Megaraptora is a family belonging to the Allosauroidea
Family members[]
Description[]
Megaraptorans were medium to large-sized theropods, ranging from Fukuiraptor, which was about 4.2 meters (13.8 feet) in length, to the 9 meter (30 feet) long Aerosteon, the 9 to 10 meter (30 to 33 feet) long Maip and the 12.8 meter (42 foot) long Bahariasaurus, if it is a member. Most megaraptorans are known from very fragmentary remains, although certain characteristics can be identified in multiple members of the clade. At least some megaraptorans, such as Murusraptor and Aerosteon, had extensively pneumatic bones (most noticeably the ilia and ribs), which likely housed sinuses connected to the lungs, similar to modern birds. The slender leg bones and long metatarsals of several species indicate that members of this group likely had cursorialhabits. Most megaraptorans are part of the family Megaraptoridae, which was named by Fernando Novas and his colleagues in 2013. This family is united by several adaptations of the ulna and claws which are not present in the basal megaraptoran Fukuiraptor.
Skull and teethedit[]
link=https://en.m.wikipedia.org/wiki/File:Megaraptor_bust.png|alt=|thumb|A restoration of the head of Megaraptor, based on a juvenile specimen No megaraptoran fossil is known to preserve a complete skull, although skull material is known for several taxa. Aerosteon, Megaraptor,Orkoraptor, and Murusraptorpreserve several bones of the rear part of the skull, lower jaws are known from Australovenator, and a juvenile specimen of Megaraptor described in 2014 preserved much of the snout as well as parietal fragments. Teeth have been found in many genera. Collectively, megaraptorans can be reconstructed as having a long, lightly built skull with many relatively small teeth.
Based on Megaraptor, the premaxillary bone at the tip of the snout is small, with a long and rod-like branch of bone which extends above the external nares (nostril holes). The nares themselves were very large and elongated, akin to some early tyrannosauroids (Dilong, Proceratosaurus, etc.). The snout also had some similarities to carcharodontosaurids, namely the straight upper edge of the maxilla and rectangular nasal bones. The parietal bones at the top of the skull, behind the eyes, had a strongly developed sagittal crest, as in tyrannosauroids. Otherwise, the rear part of the skull is rather simple, without any pronounced crests or bosses, although the lacrimal and postorbital bones did have rugosepatches in some genera. Aerosteon and Murusraptor possessed a pneumatic quadrate, as in a few allosauroids (Sinraptor, Mapusaurus) and tyrannosauroids. The dentary, which is only known in Australovenator, is long and graceful, with the first tooth smaller than the rest (as in tyrannosauroids). The mandible as a whole has only a single meckelian foramen, as in carcharodontosaurians, tyrannosaurids, and ornithomimids. However, the rear part of the mandible (as seen in Murusraptor) was significantly more lightly built than that of tyrannosauroids. Preserved braincase material has similarities to both carcharodontosaurians and tyrannosauroids.
The premaxillary teeth of Megaraptor were variably similar to those of tyrannosauroids, being small, incisiform (chisel-like) and D-shaped in cross section. However, Murusraptor's premaxillary teeth were fang-like, as in non-tyrannosauroid theropods. Megaraptoran maxillary teeth show much variety between genera, although they were generally small compared to the snout with minimal enamel ornamentation. Some megaraptorans, such as Orkoraptor, Australovenator, and Megaraptor, had teeth which were 8-shaped in cross section and completely unserrated from the front (similar to dromaeosaurids and compsognathids), while Murusraptor had anterior serrations only at the tip of its teeth. Fukuiraptor had very laterally compressed and blade-like teeth (similar to carcharodontosaurs) with both anterior and posterior serrations.
Vertebrae and ribsedit[]
[[null|link=https://en.m.wikipedia.org/wiki/File:Aerosteon_cervicals.png%7Calt=%7Cleft%7Cthumb%7COpisthocoelous cervical vertebrae from Aerosteon]] The cervical (neck) vertebrae of megaraptorans were nearly unique among theropods in the fact that they were strongly opisthocoelous. This means that they were convex from the front and concave from behind. Opisthocelous vertebrae are also characteristic of Allosaurus and sauropods, and they may facilitate high flexibility without sacrificing defense against shear forces.Otherwise, the cervicals were similar to those of carcharodontosaurians, with short neural spines, transverse processes (projecting rib facets) located around mid-length on the centra, and a pair of large lateral pits known as pleurocoels. In fact, one or more pleurocoels were present in most megaraptoran vertebrae, and they connected to a complex system of numerous small air pockets within the vertebrae. This web-like internal structure of megaraptoran vertebrae (and that of a few other theropods) has been described as "camellate".
