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The inhibitory cascade (IC) represents a developmental model that explains the evolution of molar relative sizes, originally described in rodents but later validated in several mammalian groups. The IC comprises signalling molecules produced by the first molar buds that inhibit the development of subsequent molars and molecules from surrounding tissues that have opposite effects. Sloths, as xenarthrans, present many peculiarities in their dentition, like tooth and enamel loss, homodonty, and changes in the typically mammalian dental formula. Here, we test the existence of an IC and explore the evolution of the lower dentition in sloths. We studied the variability of molariform proportions in 20 specimens of the Late Pleistocene ground sloth Lestodon armatus. We also analysed molariforms proportions in 53 sloth genera to explore evolutionary trends. Our results show that the lower dentition of most sloths complies with the IC model, despite the difficulties of assessing dental homologies with other mammals. Furthermore, we tested the existence of different patterns among families, obtaining support for models taking mylodontids and orophodontids separately from the rest of sloths. Also, members of Mylodontidae show a unique IC pattern, with a slope considerably higher than 2 and an mf1 ≤ mf2 << mf3 configuration. This pattern could be related to the morphological adaptations to grazing showed by mylodontids during most of their evolutionary history.

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The locality Mikhailovka-5 is situated in the northern part of the Mikhailovka quarry in the northwest of the Kursk Oblast in central Russia. A rich mollusk fauna was collected along with small mammal remains from this lacustrine deposit located between Likhvinian (= Holsteinian) fossil soils and Valdayian (= Weichselian) periglacial deposits. The small mammal fauna is diverse, and includes numerous rodents, e.g., such indicative taxa as Arvicola ex gr. sapidus and Microtus ex gr. agrestis, a significant number of Clethrionomys glareolus and various insectivores. This assemblage closely corresponds to other Mikulino (= Eemian) faunas from the Russian Plain. The mollusk fauna includes a large number of terrestrial species, some of which have currently a more southern and western distribution. Both the molluskan and mammal faunas from Mikhailovka-5 indicate temperate climatic conditions, as evidenced by the diversity of insectivores, particularly the moles. Abundant remains of rodents of the genera Clethrionomys, Apodemus, and Microtus (Terricola) and of mollusks such as Acme, Macrogastra, Ruthenica, Punctum, and Acanthinula indicate the presence of extensive woodlands of mixed or broadleaf type, which were typical for this latitude during the Eemian interglacial. The palaeontological data provided in this paper, confirm that Mikhailovka-5 belongs to the Mikulino interglacial, as previously suggested by pedological arguments.

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The Middle Pleistocene site Bilzingsleben II is well-known for its wealth of vertebrate and archaeological remains. Of particular importance is the record of Homo erectus bilzingslebenensis. Most palaeontologists consider the find horizon as a primary vertebrate deposit formed during human occupation, while some archaeologists attribute its formation to turbulent gravitational mass flows, inundation or a combination of both. Here we present mortality profiles of the beavers Castor and Trogontherium to provide further arguments to this controversial discussion. The mortality profiles of Castor from Bilzingsleben II, Weimar-Ehringsdorf and Weimar-Taubach are largely identical indicating similar taphonomic filters that were effective in the formation of the find layers. Individuals, which were tentatively classified as suspected ±2–2½ year old beavers dominate by far in all three sites. The structure of these mortality profiles shows similarities to Stiner’s (1990) “prime dominated mortality pattern”, which is indicative of human hunting. This consideration is supported by the difference of the mortality profile of Trogontherium from Bilzingsleben II (dominance of older individuals) in relation to the profiles of non-hominin generated assemblages of Tegelen and Mosbach 2 (dominance of younger individuals). Thus, our data support the interpretation of the Palaeolithic find horizon of Bilzingsleben II as a primary vertebrate deposit, but not the gravitational mass flow and inundation hypotheses.

