Showing posts with label Albelisauroids. Show all posts
Showing posts with label Albelisauroids. Show all posts

Wednesday, 26 March 2014

Dinosaur remains from northwestern Saudi Arabia.

Dinosaurs are the most distinctive element of Mesozoic Vertebrate faunas, arising in the Triassic, and coming to dominate all known terrestrial ecosystems during the Jurassic and Cretaceous, before disappearing abruptly (other than the still extant Birds) at the end of that period. Despite this widespread distribution, very few Dinosaur remains are known from the Middle East, with a few scattered remains recorded from Oman, Jordan, Yemen, Egypt and Lebanon, and, to date, only two recorded Dinosaur finds from Saudi Arabia, and unidentified Sauropod, possibly a Titanosaur, and some other unidentified bones, all from the late Cretaceous Adaffa Formation of the Midyan Peninsula, in the northwest of the country, collected between 2004 and 2008 by a joint expedition of the Saudi Geological Survey and the Egyptian Geological Museum.

In a paper published in the journal PLoS One on 26 December 2013, a team of scientists led by Benjamin Kear of the Department of Earth Sciences at Uppsala University formerly describe these Dinosaur  specimens for the first time.

Geological map of northeast of Saudi Arabia, showing outcrops of the Addafa Formation. Kear et al. (2014).

The material comprises seven caudal (tail) vertebrae, plus two other fragments, from a Sauropod Dinosaur, plus two Theropod teeth, collected from a limestone outcrop 11 km northeast of Al Kuraybah. The specimens were disarticulated, apparently due to water turbulence, but are thought to come from only two animals (i.e. one Sauropod and one Theropod). The most complete vertebra has a length of 105 mm and a height of 133 mm, and does indeed appear to be from a Titanosaur. Both of the teeth are fragmentary in nature, though they are distinctively Theropod in nature, flattened with a serrated cutting edge, and are thought to most likely be from an  Abelisaurid.

Dinosaur remains from the Adaffa Formation of Saudi Arabia. Titanosaurian distal caudal vertebra in: (A) anterior; (B) lateral; and (C) posterior views. Abelisaurid teeth including: (D) crown fragment with enlargement of the distal denticles; and maxillarydentary tooth shown in distal (E) and lateral (F) views with enlargements of the distal carina and baso-apical enamel ridges. Kear et al. (2014)


See also A dwarf Tyrannosaurid from the Late Cretaceous of northern Alaska, Bite marks on the bones of Late Cretaceous juvenile Ornithischian Dinosaurs from Utah, A new species of Theropod Dinosaur from the Late Jurassic of Portugal, A new species of Titanosaur from the Early Cretaceous of Texas and The foot of a small Alvarezsauroid Dinosaur from Inner Mongolia, China.

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Sunday, 13 October 2013

A new species of Abelisauroid Dinosaur from the Late Cretaceous of Madagascar.

The Albelisauroids were a group of Theropod Dinosaurs that appeared in the Middle Cretaceous, and underwent a major diversification in the Cretaceous. They were restricted to the southern continent of Gondwana, which by the Cretaceous had separated from the supercontinent of Pangea and started to break up into the continents of today's Southern Hemisphere; Albelisauroids are known from Africa, Madagascar, India and South America. Albelisauroids were noted for having short, but tall and often ornamented skulls, as well as often having greatly reduced forelimbs.

In a paper published in the journal PLoS One on 18 April 2013, Andrew Farke of the Raymond M. Alf Museum of Paleontology in Claremont, California and Joseph Sertich of the Department of Earth Sciences at the Denver Museum of Nature and Science, describe a new species of Abelisauroid Dinosaur from the Late Cretaceous of Madagascar.

The new species is named Dahalokely tokana, where 'Dahalokely' means 'small bandit' and 'tokana' means lonely, both in Malagasy; references to the species' small size for an Albesauroid and location on the isolated landmass of Madagascar. The species is described from six complete vertebrae and one partial vertebra, plus one complete and three partial ribs. This material is enough to confidently place Dahalokely tokana within the Abelisauroidea, but not to make any good estimation of its place within the group. It is calculated that the specimen was about 3.5 m long when living.

