Nguyen Truong Son

Mammalian skull heterochrony reveals modular evolution and a link between cranial development and brain size

The multiple skeletal components of the skull originate asynchronously and their developmental schedule varies across amniotes. Here we present the embryonic ossification sequence of 134 species, covering all major groups of mammals and their close relatives. This comprehensive data set allows reconstruction of the heterochronic and modular evolution of the skull and the condition of the last common ancestor of mammals. We show that the mode of ossification (dermal or endochondral) unites bones into integrated evolutionary modules of heterochronic changes and imposes evolutionary constraints on cranial heterochrony. However, some skull-roof bones, such as the supraoccipital, exhibit evolutionary degrees of freedom in these constraints. Ossification timing of the neurocranium was considerably accelerated during the origin of mammals. Furthermore, association between developmental timing of the supraoccipital and brain size was identified among amniotes. We argue that cranial heterochrony in mammals has occurred in concert with encephalization but within a conserved modular organization.

Description of a New Genus and Species of Rodent (Murinae, Muridae, Rodentia) from the Tower Karst Region of Northeastern Vietnam

Abstract Tonkinomys daovantieni, a new genus and species of murid rodent in the Dacnomys Division, is described. It is represented by 14 adults collected from talus habitats in the forested tower karst landscape of the Huu Lien Nature Reserve of northeastern Vietnam. The combination of semispinous, dense, grayish black fur covering upperparts; a dark gray venter; gray ears; a thick, bicolored tail considerably shorter than length of head and body; and large, extremely bulbous footpads is unlike any other species of Indomalayan murid. Body size and build of the new rat, along with some cranial features, are similar to the Thai Leopoldamys neilli, but other cranial traits coupled with molar occlusal patterns resemble morphology in species of the Indomalayan Niviventer, Chiromyscus, and Saxatilomys. The new species is petricolous, includes insects in its diet, and was found only in talus composed of large limestone blocks. Its distribution in the reserve is likely patchy. Whether this limestone rat is restricted to the extensive karst regions of northeastern Vietnam or also occurs in southern China and elsewhere in the northern karst landscapes of Indochina, and Vietnam in particular, will be known only by conducting surveys in limestone regions outside of northeastern Vietnam.

Revealing cryptic bat diversity: three new Murina and redescription of M. tubinaris from Southeast Asia

Based on a series of specimens collected in Cambodia and Vietnam, this paper describes 3 new species of tube-nosed bats belonging to the Murina “suilla-group” (Vespertilionidae: Murininae). We provide detailed accounts of their external and craniodental morphology, including a suite of standard measurements, and compare the new taxa with all other members of the group currently recognized in Southeast Asia. The 1st new species was previously included in M. tubinaris (Scully, 1881) but is considered distinct due to differences in external and craniodental features. This new species is widespread in continental Southeast Asia and relatively well represented in museum collections, whereas the other new species are known only from a few specimens collected at scattered localities. The new taxa are known only from forested areas, which highlights the incompleteness of existing knowledge and strong potential for further discoveries in the region.

A survey of small mammals from Huu Lien Nature Reserve, Lang Son Province, Vietnam

ABSTRACT A survey of the small mammals of Huu Lien Nature Reserve, Lang Son Province, Vietnam (21°40′52″N, 106°20′28″E) resulted in the capture of 187 specimens representing 21 species of bat, insectivore, and rodent: Suncus etruscus, Rhinolophus pearsonii, Rhinolophus pusillus, Rhinolophus stheno microglobosus, Aselliscus stoliczkanus, Hipposideros armiger, Hipposideros larvatus, Harpiocephalus harpia, Pipistrellus paterculus, Scotomanes ornatus, Callosciurus erythraeus, Dremomys rufigenis, Niviventer fulvescens, Niviventer langbianis, Tonkinomys daovantieni, Rattus andamanensis, Rattus losea, Rattus tanezumi, Mus caroli, Rhizomys pruinosus, and Atherurus macrourus. In addition Ratufa bicolor and Tamiops sp. are reported from observations. The recently described genus and species Tonkinomys daovantieni is currently known only from material collected during the present survey and is apparently endemic to karst habitats in northeastern Vietnam.

Molecular phylogeny of East and Southeast Asian fossorial moles (Lipotyphla, Talpidae)

Abstract The diversity of fossorial moles in East and Southeast Asia is contained in the 2 species-rich genera Mogera (8 species) and Euroscaptor (8 or more species), and the 3 monospecific genera Scapanulus, Scaptochirus, and Parascaptor. To better understand the evolution and biogeography of these fossorial moles, we conducted molecular phylogenetic analyses using mitochondrial cytochrome-b (Cytb; 1,140 base pairs [bp]) and 12S rRNA (approximately 830 bp) and nuclear recombination activating gene 1 (Rag1; 1,010 bp) gene sequences from 5 species of Euroscaptor, 6 of Mogera, and the single species of Scaptochirus. Phylogenetic estimates revealed 5 distinct lineages of East and Southeast Asian fossorial moles: Mogera, Scaptochirus, Euroscaptor mizura, E. parvidens, and E. malayana–E. klossi–E. longirostris. Our results support the monophyly of Mogera but not Euroscaptor, indicating a need for taxonomic revision of the latter genus. We hypothesize that Mogera originated in the central portion of its range and then dispersed to peripheral islands, such as Taiwan and the Japanese Islands. The fragmented distribution of Southeast Asian Euroscaptor presumably arose from habitat competition (invasion) from Mogera species, long-range dispersal, vicariance events, or a combination of these, explaining the high species richness of fossorial moles in this region.

