Stegouros
Name: Stegouros
(roofed tail).
Phonetic: Steg-oo-ros.
Named By: Sergio Soto-Acu�a, Jonatan Kaluza,
Marcelo Leppe, Joao Botelho, Jos� Palma-Liberona, Carolina
Gutstein, Roy Fern�ndez, Hector Ortiz, Ver�nica Milla, B�rbara
Aravena, Leslie Manr�quez, Jhonatan Alarc�n-Mu�oz, Juan Pino,
Christine Trevisan, H�ctor Mansilla, Luis Hinojosa, Vicente
Mu�oz-Walther & David Rubilar-Rogers - 2021.
Classification: Chordata, Dinosauria,
Ornithischia, Thyreophora, Ankylosauria, Parankylosauria.
Species: S. elengassen
(type).
Diet: Herbivore.
Size: Estimated between 1.8 and 2 meters
long.
Known locations: Chile - Dorotea Formation.
Time period: Campanian of the Cretaceous.
Fossil representation: Almost complete individual.
Stegouros
is a genus of small ankylosaurian
dinosaur that lived in South America
during the late Cretaceous. What is an immediate stand out feature of
this dinosaur is the tail which has a very distinct arrangement of
osteoderms. This arranging of osteoderms led to comparison to a
maquahuitl, a kind of hand held weapon with a wooden handle and
shards of obsidian (volcanic glass) studded around the edges that
was once use by various Mesoamerican civilisations such as the
Aztec, Maya, Mixtec and Toltec.
The
tail of Stegouros might have been used as a
weapon, though probably
not as sharp as the obsidian blades of a maquahuitl. The difference
in osteoderm arrangement in Stegouros when compared
to other
ankylosaurs might also indicate a display function however. The lack
of ossified tendons in the tail might indicate greater flexibility,
though it’s also possible that the holotype individual of Stegouros
might not have been fully grown. In a related manner there were no
osteoderms found associated with the head. If present they may not
have had time to ossify, even if they did at all.
Stegouros
was small when compared to most other ankylosaurs, though roughly
comparable to some other southern genera. For this reason Stegouros
would have almost certainly been a browser of low growing vegetation.
Other dinosaurs from the same fossil formation as Stegouros
include
sauropods, ornithopods and theropods. However the Dorotea Formation
where the holotype of Stegouros was found is
composed of marine
sediments and also includes plesiosaurs, ammonites and fish. Either
Stegouros lived in a coastal habitat, or was
washed downstream after
death and into an estuary or a coastal sea. We cannot know for
certain, but the high level of preservation in the holotype
individual of Stegouros does mean that it was
probably buried very
quickly before scavengers and the elements could destroy the body.
The
describers of Stegouros also proposed at the time
of the genus
description the creation of a new group of ankylosaurs called the
Parankylosauria (‘Near Ankylosauria’). This group could include
ankylosaurs that are of a different evolutionary lineage separate to
members of the Ankylosauridae and Nodosauridae. At the time of the
creation of the Parankylosauria, all known members are from southern
continents such as Antarctica, Australia and South America, though
there is no telling what future discoveries may teach us.
Further reading
- Bizarre tail weaponry in a transitional ankylosaur from
subantarctic Chile. - Nature. 600 (7888): 259–263. -
Sergio Soto-Acu�a, Jonatan Kaluza, Marcelo Leppe, Joao Botelho,
Jos� Palma-Liberona, Carolina Gutstein, Roy Fern�ndez, Hector
Ortiz, Ver�nica Milla, B�rbara Aravena, Leslie Manr�quez,
Jhonatan Alarc�n-Mu�oz, Juan Pino, Christine Trevisan, H�ctor
Mansilla, Luis Hinojosa, Vicente Mu�oz-Walther & David
Rubilar-Rogers - 2021.
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