The new specimens of the largest eugaleaspiform Nochelaspis maeandrine are redescribed from two localities of the Xishancun Formation in Qujing City, Yunnan Province, southwestern China. Nochelaspis is most suggestive of Yunnanogaleaspis from the same horizon, but differs in its slit-like median dorsal opening (length/width>6), much stronger inner cornual process, coarse stellate ornamentation, and the serrations along the edges of the median dorsal opening and headshield. The new findings reveal the morphological details on the ventral side of the headshield as well. The oralobranchial fenestra is covered by a large dermal ventral plate, which is decorated with dense, tiny granular tubercles, and aligned with six pairs of separated, large, and circular branchial openings. This condition is different from that of osteostracans, in which the oralobranchial fenestra is covered by numerous minute scales or larger dermal platelets, and the branchial openings are slit-shaped and covered by small skin flaps somewhat like those of elasmobranchs. However, the branchial openings of galeaspids and osteostracans are both located ventrally as in modern rays, indicating a benthic lifestyle dwelling on sandy or muddy substrates in a quiet marine environment.
Abundant mammalian fossils were uncovered during the field exploration for Nihewan beds at the beginning of the 1980s along Xinyaozi Ravine at Nangaoya Township of Tianzhen County, Shanxi Province in North China and the studied taxa indicate an age of the early Early Pleistocene. Recent studies on the rhino material not yet described show that there are at least two species of rhinocerotids: Elasmotherium peii and Coelodonta nihowanensis . There might be a third taxon provisionally named as Stephanorhinus cf. S. kirchbergensis due to incompleteness of the specimens. Since its morphometric characters are between S. kirchbergensis and C. nihowanensis , it might be a variety of one of the two species although it is more similar to the former than the latter. In the same way, The rhino specimens from Xiashagou named as Rhinoceros sinensis (?) by Teilhard de Chardin and Piveteau (1930) might be a variety of S. kirchbergensis or C. nihowanensis . The rhinocerotids uncovered so far from the Early Pleistocene deposits in the generalized Nihewan Basin including two certain species and two uncertain ones. The localities yielding E. peii include Xiashagou, Shanshenmiaozhui, Daheigou and Xinyaozi; those yielding C. nihowanensis include Xiashagou, Danangou, Donggutuo, Shanshenmiaozhui and Xinyaozi. R. sinensis (?) appeared only at Xiashagou and Stephanorhinus cf. S. kirchbergensis only at Xinyaozi.
The mastodont-grade proboscideans represent an important stage in the evolution of the group, establishing the basic pattern of the evolution of the crown groups of proboscideans. The research on mastodons has a history of more than 400 years. The classification and nomenclature have been revised and changed many times, and the problems in their evolution were fully reflected in the history of mastodon nomenclature. In this paper, we undertook a bibliographical research into the nomenclature and etymology of various mastodont groups, reviewing 175 translated Chinese names of mastodont-grade proboscideans, including 12 taxon names higher than the genus level, 46 genera, and 117 species, covering almost all the species of the mastodont radiation. On this basis, we review the principal phylogenetic hypotheses of mastodont interrelationships, and highlight problems in the classification and nomenclature of mastodonts. The evolution of the skull and mandible of mastodons is continuous in all clades, reflecting the same parallel evolution trend; while, although the morphological characteristics of cheek teeth across all lineages are not obvious, they are relatively stable in each lineage. Choerolophodontidae is the most robust monophyletic group within the mastodonts, of which Synconolophus may be a distinct, valid genus. Miomastodon and Pliomastodon of Mammutidae may both be valid, but they are not necessarily the direct ancestor of Mammut americanum . The phylogenetic relationship between Platybelodon danovi , P. grangeri and Aphanobelodon zhaoi within the Amebelodontidae is questionable, depending on whether the lower incisor section of P. danovi is the dentine rod structure or not, while Konobelodon britti in America may be a synonym of Torynobelodon loomisi . The species assigned to Konobelodon in Asia is possibly not amebelodontids, but probably attributable to Paratetralophodon , instead; Serridentinus of Gomphotheriidae may be a valid taxon, representing a trend towards somewhat zygodonty in Gomphotheriidae that terminated with the Cuvieroniinae. The Cuvieroniinae may only include Cuvieronius and Rhynchotherium , while other brevirostrine gomphotheres in America, such as Stegomastodon may have been evolved from a lineage of amebelodonts. Notiomastodon may be related to Sinomastodon , which itself may have originated from Pliomastodon (?) zhupengensis in southern China. The name Mastodon intermedius Teilhard de Chardin & Trassaert, 1937 (now Sinomastoodon intermedius ) has the senior primary homonym Mastodon intermedius Eichwald, 1831. We suggest that Sinomastodon intermedius should be replaced with its senior synonym-Sinomastodon sendaicus (Matsumoto, 1924).
Bayesian tip dating is a recently developed method to estimate divergence times and evolutionary rates. It overcomes several drawbacks in traditional stepwise approach. However, it also requires more knowledge about statistics. This paper hierarchically explains the theory and computation in the Bayesian tip-dating approach, and divides the whole process into prior for the divergence times, prior for the evolutionary rates, model for the character changes and Markov chain Monte Carlo algorithm, which are key components in this method. The aim is to provide a general guidance for paleontologists in empirical data analyses.