Ocepechelon bouyai

Reconstruction of Ocepechelon bouyai（圖片來源：Bardet N et al. (2013)，採用 CC BY 2.5 授權）

Age

Cretaceous（Maastrichtian）

~67 Ma

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Taxonomy

Kingdom: Animalia

Phylum: Chordata

Class: Sauropsida

Order: Testudines

Suborder: Cryptodira

Family: Protostegidae

Genus: Ocepechelon

Species: Ocepechelon bouyai

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Morphological description

The fossil of the narrow-snouted phosphate turtle Ocepechelon bouyai is based on a gigantic skull. The skull measures roughly 70 cm in length and about 43 cm in width, making it one of the most impressive sea turtle skulls known. The skull is overall flattened and elongated, and its most striking feature is a suction-feeding snout formed by multiple dermal bones, narrowing anteriorly into a small tubular opening. This structure represents a highly specialized suction apparatus.

The premaxillae are fused into a planar surface and connect with maxillae that curve ventrolaterally. At the posterolateral part of the skull roof, the squamosals extend outward, giving the posterior portion of the skull a broad, flaring appearance. The external nares are positioned near the top of the skull, between the anterior margins of the orbits, and the nasal cavity is markedly flattened.

Along the inner margin of the upper jaw, traces of the keratinous beak sheath (rhamphotheca) are preserved. Its lower edge forms a narrow and thin surface that resembles a structure for controlling water flow rather than for biting, crushing, or cutting prey. The orbits are large and directed anterolaterally, and they overlap with the inferior temporal fossa.

Skull of Ocepechelon bouyai（圖片來源：Bardet N et al. (2013)，採用 CC BY 2.5 授權）

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Etymology

Genus name Ocepechelon: “OCP” derives from the abbreviation of the Moroccan phosphate company Office Chérifien des Phosphates, while “chelon” comes from the ancient Greek χελώνη, meaning “turtle.” The name honors the institution that supported fossil collection and research.

Species name bouyai: named in honor of Baâdi Bouya, the geological survey director of the Office Chérifien des Phosphates at Khouribga, Morocco, who provided important support to the research team during fieldwork.

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Biological description

The skull morphology suggests that Ocepechelon bouyai was a turtle inhabiting large open marine environments during the Late Cretaceous. Its limbs likely evolved into flippers suited for swimming. The flattened skull, together with eyes and external nares positioned near the top of the head, indicates that the animal probably spent much of its time near the sea surface, similar to the posture adopted by some living crocodilians when cruising at the water surface. Stratigraphic context and associated marine vertebrate fossils further support an offshore marine habitat.

Its most remarkable ecological adaptation lies in its straw-like snout. The tubular, extremely narrow anterior opening lacks any structure capable of cutting or grinding food, making it unlikely that prey was obtained through biting. Instead, the turtle likely captured small swimming prey by generating rapid inflows of water through the narrow opening, a feeding strategy comparable to that of modern seahorses.

Estimates suggest that the diameter of the snout opening was about 6 cm. This implies a diet primarily composed of small fish, squid, or soft-bodied organisms such as jellyfish. Because suction feeding requires rapid expansion of the buccopharyngeal cavity, the broad posterolateral expansions of the pterygoids and squamosals would have provided large attachment areas for muscles, indicating powerful hyoid and pharyngeal musculature capable of quickly generating negative pressure.

As in many modern turtles, the esophagus may have possessed considerable extensibility, allowing it to function as a temporary water reservoir during suction and swallowing, thereby facilitating prey capture and the expulsion of excess water. The buccopharyngeal cavity may also have contained keratinous papillae that helped retain prey during suction feeding.

(Author: Shui-Ye You)

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Reference

Bardet N et al. (2013). A Giant Chelonioid Turtle from the Late Cretaceous of Morocco with a Suction Feeding Apparatus Unique among Tetrapods. PLOS ONE.

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