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Megaraptor
Megaraptor (lit. 'large thief') is a genus of large theropod dinosaur, the type genus and namesake of the clade Megaraptora and family Megaraptoridae. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America, dating to the Turonian and Coniacian ages of the Late Cretaceous, roughly 90–88 million years ago. One species of Megaraptor, M. namunhuaiquii, has thus been named, known from seven partial or fragmentary skeletons, with only two including skull elements.
The type specimen of Megaraptor consists of a fragmentary assemblage of limb bones, discovered in 1996 by Argentine palaeontologist Fernando E. Novas. Believing that a large claw found at the site came from the animal's foot, he determined that it was probably a coelurosaur related to dromaeosaurs and troodontids, and named it accordingly. While Novas never stated that Megaraptor belonged to either family, contemporary depictions often portrayed it as a giant dromaeosaurid. The discovery of another specimen revealed that Megaraptor's large claw actually came from its hand, and it was surmised in 2004 to belong to a novel lineage predating the carnosaur–coelurosaur split. Subsequent analyses recovered Megaraptor and related genera (collectively known as megaraptorans) as relatives of the allosauroid Neovenator, though since the description of a relatively complete juvenile skull in 2014, it has been recovered primarily within Coelurosauria, and may have been a close relative of tyrannosaurs.
No complete skeletons of Megaraptor are known, so its anatomy has been pieced together over the years through only a few fragmentary specimens. It has been estimated that Megaraptor measured 8 m (26 ft) in length, and weighed around 1 t (2,200 lb). Its skull, the anatomy of which is known primarily from a juvenile specimen, was long, low, and slender, though in adults it was likely deeper and more robust, with smaller eye sockets and more robust frontal bones. Similar to tyrannosaurs, it had small, conical teeth at the front of its jaws, and longer, more curved teeth near the back, a condition known as heterodonty. Megaraptor had very large deltopectoral crests on its upper arm bones, and various other muscle attachment sites suggest that its arms were strong. The hand claws of Megaraptor were very long and strongly curved, with the claw of the first finger measuring 35 cm (14 in) in total length; the claw of the third finger was the smallest, only 6.5 cm (2.6 in) in length. Similar to dromaeosaurids and birds of prey, these claws may have been lengthened considerably by a sheath of keratin.
The depositional environment of the Portezuelo Formation was a fluvial (river) deposit, with a humid climate. Megaraptor would have shared its ecosystem with various other non-avian archosaurs, including the abelisaurid Elemgasem, the titanosaurian sauropod Futalogknosaurus, the unenlagiine theropod Unenlagia, and the azhdarchoid pterosaur Argentinadraco. It was initially suggested that Megaraptor may have used its hand claws to open carcasses, though a role in active predation is now generally favoured. Due to the relatively gracile construction of its skull compared to that of other theropods, Megaraptor, along with other megaraptorans such as Australovenator, may have relied on its large hand claws to grab prey items, pulling them towards its chest so that they could be dispatched by its jaws.
In January 1996, Argentine palaeontologist Fernando E. Novas recovered the fragmentary remains of a large theropod, consisting of a right ulna, a left manual phalanx (finger bone), part of a right metatarsal, and a very large ungual phalanx (a bone which supported a claw in life). The specimen was discovered in strata belonging to the Portezuelo Formation, part of the Río Neuquén Subgroup in Neuquén, northwestern Patagonia. The specimen, catalogued as MCF-PVPH 79, was transported to the Museo Carmen Funes, a palaeontological collection in Plaza Huincul. In December 1997, Novas presented a cast of the ungual, which he believed came from the second digit of the foot, to the Houston Museum of Natural Science. The next year, he described it in a paper published in the Journal of Vertebrate Paleontology. Believing that the new taxon was related in some capacity to dromaeosaurids and troodontids, (though noting that a more basal position was possible), Novas gave it the binomial name Megaraptor namunhuaiquii. The genus name derives from the Greek mega (large) and the Latin raptor (thief), while the species name derives from the Mapuche namun (foot) and huaiqui (lance). Though Novas never expressed a belief that M. namunhuaiquii was a dromaeosaurid, it was nevertheless depicted as such in contemporary palaeoart.
