An Oligocene giant rhino provides insights into Paraceratherium evolution

As one of the largest land mammals, the origin and evolution of the giant rhino Paraceratherium bugtiense in Pakistan have been unclear. We report a new species Paraceratherium linxiaense sp. nov. from northwestern China with an age of 26.5 Ma. Morphology and phylogeny reveal that P. linxiaense is the highly derived species of the genus Paraceratherium, and its clade with P. lepidum has a tight relationship to P. bugtiense. Based on the paleogeographical literature, P. bugtiense represents a range expansion of Paraceratherium from Central Asia via the Tibetan region. By the late Oligocene, P. lepidum and P. linxiaense were found in the north side of the Tibetan Plateau. The Tibetan region likely hosted some areas with low elevation, possibly under 2000 m during Oligocene, and the lineage of giant rhinos could have dispersed freely along the eastern coast of the Tethys Ocean and perhaps through some lowlands of this region.


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Policy information about availability of data All manuscripts must include a data availability statement. This statement should provide the following information, where applicable: -Accession codes, unique identifiers, or web links for publicly available datasets -A list of figures that have associated raw data -A description of any restrictions on data availability Tao Deng Apr 26, 2021 Photographs of the fossils were taken using a Nikon D850 camera; 3D scanners for capturing the geometry and producing a threedimension digital model of fossil were based on an Artec Spider; and the software using to collect data and establish matrix was Mesquite.
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MRI-based neuroimaging
Our study describe a new giant rhino based on a complete skull and mandible with the associated atlas, and an axis and two thoracic vertebrae of another individual from the Late Oligocene (26.5 million years ago) deposits in northwestern China. Phylogenetic and palaeogeographical analyses were performed. Based on the dispersal of giant rhinos and the history of transgression-regression cycles of the Tethys Ocean in the Tarim Basin during Paleogene, we discussed the paleo-elevation of the Tibetan Plateau.
Fossil and extant genera and species of the superfamily Rhinocerotoidea were used to compare with new fossils and to established the data matrix for cladistic analysis. Many localities situated south to or north to the Tibetan Plateau in Asia and a series of localities in the Tarim Basin were used to analyse paleogeography.
All samples from other species within the genus Paraceratherium are used for comparison. All genera of the giant rhino, other Paleogene rhinocerotoids (branching group), and additional 3 Neogene and Quaternary genera are used for the cladistic analysis to establish the phylogenetic relationship of the family Paraceratheriidae. Whenever possible, we selected taxa with well-preserved samples as well as distinct diagnosis to illustrate their shape outline, and included taxa once appeared in previous phylogenetic analyses to make a forceful comparison. We marked all localities with fossils of genus Paraceratherium in the paleogeographical analysis in order to display their dispersal history. In Supplementary Figure 3, we marked 21 classic localities in the Tarim Basin, from which typical formations with marine sediments and fossils have been discovered.
The fossil specimens described in this study were collected by a joint team of the Institute of Vertebrate Paleontology and Paleoanthropology and the Hezheng Paleozoological Museum from the Late Oligocene deposits near Wangjiachuan Village in Dongxiang County, Gansu Province, China The fossil specimens were discovered in May 2015, and prepared by three professional technicians from the Hezheng Paleozoological Museum under the supervision of the authors from December 2016 to February 2017. Since then, the specimens were studied by the authors.
No data are excluded.
The fossil specimens were housed in the Hezheng Paleozoological Museum, and are available on request; we provided detailed description of the methods and all the raw data, including character coding for phylogenetic analysis and measurements for comparison in the supplementary information, which can be used to reproduce all the results obtained in this study. The results reported in this study can be reproduced according to the methods clarified in the text.
Randomization is not applicable to this study, because this research studied an Oligocene giant rhino and performed phylogenetic and paleogeographical analyses to study the phylogeny and dispersal of giant rhinos during the Eocene and Oligocene.
Blinding is not applicable to this study.