| Ceratosuchops | |
|---|---|
 | |
| Holotype skull fragments | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Spinosauridae |
| Clade: | †Ceratosuchopsini |
| Genus: | †Ceratosuchops Barkeret al., 2021 |
| Type species | |
| †Ceratosuchops inferodios Barkeret al., 2021 | |
| Synonyms[1] | |
| |
Ceratosuchops (meaning "horned crocodile face") is agenus ofspinosaurid from theEarly Cretaceous (Barremian)Wessex Formation ofBritain. The type species isC. inferodios, known from skull fragments (a snout tip and a partial braincase) recovered between 2013–2017 fromChilton Chine on theIsle of Wight, and housed at theDinosaur Isle Museum inSandown. It was named in 2021 by a team consisting of Chris Tijani Barker, Darren Naish, David W. E. Hone, and colleagues, alongsideRiparovenator milnerae.
Ceratosuchops is notably distinguished from its close relatives by the presence of a bony lump, known as a boss, which extends from eachpostorbital bone, hence its genus name. These bosses may have served a function in signalling, or, like similar structures in other species, might have been involved incombat behaviours. The size ofC. inferodios is difficult to deduce, given the fragmentary nature of its remains, though it may have been similar to that ofBaryonyx. Analysis of thebraincase andneuroanatomy ofC. inferodios suggests that it was very similar to other basal tetanurans, and that baryonychines likely underwent few changes to their brain anatomy as a result of their shift from terrestrial to aquatic prey.
Ceratosuchops forms part of thetribe Ceratosuchopsini, alongsideRiparovenator and the later, north AfricanSuchomimus, and to the exclusion of the other Wessexbaryonychine (Baryonyx). The presence of up to three ecologically similar taxa (Baryonyx,Ceratosuchops, andRiparovenator) in the same environment ledC. inferodios' describers to suggest that, at minimum, it andRiparovenator were likelyecologically distinct in some way. However, it was tentatively suggested in 2022 byPaul Sereno and colleagues thatC. inferodios andRiparovenator may have been the same taxon, and that the differences between the two were the result of individual variation; accordingly, when conducting aphylogenetic analysis of Spinosauridae, the nameC. inferodios was used for both.
Theholotype remains ofCeratosuchops inferodios consist ofIWCMS 2014.95.5 (premaxillary bodies), IWCMS 2021.30 (a posterior premaxilla fragment), and IWCMS 2014.95.1-3 (a nearly complete braincase). These, in addition to a referred rightpostorbital (IWCMS 2014.95.4), were recovered from rocks inChilton Chine of theWessex Formation, part of theIsle of Wight section of theWealden Supergroup, between 2013–2017. These specimens, alongside the holotype remains ofRiparovenator milnerae, were accessioned at the Dinosaur Isle Museum inSandown. While the remains ofR. milnerae were found in geological context, those ofC. inferodios were recovered fromsandstone blocks found on theforeshore, and their exact stratigraphic location could not be determined.[2]
In 2021,Ceratosuchops inferodios was named anddescribed by a team of palaeontologists including Chris Tijani Barker,Darren Naish, David W. E. Hone, and others. The generic name comes from theGreek κέρας ("horn"), Σοῦχος ("crocodile"), and ὄψ ("face"), referring to the prominent postorbital boss seen in the holotype; thespecific name comes fromLatin īnfernus ("hell, underworld") and Greek ερωδιός ("heron"), referencing the presumption by the research team that its ecology resembled that of modern herons.[2]
Due to the fragmentary nature of the remains, and their restriction to skull material, the overall size ofCeratosuchops cannot reliably be estimated. Based on relative sizes, its body mass was likely similar to that ofBaryonyx.[3]
Thepremaxillae ofCeratosuchops had short subnarial processes (theventral, or bottom, part, where they contacted themaxillae), similar toBaryonyx. On the other hand, the presence of narialfossae, slight depressions in front of eachnaris (nasal opening), more closely resembles a specimen assigned to cf.Suchomimus, to the exclusion of other baryonychines. Twotuberosities projected from the part of the premaxilla which formed theanterior (front) portion of the nares. LikeBaryonyx, the premaxilla lacked asagittal crest. LikeRiparovenator,C. inferodios' postorbital bone was rugose, though in the latter, this rugosity was part of a large postorbitalboss (mass of bone); its describers suggest that, like similar skull ornamentation in other taxa, these bosses may have played a role in signalling within the species, or perhapsagonistic (combative) behaviours. The subcondylar recess ofC. inferodios'basioccipital was narrow, restricted to the ventral portion of the bone, and unlikeBaryonyx orRiparovenator, lacked lateral crests; the dorsal process, meanwhile, was relatively thick like that ofBaryonyx.[2]
