Phymatolithon Foslie is one of the most studied and ecologically important genera of crustose coralline algae (CCA) due to their dominant abundance in various marine ecosystems worldwide. The taxonomy of the genus is complex and has been revised and updated many times based on morphological and molecular analyses. We report on a crustose coralline algal species collected in June 2011 via snorkeling in the subtidal zone along the beach Abu Qir on the Mediterranean coast of Egypt, as part of a larger macroalgal diversity survey in the region. The species shows significant sequence divergences (3.5%–14.8% in rbcL; 2.9%–11% in psbA) from other closely related Phymatolithon taxa. Morpho-anatomically, this species possesses the characters considered collectively diagnostic of the genus Phymatolithon, namely, thalli non-geniculate epithelial cells and non-photosynthetic and domed-shaped meristematic cells, usually as short with progressive elongation of their perithallial derivatives. Based on molecular and morphological analyses, we determined that these specimens encompass a new, distinct species that we herein name Phymatolithon abuqirensis. Including this new species, the total number of described Phymatolithon species found in the Mediterranean Sea is now six.

植硅体 Foslie 是研究最多和生态上重要的甲壳珊瑚藻 (CCA) 属之一，因为它们在全球各种海洋生态系统中占主导地位。该属的分类很复杂，根据形态学和分子学分析已经多次修订和更新。我们报告了 2011 年 6 月收集的壳状珊瑚藻物种通过在埃及地中海沿岸阿布基尔海滩沿岸的潮下带浮潜，作为该地区更大的大型藻类多样性调查的一部分。该物种显示出显着的序列差异（3.5%–14.8%红细胞大号; 2.9%–11% 在psba) 来自其他密切相关的植硅体分类群。形态解剖学上，该物种具有被认为是该属的集体诊断特征植硅体，即菌体非膝状上皮细胞和非光合作用和圆顶形分生细胞，通常随着它们的菌体周围衍生物的逐渐伸长而变短。基于分子和形态分析，我们确定这些标本包含一个新的、独特的物种，我们在此命名为Phymatolithon abuqirensis。包括这个新种，被描述的总数植硅体在地中海发现的物种现在有六种。