Ajkaceratops
| Ajkaceratops | ||||||||||||
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The holotype (MTM V2009.193.1) of Ajkaceratops kozmai in a side view, rostral (left) and premaxilla (right). The central upper indentation corresponds to the lower part of the outer nostril, the indentation on the right corresponds to the front part of the “additional window” between the premaxillary and maxilla (length of the scale bar: 1 cm). |
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| Temporal occurrence | ||||||||||||
| Upper Cretaceous , Santonium | ||||||||||||
| 86.3 to 83.6 million years | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Ajkaceratops | ||||||||||||
| Ősi et al., 2010 | ||||||||||||
| Art | ||||||||||||
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Ajkaceratops is a genus of ceratopsians from the coronosauria group . The only known species of the so far monotypical genus is Ajkaceratops kozmai from the Santonium (approx. 86.3 to 83.6 million years ago) of Hungary . Ajkaceratops is considered to be the first reliable record of a representative of Ceratopsia in Europe.
Etymology and history of research
The generic name refers to the Hungarian city of Ajka , in the vicinity of which the remains of Ajkaceratops were found, in combination with the ending " -ceratops ", which is often used by representatives of the Ceratopsia , from ancient Greek κέρας , kéras - "horn" and ὤψ , ōps - "eye", "face". The additional species " kozmai " honors the Hungarian geologist Károly Kozma . The species name can accordingly be translated as "Kozma's horn face of Ajka".
The remains of Ajkaceratops kozmai come from the so-called Csehbánya Formation from the Iharkút bauxite open- cast mine in Veszprém County and were first identified in 2010 by Ősi et al. described. Ajkaceratops kozmai is therefore the first undoubted evidence of a representative of Ceratopsia in Europe. Earlier discovery reports from other European sites were considered dubious and most experts agreed that the geographical distribution of Ceratopsia was limited to North America and East Asia.
In 2015, Csiki-Sava et al. in a more comprehensive analysis a possible explanation for the occurrence of ceratopsians in Europe.
Fossil record
The previously existing fossil material of Ajkaceratops kozmai is the Hungarian Science Museum in (Magyar Természettudományi Múzeum) Budapest stored and includes only a fragment of the rostrum ( holotype MTM V2009.193.1) and 4 Prädentalia , under the assumption that at the same time in this field, only a Species from the group of Ceratopsia occurred, also Ajkaceratops kozmai can be assigned. The holotype consists essentially of the rostral , nor in conjunction with fragments of the edentulous premaxilla and the rostral extension of the maxilla .
An analysis of the wear marks on the teeth of the small ornithopod Mochlodon vorosi , which also occurs in the Csehbánya Formation, has shown that a few teeth, which were originally interpreted as lower jaw teeth by Mochlodon , show significantly different wear patterns. Teeth, which can be clearly assigned to the genus Mochlodon , show straight, almost parallel welts and scratches on their worn surfaces, which indicate a largely local (vertical, parallel to the sagittal plane ) jaw movement. In the case of teeth with a deviating pattern, on the other hand, the wear surfaces show approximately concentrically arranged, arc-shaped traces, which speak for a simultaneous combination of orthal and palinal (horizontal, parallel to the sagittal plane) jaw movement during the chewing process. Such a circumpalinale chewing movement is unknown by representatives of the Ornithopoda, but has been found in some representatives of the Neoceratopsia . Since the teeth of ornithopods and ceratopsians can be very similar in shape, the authors of this study suspect that the teeth with circumpalinal wear patterns could be fossil evidence of Ajkaceratops .
features
Despite the only fragmentary fossil evidence, Ősi et al. (2010) consider some essential features:
- A rostral bone curved like a parrot's beak ,
- a strongly domed roof of the palate of the premaxilla and
- a ventral ("abdominal side") located, clear appendage on the very likely associated predentalia
prove the affiliation to the Ceratopsia .
- An additional, oval skull opening (" accessory fenestra ") between the maxilla and premaxilla , clearly delimited from the outer nostril,
indicates a relationship with the Coronosauria within the Ceratopsia .
The following are considered autapomorphic characteristics of the genus Ajkaceratops :
- The part of the premaxilla lying on the abdomen ( ventral ) to this additional skull window is flattened dorsoventrally;
- A “caudolateral” extension of the premaxilla that starts laterally at the rear is curved and oriented approximately horizontally at its end;
- The outer margins of the probably associated predentalia are sharply delimited and not beveled.
Due to the dimensions of the skeletal elements found so far, Ősi et al. (2010) assume that the individuals of Ajkaceratops found so far reached a maximum body length of only about 1 m. Ajkaceratops would be a very small representative of the Coronosauria . The authors emphasize that it is not possible to estimate the individual age on the basis of the available fossil material, but also point out that there are no signs of youth. Ajkaceratops was possibly actually a dwarf form of the Coronosauria.
Paleecology
Ajkaceratops was, like all other representatives of the Ceratopsia , a quadruped herbivore .
During the Upper Cretaceous Period, Central Europe essentially consisted of a collection of larger and smaller, largely isolated islands ("European Cretaceous Archipelago"). The sediments of the Csehbánya Formation were deposited in the lowland fringes of one of the larger of these islands in an alluvial plain , which is essentially also the habitat of Ajkaceratops .
As already mentioned by Ősi et al. (2010) indicated, for Ajkaceratops paleobiogeographical an influx from the East Asian region, from island to island, and, with regard to its size, a case of island dwelling.
Individual evidence
- ↑ a b c d e f A. Ősi, RJ Butler & DB Weishampel: A Late Cretaceous ceratopsian dinosaur from Europe with Asian affinities. In: Nature. Vol. 465, No. 7297, 2010, pp. 466-468, doi: 10.1038 / nature09019 ( alternative PDF link ), Supplementum
- ↑ a b c 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
- ↑ FJ Varriale: Dental microwear reveals mammal-like chewing in the neoceratopsian dinosaur Leptoceratops gracilis. In: PeerJ , Volume 4, 2016, e2132, doi : 10.7717 / peerj.2132 .
- ↑ A. Virág & A. Ősi: Morphometry, Microstructure, and Wear Pattern of Neornithischian Dinosaur Teeth From the Upper Cretaceous Iharkút Locality (Hungary). In: The Anatomical Record - Advances in Integrative Anatomy and Evolutionary Biology , Volume 300, Number 8, 2017, pp. 1439–1463, doi : 10.1002 / ar.23592 .
