Arcovenator
| Arcovenator Temporal range: Late Cretaceous,
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| Genus: | Arcovenator Tortosa et al., 2013
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Arcovenator ("Arc hunter") is a genus of abelisaurid theropod dinosaur hailing from the Late Cretaceous of France.[1] The type and only described species is Arcovenator escotae.[1]
Description
Though shallower, the nearly complete braincase of Arcovenator is otherwise of similar size to those of Majungasaurus and Carnotaurus, implying an animal about 5-6 m long.[1] It has moderately thick frontals, as does Aucasaurus, thus less so than Rajasaurus, though more than Rugops, resulting in a slight dome.[1] The parietal which borders the supratemporal fenestrae medially forms ridges on their respective anteromedial margins which as they approach the parietal eminence fuse into a sagital crest.[1] The postorbital is intermediate between the plesiomorphic condition of Eoabelisaurus and the derived one of Carnotaurus.[1] It has a thick rough-surfaced process dorsal to the eye socket that extends to the lacrimal, forming a bony brow ridge.[1] Generally the external bone ornamentation is more subdued than that of Majungasaurus.[1] The tall teeth (3-5.5 cm) have denticles on the apical portion of the mesial carina and along the length of the distal one, with varying density.[1]
The caudal vertebrae of A. escotae are remarkably similar to those of Majungasaurus, though more dorso-ventrally compressed.[1] The centra possess amphicoelous articulations with the pertinent facets of an intermediate nature between the circular ones of Ilokelesia and those of the elliptical persuasion in Rajasaurus and have neither pneumatic recesses nor accessory hyposphene-hypantrum articulations.[1] The transverse processes of the neural arches aren't as inclined as in Brachyrostra.[1]
The cnemial crest of Arcovenator's the slender 51-cm tibia is well developed as is characteristic of abelisauroids.[1] It has a proximal lateral condyle more prominent than the medial one, a noticeable distal longitudinal ridge and tapered malleoli.[1] The nearly half-meter-long fibula possesses the typical anatomical characters of ceratosaurs.[1]
Classification and systematics
| Abridgement of cladogram presented in Tortosa et al., 2013[1] | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Arcovenator is a theropod genus nested within the clade Abelisauridae,[1] which in Linnaean taxonomy has the rank of family.[2] This taxonomical group has as close relatives noasaurids within Abelisauroidea.[1][3] The latter in turn along with Limusaurus and Ceratosaurus nests within Ceratosauria.[1][4]
Distinguishing characters of abelisaurids are their short, tall skulls with extensively sculptured external surfaces, the drastically reduced forelimbs, and the stout hindlimbs.[5]
As with many dinosaur clades, the structure of the phylogenetic tree of Abelisauridae and which genus pertains to which subgroup are in a state of flux as more data is obtained from both new fossils and applying new analytic techniques.[3][5][6] Arcovenator escotae, being the most complete and informative find since Genusaurus as far as French abelisaurids are concerned, suscitates readily the parallel interests of attempting to determine its position in relation to other genera, and ascertaining what its suite of characters resolves further of the relatedness between them.[1]
Thus Thierry Tortosa and colleagues conducted a phylogenetic analysis, which is summarized in the cladogram to the right and is based, in part, on previously published works including both the newly discovered fossil remains and other described but unnamed French abelisaurs.[1]
The study generally agrees with previous results, namely a relatively recent one obtained both by Matthew Carrano & Scott Sampson (2008)[7] and Diego Pol & Oliver W. M. Rauhut (2012)[4] of a clade that includes at least Majungasaurus, Indosaurus and Rajasaurus, which in the more recent analysis includes Arcovenator.[1] Tortosa et al. name this well-supported clade Majungasaurinae, ranking it as subfamily and defining it to contain all abelisaurids more closely related to Majungasaurus than to Carnotaurus.[1] The members of this taxonomical group have various cranial characters in common including an elongated antorbital fenestra, and a parietal with a sagittal crest that widens anteriorly into a triangular surface.[1] Also of note is that, in partial agreement with some analyses, the more fragmentary French ceratosaur remains are placed within Abelisauridae, and contrary to others, Abelisaurus is recovered as a carnotaurin.[1]
There are also insights into the paleobiogeography of abelisauroids: just presence of them in the so-called European Archipelago[8] confounds hypotheses that only consider the continents derived from the breakup of Mesozoic Gondwana.[1] Two lineages of European abelisaurs are discerned: a basal one, the small Albian Genusaurus with the African Kryptops as a likely close relative, and a derived one, the larger Campanian Arcovenator allied with the Madagascan Majungasaurus and the Indian Rajasaurus in Majungasaurinae.[1] As the inferred character distributions obtained through the phylogenetic analysis make it unlikely that these lineages are more closely related to each other than to other abelisaurids, this suggests a more complicated series of events regarding their biogeography with vicariance applicable to the older one and oceanic dispersal being likelier for the more recent one.[1] These results lend support to the proposed role of Africa as a hub for faunal movements between Europe and India or Madagascar[9] and isolation of South American abelisaurids.[1][7]
Discovery and naming
