Named By: Jose F. Bonaparte - 1991.
Classification: Chordata, Reptilia, Dinosauria, Saurischia, Theropoda, Alvarezsauroidea, Alvarezsauridae.
Species: A. calvoi (type).
Size: Estimated about 1.2 meters long.
Known locations: Argentina - Bajo de la Carpa Formation.
Time period: Santonian of the Cretaceous.
Fossil representation: Partial remains.
was the first of a group of dinosaurs that were first discovered late
into the twentieth century. Since it was the first, Alvarezsaurus
was used to name this new group which became known as the
At the time of writing there are now several genera of
alvarezsaurs known to us, but in a twist the type genus,
Alvarezsaurus, has remained one of the most
incomplete and least
understood. This is not the first time that such a thing has happened
though, the ankylosaurs,
the armoured herbivorous dinosaurs with
clubbed tails are named after one of the most famous dinosaurs of all
yet Ankylosaurus is one of
the most incomplete
of these. Alvarezsaurus was named in honour of
the historian Don
Gregorio Alvarez, and not after Luis Alvarez a famous physicist and
‘amateur’ palaeontologist who was among the first to suggest that a
comet or meteor was responsible for causing the KT extinction and
wiping out the dinosaurs.
Alvarezsaurus has been estimated at about two meters long, something which makes it large for its kind. Alvarezsaurus also seems to have been quite primitive in form when compared to other genera. Like its relatives Alvarezsaurus is noted for having an enlarged finger with a large claw. The popular consensus is that this claw was used to jab holes into the sides of termite mounds so that an individual Alvarezsaurus could pick off individual termites. Modelling studies however have so far not shown a lot of support for this theory, though it has not been discounted completely. It may be that the true function of the finger still remains unknown to us at the time of writing.
Another alvarezsaurid known from the same formation as Alvaresaurus is the genus Achillesaurus. Although still often treated as a distinct genus, at the time of writing at least one study (Makovicky et al, 2012) has considered that this genus might be a synonym to Alvarezsaurus.
- Los vertebrados fósiles de la Formación Rio Colorado, de la Ciudad de Neuquén y Cercanías, Cretácico Superior, Argentina [The vertebrate fossils of the Rio Colorado Formation, from the city of Neuquén and surrounding areas, Upper Cretaceous, Argentina]. - Revista del Museo Argentino de Ciencias Naturales "Bernardino Rivadavia" e Instituto Nacional de Investigación de las Ciencias Naturales: Paleontología 4(3):17-123 - Jose F. Bonaparte - 1991.
- A New Coelurosaurian Theropod from the La Buitrera Fossil Locality of Río Negro, Argentina. - Fieldiana Life and Earth Sciences 5: 90. - P. J. Makovicky, S. N. Apesteguía & F. A. Gianechini - 2012.