Fish conquered the deep sea 130 million years ago Lower Cretaceousaccordingly Youfossil races occurring in the northern Apennines, bringing their appearance in these areas forward by about 80 million years.
So far, the fossils of deep-sea fish are 50 million years old. magazine PNAS publishes, with Spanish participation, a study on the existence of fossilized tracks left by various species of fish when feeding or moving.
The research is based on fossil or imfossil traces, not on direct body remains of the fish (such as bones, teeth or scales), they explain to Efe Zain Belausteguifrom the University of Barcelona, and Fernando Muniz from the University of Seville, both signatories to the study.
The ichnofossils are interpreted as different types of tracks, primarily food and locomotion tracks, that are “most likely left by different species of fish in the bottom sediments of a deep-sea environment,” they point out.
These fossilized “footprints” represent the earliest evidence of vertebrate life on the ocean floor, according to the research team led by Andrea Baconfrom the University of Genoa (Italy).
Limestones of the Northern Apennines
The fossils are preserved in limestone from the northern Apennines, where low-lying plain deposits from the Tethys Ocean existed between the ancient continents of Gondwana and Laurasia.
The team identified trace fossils in the shape of holes and groovesand suggests they may have been produced by three different types of fish.
The first was a toothless neoteleost, the second a chimera-like fish — which would have produced two different types of food tracks — and a possible third fish with a large caudal fin that would have left the tracks identified as locomotion, indicate Muñiz and Belaustegui . .
Comparison with current analogues
One of the tools of ichnology It is based on a comparison with current analogues. As more information becomes available about the tracks that different types of organisms produce when they interact with different types of substrates, more resources will become available for the interpretation of ichnofossils.
In this case, there is evidence of the existence of different species of fish as early as 130 million years ago similar anatomical features to those currently being observed, and that may have left traces similar to those we can see today.
For this research, the current traces were studied in different locations in Italy, in the Piedras River estuary (Huelva) and with underwater recordings at a depth of 1,544 meters in the Kermadec Trench (Pacific).
Muñiz and Belaustegui are ichnologists and their work in this study focused on identifying and interpreting these fossil records. The results suggest that vertebrates colonized the deep sea in the early Cretaceous and that this transition may have been due to increased food sources rather than a change in deep sea oxygen levels.
In addition, they suggest that the Lower Cretaceous abysses already represented a modern deep-sea ecosystem characterized by aggregations of various fish species.