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Estimating body mass from the astragalus in mammals

100%

Tsubamoto T.

Acta Palaeontologica Polonica

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2014

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tom 59

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nr 2

Astragalar fossils have been intensively studied as an indicator of the functional morphology and phylogenetic relationships of mammals. However, relatively few studies have investigated the relationship between astragalar size and body mass, usually with a focus on a particular taxonomic group. Here, univariate and multiple regression models are used to analyze the relationship between astragalar size and body mass based on an extensive sample of extant land mammals (11 orders, 48 species, 80 individuals; body mass ranging from 18 g to 3.4 t). The analyses revealed the size of the tibial trochlea to be a better predictor of body mass than the total size of the astragalus. Based on these results, estimates of the body mass of several Paleogene land mammals were calculated and compared to those of previous studies. Thus, for example, the body mass of “Baluchitherium”, the largest terrestrial mammal known to date, was estimated at about 10–15 t.

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A new tritylodontid synapsid from Mongolia

51%

Watabe M., Tsubamoto T., Tsogtbaatar K.

Acta Palaeontologica Polonica

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2007

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tom 52

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nr 2

The Upper Jurassic Ulaan Malgait Beds in the Shar Teg locality of southwestern Mongolia have yielded remains of a new tritylodontid therapsid (Synapsida), Bienotheroides shartegensis sp. nov. The specimen consists of a fragmentary skull associated with lower jaws. It is assigned to Bienotheroides based on its short snout, a premaxilla−palatine contact, very reduced maxilla, relatively rounded corner of upper postcanine teeth (PC), and PC cusp formula of 2−3−3. It differs from the other species of Bienotheroides in having a much more reduced middle mesial cusp of PC. It further differs from B. zigongensis and B. ultimus in having shorter and wider PC, from B. ultimus in lacking a projection at the middle mesial margin of PC, and from B. wansienensis in lacking the vestigialmost mesiobuccal cusp of PC and in lacking a diastema between upper I1 and I2. This is the first discovery of the Tritylodontidae in Mongolia. This discovery extends the taxonomic (morphological) diversity and geographic range of Bienotheroides and underlies the success of the genus in the Middle to Late Jurassic biota of eastern Eurasia.

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Discovery of a crocodyliform tooth from the upper Eocene Ergilin Dzo Formation, Mongolia

45%

Iijima M., Tsubamoto T., Tsogtbaatar K., Chinzorig T., Baasankhuu S.

Acta Palaeontologica Polonica

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2019

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tom 64

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nr 4

Although the distribution of Asian crocodyliforms was extended northwards during the Paleocene–Eocene greenhouse world, the fossil record in northern Asia becomes scarce towards the end of the Eocene. We here report the first crocodyliform (an isolated tooth) from the upper Eocene Ergilin Dzo Formation of southeastern Mongolia, the mammalian fauna of which defines the Ergilian Asian Land Mammal Age. The conical non-recurved crown, the near complete root with the central resorption facet, and its late Eocene age suggest the crocodyliform affinity of the tooth. The current finding represents one of the northernmost occurrences of crocodyliforms in the upper Eocene of Asia (paleolatitude ca. 49°30’ N), and demonstrates that SE Mongolia probably met thermal requirements of crocodyliforms during the late Eocene.

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New Early Cretaceous spalacotheriid symmetrodont mammal from Japan

45%

Tsubamoto T., Rougier G. W., Isaji S., Manabe M., Forasiepi A. M.