The reds and the yellows: a review of Asian Chrysopteron Jentink, 1910 (Chiroptera: Vespertilionidae: Myotis)

Abstract Chrysopteron Jentink, 1910 is 1 of the 7 subgenera of Myotis Kaup, 1829 recognized by Tate that traditionally comprises Asian and African species characterized by conspicuously parti-colored wing membranes. Definition of Myotis subgenera has long challenged taxonomists and prior to the present study the systematic status of numerous forms within Chrysopteron remained unclear. Following examination of material (including available type specimens) in 21 European, North American, and Asian collections, and using morphological (external, cranial, and dental characters) and genetic data, we evaluate the validity of the Chrysopteron subgenus, revise the taxonomy of the named Asian forms, and review their distinguishing characters, distribution, and taxonomic history. We argue that Chrysopteron is an available name for a monophyletic “Ethiopian clade” recovered with high support in our analyses, which comprises species characterized by striking reddish or yellowish dorsal fur that strongly differentiates them from congeners. We also determine that M. formosus sensu lato contains several morphologically distinct forms, some of which occur in sympatry and some in widely separated localities. A morphological key is provided for all Asian species of Chrysopteron revealed by our study: M. bartelsi Jentink, 1910 (Java and Bali), M. formosus (Hodgson, 1835) (Afghanistan, India, Nepal, China, Taiwan, and Vietnam), M. hermani Thomas, 1923 (Sumatra, Thailand, and Malaysia), M. rufoniger (Tomes, 1858) (Korea, Japan, China, Taiwan, Laos, and Vietnam), M. rufopictus (Waterhouse, 1845) (Philippines), and M. weberi (Jentink, 1890) (Sulawesi).

Patterns of Postcranial Ossification and Sequence Heterochrony in Bats: Life Histories and Developmental Trade-Offs

The recently increased interest in studies on sequence heterochrony has uncovered developmental variation between species. However, how changes in developmental program are related to shifts in life-history parameters remains largely unsolved. Here we provide the most comprehensive data to date on postcranial ossification sequence of bats and compare them to various boreoeutherian mammals with different locomotive modes. Given that bats are equipped with an elongated manus, we expected to detect characteristic heterochronies particularly related to wing development. Although heterochronies related to wing development were confirmed as predicted, unexpected heterochronies regarding the pedal digits were also found. The timing of ossification onset of pedal phalanges is earlier than other mammals. Particularly, bats deviate from others in that pedal phalanges initiate ossification earlier than manual phalanges. It is known that the foot size of new born bats is close to that of adults, and that it takes several weeks to month until the wing is developed for flight. Given that the foot is required to be firm and stable enough at the time of birth to allow continued attachment to the mother and/or cave walls, we suggest that the accelerated development of the hind foot is linked to their unique life history. Since the forelimb is not mature enough for flight at birth and requires extended postnatal time to be large enough to be fully functional, we postulate that bats invest in earlier development of the hindlimb. We conclud that energy allocation trade-offs can play a significant role in shaping the evolution of development.

A new species of mole of the genus Euroscaptor (Soricomorpha, Talpidae) from northern Vietnam

Abstract A new species of talpine mole from northern Vietnam is described and compared with other species of the genus Euroscaptor. This small mole was assigned to the genus Euroscaptor on the basis of its dental formula, but it also shows unique morphological and karyological characteristics. The new species is externally similar to E. parvidens from southern Vietnam, possessing warty protuberances on the muzzle not seen in other members of this genus. The tail of the new species is much shorter than in E. parvidens and E. malayana, both known to have short tails. The tail is not visible under the fur in the dorsal view, giving it an almost tailless appearance. The skull of the new species is similar to that of E. longirostris, but the palate is characteristically wider. The molars of the upper jaw are of a simple triangular shape, and there is no hypoconulid in the lower molars. The diploid number of the new species was determined to be 2n  =  38, which is a new karyotype for this genus. This mole inhabits the lower elevational areas of northern Vietnam and is partially peripatric with E. longirostris in the type locality. Because of the distribution of another taxon in northern Vietnam, Mogera latouchei, the ecological relationships among 4 species of Vietnamese moles also is discussed.

Description of a New Species of the Genus Aselliscus (Chiroptera, Hipposideridae) from Vietnam

Trident bats found in mainland Southeast Asia are currently subsumed into a single species, Aselliscus stoliczkanus. In this study, we examined morphological and genetic data from different populations from Southeast Asia, with a special focus on specimens from Vietnam. Our analyses support the existence of a further species of Aselliscus in northeastern Vietnam that separated from A. stoliczkanus sensu lato (s.l.) during the late Miocene. Within the latter taxon, we identified five geographic lineages that diverged from each other during the Plio-Pleistocene epoch. Some of them may also correspond to further separate taxa, but additional molecular and morphological data are needed to test this hypothesis. Herewith, based on the combined evidences we describe the northeastern Vietnamese population as a separate species.

Description of a new species of Myotis (Vespertilionidae) from Vietnam

During the examination of a series of specimens, formerly referred to Myotis montivagus, recently collected in Vietnam and Lao PDR, we found that they differ in several important ways from any species formerly included in M. montivagus. We describe them as a new species characterised by a relatively long forearm, moderately long ears, flat cranial profile and wide anteorbital bridge. Based on characters classically used to separate the ‘subgenera’ of Myotis the new species shows affinities to both the nominate subgenus ‘Myotis’ and ‘Selysius’. Our morphological investigations support recent phylogenetic analyses showing that the former ‘subgenera’ of Myotis are in fact paraphyletic groups, even within Southeast Asia. Nevertheless, many of the external and craniodental features formerly used to separate these subgenera provide a practical means of grouping species. Using these characters we provide an identification key to identify the new species, as well as other currently recognized medium and large sized, small-footed Myotis species from the Indomalayan Region.