More than 500 million years ago, in the clear geological sea of Gondwana, a strange-shaped arthropod slowly crawled on the bottom of the sea, searching for biological remains and other organic matter. They are Marrella. Marra worms appeared in large numbers in the Cambrian ocean and belonged to a unique class of arthropods-Marrellomorpha (Marrellomorpha). At present, the earliest Malraea appeared in the early Cambrian strata in Hunan, China, and it has been more than 500 million years ago. The family is very prosperous and is the most numerous arthropod in the Burgess Shale Biota in Canada. Marla worms and their close relatives are also a thriving group. For the next 150 million years, they have lived freely in the ocean and evolved various types. They are like modern sea spiders, evolving skinny shells to dispel the appetite of predators and continue their lives.
The earliest record of Marra insect fossils
In 1909, the famous paleontologist Charles Walcott collected the first Marla worm fossil from the Burgess Shale in Canada. At first, Walcott thought it was like a lace crab, perhaps a strange trilobite. In 1971, paleontologist Harry Whittington re-studied this fossil and based on the characteristics of its legs, gills, and head appendages, he determined that it was not our common trilobites, chelated limbs or crustaceans, but a A brand-new taxa, so a new class of Marla.
In 2012, paleontologist Liu Qing discovered and reported the earliest Malraea so far in Paiwu Township, Huayuan County, Xiangxi, Hunan, China. Although only one fossil specimen was found at that time, the traces of the back spines of the Marra worm were clearly preserved, indicating that the early representative form of the Marra worm was simple, with the X-shaped back spines as the main feature and smooth edges.
Weak creatures in the Cambrian ocean
Marla worms are very weak animals in the Cambrian ocean, so they need to find ways to protect themselves from being killed. They did not use the traditional method, but took a different approach to reduce their size, become skinny and make predators lose their appetite. The most typical feature of Marla worms is that two pairs of long curved spines extend to the rear, and the streamlined and light body makes it easy to cruise freely in the ocean.
Before the discovery of the Marla worm in the Loquat nut biota in western Hunan, the earliest Marla worm fossils appeared in the Kaili biota in Guizhou. The Kaili Biota includes 11 major categories and more than 100 genera of animal fossils, featuring various arthropods, echinoderms, and jellyfish, including trilobites, and many specimens have preserved mollusc structures. The age is slightly earlier In the Burgess Shale Biota, Canada. The Marla worms discovered and reported in the Kaili Biota are very similar in morphology to those of the Loquat Nut Biota, and there may be a close relationship between them.
The Canadian Burgess Shale Biota is located in British Columbia. More than 100 marine animals have been discovered, of which arthropods are the dominant group. The Marla worm fossil is one of the most common fossils in the Burgess shale biota. More than 25,000 specimens have been collected, making it the second most common arthropod in the area. Among them, the most prominent feature is the discovery of a large number of Marla worms that preserve soft structures. Soft structures such as appendages are all well preserved, providing important materials for comprehensive scientific research.
In addition, a new species of Marra worm-Marra worm Australia, a three-dimensional preserved Austen-type fossil, was also discovered in the Monk Creek Phosphate Biota in Australia, providing paleontologists with more information about this species.
Relatives of Marla in the Paleozoic ocean
After the Cambrian, Marra worms evolved more new types. The back spines of the Fuca worm that appeared in the Ordovician are more gorgeous, with a pair of small spikes protruding from both sides, forming a hexagon. There are many slender cilia growing on the edges of the six spikes, which are extremely gorgeous. Most of the fossils of Foca worms only retain the hard bone spurs, but in the Feizurata Special Buried Fossil Library in Morocco, the body structure of the Foca worms is also completely preserved, which is not easy. These light little guys are swimming in the Ordovician ocean, like elves living in the sea.
About 50 million years later, scientists discovered the descendant of Marra insects, Mimetaster hexagonalis (Mimetaster hexagonalis) in the Hunsrück Special Burial Fossil Library of the Early Devonian in Germany. Although its carapace is small, its two strong appendages are exceptionally prominent, just like a steel spider.
After the Devonian Marla descendants disappeared, no traces of such arthropods were found in the strata. It seems that their extinction also represents the collective curtain call of the Cambrian evolutionary fauna. Soon after, the curtain of new life forms Pulled up slowly.