Neovenator

The first bones of Neovenator were discovered in the summer of 1978 when a storm made part of the Grange Chine collapse. Rocks containing fossils fell to the beach of Brighstone Bay on the southwestern coast of the Isle of Wight. They were first collected by the Henwood family and shortly afterwards geology student David Richards collected additional material. Richards sent the remains to the Museum of Isle of Wight (now Dinosaur Isle) and the British Museum of Natural History. In the latter institution, palaeontologist Alan Jack Charig determined that the bones belonged to two kinds of animal: Iguanodon and a theropod. The "Iguanodon", later referred to Mantellisaurus and ultimately made the separate genus Brighstoneus, generated the most interest and in the early 1980s a team was sent by the BMNH to secure more material. The theropod material, meanwhile, was fairly incomplete (consisting of vertebrae and fragments of the pelvis), and a lack of diagnostic features meant that it was ignored until its significance was recognised by Dr. William Blows. consisting of a lower jaw, parts of the cervical (neck) vertebrae and limb elements. In 1990 the material, then considered a possible new species of Megalosaurus, was provisionally described by Hutt. Having mistaken the ischium of MIWG 6352 for a pubic bone, Hutt suggested this specimen represented a separate species. In 1996, Steve Hutt, David Martill and Michael Barker named and described the type species Neovenator salerii. The generic name Neovenator means "new hunter" from the Greek neo~, "new" and Latin venator, "hunter". The specific name salerii honours the land owners of the site, the Salero family. In view of the large number of individuals involved in the discovery process, it was considered improper to single out one of them as discoverer. The holotype is the skeleton accessioned as BMNH R10001 and MIWG 6348. In 1999, Hutt dedicated his (unpublished) master thesis to Neovenator. This thesis would form the foundation for a monograph discussing the osteology of the genus. That monograph was published in 2008, and was authored by Stephen L. Brusatte, Roger B. J. Benson and Hutt by the Palaeontographical Society. In 2012, teeth indistinguishable from those associated with the holotype of Neovenator were found in the Angeac-Charente bone bed, in France, dating to the Berriasian. They were distinguished from those of Erectopus, a basal allosauroid also known from the Early Cretaceous of France, by differences in the carinae of their teeth. == Description ==

