| Torvosaurus | |
|---|---|
 | |
| MountedT. tanneri skeletal reconstruction,Museum of Ancient Life | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Megalosauridae |
| Subfamily: | †Megalosaurinae |
| Genus: | †Torvosaurus Galton &Jensen,1979 |
| Type species | |
| †Torvosaurus tanneri Galton & Jensen, 1979 | |
| Other species | |
| Synonyms | |
| |
Torvosaurus (/ˌtɔːrvoʊˈsɔːrəs/) is agenus of largemegalosaurinetheropoddinosaur that lived approximately 165 to 148million years ago during theCallovian toTithonian ages of the lateMiddle andLate Jurassic period in what is nowColorado,Portugal,Germany, and possiblyEngland,Spain,Tanzania, andUruguay. It contains two currently recognizedspecies,Torvosaurus tanneri andTorvosaurus gurneyi, plus a third unnamed species from Germany.[1]
In 1979, thetype speciesTorvosaurus tanneri was named. Measuring around 9 meters (30 ft) long and weighing approximately 2–2.4 metric tons (2.2–2.6 short tons),T. tanneri was among the largest terrestrialcarnivores in North America during the Late Jurassic. Specimens ofTorvosaurus gurneyi were measured up to 10 meters (33 ft) in length and 4–5 metric tons (4.4–5.5 short tons) in body mass,[2] suggesting that it was much larger thanT. tanneri and was the largest terrestrial carnivore in Europe during the Late Jurassic. Based on bone morphology,Torvosaurus is thought to have had very powerful short arms.
Fossilized remains ofTorvosaurus have been found inNorth America,Portugal,Germany, and possibly inEngland,Spain,Tanzania, andUruguay. The first discovered remains referable toTorvosaurus were discovered in 1899 byElmer Riggs in the "Freeze-out Hills" of southeasternWyoming, 18 kilometers (11 mi) northwest ofMedicine Bow. The material consisted of part of the left foot and right hand and they were taken to theField Museum of Natural History inChicago, where they were stored until being re-discovered around 2010. The specimen was assigned toTorvosaurus tanneri after being described in 2014.[3]
More remains of a largetheropod that is now believed to have beenTorvosaurus were discovered in theTendaguru Formation ofTanzania and was named "Megalosaurus"ingens byWerner Janensch in 1920, based on the specimen MB R 1050, a 12-centimeter-long (4.7 in) tooth fromGerman East Africa (now Tanzania).[4] It was eventually reclassified as a probable member ofCarcharodontosauridae before being reclassified as a probable member of theTorvosaurus genus in 2020.[5] Although it was only referred to asTorvosaurus sp., one commentator has noted it could potentially be calledTorvosaurus ingens.[6][7] Sotoet al. described teeth of a member of the genusTorvosaurus from theTacuarembó Formation ofUruguay. The authors noted that some of the specimens of "Megalosaurus" ingens figured byWerner Janensch share the features of the Uruguayan material and stated that the materials from Tanzania and Uruguay may represent the same taxon, due to geographical proximity, but ultimately concluded that, based on only teeth, they do not share any derived characteristics to distinguish them from the described species of the genus,T. tanneri andT. gurneyi.[5][8] However, Rauhutet al. consider the teeth to be undiagnostic, being coherent in size and shape with a variety of other theropods (including carcharodontosaurids), thus considering their attribution to the genus to be problematic.[1]
In 1971, Vivian Jones ofDelta, Colorado, in the Calico Gulch Quarry inMoffat County, discovered a single gigantic thumb claw of a theropod. This was shown toJames Alvin Jensen, a collector who was working forBrigham Young University. In an effort to discover comparable fossils, Vivian's husband Daniel Eddie Jones directed Jensen to theDry Mesa Quarry, where abundant gigantic theropod bones, together withSupersaurus remains, proved present in rocks of theMorrison Formation. From 1972 onward, the site was excavated by Jensen and Kenneth Stadtman. Thetype speciesTorvosaurus tanneri was named and described in1979 byPeter Malcolm Galton and Jensen.[9] The genus nameTorvosaurus derives from theLatin wordtorvus, meaning "savage", and theGreek wordsauros (σαυρος), meaning "lizard".[10] Thespecific nametanneri comes from the, first counselor in theFirst Presidency ofthe Church of Jesus Christ of Latter-day Saints,Nathan Eldon Tanner.
