动物实验 z-bo 2020-11-05 334

　　The Carboniferous is the era of the famous giant creatures. In addition to the well-known terrestrial creatures such as giant dragonflies and giant spiders, some huge invertebrates such as ammonites and brachiopods also lived in the ocean. Many studies have shown that the enlargement of terrestrial organisms is mainly related to the higher oxygen content in the atmosphere (up to about 35% in the Carboniferous). However, there is still no clear conclusion about the factors affecting the enlargement of invertebrates in the ocean.

　　Gigantoproductus is one of the largest brachiopods. It is a kind of standardized stone in the Early Carboniferous strata. It usually gathers in layers in the wild, with a shell width of more than 10 cm. However, most of the brachiopods were no more than 2-3 cm in size during the geological history. In order to understand the distribution and evolution of these large brachiopods, Dr. Qiao Li from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, and others have collected a certain number of related specimens in multiple field work in South China, and combined them with the recorded fossils of Longshen shell. The study of origin and geographical distribution analyzes their distribution and evolution law.

　　The study found that the spatial and temporal distribution of the long-shen shell has obvious limitations. In terms of time, they mainly appeared in the middle and late Early Carboniferous (mid-Constitution-middle and late Serpukhov). Spatially, they are mainly distributed in Eurasia. Through palaeogeographic reconstruction, it is found that Dalongshen shellfish is mainly distributed around the Paleo-Tethys at middle and low latitudes (Figure 2), so it adapts to the relatively narrow regional climate and environment of the equatorial region. Therefore, when the late Paleozoic Great Ice Age developed on a large scale in the late Early Carboniferous, Dalongshen shellfish quickly disappeared. At present, more research is needed on the factors that influence the size of the long shellfish.