Tyrannotitan

Tyrannotitan (/tɪˌrænəˈttən/; lit.'tyrant titan') is a genus of huge bipedal carnivorous dinosaur of the carcharodontosaurid family from the Aptian stage of the early Cretaceous period, discovered in Argentina. It is closely related to other giant predators like Carcharodontosaurus and especially Giganotosaurus as well as Mapusaurus.

Tyrannotitan
Temporal range: Early Cretaceous (Aptian), 118 Ma
Dinosaurios los gigantes argentinos.jpg
Mounted skeleton
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Family: Carcharodontosauridae
Tribe: Giganotosaurini
Genus: Tyrannotitan
Novas et al., 2005
Type species
Tyrannotitan chubutensis
Novas et al., 2005

Discovery and speciesEdit

 
Known remains (in yellow)
 
Vertebra and ischium

Tyrannotitan chubutensis was described by Fernando E. Novas, Silvina de Valais, Pat Vickers-Rich, and Tom Rich in 2005. The fossils were found at La Juanita Farm, 28 kilometres (17 mi) northeast of Paso de Indios, Chubut Province, Argentina. They are believed to have been from the Cerro Castaño Member, Cerro Barcino Formation (Aptian stage).[1]

The holotype material was designated MPEF-PV 1156 and included partial dentaries, teeth, back vertebrae 3–8 and 11–14, proximal tail vertebrae, ribs and chevrons, a fragmentary scapulocoracoid, humerus, ulna, partial ilium, a nearly complete femur, fibula, and left metatarsal 2. Additional material (designated MPEF-PV 1157) included jugals, a right dentary, teeth, atlas vertebra, neck vertebra (?) 9, back vertebrae (?)7, 10, 13, fused sacral centra (5 total), an assortment of distal caudals, ribs, the right femur, a fragmentary left metatarsal 2, pedal phalanges 2-1, 2–2, and 3-3.[1]

DescriptionEdit

 
Reconstruction of a Tyrannotitan, feeding on a Chubutisaurus.
 
Estimated size, compared to a human.

Tyrannotitan was a large animal, reaching 12.2–13 metres (40–43 ft) in length and 4.8–7 t (5.3–7.7 short tons) in body mass.[2][3][4][5][6] It is geologically the oldest known giant carcharodontosaurid along with the more basal Acrocanthosaurus from North America (both found in Aptian-age rocks).[7][5] Unlike other known carcharodontosaurids, this animal lacks skeletal pneumaticity extending into the sacral and caudal centra. The scapulocoracoid is fused, and much better developed than that of Giganotosaurus carolinii, yet the arm is very small. Most of the shaft of the scapula is missing.[1]

The acromion curves about 90 degrees from the shaft axis, making it look vaguely tyrannosaurid-like. Whether the sharp difference between taxa is due to evolution or sexual dimorphism in poorly sampled populations of both species, has not been determined (the latter seems unlikely). A proximal caudal has a very tall neural spine (about twice the height of its centrum, judging by the figure). The base of the orbital fenestra is a notch of nearly 90 degrees into the body of the jugal, which contrasts with the rounded base restored for Giganotosaurus and agrees with Carcharodontosaurus favorably. The denticles on its teeth are "chisel-like", and are virtually identical to those of other carcharodontosaurids in having a wrinkled enamel surface, heavily serrated mesial and distal carinae, and labiolingually compressed (laterally flattened) crowns.[8] The femur of the paratype specimen is 1.4 m (4.6 ft) long according to Novas et al.[1] Canale et al. recover Tyrannotitan as deeply nested within the tribe Giganotosaurini as its most basal member. Characteristics that unite the Giganotosaurini include the presence of a postorbital process on the jugal with a wide base, and a derived femur with a weak fourth trochanter and a shallow broad extensor groove at the distal end.[8][9]

ClassificationEdit

The following cladogram after Novas et al., 2013, shows the position of Tyrannotitan within Carcharodontosauridae.[10]

Allosaurus  

Carcharodontosauridae

Neovenator  

Eocarcharia

Concavenator  

Acrocanthosaurus  

Shaochilong  

Carcharodontosaurinae

Carcharodontosaurus  

Giganotosaurini

Tyrannotitan

Mapusaurus  

Giganotosaurus  

ReferencesEdit

  1. ^ a b c d Novas, F. E.; S. de Valais; P. Vickers-Rich; T. Rich (2005). "A large Cretaceous theropod from Patagonia, Argentina, and the evolution of carcharodontosaurids". Naturwissenschaften. 92 (5): 226–230. Bibcode:2005NW.....92..226N. doi:10.1007/s00114-005-0623-3. PMID 15834691. S2CID 24015414.
  2. ^ Rey LV, Holtz, Jr TR (2007). Dinosaurs: the most complete, up-to-date encyclopedia for dinosaur lovers of all ages. United States of America: Random House. ISBN 978-0-375-82419-7.
  3. ^ Gregory S. Paul (2010). The Princeton Field Guide to Dinosaurs. United States of America: Princeton University Press. ISBN 9780691137209.
  4. ^ Campione, Nicolás E.; Evans, David C. (2020). "The accuracy and precision of body mass estimation in non-avian dinosaurs". Biological Reviews. 95 (6): 1759–1797. doi:10.1111/brv.12638. ISSN 1469-185X. PMID 32869488. S2CID 221404013.
  5. ^ a b Campione, Nicolás E.; Evans, David C.; Brown, Caleb M.; Carrano, Matthew T. (2014). "Nicolás E. Campione, David C. Evans, Caleb M. Brown, Matthew T. Carrano (2014). Body mass estimation in non-avian bipeds using a theoretical conversion to quadruped stylopodial proportions". Methods in Ecology and Evolution. 5 (9): 913–923. doi:10.1111/2041-210X.12226. S2CID 84317234.
  6. ^ Persons, S. W.; Currie, P. J.; Erickson, G. M. (2020). "An Older and Exceptionally Large Adult Specimen of Tyrannosaurus rex". The Anatomical Record. 303 (4): 656–672. doi:10.1002/ar.24118. ISSN 1932-8486. PMID 30897281.
  7. ^ Bates, Karl T.; Manning, Phillip L.; Hodgetts, David; Sellers, William I. (2009). "Bates KT, Manning PL, Hodgetts D, Sellers WI (2009) Estimating Mass Properties of Dinosaurs Using Laser Imaging and 3D Computer Modelling". PLOS ONE. 4 (2): e4532. Bibcode:2009PLoSO...4.4532B. doi:10.1371/journal.pone.0004532. PMC 2639725. PMID 19225569.
  8. ^ a b Canale, Juan Ignacio; Novas, Fernando Emilio; Pol, Diego (2015). "Osteology and phylogenetic relationships of Tyrannotitan chubutensis Novas, de Valais, Vickers-Rich and Rich, 2005 (Theropoda: Carcharodontosauridae) from the Lower Cretaceous of Patagonia, Argentina". Historical Biology. 27: 1–32. doi:10.1080/08912963.2013.861830. S2CID 84583928.
  9. ^ "Coria R. A. & Currie P. J. 2006. – A new carcharodontosaurid (Dinosauria, Theropoda) from the Lower Cretaceous of Argentina. Geodiversitas 28 (1) : 71–118". {{cite journal}}: Cite journal requires |journal= (help)
  10. ^ Novas, Fernando E. (2013). "Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia". Cretaceous Research. 45: 174–215. doi:10.1016/j.cretres.2013.04.001.