Marine subsidization is a well-documented process on modern coastlines. Marine algae, seagrasses, and other coastal plants produce organic matter that washes ashore or is carried inland by tides, storms, and scavenging animals, enriching terrestrial soils and feeding land-based consumers. Ecologists have long recognized this cross-boundary nutrient transfer in contemporary settings, from seabird colonies fertilizing islands to kelp forests sustaining coastal forests. Yet, according to the authors, this phenomenon has rarely been considered in reconstructions of Cretaceous terrestrial coastal ecosystems, despite the fact that many of the most famous dinosaur-bearing rock formations in North America were deposited along the margins of the Western Interior Seaway, a vast inland sea that split the continent.

The research team focused on a geochemical signature that had puzzled paleontologists for years. Studies of Cretaceous coastal ecosystems frequently reported anomalously high carbon isotope values, expressed as δ13C, in the bioapatite of dinosaurs and other vertebrates, values much higher than expected when compared to the presumed dietary carbon sources of these animals. In terrestrial C3 plant communities, which dominated Cretaceous floras, δ13C values are relatively low. Marine plants and macroalgae, however, use a modified C3 photosynthetic pathway that results in comparatively enriched δ13C values. Any animal consuming marine-derived plant material or prey that had themselves fed on such resources should therefore carry a distinctive isotopic fingerprint in its tissues.

To test whether Cretaceous coastal vertebrates were actually tapping into marine food sources, the researchers analyzed stable carbon isotopes preserved in tooth enamel from a range of vertebrate taxa, including fish, neosuchian crocodilians, and dinosaurs. Tooth enamel is remarkably resistant to chemical alteration over geological time, making it one of the most reliable archives of an animal’s dietary carbon signature. The team compared enamel from coastal assemblages against enamel from the Cloverly Formation of Wyoming and Montana, an inland intercontinental deposit where marine influence was expected to be minimal based on established stratigraphic interpretations.

The coastal formations examined span a broad geographic and temporal range across western North America. They include the Dunvegan Formation of British Columbia and Alberta in Canada, the Wayan Formation and Draney Limestone of Idaho, the Antlers Formation of Oklahoma and Texas, the Woodbine Group and Lewisville Formation of Texas, and the Mussentuchit Member of the Cedar Mountain Formation in Utah. Together, these units represent diverse coastal environments that existed at various points during the Cretaceous period, from estuarine and deltaic settings to nearshore floodplains.

The results were striking. Coastal vertebrate enamel exhibited δ13C values up to more than 5.5 per mil above what would be expected from animals feeding exclusively on terrestrial C3 vegetation. This enrichment is consistent with the incorporation of marine-derived carbon into the diets of coastal organisms. In contrast, the upland assemblages from the Cloverly Formation showed no comparable enrichment, supporting the interpretation that the elevated isotope values in coastal settings reflect genuine marine subsidization rather than some artifact of preservation, diagenesis, or analytical methodology.

The implications of this finding extend beyond simply confirming that some dinosaurs ate things that came from the sea. Back-calculations of dietary plant δ13C values from dinosaur herbivore enamel have traditionally relied on assumptions about the isotopic composition of terrestrial C3 plants. If coastal herbivores were consuming marine algae, seagrasses, or animals that had fed on such resources, then previous estimates of dietary plant δ13C values systematically underestimated the true range of carbon sources available to these animals. Future estimations of Cretaceous vertebrate isotopic offsets must therefore account for the influx of 13C-enriched, marine-derived organic matter into terrestrial food webs.

Beyond the technical implications for isotope ecology, the study suggests that marine subsidization may have functioned as a major ecosystem and trophic driver in Cretaceous coastal environments. If substantial quantities of marine nutrients and energy were regularly flowing onto land, they could have supported higher densities of vertebrate consumers than terrestrial primary production alone would allow. This could help explain the remarkable abundance and diversity of large-bodied dinosaurs and other vertebrates in coastal depositional settings, which have sometimes been attributed solely to favorable terrestrial conditions or preservational biases.

