Margarita Erbajeva

Evolutionary History of Lagomorphs in Response to Global Environmental Change

Although species within Lagomorpha are derived from a common ancestor, the distribution range and body size of its two extant groups, ochotonids and leporids, are quite differentiated. It is unclear what has driven their disparate evolutionary history. In this study, we compile and update all fossil records of Lagomorpha for the first time, to trace the evolutionary processes and infer their evolutionary history using mitochondrial genes, body length and distribution of extant species. We also compare the forage selection of extant species, which offers an insight into their future prospects. The earliest lagomorphs originated in Asia and later diversified in different continents. Within ochotonids, more than 20 genera occupied the period from the early Miocene to middle Miocene, whereas most of them became extinct during the transition from the Miocene to Pliocene. The peak diversity of the leporids occurred during the Miocene to Pliocene transition, while their diversity dramatically decreased in the late Quaternary. Mantel tests identified a positive correlation between body length and phylogenetic distance of lagomorphs. The body length of extant ochotonids shows a normal distribution, while the body length of extant leporids displays a non-normal pattern. We also find that the forage selection of extant pikas features a strong preference for C3 plants, while for the diet of leporids, more than 16% of plant species are identified as C4 (31% species are from Poaceae). The ability of several leporid species to consume C4 plants is likely to result in their size increase and range expansion, most notably in Lepus. Expansion of C4 plants in the late Miocene, the so-called ‘nature’s green revolution’, induced by global environmental change, is suggested to be one of the major ‘ecological opportunities’, which probably drove large-scale extinction and range contraction of ochotonids, but inversely promoted diversification and range expansion of leporids.

New data on Late Miocene - Pleistocene ochotonids (Ochotonidae, Lagomorpha) from North China

Detailed study of ochotonids from the Late Miocene-Pleistocene of North China revealed more than fifteen ochotonid taxa. They include Ochotona plicodenta sp. nov., O. gracilis sp. nov., O. lingtaica sp. nov., O. youngi sp. nov., O. magna sp. nov., O. zhangi sp.nov., O. cf. O. lagreli, O. cf. O. minor, O.c f. O. cansus, O. aff. O. tibetana, O. aff. O. bazarovi, O. aff. O. dodogolica, O. aff. O. intermedia, Ochotona sp. (small), O. complici- dens and O. complicidens near to Ochotonoma. Of these species, the former ten are the en- demics to China and the other forms are widely-distributed in Asia. Evolutionary history of ochotonids is shortly discussed.

Pliocene and Pleistocene biostratigraphic succession of Transbaikalia with emphasis on small mammals

This paper deals with the Pliocene, Pleistocene and Holocene mammalian faunas of the Transbaikal area for which 15 successive mammalian faunas are recognized. This review is based on the study of new paleontological materials obtained from several Late Cenozoic localities and reexamination of existing faunal data. Stratigraphically, the oldest fauna is known as Udunginian. It contains mostly fossils of forest inhabitants and few arvicolids. This fauna was replaced by the next Pliocene hipparion assemblage known as the Chikoi Faunistic Complex, characterized by the dominance of forest-steppe and open landscape inhabitants, as well as by the abundance and diversity of rooted arvicolids. The Itantsinian Complex is the following faunistic level of the Late Pliocene. It is characterized by the first appearance of Equus and Spermophilus and by the presence of progressive taxa of rooted voles. The Early Pleistocene fauna is characterized by the appearance and abundance of rootless arvicolids and by the continued existence of the latest rooted voles. The Middle Pleistocene Tologoi Faunistic Complex is distinguished from the preceding one by the disappearance of rooted voles. The Late Pleistocene fauna featured a diversity of Microtus taxa and an abundance of Lasiopodomys and Ochotona species. The majority of the Late Pleistocene small mammals belong to recent species, although some of them were distributed over a greater area at that time than at present.

Stepwise onset of the Icehouse world and its impact on Oligo-Miocene Central Asian mammals

Central Asia is a key area to study the impact of Cenozoic climate cooling on continental ecosystems. One of the best places to search for rather continuous paleontological records is the Valley of Lakes in Mongolia with its outstandingly fossil-rich Oligocene and Miocene terrestrial sediments. Here, we investigate the response by mammal communities during the early stage of Earth’s icehouse climate in Central Asia. Based on statistical analyses of occurrence and abundance data of 18608 specimens representing 175 mammal species and geochemical (carbon isotopes) and geophysical (magnetic susceptibility) data we link shifts in diversities with major climatic variations. Our data document for the first time that the post-Eocene aridification of Central Asia happened in several steps, was interrupted by short episodes of increased precipitation, and was not a gradual process. We show that the timing of the major turnovers in Oligocene mammal communities is tightly linked with global climate events rather than slow tectonics processes. The most severe decline of up 48% of total diversity is related to aridification during the maximum of the Late Oligocene Warming at 25 Ma. Its magnitude was distinctly larger than the community turnover linked to the mid-Oligocene Glacial Maximum.

