Analysis of the jaw sizes of modern sharks did not make it possible to estimate the body size of prehistoric plaquetoderms. In this respect informs PeerJ.
Placoderms are an extinct class of marine vertebrates, their old name being “armored fish”. These predators lived in the Earth’s oceans about 435-360 million years ago, the largest species reached a length of 9-10 meters. Their heads and parts of their bodies were covered with a shell, but the skeleton itself was composed of cartilage, like that of sharks, and therefore placoderms were very poorly tracked in the fossil record. In particular, the size of some species is only approximately known, so the idea of body length of dunkleosts from the Artrodirus lineage was derived based on the size of their jaws and the search for an analogy. modern sharks.
Russell Engelman at Case Western Reserve University and colleagues set out to test these methods, using data from modern sharks, as well as placoderms whose body sizes were accurately measured by analyzing fossils.
“For many years, Dunkleosteus Length estimates of 5-10 m have been given, but apparently no one has statistically tested these methods and checked whether they give reliable or reasonable results on other known fish of the class arthrodyra, ”says the scientist.
It turns out that the size of the sharks’ mouth does not allow us to accurately estimate the body size of an arthropod. More “stocky” arthropods have always had larger mouths than sharks of similar length. Therefore, when assessing the body lengths of the arthrodia from their mouths, they appeared to be 2-2.5 times their actual size as determined from the entire skeleton. In Dunkleosteus, the mouth is particularly large even for an arthropod, which does not allow it to be used to estimate total body size.
These findings help explain the oddity described earlier – according to past estimates, dunkleosteus should have been an extremely elongated fish with a small eel-like head, although the plactoderms should have resembled sharks. These proportions would make the animal’s gills so small relative to its body that the fish would likely suffocate.
ancient biologists raised artificial fat for test tube meat.