In 1985, Jensen could report a considerable amount of additional material, among it being the first skull elements.[11] The fossils from Colorado were further described byBrooks Britt in 1991.[12] Theholotype, BYU 2002, originally consisted of upper and lower arm bones. Theparatypes included some back bones, hip bones, and hand bones.[9] When the material described in 1985 is added, the main missing elements are the shoulder girdle and the thighbone.[12] The original thumb claw, specimen BYUVP 2020, was only provisionally referred, as it had been found in a site 195 kilometers (121 mi) away from the Dry Mesa Quarry.[9] The holotype and paratypes represented at least three individuals, these being two adults and a juvenile.[12] In 1991, Britt concluded that there was no proof that the front limbs of the holotype were associated and chose the left humerus as thelectotype.[12] Several single bones and teeth found in other American sites have been referred toTorvosaurus.[12]
In 1992, fossils of a large theropod found atComo Bluff inWyoming contained skull, shoulder girdle, pelvic, and rib elements. They were named byRobert T. Bakkeret al. as the speciesEdmarka rex. Bakkeret al were impressed with the size ofEdmarka, noting that it "would rivalT. rex in total length," and viewing this approximate size as "a natural ceiling for dinosaurian meat-eaters."[13] This was often considered ajunior synonym ofTorvosaurus,[14] but a detailed analysis has not been carried out yet.[15] The same site has rendered comparable remains for which thenomen nudumBrontoraptor has been used.[16][17] Most researchers now regard both specimens as belonging toTorvosaurus tanneri.[2] However,Edmarka rex andBrontoraptor require reclassification to determine whether or not they actually belong toT. tanneri, as all the specimens described prior to their discovery indicate that they reached their adult size and both incomplete specimens lack detailed osteological descriptions.[18]
In 2012, a still undescribed, 55% complete specimen was discovered in Colorado in the Skull Creek Quarry, which is an exposure of the Morrison Formation. The specimen, nicknamed "Elvis", included the pelvic, spine, and hind limb bones, a complete, associated backbone, as well as cranial elements. It is the most complete specimen ofTorvosaurus found to date.[19] A mounted skeleton of the specimen, with missing parts reconstructed with casts from otherTorvosaurus specimens, is currently on display in the Museum of Natural History & Science in Cincinnati.[19][20]
In 2000, material from Portugal was referred to aTorvosaurus sp. byOctávio Mateus andMiguel Telles Antunes.[21] In 2006, fossils from the PortugueseLourinhã Formation were referred toTorvosaurus tanneri.[22] In 2012, however,Matthew Carranoet al. concluded that this material could not be more precisely determined than aTorvosaurus sp.[23] In 2013 and 2014, eggs with and without embryos were reported from Portugal and referred toTorvosaurus.[24][25] The species from Portugal was namedT. gurneyi in honor ofJames Gurney in 2014, the creator of theDinotopia series of books. It is the largest named theropod known from Europe, although an isolated anterior caudal vertebra from theVega Formation inSpain, which may belong toTorvosaurus or a closely related taxon, is about 15% larger than the one found onT. gurneyi.[2][26] It was the morphological distinctiveness of the holotype maxilla ML1100 that led to the naming of the Portuguese species.[2] In 2017, a set of Portuguese cranial material assigned toTorvosaurus was described, including a specimen interpreted as belonging to the same individual as the holotype ofTorvosaurus gurneyi.[27]
In 2020, Sotoet al. described FC-DPV 2971, a tooth from Uruguay, as belonging to a new unnamed species ofTorvosaurus.[5] They also assignedMegalosaurus/Ceratosaurus ingens (specimen MB R 1050) from Tanzania toTorvosaurus.[5] Also in 2020, a fragmentary maxilla referable toTorvosaurus was described from the middleCallovianOrnatenton Formation of Germany. This is the oldest record of the genus and suggests that megalosaurines originated in Europe, or at least that Europe was a biogeographical turntable for them from the Middle to the early Late Jurassic. Other possibleTorvosaurus instances in Europe include fragmentary remains from theKimmeridge Clay of England that possibly belong to the genus.[1] These consist of a tibia (OUMNH J.29886) and a maxilla fragment that were collected separately from each other.[23]
