Abstract Morphological characteristics of the teeth and mandibles of Lemmus cf. sibiricus from the Skorodumian faunal complex of the Eopleistocene of Western Siberia were compared with similar characteristics of modern and fossil Lemmini from Europe and Asia (using collection and literary data) in order to estimate the possibility of clarifying the taxonomic affiliation and determining the place of the considered form in the evolutionary history of Palearctic Lemmini. The comparative morphological approaches based on qualitative traits and linear measurements of cheek teeth (traditionally used for the taxonomic diagnostics of representatives of the tribe) were used. It was demonstrated that according to a combination of apomorphic and plesiomorphic traits, lemmings from the Skorodumian faunal complex of the Eopleistocene of Western Siberia occupy an intermediate position between the more ancient L. kowalskii and modern species Lemmus sibiricus. Based on such intermediate position between the ancestral widespread form and modern regional taxa of the genus Lemmus, Western Siberian Eopleistocene lemmings correspond to Eastern Siberian L. sheri Abramson, 1992. Differences between the Eopleistocene forms and L. kowalskii are clearly traced and reflect the evolutionary changes in the cheek teeth associated with the transition of the Eopleistocene forms to a higher level of specialization toward bryophagy. At the same time, a morphological similarity of Western and Eastern Siberian Eopleistocene lemmings to each other is no higher than the similarity of each of regional forms to modern Lemmus inhabiting the same region. Therefore, it can be assumed that within the Eurasian range of the Eopleistocene Lemmus, a geographical differentiation, comparable by the level of interregional differences with differentiation within the distribution area of modern genus Lemmus, could be observed. A combination of similarities in some traits and differences in other ones most likely reflects mosaic morphological changes on the scale of the vast Eopleistocene range of the same form (probably, a polytypic taxon, which should be designated as Lemmus sheri Abramson, 1992 by right of priority). Taking into account the presence of regional peculiarities, it is appropriate to designate the Eopleistocene lemmings of the Olerian Formation of Eastern Siberia as L. sheri sensu stricto, and to classify lemmings from the Skorodumian faunal complex of Western Siberia as a polytypic taxon L. sheri sensu lato.

True Lemmings (Lemmini, Arvicolinae, Rodentia) in the Eopleistocene (Calabrian) of the North of Western Siberia

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2025年12月1日

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E. A. Markova,
A. V. Borodin

摘要

Abstract

Morphological characteristics of the teeth and mandibles of Lemmus cf. sibiricus from the Skorodumian faunal complex of the Eopleistocene of Western Siberia were compared with similar characteristics of modern and fossil Lemmini from Europe and Asia (using collection and literary data) in order to estimate the possibility of clarifying the taxonomic affiliation and determining the place of the considered form in the evolutionary history of Palearctic Lemmini. The comparative morphological approaches based on qualitative traits and linear measurements of cheek teeth (traditionally used for the taxonomic diagnostics of representatives of the tribe) were used. It was demonstrated that according to a combination of apomorphic and plesiomorphic traits, lemmings from the Skorodumian faunal complex of the Eopleistocene of Western Siberia occupy an intermediate position between the more ancient L. kowalskii and modern species Lemmus sibiricus. Based on such intermediate position between the ancestral widespread form and modern regional taxa of the genus Lemmus, Western Siberian Eopleistocene lemmings correspond to Eastern Siberian L. sheri Abramson, 1992. Differences between the Eopleistocene forms and L. kowalskii are clearly traced and reflect the evolutionary changes in the cheek teeth associated with the transition of the Eopleistocene forms to a higher level of specialization toward bryophagy. At the same time, a morphological similarity of Western and Eastern Siberian Eopleistocene lemmings to each other is no higher than the similarity of each of regional forms to modern Lemmus inhabiting the same region. Therefore, it can be assumed that within the Eurasian range of the Eopleistocene Lemmus, a geographical differentiation, comparable by the level of interregional differences with differentiation within the distribution area of modern genus Lemmus, could be observed. A combination of similarities in some traits and differences in other ones most likely reflects mosaic morphological changes on the scale of the vast Eopleistocene range of the same form (probably, a polytypic taxon, which should be designated as Lemmus sheri Abramson, 1992 by right of priority). Taking into account the presence of regional peculiarities, it is appropriate to designate the Eopleistocene lemmings of the Olerian Formation of Eastern Siberia as L. sheri sensu stricto, and to classify lemmings from the Skorodumian faunal complex of Western Siberia as a polytypic taxon L. sheri sensu lato.