Rugops (meaning ‘wrinkle face’) is a
monospecificgenus of basal
abelisauridtheropoddinosaur 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 (14.4–17.4 ft) and weight of 410 kilograms (900 lbs). 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.
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]
Description
In 2010,
Gregory S. Paul gave Rugops an estimated length of 6 metres (19.7 ft) and weight of 750 kilograms (1,650 lbs).[9] However, Grillo & Delcourt (2016) gave a lower estimate of 4.4 metres (14.4 ft) long while Molina-Pérez & Larramendi (2016) gave an estimate of 5.3 metres (17.4 ft) long and 410 kilograms (900 lbs) in weight.[10][11]
Skull
The skull length of Rugops was about 31.5 centimetres (12.4 inches).[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.[13][1] 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]
Classification
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]
^Brusatte, S.L. and Sereno, P.C. (2007). "A new species of Carcharodontosaurus (dinosauria: theropoda) from the Cenomanian of Niger and a revision of the genus." Journal of Vertebrate Paleontology, 27(4): .
^Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 79
^Grillo, O. N.; Delcourt, R. (2016). "Allometry and body length of abelisauroid theropods: Pycnonemosaurus nevesi is the new king". Cretaceous Research. 69: 71–89.
doi:
10.1016/j.cretres.2016.09.001.
^Molina-Pérez & Larramendi 2016. Récords y curiosidades de los dinosaurios Terópodos y otros dinosauromorfos, Larousse. Barcelona, Spain p. 256
^C. Lamanna, Matthew; D. Martínez, Rubén; B. Smith, Joshua (2002). "A definitive abelisaurid theropod dinosaur from the early Late Cretaceous of Patagonia". Journal of Vertebrate Paleontology. 22 (1): 58–69.
doi:
10.1671/0272-4634(2002)022[0058:ADATDF]2.0.CO;2.
S2CID86153297.
^Smith, Joshua B. (2007). "Dental morphology and variation in Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar". In Sampson, Scott D.; Krause, David W. (eds.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Society of Vertebrate Paleontology Memoir 8. Vol. 27. pp. 103–126.
doi:
10.1671/0272-4634(2007)27[103:DMAVIM]2.0.CO;2.
S2CID85729335. {{
cite book}}: |journal= ignored (
help)
^Cerroni, M.A.; Motta, M.J.; Agnolín, F.L.; Aranciaga Rolando, A.M.; Brissón Egli, F.; Novas, F.E. (2020). "A new abelisaurid from the Huincul Formation (Cenomanian-Turonian; Upper Cretaceous) of Río Negro province, Argentina". Journal of South American Earth Sciences. 98: 102445.
Bibcode:
2020JSAES..9802445C.
doi:
10.1016/j.jsames.2019.102445.
S2CID213781725.
^W. M. Rauhut, Oliver; T. Carrano, Matthew (2016). "The theropod dinosaur Elaphrosaurus bambergi Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania". Zoological Journal of the Linnean Society. 178 (3): 546–610.
doi:
10.1111/zoj.12425.
^Iori, F.V.; de Araújo-Júnior, H.I.; Simionato Tavares, S.A.; da Silva Marinho, T.; Martinelli, A.G. (2021). "New theropod dinosaur from the late Cretaceous of Brazil improves abelisaurid diversity". Journal of South American Earth Sciences. 112: 103551.
Bibcode:
2021JSAES.11203551I.
doi:
10.1016/j.jsames.2021.103551.
ISSN0895-9811.
S2CID239682640.
^Tortosa, Thierry; Eric Buffetaut; Nicolas Vialle; Yves Dutour; Eric Turini; Gilles Cheylan (2014). "A new abelisaurid dinosaur from the Late Cretaceous of southern France: Palaeobiogeographical implications". Annales de Paléontologie. 100 (1): 63–86.
Bibcode:
2014AnPal.100...63T.
doi:
10.1016/j.annpal.2013.10.003.
^Mattia Baiano; Rodolfo Coria; Andrea Cau (2020). "A new abelisauroid (Dinosauria: Theropoda) from the Huincul formation (lower upper Cretaceous, Neuquén Basin) of Patagonia, Argentina". Cretaceous Research. 110: 104408.
Bibcode:
2020CrRes.11004408B.
doi:
10.1016/j.cretres.2020.104408.
S2CID214118853.