240 million years ago, a group of four-legged marine animals passed through a shallow sea area, leaving a string of footprints of different shades on the wet soil of the seabed... Water waves drive sediment, and footprints gradually seal the seabed. Vicissitudes of mulberry fields. What was once a shallow sea is now mountainous. Recently, scientists have uncovered the secrets of this string of footprints.
Chinese Beantooth Dragon Swimming Restoration Drawing Zhang Zongda
How are footprints found?
Recently, a team of Chinese and foreign scientists announced the discovery of more than 200 marine reptile footprints in The Town of Qipu, Economic Development Zone, Anshun City, Guizhou Province, some of which provide evidence of the earliest simultaneous swimming of marine tetrapods to date. The research paper was published in the journal paleontological journals Paleogeography, Paleoclimate, Paleoecology.
In the summer of 2017, at the invitation of the Guizhou Provincial Museum, the deliminology experts of China University of Geosciences (Beijing) and their German counterparts conducted several inspections of the footprints of The Shop, and carried out three-dimensional photography, distribution mapping and meticulous measurements. Geological surveys show that this combination of footprint fossils is preserved on the thin to medium-thick layer of argillaceous dolomite in the Pine Nut Kan section of the Triassic Anni-level Guanling Formation in Honglong Village, Wanpu Town. This section of the strata has produced the famous Luoping biota – including abundant fish fossils and marine reptile bones, arthropods and spinosaurs, bivalves, gastropods, brachiopods and ammonites, as well as plant fossils. Footprint point areas belong to lagoon or shallow sea sediments.
Xing Lida, associate professor at China University of Geosciences (Beijing), is one of the researchers who made this discovery. He introduced that relicologists have found a large number of terrestrial main dragon footprints in the Songzi kan section of the Guanling Formation in Yunnan Province, such as the footprints of Bo's hand beasts. However, the 22 tracks and more than 200 isolated footprints found at the footprint point of The Shop, as well as some uncertain traces, are obviously different from terrestrial footprints, but belong to the footprints left by rare marine reptiles under the water.
"It's very rare that footprints underwater can be kept." Xing Lida said that on the rocks of the footprint site, the researchers found a new type of footprint. This set of footprints, the overall look is a bit of an eight-figure, some are half-foot on the ground, some are full-foot on the ground. It should have been left by a quadruped animal that "walked and swam" in the sea. If you look at the details, you can also see that these footprints have complete toe marks and palm marks, and each footprint has four toes, thick and blunt. There is also an elongated "heel" behind the footprints. "This morphological characteristic and the pattern of the 'outer eight characters' are similar to the footprints that paleontologists have known before."
The fossils are very different. Xing Lida introduced that these footprints have complete toe and palm marks, similar to the footprints left by quadrupeds walking normally on land." The overall footprint is wide, the footprint is symmetrical and turns outward relative to the midline of the trail, which is a typical tetrapod footprint with underwater swimming or seabed walking habits. Because its morphology and track pattern are significantly different from previous footprint records, the researchers have classified it into a new taxonomy and named it Anshunpesaquacursor, where the genus name "Anshun Footprint" is taken from Anshun, Guizhou, where the footprint was found, and the "Running" in the species name means "runner in the water".
Anshun footprint photo and walking map
What animals are left behind?
"The most direct way to decipher the footprints left by this animal is to compare the fossil bones of the footmen." Xing Lida said.
Of course, it is not a random search for fossils, and researchers must first find fossil bones produced by the relevant strata. "We studied fossils from nearby and adjacent strata, including the skeletons of Triassic marine reptiles in Guizhou and Yunnan provinces, such as turtles, ichthyosaurs, sea dragons, protosaurus, and main dragons." Of these "potential tracers", the primitive turtles were excluded because they had typical bow-shaped pre-footprints and scratch-like features of toe marks that did not appear in the sample; ichthyosaurs could not leave any clear toe marks and could be completely excluded; sea dragons had a distinctly different pattern of movement from the Anshun footprints, with toe proportions and sharp claws different from Anshun footprints; proto-dragon toe proportions different from Anshun footprints; and the dominant dragon-shaped claws did not match the fossil samples.
Xing Lida said, don't look at the "fish dragon" and "sea dragon" in the name of the "dragon", in fact, it is not a dinosaur, just a distant relative of the dinosaurs living in the water. "After the same exclusion, there are not many possibilities left. At this time, our eyes were on the newly shoped Chinese bean tooth dragon. Beantooth dragon is a kind of marine reptile that lived in the Triassic Period, looking a bit like a large turtle, with a large triangular head and bean-like teeth in its mouth, which is also the origin of its name. ”
"The flipper bones of the Chinese bean-toothed dragon are laterally expanded, and the thick toe ends are not so sharp, which is very compatible with our newly discovered set of footprints." Xing Lida introduced that the Chinese bean tooth dragon was found in Xinpu Township, Anshun City, Guizhou Province, and this discovery site is only a few tens of kilometers away from the discovery place of this set of footprints - the town of Qipu in Anshun City, Guizhou Province. "Of course, we can't be sure that this is the footprint left by the Chinese bean tooth dragon, because the Chinese bean tooth dragon lived a little later than the age of this set of footprint fossils found this time." Xing speculated that this may have been left by relatives of a slightly earlier beantooth dragon, or that there may have been other reptiles reptiles reptiles that resembled beantooth dragons.
Therefore, the "tracers" of the Anshun footprint may be dragon turtles or a dragon-toothed dragon-like dragon that has not yet found bones in the Guanling Formation.
How do you swim in the sea?
"Being able to know how two marine reptiles are operating in the same shallow sea environment is one of the big implications of this study." At the same time, through the study of the footprints of the rush, we also further revealed how marine reptiles use their limbs to swim together. Xing Lida introduced that the fossil samples in the study revealed the synchronous movement, rowing or propped movement of limbs of marine animals - that is, symmetrical left and right limbs moving at the same time." "Bracing" describes the use of the forelimbs or hind limbs to reach the bottom to push the body down the water.
Due to the harsh storage conditions, the underwater traces of marine tetrapods are rarely preserved. Therefore, the footprint fauna from Anshun, Guizhou is of great significance, they record the underwater activity of marine reptiles, and they are the first to find records of the underwater behavior of plesiosaurs or dragon turtles, revealing the early swimming methods of marine reptiles using limb coordination. At the same time, the fossil footprint combination shows that the plesiosaurs once appeared with plesiosaurs or dragon turtles to feed in shallow sea environments such as lagoons along the coast of the East Tethys Sea, which further understood the habits and movements of marine reptiles in shallow waters of the Middle Triassic or the bottom of lagoons, and expanded the limited understanding of marine reptile footprints. The rich fossil record facilitates the comparison of biota in this study area with other regions, and provides direction for paleontology, paleontological geography and paleoenvironmental studies.
(Original title: Chinese and foreign scientists found marine reptile footprints 240 million years ago, this "runner" is still an outer eight characters)
Source: Beijing Evening News
Process Edit: U016
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