In 2004, a second Megaraptor specimen (MUCPv 341), was described in a paper helmed by Jorge O. Calvo. Consisting of a right ulna, radius and a complete manus (hand), found in association with the femur of the sauropod Futalogknosaurus, it demonstrated that the large ungual belonged to the first digit of the manus, as opposed to the second digit of the foot, and led its describers to suggest a position predating the coelurosaur–allosauroid split. In 2005, a third M. namunhuaiquii specimen (MUCPv 595), consisting of the partial skeleton of a juvenile with uncertain affinities, was discovered. It was described in 2014 by a team led by Juan D. Porfiri. The assignment of this specimen to M. namunhuaiquii has since been called into question, including by Porfiri himself. A paper published in 2025 by Maximilian Kellermann et al noted morphological inconsistencies between the juvenile and other, larger specimens referred to M. namunhuaiquii, and the presence of a structure on its caudal (tail) vertebrae which is also present in Maip and Murusraptor. Referral to a single genus, according to them, appeared to be driven largely by the fact that both specimens were found at the same locality. On the other hand, the differences observed may be the result of ontogenetic changes, the anatomical changes an animal undergoes as it matures. A fourth specimen (MUCPv 278), consisting of a humerus, was described in 2025. A fifth specimen assigned to M. namunhuaiquii (MUCPv 1353) is known, discovered in 2008. Consisting of assorted skull material and "a large part" of the postcranial skeleton, it has been described only in a thesis authored by Porfiri. That same thesis references two additional specimens, MUCPv 412 and MUCPv 413, which consist of parts of the ulna and a manual phalanx (finger bone).
South American megaraptorids were generally very large, exceeding 7 m (23 ft) in length and 1 t (1,000 kg) in mass. The holotype of Megaraptor was estimated by Fernando Novas to measure around 8 m (26 ft) in length. In 2010, Gregory S. Paul estimated its length at 8 m (26 ft), its weight at 1 t (2,200 lb). Porfiri et al., in their 2014 paper describing MUCPv 595, estimated the length of a mature specimen at 9–10 m (30–33 ft) based on the proportions of Allosaurus. In 2016, extrapolating instead from other megaraptorans, Asier Larramendi and Rubén Molina-Pérez estimated that M. namunhuaiquii had a body length of 8.3 m (27 ft), a hip height of 2.35 m (7.7 ft), and a body mass of 1.3 t (2,900 lb). MUCPv 595 has an estimated body length of 3 m (9.8 ft). While MUCPv 278 is known only from a humerus, that humerus, is roughly twice the size of the equivalent bone in the juvenile specimen, and one-third larger than that of Australovenator.
The skull of Megaraptor is known primarily from a single juvenile specimen, MUCPv 595, which preserves both premaxillae and maxillae, nasals, a left frontal, and a partial braincase, though some elements are known from MUCPv 1353. The skull was fairly gracile and weak compared to that of other theropods, possibly a consequence of the development of more powerful and mobile forelimbs and thus a decreased reliance on the skull for predation. The premaxilla is fairly small and bears several large foramina, as in many tyrannosauroids. The maxilla is long and subtriangular, and has a combination of coelurosaur traits, such as the lengthening of the anterior (front) maxillary ramus, and allosauroid traits, such as the straightness of the dorsal (upper) margin. At the same time, there are traits that match neither group, such as the overall morphology of the maxillary ramus. The nasals were paired and unfused, though this may be attributed to the juvenile nature of the known skull. Similarly, the nasal rugosities present in many other basal tetanurans are absent, though this may again be due to the specimen's age upon death. The frontal is quadrangular, with a wide supratemporal fossa, bound by a strong ridge which contacted that of the opposite frontal, very similar to the condition seen in tyrannosauroids and unlike that of allosauroids. The braincase, too, has a mosaic of coelurosaur (particularly tyrannosauroid) and allosauroid traits. This resembles the pattern seen in tyrannosauroids. Allesio Ciaffi et al., in 2025, used allometry to determine that the skull of a fully mature M. namunhuaiquii would likely have been deeper and more robust than that of MUCPv 595, and that the orbits (eye sockets) would have proportionally been smaller. They did, however, note the caveat that much of M. namunhuaiquii's postcranial skeleton (the elements posterior to the skull, or behind it) contradicts what might be assumed based on allometry alone, and that the same may apply to cranial elements. Based on allometric trends in Murusraptor and tyrannosaurids, it is possible that the frontal bones of megaraptorids such as M. namunhuaiquii would have become wider, deeper, and shorter with age.
