| Dornraptor | |
|---|---|
 | |
| Known fossil material | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Clade: | Averostra |
| Genus: | †Dornraptor |
| Species: | †D. normani |
| Binomial name | |
| †Dornraptor normani | |
| Synonyms | |
Dornraptor (meaning "Dorset robber or thief") is an extinct genus ofaverostran, possiblystemtetanuran, theropod dinosaur from the EarlyJurassic (LateSinemurian) ofCharmouth,Dorset, England. The genus contains asingle species,D. normani, known from a fragmentary knee joint and femur that were initially described bySir Richard Owen as belonging to the early armored dinosaurScelidosaurus.[5]Dornraptor lived in what is now England, along other theropods likeDracoraptor andSarcosaurus.
Dornraptor was described as having come from theBlue Lias Formation in 2024, although previous authors proposed a corrected locality of theCharmouth Mudstone Formation.[1]
.png)
In 1858,Richard Owen received fragmentary dinosaur leg bones discovered by James Harrison inCharmouth,Dorset. These included a right knee joint—comprising the articulated distal end of thefemur and a proximal third of thetibia andfibula—and a partial left femur. He used them as part of the type material of the thyreophoranScelidosaurus when describing it in 1859.[5][6] Subsequent studies reconsidered their classification, suggesting early theropod affinities within the Saurischia, rather than an early thyreophoran within the Ornithischia.[2]
Theinformal name "Merosaurus newmani" was coined bySamuel Paul Welles, H. P. Powell, and Stephan Pickering in 1995 in an unpublished manuscript for the theropod material.[3][4][7] Carrano and Sampson (2004) proposed that the articulated knee joint likely belonged to a basal, indeterminate tetanuran theropod.[8]Darren Naish andDavid Martill (2007) also assigned these specimens to the Tetanurae.[9] In 2010, Roger Benson suggested that the bones could be attributed to theCoelophysoidea, while ultimately concluding that both specimens were indeterminate theropods.[10]
In 2024,Dornraptor normani was formallydescribed as a new genus and species of averostran theropod by Matthew G. Baron. He establishedNHMUK (BMNH) 39496, the right knee joint, as theholotype specimen. The partial fibula originally described by Owen as belonging to this specimen has since been lost.GSM 109560, the left femur, was also referred to the genus. Thegeneric name,Dornraptor, combines "Dorn", an abbreviated form of theAnglo-SaxonDornwaraceaster—referring to the English region of Dorset—with theLatin word "raptor", meaning "robber" or "thief", which is frequently used in the names of small- and medium-sized theropods. Thespecific name,normani, honours British palaeontologistDavid B. Norman.[2]
Dornraptor stands out from other theropods due to a large scar along themedial side of thedistal end of the femur, a medial distal crest, and a prominentanterior trochanter separated from the head by a cleft. Additionally, it possesses a shallow trochanteric shelf and aforamen on the anterior surface of the femur. Its femur also features a deep anteriorsulcus between the articularcondyles and a medial condyle with similaranteroposterior diameter to the width of the articular surface.Dornraptor exhibits an elongatedcnemial crest reaching proximally beyond the medial and lateral condyles, along with a pronounced fibular crest extending up to the proximal end of the tibia. Thelateral side of the tibia also displays a sharp crest parallel to the fibular crest, forming a distinct bulge distally. Additionally, the proximal end of the tibia shows a separate crest, not connected to the fibular crest, and a noticeable cleft between the posterior condyles. Lastly, the lateral condyle of the tibia forms an acute angle when viewed from the medial side.[2]
Early reviews of the fossil material suggestedcoelophysoid,tetanuran, andceratosaurian affinities.[10][8][9]While specimens NHMUK 39496 and GSM 109560 lack anatomical overlap, their discovery in the same stratigraphic unit, along with similar size and proportions, suggests they belong to the same taxon, distinct from earlier forms and contemporaneous taxa likeDracoraptor andSarcosaurus. Utilizing a modified version of the Baron et al. (2017)phylogenetic dataset,[11]Dornraptor was found to be an early-branchingaverostran theropod in a polytomy withElaphrosaurus,Cryolophosaurus, and the clade containingAllosaurus andPiatnitzkysaurus. This clade was recovered as thesister group to a clade containing theceratosaursEoabelisaurus andCeratosaurus. These results are displayed in thecladogram below, withDornraptor and the contemporary non-averostransDracoraptor andSarcosaurus inbold:[2]
ScoringDornraptor in other matrices also resulted in its placement in variousbasal positions within the Averostra, outside of the major cladesAbelisauroidea andCoelurosauria.[2]
Following the formal description ofDornraptor, Mickey Mortimer discussed it on the Theropod Database blog, noting that some of the characters used by researchers to exclude tetanuran affinities for the holotype are found in some basal members of this clade, such asChuandongocoelurus,Dubreuillosaurus, andEustreptospondylus. One definitive feature—the bulbous fibular crest—supportsDornraptor as a tetanuran, as it is found in genera includingMegalosaurus,Piatnitzkysaurus, andSinraptor. The referred femur is similar toDilophosaurusLiliensternus, ceratosaurs, and tetanurans, suggesting it either comes from a gracile ceratosaur or a tetanuran.[12]
TheCharmouth Mudstone Formation and underlyingBlue Lias were mostly shallow marine environments, with both formations containing a wide variety of marine fossils, including variousammonites,belemnites,crinoids,mollusks, andcrustaceans. Marine invertebrates includeichthyosaurs,plesiosaurs, andthalattosuchians. Occasionally, rare small pieces of fossilized wood are found.[13][14] Inner continental landmasses were an archipelago of large islands inherited fromCaledonian andVariscan massifs, where the Dorset area was part of theWessex Basin, bordered by the London-Brabant,Armorican,Cornubian, andWelsh Massifs, divided into sub-basins by east-west faults that were the source for siliclastic material, as recorded in coeval boreholes.[15] The basin was deposited on theMid-Dorset High fault block. Generally in the Early Jurassic there was a regional and global marine transgression, covering northwest Europe with a shallow sea, punctuated by smaller sea-level changes, locally driven by a mix of global sea-level shifts and local geological movements. Sea levels rose during the Lower Sinemurian (turneri andraricostatum Zones) and fell during the Late Sinemurian (obtusum andoxynotum) Zones on theLondon Platform, at the timeDornraptor and other dinosaurs are recovered.[13]
Other dinosaurs from the locality include the well-known thyreophoranScelidosaurus, as well as indeterminate theropod remains suggesting smallerCoelophysis-sized taxa, withDornraptor likely being the terrestrial apex predator.[1] Other terrestrial taxa include the pterosaurDimorphodon, as well the synapsidOligokyphus.[16][17] A large insect fauna is known, made ofbeetles,blattodeans,dragonflies,grasshoppers, etc.[18] The flora included members of theBennettitales,Corystospermaceae andconifers.Palynology indicates the presence of taxa like the "seed ferns"Alisporites, the "cycadophyte"Chasmatosporites, and the dominantHirmeriellaceae coniferCorollina andClassopollis, suggesting arid or semiarid environments, usually compared with modernMediterranean islands.[19]
.jpg)
.jpg)
.png)
.jpg)
