The Abyssochrysoidea are a large group of Caenogastropods found in deep-sea environments. The genus Provanna is the largest within this group, currently containing 29 extant species from hydrothermal vents, hydrocarbon seeps, and organic falls (such as sunken wood and Whale falls) in the Pacific Ocean, the Caribbean, the Southern Ocean, and off the west coast of Africa, as well as nine species from preserved seep deposits and organic falls in Japan, New Zealand, the United States, and Peru, the oldest of which date back to the Cretaceous. These Snails are grazers and detritivores form part of biological communities which are dependent on the chemosynthetic activities of Bacteria and Archaeans for their survival.
In a paper published in the journal Zoosystematics and Evolution on 2 January 2024, Cong Wu and Fang Chen of the National Engineering Research Center of Gas Hydrate Exploration and Development, the Key Laboratory of Marine Mineral Resources of the Ministry of Land and Resources, and the Guangzhou Marine Geological Survey, Ying Tian of the Key Laboratory of Mariculture and Stock Enhancement in North China Sea at Dalian Ocean University, and the Dalian Shell Museum, Kazutaka Amano of the Department of Geology and Paleontology at the Japanese National Museum of Nature and Science, and Xin Su of the School of Ocean Sciences from the China University of Geosciences, describe a new species of Provanna from specimens recovered from two drill cores sunk into cold seeps in the South China Sea.
The new species is described from two specimens, and three other shell fragments, recovered from two separate drill cores (GMGS2-09B and GMGS2-07B) sunk into the seafloor of the northern South China Sea. The shells were obtained from carbonate layers with carbon isotope signatures which strongly indicate that they were laid down at ancient methane seeps. The new species is named Provanna dongshaensis, where 'dongshaensis' means 'from Dongsha' in reference to the island known as 'Dongsha' in Chinese, which lends its name to the area where the fossils were found. This island is currently administered by Taiwan under the name 'Tungsha', and is known as 'Pratas Island' in English.
The larger of the two specimens of Provanna dongshaensis is 10.89 mm high and has a final whorl width of 7.13 mm; the smaller has a height of 7.80 mm and a final whorl width of 5.02 mm. It is not possible to tell the length of the original shells as both are slightly damaged and lack their tips. This means that the protoconch (the shell that a marine Gastropod uses during its larval, planktonic stage), an important diagnostic tool for Gastropods is missing. Nor is the radula (tongue), another key diagnostic feature, present in any specimens, nor any genetic organic material from which DNA could be extracted. Previous studies, however, have established that the shell microstructure of the genus Provanna, is distinctive, so Wu et al. are confident in their assignment of the shells.
The largest of the specimens in the collection has been dated to 91 693 yeats before the present, though all others are significantly younger, with dates of 16 230±50 years before the present and 15120±50 years before the present. This places all specimens within the final Pleistocene glaciation, although their chronological distribution is probably more closely linked to the life cycle of the cold methane seep where they lived than to the climate on the surface. Wu et al. note that a number of other Gastropod shells are present in the cores from which Provanna dongshaensis was derived, suggesting that the site might be significant for our understanding of ancient cold seeps in the South China Sea.
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