 |
| Coneroichnus marinus Natali & Leonardi, 2023 Art by Marco Astracedi. |
Abstract
An uncommon ichnofossil, constituted of a sequence of eleven imprints, named as Coneroichnus marinus ichnog. et ichnosp. nov., is described from Mount Conero, Province of Ancona, Italy. The trackway is impressed in whitish micritic limestone of the Maiolica Formation (Upper Jurassic–Lower Cretaceous), herein interpreted as the passage on the sea bottom of a marine reptile, softly interfering in the sediment-water interface. Its gait can be defined as half-swimming, that is the swimming in exploratory and punting propulsive contact with the mud at the bottom. We discuss the probable trackmaker and we suggest it was probably a pliosaurid Plesiosauria. The extreme rarity of ichnofossils of tetrapods on the deep-sea bottom in the whole world is herein confirmed.
Keywords: Early Cretaceous, Coneroichnus marinus ichnog. et ichnosp. nov., pelagic reptile trackway.
 |
| The image shows marine reptiles of the order Plesiosauria, on the seabed of the Tethys Ocean. The plesiosaur shown here in the foreground, together with the one on the left, is inspired by Leptocleidus, a short-necked plesiosaur, as an example of the supposed author of the trackway under study. In the background on the right side, one sees another plesiosaurid: Brancasaurus, a typical long-necked plesiosaur, another hypothetical author of the trackway. Art by Marco Astracedi. |
CONCLUSIONS:
In the present paper we have allocated from an ichnotaxonomical and ichnological point of view a trackway, from deep pelagic environment, on the seabed of the Tethys Ocean, which then became a limestone bank of the Maiolica Formation, of the Berriasian–Hauterivian, Early Cretaceous of Mount Conero (Sirolo, Marche, Italy). We have updated the most likely stratigraphic position of the outcrop bearing the sequence of tracks;we have assigned to them the name of Coneroichnus marinus ichnog. et ichnosp. nov.
We concluded that its gait can be defined as the half-swimming manner of gait, that is the exploratory and propulsive contact swimming with the mud saturated with water on the bottom. Since this kind of underwater progression happens, in this specific case, in contact with the sea bottom, it was here also defined as a punting and foraging manner of gait.
Only two other tracksites with tracks attributed to fossil marine reptiles had been so far found in sediments from the deep seabed paleoenvironment, not only in Italy, but in the entire world. Mount Conero is the third ichnosite in the world with deep-marine fossil trackways. It will be useful to carry out more intense research along all the outcrops of Maiolica at Mount Conero and along the Adriatic Sea, but also in other areas, on tabular surfaces of layers not too eroded, looking for other specimens of marine reptile tracks like these or similar to them.
Luca Natali and Giuseppe Leonardi. 2023. Coneroichnus marinus ichnogenus et ichnospecies nov., A Fossil Trackway of Marine Reptile in the Maiolica Formation (Upper Jurassic–Lower Cretaceous) from Monte Conero, Marche, Italy. Revista Brasileira De Paleontologia. 26(3), 156–171. DOI: 10.4072/rbp.2023.3.02
RESUMO – Um raro icnofóssil, ou seja, uma sequência de onze impressões em micrite calcária da Formação Maiolica (Jurássico Superior–Cretáceo Inferior), é aqui nomeado como Coneroichnus marinus ichnog. et ichnosp. nov. sendo detalhadamente descrito. A pista se encontra no Monte Conero, na Província de Ancona, Itália. Ela é atribuída à passagem sobre o fundo do mar de um réptil marinho, o qual deformou a superfície na interface sedimento-água. Seu deslocamento pode ser definido como semi-natação, que corresponde a uma natação de caráter exploratório e propulsivo em contato com a lama do fundo. Discute-se o produtor desta pista, possivelmente um pliosaurídeo Plesiosauria. A extrema raridade de icnofósseis de tetrápodes no substrato marinho profundo em todo o mundo é confirmada.
Palavras-chave: Cretáceo Inferior, Coneroichnus marinus ichnog. et ichnosp. nov., pista de um réptil pelágico.
