# First decoding and characterization of the mitogenomes of the crocodile newts Tylototriton anguliceps and T. ngoclinhensis (Caudata, Salamandridae) from Vietnam and a phylogenetic assessment of the genus Tylototriton

## TL;DR

This study decodes the mitochondrial genomes of two crocodile newt species from Vietnam and provides new insights into their evolutionary relationships.

## Contribution

The first complete mitochondrial genomes of Tylototriton anguliceps and T. ngoclinhensis are assembled and a mitogenome misidentification is corrected.

## Key findings

- The mitochondrial genomes of T. anguliceps and T. ngoclinhensis each contain 37 genes, typical of vertebrates.
- Phylogenetic analysis confirms the taxonomic placement of the two species into different subgenera.
- A previously misidentified mitogenome is re-assigned to T. maolanensis, providing its first complete mitogenome.

## Abstract

Tylototriton
anguliceps and T.
ngoclinhensis are two species of crocodile newts native to Vietnam. In this study, we assemble and describe for the first time the complete mitochondrial genomes of T.
anguliceps (16,720 bp) and T.
ngoclinhensis (16,260 bp). Both genomes consist of 37 genes, which is consistent with most other vertebrates, including 13 protein-coding genes (PCGs), 22 transfer RNAs (tRNAs), and two ribosomal RNAs (rRNAs). The arrangements of these mitochondrial genes are the same in T.
anguliceps and T.
ngoclinhensis, but some genes have slight differences in their lengths, start codons, and stop codons. Phylogenetic analysis using 13 PCGs from the mitogenomes as well as concatenated 16S and ND2 sequences confirm the taxonomic identities of the samples, with T.
anguliceps belonging to the subgenus Tylototriton and T.
ngoclinhensis to the subgenus Yaotriton. Furthermore, the phylogenetic analysis reveals that the previously assembled mitogenome (GenBank accession KR733683) thought to represent T.
wenxianensis is likely belongs to T.
maolanensis, thus providing the first mitogenome for this species. This study’s re-identification and the completion of two new mitogenomes provide a total of three new mitogenomes for future studies: those of T.
anguliceps, T.
ngoclinhensis, and the re-identified T.
maolanensis. The new mitogenomes can contribute valuable data for future molecular and evolutionary studies, as well as a basis for conservation genomics of the genus Tylototriton and other salamanders.