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16 August 2021 The first records of mollusks from mid-Cretaceous Hkamti amber (Myanmar), with the description of a land snail, Euthema myanmarica n. sp. (Caenogastropoda, Cyclophoroidea, Diplommatinidae)
Igor Balashov
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Abstract

Five land snails and the borings of marine bivalves are reported from Hkamti (Khamti) amber whose age was recently uranium-lead dated to be ca. 110 Ma, in contrast to the nearby Kachin (‘Burmese') amber considered to be ca. 99 Ma. Four of the snails belong to Cyclophoridae, and although their condition does not allow unambiguous identification or description of the species, one of them strongly resembles Archaeocyclotus plicatula Asato and Hirano in from Kachin amber. The fifth snail, Euthema myanmarica n. sp. (Diplommatinidae), is a representative of a genus that was known exclusively from Kachin amber until now. The genus Euthema is revised, with a new synonym, Xenostoma . The recently described ‘Truncatellina dilatatus’ from Kachin amber is placed in Euthema. A comparison of the distinguishing characters of the eight Euthema species is provided. The borings of bivalves in Hkamti amber correspond to the ichnospecies Teredolites clavatus , associated with the bivalve genus Martesia (Pholadidae), and are common in Kachin amber. Similarity of the malacofauna from Hkamti and Kachin ambers, as well as the presence of numerous, similar Teredolites clavatus, indicates that these ambers were formed in very similar paleoenvironments. This indication suggests that forests with very similar conditions existed throughout the entire Albian to the early Cenomanian, or that the dating of at least one of these amber deposits is incorrect. In the latter case, it would mean that Kachin amber is at least 110 Ma or older.

Copyright © The Author(s), 2021. Published by Cambridge University Press on behalf of The Paleontological Society
Igor Balashov "The first records of mollusks from mid-Cretaceous Hkamti amber (Myanmar), with the description of a land snail, Euthema myanmarica n. sp. (Caenogastropoda, Cyclophoroidea, Diplommatinidae)," Journal of Paleontology 95(5), 994-1003, (16 August 2021). https://doi.org/10.1017/jpa.2021.26
Accepted: 21 February 2021; Published: 16 August 2021
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