The specimen itself is modest in appearance. When collector J. L. Goedert found the concretion fragment at extreme low tide in April 2025, the fish remains were slightly etched by natural weathering and protruding from two sides of the rock. Scales and bones were closely packed around three vertebrae that were still in apparent articulation, and careful preparation revealed a single otolith, the ear stone that fishes use for balance and hearing. All of the remains are assumed to come from one individual fish, now registered as the holotype specimen UWBMVP 128914 at the University of Washington’s Burke Museum in Seattle. The species is named for Michael A. Rich of the Burke Museum, who has produced numerous research photographs for the paleontology team there, including the images of the new species.

What makes the find remarkable is where it came from. The Makah Formation, the rock unit that yielded the concretion, was deposited in a deep-marine basin-plain environment well offshore during the early Oligocene. The formation is dominated by turbidites, thick sections of structureless mudstone and siltstone, and alignments of calcareous concretions that help define the bedding. Within those concretions, researchers have found glendonites, minerals that indicate bottom water temperatures near freezing. Fossils of any kind are rare in this part of the Makah Formation, but the preserved biota includes mollusks, sea pen axes, whales, wood falls, and distinct invertebrate communities that lived at cold hydrocarbon seeps. The only fish previously mentioned from this interval was a bone fragment and some scales of an indeterminate aulopiform, protacanthopterygian or scombroid, making the new grenadier a significant addition to the deep-water record.

Preparation of the fossil required patience and precision. The specimen was etched with dilute formic acid at roughly five percent concentration, and final cleaning was done in an ultrasonic bath for fifteen minutes. Because the bones, scales and otolith had been replaced by silica, they survived the acid treatment while the surrounding carbonate dissolved away. Individual scales were photographed with a Canon EOS 5DS digital camera and a 65 mm macro lens mounted on a vertical carriage, with custom-built software controlling the camera’s movement to allow precision focusing. For some scales, up to fourteen images were stacked to produce sharp composite photographs. Comparative scales from modern grenadiers held in the ichthyological collection of the Zoological Museum Hamburg were stained with Alizarin Red to make their characters easier to see, and the images were stacked using the software Helicon Focus.

The otolith proved to be the key to identifying the fish. At 14.5 millimeters in length, it is large, with an overall oval shape and a length-to-height ratio of 1.4. Its dorsal rim is low and broadly undulating, with a depression near the middle and a rounded postdorsal high, while the ventral rim is regularly curved and deepest in front of its middle. The inner face carries a wide sulcus, the groove that houses the sensory epithelium of the inner ear, positioned supramedian and containing two large, nearly equally sized, closely spaced colliculi. The absence of a pseudocolliculum in the narrow collum, together with the otolith’s robust proportions, marks the specimen as belonging to Coryphaenoides, the second most species-rich genus of the Macrouridae after Coelorinchus. The closest living analogues include Coryphaenoides carminifer from the tropical East Pacific, C. marshalli from off southern West Africa, C. rupestris from off Norway, and C. woodmasoni from the Laccadive Sea, though the fossil differs from all of them in details such as a more pointed anterior tip and the position of the deepest point of the ventral rim.

The scales are equally distinctive. They are of the cycloid-spinoid type, circular to polygonal in shape, with distinct continuous circuli and no radii or reticulate structure. Their most striking feature is the armament of spines: robust, moderately long to long, angled at 80 to 90 degrees relative to the scale surface, and, unusually, not arranged in rows. In typical body scales from the flanks, the longest spines reach one third to one half of the scale length, and in some smaller peripheral scales, which may have come from the head region or fin bases, the spines actually exceed the scale length. The authors compared the fossil scales with material from modern species including C. rudis, C. alateralis, C. subserrulatus and C. armatus, and found that the combination of characters in C. richi differs from all macrourid scales, fossil or extant, described so far. The spines are stronger than in species such as C. asper or C. guentheri, lack the broad bases seen in C. subserrulatus and many Coelorinchus species, have a single tip rather than the tridentate tips of C. marshalli, and are more densely set than in most species of the genus.