The proximal caudals (vertebrae at the base of the tail) had a longitudinal ridge running along their lower surface, similar to the case in Neovenator but unlike tyrannosauroids. They also had a pair of lateral ridges which stretched downwards from the transverse processes to the centra. These ridges, known as centrodiapophyseal laminae, defined a large depression (infradiapophyseal fossa) under the transverse processes. Although these ridges were also present in dorsal (back) vertebrae and have been found in other theropods, megaraptorans were practically unique in the fact that their centrodiapophyseal laminae were well-developed at the base of the tail, sometimes even more so than the dorsal vertebrae. Only spinosaurids share this feature. The strong development of these ridges may indicate that the tail was deep and muscular.
The dorsal ribs were thick and curved yet hollow and pierced by a hole near their connection to the vertebrae. The gastralia(belly ribs) were wide and strongly built paddle-shaped structures, with the left and right sides fused at the midline of the chest. These features signified that megaraptorans were wide-bodied theropods, akin to the condition in tyrannosaurids.
Forelimbsedit[]
Megaraptorans have a sigmoid (S-shaped) humerus (forearm bone), similar to that of both basal allosauroids and basal coelurosaurs. Most megaraptorans had large, robust humeri akin to those of Allosaurus, but the basal-most member Fukuiraptor has a much more slender humerus. The distal part of the humerus (near the elbow) has a well-developed system of condyles and grooves similar to that of coelurosaurs, particularly the dromaeosaurids. link=https://en.m.wikipedia.org/wiki/File:Megaraptor_hand.jpg|alt=|thumb|260x260px|The lower arm of Megaraptor The ulna of megaraptorids is characteristic in several regards. The olecranon process is well-developed, though it is thin, blade-like, and extends as a crest longitudinally down the shaft of the ulna. In addition, megaraptorids have acquired another long, crest-like structure on the ulna called the lateral tuberosity, which is perpendicular to the blade of the olecranon. As a result, the ulna of megaraptorids is T-shaped in cross section, with three prongs formed by the forward-projection anterior process, the outwards-projecting lateral tuberosity, and the backwards-projecting olecranon process. These adaptations are absent in the most basal megaraptoran, Fukuiraptor. The radius is not unusual compared to other theropods.
Megaraptorans also had very characteristic hands. The first two fingers were large and slender, but the third one was small. These relative differences in finger length are somewhat similar to the case in tyrannosauroids and various other basal coelurosaurs, but the megaraptoran trend of forearm and finger enlargement is opposite to the trend towards forearm diminishment which characterizes advanced tyrannosauroids. Megaraptor retained a vestigial fourth metacarpal, the hand bone that would have connected to the fourth finger in early dinosaurs. This was a primitive feature lost by most other tetanurans. The first two fingers had absurdly large unguals (claws); in Megaraptor the first claw was larger than the entire ulna. Unlike the large unguals of many other theropods (megalosauroids, for example), megaraptoran claws were thin and oval-shaped in cross-section. These claws also had asymmetrically-positioned grooves on their flat faces and a sharp ridge on their lower edge in megaraptorids (non-Fukuiraptormegaraptorans). The carpus (wrist) of megaraptorans incorporated a semilunate (crescent-shaped) carpal similar to that of maniraptorans.
Examinations of the forelimbs of megaraptorans by Rolando, Novas, and Porfiri et al., that were published in January, 2023 show that the megaraptorans' forelimb bones are remarkably well-developed; powered by strong pectoral and front limb muscle that were functionally significant and important to the paleobiology of this group of theropods. Their data also suggests these muscle attachments became increasingly pronounced through megaraptoran evolutionary history, being substantially better developed in derived taxa such as Australovenator and especially Megaraptor itself than in earlier genera such as Fukuiraptor. Their results further suggest that the highly specialized forelimbs were capable of highly complex movements, such as great extension and flexion, particularly in the highly derived hands, as well as enhanced humeral protraction; attributes that likely aided in prey capture.
