Rugops Temporal range: Late Cretaceous, | |
---|---|
Restored skull | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Family: | † Abelisauridae |
Genus: | † Rugops Sereno et al. 2004 |
Species: | †R. primus |
Binomial name | |
†Rugops primus Sereno et al. 2004 | |
Rugops (meaning 'wrinkle face') is a monospecific genus of basal abelisaurid theropod dinosaur from Niger that lived during the Late Cretaceous period (Cenomanian stage, ~95 Ma) in what is now the Echkar Formation. The type and only species, Rugops primus, is known only from a partial skull. It was named and described in 2004 by Paul Sereno, Jeffery Wilson and Jack Conrad. Rugops has an estimated length of 4.4–5.3 metres (14–17 ft) and weight of 410 kilograms (900 lb). The top of its skull bears several pits which correlates with overlaying scale and the front of the snout would have had an armour-like dermis.
A skull pertaining to an abelisaurid was recovered during an expedition in 2000 led by Paul Sereno near In-Abangharit, Niger Republic. [1] [2] The specimen came from the Echkar Formation of the Tegama Group which dates to the Cenomanian stage of the Late Cretaceous period, 96 Ma. The formation has also yielded specimens pertaining to the carcharodontosaurid Carcharodontosaurus iguidensis , [3] the spinosaurid Spinosaurus , [1] an unnamed rebbachisaurid and titanosaur, [1] and the crocodylomorphs Fortignathus , [4] Laganosuchus and Kaprosuchus . [5] The specimen was described in 2004 by Paul Sereno, Jeffery Wilson and Jack Conrad. The holotype specimen, MNN IGU1, consists of a partial skull which lacks portions of the palate and skull roof. [1] The type specimen may represent a subadult individual based on its small size, the lack of fusion between the nasals and the presence of the fenestra between the prefrontal, frontal, postorbital and lacrimal bones. [6]
The generic name, Rugops, is derived from the Latin word "ruga" (wrinkle) and the Greek word "opsi" (face). The specific name is derived from the Latin word "primus" (first). Both the generic and specific name refer to Rugops as being one of the earliest abelisaurids with a textured skull. [1]
In 2005, a partial right maxilla of an abelisaurid was described from the Kem Kem Group of Morocco. The maxilla shares some similarities with Rugops such as with the morphology of the teeth, the shape of the alveolar, the rugose texture on the lateral sides, the straight border with the premaxilla, and the position of the palatal shelf. [7] However, the maxilla cannot be referred to Rugops as the diagnostic features of the genus are located on different parts of the skull. [8]
In 2010, Sereno gave Rugops an estimated length of 6 metres (20 ft) and weight of 750 kilograms (1,650 lb). [9] However, Grillo & Delcourt (2016) gave a lower estimate of 4.4 metres (14 ft) long while Molina-Pérez & Larramendi (2016) gave an estimate of 5.3 metres (17 ft) long and 410 kilograms (900 lb) in weight. [10] [11]
The skull length of Rugops was about 31.5 centimetres (12.4 in). [1] As in other abelisaurids, the skull of Rugops has an external surface that is textured, a dental arcade that is U-shaped, maxillary-jugal contact that is broad, the presence of a socket on the maxilla and alveoli that are subrectangular in shape. The orbital brow is present on the skull, although it is not fully formed. Many of the bones that make up the skull have slender proportions. In addition, the skull also has relatively thin nasals and skull fenestrae that are proportionally large. The upper surface of each nasal bone has a row of several depressions with grooves for vascular supply going into them. [1] A similar condition is seen in Carnotaurus , although the upper surface of the nasals is convex unlike Rugops, as it is concave. [6] Sereno et al. (2004) suggested that the depressions on the dorsal surface of each nasal anchored either sensory structures or soft tissues for display. [1] Delcourt (2018), however, interpreted that they correlate with overlying scales, as seen in extant reptiles such as crocodiles and lizards. The anterior-most snout has a papillate texture which indicates the presence of an armour-like dermis. The author suggested that, based on the type specimen probably being a subadult individual, the armour-like dermis may have reached a larger surface as it grew to which it developed a more papillate texture. Delcourt (2018) also proposed that the armour-like dermis may correlate with a low-motion headbutting behaviour, as seen in marine iguanas. [12]
A maxilla (NPSJB-PV247) from Patagonia shows similarities with Rugops as the pattern of external ornamentation is nearly identical and the internal details are also have a close similarity. [1] [13] In Rugops, the interdenticular sulci of the denticles, the presence of which might possible be a synapomorphic characteristic of Abelisauridae, is absent and has a higher dental formulae than in any other abelisaurid. [14] The nasal sculpturing of Rugops is similar to the ornamentation seen in Skorpiovenator as the surface of the nasals show hummocky-like rugosities and has grooves that lead into each foramen. However, unlike Skorpiovenator, Rugops lacks extra foramina on the skull roof that could represent homologues. The external morphology of the nasals are similar to that of Skorpiovenator as they share a similar foramina pattern. The ventral surface of the nasals have a series of foramina, which has been suggested to connect to an internal system. [15]
