Suyin Ting

Gomphos elkema (Glires, Mammalia) from the Erlian Basin: Evidence for the Early Tertiary Bumbanian land mammal age in Nei-Mongol, China

Abstract Dental and postcranial specimens of Gomphos elkema, including lower and upper dentition and pedal elements, from the Huheboerhe locality, Erlian Basin, Nei-Mongol (Inner Mongolia), are described. Postcranial elements of Gomphos are similar to those of Mimolagus, suggesting affinity with lagomorphs. Gomphos elkema is a typical Bumbanian taxon, previously known only from Mongolia. Gomphos elkema specimens at Huheboerhe indicate occurrence of Bumbanian-equivalent beds and fauna in the region and suggest potential presence of the Paleocene–Eocene boundary in the Huheboerhe section.

Age and Correlation of Fossiliferous Late Paleocene–Early Eocene Strata of the Erlian Basin, Inner Mongolia, China

Abstract The Asian continent preserves a rich and diverse record of Paleogene mammal faunas and their evolution through time. The sequence of faunal succession is of key importance to our understanding of the origin and diversification of modern mammal groups, as phylogenetic data suggest that many major modern clades may be rooted in Asia. By calibrating the Asian fauna sequence within a chronostratigraphic framework, we can begin to compare patterns of succession on a global scale and constrain models for the origination and dispersal of modern mammal groups in the early Paleogene. The Erlian Basin of Inner Mongolia preserves Early Paleogene strata and mammal fossils assignable to the Gashatan, Bumbanian, and Irdin Manhan Asian Land Mammal Ages (ALMAs). We measured stratigraphic sections and analyzed the stable isotope composition of paleosol carbonates and paleomagnetic directions of rocks at three localities in the Erlian Basin. The data document patterns in lithology, carbon isotope composition, and magnetic polarity that are consistent at all three localities and allow us to present two constrained hypotheses for the correlation of the local stratigraphic sections. Within the resulting composite section, we are able to identify a secular decrease in the carbon isotope composition of paleosol carbonate that can be equated to a multimillion-year trend preserved in late Paleocene and early Eocene terrestrial and marine records. Using this trend and previously documented constraints on the age of the Bumbanian ALMA, the composite section is shown to correlate within the interval of time represented by chrons C26n–C24n of the Geomagnetic Polarity Timescale (GPTS). We outline three possible correlations of the sequence of magnetic polarity zones in our composite section to the GPTS and explore the biostratigraphic implications of these. All three possible correlations show that Gashatan faunas in Inner Mongolia occur within chron C24R, and the preferred correlation suggests that the Gashatan taxa may have persisted close to the Paleocene/Eocene boundary. If confirmed through further sampling, this result would imply that the first appearance of the modern mammal orders Primates, Artiodactyla, and Perissodactyla in Asia at the base of the Bumbanian ALMA did not significantly precede their first appearances in Europe and North America at the Paleocene/Eocene boundary. Fossil sites in the Erlian Basin promise to be central to resolving the debate about whether these clades lived and diversified in Asia before dispersing throughout the Northern Hemisphere at the Paleocene/Eocene boundary.

New Paleomagnetic and Stable‐Isotope Results from the Nanxiong Basin, China: Implications for the K/T Boundary and the Timing of Paleocene Mammalian Turnover

The Nanxiong Basin (Guangdong Province, China) preserves the most complete Asian stratigraphic record of the Cretaceous‐Paleogene (K/Pg) boundary extinction and the subsequent Paleocene mammalian radiation. Despite extensive study, the precise placement of the K/Pg boundary in the Nanxiong Basin sequence has been controversial, and the timing of subsequent mammalian turnover is poorly constrained. We present new paleomagnetic and geochemical data from the Late Cretaceous Pingling Formation (Nanxiong Group) and the overlying Paleocene Shanghu, Nongshan, and Guchengcun formations (Luofozhai Group). Our samples are directly correlated with previous geochemical and paleontological sampling localities, allowing for easy comparison with other local proxy records. Results indicate that the traditional placement of the K/Pg boundary at the base of a chaotic channel sandstone bed marking the highest stratigraphic appearance of dinosaur eggshell fragments and lowest stratigraphic appearance of Paleocene mammalian fossils lies about two‐thirds of the way up Chron C29R, consistent with the placement of the boundary in all other well‐documented sections. The average carbon isotope composition of paleosol carbonates decreases by >2‰ in the Early Paleocene, consistent with a major disruption to global carbon cycling after the K/Pg boundary. Constraints on the age of the first major Cenozoic mammalian turnover event in Asia (the Shanghuan‐Nongshanian Asian Land Mammal Age boundary) support its placement near the top of Chron C27N, which coincides with a similar turnover in North America and geochemical changes recorded in several deep sea cores.

The osteology of Matutinia (Simplicidentata, Mammalia) and its relationship to Rhombomylus

Abstract New dental, cranial, and postcranial specimens of the eurymylid Matutinia nitidulus from the early Eocene Lingcha Formation, Hengyang Basin, Hunan Province, China, are described. These materials are among the best of basal gliroid mammals from Asia. Matutinia is similar to Rhombomylus in general tooth and cranial morphologies, including an expanded hypocone shelf on the upper cheek teeth and a complex zygomatic arch. These features distinguish the two genera from other eurymylids such as Heomys and Eurymylus. Matutinia differs from Rhombomylus in having lower crowned and less lophate cheek teeth, fewer bony septa in the mastoid chamber, a lower promontorium, and a carotid foramen in the ear region. Based on the new material, we consider Matutinia a valid genus, not a junior synonym of Rhombomylus.

NEW EARLY EOCENE MAMMALIAN FOSSILS FROM THE HENGYANG BASIN, HUNAN CHINA

Abstract New fossil mammal materials found in the upper Lingcha Formation of the Hengyang Basin, Hunan, China, include a complete skull of Hapalodectes hetangensis and a taxon new to the fauna, Dissacus zengi, n. sp. H. hetangensis is the morphologically least derived species of the genus and currently is the earliest known record of the genus. D. zengi, n. sp. is the second Asian early Eocene record of the genus and represents the last occurrence of the genus in Asia. The Lingcha Formation includes two fossiliferous intervals. The upper contains about 12 species belonging to 7 mammalian orders, and the lower has yielded one mammalian species and one reptilian species. Biostratigraphic, chemostratigraphic, and magnetostratographic study in the Lingcha Formation indicates that the transient carbon isotope excursion that marks the Paleocene–Eocene boundary as currently advocated is present in the upper Lingcha Formation. The fauna from the upper Lingcha Formation occurs within the excursion interval, and is of earliest Eocene age. It is correlative with the Wasatchian-0 faunal zone in the Big Horn Basin, Wyoming, North America. The lower Lingcha Formation is of Paleocene age.