The research also highlights the value of comparative approaches that pair coastal and inland deposits. By establishing that the Cloverly Formation, an inland deposit, lacks the isotopic enrichment seen in coastal assemblages, the study provides a baseline against which marine influence can be detected. This framework can now be applied to other Cretaceous formations around the world, potentially revealing the geographic extent and temporal variability of marine subsidization during the age of dinosaurs.

As paleontologists continue to reconstruct ancient ecosystems with ever-greater precision, the recognition that ocean and land were deeply intertwined during the Cretaceous adds a new dimension to our understanding of dinosaur ecology. The giants that roamed the shorelines of the Western Interior Seaway were not simply inhabitants of a terrestrial world; they were participants in a dynamic system where marine and terrestrial energy flows converged, shaping the structure and productivity of ecosystems in ways that scientists are only now beginning to appreciate.

Subject of Research: Marine-derived nutrient subsidies in Cretaceous coastal dinosaur ecosystems revealed by stable carbon isotope analysis of tooth enamel

Article Title: Marine subsidization of dinosaurian ecosystems

Article References: Forster, C. W., Suarez, C. A., Cullen, T. M., Zanno, L. E., & Hyland, E. G. (2026). Marine subsidization of dinosaurian ecosystems. Frontiers in Ecology and Evolution, 14, Article 1895247. https://doi.org/10.3389/fevo.2026.1895247

Image Credits: AI Generated

DOI: 10.3389/fevo.2026.1895247

Keywords: marine subsidization, Cretaceous, dinosaurs, stable carbon isotopes, tooth enamel, Western Interior Seaway, paleoecology, coastal ecosystems, δ13C, food webs, Frontiers in Ecology and Evolution, vertebrate paleontology

The fossil material was unearthed at the La Tejería site in El Castellar, in the province of Teruel, an region that has become one of Europe’s most productive windows into Mesozoic life. Over the course of careful excavation, the team recovered fourteen exceptionally preserved caudal vertebrae, the bones of the dinosaur’s tail, along with several chevron bones, the small paired elements that hang beneath the tail vertebrae and help protect blood vessels and support musculature. Although skull material and limb bones were not part of the recovered assemblage, the quality and diagnostic character of the tail bones proved sufficient for the researchers to make a confident identification at the genus level, something rarely achievable with fragmentary sauropod remains.

Sergio Sánchez Fenollosa, a PhD student in biodiversity and evolutionary biology at Fundación Dinópolis and lead author of the study, described the slow accumulation of evidence that led the team to their conclusion. From the earliest stages of the osteological study, he explained, the researchers noticed strong similarities between the Spanish bones and several diplodocine sauropods. As the anatomical work progressed, they began to identify a combination of features characteristic of Diplodocus species, and subsequent evolutionary analyses repeatedly pointed in the same direction. With each new result, he said, the picture became clearer: the team was looking at a Diplodocus. He added that the outcome of the dig represents some of the strongest palaeontological evidence yet found for episodes of dispersal and faunal exchange between North America and Europe across the proto-Atlantic Ocean during the Late Jurassic, and that the discovery allows a better understanding of Iberian Mesozoic ecosystems and the diversity of sauropod dinosaurs that inhabited the European Jurassic.

The identification rested on a suite of distinctive anatomical features preserved in the vertebrae and chevrons. The tail bones display large pneumatic cavities, air-filled spaces that lightened the skeleton in these colossal animals, a hallmark of many sauropod lineages but expressed in a particularly characteristic form in Diplodocus. The underside of the tail vertebrae bears deep longitudinal grooves, and the chevron bones are distinctly forked, with unique medial fossae, depressions on their inner surfaces, that match the condition seen in North American Diplodocus material. The vertebral centra, the main cylindrical bodies of the vertebrae, are elongated and lack the lateral ridges found in many related diplodocids. Taken together, this combination of traits distinguished the Spanish specimen from other European diplodocids and aligned it with the Diplodocus lineage.

To test the anatomical assessment rigorously, the research team combined traditional comparative anatomy with advanced phylogenetic analyses, employing both maximum parsimony and Bayesian inference methods. These computational approaches evaluate how anatomical characters are distributed across known taxa to reconstruct evolutionary relationships. In both analytical frameworks, the Spanish specimen was confidently placed within the genus Diplodocus, and more specifically as a close relative of Diplodocus hallorum, one of the largest and longest species within the genus. The convergence of anatomical and statistical evidence is what gives the identification its strength, since isolated tail vertebrae can be notoriously difficult to assign to a precise genus among the many similar diplodocid sauropods known from the Late Jurassic.