Torvosaurus was a very large and robust predatory dinosaur.T. tanneri was initially described as 10 metres (33 ft) long,[9] but a detailed osteological description has revised its length estimate to 9 metres (30 ft).[12]T. gurneyi was initially estimated around 11 metres (36 ft) long,[22] but its body length estimate was revised to 10 metres (33 ft) in its specific description.[2] Claims have been made indicating even larger sizes for the American speciesT. tanneri, with estimates of up to 12 m (39 ft) in length and more than 4 t (4.4 short tons) based on incomplete remains ofEdmarka rex and "Brontoraptor".[28][29] However,Edmarka rex and "Brontoraptor" lack detailed analyses to verify whether or not they actually belong toT. tanneri.[18]T. tanneri is estimated to have weighed approximately 2–2.4 metric tons (2.2–2.6 short tons),[30][31][32][33] whileT. gurneyi is estimated to have weighed 4–5 metric tons (4.4–5.5 short tons).[2]
Among the differentiating features originally recognized betweenT. gurneyi andT. tanneri are the number of teeth, alongside the size and shape of the mouth. While the upper jaw ofT. tanneri has more than 11 teeth, that ofT. gurneyi has less.[2] However, later examination of a new right maxilla, probably belonging to the same individual as the holotype ofT. gurneyi, has determined that, while the two species can be distinguished based on the morphology of the maxillary medial wall and interdental plates, the supposedly lower number of maxillary teeth in the Portuguese form may be an artifact of preservation, since it is not possible to know the exact number of teeth in the complete maxilla at the moment.[27]The material from Germany is further distinguished by the other two species by a temporal difference of c. 10 Ma and a few morphological differences which indicate that it was the third species outside a sister taxon relationship betweenT. tanneri andT. gurneyi. The material is only 10% smaller than the maxilla ofT. tanneri, although the ontogenetic stage of the specimen is unknown. This indicates that derived megalosaurines were already among the largest terrestrial predators of the late Middle Jurassic, with only a moderate increase in size in the genus by the Late Jurassic.[1]
Torvosaurus had an elongated, narrow snout, with a kink in its profile just above the large nostrils. The frontmost snout bone, thepremaxilla, bore three rather flat teeth oriented somewhat outwards with the front edge of the teeth crown overlapping the outer side of the rear edge of the preceding crown. Themaxilla was tall and bore at least eleven rather long teeth. Theantorbital fenestra was relatively short. Thelacrimal bone had a distinctive lacrimal horn on top. Its lower end was broad in side view. The eye socket was tall with a pointed lower end. Thejugal was long and transversely thin. The lower front side of thequadrate bone was hollowed out by a tear-shaped depression, the contact surface with thequadratojugal. Both the neck vertebrae and the front dorsal vertebrae had relatively flexible ball-in-socket joints. The balls on the front side of the vertebral centra had a wide rim, a condition by Britt likened to aDerby hat. The tail base was stiffened in the vertical plane by high and in side view wide neural spines. The whole of the arm was very strong, but somewhat short. Whether the thumb claw was especially enlarged is uncertain. In the pelvis, theilium resembled that ofMegalosaurus and had a tall, short, front blade and a longer pointed rear blade. The pelvis as a whole was massively built, with the bone skirts between thepubic bones and theischia contacting each other and forming a vaulted closed underside.[12]
