Iberospinus
| Iberospinus | |
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| Skeletal diagram of the related Baryonyx, showing the known bones of Iberospinus in red (Scott Hartman) | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Spinosauridae |
| Genus: | †Iberospinus Mateus & Estraviz-López, 2022 |
| Species: | †I. natarioi
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| Binomial name | |
| †Iberospinus natarioi Mateus & Estraviz-López, 2022
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Iberospinus IPA: [aɪbiːʌroʊs̠piːnʊs̠] or IPA: [aɪbiːʌroʊs̠paɪnʌs̠] (meaning "Iberian spine") is an extinct genus of spinosaurid 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.[1] It is important for its implications of the geographical origin of Spinosauridae and the suggested presence of an at least semi-aquatic lifestyle early in the evolution of this clade.[2]
Discovery and naming
The first fossil material was discovered in 1999, with additional expeditions from 2004 to 2008. After being described as a specimen of Baryonyx in 2011,[3] it was realised to have been a unique species in 2019, with specimen ML1190 as the holotype.[4] Additional material was discovered in a June 2020 expedition, after which Iberospinus was described as a new genus and species in 2022 by Octávio Mateus and Darío Estraviz-López.[2]
Iberospinus is currently known from dentary fragments, teeth, an incomplete right scapula, partial dorsal and caudal vertebrae, rib fragments, a partial pubis, two incomplete calcanea, and a pedal ungual phalanx. All of the material belongs to one individual. The holotype material represents one of the most complete spinosaurid specimens in the world.[2]
Of the generic name, "Iberospinus," "ibero," IPA: [aɪbiːʌroʊs̠] is derived from Iberia, a Roman name for the Iberian Peninsula, while the Latin "spinus," IPA: [s̠piːnʊs̠] or IPA: [s̠paɪnʌs̠] means spine, after the elongated neural spines of related spinosaurids. The specific name, "natarioi, IPA: [nɑtʰɑːɽiːoʊiː] " honors Carlos Natário, the discoverer of the holotype.[2]
Description
The dentary (lower jaw) of Iberospinus shows an intricate neurovascular system that would connect the teeth and the external foramina. A series of replacement teeth are also preserved in the dentary. Characteristics of the bones, especially in the tail and pedal ungual phalanx, indicate a possible semi-aquatic lifestyle, though the extreme features in some related spinosaurines are not seen.[2]
The following
Classification
The Iberospinus fossil material was included in
| Spinosauridae |
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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:[2]
| Spinosauridae |
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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.[6]
Paleobiology
A 2017 histological study of
Palaeoenvironment
The Papo Seco Formation of Portugal where Iberospinus is known from is composed of marl, representing a lagoon environment. Other dinosaur remains from the area include fragments tentatively assigned to Mantellisaurus, a macronarian sauropod, and Megalosaurus. Most of the bones of Iberospinus specimen ML1190 were damaged, and some scratches may be marks from small scavengers. The specimen's disarticulation indicates it was transported from a more-terrestrial environment (since many bones are missing), but those found were close together.[8][9]