Vernayini Liu, Zhao, Liu & Chen 2025, tribe nov.

Vernayini Liu, Zhao, Liu & Chen, tribe nov. Etymology. The tribal name is formed by adding to the stem of the name of the type genus Vernaya, the suffix ini; thus, the name of the tribe becomes Vernay + ini = Vernayini. Type genus. Vernaya Anthony, 1941. Genera included. The single genus Vernaya comprises four species: Vernaya fulva (Allen, 1927), Vernaya foramena Wang, Hu & Chen, 1980, Vernaya meiguites Zhao, Li, Wang, Jiang, Liu & Chen, 2023 and Vernaya nushanensis Zhao, Liu, Jiang, Liu & Chen, 2023. Diagnosis. Vernayini is a tribe of small, arboreal, nocturnal rodents within the subfamily Murinae, which are well-adapted for climbing. These rodents are characterized by their medium-sized bodies, long, soft fur, and a unique combination of morphological features that distinguish them from other rodent groups. The hindfoot is less than 25 mm in length, and the total skull length is under 35 mm. Notably, the tail is particularly long, approximately twice the length of the head and body combined, and it is covered with fine scales, remaining hairless. Both the fifth digit of the forefoot and the first digit of the hindfoot are equipped with flattened nails, with the thumb capable of opposing the other fingers. The first digit of the hindfoot is semi-opposed and has a flattened nail instead of a claw, and both the fifth finger and the fifth toe have one claw each. The skull of Vernayini rodents features a longitudinal depression in the interorbital region, which also frequently contains two unossified sockets. The molar morphology of this tribe is quite distinctive, featuring an incisive foramen that extends backward to the front of the first molar. The third molar, M 3, is notable for its two tabular transverse ridges. Furthermore, the posterior lobe of the third transverse ridge on the first molar, M 1, is significantly different from what is seen in Rattini and Micromyini. Members of this tribe are skilled climbers, frequently active on large trees and plants like bananas. Their activity peaks during the morning, and their diet includes plant fruits, seeds, and insects (Pan et al. 2007; Smith and Xie 2008; Wei et al. 2022). Distribution. Vernayini is primarily found in the mountainous regions of southwestern China, extending into northern Myanmar. The four species within this tribe have distinct distribution patterns (Zhao et al. 2023), as follows: Vernaya fulva: found in western Yunnan Province, China, west of the Lancang River, and extends into northern Myanmar. Vernaya foramena: distributed in the Qinling Mountains of northern Sichuan, southern Gansu, southwestern Shaanxi, central Sichuan, the Qionglai Mountain District in western Sichuan, and northeastern Chongqing. Vernaya meiguites: distributed in the Meigu Dafengding National Nature Reserve, Mabian Dafengding National Nature Reserve, and adjacent areas, as well as the Gongga Mountains in the middle of the Hengduan Mountains. Vernaya nushanensis: found in Xuemeng Mountain, Lushui, Caojian, Dali, Yunnan Province, China, likely with the Lancang River (upper Mekong River in China) as its eastern boundary. The divergence of arboreal animals may be related to climatic and geological movements. Both Vernaya and Micromys are climbing species. Micromys is found in various regions of the world, including Myanmar, India, Vietnam, and Russia. In China, its distribution extends to Sichuan, Chongqing, Yunnan, and the southern part of Shaanxi (Wei et al. 2022). This distribution overlaps with the distribution of Vernaya species. According to the divergence time results, we noticed that the divergence of Micromys and Vernaya occurred approximately 12 Ma ago. At this time, what caused the two genera to diverge caught our attention. During the 14–12 Ma, the Qinghai-Tibetan Plateau (QTP) is thought to have experienced a rapid uplift (Coleman and Hodges 1995; Dettman et al. 2003). Moreover, the uplift of the Sanjiang area in the southern section of the Hengduan Mountains is believed to have occurred at 25–17 Ma and 13–8 Ma (Zhong and Ding 1996). These events have created complex land conditions and diversified climate evolution (Wu et al. 2001), leading to the differentiation and evolution of specific species. Therefore, based on these findings, we speculate that the two climbing genera, Micromys and Vernaya may have been closely related in the early stage; later, due to the uplift of the QTP and the change in climate, the habitats of the two have changed and occupied different ecological niches, which led to their divergence. Moreover, should Vernaya and Micromys be subject to distinct selective pressures within their mitochondrial genomes, the discovery of adaptive sites that fuel speciation is a thrilling prospect that beckons us to delve deeper into this evolutionary enigma.