Wednesday, December 19, 2018

Paralititan stromeri - giant titanosaurian from Albian-Cenomanian of Egypt

Paralititan (meaning "tidal giant") was a giant titanosaurian sauropod dinosaur genus discovered in coastal deposits in the Upper Cretaceous Bahariya Formation of Egypt. It lived between 99.6 and 93.5 million years ago.

Joshua Smith, who informally led the research team that found the dinosaur fossils, told an interviewer, "It was a truly enormous dinosaur by any reckoning."

Paralititan size by Sassani, 2012.

Little of Paralititan is known, so its exact size is difficult to estimate. However, the limited material, especially the long humeri, suggested that it is one of the most massive dinosaurs ever discovered, with an estimated weight of 59 t (65 short tons). The complete right humerus measured 1.69 meters (5.54 ft) long which at the time of discovery was the longest known in a Cretaceous sauropod; this was surpassed in 2016 with the discovery of Notocolossus which had a 1.76 m (5 ft 9 in) humerus. Using Saltasaurus as a guide, Carpenter estimated its length at around 26 m (85 ft). Scott Hartman estimates an animal that is massive, but still smaller than the biggest titanosaurs such as PuertasaurusAlamosaurus, and Argentinosaurus. In 2010, Gregory S. Paul estimated the length at twenty metres, the weight at twenty tonnes.

From the formation another sauropod had already been known, AegyptosaurusParalititan differs from Aegyptosaurus in its larger size, the latter genus weighing only fifteen tons, possibly in not having pleurocoels in its front tail vertebrae, and in possessing a relatively longer deltopectoral crest on its humerus.

Humeri at the Egyptian Geological Museum

The holotype specimen of Paralititan, CGM 81119, was found in a layer of the Bahariya Formation, dating from the Cenomanian. It consists of a partial skeleton lacking the skull. It is incomplete, apart from bone fragments containing two fused posterior sacral vertebrae, two anterior caudal vertebrae, both incomplete scapulae, two humeri and a metacarpal. The Paralititan type specimen shows evidence of having been scavenged by a carnivorous dinosaur as it was disarticulated within an oval of eight metres length with the various bones being clustered. A Carcharodontosaurus tooth was discovered in between the clusters. The holotype is part of the collection of the Cairo Geological Museum.

The large anterior dorsal vertebra 1912V11164, in 1932 by Stromer referred to an undetermined "Giant Sauropod", was in 2001 tentatively referred to Paralititan.

The autochthonous, scavenged skeleton was preserved in tidal flat deposits containing in the form of fossil leaves and root systems, a mangrove vegetation of seed ferns, Weichselia reticulata. The mangrove ecosystem it inhabited was situated along the southern shore of the Tethys Sea. Paralititan is the first dinosaur demonstrated to have inhabited a mangrove habitat. It lived at approximately the same time and place as giant predators CarcharodontosaurusSpinosaurus, and the sauropod Aegyptosaurus.

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