Size Neovenator was a mid-sized, lightly built carcharodontosaurid. The holotype specimen measured approximately in length, and was fairly lightly built. It has been suggested that the holotype may be a subadult, and if this is the case, this may not be reflective of the maximum body size of the genus. However, in 2016, Jeremy Lockwood noted that most of the elements referred to Neovenator are roughly the same size as the holotype, suggesting that adults would have had a similar body size. Specimen MIWG 4199 indicates an individual with a possible length of about , A footprint (IWCMS:2016.273) is believed to have been left by an animal with a hip height of , and while the trackmaker is uncertain, it has been suggested that it was left by a mature Neovenator. The left maxilla, as preserved, measures around in length, and in depth. Only a small portion near where the jugal connected is missing. As in many basal tetanurans (and the more derived Carcharodontosaurus), the maxilla contributed to the posterior (rear) border of the external naris (nasal opening). Similar to abelisaurids and other allosauroids (i.e. Giganotosaurus, Mapusaurus and Sinraptor), the surface of the maxilla bore prominent rugosities, and contains a high density of foramina, particularly at its anteriormost (very front) portion, ventral to (below) the external naris. It has been suggested that Neovenators snout was highly vascularised or innervated. Unlike many other allosauroids and ceratosaurs, the ascending ramus lacked pneumatic excavation (hollow spaces containing air pockets). The neural spines of the cervical vertebrae were narrow anteroposteriorly (from front-to-back), are thick transversely, and were overall rod-like in shape. The seventh was inclined posteriorly, the eighth anteriorly, and the ninth directly vertically.The first two dorsal vertebrae were morphologically intermediate between the cervical and dorsal vertebrae, being, among other things, short anteroposteriorly when compared to dorsal vertebrae further along the column. The remaining dorsal vertebrae were fairly homogenous in morphology, characterised by their tall centra and biconcave articular surfaces. Each dorsal vertebra had transverse processes which are broad anteroposteriorly yet thin dorsoventrally (up-and-down). Their neural spines are subrectangular in lateral view and are thick transversely, at least in comparison to most non-allosauroid tetanurans. Two large fragments of the dorsal ribs are known, one better-preserved and coming from the left side of the torso, and the other coming from the right side. Some disarticulated gastralia (constituent bones of the gastral basket, which supported the organs and aided in respiration) are known. Sacral vertebrae are known from referred specimens. The second and third sacral vertebrae were fused, unlike Acrocanthosaurus and Sinraptor, but like some specimens of Allosaurus. The second and fourth sacrals are known exclusively from their centra, so the neural arches of the sacra are poorly known. The first caudal vertebra of the holotype is poorly preserved due to damage sustained during the cliff fall, thus leaving the second as the best preserved. Though most of the anterior and middle caudal vertebrae are damaged, the distal ones are fairly complete. The anterior caudal centra had suboval articular surfaces, and posterior surfaces smaller than the anterior surface, and this pattern continues until the vertebra tentatively identified as the twenty-second. Appendicular skeleton The left scapula and coracoid of Neovenators holotype are nearly complete, though its forelimbs are not known. Around two-thirds of the glenoid fossa's length is taken up by the scapula. While well-preserved, the coracoid is damaged enough that most of the point where it articulated with the scapula is absent. The shoulder joint is wider transversely than anteroposteriorly. On the medial surface of the scapulocoracoid, the glenoid is buttressed by a slight ridge, which fans out posteriorly to unite with the ventral margin of the scapular blade. The ilia of Neovenator, including referred elements, are fragmentary. Ventral to the ilium's front blade is a notch, which has a robust shelf on the inner side. The ilium overall is highly pneumatised. While a right pubis is preserved, it is fragmentary, heavily abraded and badly crushed. Distally, it expands into a large pubic boot, similar to that of other carcharodontosaurs and tyrannosaurids. The "feet" of the ischia are connected anteriorly but diverge posteriorly; the ischiac feet were expanded, another trait observed in other carcharodontosaurs. Like in other carcharodontosaurs, and in some tyrannosaurids, Neovenators femoral head is angled dorsomedially (upwards and towards the centrum). The lesser trochanter of the femur has a robust ridge on its outer side, and is itself extremely robust. The fourth trochanter has a depression in the form of a thumbprint located laterally on its dorsal border. The distal portion of the tibia shows an oval rough area at the inner side. The top of the outer malleolus of the tibia is pinched from the front to the rear. The outer front bulge of the top surface of the tibia has a spur deflected ventrally. In the foot, the outer side of the second metatarsal has a hollow surface to contact the third metatarsal. == Classification ==

|leftIn the 1996 paper describing Neovenator, Hutt, Martill and Barker suggested a close relationship with Allosaurus, and that Neovenator might itself have been a member of Allosauridae. However, that topology was the result of incorrect scoring, and two of the characters used to unite the two genera (prezygapophysis morphology and the distal expansion of the scapula) are respectively erroneous and uncorrelated with phylogeny. The idea of Neovenator being a "proto-carcharodontosaurid" was first put forward by Jerald D. Harris in 1998, and was supported by Darren Naish, Steve Hutt, and David Martill in 2001, based on the presence an inflated "boot" to each ischium and of pleurocoels (pneumatic hollows) throughout the vertebrae, both classically carcharodontosaurian traits. If this is the case, Neovenatoridae is likely monotypic. Fernano Novas et al. (2013) recovered Neovenator at the base of Carcharodontosauridae, in a polytomy with Eocarcharia and Concavenator. }} == Palaeobiology ==

Senses Chris Barker and colleagues suggested that Neovenator may have possessed integumentary sensory organs on its snout, much as modern waterfowl and crocodilians use to find food in muddy water, based on neurovascular structures found on the skull. As Neovenator is believed to be completely terrestrial, unlike the modern species, it is assumed that these sensory organs were used for other purposes, such as sensitivity to pressure and temperature, controlling jaw pressure and precision feeding. In support of this, the tooth wear for Neovenator seems to indicate that it avoided eating or biting into bone while it fed. Additionally, Neovenator might have used these integumentary sensory organs in courtship and sensing nest conditions, a technique seen today in most species of crocodilians and megapode birds. Though such structures are known for another theropod, the tyrannosaurid Daspletosaurus horneri, Neovenators neurovascular structures that likely supported these organs are the best preserved and most complete in any known theropod yet discovered. However, a more recent study reviewing the evolution of the trigeminal canals among sauropsids notes that a much denser network of neurovascular canals in the snout and lower jaw is more commonly encountered in aquatic or semiaquatic taxa (e.g., Spinosaurus, Halszkaraptor, Plesiosaurus), and taxa that developed a rhamphotheca (e.g., Caenagnathasia), while terrestrial taxa such as tyrannosaurids and Neovenator may have had average facial sensitivity for non-edentulous terrestrial theropods, although further research is needed. Palaeopathology As with many specimens of Allosaurus, the holotype of Neovenator salerii was highly pathological. The pathologies listed in the 1996 paper and the 2008 monograph: are the fusion of two caudal vertebrae and their associated chevron into a single mass (also seen in certain Allosaurus and likely the result of neoplastic ankylosis); healed fractures to the gastralia; a fracture to the scapula; one gastralium which appears to exhibit regrowth across its entire length, and osteophytes on some of the pedal (foot) phalanges. One of the left pedal phalanges has been almost completely covered by exostotic bone growth and small lesions, suggesting osteomyelitis, similar to one specimen of Allosaurus. == Palaeoecology ==

