Tarbosaurus - Paleoecology

Paleoecology

The vast majority of known Tarbosaurus fossils were recovered from the Nemegt Formation in the Gobi Desert of southern Mongolia. This geologic formation has never been dated radiometrically, but the fauna present in the fossil record indicate it was probably deposited during the early Maastrichtian stage, at the end of the Late Cretaceous about 70 million years ago. The Subashi Formation, in which Shanshanosaurus remains were discovered, is also Maastrichtian in age.

Nemegt sediments preserve large river channels and soil deposits that indicate a far more humid climate than those suggested by the underlying Barun Goyot and Djadochta Formations. However, caliche deposits indicate at least periodic droughts. Sediment was deposited in the channels and floodplains of large rivers. Occasional mollusc fossils are found, as well as a variety of other aquatic animals like fish and turtles. Crocodilians included several species of Shamosuchus, a genus with teeth adapted for crushing shells. Mammal fossils are exceedingly rare in the Nemegt Formation, but many birds have been found, including the enantiornithine Gurilynia and the hesperornithiform Judinornis, as well as Teviornis, an early representative of the still-existing Anseriformes (waterfowl), a bird order. Scientists have described many dinosaurs from the Nemegt Formation, including ankylosaurids such as Tarchia, and pachycephalosaur Prenocephale. By far the largest predator known from the formation, adult Tarbosaurus most likely preyed upon large hadrosaurs such as Saurolophus and Barsboldia, or sauropods such as Nemegtosaurus, and Opisthocoelicaudia. Adults would have received little competition from small theropods such as troodontids (Borogovia, Tochisaurus, Saurornithoides), oviraptorosaurs (Elmisaurus, Nemegtomaia, Rinchenia) or Bagaraatan, sometimes considered a basal tyrannosauroid. Other theropods, like the gigantic Therizinosaurus, may have been herbivorous, and ornithomimosaurs such as Anserimimus, Gallimimus, and Deinocheirus might have been omnivores that only took small prey and were therefore no competition for Tarbosaurus. However, as in other large tyrannosaurids as well as modern Komodo dragons, juveniles and subadult Tarbosaurus may have filled niches between the massive adults and these smaller theropods.