Original title: what does a hairy snail look like? A snail with horny hair appeared 100 million years ago (Amber)
On October 12, a team of Chinese and foreign scientists announced that they had found terrestrial snails with horny hair in amber for the first time, which is also the oldest record with hairy bodies in the current gastropod fossil record.
'the snail carried a heavy shell and climbed up step by step. ' In the Middle Cretaceous about 100 million years ago, there was a snail whose shell was' hairy '. It was wrapped in amber during foraging or traveling and remains today.
On October 12, a team of Chinese and foreign scientists announced that they had found a terrestrial snail with horny hair in amber for the first time, which is also the oldest record with hairy structure in the current gastropod fossil record.
The study was conducted by Thomas & middot of the University of gisenyustus libich in Germany; Dr. Thomas A. Neubauer, associate professor Xing Lida of China University of Geosciences (Beijing), and researcher Adrian & middot of the natural history museum in Bern, Switzerland; Adrienne Jochum studied together. The research paper was published in iscience, an international well-known academic journal and a subsidiary of cell group.
Restoration diagram of amber wool ring snail. (drawing Liu Yi)
A furry shell is an ancestral sign
The amber specimen comes from the famous amber producing area - hukang River Valley, Kachin state, northern Myanmar. The amber here is about 100 million years ago, which is the Middle Cretaceous.
The newly discovered snail amber fossil is about 6.6 mm in diameter and 2.2 mm high. Through the reconstruction, segmentation and fusion of CT data, Xing Lida's team obtained the high-definition 3D shape of the specimen.
Different from most known gastropods, the shell surface of this specimen is covered with dense horny hair, and there are obvious threads on the upper and top sides of the lateral edge of the spiral layer. Therefore, the author named a new genus: hirsuticyclus, and a new species is h. electrum.
Amber wool ring mouth snail.
'in terms of classification, the amber hairy ring mouth snail belongs to the ring mouth Snail family (cyclophoridae),' Thomas pointed out, 'the family is some ancient terrestrial species, generally like to live in a warm, humid, dark and humus environment.'
Like snails, most gastropod species have a spiral shell that retracts its soft body into the shell when in danger. Some gastropods have a layer of horny hair on their shells. Scholars believe that these hairy structures may be a defense measure to reduce predatory, or increase the adhesion of water to make it easier to move, or improve the adhesion of the shell surface.
This feature has been repeated in hygromiidae, Helicidae and other categories, which indicates that this feature has evolved independently for several times. Scholars speculate that hair structure is an ancestral sign, which has been lost many times in the evolution history, which may be related to the round-trip transformation of the environment from humidity to drought.
Close up of amber hair ring mouth snail.
The fur on the shell can deter predators
Although hair structures have evolved independently for several times, according to Xing Lida, they have never been found in the fossil record before. " We can't imagine that these extremely exquisite structures can be preserved in the form of traditional fossils, but the emergence of amber perfectly solves this problem and finally gives us the opportunity to study the hairy snail in the fossil record. "
He said that the amber hairy ring mouth snail is a magical gift brought by the special preservation of amber. It is the only record with hairy structure in the current gastropod fossil record, and it is also the oldest record.
What is the role of the horny hair covering the surface of the shell? Scientists believe that this horny hair is a snail's adaptation to the tropical forest environment, increases its adhesion to plants during foraging in a humid environment, and may also have the function of collecting and transporting small seeds. The emergence of this trait has a great relationship with the global radiation evolution of angiosperms, the main food of snails. Snails may prefer soft angiosperms to hard conifers.
Scientists infer that the amber hairy ring mouth snail has gradually adapted to the angiosperm dominated world in the mid Cretaceous. The hair on the shell first deterred predators. Functionally, it helps it better adhere to the leaves of angiosperms, reduce the risk of accidental falling, and the large consumption of falling and climbing back to the top.
Moreover, a thick layer of hair can also play a role in heat insulation.
Another interesting finding is that living bees unintentionally transfer pollen from one flower to another through their whole body villi. The seta of amber hair ring mouth snail may also have a similar function.
In the Middle Cretaceous, the average size of angiosperm seeds was very small, often less than 1 cubic mm. The hair of amber hair ring mouth snail may attach to some small seeds and spread with movement to other places.
In other words, the diffusion of angiosperms may trigger the adaptive evolution of snails and promote the diversification of Cretaceous terrestrial snails. In turn, the evolution of snails also helps the diffusion of angiosperms to some extent.
Hairy ring ribbed snail. (photographer Zhou Qinghua)
Know more: amber is a great sample for studying paleontology
In 2016, Xing Lida's team published the world's first ancient bird and dinosaur in amber, and then found frogs, snakes and snails with soft tissues such as tentacles in amber.
"The small animal fossils wrapped in amber in Myanmar are the best Cretaceous paleontological samples we have encountered so far. They provide an important supplement to the compression fossils in sedimentary rocks, reveal the three-dimensional details of soft tissue that traditional fossils are difficult to preserve, and deepen our understanding of ancient animals." Xing Lida introduced.
The discovery of Cretaceous amber in the hukang River Valley of Kachin state in northern Myanmar, a famous amber producing area, has also provided a unique forest ecosystem record for scientists' research since 2000.
Just yesterday, paleontologists also announced the research results of frog egg amber. The specimen is an extremely rare amphibian egg. 55 eggs, which are spherical to ovoid, are preserved, with an average diameter of about 1.2 millimeters. Each egg cell consists of a gelatinous mass and a dark centrosome, which may represent primitive egg cells.