The Spanish Diplodocus dates to approximately 150 million years ago, near the end of the Jurassic Period, a time that corresponds closely with the age of the Morrison Formation faunas in North America. Its presence in Europe provides compelling evidence that dinosaurs could migrate between the two landmasses during the Late Jurassic. The most likely mechanism, according to the researchers, involved temporary land bridges that emerged as the proto-North Atlantic Ocean underwent regressive phases, periods in which sea levels fell and exposed connections between now-separated continental areas. Such episodic corridors would have allowed herds of giant herbivores, and presumably the predators and smaller animals that followed them, to move between North America and Europe, explaining how a genus once thought to be endemic to the American West could appear on the Iberian Peninsula.

Co-author Dr Alberto Cobos, managing director of Fundación Dinópolis, emphasized the sheer scale of the animal. The Diplodocus from El Castellar was approximately 25 meters long, comparable in size to its North American relatives, making it another of the giant sauropods of the Spanish Jurassic. He noted that it joins other enormous sauropod dinosaurs from Teruel with very different characteristics from those of diplodocids, such as Turiasaurus and Losillasaurus, among others. The fossils of all these dinosaurs, including those of the new Diplodocus specimen, he said, make Teruel a reference place for understanding this great diversity. The coexistence of a diplodocid giant alongside turiasaurian sauropods of entirely different build suggests that Late Jurassic Iberian ecosystems supported multiple niches for gigantic herbivores, perhaps with the different lineages specializing in different vegetation or feeding heights.

The broader fossil record of the region reinforces that picture of ecological richness. The area where the specimen was found has yielded numerous dinosaur fossils representing sauropods, theropods, stegosaurs, and ornithopods, indicating that these ancient coastal environments supported complex and diverse ecosystems. During the Late Jurassic, eastern Iberia lay along the margins of the expanding Atlantic, with shallow seas, coastal plains, and floodplains that periodically preserved the remains of the animals that roamed them. The addition of Diplodocus to this faunal list strengthens the resemblance between Iberian and North American Late Jurassic assemblages, supporting the idea of a broadly shared dinosaur fauna across the two regions rather than isolated provincial communities.

Diplodocus itself occupies a special place in the history of palaeontology and popular culture. First discovered in the United States in 1878, the genus is famous for its enormous length of up to 25 meters, its long whip-like tail, and its relatively small head perched at the end of a gracefully curved neck. Throughout the early twentieth century, casts of Diplodocus skeletons were displayed in leading natural history museums around the world, making the animal a symbol of global palaeontology and a beloved icon of prehistoric life. Its frequent appearances in exhibitions, books, and audiovisual productions about dinosaurs have made it one of the best-known of all the so-called terrible lizards among the general public, which is precisely why the confirmation of its presence in Europe carries such resonance both scientifically and culturally.

The fossils themselves are now on display for future research and public education in the dinosaur hall of the Museo Aragonés de Paleontología at Dinópolis in Teruel, a city in eastern Spain situated roughly between Madrid and Valencia. There, visitors can see the tangible evidence of an animal that lived 150 million years ago on a planet whose geography differed profoundly from today’s, when the Atlantic was still young and narrow and continents remained within reach of wandering giants. For palaeontologists, the specimen opens new questions about how many other supposedly North American dinosaur lineages may await discovery in European rocks, and about the frequency and duration of the dispersal events that connected the faunas of two continents. For the moment, the tail bones from La Tejería stand as the first physical proof that Diplodocus, the archetypal giant of the American Jurassic, also called Europe home.

Subject of Research: First discovery of the sauropod dinosaur genus Diplodocus outside North America, from Late Jurassic deposits in Teruel, Spain

Article Title: First ever find of a Diplodocus outside of North America

Article References: First ever find of a Diplodocus outside of North America. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Diplodocus, sauropod, Late Jurassic, Teruel, Spain, paleontology, Morrison Formation, faunal dispersal, proto-Atlantic, vertebrate paleontology, dinosaurs, Iberia