Studies of the Iharkút fish-fauna

The studies of the Iharkút fish-fauna turned to be an unexpectedly informative segment of our researches. However, fish fossils have been unearthed since the first excavations at the Iharkút fossil site, their number and variability made their closer studies possible only for now. The two dominant fish taxa of the Iharkút vertebrate assemblage are lepisosteid fishes and pycnodontid fishes, both groups are represented by thousands of fossils. The fish-fauna of Iharkút is investigated by Márton Szabó, Péter Gulyás and Attila Ősi.

The Iharkút gar-material includes thousands of different remains. The ganoid scales, the plicidentine teeth, the opisthocoelous vertebrae, the various skull-elements and the supracleithrum represent the main parts of the body of the Iharkút gars. On the other hand, not all gar fossils helped us to study the taxonomical belonging of these fishes, but the scales, the teeth and the supracleithrum. Based on the features of these elements, we refer the material to the genus Atractosteus. However Atractosteus remains have been found earlier at several european Late Cretaceous fossil sites, their occurence in the Csehbánya Formation of Iharkút (and in the interdigitating Ajka Coal Formation, also Santonian in age) could be the oldest in Europe. The other main point of the material that it consist not only of teeth, scales and/or vertebrae, just like at most european localities. As an additional material, Martin Segesdi have found ganoid gar scales in some of the Iharkút coprolites. These finds could refer that these fishes have been preys for some other taxa at the locality.

The Iharkút Pycnodontiform-material includes lower jaws, vomers, hundreds of isolated teeth, a premaxilla or predentale, pharyngeal teeth and some scales. These fossils are similar to those of the genus Coelodus. Hopefully more Iharkút pycnodontid fossils will be unearthed in the future, which will let us identify these pycnodontids taxonomically closer.

Other, still unidentified fish fossils (teeth, pharyngeal teeth, scales and amphicoelous vertebrae) are also known from the Late Cretaceous Csehbánya Formation, however, this material is too fragmentary and poorly preserved for detailed studies.

Ancient ecosystem in the freshwaters of Iharkút (Graphic: Tibor Pecsics)
Ancient ecosystem in the freshwaters of Iharkút (Graphic: Tibor Pecsics)
Dentition of the extant Lepisosteus (upper) and Atractosteus (lower)
Dentition of the extant Lepisosteus (upper) and Atractosteus (lower)
Pannoniasaurus inexpectatus preys on an Atractosteus gar (graphic: Tibor Pecsics)
Pannoniasaurus inexpectatus preys on an Atractosteus gar (graphic: Tibor Pecsics)
Scanning electron micrograph of a ganoid gar-scale from Iharkút
Scanning electron micrograph of a ganoid gar-scale from Iharkút

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