7 maj 2021

The first tetrapods - earlier than scientists thought. Zachełmie, Poland.

 

Link to this video on youtube https://www.youtube.com/watch?v=Oi8SFw1hOd4

Location GPS of Zachełmie

50°58'09.4"N 20°41'21.4"E

(50.969270, 20.689287) 

 

Text from the video

Back in February, during the winter everyone was waiting for, I managed to catch the moment when the Geological Museum in Warsaw was open. The only way not to turn into an icicle was to come over before they opened the museum that day. After queuing for some time, you could finally begin your tour. And so, while wandering around the great hall, still blowing on my cold hands, I noticed quite interesting creatures behind the popular Dyzio. Of course! After all, the historic moment when the fish came out of water took place near Kielce. In addition, earlier than the scientific world has so far thought, and the animals I’m looking at are the famous tetrapods from the quarry in Zachełmie. They walked here and there 390 million years ago, leaving traces.

Millennia passed and one fine day Polish scientists discovered these traces. The publication in Nature didn’t go unnoticed. Paleontologists Philippe Janvier and Gaël Clément compared the discovery in Zachełmie to throwing a grenade into the current picture of transforming fish into tetrapods. This drawing can tell you a bit about what's going on. Although it has an original, slightly more distant dating, it doesn’t really matter here. So - looking at the tetrapods, I thought that although I already mentioned Zachełmie in one of my videos in Polish language, this matter requires the whole episode.

Paleozoic Era. According to the Wikipedia, it is an era in the geological history of the Earth, which lasted from about 540 million to about 250 million years ago. Its name comes from the Greek words: palaiós - old, ancient, zóon - animal. The Palaeozoic Era is divided into 6 periods: Cambrian, Ordovician, Silurian, Devonian, Carboniferous, Permian.

We are interested in Devonian. The devonian period lasted about 60 million years, from 419.2 to 358.9 million years ago. In that time Zachełmie was here. The Devonian climate was warm and dry, and near Kielce it was almost subtropical. There was 15% oxygen in the atmosphere, the average temperature on Earth was 20 ° C. Sea level was relatively stable for most of the period and was 180 meters higher than it is today. Reefs flourished in the seas, creating the largest reef structures in the history of the Earth. The devonian is also called the age of fish. Among them, jawless fish are common, and also armored fish that are at the peak of their development. Fossils of three armored fish – dunkleosteus were discovered In the village Płucki in the Świętokrzyskie region. The head of the largest one was over 60 cm, and the whole specimen was about 6-7 m long. The 5-meter specimen was the most complete. It is estimated that these fish could reach up to 20 m. Dunkleosteuses were predators - but they had no teeth. Instead, their jaws were equipped with sharp and, additionally, self-sharpening edges, which rubbed against each other and sharpened each other with each closing of their mouths. It seems that after reaching several meters in length, these fish did not have many enemies - they ruled the food pyramid.

In addition to armored fish, the Devonian bony fish developed, including fossils of lobe-finned fish and lungfish from this era. Initially, these fish lived in the seas and later also in freshwater. Bony fish are currently the most numerous group, they constitute 95% of fish alive today. Examples of fish in this group are trout, carp, cod, mackerel. In the Middle Devonian, cartilaginous fish also appeared, such as rays and sharks.

In the Devonian, land colonization is already clearly visible. Although the origins of terrestrial plants disappear into the abyss of scientists' discussions, we can say with a high degree of certainty that in the Devonian there are more and more bryophytes on land, then the club moss plants appear, followed by ferns and horsetails.

The specimens you are looking at come from the exhibition in the Geological Museum in Warsaw. In the Lower Devonian sandstones from the vicinity of Kostomłoty in the Świętokrzyskie Mountains, fossilized plant roots have been preserved. They occur in sediments of shallow-sea origin, hence the conclusion that these plants grew at the partially flooded shore and covered coastal swamps. The large thickness of the sediments with roots and their mutual overgrowth prove that these were not the first timid and rickety plants. On the contrary - they were already well-established there.

Next, forest-like plant accumulations gradually developed on the land. Some species were up to 30 meters high. Deep root systems stabilized the soil, and organic compounds produced by plants caused faster chemical weathering of the rocks. The thriving vegetation absorbed huge amounts of carbon dioxide, which resulted in a decrease of the amount of this gas in the atmosphere, and the oxygen produced by plants caused a gradual increase in the amount of it. Increasingly lush vegetation began to facilitate the development of land herbivores.

Well, but I've come a little too far. Let's go back to 390 million years before our time, and even 393 million years before today. This clarification comes from a lecture by Dr. Grzegorz Niedźwiedzki on the Copernicus Center for Interdisciplinary Studies channel on youtube. So those 393 million years ago, 7 to 10 million years earlier than was thought so far, early tetrapods walked on the site of the present quarry in Zachełmie. There were periodic muddy lakes around, probably also a lagoon and the vast shallows of the nearby sea. These conclusions can be drawn by studying isotopes, fossil deposits and microfossils. As we already know, the climate was warm, and the sea water temperature was around 30 ° C. At the reconstruction in the Geological Museum, one of the tetrapods intends to eat some shrimps, because traces of crustaceans similar to shrimps were also found in Zachełmie. However, I don’t know if it is possible to determine what our tetrapods actually ate. Who knows, maybe they also liked to nibble on some greens? Although palaeopedological data suggest that the vegetation around was pour, there were some moisture-loving herbaceous plants and small shrubs. In the soil where these plants grew, small crustaceans dug burrows, what in the fossil record takes such appearance.

No animal bones were found in Zachełmie because, as noted by Dr. Grzegorz Niedźwiedzki, the environmental conditions of the Zachełmie region weren’t conducive to the preservation of these. So there only tracks and trackways are left - and it's nice that they are preserved. The reconstructions of animals themselves are probably some kind of approximation.

The best preserved digit is quite large. It shows fingerprints and structures resembling hand or foot pads. This allowed the paw to be reconstructed. Based on the footprints and the spacing of the tracks, it was estimated that the tetrapods could measure up to 2.5 m in length. The features of the petrified environment and its location in the landscape suggest that the traces were left by wading animals. In the quarry in Zachełmie, single, large digits were also found, interpreted as made by swimming tetrapods, catching the ground. The same features of the environment indicate that the tetrapods must also be able to move outside water habitats.. Of course, this also doesn’t exclude the possibility of getting food directly on land.

The quarry, where the traces of the first tetrapods were found, is a very nice, relaxing place. It is worth visiting for its beauty alone. The traces of the tetrapod are in the background, looking from the entrance to the quarry, and you should definitely look at them, although the most expressive ones were transferred to the Geological Museum in Warsaw. The quarry in Zachełmie doesn’t mean only traces of tetrapods. For example, on the southern walls are spectacular fossilized cracks associated with the periodic drying of the land in the Devonian and stromatolites, which are calcareous laminated structures that owe their formation to single-celled, thread-like cyanobacteria growing on the seabed, and also structures recognized by researchers as a relic of Devonian rains. The Permian and Triassic rock formations are also very picturesque. In addition, you do not need a specialist to find all these attractions, because there are information boards next to them. 

 

Bibliography


Zachełmie, Poland. Devonian beach and stromatolites

 

Zachełmie, Poland. Devonian beach and stromatolites.
 
 
Zachełmie, Poland. Dried Devonian periodic lakes.
 
Traces of tetrapod in Zachełmie.
 
Trackway of tetrapod in Zachełmie, Poland.
 
Trackway of tetrapod. Geological Museum in Warsaw
 
Paw digit of tetrapod from Zachełmie. Geological Museum in Warsaw.
 

 


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