In their 2021 phylogenetic analysis, Barker and colleagues recoveredCeratosuchops within theBaryonychinae, as thesister taxon to the coevalRiparovenator. They are, in turn, part of a clade containingSuchomimus, which they name Ceratosuchopsini.[2][4]
| 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 Barker and colleagues, with the Wessex baryonychine fossils recovered as the sister taxon toSuchomimus.[1]
Like most spinosaurs,Ceratosuchops would have fed on available small to medium-sized aquatic and terrestrial prey in these areas, such asfish, smallturtles, youngcrocodiles, babydinosaurs, andmammals.[5][6][7]
A 2023 study by Barker and colleagues based on CT scans of the braincases ofCeratosuchops andBaryonyx found that the brain anatomy of these baryonychines was similar to that of other non-maniraptoriform theropods. Theirneurosensory capabilities such as hearing andolfaction (sense of smell) were unexceptional, and their gaze stabilisation less developed than those of spinosaurines, so their behavioural adaptations were probably comparable to those of other large-bodied terrestrial theropods. This suggests that their transition from terrestrial hypercarnivores tosemi-aquatic "generalists" during their evolution did not require substantial modification of their brain and sensory systems. This could mean that spinosaurids were either pre-adapted for detection and capture of aquatic prey, or that their transition to semi-aquatic lifestyles only required modifications to the bones associated with the mouth. Theirreptile encephalization quotient values imply that the cognitive capacity and behavioural sophistication of baryonychines did not deviate much from that of otherbasal theropods.[8]
Thetype specimen ofCeratosuchops comes from the Wessex Formation.[9]Sedimentological data suggests that the depositional environment of the Wessex Formation was afloodplain intersected byfluvial (river) andlacustrine (lake) deposits. Water levels likely varied throughout the year,[10] due to there being more evaporation than precipitation, though precipitation was regardless quite high. The Wessex seems to have regularly experienced extreme storms[11] and periodic flood events, resulting in debris flows which would have deposited dead organisms in ponds.[12] Burned plant and insect material andfusain suggests that the environment experienced frequentwildfires, stifling for the most part the dense growth ofgymnosperms.[10][12] Much of the flora of the formed of low ground cover, consisting primarily ofpteridophytes, with occasional stands ofconifers,cycads and the tree fernTempskya.[10] Most vertebrate material from the Wessex Formation originates from plant debris beds, resulting from the aforementioned flooding events.[12]
Aside fromCeratosuchops, the dinosaur fauna of the Isle of Wight includes the theropodsAristosuchus,Calamospondylus,Eotyrannus,Neovenator,Ornithodesmus,Riparovenator andYaverlandia, the sauropodsChondrosteosaurus,Eucamerotus, andOrnithopsis,[2][13] the thyreophoransPolacanthus[13] andVectipelta,[14] and the ornithopodsBrighstoneus,[15]Comptonatus,[16]Hypsilophodon,Iguanodon,[13]Mantellisaurus,[17]Valdosaurus[2][13] andVectidromeus.[18] Thepterosaur fauna of the Wessex Formation consists ofColoborhynchus,Caulkicephalus,Istiodactylus,[19]Vectidraco,[20] andWightia;[21] multiple unnamed pterosaur taxa, including actenochasmatid, are also known.[19]Neosuchiancrocodyliforms includeBernissartia,Koumpiodontosuchus[22] andVectisuchus.[23] Limited evidence exists ofelasmosaurids andleptocleididplesiosaurs.[9] The mammal fauna of the Wessex Formation includes themultituberculateEobataar[3] and thespalacotheriidYaverlestes.[24]Albanerpetontid amphibians are represented byWesserpeton.[25] The fish fauna of the Wessex Formation, bothbony andcartilaginous, is extensive, includinghybodontiform and modernsharks (Selachii),pycnodontiforms,Lepidotes andScheenstia.[26] Invertebrates are represented by an assortment ofnon-biting midges,[27]hymenopterans (wasps) including multipleparasitoid taxa,[28]coleopterans (beetles), theavicularoid spiderCretamygale,[29] and theostracodCypridea.[30]
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.[2]
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).[2]
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