• A Lygodium japonicum BLAST analysis found four squalene cyclase-annotated isotigs. • Two of four isotigs were chimeric sequences due to incorrect assembly. • Two isotigs constituted a single hopene synthase-encoding gene, designated LJH. • Homology-based PCR isolated a squalene cyclase pseudogene distinct from the isotigs. Transcriptome mining is a powerful tool for gene discovery in plant sciences. Biosynthetic enzyme transcripts of specialized metabolites have been isolated using transcriptome datasets of non-model plants; however, this methodology has not been applied to fern metabolites. Herein, we attempted to isolate transcripts of squalene cyclases from the Lygodium japonicum transcriptome database. A BLAST search revealed the presence of four isotigs (12872, 12873, 33018, and 33763) annotated as squalene cyclase, two of which contained full-length open-reading frame sequences. However, both isotigs failed to be amplified; our investigation revealed them to be chimeric sequences due to incorrect assembly. We also revealed that part of isotigs 12873 and 33018 constituted a single gene, designated LJH . Conversely, homology-based PCR resulted in the isolation of a squalene cyclase homolog, LjSCx , distinct from the four isotigs. Biochemical characterization of LJH and LjSCx revealed that LJH is a hopene synthase gene and LjSCx is a pseudogene. These findings highlight the usefulness and limitations of transcriptome datasets, especially with respect to genes comprising a gene family.