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Megaraptor
Megaraptor (lit. 'large thief') is a genus of large theropod dinosaur, the type genus and namesake of the clade Megaraptora and family Megaraptoridae. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America, dating to the Turonian and Coniacian ages of the Late Cretaceous, roughly 90–88 million years ago. One species of Megaraptor, M. namunhuaiquii, has thus been named, known from seven partial or fragmentary skeletons, with only two including skull elements.
The type specimen of Megaraptor consists of a fragmentary assemblage of limb bones, discovered in 1996 by Argentine palaeontologist Fernando E. Novas. Believing that a large claw found at the site came from the animal's foot, he determined that it was probably a coelurosaur related to dromaeosaurs and troodontids, and named it accordingly. While Novas never stated that Megaraptor belonged to either family, contemporary depictions often portrayed it as a giant dromaeosaurid. The discovery of another specimen revealed that Megaraptor's large claw actually came from its hand, and it was surmised in 2004 to belong to a novel lineage predating the carnosaur–coelurosaur split. Subsequent analyses recovered Megaraptor and related genera (collectively known as megaraptorans) as relatives of the allosauroid Neovenator, though since the description of a relatively complete juvenile skull in 2014, it has been recovered primarily within Coelurosauria, and may have been a close relative of tyrannosaurs.
No complete skeletons of Megaraptor are known, so its anatomy has been pieced together over the years through only a few fragmentary specimens. It has been estimated that Megaraptor measured 8 m (26 ft) in length, and weighed around 1 t (2,200 lb). Its skull, the anatomy of which is known primarily from a juvenile specimen, was long, low, and slender, though in adults it was likely deeper and more robust, with smaller eye sockets and more robust frontal bones. Similar to tyrannosaurs, it had small, conical teeth at the front of its jaws, and longer, more curved teeth near the back, a condition known as heterodonty. Megaraptor had very large deltopectoral crests on its upper arm bones, and various other muscle attachment sites suggest that its arms were strong. The hand claws of Megaraptor were very long and strongly curved, with the claw of the first finger measuring 35 cm (14 in) in total length; the claw of the third finger was the smallest, only 6.5 cm (2.6 in) in length. Similar to dromaeosaurids and birds of prey, these claws may have been lengthened considerably by a sheath of keratin.
The depositional environment of the Portezuelo Formation was a fluvial (river) deposit, with a humid climate. Megaraptor would have shared its ecosystem with various other non-avian archosaurs, including the abelisaurid Elemgasem, the titanosaurian sauropod Futalogknosaurus, the unenlagiine theropod Unenlagia, and the azhdarchoid pterosaur Argentinadraco. It was initially suggested that Megaraptor may have used its hand claws to open carcasses, though a role in active predation is now generally favoured. Due to the relatively gracile construction of its skull compared to that of other theropods, Megaraptor, along with other megaraptorans such as Australovenator, may have relied on its large hand claws to grab prey items, pulling them towards its chest so that they could be dispatched by its jaws.
In January 1996, Argentine palaeontologist Fernando E. Novas recovered the fragmentary remains of a large theropod, consisting of a right ulna, a left manual phalanx (finger bone), part of a right metatarsal, and a very large ungual phalanx (a bone which supported a claw in life). The specimen was discovered in strata belonging to the Portezuelo Formation, part of the Río Neuquén Subgroup in Neuquén, northwestern Patagonia. The specimen, catalogued as MCF-PVPH 79, was transported to the Museo Carmen Funes, a palaeontological collection in Plaza Huincul. In December 1997, Novas presented a cast of the ungual, which he believed came from the second digit of the foot, to the Houston Museum of Natural Science. The next year, he described it in a paper published in the Journal of Vertebrate Paleontology. Believing that the new taxon was related in some capacity to dromaeosaurids and troodontids, (though noting that a more basal position was possible), Novas gave it the binomial name Megaraptor namunhuaiquii. The genus name derives from the Greek mega (large) and the Latin raptor (thief), while the species name derives from the Mapuche namun (foot) and huaiqui (lance). Though Novas never expressed a belief that M. namunhuaiquii was a dromaeosaurid, it was nevertheless depicted as such in contemporary palaeoart.