When first described in 1979 by Galton and Jensen,[9]Torvosaurus was classified as amegalosaurid, which is the current consensus.[14] It was later assigned toCarnosauria byRalph Molnaret al. in 1990,[34] then to a basal position inSpinosauroidea byOliver Walter Mischa Rauhut in 2003,[35] and to a very basal position inTetanurae byThomas Holtz in 1994.[36] All these assignments are not supported by present phylogenetic analysis.[14] In 1985, Jensen assignedTorvosaurus to a family of its own,Torvosauridae.[11] Despite support for this concept byPaul Sereno[37] and Mateus,[22] it seems redundant becauseTorvosaurus is closely related to, and perhaps thesister species of, the earlierMegalosaurus withinMegalosaurinae.[14] However, Torvosauridae may be used as an alternative name for Megalosauridae ifMegalosaurus is considered an indeterminablenomen dubium.[38] Though a close relative ofMegalosaurus,Torvosaurus is seemingly more advanced, or apomorphic.Torvosaurus's largerclade,Megalosauridae, is most commonly held as abasal branch ofTetanurae, considered to be less derived thancarnosaurs orcoelurosaurs and likely related to thespinosaurids.[14]
The following is acladogram based on the phylogenetic analysis conducted by Carrano, Benson, and Sampson (2012) showing the relationships ofTorvosaurus:[14]
According to Carranoet al. (2012),Torvosaurus can be distinguished based on the following characteristics:[39]
The study of fossilized embryos ofTorvosaurus provides researchers with information about the transformation of the embryo over time, the different developmental pathways present in dinosaur lineages, dinosaur reproductive behavior, and dinosaur parental care.[41][42][43] In 2013, Araújoet al. announced the discovery of specimen ML1188, a clutch of crushed dinosaur eggs and embryonic material attributed toTorvosaurus.[24] This discovery further supports the hypothesis that large theropods were oviparous, meaning that they laid eggs and hence that embryonic development occurred outside the body of female dinosaurs. This discovery was made in 2005 by the Dutch amateur fossil-hunter Aart Walen at theLourinhã Formation in Western Portugal in fluvial overbank sediments that are considered to be from the Tithonian age of theJurassic, approximately 152 to 145 million years ago. This discovery is paleontologically significant for a number of reasons: (a) these are the most primitive dinosaur embryos known; (b) these are the only basal theropod embryos known; (c) fossilized eggs and embryos are rarely found together; (d) it represents the first evidence of a one-layered eggshell for theropod dinosaurs; and (e) it allows researchers to link a new eggshell morphology to the osteology of a particular group of theropod dinosaurs.[24] The specimen is housed at theMuseu da Lourinhã in Portugal. As the eggs were abandoned due to unknown circumstances, it is not known ifTorvosaurus provided parental care to its eggs and young or abandoned them shortly after laying.[44] However, the eggshells are highly porous, allowing efficient gaseous exchange between the external and internal media, thus indicating the eggs were buried for incubation within substrate in a manner similar to modern seaturtles. This is also corroborated by the undisturbed taphonomic setting and low-energy geological context.[24]
All documentedTorvosaurus specimens from theMorrison Formation are from similarly sized, likely adult individuals and the lack of immature individuals may be explained by many factors, none of which are mutually exclusive. For one thing, the formation is known to preserve large vertebrates better than smaller ones. Immature individuals may also have occupied a different ecological niche from adults in habitats where their remains were likely to preserve as fossils and they may have been the prey of choice of larger predators as well.Torvosaurus may also have experienced Type B1 population survivorship, as has been found in other dinosaurs, with mortality increasing after sexual maturity was achieved, leading to an abundance of mature individuals in the fossil record. A final possibility is that immatureTorvosaurus remains could be misidentified due to having different proportions compared to the very large and robust adults.[3]
Thetype specimen ofTorvosaurus tanneri, BYU 2002, was recovered in theDry Mesa Quarry of the Brushy Basin Member of theMorrison Formation in Montrose County, Colorado. The specimen was collected by James A. Jensen and Kenneth Stadtman in 1972 in medium-grained, coarse sandstone that was deposited during theTithonian andKimmeridgian ages of theJurassic, approximately 153 to 148 million years ago.[45] This specimen is housed in the collection ofBrigham Young University inProvo, Utah.
