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Iberospinus (meaning "Iberian spine") is an extinct genus of Spinosauridae dinosaur from the Early Cretaceous (Barremian) Papo Seco Formation of Portugal. The genus contains a single species, I. natarioi, known from several assorted bones belonging to one individual. Iberospinus represents one of five known spinosaurid taxa from the Iberian Peninsula, the others being Camarillasaurus, Protathlitis, Riojavenatrix, and Vallibonavenatrix. It is important for its implications of the geographical origin of Spinosauridae and the suggested presence of potentially semi-aquatic lifestyle earlier in the evolution of this clade.
Iberospinus is currently known from Mandible fragments, Tooth, an incomplete right scapula, partial dorsal and Vertebra vertebrae, rib fragments , a partial pubis, two incomplete Calcaneus, and a pedal ungual Phalanx bone . All of the material belongs to one individual. The holotype material, despite being highly fragmentary, represents one of the more complete spinosaurid specimens known.
Of the generic name, " Iberospinus," "ibero" is derived from Iberia, a Roman name for the Iberian Peninsula, while the Latin spinus means spine, after the elongated neural spines of related Spinosauridae. The specific name, " natarioi" honors Carlos Natário, the discoverer of the holotype.
The following Autapomorphy distinguish Iberospinus. The dentary bone contains a single foramen within the Meckelian groove and has a straight ventral edge instead of curved as in most other spinosaurids. Laminae are present in the pleurocoelic depression of the mediodistal tail vertebrae. The scapula has a straight anterior rim without a protruding acromion and a coracoidal contact occupying the entire ventral surface. The pubic apron is thick throughout the entire length of the pubic shaft. There is a mound-like eminence in the proximal lateral portion of the pubic bone.
In their description of Mateus & Estraviz-López (2022) recovered Iberospinus within the Spinosauridae, outside of both the Baryonychinae and the Spinosaurinae, similar to the results of Arden et al. (2019). However, they explain that the fossil material shows some characteristics of baryonychines, suggesting a closer relation to the group. A cladogram after the describing authors is shown below:
In their 2023 description of Protathlitis, Santos-Cubedo et al. performed a phylogenetic analysis, recovering a taxonomic split between the Baryonychinae and Spinosaurinae, similar to the previous results of Mateus & Estraviz-López (2022). Although Iberospinus was not included in their analysis, they proposed that, due to similarities in anatomy, likely phylogenetic position, and age, Iberospinus may be either the sister taxon to Camarillasaurus, or possibly synonymous with it. In their 2025 reassessment of Camarillasaurus, Rauhut and colleagues recovered Iberospinus as the basalmost member of the Spinosaurinae, with Camarillasaurus as a later-diverging taxon, precluding their synonymization.
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