In 2004, a second Megaraptor specimen (MUCPv 341), was described in a paper helmed by Jorge O. Calvo. Consisting of a right ulna, radius and a complete manus (hand), found in association with the femur of the sauropod Futalogknosaurus, it demonstrated that the large ungual belonged to the first digit of the manus, as opposed to the second digit of the foot, and led its describers to suggest a position predating the coelurosaur–allosauroid split. In 2005, a third M. namunhuaiquii specimen (MUCPv 595), consisting of the partial skeleton of a juvenile with uncertain affinities, was discovered. It was described in 2014 by a team led by Juan D. Porfiri. The assignment of this specimen to M. namunhuaiquii has since been called into question, including by Porfiri himself. A paper published in 2025 by Maximilian Kellermann et al noted morphological inconsistencies between the juvenile and other, larger specimens referred to M. namunhuaiquii, and the presence of a structure on its caudal (tail) vertebrae which is also present in Maip and Murusraptor. Referral to a single genus, according to them, appeared to be driven largely by the fact that both specimens were found at the same locality. On the other hand, the differences observed may be the result of ontogenetic changes, the anatomical changes an animal undergoes as it matures. A fourth specimen (MUCPv 278), consisting of a humerus, was described in 2025. A fifth specimen assigned to M. namunhuaiquii (MUCPv 1353) is known, discovered in 2008. Consisting of assorted skull material and "a large part" of the postcranial skeleton, it has been described only in a thesis authored by Porfiri. That same thesis references two additional specimens, MUCPv 412 and MUCPv 413, which consist of parts of the ulna and a manual phalanx (finger bone).
South American megaraptorids were generally very large, exceeding 7 m (23 ft) in length and 1 t (1,000 kg) in mass. The holotype of Megaraptor was estimated by Fernando Novas to measure around 8 m (26 ft) in length. In 2010, Gregory S. Paul estimated its length at 8 m (26 ft), its weight at 1 t (2,200 lb). Porfiri et al., in their 2014 paper describing MUCPv 595, estimated the length of a mature specimen at 9–10 m (30–33 ft) based on the proportions of Allosaurus. In 2016, extrapolating instead from other megaraptorans, Asier Larramendi and Rubén Molina-Pérez estimated that M. namunhuaiquii had a body length of 8.3 m (27 ft), a hip height of 2.35 m (7.7 ft), and a body mass of 1.3 t (2,900 lb). MUCPv 595 has an estimated body length of 3 m (9.8 ft). While MUCPv 278 is known only from a humerus, that humerus, is roughly twice the size of the equivalent bone in the juvenile specimen, and one-third larger than that of Australovenator.
The skull of Megaraptor is known primarily from a single juvenile specimen, MUCPv 595, which preserves both premaxillae and maxillae, nasals, a left frontal, and a partial braincase, though some elements are known from MUCPv 1353. The skull was fairly gracile and weak compared to that of other theropods, possibly a consequence of the development of more powerful and mobile forelimbs and thus a decreased reliance on the skull for predation. The premaxilla is fairly small and bears several large foramina, as in many tyrannosauroids. The maxilla is long and subtriangular, and has a combination of coelurosaur traits, such as the lengthening of the anterior (front) maxillary ramus, and allosauroid traits, such as the straightness of the dorsal (upper) margin. At the same time, there are traits that match neither group, such as the overall morphology of the maxillary ramus. The nasals were paired and unfused, though this may be attributed to the juvenile nature of the known skull. Similarly, the nasal rugosities present in many other basal tetanurans are absent, though this may again be due to the specimen's age upon death. The frontal is quadrangular, with a wide supratemporal fossa, bound by a strong ridge which contacted that of the opposite frontal, very similar to the condition seen in tyrannosauroids and unlike that of allosauroids. The braincase, too, has a mosaic of coelurosaur (particularly tyrannosauroid) and allosauroid traits. This resembles the pattern seen in tyrannosauroids. Allesio Ciaffi et al., in 2025, used allometry to determine that the skull of a fully mature M. namunhuaiquii would likely have been deeper and more robust than that of MUCPv 595, and that the orbits (eye sockets) would have proportionally been smaller. They did, however, note the caveat that much of M. namunhuaiquii's postcranial skeleton (the elements posterior to the skull, or behind it) contradicts what might be assumed based on allometry alone, and that the same may apply to cranial elements. Based on allometric trends in Murusraptor and tyrannosaurids, it is possible that the frontal bones of megaraptorids such as M. namunhuaiquii would have become wider, deeper, and shorter with age.
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