Hindlimbsedit[]
link=https://en.m.wikipedia.org/wiki/File:Australovenator_tibiae.png|alt=|left|thumb|219x219px|The left and right tibiae of Australovenator in multiple views. Note the structure of the front surface of the distal tip (seen in C and O). The femur (thigh bone) of megaraptorans is only known in Australovenator and Fukuiraptor, but it is similar to that of coelurosaurs in several respects. For example, the greater trochanter is well-developed and offset from the femoral shaft by a deep concavity. The size of the greater trochanter has the added effect of making the portion of the femur near the hip socket rectangular, when seen from above. In non-coelurosaur theropods, the greater trochanter is small, making the femur teardrop-shaped when seen from above. The femoral head is slightly upturned as in carcharodontosaurians (particularly carcharodontosaurids) and some coelurosaurs. In megaraptorans, the portion of the femur near the knee is asymmetrical when seen from the front due to the lateral condyle projecting further distally than the medial condyle.
The tibia was also similar to that of coelurosaurs. It was a long and thin bone. The front of the lateral condyle of the tibia hooks downwards, similar to the condition in Neovenator, Tanycolagreus, and some tyrannosauroids. The medial and lateral malleoli are expanded and project away from each other, as in advanced tyrannosauroids (both) and carcharodontosaurians (medial malleolus only). The front surface of the distal tip of the tibia (near the ankle) had the form of a flattened facet for the reception of the astragalus bone of the ankle, similar to the case in coelurosaurs. The inner edge of this facet was defined by a ridge, a feature unique to megaraptorids. The upper edge of the facet lacked a well-defined supra-astragalar buttress, unlike allosauroids. The ascending process of the astragalus, which lays on the facet, is expanded into a large trapezoidal plate of bone, similar to coelurosaurs but unlike the small, triangular ascending process of allosauroids. Fukuiraptor, Australovenator, and Aerosteon have a distinct forward-pointing prong on the outer edge of the astragalus, and Fukuiraptor and Australovenator have an additional prong that projects backwards.
The fibula is also long and strongly tapers away from the knee, as in coelurosaurs. It connects to a small facet on the outer edge of the astragalus (as in coelurosaurs) rather than a large facet on the upper edge (as in allosauroids). Near the knee and facing the tibia, the fibula has a wide groove or depression known as a proximomedial fossa. Metatarsal III, the foot bone which connected to the middle toe, was very long and slender in all megaraptorans, as in coelurosaurs. The joint for the middle toe is tall and pulley-shaped, with a deep and crescent-shaped depression visible from below.
Hipedit[]
link=https://en.m.wikipedia.org/wiki/File:Aerosteon_ilium_photos.png|alt=|thumb|209x209px|The ilium of Aerosteon. Pneumatization is visible on the main blade in medial view (B) and the pubic peduncle in lateral view (A). The ilium (upper plate of the hip) was a heavily pneumatized bone, filled with air pockets and perforated by pits. The only other large theropod known to possess a pneumatic ilium is Neovenator. In some megaraptorans, the preacetabular blade has a notch along its front edge, as in tyrannosauroids but also in Neovenator. A stronger concavity was present a bit lower, between the preacetabular blade and pubic peduncle. This concavity, known as the cuppedicus (or preacetabular) fossa, was rimmed by a prominent shelf on the inner face of the ilium. This trait is also known in various coelurosaurs, Chilantaisaurus, and probably Neovenator. The postacetabular blade, on the other hand, lacks a large concavity. In non-coelurosaurian tetanurans, this portion of the ilium has a large depression known as a brevis fossa, which is visible from the outer face of the ilium. However, coelurosaurs and megaraptorans have a much smaller brevis fossa which occupies only a portion of the rear edge of the ilium, and it is mostly hidden from outside observers.
The ischium (rear lower plate of the hip) is only known in Murusraptor. It is slightly expanded, similar to that of carcharodontosaurids. The pubis (front lower plate of the hip) has a much more pronounced scythe-like expansion at its tip, which is over 60% as long as the main shaft of the bone. This adaptation, known as a pubic boot, is also known in carcharodontosaurians and tyrannosaurids. The pubis is also expanded near its contact with the ilium. The left and right pubic bones are not entirely fused to each other, they are separated along their midline by an oval-shaped hole.
The megaraptora was first made in 2010 based on Megaraptor. It included Australovenator, Rapator, and Orkoraptor. Then in 2015, recently a new megaraptoran was nicknamed Lightning Claw. However it was now considered to be a Rapator specimen. Recently in the year of 2016, a new specie of megaraptoran was found. It was known as Aoniraptor. Even more recently another new megaraptoran known as Murusraptor was described although it was discovered since 2000.
Megaraptora
Aoniraptor Fukuiraptor Siats (dinosaur) Aerosteon Australovenator Megaraptor Murusraptor Orkoraptor Rapator