[Paleontology • 2016]
Timurlengia euotica • New Tyrannosaur from the mid-Cretaceous of Uzbekistan clarifies Evolution of Giant Body Sizes and Advanced Senses in Tyrant Dinosaurs
Timurlengia euotica
Brusatte, Averianov, Sues, Muir & Butler, 2016
DOI: 10.1073/pnas.1600140113 |
Significance
Tyrannosaurs — the iconic group of dinosaurian carnivores that includes Tyrannosaurus rex —dominated
latest Cretaceous ecosystems with their colossal sizes and
sophisticated senses. A gap in the mid-Cretaceous fossil record between
these giant apex predators and their older, smaller relatives makes it
difficult to understand how the characteristic body size and ecological
habits of T. rex and kin developed. A new species from Uzbekistan
fills this gap. This horse-sized animal shows that tyrannosaurs had yet
to achieve huge size at this time but had already evolved key brain and
sensory features of the gigantic latest Cretaceous species.
Tyrannosaurs apparently developed giant body size rapidly, late in the
Cretaceous, and their success may have been enabled by their
early-evolving keen senses.
Abstract
Tyrannosaurids — the familiar group of carnivorous dinosaurs including Tyrannosaurus and Albertosaurus —
were the apex predators in continental ecosystems in Asia and North
America during the latest Cretaceous (ca. 80–66 million years ago).
Their colossal sizes and keen senses are considered key to their
evolutionary and ecological success, but little is known about how these
features developed as tyrannosaurids evolved from smaller basal
tyrannosauroids that first appeared in the fossil record in the Middle
Jurassic (ca. 170 million years ago). This is largely because of a
frustrating 20+ million-year gap in the mid-Cretaceous fossil record,
when tyrannosauroids transitioned from small-bodied hunters to gigantic
apex predators but from which no diagnostic specimens are known. We
describe the first distinct tyrannosauroid species from this gap, based
on a highly derived braincase and a variety of other skeletal elements
from the Turonian (ca. 90–92 million years ago) of Uzbekistan. This
taxon is phylogenetically intermediate between the oldest basal
tyrannosauroids and the latest Cretaceous forms. It had yet to develop
the giant size and extensive cranial pneumaticity of T. rex and
kin but does possess the highly derived brain and inner ear
characteristic of the latest Cretaceous species. Tyrannosauroids
apparently developed huge size rapidly during the latest Cretaceous, and
their success in the top predator role may have been enabled by their
brain and keen senses that first evolved at smaller body size.
Keywords: dinosaur, Tyrannosauroidea, Uzbekistan, phylogenetics, evolution
A fossil tooth
(front and back) of the newly discovered dinosaur. The blade-like teeth,
says Hans Sues, were well-suited for "slicing through meat." |
Systematic Paleontology
Dinosauria Owen, 1842; Theropoda Marsh, 1881;
Coelurosauria Huene, 1914; Tyrannosauroidea Osborn, 1905;
Timurlengia euotica gen. et sp. nov.
Holotype: ZIN PH (Paleoherpetological Collection, Zoological Institute, Russian Academy of Sciences, Saint Petersburg, Russia) 1146/16, a well-preserved braincase missing only the paroccipital processes and much of the parabasisphenoid (Figs. 1 and 2 and Figs. S1−S3).
Etymology Timurlengia, in reference to the fourteenth-century Central Asian ruler Timurleng (English: Tamerlane), and euotica, meaning “well eared” in reference to the large inner ear of the holotype.
Horizon and Locality: Dzharakuduk, central Kyzylkum Desert, Navoi Viloyat, Uzbekistan. Bissekty Formation, Upper Cretaceous, Middle-Upper Turonian (ca. 90–92 million years ago)
Conclusions
Timurlengia is a long-awaited diagnostic tyrannosauroid from the
middle part of the Cretaceous. It indicates that these predators
were still far from giants during this time, but had already
evolved signature brain and sensory features that may have been
tied to the extraordinary success of the last-surviving, latest Cretaceous
species like Tyrannosaurus. However, Timurlengia remains a
single data point from a still murky interval in dinosaur history, and
future discoveries from this gap will undoubtedly lead to a better
understanding of how tyrannosauroids rose from marginal creatures
into some of the largest terrestrial predators in Earth history.
Stephen L. Brusatte, Alexander Averianov, Hans-Dieter Sues, Amy Muir
and Ian B. Butler. 2016. New Tyrannosaur from the mid-Cretaceous of
Uzbekistan clarifies Evolution of Giant Body Sizes and Advanced Senses
in Tyrant Dinosaurs. Proceedings of the National Academy of Sciences of the United States of America. in press. DOI: 10.1073/pnas.1600140113
The discovery of a tiny Tyrant set the stage for the evolution of T. rex
http://po.st/TSbHav via @SmithsonianMag @NMNH #PreRex
Behold Timurlengia—the Elusive Missing Link in Tyrannosaur Evolution
http://gizmodo.com/behold-timurlengia-the-elusive-missing-link-in-tyrannos-1764749916
http://po.st/TSbHav via @SmithsonianMag @NMNH #PreRex
Behold Timurlengia—the Elusive Missing Link in Tyrannosaur Evolution
http://gizmodo.com/behold-timurlengia-the-elusive-missing-link-in-tyrannos-1764749916
Timurlengia euotica: Distant relative of T-rex shows how dinosaur became giant
http://ibt.uk/A6V4r via @IBTimesUK #dinosaurevolution
http://ibt.uk/A6V4r via @IBTimesUK #dinosaurevolution
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