Studies suggest that thepaleoenvironment of this section of the Morrison Formation included rivers that flowed from the west into a basin that contained a giant, saline alkaline lake and there were extensive wetlands in the vicinity. The Dry Mesa Dinosaur Quarry of western Colorado yields one of the most diverse Upper Jurassic vertebrate assemblages in the world.[46] The Dry Mesa Quarry has produced the remains of thesauropodsApatosaurus,Brachiosaurus,Diplodocus,Barosaurus,Supersaurus, andCamarasaurus, theiguanodontsCamptosaurus andDryosaurus, and thetheropodsAllosaurus,Tanycolagreus,Koparion,Stokesosaurus,Ceratosaurus, andOrnitholestes, as well asOthnielosaurus,Gargoyleosaurus, andStegosaurus.[47]
The flora of the period has been revealed by fossils ofgreen algae,fungi,mosses,horsetails,ferns,cycads,ginkgoes, and several families ofconifers. Other animal fossils discovered includebivalves,snails,ray-finned fishes,frogs,salamanders,amphibians,turtles,sphenodonts,lizards, terrestrial (likeHoplosuchus) and aquaticcrocodylomorphs,cotylosaurs, several species ofpterosaurs, likeHarpactognathus, and earlymammals, such asmultituberculates,symmetrodonts, andtriconodonts.[47]
The Ornatenton Formation is a Callovian aged shallow marine deposit, within the formationTorvosaurus wassympatric with the closely related and also largeWiehenvenator. The Lourinhã Formation is Kimmeridgian–Tithonian in age. The environment is coastal and therefore has a strong marine influence. Its flora and fauna are very similar to that of the Morrison.Torvosaurus appears to be the top predator here. It lived alongside the European species ofAllosaurus (A. europaeus),Ceratosaurus,Stegosaurus, and presumablyCamptosaurus. The theropodLourinhanosaurus also stalked the area.Lusotitan was the largest sauropod in the region, while the diplodocidsDinheirosaurus andLourinhasaurus were also present.Dacentrurus andMiragaia were both stegosaurs, whileDracopelta was anankylosaurian.Draconyx was an iguanodontid related toCamptosaurus. Due to the marine nature of the Lourinhã Formation, sharks,plesiochelyid turtles, andteleosaurid crocodyliforms are also present.[48]
The small-scale trough and ripple cross-bedded fine-grained sandstone at the base of the Upper Dinosaur Member of theTendaguru Formation, of which possibleTorvosaurus material is known from, is interpreted as tidal flat deposits. Stagnant water bodies, such as small lakes and ponds, were present and a freshwater depositional environment close to the sea was also probably present.
The possible unnamedTorvosaurus species from the Tendaguru Formation would have shared its habitat with many species ofsauropods, such asAustralodocus,Dicraeosaurus,Giraffatitan,Janenschia,Tornieria,Wamweracaudia, three unnamed species ofdiplodocine sauropods, an unnamed species offlagellicaudatan, and the "Archbishop". The theropods it coexisted with wereAllosaurus tendagurensis,Ceratosaurus roechlingi,Elaphrosaurus,Labrosaurus stechowi,Ostafrikasaurus,Veterupristisaurus (of which it would have possibly competed with to be top predator), a possibleabelisauroid, and an indeterminatemegalosauroid, while theornithischians it coexisted with wereDysalotosaurus andKentrosaurus. As far as pterosaurs are concerned, it coexisted withTendaguripterus, an indeterminatearchaeopterodactyloid, an indeterminateazhdarchid, two indeterminatedsungaripteroids, an indeterminaterhamphorynchoid, and an indeterminate pterosaur of unknown classification. Due to the coastal environment of the Tendaguru Formation,crocodyliformes, such asBernissartia,amphibians, including an unnamedlissamphibian, andsharks are also present.[49]
Within South America, possibleTorvosaurus remains are only present within theTacuarembó Formation of Uruguay. Because the formation was laid down influvial tolacustrinesandstones,siltstones, andmudstones, this indicates that the environment of the formation would have been dominated byrivers,streams, andlakes.
