Reconstrucción de la red neurovascular del maxilar de <i>Iguanodon</i> en las X Jornadas Internacionales de Salas de los Infantes

En las pasadas X Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno 2025, se presentó la primera reconstrucción de la red neurovascular de la maxila de Iguanodon bernissartensis realizada mediante técnicas 3D. La morfología de la rama maxilar del nervio trigémino es muy poco conocida entre los dinosaurios no avianos. En I. bernissartensis, el canal principal es grande y los secundarios que conducen a los forámenes maxilares forman un ángulo obtuso con el canal principal. Esta morfología difiere con la presente en terópodos o saurópodos indicando que la rama maxilar es muy variable entre los dinosaurios no avianos. Además, también se encontraron diferencias en la organización de la segunda fila dorsal de canales secundarios entre I. bernissartensis y otros ornitópodos más basales debidas a la elongación de la maxila. El resumen es el siguiente:

The study of dinosaur neuroanatomy is a growing field. This field is mostly dominated by the study of the cavities of the central nervous system on the braincase. However, the increasing study of the neurovascular cavities on the rostral bones in recent years is allowing a more thorough reconstruction of the neurovascular system.
The trigeminal nerve is the primary somatosensory nerve that can be identified in the rostral bones. It stems from the forebrain and then divides into three main rostral divisions: the ophthalmic division (V1), the maxillary division (V2), and the mandibular division (V3). These branches with their corresponding arteries and veins run through bony canals in the nasal (V1), the maxilla (V2) and the dentary (v3). Its knowledge in Ornithopoda however, is so far limited to an indeterminate Dryosaurid, the elasmarian Galleonosaurus, the non hadrosaurid Styracosterna Fukuisaurus and the hadrosaurid Edmontosaurus. We explore this neurovascular network in the maxillae of the non hadrosaurid Styracosterna Iguanodon bernissartensis.
Two right maxillae (CMP11.1 and CMP11.2) retrieved from the upper Barremian “Arcillas de Morella” Formation at Morella (Castellón, Spain) were referred to the large-sized European ornithopod Iguanodon bernissartensis. To evaluate potential differences between these specimens and other dinosaurs, the maxillae were scanned using computed axial tomography (CT-scan).
The maxillary canal of the best preserved CMP11.1 has a relatively large diameter and runs longitudinally through the maxilla dorsal and labial to the roots of the teeth. This main canal branches into secondary canals that exit the maxilla through two rows of foramina in the lateral surface. The secondary canals that exit through the ventral row of seven foramina form an obtuse angle with the posterior part of main maxillary canal. The second row of four foramina emerge lateral to the main canal with a close to 90 degree angle in dorsal or ventral view. Finally, the main canal exits through the anterior maxillary foramen without branching.
Preservation of the second maxilla CMP11.2 is not as good as CMP11.1 but it also shows the same structure: a large main maxillary canal and some ventral and lateral rows of foramina. A comparison with the trigeminal V2 branch from a braincase of a different individual also referrable to I. bernissartensis shows a diameter very close to that of the posterior foramen in both maxillae, suggesting no drastic changes in the diameter of V2.
The maxillary canal has been described only in a handful of non-avian dinosaurs, especially in theropods. But among the clade Ornithopoda this structure has only described before in Galleonosaurus dorisae a basal elasmarian ornithopod from the Barremian of Australia (Wonthaggi Formation).
Both Iguanodon and Galleonosaurus share an obtuse angle of the secondary canals with the posterior portion of the main canal, however these secondary canals are noticeably longer in Iguanodon. Also, the number and distribution of the external foramina differ; in Galleonosaurus there is one predominant ventral row of foramina but in the anterior part of the maxilla the canal divides into multiple branches anterior to the antorbital fenestra. In Iguanodon the dorsal row of foramina is distributed in the anterior half of the bone, however in both taxa these dorsal foramina are located anterior to the ascending process of the maxilla. This suggests that the more spaced distribution in Iguanodon might be a product of the elongation of the anterior portion of the maxilla.
The dorsal alveolar canals in ornithopods are large and the secondary canals show a characteristic obtuse angulation which differs with the branching of these canals in other non-avian dinosaurs. The differences in the organization of the second dorsal row of secondary canals among ornithopods particularly the density, number of rows and position might be a product of the elongation of the preorbital region in Iguanodontia, absent in earlier branching ornithopods.