The animal population of the Earth in the form we know today began to develop in the Cambrian period. It was then that the main groups of organisms appeared, including the first predators. The new article is devoted to Timorebestia koprii, a newly described species of carnivore discovered in Greenland. Unlike other carnivores of the Cambrian period, Timorebestia does not belong to arthropods, it is a large and one of the earliest representatives of the bristle-jawed type.
Life has existed on Earth for almost as long as our planet itself: just under four billion years. However, not all eras and periods of the biosphere’s history have been described in equal detail. Its early stages – including the long Proterozoic era, when the Earth remained a “planet of microbes” with some multicellular inhabitants – are represented only by few and poorly preserved fossils.
Everything changed with the onset of the Paleozoic era and its first period, the Cambrian, 539 million years ago. Then the biodiversity of the oceans increased dramatically, many animals acquired skeletons (which are well preserved in fossilized form) and the first predators appeared. Before that, eating other animals had never occurred to anyone. However, there were no good goals either.
The Cambrian predators had a very peculiar appearance – like, for example, the anomalocaris (literally, “abnormal shrimp”) with two curved tentacles near a large round mouth. Or the opabinea, which had five eyes and a long grasping trunk. Paleontologists refer to them as early arthropods of a kind and note that some sizes were close to a meter.
However, the first arthropods appeared 529-521 million years ago, that is, 10-20 million years after the beginning of the Cambrian. A new article for Science Advances is devoted to an even older group of animals – the bristlejawed or sea arrows (Chaetognatha), which appeared at least 538 million years ago, at the dawn of the Cambrian. The authors described a new species and genus of bristlecone – Timorebestia koprii, the remains of which were discovered in the north of Greenland, in the camp of the Sirius Pass field.
The huge island in those distant times was completely different: free of ice and much warmer. Moreover, it was located in the Southern Hemisphere.
Timorebestia reminded the scientists of Amiskwia sagittiformis, another Cambrian organism that is similar in structure, and most likely also related to modern bristlejaws like saggites. These sea arrows are small planktonic invertebrates ranging in size from a few millimeters to 12 centimeters. Bristlejaws swim, bending their bodies up and down, and eat smaller planktonic organisms: infusoria, microscopic crustaceans, and so on. To do this, bristlecone mammals use special bristles near the mouth – hence their name.
Two distant relatives of these creatures from the Cambrian – Timorebestia and Amiskwia – share a common body plan and a nektonic lifestyle, i.e. active swimming in the water column. Other similarities include the presence of lateral and caudal fins, a well-developed head section with long antennae (“antennae”), and the structure of the mouthparts.
For a Cambrian animal, T. koprii was impressive in size – some specimens reached a length of almost 30 centimeters. The fossil also contained a ganglion, or nerve node, located on the ventral side. Ganglion is well preserved due to the unique mechanism of secondary phosphate mineralization (phosphatization). Such an organ is characteristic of bristlecone mammals, which allows us to confidently attribute thymorebestia to this type of animal. At the same time, it cannot be said that he was the ancestor of the living naval gunners. Scientists have assigned T. koprii to a dead-end, so-called stem group type.
The authors of the study believe that the animal described by them led a predatory lifestyle, which explains the large antennas and complex structure of the fins. Moreover, in the digestive tract of one of the fossilized specimens of T. koprii, several arthropods with a shell of the species Isoxys volucris were found.
It turns out that Timorebestia was one of the largest predators of the Cambrian period and “climbed” to the top of the food chain before arthropods like Anomalocaris. This distinguishes Timorebestia koprii from its modern relatives, the sea arrows, which are forced to be content with modest prey and often find themselves eaten, for example, by fish.