Acta Palaeontologica Polonica

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2004

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tom 49

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nr 3

We describe a new spalacotheriid (acute−angled) “symmetrodont” (Mammalia, Trechnotheria), Symmetrolestes parvus gen. et sp. nov., from the Lower Cretaceous, likely Barremian, Kitadani Formation of the Tetori Group, central Japan. The specimen consists of a fragmentary right lower jaw with first incisor and five preserved postcanine teeth (interpreted as p5–m4). Symmetrolestes has acute−angled molariforms with complete shearing surfaces on the para– and protocristids, and relatively tall crowns, features that are referable to Spalacotheriidae. Symmetrolestes is more derived than zhangheotheriids in having complete shearing surfaces, taller crowns, and more complete cingulids. It differs from other spalacotheriids in having fewer molariforms (m1–4), higher number of premolariforms (p1–5), and gradual transition between premolariforms and molariforms. Our cladistic analysis of 29 characters shows Symmetrolestes as the sister group of the remaining Spalacotheriidae. This node is supported by only one character (Bremer support: 1) and therefore not particularly stable. The remaining spalacotheriids are arranged in a fully pectinated tree conforming to the topology of the previous researchers, in which Spalacolestinae occupy an apical position. The combination of the occurrences of a primitive spalacotheriid, Symmetrolestes, in Japan and of Zhangheotheriidae, which is the sister taxon of Spalacotheriidae, in China suggests a possibility for an East Asian origin of Spalacotheriidae, although it implies long ghost lineages for the latest Jurassic to Early Cretaceous East Asian “symmetrodonts”.

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Middle Eocene ungulate mammals from Myanmar: a review with description of new specimens

45%

Tsubamoto T., Egi N., Takai M., Sein C., Maung M.

Acta Palaeontologica Polonica

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2005

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tom 50

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nr 1

We review an ungulate mammalian fauna of the Eocene Pondaung Formation, central Myanmar, and herein describe new dental specimens. The taxa newly recognized in the Pondaung Formation are two indeterminate bunodont artiodactyls, two small “eomoropid” perissodactyls (Eomoropussp. cf. E. minimus and an indeterminate “eomoropid”), and a new deperetellid perissodactyl genus, Bahinolophus, which is established for Deperetella birmanica from the Pondaung Formation. The Pondaung ungulate fauna consists of 29 species (14 families and 18 genera): one species of an indeterminate small ungulate, 12 species (six genera in six families) of artiodactyls, and 16 species (11 genera in seven families) of perissodactyls. Although both Pondaung artiodactyls and perissodactyls are abundant and taxonomically diverse, the former are less diversified in generic numbers than the latter, but are nearly equal to the latter in abundance. Anthracotheriid artiodactyls and brontotheriid and amynodontid perissodactyls are the most abundant elements in the fauna. The estimated paleoecologies of the included taxa, the geologic and geographic evidence, and cenogram analysis suggest that the paleoenvironment of the Pondaung fauna was forested/woodland vegetation with humid/subhumid moisture and large rivers, which were located not far from the eastern Tethyan Sea. The age of the Pondaung fauna is independently correlated with the latest middle Eocene only on the basis of the stratigraphic, microfossil, and radiometric evidence, yielding a result consistent with mammalian faunal correlations. On the other hand, the Pondaung fauna includes many artiodactyl taxa compared to other middle Eocene faunas of East Asia and shows relatively high endemism at the generic level, implying that the Pondaung fauna is not formally included in the Eocene Asian Land Mammal “Ages” system.

Ograniczanie wyników

5 Acta Palaeontologica Polonica

5 Tsubamoto T.

2 Tsogtbaatar K.

1 Baasankhuu S.

1 Chinzorig T.

1 Egi N.

1 Forasiepi A. M.

1 Iijima M.

1 Isaji S.

1 Manabe M.

1 Maung M.

1 Rougier G. W.

1 Sein C.

1 Takai M.

1 Watabe M.

1 2019

1 2014

1 2007

1 2005

1 2004

Estimating body mass from the astragalus in mammals

A new tritylodontid synapsid from Mongolia

Discovery of a crocodyliform tooth from the upper Eocene Ergilin Dzo Formation, Mongolia

New Early Cretaceous spalacotheriid symmetrodont mammal from Japan

Middle Eocene ungulate mammals from Myanmar: a review with description of new specimens