecca F Bennion
- Evolution & Diversity Dynamics Lab, University of Liège, 14 Allée du 6 Août, Liège 4000, Belgium
- Palaeontology Department, Royal Belgian Institute of Natural Sciences, 29, Rue Vautier, 1000 Brussels, Belgium
| | - Ben Thuy
- Palaeontology Departement, Natural History Museum Luxembourg, 25 Rue Münster, L-2160 Luxembourg, Grand-Duchy of Luxembourg
| | - Robert Weis
- Palaeontology Departement, Natural History Museum Luxembourg, 25 Rue Münster, L-2160 Luxembourg, Grand-Duchy of Luxembourg
| | - Valentin Fischer
- Evolution & Diversity Dynamics Lab, University of Liège, 14 Allée du 6 Août, Liège 4000, Belgium
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Miedema F, Maxwell EE. Ontogenetic variation in the skull of Stenopterygius quadriscissus with an emphasis on prenatal development. Sci Rep 2022; 12:1707. [PMID: 35105895 PMCID: PMC8807662 DOI: 10.1038/s41598-022-05540-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 12/16/2021] [Indexed: 12/03/2022] Open
Abstract
The availability of a large sample size from a range of ontogenetic stages makes Stenopterygius quadriscissus a good model to study ontogenetic variation in a fossil sauropsid. We qualitatively examined pre- and postnatal ontogenetic changes in the cranium of S. quadriscissus. The prenatal ossification sequence is similar to other diapsids, exhibiting delayed chondrocranial ossification compared to the dermatocranium. In the dermatocranium, the circumorbital area is more ossified earlier in development relative to other elements, especially those of the skull roof where ossification is comparatively weaker across prenatal stages. Perinatally all cranial elements are ossified, and many scarf and step joints are already closed. We propose four prenatal and three postnatal stages in S. quadriscissus on the basis of relative ossification, size and qualitative cranial characters pertaining to the jugal, parietal, frontal, pterygoid and surangular. These will provide a basis for determining ontogenetic stages in other ichthyosaurs. Moreover, our postnatal observations aid in refining ontogenetic characters for phylogenetic studies. Lastly, we observed that the antimeric sutures of the midline of the skull roof are open perinatally and that fusion of the midline only appears in the adult stage. We hypothesize that the loose connection of the midline functions as a fontanelle, limiting potential damage during birth.
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Affiliation(s)
- Feiko Miedema
- Staatliches Museum Für Naturkunde Stuttgart, Rosenstein 1, 70191, Stuttgart, Germany.
- Department of Paleontology, Hohenheim University, Schloss Hohenheim 1 A, 70599, Stuttgart, Germany.
| | - Erin E Maxwell
- Staatliches Museum Für Naturkunde Stuttgart, Rosenstein 1, 70191, Stuttgart, Germany
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