Cruciformaster

Lore & Background

The Cruciformaster fossil material was discovered in outcrops of the Calcaire de Ménerbes Formation near the village of Ménerbes in southeastern France, on the Lacoste plateau north of the Lesser Luberon Massif. Two individuals are known, preserved together on a single limestone slab. The larger one is nearly complete and preserved with the abactinal face up, while the smaller one preserves only part of one arm and is preserved with the actinal face up. These fossils were initially held in the private collection of Nicolas Tourment in Marseille and are now housed in the Natural History Museum of Geneva, Switzerland, under specimen number MHNG-GEPI-87379. In 2026, Anaïs Travers and colleagues described Cruciformaster pedicellarius as a new genus and species based on these remains, designating the larger individual as the holotype and the smaller as a paratype. The generic name references the distinctly cruciform shape of the superomarginal plates, combined with the Latin aster meaning 'star'. The specific name pedicellarius alludes to the notched actinal and adambulacral ossicles corresponding to insertions for pedicellariae. Cruciformaster has a broad, pentagonal central disc and five short, tapered arms with rounded interbrachial areas. The holotype has a large radius of 9 cm and a small radius of 4 cm.

Reader's Guide

Cruciformaster is significant as the first fossil member of the family Oreasteridae to be described, and it is part of a unique fossil assemblage from the Calcaire de Ménerbes Formation, dated to about 16 million years ago. This assemblage includes three other sea stars—Lacosteaster lauerorum (Solasteridae), an unnamed species of Astropecten (Astropectinidae), and Menerbesaster bongrainae (Echinasteridae)—each from a different family, representing the first described diverse Miocene sea star fauna in Western Europe. The preservation is exceptional: ossicles are almost always in anatomical position, and the flattened preservation style contrasts with the folded preservation typical of sea stars that escape slow burial. The co-occurrence of these four families, whose modern members inhabit different environments (oreasterids in warm, shallow waters; solasterids in shallow to upper bathyal; astropectinids in cold to tropical waters; echinasterids in various habitats) and have different lifestyles (epibenthic vs. endobenthic), suggests they were transported by a natural event and rapidly buried. The deposit is interpreted as a sudden, massive mortality event, possibly from episodic storms. Modern analogs suggest Cruciformaster may have preyed on the sea urchin Tripneustes planus, similar to modern Oreaster reticulatus preying on Tripneustes ventricosus.

Did You Know?

• Cruciformaster is the first—and only, at the time of its description—fossil member of the family Oreasteridae to be described.
• The two known individuals are preserved together on a single limestone slab, with the larger one showing the abactinal face and the smaller only part of one arm showing the actinal face.
• The generic name Cruciformaster references the cruciform shape of the superomarginal plates, unlike the rectangular shape in other oreasterids.
• The fossil assemblage includes four sea stars from different families, representing the first described diverse Miocene sea star fauna in Western Europe.