Like a modern lobster that lived hundreds of million years ago, trilobites were able to gather in groups and go on a journey together at the bottom of ancient oceans. To such conclusion came the Polish paleontologists, after studying dozens of fossils of trilobites, lined up in chains for each other.
As the trilobite not to lose ahead of crawling companion in the murky waters of the Devonian sea, and will he have enough gumption to travel close friendly team, said the doctor of biological Sciences, leading researcher of the laboratory of ancient organisms Paleontological Institute. A. borisyak studies Elena B. Naimark
A group of Polish paleontologists from the Institute of paleobiology Polish Academy of Sciences a few years ago examined in the mountains of Central Poland interesting layers, which kept a lot of whole shells of trilobites, and these whole shells were located in chains for each other. And such chains are long and not very found in different layers as much as 78. It is clear that this is not just post-mortem congestion, and an example of orderly conduct, which has been demonstrated in animals, the age of which 365 million years.
Further research led Blazer Blazejowski from the same Institute of paleobiology: he decided to look closer at this fossil behavior, suggesting that trilobite chain gathered is not random. Rather, they represent the marching columns like modern arthropods, which move to the mating or egg laying.
These findings, indeed, not uncommon, we are aware of similar columns of trilobites from the sediments of the Ordovician of Portugal and Morocco, – says Elena Naimark, for example, in Morocco, found a chain of hundreds of trilobites. Also we know about ancient chains of arthropods: the Cambrian rocks of the age of 525 million years old contain the remains of early crustaceans Synophalos xynos, called chain shrimp. Sinforosa was sostituibili their shells in a long line of dozens of tightly linked individuals. There is even the classification of these marching columns. There are columns from the same species, several different types, unidirectional or multidirectional. And all this is the result of various factors, how abiotic and behavioral. Large concentrations trilobite shells can be formed as a result of mass post-mortem concentration, then it just randomly located residues. In the best case they are deployed in the direction of water flow, that is, the relative positions of the shells is determined by abiotic effects. But if the relative position of the shells one way or another orderly, then you need to look for other causes, behavioural, paying attention to details. Polish new finding gives the opportunity to discuss these details. Two questions obviously require decisions: where these trilobites were and how they kept together.
Polish authors answer these questions: We present evidence of one of the most ancient episodes of animal migration in the form of chains eyeless trilobites Trimerocephalus chopini from the late Devonian of Central Poland – the researchers report in their article. – These chains represent the mass migration of the group, coordinated through chemotaxis and is comparable to that observed today crustaceans like lobster. In other words, their behavior is coordinated by chemical senses, and they were sent to the spawning arenas.
In our time of migration as vertebrates and invertebrates are quite common and well studied. Typically, the mass pull to change places connected with them either with reproduction or feeding. The aforementioned lobster, for example, travel for tens of kilometers to spawning grounds, and for the day of their marching column can overcome more than 10 km from the Hypothesis that chemotaxis is consistent with what we know about the migrations of crawfish – not to disperse across the ocean floor helps them smell the urine of other animals, the location and concentration of which animals to determine accurately their antennae.
Why scientists have decided that the Polish Trimerocephalus too, like lobsters kept together at the expense of the role of chemoreception? Just because they didn’t have eyes, it was blind trilobites, so that the vision they rely could not. They are likely guided by the smell.
It is hard to imagine an animal, devoid of feelings chemosensing, in particular water animal. At all, and single-celled animals especially chemical signalling plays a role permetteranno, – reminds Elena Naimark. – But the fossil material difficult to prove that certain morphological structures were performed precisely this function. All trilobites had long jointed antenna, is provided with a series of bristles. The antenna, apparently, involved in the perception of chemical signals. In addition, some of the trilobites found the special club-shaped structure located around the mouth – the so-called frontal organ. He allegedly specialized in the role of chemoreception.
Most likely, the Polish blind trilobites were moving to the spawning grounds, suggesting Blazejowski and his colleagues. This conclusion follows from the differences in appearance of trilobites in the chains. They are clearly divided into two groups according to their characteristics, and the numerical relation of these groups, 1:1, and males and females in the vast majority of animal species. So most likely, it was the males and females gathered together for breeding, and we have a great opportunity to observe part of their mating ritual, – says Elena Naimark.
However, the way this column was caught in the storm, and raised from the bottom of sink water with high concentrations of hydrogen sulfide and carbon dioxide literally poisoned animals.
It is clear that the animals were caught by surprise, and besides being buried under a layer of sediment, they are not shifted from their positions when movement of sediment or currents of water on the surface of the sediment, they were not disturbed by burrowing benthic inhabitants. Most likely, this situation means catastrophic burial under a thick layer bad is aerated, and the depth of which is greater than the sphere of life of the inhabitants of the soil, – summarized Elena Naimark. – I don’t think it’s asphyxia, which I trust the authors. Their arguments are based on the presence of folded (who pose security) single trilobites with these chains. According to Polish experts, this suggests that the trilobites in principle, it was time to curl up, but they did not, did not, because they plunged to their death from suffocation. Otherwise, they would all be curtailed. I believe that there is something to think about, because many other chains trilobites from Morocco and Portugal unfolded consist of individuals, while located next single trilobites, as a rule, discontinued. So you need to look for an alternative explanation, and I really missed it when I read the work of Polish colleagues. Probably it lies in the data on the isotopic composition of precipitation from a given location. Such data, although presented, but not interpreted, can help to unravel the cause of the sudden death of trilobites.