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Iberospinus

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Iberospinus
Temporal range: Early Cretaceous (Barremian),
129.4–125 Ma
↓
Skeletal diagram of the related Baryonyx, showing the known bones of Iberospinus in red (Scott Hartman)
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: †Spinosauridae
Genus: †Iberospinus
Mateus & Estraviz-López, 2022
Species:
†I. natarioi
Binomial name
†Iberospinus natarioi
Mateus & Estraviz-López, 2022

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 four known spinosaurid taxa from the Iberian Peninsula, the others being Baryonyx, Vallibonavenatrix, and Camarillasaurus. 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.[1]

Discovery and naming

Life reconstruction of Iberospinus showing a 3D digitalization of some of the recovered bones, as well as reconstructed musculature

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,[2] it was realised to have been a unique species in 2019.[3] 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.[1]

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.[1]

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.[1]

Description

CT scan of the holotype dentary, showing teeth (blue), replacement teeth (green and pink), and neurovascular system (yellow)

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.[1]

The shoulder blade

The following autapomorphies distinguish Iberospinus. The dentary bone contains a single foramen within the Meckelian sulcus 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 shoulder blade 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.[1]

Classification

Iberospinus was recovered within the Spinosauridae, outside of both the Baryonychinae and the Spinosaurinae. However, Mateus & Estraviz-López (2022) explain that the fossil material shows some characteristics of baryonichines, suggesting a closer relation to the group. An adjusted cladogram after the describing authors is shown below:[1]

Spinosauridae

References

  1. ^ a b c d e f g Mateus O, Estraviz-López D (2022). "A new theropod dinosaur from the Early Cretaceous (Barremian) of Cabo Espichel, Portugal: Implications for spinosaurid evolution". PLOS ONE. 17 (2): e0262614. doi:10.1371/journal.pone.0262614.
  2. ^ Mateus, Octávio; Araújo, Ricardo; Natário, Carlos; Castanhinha, Rui (2011-04-21). "A new specimen of the theropod dinosaur Baryonyx from the early Cretaceous of Portugal and taxonomic validity of Suchosaurus". Zootaxa. 2827 (1): 54–68. doi:10.11646/zootaxa.2827.1.3. ISSN 1175-5334.
  3. ^ Arden, Thomas M. S.; Klein, Catherine G.; Zouhri, Samir; Longrich, Nicholas R. (2019-01-01). "Aquatic adaptation in the skull of carnivorous dinosaurs (Theropoda: Spinosauridae) and the evolution of aquatic habits in spinosaurids". Cretaceous Research. 93: 275–284. doi:10.1016/j.cretres.2018.06.013. ISSN 0195-6671.
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