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Water voles are important key fossils of the Quaternary. Given their wide distribution, regional differences were expected to exist in different areas. Early hints on possible independent evolutionary trends of water voles in Italy came from palaeontology and specifically from the comparison of enamel differentiation (SDQ value) of the first lower molars between specimens from Italy and Germany. The data available at that time indicated that in the early Middle Pleistocene there were only minor enamel differences between first lower molars of water voles from these two geographical regions, whereas from the late Middle Pleistocene onwards, two lineages were clearly distinguished. Examination of mitochondrial DNA of extant Arvicola populations from across Europe by Wust-Saucy led to a similar conclusion that Arvicola populations from the Italian Peninsula had undergone independent evolution during the last 0.2 million years.

The inclusion of new fossil and extant Arvicola samples from Italy and Central Europe, together with the examination of additional morphological parameters of the occlusal surface (so-called van der Meulen indexes), have provided further support for the proposed evolutionary pattern. The combined analysis of length, SDQ and A/L index reveal a certain degree of intercorrelation and indicate an essentially continuous evolutionary trend. However, variations are discernible, related to the age and geographical origins of the samples, and become more clearly seen at least since the beginning of the Late Pleistocene. Italian samples have a characteristic tendency to grow larger, elongate the anteroconid, and have less derived SDQ. This corroborates the suggestion that Italian water voles underwent an evolutionary history distinct from that of their Central European counterparts. The differences in morphology may be related to a combination of etho-/ecological (aquatic or terrestrial habits) and palaeobiogeographical factors.

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The original fossil record of Allosorex stenodus Fejfar, 1966 from Ivanovce (late Ruscinian, MN 15b) is redescribed and supplemented by the description of so far unpublished fossil remains, including upper dentition (P4 and M3) and a humerus fragment as well as the enamel microstructure analysis of m2. Based on the critical evaluation of other fossil remains from sites in Romania, Hungary, and France, the Ivanovce fossils are so far the only unquestionable recorded finds of A. stenodus in Europe, which can be considered as a local early Pliocene (MN 15) endemic species. Its occurrence is connected with the forested karst area along a broad valley of “pre-Váh” River, ecologically and climatically resembling the environment of modern karst areas in south-eastern Asia. Based on enamel microstructure analysis and unique mandible and dentition morphological characters, a separate taxonomical status of the species is also discussed.

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The vertebrate locality of Dorkovo yielded a rich mammalian assemblage of which some large mammals have been studied, but not smaller mammals. The previous investigations correlated this fauna to the early Pliocene (early Ruscinian, MN 14). The present paper describes lagomorph remains which consist of one fragment of mandible and 106 isolated teeth. Four species are identified: Ochotona cf. antiqua, Prolagus sorbinii, Alilepus spassovi n. sp. and Trischizolagus crusafonti. The new species is characterised by the derived pattern of its p3 which has trigonid more stretched, enamel infolding stronger than in any other species of Alilepus, and the p3 lacks anteroflexid. The presence of four species of lagomorphs at Dorkovo is in agreement with the diversity dynamics of lagomorphs toward the end of late Miocene and during the early Pliocene in Eurasia, and in particular in Eastern Europe. The time range of the Dorkovo lagomorphs encompasses the Miocene/Pliocene boundary, and this is in agreement with the previous age assignments, i.e., earliest Pliocene, or early part of MN 14 mammalian zone.

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Over the last half a century, a massive amount of data has been gathered on Neogene rodents of Europe. Using the NOW database, we analysed changes in generic diversity during the Neogene and the beginning of the Quaternary. Studies as the present are useful for exploring major changes in diversity, but the pitfalls are many and varied. Whereas the quality of the fossil record is good, there are notable exceptions. Within our dataset, MN 1, MN 12 and MN 17 stand out for the limited number of localities available and the record of the eastern Mediterranean is clearly as yet poorer than that from central Europe and the Iberian Peninsula. The record can be influenced by incomplete faunal lists, outdated literature and unresolved taxonomies. In addition, the use of the MN system presumably obscures patterns, as it often does not allow for a co-eval comparison between various regions. Reconstruction of major patterns starts with the understanding of basic data. Despite all these limitations the results of this work indicate that the record for central Europe consistently shows higher diversity than lower latitudes. The highest peak in diversity is found in MN 15, but the record of the Iberian Peninsula shows no increase at that time. The rodent diversity is surprisingly constant during most part of the Neogene, the stronger variations being related to the diversification of the murinae and arvicolinae groups and decline of the cricetine.