The fossil remains of A. escotae were found near Pourrières, Var department, Provence-Alpes-Côte d'Azur region,[10] during preventive paleontological and archaeological prospection activities before construction took place on the stretch of the A8 motorway between Châteauneuf-le-Rouge and Saint Maximin.[11][12][1] The pertinent late Campanian strata (72 to 76 million years ago)[13][14][15] of the Lower Argiles Rutilantes Formation are located in the Aix-en-Provence Basin of southeastern France.[1] The holotype of Arcovenator escotae is made up of a fragmentary skull with teeth and associated lower leg bones and caudal vertebra found in a single stratum of fluvial sandstone.[1] Caudal vertebra and teeth found close both in distance and depth were also referred to the species.[1]
The genus name Arcovenator derives from the river Arc as the locality is set within its basin and the Latin word for 'hunter', venator.[1] The specific epithet 'escotae' honors Escota, a motorway concession company,[16] which since 2006 has provided the necessary funds to excavate the locality.[1]
Paleoecology
Arcovenator escotae lived in the Ibero-Armorican island,[1] a relatively large landmass formed by what are now parts of France, Spain and Portugal.[8] The compressional subsidence basin of Aix-en-Provence was a low-relief endorheic affair located at a paleolatitude of 35° N, and had its borders to north and south in the form of limestone highlands, respectively the Sainte Victoire and Etoile massifs, and to the east as the Maure Mountains.[13] The sediment from these sources flowed along rivers into a perennial lake originating interbedded lacustrine, alluvial and fluvial sediments at the time of Arcovenator, when the climate was warm, subhumid with marked seasons.[13] The fossil remains were found in one of the formation's various levels of fluvial sandstone,[1] characteristic of a river's mouth or when it overflows its banks,[13] along with hybodonts, the turtles Foxemys and Solemys, the crocodylomorphs Musturzabalsuchus and Ischyrochampsa, azhdarchid pterosaurs, titanosaurian sauropods, the ornithopod Rhabdodon and nodosaurids.[1] The abundance of fragmentary remains of medium-sized abelisaurs, especially teeth in this and other localities of the region show that these animals would have been relatively common in the landscape.[1]
References
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am Tortosa, Thierry (2013). "A new abelisaurid dinosaur from the Late Cretaceous of southern France: Palaeobiogeographical implications". Annales de Paléontologie (In press). doi:10.1016/j.annpal.2013.10.003. Retrieved 13 December 2013.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Krause, David W. (2007). "Overview of the history of discovery, taxonomy, phylogeny, and biogeography of Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar". In Sampson, Scott D.; & Krause, David W. (eds.) (ed.). Majungasaurus crenatissimus (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar. Society of Vertebrate Paleontology Memoir 8. pp. 1–20.
{{cite book}}:|editor=has generic name (help); Unknown parameter|coauthors=ignored (|author=suggested) (help)CS1 maint: multiple names: editors list (link) - ^ a b Sereno, Paul C.; Wilson, JA; Conrad, JL (2007). "New dinosaurs link southern landmasses in the Mid-Cretaceous". Proceedings of the Royal Society B. 271 (1546): 1325–1330. doi:10.1098/rspb.2004.2692. PMC 1691741. PMID 15306329.
- ^ a b Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1098/rspb.2012.0660 , please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1098/rspb.2012.0660instead. - ^ a b Tykoski, Ronald B. (2004). "Ceratosauria". In Weishampel, David B.; Dodson, Peter; & Osmólska, Halszka (eds.) (ed.). The Dinosauria (Second ed.). Berkeley: University of California Press. pp. 47–70. ISBN 0-520-24209-2.
{{cite book}}:|editor=has generic name (help); Unknown parameter|coauthors=ignored (|author=suggested) (help)CS1 maint: multiple names: editors list (link) - ^ Coria, Rodolfo A. (2002). "A new close relative of Carnotaurus sastrei Bonaparte 1985 (Theropoda: Abelisauridae) from the Late Cretaceous of Patagonia" (subscription required). Journal of Vertebrate Paleontology. 22 (2): 460–465. doi:10.1671/0272-4634(2002)022[0460:ANCROC]2.0.CO;2.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ a b Carrano, M.T. (2008). "The phylogeny of Ceratosauria (Dinosauria:Theropoda)". Journal of Systematic Palaeontology (6): 183–236.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ a b Dalla Vecchia, Fabio M. (2006). "Telmatosaurus and the Other Hadrosaurids of the Cretaceous European Archipelago. An Overview". Natura Nascosta (32): 1–55.
- ^ Ezcurra, M.D. (2012). "An abelisauroid dinosaur from the Middle Jurassicof Laurasia and its implications on theropod palaeobiogeography and evolution". Proceedings of Geological Association.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ "Insee - COG - Fiche de la commune de Pourrières". Insee. Retrieved 13 December 2013.
- ^ "VINCI Autoroutes | Quand l'autoroute mène aux dinosaures…" (in French). VINCI Autoroutes. 04 June 2012. Retrieved 13 December 2013.
{{cite web}}: Check date values in:|date=(help) - ^ "VINCI Autoroutes | L'autoroute du temps sur l'A8" (in French). VINCI Autoroutes. Retrieved 13 December 2013.
- ^ a b c d Cojan, Isabelle (2006). "Correlation of Terrestrial Climatic Fluctuations With Global Signals During the Upper Cretaceous–Danian in a Compressive Setting (Provence, France)". Journal of Sedimentary Research. 76: 589–604. doi:10.2110/jsr.2006.045.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ Felix M. Gradstein, James G. Ogg, Mark D. Schmitz, Gabi M. Ogg, ed. (2012). The Geologic Time Scale 2012. p. 810.
{{cite book}}: CS1 maint: multiple names: editors list (link) - ^ Thibault, Nicolas (15 June 2012). "Astronomical calibration of upper Campanian–Maastrichtian carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C): Implication for the age of the Campanian–Maastrichtian boundary". Palaeogeography, Palaeoclimatology, Palaeoecology. 337–338 (52–71). Retrieved 13 December 2013.
{{cite journal}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) - ^ "VINCI Autoroutes | Escota". VINCI Autoroutes. Retrieved 13 December 2013.