The unordered spine pattern is perhaps the most intriguing character of all. In most macrourid taxa, scale spines are arranged in parallel, sub-parallel or radial rows, sometimes with an enlarged middle row. A similar unordered pattern does occur in the modern C. rudis, but there the spines lie relatively flat in lateral view, whereas in C. richi they point straight away from the scale plane. Whether this arrangement represents a specific adaptation or a primitive condition is difficult to determine. Morphology-based phylogenies suggest that the primitive scale pattern in Coryphaenoides already showed spines ordered in rows, which would make the fossil’s pattern a derived feature. But more recent molecular phylogenetic studies do not yet include enough species of the highly diverse grenadier assemblage to allow a reliable reconstruction of the evolution of scale patterns in the family.

The authors also use the discovery to sound a note of caution about how fossil grenadiers are classified. Multiple fossil macrourid species and genera were described in 1956 based on isolated scales from Pacific Coast rocks of the United States ranging in age from Paleocene to Pliocene, but macrourid scale characters show a high degree of convergent evolution, meaning that very similar features can appear in only distantly related taxa. Several of those older taxa, particularly at the genus level, must be considered doubtful because of the limited comparative material used. Even though the scales of C. richi are highly characteristic, the researchers recommend that fossil macrourid taxa should not be described on the basis of isolated scales alone; it was the combination of otolith and scales that allowed a confident identification here.

The broader significance of the find lies in what it says about the history of the deep sea. The Eocene-Oligocene Transition, around 34 million years ago, was a pivotal interval in which deep-ocean circulation shifted from a halothermal system to a thermohaline one. This change brought well-oxygenated but cold water into the deep ocean and triggered, or accelerated, the depth migration of certain fish groups that are now iconic inhabitants of the deep, including the Macrouridae and many Ophidiiformes, which had mostly inhabited shallow seas during the preceding warm-house period. The earliest fossil macrourids are known from middle to lower shelf environments of Paleocene Denmark and Australia, and during the Eocene warm-house their otoliths are found commonly in shallow-water deposits of Antarctica. As cooling set in during the middle to late Eocene, macrourids began venturing into bathyal realms, and depth segregation of macrourid speciation has been observed in the late Eocene and Oligocene fossil record of New Zealand.

Against that backdrop, Coryphaenoides richi from the lower Oligocene deep-water rocks of the Makah Formation confirms that the family was by then firmly established in bathyal environments of the northeast Pacific, and that one particular lineage within the genus Coryphaenoides was already evident. Earlier Oligocene records of Coryphaenoides otoliths are few and require revision, as some may represent extinct macrourid genera instead, and no records of the genus are known from Eocene strata, even though the earliest macrourids date back to the Paleocene. Today, species of Coryphaenoides are characteristic demersal fishes at bathyal and abyssal depths and rank among the deepest-living teleosts known. A fish that began diversifying as the deep ocean cooled and oxygenated now thrives in some of the most extreme habitats on Earth, and the tiny concretion from a Washington beach preserves a snapshot of that transformation in progress.

Subject of Research: A new Oligocene deep-sea grenadier fish species from Washington State illuminating the early evolution of macrourid fishes

Article Title: Coryphaenoides richi sp. nov. ( Macrouridae , Teleostei ) from the deep-marine, Oligocene Makah Formation of Washington State, U.S.A.

Article References: Schwarzhans, W. W., Moritz, T., & Goedert, J. L. (2026). Coryphaenoides richi sp. nov. (Macrouridae, Teleostei) from the deep-marine, Oligocene Makah Formation of Washington State, U.S.A.. Zitteliana, 100, 31-38. https://doi.org/10.3897/zitteliana.100.182311

Image Credits: AI Generated

DOI: 10.3897/zitteliana.100.182311

Keywords: Coryphaenoides richi, Macrouridae, grenadier fish, Oligocene, Makah Formation, deep sea, paleontology, otolith, fossil fish, Eocene-Oligocene Transition, Washington State, marine paleontology