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The Staniantsi-Mazgoš Basin is one of several Neogene intramontane basins in NW Bulgaria. Recent fieldwork in the open pit coal mine yielded material of an exceptional diversity of vertebrates from the uppermost Miocene. In particular, skeletal remains of a large Castorinae are very numerous and well-preserved. Here we perform a comparative morphological description of the postcranium of the Staniantsi-beaver and compare it with the extant Castor fiber and closely related fossil taxa, noting an overall high degree of similarity in many cases. Analyses of the functional anatomy confirm similar locomotor adaptations of the large Staniantsi-beaver and the extant Castor fiber. It is shown that the hindlimb exhibits typical adaptations for swimming and the forelimb is modified for a primary fossorial movement. Further, the caudal vertebrae indicate a flattened tail. Minor osteological differences can be used in a future clarification of the taxonomic status of this fossil castorine. In conclusion, the large Staniantsi-beaver seems to be equivalent to the extant Castor fiber and several fossil castorids in his locomotor adaptations and fits perfectly into the assumed swampy to lacustrine palaeoenvironment of the Staniantsi-Mazgoš Basin. Our results highlight the importance of the postcranium for reconstructing the palaeobiology and elucidating the taxonomy of fossil rodents.

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Here we report about the presence of fossils belonging to different beaver lineages from the late Miocene (MN 9, Vallesian) of Grytsiv (western Ukraine). Among them, nine isolated molars were assigned to Chalicomys jaegeri and described in detail here for the first time. Morphologically and metrically these specimens fit well into the range known for this species from other localities. The teeth are of different wear stages, mainly moderately or strongly worn. Two other teeth (a germ and one with a little wear), are tentatively identified as belonging to a smaller-sized beaver resembling Euroxenomys minutus. This is based mainly on their smaller size as measured at the occlusal surface. Taxonomic status and palaeoecology of Chalicomys jaegeri and other species of this genus are discussed in the paper.

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The maxillary presented in this work has been excavated in the middle Miocene karst filling Petersbuch 136 (Germany, Bavaria) and shows the oldest evidence of dental anomaly in a sciurid. The aberrant morphology, probably hyperdontia or no replacement of roots of deciduous teeth, affects the area of the P3, a tooth that is generally not well documented in the Spermophilinus record.

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In Asia, the first find of an eomyid rodent was reported almost one century after the first studies of the family Eomyidae in North America and Europe. Since then, eomyid rodents have been increasingly found in Asia particularly over the past two decades. Here, we review the Asian record of this family at the genus level. Currently, 22 species within 14 genera were reported from Asia, including seven endemic genera and rare materials of apeomyine eomyids. Eomyids emphasize the palaeogeographic importance of Asia in considering intercontinental dispersal events of small mammals. With newly compiled data for Asian eomyids, we also compare genus-level diversity trends through time among North America, Europe, and Asia. Despite data standardizations limited with respect to potential biases in the fossil record, we found that the Asian eomyid diversity closely follows ecological shifts induced by climate changes. In general, Asian eomyid genera disappeared earlier than their European counterparts. We suggest that this pattern is not dictated by differences in the quality of the fossil record and is related to the expansion of drier habitats over large areas of Asia.

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An isolated mandible of Carnivora (Mammalia) from the phosphorites of Quercy (France) is described as a new genus. It is compared with the amphicyonid genus Cynodictis, some primitive North American amphicyonids, and with European and North American Eocene carnivoraforms. I conclude that it is a primitive amphicyonid which may be dated to the middle or late Eocene.

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To the arcticle: Tonarová, P., Vodrážková, S., Hints, O., Männik, P., Kubajko, M., Frýda, J. (2019): Llandovery microfossils and microfacies of the Hýskov section, Prague Basin. – Fossil Imprint, 75(1): 25–43.

https://doi.org/10.2478/if-2019-0002

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To the article: Vianey-Liaud, M., Marivaux, L., Lehmann, T. (2019): A reevaluation of the taxonomic status of the rodent Masillamys Tobien, 1954 from Messel (Germany, late early to early middle Eocene, 48–47 m.y.). – Fossil Imprint, 75(3-4): 454–483.
https://doi.org10.2478/if-2019-0028