Trilobites with unusual heads discovered by paleontologists

Trilobites with unusual heads discovered by paleontologists
Trilobites with unusual heads discovered by paleontologists
Anonim

Trilobites are extinct marine arthropods that lived in the ancient ocean during the Cambrian and Ordovician periods. In the modern world, horseshoe crabs and woodlice may outwardly remind us of trilobites.

Although the genetic diversity of trilobites reached its peak precisely in the Cambrian (541 - 485 million years ago), morphological differences in the cephalons - the head regions - are most noticeable in trilobites millions of years later, in the Middle and Late Ordovician.

For trilobites of the Cambrian period, the specialization of the head shield is a rather rare phenomenon, especially among the ptichoparids (a separate order of trilobites). With a few exceptions, ptichoparioids show paleontologists rather uniform cephalons - with cheek sutures that resemble blades.

Recently, however, a team of scientists consisting of Professor Zhao Fangcheng, PhD student Sun Zhixin, and Dr. Zeng Han of the Nanjing Institute of Geology and Paleontology, Chinese Academy of Sciences (NIGPAS) described a trilobite from the order of ptichoparids with an unusual head morphology. He was given the scientific name Phantaspis auritus gen. et sp. nov.

An animal fossil has been found in the Middle Cambrian Mantou Formation in Shandong Province, North China.

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Almost complete exoskeleton (left) and cranidium - the central part of the head shield (right) of the trilobite Phantaspisauritus gen. et sp. nov

This unique trilobite provides a fresh perspective on the morphological range and structural basis of cephalon specialization in Cambrian trilobites. A study of the new specimen was published in the journal Acta Palaeontologica Polonica.

Phantaspis is characterized by a brain with an enlarged anterior part of a bilobate shape, reminiscent of a pair of rabbit ears in later stages of ontogeny. This form of specialization of the head shield was not observed in any other trilobites of later periods.

This illustrates the diversity of Cambrian trilobites in morphotypes and gives an example of the variation in the outlines of the head shield in ptychopariids in the Middle Cambrian, and at the same time suggests that the specialization of cephalons in trilobites began earlier than one might have expected.

The extended cephalon Phantaspis resembles some other trilobite species with a distinct head region, such as Harpina and Trinucleidae. However, in Phantaspis, the anterior border of the cephalon was not thickened as in the above groups.

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Reconstruction of the dorsal exoskeleton and life cycle of Phantaspisauritus gen. et sp.

Scientists speculate that the shape of the head seen in Phantaspis may have reduced the danger of being eaten by other animals by increasing the size of trilobites, making them difficult for predators to eat.

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