Chrysochromulina ephippium is a marine haptophyte microalga in the genus Chrysochromulina, class Prymnesiophyceae, order Prymnesiales. The specific epithet ephippium, from Latin meaning saddle, describes a distinctive saddle-shaped morphological feature of the organism — most likely a scale type visible under electron microscopy that is diagnostic for this species. Scale morphology, haptonema length, and cell dimensions collectively define species boundaries within the genus. C. ephippium has been recorded from Norwegian coastal marine waters, a region extensively surveyed for haptophyte diversity during the mid-to-late twentieth century by Norwegian phycologists including Magne Parke and Irene Manton. These surveys established Norway as a center of described Chrysochromulina diversity, with many type specimens collected from fjords and coastal shelf areas. The species is a nanoplankton organism adapted to pelagic coastal habitats, where it occupies a niche as a photosynthetic primary producer, potentially supplemented by phagotrophic feeding on bacteria. Chrysochromulina species contribute to marine carbon cycling and serve as food for microzooplankton and other planktonic grazers. The cell's golden-brown pigmentation reflects a chloroplast composition rich in chlorophylls a and c and fucoxanthin-type carotenoids, shared across the Prymnesiophyceae. C. ephippium has not been formally evaluated under IUCN criteria and is classified as Not Evaluated, consistent with the general approach to marine nanoplankton taxa whose global population status cannot be readily estimated.