Pannoniasaurus
| Pannoniasaurus | ||||||||||||
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The holotype (MTM 2011.43.1.) Of Pannoniasaurus inexpectatus . Right square in different views (length of the scale bar: 1 cm). |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous , Santonium | ||||||||||||
| 86.3 to 83.6 million years | ||||||||||||
| Locations | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Pannoniasaurus | ||||||||||||
| Makádi et al., 2012 | ||||||||||||
| Art | ||||||||||||
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Pannoniasaurus is a genus of Mosasauroidea from the subgroup of Tethysaurinae . The only known species of the so far monotypical genus is Pannoniasaurus inexpectatus from the Santonium (approx. 86.3 to 83.6 million years ago) of Hungary . Pannoniasaurus inexpectatus is considered the first reliable evidence of a representative of the Mosasauroidea that lived exclusively in fresh water.
Etymology and history of research
The generic name is derived from the name of the Roman province of Pannonia from whose former area the finds originate, and the Latinized ancient Greek word σαῦρος sauros - "lizard", "salamander". The additional species “ inexpectatus ” (Latin for “the unexpected”) refers to the unexpected appearance of a mosasaur in a freshwater habitat .
Already in 2000, was on a slag heap of Ajka of the vertebrae (MTM V.2000.21.) A large coalfield scales lizard found. The find could be assigned to the deeper parts of the Ajka coal formation. A more precise palaeontological or stratigraphic assignment was not possible and the piece was initially thought to be the vertebra of a monitor lizard . Corresponding finds from the almost simultaneous Csehbánya Formation from the Iharkút bauxite opencast mine in Veszprém County followed later .
Even before the first description, extensive geochemical analyzes and studies of the oxygen isotype of the fossil material from the Csehbánya Formation were published in 2009, which confirmed a freshwater habitat as a habitat for Pannoniasaurus .
It was first described in 2012 by Makádi , Caldwell and Ősi . At the same time, Pannoniasaurus was added to the newly established group of Tethysaurinae within the Mosasauroidea together with Yaguarasaurus , Tethysaurus ( type genus ) and Russellosaurus .
In 2015, Garcia et al. from a similar find from continental deposits of the early Campanium in southern France. The authors also assign their find to a freshwater living representative of the Tethysaurinae . However, due to the fossil material, it was not possible to further classify the species at the generic or even species level. Pannoniasaurus inexpectatus is still the first undoubted evidence of a representative of the Mosasauroidea in a freshwater habitat.
Fossil record
The lost material from the bonebed the Csehbánya formation of Iharkút comprises over 100 individual bones of several individuals of different sizes. The specimens are kept at the Hungarian Natural Science Museum (Magyar Természettudományi Múzeum - MTM) in Budapest . A single right square (MTM 2011.43.1.) Was set as the holotype .
features
With a length of up to 6 m, Pannoniasaurus was a medium-sized representative of the Mosasauroidea with a flattened, crocodile-like head. Paddle-shaped limbs are likely, but not supported by fossil records. The following autapomorphies are listed for genus and type species :
Cranial skeleton
To make it easier to understand, the names of the respective partial figures (C – M) are shown in brackets on the right.
- The stapedial pit of the quadratum (F), i.e. the connection point to the stapes , has a length-to-width ratio of 3: 1,
- The square shows a saddle-shaped joint connection to the lower jaw.
- The elongated, narrow shaft of the quadratum lies distal to the shell- shaped main body (English " conch ") and to the infrastapedial process of the quadratum.
- The wing-shaped infrastapedial process of the quadratum is large and the suprastapedial process is elongated with a medially beveled tip.
- The premaxilla (C) is flattened dorsoventrally , laterally widened and, in its dorsal view, resembles the shape of a violin .
- The coronoid (J), that single bone in the lower jaw of reptiles which the crown extension (coronoid) corresponds to the lower jaw bones of mammals, wearing a long Dorsalfortsatz.
- The teeth (H) are conical and curved backwards inwards (posterolingual), with undulating longitudinal grooves (“striae”), a distinct, mesial and a less distinct, labiodistal cutting edge (“carina”).
Postcranial skeleton
- The hypapophyses , ventral (“abdominal”) processes on the vertebral body, show a circular joint surface
- The cervical vertebrae have two strong bone ridges on the side of the abdomen ("ventrolateral").
- The individual vertebrae of Pannoniasaurus are, like most reptiles, procoel, ie the vertebral body has an indentation anteriorly (at the end directed towards the head) as a joint pit; posterior , at the end facing the tail, but a bulge as a corresponding joint head. In all vertebrae, apart from the caudal vertebrae, the latter is clearly separated from the actual vertebral body by a constriction at the base.
- Two openings (“Paracotylare Foramina”) located apart from the joint pit (“Cotyla”) on the front (anterior) of the vertebrae are missing in Pannoniasaurus .
- Parazygosphenal foramina, two similar openings on the back (posterior) of the vertebrae, slightly apart from the zygosphere-zygantrum joint , are also absent.
- The rib heads are oval.
Systematics
Makádi et al. (2012) combine Pannoniasaurus with Yaguarasaurus , Tethysaurus and Russellosaurus to clade of Tethysaurinae . Tethysaurus is defined as the type genus . The systematic position within the Mosasauroidea is left open (" incertae sedis "). The Tethysaurinae themselves are defined as "the last common ancestor of Pannoniasaurus inexpectatus and Russellosaurus coheni and all its descendants." This means, as Madzia & Cau also criticized in 2017, that the type genus of the Tethysaurinae is not included in their definition and this is therefore strict taken, does not comply with the rules of the ICPN (Article 11.7).
