<i>Aleuritopteris hainanensis</i> (Pteridaceae), a New Species From Hainan, China

<i>Aleuritopteris hainanensis</i>, a new fern of Pteridaceae from Hainan Province, China, is described and illustrated. Morphologically, <i>A. hainanensis</i> closely resembles <i>A. squamosa</i>, with both species bearing densely scaly fronds. However, the fertile fronds of <i>A. squamosa</i> (10.7-25.9 cm) are significantly longer than the sterile fronds (4.1-10.7 cm), whereas in <i>A. hainanensis</i>, the sterile (9.4-13 cm) and fertile fronds (10.1-14.1 cm) are nearly equal in length. In addition, the stipe and abaxial lamina scales of <i>A. hainanensis</i> are broadly lanceolate with nearly entire margins, while those of <i>A. squamosa</i> are lanceolate with margins erose-serrulate. Plastomes analysis futher reveals that the genetic distance between <i>A. hainanensis</i> and <i>A. squamosa</i> is significantly greater than the typical intraspecific variation, supporting the recognition of <i>A. hainanensis</i> as a distinct species. According to IUCN criteria, we propose that <i>A. hainanensis</i> should be categorized as a Vulnerable (VU) species.