Palaeoenvironment The only definite remains of Neovenator are known from the Barremian-age Wessex Formation of the Isle of Wight, though teeth identical to the genus are known from the Berriasian-age due to there being more evaporation than precipitation, though precipitation was regardless quite high. The Wessex seems to have regularly experienced extreme storms and periodic flood events, resulting in debris flows which would have deposited dead organisms in ponds. Burned plant and insect material and fusain suggests that the environment experienced frequent wildfires, stifling for the most part the dense growth of gymnosperms. the thyreophorans Polacanthus and the ornithopods Brighstoneus, Hypsilophodon, Iguanodon, Valdosaurus The pterosaur fauna of the Wessex Formation consists of Coloborhynchus, Caulkicephalus, Istiodactylus, Vectidraco, and Wightia; multiple unnamed pterosaur taxa, including a ctenochasmatid, are also known. and Vectisuchus. Limited evidence exists of elasmosaurids and leptocleidid plesiosaurs. The mammal fauna of the Wessex Formation includes the multituberculate Eobataar and the spalacotheriid Yaverlestes. Albanerpetontid amphibians are represented by Wesserpeton. Invertebrates are represented by an assortment of non-biting midges, hymenopterans (wasps) including multiple parasitoid taxa, coleopterans (beetles), the avicularoid spider Cretamygale, and the ostracod Cypridea''. If Neovenator was indeed present in the older Angeac-Charente bone bed, it would have been part of an entirely different, less well-understood faunal assemblage. The depositional environment of the Angeac-Charente was likely a tropical or subtropical floodplain combined with a poorly oxygenated swamp, with a flora dominated by cheirolepidiacean conifers. Most of the vertebrate fauna of the locality appear to have inhabited and been preserved in the swamp, making it among the few swamp bone beds. The most well-known dinosaur fossils from the Angeac-Charente are an indeterminate basal ornithomimosaur, whose fossils are known in great numbers. Other theropod clades are represented by teeth, including large teeth which have been tentatively assigned to megalosaurids. Remains of a dacentrurine stegosaurian, similar to Dacentrurus, are also known. Some ornithischians are known, including camptosaurs, hypsilophodontids, an indeterminate ankylosaur, and Echinodon sp. Two indeterminate pterodactyloid pterosaurs have been identified. Predation Neovenator was likely similar to other allosauroids in terms of feeding and hunting behaviour, likely targeting smaller species (or juveniles of larger species). There is evidence in the form of bite marks that Neovenator likely preyed on Mantellisaurus. Darren Naish, Steve Hutt and David Martill noted in 2001 that allosauroids in general had limb proportions poorly suited for great speeds, and that Neovenator likely would have hunted through ambush. They speculated that, like what has been suggested for other allosauroids, Neovenator may have ganged up on large prey in a similar fashion to certain crocodilians and Komodo dragons. Since ontogenetic niche partitioning, where juveniles occupy different niches to the adults, has been suggested for certain non-avian dinosaurs, Naish, Hutt, and Martill hypothesised that the same might have applied to Neovenator. Taphonomy The holotype of Neovenator was recovered from a plant debris bed, underlain by sandstone and mudstone, and overlain by further mudstone. Its remains were found in association with multiple fossil logs, bivalves of the family Unionidae, and a partial skeleton of the iguanodontid Brighstoneus. Despite being discovered close to one another, it is likely that the two specimens were swept together by one of two sedimentary pulses (one indicative of a small flood, the other indicative of a far larger flood) which formed the locality. == References ==