Dahalokely tokana. (A) Reconstructed silhouette with preserved elements indicated in white. Cervical vertebra (C?5) in (B) cranial; (C) left lateral; and (D) dorsal views. Dorsal vertebra (D 2) in (E) cranial; (F) left lateral, and (G) dorsal views. Dorsal vertebra (D?6) in (H) cranial; (I) left lateral; and (J) dorsal views. Abbreviations: cprl, centroprezygapophyseal lamina; didfs, dorsal infradiapophyseal fossa; diprfs, dorsal infraprezygapophyseal fossa; dp, diapophysis; ep, epipophysis; ha, hypantrum; ho, hyposphene; idfs, infradiapophyseal fossa; ipofs, infrapostzygapophyseal fossa; iprfr, infraprezygapophyseal foramen; iprfs, infraprezygapophyseal fossa; lpfr, laminopeduncular foramen; ns, neural spine; pfr, pneumatic foramen; posf, postspinal fossa; poz, postzygapophysis; pp, parapophysis; prel, prezygoepipophyseal lamina; prsf, prespinal fossa; prz, prezygapophysis; sprl, spinoprezygapophyseal lamina; vidfs, ventral infradiapophyseal fossa; viprfs, ventral infraprezygapophyseal fossa. Farke & Sertich (2013).


Madagascar and India are thought to have separated from the rest of Gondwana around 100 million years ago, and from one-another around 88 million years ago. The deposits from which Dahalokely tokana was recovered are thought to be around 90 million years old, thus potentially shedding light into this period of time, when little fossil material is known from Madagascar. Most Cretaceous material from Madagascar, including all previously described Abelisauroids from the island, is around 70 million years old, making Dahalokely tokana the oldest known member of the group from Madagascar by around 20 million years.

The approximate location of the site where Dahalokely tokana was discovered. Farke & Sertich (2013).


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Tuesday, 13 August 2013

An Abelisauroid from the Late Cretaceous of Brazil.

The Albelisauroids were a group of Theropod Dinosaurs that appeared in the Middle Cretaceous, and underwent a major diversification in the Cretaceous. They were restricted to the southern continent of Gondwana, which by the Cretaceous had separated from the supercontinent of Pangea and started to break up into the continents of today's Southern Hemisphere; Albelisauroids are known from Africa, Madagascar, India and South America. Albelisauroids were noted for having short, but tall and often ornamented skulls, as well as often having greatly reduced forelimbs.

In a paper published in the journal Revista Mexicana de Ciencias Geológicas on 4 March 2013, Elaine Machado of the Laboratório de Sistemática e Tafonomia de Vertebrados Fósseis at the Departamento de Geologia e Paleontologia at the Museu Nacional and Universidade Federal do Rio de JaneiroDiogenes de Campos of the Museu de Ciências da Terra at the Departamento Nacional de Produção Mineral do Brasil, Jorge Calvo of the Centro Paleontológico Lago Barreales at the Universidad Nacional del Comahue and Alexander Kellner also of the Laboratório de Sistemática e Tafonomia de Vertebrados Fósseis discuss a new Albelisauroid specimen from the Maastrichtian (end Cretaceous) Marília Formation near Peirópolis in Brazil.

The specimen is described from a single right tibia, 395 mm in length, though considered distinctive enough that Machado et al. do not consider that it belonged to any previously described species. However due to the limited nature of the material, the specimen is not formally described as a new species, but rather referred to as the 'Cambará Theropod'.

Right tibia of the Cambará Theropod. (a) Anterior view showing the torsion presented in relation to the proximal and distal condyles; (b) posterior view showing the two asymmetrical condyles and the surrounding muscle attachment scars; (c) medial view, showing muscle scars on the proximal epiphysis, and muscle scars in proximal and distal portions; and (d) lateral view; note the cnemial crest is elevated above the proximal articulation. Abbreviations: cnc - cnemial crest, dep - depression, gr –groove, tfap - tibial facet for ascending process of astragalus, tfas - tibial facet for astragalus, fc - fibular crest, ff - fibular facet, lcon - lateral condyle, lm - lateral malleolus, mcon -medial condyle, mm - medial malleolus, mus - muscle scar. Scale bar is 100 mm. Machado et al. (2013).



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