Tsagantegia (; meaning Tsagan Teg) is a genus of medium-sized ankylosaurid dinosaur that lived in Asia during the Late Cretaceous period. The genus is monotypic, including only the type species, T. longicranialis. The specimen consists of a very partial individual, comprising the skull and lacking postcranial remains. Since it only preserves the skull, Tsagantegia is mainly characterized by its elongated snout and the flattened facial osteoderms, greatly differing from other ankylosaurs.
Discovery and naming
The first, and only, discovery of
Tsagantegia fossils occurred in 1983, when the
Mesozoic team of the Joint Soviet-Mongolian Paleontological Expedition unearthed an
Ankylosauria skull from the
Tsagan-Teg (or "White Mountain") locality near the town of Dzun-Bayan,
Mongolia. This locality is one of many deriving from the Bayan Shireh Formation, an
Late Cretaceous (
Cenomanian-
Turonian)-aged geologic formation in the eastern
Gobi Desert. This ankylosaur skull was then deposited at the Institute of Paleontology and Geology of the Mongolian Academy of Sciences (MPC) under specimen number
MPC 700/17. This skull remained unresearched until it was described by Russian paleontologist Tatiana Tumanova in 1993. Tumanova described the skull as belonging to a new
genus and
species of
Ankylosaurinae Ankylosauridae,
Tsagantegia longicranialis. The generic name,
Tsagantegia, is in reference to the Tsagan-Teg locality where the skull was unearthed, and the specific name,
longicranialis, comes from the
Latin roots
longus "long" and
cranium "skull" in reference to its elongated skull. Due to being known solely from MPC 700/17, MPC 700/17 was chosen as the
holotype (name-bearing) specimen for
Tsagantegia longicranialis. Since its description, no additional remains of
Tsagantegia longicranialis have been mentioned in scientific literature.
Description
Tsagantegia was a medium to large-sized ankyosaur, with an estimated length of
[ Genus List for Holtz 2012 Weight Information ] and weighing about .
The skull measures about in length, with a near width of , missing the lower jaws. Unlike other Asian ankylosaurs, in
Tsagantegia the caputegulae (
cranium ornamentation) are not subdivided into a mosaic of
polygons but are amorphous and flattened; they show some degree of symmetry. The
quadratojugal,
squamosal and orbital horns are poorly preserved, in contrast with other ankylosaurs. The snout was long and flat with a pointed rostrum (beak); each
maxilla preserves approximately 18 alveoli, no teeth were preserved.
According to Arbour,
Tsagantegia differs from
Gobisaurus and
Shamosaurus based on the more rounded, U-shaped premaxillary
beak and the flat ornamentation.
Classification
Although fragmentary, the phylogenetic position of
Tsagantegia can be established. In 2012, Thompson et al. conducted an analysis of almost all known valid ankylosaurs and outgroup taxa at the time. They based their resulting phylogeny on characters representing cranial, post-cranial, and osteodermal anatomy, and details of synapomorphies for each recovered clade.
Tsagantegia was found to be closely related to
Pinacosaurus and
Shamosaurus.
In the performed phylogenetic analysis by Arbour and Currie in 2015, below are the results for the analysis:
Paleoecology
Tsagantegia was unearthed from the Tsagan Teg locality, which represents part of the Upper Bayan Shireh.
U–Pb analyses seem to confirm the age of the Bayan Shireh Formation from 92 million to 86 million years ago,
Cenomanian-
Santonian ages.
Based on comparisons between the snouts of
Tsagantegia and the contemporary
Talarurus, these taxa were divided by niche partitioning. In a palatal view, the rostra
Talarurus have a broad-like, rectangular shape, while
Tsagantegia have a more shovel-like shaped rostra. These morphological differences indicate that
Tsagantegia filled the niche of a browser
herbivore, while
Talarurus was a grazer.
-based boundary indicates a semi-arid environment and climate,
but also, the presence of
fluvial and lacustrine
sediments are indicators of large
rivers and
lakes.
As interpreted by Hicks et al. 1999, during the times of the Bayan Shireh Formation, large rivers drained the eastern part of the
Gobi Desert.
Additional to this,
fossil fruits remains have been recovered from the Bor Guvé and Khara Khutul localities (Upper and Lower Bayan Shireh, respectively), suggesting the presence of
Angiosperm plants.
Tsagantegia shared its habitat with numerous animals from other localities of the formation, compromising dinosaur and non-dinosaur genera; such as the theropods Achillobator,[ the fellow ankylosaur Talarurus;][ and the large sauropod Erketu.][ The turtle Lindholmemys,][
]
See also