If present,Torvosaurus would probably have been theapex predator in the Tacuarembó Formation, although it may have been rivalled bycf.Ceratosaurus.[50] It shared its habitat with two unnamedtheropods, an unnamedcoelurosaur, an unnamedsauropod known solely from footprints, an unnamedornithopod also known from footprints, an indeterminatemesoeucrocodylian, an indeterminateturtle species that lived alongside the named turtle speciesTacuarembemys kusterae, and the possiblepholidosaurMeridiosaurus vallisparadisi.Fish, such asArganodus tiguidiensis,Asiatoceratodus cf. tiguidensis,Neoceratodus africanus, andPriohybodus arambourgi, andbivalves, such asDiplodon, are also present.[51][52]
Torvosaurus coexisted with other large theropods such asAllosaurus andCeratosaurus in the United States and Portugal, possiblyVeterupristisaurus in Tanzania, and possiblycf.Ceratosaurus (?) in Uruguay. The three, possibly four, species appear to have had differentecological niches, based on anatomy and the location of fossils.Torvosaurus andCeratosaurus may have preferred to be active around waterways and had lower, more sinuous, bodies that would have given them an advantage in forest and underbrush terrains, whereasAllosaurus had shorter bodies, longer legs, were faster and less maneuverable, and seem to have preferred dry floodplains.[53] Also, Rauhut et al. (2016) proposed that allosaurids and megalosaurids would have had different environmental preferences, the former being more common in inland areas, while the latter being dominant in marine and coastal environments.[54]
On the other hand, the majority ofTorvosaurus remains from the Morrison Formation have been found in localities preserving multiple taxa, includingAllosaurus, withTorvosaurus itself being a minor component of the bonebeds. This pattern has been interpreted as indicative ofTorvosaurus sharing habitats with other predators, most notablyAllosaurus, but at much lower abundances.[3] The three may also have had different dietary preferences, withAllosaurus being more suited for bone slicing (thanks to its short and stout serrated teeth, deep and narrow skull, and powerful dorsoventral movement capacity of the neck), whileCeratosaurus, with its long and blade-like teeth and relatively straight neck, would have probably been incapable of doing so, instead concentrating on the deepest organs of a carcass. While probably capable of some bone consumption,Torvosaurus, with its large skull and teeth and large, powerful, and lithe body may have been specialized in opening up and dismembering exceptionally large sauropod carcasses. This would have allowed smaller theropods, likeAllosaurus, better access in a possiblecommensalism relationship.[55]
Allosaurus was itself a potential food item to other carnivores, as illustrated by anAllosauruspubic foot marked by the teeth of another theropod, probablyCeratosaurus orTorvosaurus. The location of the bone in the body (along the bottom margin of the torso and partially shielded by the legs) and the fact that it was among the most massive in the skeleton indicates that theAllosaurus was being scavenged.[56]
Bite marks onAllosaurus andMymoorapelta remains were found among other bones with feeding traces in the Upper Jurassic Mygatt-Moore Quarry. Unlike the others, these have left striations that, when measured to determine denticle width, produced tooth and body size extrapolations greater than any known specimen ofAllosaurus orCeratosaurus, the two large predators known for osteological remains from the quarry. The extrapolations are instead coherent, either with an unusually large specimen ofAllosaurus or a separate large taxon likeTorvosaurus which is not known from the quarry. The result either increases the known diversity of the site based on ichnological evidence alone or represents powerful evidence of cannibalism inAllosaurus. Based on the position and nutrient value associated with the various skeletal elements with bite marks, it is predicted that whileMymoorapelta was either predated upon or scavenged shortly after death,Allosaurus was scavenged some time after death.[57]
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