Geology and fauna, and preliminary correlation of sediments of the main Late Cenozoic sites of the Transbaikal area

Abstract The Pliocene and Pleistocene sediments exposed in eight sections of Transbaikalia have been correlated using geological and palynological data, together with information on fossil mammals and some paleomagnetic characteristics. The most complete sequence of fossiliferous deposits (spanning the time interval from the Middle Pliocene to the Late Pleistocene) is exposed in the Tologoi key section. The sequence was correlated with other sections primarily on the basis of mammal faunas. During deposition of the Chikoi Suite, Udunginian, Chikoian and Itantsinian faunal complexes appeared in succession. Four successive stages in mammal evolution are recognized within the Early Pleistocene. Deposition of the Krivoyarskaya Suite proceeded throughout the time when the Tologoi faunistic complex, Ivolginian and other Pleistocene faunas followed each other in the Transbaikalian region.

Oligocene and early Miocene mammal biostratigraphy of the Valley of Lakes in Mongolia

The Taatsiin Gol Basin in Mongolia is a key area for understanding the evolution and dispersal of Central Asian mammal faunas during the Oligocene and early Miocene. After two decades of intense fieldwork, the area is extraordinarily well sampled and taxonomically well studied, yielding a large dataset of 19,042 specimens from 60 samples. The specimens represent 176 species-level and 99 genus-level taxa comprising 135 small mammal species and 47 large mammals. A detailed lithostratigraphy and new magnetostratigraphic and radiometric datings provide an excellent frame for these biotic data. Therefore, we test and evaluate the informal biozonation scheme that has been traditionally used for biostratigraphic correlations within the basin. Based on the analysis of the huge dataset, a formalised biostratigraphic scheme is proposed. It comprises the Cricetops dormitor Taxon Range Zone (Rupelian), subdivided into the Allosminthus khandae Taxon Range Subzone and the Huangomys frequens Abundance Subzone, the Amphechinus taatsiingolensis Abundance Zone (early Chattian), the Amphechinus major Taxon Range Zone (late Chattian), subdivided into the Yindirtemys deflexus Abundance Subzone and the Upper Amphechinus major T. R. Z., and the Tachyoryctoides kokonorensis Taxon Range Zone (Aquitanian). In statistical analyses, samples attributed to these biozones form distinct clusters, indicating that each biozone was also characterised by a distinct faunal type.

Karyological and dental identification of Microtus limnophilus in a large focus of alveolar echinococcosis (Gansu, China)

A study of voles (Arvicolidae, Rodentia) from Gansu (China) designed to identify a potential host of Echinococcus multilocularis, responsible for human alveolar echinococcosis, leads to a general analysis of Microtus limnophilus population karyotypes, M1 of M. oeconomus populations from all of Eurasia and of M. limnophilus of Mongolia. The Microtus of Gansu belonging to the nominal subspecies M. limnophilus limnophilus (2n = 38; NF = 58) differs markedly in size and shape of M1 from the M. limnophilus of Mongolia, which must therefore be considered as a new subspecies M. limnophilus of malygini nov. ssp. (2n = 38; NF = 60) and the M. oeconomus of Mongolia should be ranked as M. oeconomus kharanurensis nov. ssp. (2n = 30; NF = 60).

Occurrences of Sinolagomys (Lagomorpha) from the Valley of Lakes (Mongolia)

The genus Sinolagomys is an early representative of the family Ochotonidae, appearing first in the late early Oligocene of Central Asia. It is known in China from Shargaltein Tal, Taben Buluk, Ulan Tatal, and northern Junggaria, and a few specimens from Tatal Gol, Mongolia have been published. For most occurrences, the genus is not represented by many specimens. Extensive studies in the Valley of Lakes, Central Mongolia, have produced a large number of sinolagomyin fossils spanning at least 10 million years and belonging to five species: Sinolagomys kansuensis, Sinolagomys major, Sinolagomys gracilis, Sinolagomys ulungurensis, and Sinolagomys badamae sp. nov. Descriptions of these are given, as well as definition of the new species. Sinolagomyins flourished during the late Oligocene and early Miocene and came to occupy vast territories from China through Mongolia and Kazakhstan. The evolution of this ochotonid group is characterized by increasing taxonomic diversity and progressive development of rootless cheek teeth.

Determining the ontogenetic variation of lower cheek teeth occlusal surface patterns in lagomorphs using micro-ct technology

Micro CT-scanning has been performed on the lower jaws of some selected lagomorph taxa in order to reconstruct unequivocally their controversial ontogenetic development. The analyses were concentrated on the development of p3, and on the sequences of lobe connections and on the sequence of appearance/disappearance of flexids/fossettes of p4-m2. This is the first time that this approach has been applied to lagomorphs and opens promising perspectives especially for the taxonomy and phylogeny of this complex order. Chiara Angelone. Institut Catala de Paleontologia, Universitat Autonoma de Barcelona, 08193 Cerdanyola del Valles, Barcelona, Spain, chiara.angelone@icp.cat Julia A. Schultz. Steinmann-Institut fur Geologie, Mineralogie und Palaontologie, Universitat Bonn, Nussallee 3, 53115 Bonn, Germany, schultzj@uni-bonn.de Margarita A. Erbajeva. Geological Institute, Siberian Branch, Russian Academy of Sciences, Ulan-Ude, Russia 670047, erbajeva@gin.bscnet.ru