A new species of Argyromys (Rodentia, Mammalia) from the oligocene of the valley of lakes (Mongolia): its importance for palaeobiogeographical homogeneity across Mongolia, China and Kazakhstan

We describe a new species of Rodentia (Mammalia), Argyromys cicigei sp. nov. from Toglorhoi (fossil bed TGW-A/2a) in Mongolia and Ulantatal (fossil beds UTL 1 and UTL 7) in China. Its tooth morphology differs from the type species Argyromys aralensis from Akespe in Kazakhstan by smaller size and simpler structures. Argyromys has been assigned in different families of Muroidea, such as Tachyoryctoididae and Spalacidae. However, the presence of common characters indicates a closer relationship of Argyromys with the genera of Cricetidae s.l. (subfamilies Eucricetodontinae; Cricetopinae; Cricetodontinae and Gobicricetodontinae among others) from Asia than with the earliest representatives of Spalacidae or the endemic Tachyoryctoididae. Argyromys cicigei sp. nov. possesses a simple anterocone and anteroconid in the upper and lower first molars, respectively, which is characteristic for Cricetidae s.l. It has a flat occlusal surface in worn specimens; weakly-developed posterolophs; an oblique protolophule and metaloph on the upper molars and it lacks a labial anterolophid on the m1. These traits are also typical of the Oligocene genera Aralocricetodon and Plesiodipus, included in the subfamilies Cricetodontinae and Gobicricetodontinae respectively. The cladistic analysis performed here supports this hypothesis. The clade formed by Argyromys species is grouped with other cricetid taxa (s.l). Spalacids, however, form a different clade, as do the tachyoryctoids. Previous authors state that the Aral Formation (Kazakhstan) should be dated to the Oligocene instead of the Miocene, based on the presence of several taxa. The finds of Argyromys in both regions supports the statement that they are closer in age than previously thought. The occurrence of Argyromys in Kazakhstan, Mongolia and China evidences the biogeographic unity of the Central Asian bioprovince during the Oligocene

Vicariance and dispersal in southern hemisphere freshwater fish clades: a palaeontological perspective

Widespread fish clades that occur mainly or exclusively in fresh water represent a key target of biogeographical investigation due to limited potential for crossing marine barriers. Timescales for the origin and diversification of these groups are crucial tests of vicariant scenarios in which continental break‐ups shaped modern geographic distributions. Evolutionary chronologies are commonly estimated through node‐based palaeontological calibration of molecular phylogenies, but this approach ignores most of the temporal information encoded in the known fossil record of a given taxon. Here, we review the fossil record of freshwater fish clades with a distribution encompassing disjunct landmasses in the southern hemisphere. Palaeontologically derived temporal and geographic data were used to infer the plausible biogeographic processes that shaped the distribution of these clades. For seven extant clades with a relatively well‐known fossil record, we used the stratigraphic distribution of their fossils to estimate confidence intervals on their times of origin. To do this, we employed a Bayesian framework that considers non‐uniform preservation potential of freshwater fish fossils through time, as well as uncertainty in the absolute age of fossil horizons. We provide the following estimates for the origin times of these clades: Lepidosireniformes [125–95 million years ago (Ma)]; total‐group Osteoglossomorpha (207–167 Ma); Characiformes (120–95 Ma; a younger estimate of 97–75 Ma when controversial Cenomanian fossils are excluded); Galaxiidae (235–21 Ma); Cyprinodontiformes (80–67 Ma); Channidae (79–43 Ma); Percichthyidae (127–69 Ma). These dates are mostly congruent with published molecular timetree estimates, despite the use of semi‐independent data. Our reassessment of the biogeographic history of southern hemisphere freshwater fishes shows that long‐distance dispersals and regional extinctions can confound and erode pre‐existing vicariance‐driven patterns. It is probable that disjunct distributions in many extant groups result from complex biogeographic processes that took place during the Late Cretaceous and Cenozoic. Although long‐distance dispersals likely shaped the distributions of several freshwater fish clades, their exact mechanisms and their impact on broader macroevolutionary and ecological dynamics are still unclear and require further investigation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148368/1/brv12473_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148368/2/brv12473.pd

First evidence of a neonate dentition in pareiasaurs from the Upper Permian of Russia

Finds of juvenile parareptiles are rare in the fossil record. We describe partial upper dentition with large vacuities between bones belonging to a neonate pareiasaur (preserved skull fragment is 22.4 mm long). The specimen was collected within 5 m from a skeleton of an adult specimen of Deltavjatia vjatkensis (Hartmann-Weinberg, 1937) (Pareiasauridae) from red calcareous mudstones in the upper part of the Vanyushonkov Member of Ursulov Formation (Upper Permian, Upper Tatarian substage, Vishkil'skiy regional stage) of Kotel'nich locality, Vyatka River region, Russia. Referral to Deltavjatia vjatkensis is based on the presence of heterodont dentition: spatulate maxillary, triconodont vomerine and conical, palatine and pterygoid teeth located on well-developed palate ridges. This is the first positively identified record of the neonate pareiasaur dentition

Modeling impregnation process of glass fabrics by polyester binder under pressure

The article gives analysis of the need for process simulation when developing new methods of making dimensional products from fiberglass, in particular, during the transition from hand-molding technology to pressure impregnation technology. In this work the results of determining the basic parameters of filler (fib erglass), its behavior un-der applied compressive force and change pack porosity are presented. On the physical model we studied the way the resin passes through the porous space and defined coefficients of pro-determined permeability in two directions, time of impregnation of predetermined packet sizes, and degree of filling to a certain depth. The experimental result s were compared with the results of numerical calculation of the modified body orthotropic theory of heat conduction. The results of calculation of the duration of impregnation for model plane models provide high of performance of convergence with the results of the experiment, which enables the use of numerical methods for simulation of the process as applied to real structures. Using the experimental data obtained from the coef ficients of permeability of fiber system, we cal-culated the time of full impregnation of the actual product. During the calculations, we have changed the source data for the applied pressure and, varying the circuit supplying and removing the binder, determined the optimal parameters for which the filling of the pore space of the fiber system does not exceed the lifetime of the binder. Modeling allows us to observe the distribution of the binder in the flow of resin during the impregnation process. Application of numerical method allows us to achieve high quality products and to im-prove understanding of the production process

Structure and properties of composite materials from fibreglass wastes and thermosetting binder

The possibility of the use of ground fibreglass wastes as fillers and thermosetting resins as binders to manufacture the articles for household and constructive use have been studied. Parameters of the mechanical properties of materials with different fraction composition have been determined. Influence of the mechanical action on particle size has been studied. Experimental test for checking the possibility of component combination has been carried out. Quality of materials has been examined. Recommendations for the use of the existing technologies in the manufacture of articles have been worked out. The obtained results can be used in developing product design, in determining the areas and conditions of their effective application as well as in choosing technologies for their processing

Utilization of fiber composite products

The method for processing of fiberglass plastic is proposed for deriving of the fiber constituent, applied as reinforcing filler for producing secondary composite materials. It is proved by theory and experiments the influence of modes of shock-centrifugal mill to produce a fibrous component with the highest content of fibers with a length of more efficient. The obtained analytical regularities can be used to develop the design of the elements of the mill, as well as for the optimization of the grinding process

Combining of fiberfill and thermoplastic polymers

The article deals with an efficient and economic way of combination of the fiber composition from fiberglass waste and thermoplastic polymers. As the mixer of components the disk-extruder is used. The effectiveness of the proposed solutions was investigated and proved experimentally. The secondary composite materials having higher values of physical mechanical properties and longer fibers in the composition in relation to the analogous materials are gained in the screw extruder