| Riparovenator | |
|---|---|
 | |
| Holotype skull fragments | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Spinosauridae |
| Clade: | †Ceratosuchopsini |
| Genus: | †Riparovenator Barkeret al., 2021 |
| Type species | |
| †Riparovenator milnerae Barkeret al., 2021 | |
Riparovenator ("riverbank hunter") is agenus ofbaryonychinespinosauriddinosaur from theEarly Cretaceous (Barremian) period of Britain. The genus contains asingle species,Riparovenator milnerae.
Between 2013 and 2017, spinosaurid fossils were uncovered at the beach near theChilton Chine before being brought toDinosaur Isle. Such remains had historically been referred toBaryonyx but were understood later to represent two new species.[1]
Theholotype remains of this taxon consist ofIWCMS 2014.95.6 (premaxillary bodies), IWCMS 2014.96.1, 2; 2020.448.1, 2 (a disarticulatedbraincase), and IWCMS 2014.96.3 (a partiallacrimal andprefrontal). Referred remains include a posterior nasal fragment (IWCMS 2014.95.7) and a caudal axial series of twenty-two vertebrae (IWCMS 2020.447.1-39), representing around fifty individual bones in total. All of the material was recovered from rocks in the Chilton Chine of theWessex Formation.[1]
In 2021, thetype speciesRiparovenator milnerae was named anddescribed by a team ofpalaeontologists including Chris T. Barker, David W. E. Hone,Darren Naish, and others. The generic name is derived from theLatinrīpārius, "of the river bank", andvēnātor, "hunter". Thespecific name honorsAngela Milner, deceased in August 2021.[1]
In their phylogenetic analysis, Barkeret al. (2021) recoveredCeratosuchops within theBaryonychinae, as thesister taxon to the coevalRiparovenator. They are, in turn, in a clade containingSuchomimus, which they name Ceratosuchopsini.[1][2]
| Baryonychinae |
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In 2022,Sereno and colleagues tentatively combinedCeratosuchops andRiparovenator into a single taxonomic unit for their phylogenetic analysis. They reason that the different features between the two taxa could be attributed to individual variation, citing the cranial variation present in specimens ofAllosaurus fragilis. Some of their supposed distinguishing features are also seen in parts of the braincase ofSuchomimus, their closest relative. The results of their phylogenetic analysis (withCeratosuchops andRiparovenator scored together) yielded similar results to those of Barkeret al. (2021), with the Wessex baryonychine fossils recovered as the sister taxon toSuchomimus.[3]
Riparovenator lived in a dry Mediterranean habitat in theWessex Formation, where rivers were home toriparian galleries.[4][5] Like most spinosaurids, it would have fed on aquatic prey as well as other terrestrial prey in these areas.[6][7][8]
Other dinosaurs from the Wessex Formation of the Isle of Wight the theropodsCeratosuchops,Neovenator,Eotyrannus,Aristosuchus,Thecocoelurus,Calamospondylus, andOrnithodesmus; the ornithopodsIguanodon,Hypsilophodon, andValdosaurus; the sauropodsOrnithopsis,Eucamerotus, andChondrosteosaurus; and theankylosaurPolacanthus.[9][1] Barker and colleagues stated in 2021 that the identification of the two additional spinosaurids from the Wealden Supergroup,Riparovenator andCeratosuchops, has implications for potential ecological separation within Spinosauridae if these andBaryonyx were contemporary and interacted. They cautioned that it is possible the Upper Weald Clay and Wessex Formations and the spinosaurids known from them were separated in time and distance.[1]
It is generally thought that large predators occur with small taxonomic diversity in any area due to ecological demands, yet many Mesozoic assemblages include two or moresympatric theropods that were comparable in size and morphology, and this also appears to have been the case for spinosaurids. Barker and colleagues suggested that high diversity within Spinosauridae in a given area may have been the result of environmental circumstances benefiting their niche. While it has been generally assumed that only identifiable anatomical traits related to resource partitioning allowed for coexistence of large theropods, Barker and colleagues noted that this does not preclude that similar and closely related taxa could coexist and overlap in ecological requirements. Possible niche partitioning could be in time (seasonal or daily), in space (between habitats in the same ecosystems), or depending on conditions, and they could also have been separated by their choice of habitat within their regions (which may have ranged in climate).[1]
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