The describing authors indicated two distinguishing traits. Both of these are autapomorphies, unique derived characters. The skull roof has small fenestra that are present between the prefrontal, frontal, post-orbital and lacrimal. The dorsal surface of each nasal has a row of seven small depressions. [1]
Sereno et al. (2004) initially found Rugops to be the basalmost abelisaurid, [1] a position also recovered by various analyses by Egli et al. (2016), [16] Delcourt (2018), [12] Cerroni et al. (2020) [17] and Rolando et al. (2020). [18] However, Rugops has also been recovered as being more derived than Rahiolisaurus and/or Eoabelisaurus but more basal than other abelisaurids by Pol & Rauhut (2012), [19] Rauhut & Carrano (2016), [20] and Iori et al. (2021). [21] Other alternative positions include Rugops being more derived than Kryptops , Chenanisaurus and/or Spectrovenator as recovered by Sereno & Brusatte (2008), [22] Zaher et al. (2020), [23] Gianechini et al. (2021) [24] and Agnolín et al. (2022), [25] and within a polytomy with other abelisaurids such as Xenotarsosaurus , Tarascosaurus , Ilokelesia and Genusaurus which has been recovered by Tortosa et al. (2014), [26] Baiano et al. (2020) [27] and Salem et al. (2022). [28]
A phylogenetic analysis conducted by Zaher et al. (2020) is reproduced below. [23]
The results of an earlier analysis by Pol & Rauhut (2012) are reproduced below. [19]
Carnotaurus is a genus of theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 72 and 69 million years ago. The only species is Carnotaurus sastrei. Known from a single well-preserved skeleton, it is one of the best-understood theropods from the Southern Hemisphere. The skeleton, found in 1984, was uncovered in the Chubut Province of Argentina from rocks of the La Colonia Formation. Carnotaurus is a derived member of the Abelisauridae, a group of large theropods that occupied the large predatorial niche in the southern landmasses of Gondwana during the late Cretaceous. Within the Abelisauridae, the genus is often considered a member of the Brachyrostra, a clade of short-snouted forms restricted to South America.
Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with Ceratosaurus than with birds. The oldest known ceratosaur, Saltriovenator, dates to the earliest part of the Jurassic, around 199 million years ago. Ceratosauria includes three major clades: Ceratosauridae, Noasauridae, and Abelisauridae, found primarily in the Southern Hemisphere. Originally, Ceratosauria included the above dinosaurs plus the Late Triassic to Early Jurassic Coelophysoidea and Dilophosauridae, implying a much earlier divergence of ceratosaurs from other theropods. However, most recent studies have shown that coelophysoids and dilophosaurids do not form a natural group with other ceratosaurs, and are excluded from this group.
Abelisaurus is a genus of predatory abelisaurid theropod dinosaur alive during the Late Cretaceous Period (Campanian) of what is now South America. It was a bipedal carnivore that probably reached about 7.4 metres in length, although this is uncertain as it is known from only one partial skull.
Carcharodontosauridae is a group of carnivorous theropod dinosaurs. In 1931, Ernst Stromer named Carcharodontosauridae as a family, which, in modern paleontology, indicates a clade within Carnosauria. Carcharodontosaurids include some of the largest land predators ever known: Giganotosaurus, Mapusaurus, Carcharodontosaurus, and Tyrannotitan all rivaled Tyrannosaurus in size. Estimates give a maximum weight of 8–10 metric tons for the largest carcharodontosaurids, while the smallest carcharodontosaurids were estimated to have weighed at least 500 kilograms (1,100 lb).
Abelisauridae is a family of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indian subcontinent and the island of Madagascar. Isolated teeth were found in the Late Jurassic of Portugal, and the Late Cretaceous genera Tarascosaurus, Arcovenator and Caletodraco have been described in France. Abelisaurids possibly first appeared during the Jurassic period based on fossil records, and some genera survived until the end of the Mesozoic era, around 66 million years ago.
Aucasaurus is a genus of medium-sized abelisaurid theropod dinosaur from Argentina that lived during the Late Cretaceous of the Anacleto Formation. It was smaller than the related Carnotaurus, although more derived in some ways, such as its extremely reduced arms and almost total lack of fingers. The type skeleton is complete to the thirteenth caudal vertebra, and so is relatively well understood, and is the most complete abelisaurid yet described. However, the skull is damaged, causing some paleontologists to speculate that it was involved in a fight prior to death.
Deltadromeus is a genus of theropod dinosaur from the Aoufous Formation of Morocco.
Majungasaurus is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period, making it one of the last-known non-avian dinosaurs that went extinct during the Cretaceous–Paleogene extinction event. The genus contains a single species, Majungasaurus crenatissimus. This dinosaur is also called Majungatholus, a name which is considered a junior synonym of Majungasaurus.
Ekrixinatosaurus is a genus of abelisaurid theropod which lived approximately 100 to 97 million years ago during the Late Cretaceous period. Its fossils have been found in Argentina. Only one species is currently recognized, Ekrixinatosaurus novasi, from which the specific name honors of Dr. Fernando Novas for his contributions to the study of abelisaurid theropods, while the genus name refers to the dynamiting of the holotype specimen. It was a large abelisaur, measuring between 6.5 and 8 m in length and weighing 800 kg (1,800 lb).
