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Riojavenatrix

MEANING: La Rioja huntress

PERIOD: Early Cretaceous

CONTINENT: Europe


Riojavenatrix is one of the most recent baryonychines to have lived. Like other spinosaurids, it was a large bipedal theropod with specializations for feeding in aquatic habitats, and likely fed on fish, though it may have been a more versatile predator. Riojavenatrix is estimated to have grown up to 8 m in length, and weighed around 1.5 t in body mass.


Riojavenatrix

Abstract from paper: A new member of Spinosauridae from the Enciso Group (uppermost Barremian–lower Aptian) from Igea (La Rioja, Spain) is here erected on the basis of axial, pelvic girdle, and hindlimb elements that exhibit a unique combination of characters. Riojavenatrix lacustris gen. et sp. nov. is one of the latest Iberian and European spinosaurid taxa. It retains a triangular pubic boot, like the megalosaurids, and a medial condyle of the femur that shows a transitional stage between the anteroposteriorly oriented long axis of non-spinosaurid theropods and the posteromedially oriented long axis of Spinosauridae. The spinosaurid record of Iberia ranges from the late Hauterivian–early Barremian to the latest Barremian–early Aptian so far, and both the oldest and the most recent evidence comes from the Cameros Basin, where spinosaurid remains are especially abundant in the Barremian deposits. A review of the spinosaurid record has allowed us to dismiss the presence of the genus Baryonyx from Iberia; hence, only Camarillasaurus, Iberospinus, Protathlitis, Riojavenatrix gen. nov., and Vallibonavenatrix are considered to be present in the Early Cretaceous of Iberia. According to this study, Riojavenatrix is one of the youngest baryonychines in the fossil record.



Riojavenatrix is from the Cretaceous. The Cretaceous is a geological period that lasted from about 145 to 66 million years ago. It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of the entire Phanerozoic. The name is derived from the Latin creta, "chalk", which is abundant in the latter half of the period.


The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct flora and fauna, while dinosaurs continued to dominate on land. The world was ice free, and forests extended to the poles. During this time, new groups of mammals and birds appeared. During the Early Cretaceous, flowering plants appeared and began to rapidly diversify, becoming the dominant group of plants across the Earth by the end of the Cretaceous, coincident with the decline and extinction of previously widespread gymnosperm groups.


The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary (K–Pg boundary), a geologic signature associated with the mass extinction that lies between the Mesozoic and Cenozoic Eras.


Riojavenatrix is a spinosaurid. Spinosaurids are a group of large theropod dinosaurs, mainly from the Early Cretaceous. They are known for their crocodilian-like skulls with long narrow snouts. The tips of their upper and lower jaws fanned out into a spoon-shaped structure, with a notch in the upper jaw that the tip of the lower jaw fit into. The nostrils of spinosaurids were further back on the snout than in most other theropods. Adaptations such as these suggest that they were at least partially piscivorous, and likely led a semi-aquatic lifestyle.


Spinosaurids had bony crests on their heads along the midline of their skulls, and large arms, with three-fingered hands. In many species, the neural spines of the vertebrae were elongated and formed a sail-like structure on the animal's back, giving the group their name. The genus Spinosaurus, from which the clade gets its name, is the longest known terrestrial predator from the fossil record, with an estimated length of up to 14 m and body mass of up to 8 t.

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