Horseshoe Crab Fossils Dating 465 Million Years Found In AlUla By Royal Commission

The Royal Commission for AlUla has reported an internationally documented discovery of rare horseshoe crab fossils in AlGharameel Nature Reserve, dating back about 465 million years. The find, now published in a peer-reviewed study, provides new evidence about ancient marine life and strengthens AlUla’s role as a centre for geological and scientific research.

The research appears in Gondwana Research, an international journal focused on geological sciences. Publication in this journal confirms the scientific importance of the AlUla horseshoe crab fossils and places the discovery within global academic discussions on Earth’s history, palaeontology, and biodiversity, with specific reference to the Arabian Peninsula’s ancient environments.

According to the study, the horseshoe crab fossils come from the Middle Ordovician period, dated between approximately 485 and 444 million years ago. This timeframe makes the specimens among the oldest known horseshoe crab fossils worldwide. Researchers report that these AlUla fossils are unusually large compared with other examples from the same geological period.

All of the AlUla horseshoe crab fossils were found preserved upside down, a mode of preservation not previously recorded for such organisms. Nearby trace fossils appear to show attempts by the animals to right themselves. This combination offers rare evidence of ancient behavioural patterns and allows comparison with the behaviour of horseshoe crabs observed in modern coastal environments.

Geological stratigraphic analysis from the site points to repeated strong seasonal storms during the Middle Ordovician. The study suggests that the AlUla horseshoe crab fossils represent groups that gathered in shallow coastal waters affected by these storms. Sediment from such events likely buried the organisms, helping preserve detailed body structures and movement traces.

The newly described material from AlGharameel Nature Reserve represents a previously unclassified species of horseshoe crab. Researchers are studying the AlUla horseshoe crab fossils in two phases with an international team led by Dr. Russell Bicknell, an academic at Flinders University in Adelaide, to establish their formal position within existing scientific classifications.

The first research phase has documented the main features of the new species and its geological setting. A second phase is planned for the first half of 2026, when additional fossil samples will be collected from AlGharameel. These further investigations aim to complete the description of the new species and clarify its evolutionary relationships.

The study states that the AlUla horseshoe crab fossils provide a clearer picture of the area’s ancient shoreline, helping reconstruct the geological and environmental history of AlUla. The Royal Commission for AlUla views the findings as supporting accurate data collection, innovation in natural heritage research, and the development of scientific and educational programmes focused on the region.

The fossil specimens are now preserved within the Royal Commission for AlUla’s museum collections, where they will support future scientific work and public engagement. The commission notes that the discovery contributes to AlUla’s profile as a destination for geological research and international collaboration, while the full scientific study is available through Gondwana Research for specialist readers.

With inputs from SPA