Sigilmassasaurus is a controversial genus of spinosaurid dinosaur that lived approximately 100 to 94 million years ago during the Late Cretaceous Period in what is now northern Africa. Named in 1996 by Canadian paleontologist Dale Russell, it contains a single species, Sigilmassasaurus brevicollis. The identity of the genus has been debated by scientists, with some considering its fossils to represent material from the closely related species Spinosaurus aegyptiacus, while others have classified it as a separate taxon, forming the clade Spinosaurini with Spinosaurus as its sister taxon.
Spinostropheus is a genus of carnivorous neotheropod theropod dinosaur that lived in the Middle Jurassic period and has been found in the Tiouraren Formation, Niger. The type and only species is S. gautieri.
Skorpiovenator is a genus of abelisaurid theropod dinosaur from the Late Cretaceous Huincul Formation of Argentina. It is one of the most complete and informative abelisaurids yet known, described from a nearly complete and articulated skeleton.
Brachyrostra is a clade within the theropod dinosaur family Abelisauridae. It includes the famous genera Carnotaurus, Abelisaurus, Aucasaurus as well as their close relatives from the Cretaceous Period of Argentina and Brazil plus Caletodraco from France. The group was first proposed in an analysis conducted by Juan Canale and colleagues in 2008. They found that all South American abelisaurids described up to that point grouped together as a sub-clade of Abelisauridae, which they named based on the relatively unusual shape of their skulls. They defined the clade Brachyrostra as "all the abelisaurids more closely related to Carnotaurus sastrei than to Majungasaurus crenatissimus."
Bahariasauridae is a potential family of averostran theropods that might include a handful of African and South American genera, such as Aoniraptor, Bahariasaurus, Deltadromeus, and Gualicho. The placement of these theropods is controversial, with some studies placing them as basal ceratosaurs possibly related to Noasauridae, others classifying them as megaraptorans, basal neovenatorids, or basal coelurosaurs. There is also a possibility the group might not be monophyletic, as a monograph on the vertebrate diversity in the Kem Kem Beds published in 2020 found Bahariasaurus to be nomen dubium. In the same paper Deltadromeus is classified as an noasaurid, a result also recovered by some previous studies. A 2024 phylogenetic analysis found Aoniraptor, Bahariasaurus, Deltadromeus, and Gualicho to form a monophyletic clade as the sister taxon to Elaphrosaurus near the base of Ceratosauria.
Eoabelisaurus is a genus of abelisauroid or abelisaurid theropod dinosaur from the Lower Jurassic Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Argentina, South America. The generic name combines a Greek ἠώς, (eos), "dawn", with the name Abelisaurus, in reference to the fact it represents an early relative of the latter. Only one species is currently recognized, E. mefi; the specific name honours the MEF, the Museo Paleontológico "Egidio Feruglio", where discoverer Diego Pol is active. It is characterized by reduced forelimb proportions that show primitive characteristics of the Abelisauridae family.
Arcovenator is an extinct genus of abelisaurid theropod dinosaurs hailing from the Late Cretaceous of France and possibly Spain. The type and only described species is Arcovenator escotae.
This timeline of ceratosaur research is a chronological listing of events in the history of paleontology focused on the ceratosaurs, a group of relatively primitive, often horned, predatory theropod dinosaurs that became the apex predators of the southern hemisphere during the Late Cretaceous. The nature and taxonomic composition of the Ceratosauria has been controversial since the group was first distinguished in the late 19th century. In 1884 Othniel Charles Marsh described the new genus and species Ceratosaurus nasicornis from the Late Jurassic Morrison Formation of the western United States. He felt that it belonged in a new family that he called the Ceratosauridae. He created the new taxon Ceratosauria to include both the Ceratosauridae and the ostrich-like ornithomimids. The idea of the Ceratosauria was soon contested, however. Later that same decade both Lydekker and Marsh's hated rival Edward Drinker Cope argued that the taxon was invalid.
Tralkasaurus is a genus of abelisaurid dinosaur from the Huincul Formation from Río Negro Province in Argentina. The type and only species is Tralkasaurus cuyi, named in 2020 by Mauricio Cerroni and colleagues based on an incomplete skeleton. A medium-sized abelisaurid, Tralkasaurus exhibits a conflicting blend of characteristics found among the early-diverging abelisauroids with others that characterize the highly specialized clade Brachyrostra, and thus its position within the clade is poorly-resolved.
Kaikaifilusaurus is an extinct genus of rhynchocephalians in the family Sphenodontidae from the Late Cretaceous of South America. Fossils of the genus were found in Cenomanian sediments of the Candeleros Formation and Turonian layers of the Huincul Formation, both of the Neuquén Basin and the Albian strata of the Cerro Barcino Formation in the Cañadón Asfalto Basin, all in Patagonia, Argentina. The genus contains two species, K. minimus and the type species K. calvoi.
Meraxes is a genus of large carcharodontosaurid theropod dinosaur from the Late Cretaceous Huincul Formation of Patagonia, Argentina. The genus contains a single species, Meraxes gigas.
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