Already in 2013 the clade of the Tethysaurinae was published by Palci et al. based on the first description of the genus Romeosaurus split again into the Tethysaurinae ( Pannoniasaurus + Tethysaurus ) and their sister group, the Yaguarasaurinae (the last common ancestor of Yaguarasaurus , Russellosaurus and Romeosaurus and all of its descendants).
In 2017 this subdivision was adopted into two more comprehensive analyzes of the Mosasauroidea system. Simões et al. find both Tethysaurinae and Yaguarasaurinae as clearly monophyletic sister groups in the vicinity of the clades Plioplatecarpinae and Tylosaurinae , i.e. clearly within the Mosasauridae , but apart from the Mosasaurinae . In relation to Pannoniasaurus, however, this work shows some peculiarities; so is z. For example, there is general talk of “ Pannoniasaurus osii ”, a taxon that does not exist at all and, curiously, the reference list does not refer to the first description by Makádi et al. (2012), but rather to the above-mentioned geochemical analyzes by Kocsis et al., 2009. Madzia & Cau, 2017 essentially use the same data set for their analysis, correcting the above-mentioned inadequacies and performing multiple calculations with different methodological approaches. This shows that the Tethysaurinae remain stable as a monophyletic group, but, depending on the calculation method, change their systematic position within the Mosasauroidea strongly and can sometimes fall out of the Mosasauridae group.
A position of the Tethysaurinae and thus also of Pannoniasaurus within the Mosasauridae can be assumed, but is obviously not proven with certainty. Thus, in the sense of Makádi et al. (2012) assumed a position “ incertae sedis ” within the Mosasauroidea .
Paleecology
A way of life is assumed for Pannoniasaurus , which is essentially similar to that of today's river dolphins .
During the Upper Cretaceous Period, Central Europe consisted of a collection of larger and smaller, largely isolated islands ("European Cretaceous Archipelago"). The alluvial sediments of Csehbánya lineup was one of the larger of these islands in a lowland hem alluvial plain deposited. Further towards the coast, the alluvial plains merged into the freshwater swamps and lakes of the Ajka coal formation. Both habitats probably corresponded to the habitat of Pannoniasaurus .
The findings from France indicate that freshwater-dwelling representatives of the Mosasauroidea were not a local isolated case, but a more widespread component of the continental ecosystems of the European Cretaceous archipelago in the Upper Cretaceous.
Individual evidence
- ↑ a b c J. Kocsis, A. Ősi, T. Vennemann, CN Trueman & MR Palmer: Geochemical study of vertebrate fossils from the Upper Cretaceous (Santonian) Csehbánya Formation (Hungary): Evidence for a freshwater habitat of mosasaurs and pycnodont fish . In: Palaeogeography, Palaeoclimatology, Palaeoecology , Vol. 280, pp. 532–542, 2009. (Abstract)
- ↑ a b c d e f g h L. Makádi, MW Caldwell & A. Ősi: The First Freshwater Mosasauroid (Upper Cretaceous, Hungary) and a New Clade of Basal Mosasauroids In: PLOS ONE , Vol. 7, No. 12, e51781. doi : 10.1371 / journal.pone.0051781 .
- ^ A b G. Garcia, N. Bardet, A. Houssayec, X. Pereda-Suberbiola & X. Valentin: Mosasauroid (Squamata) discovery in the Late Cretaceous (Early Campanian) continental deposits of Villeveyrac-L'Olivet, southern France. In: Comptes Rendus Palevol , Vol. 14, pp. 495–505, 2015. (digitized version )
- ^ A b D. Madzia & A. Cau: Inferring `weak spots' in phylogenetic trees: application to mosasauroid nomenclature. In: PeerJ , 5: e3782; doi : 10.7717 / peerj.3782
- ↑ Ph. D. Cantino & K. de Queiroz: PhyloCode - International Code of Phylogenetic Nomenclature - Version 4c. 102 p., International Society for Phylogenetic Nomenclature, 2010. (digitized version)
- ↑ A. Palci, MW Caldwell & CA Papazzoni: A new genus and subfamily of mosasaurs from the Upper Cretaceous of northern Italy. In: Journal of Vertebrate Paleontology , Vol. 33, No. 3, pp. 599-612, 2013. doi : 10.1080 / 02724634.2013.731024
- ↑ TR Simões, O. Vernygora, I. Paparella, P. Jimenez-Huidobro & MW Caldwell: Mosasauroid phylogeny under multiple phylogenetic methods provides new insights on the evolution of aquatic adaptations in the group. In: PLoS ONE , Vol. 12, No. 5, e0176773. doi : 10.1371 / journal.pone.0176773 .
- ↑ a b Z. Csiki-Sava, E. Buffetaut, A. Ősi, X. Pereda-Suberbiola & St. L. Brusatte: Island life in the Cretaceous - faunal composition, biogeography, evolution, and extinction of land-living vertebrates on the Late Cretaceous European archipelago. In: ZooKeys. Vol. 469, 2015, pp. 1–161, doi: 10.3897 / zookeys.469.8439
- ↑ G. Botfalvai, J. Haas, ER Bodor, A. Mindszenty & A. Ősi: Facies architecture and palaeoenvironmental implications of the upper Cretaceous (Santonian) Csehbánya formation at the Iharkút vertebrate locality (Bakony Mountains, Northwestern Hungary) In: Palaeogeography, Palaeoclimatology, Palaeoecology , Vol. 441, Part 4, pp. 659-678, 2016. (Abstract) ; (Manuscript version)
