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Alvarezsaurid Eggs Discovered

An Argentine-Swedish research team has reported a 70-million-year-old pocket of fossilized bones and unique eggs of an enigmatic birdlike dinosaur in Patagonia.
“What makes the discovery unique are the two eggs preserved near articulated bones of its hind limb. This is the first time the eggs are found in a close proximity to skeletal remains of an alvarezsaurid dinosaur,” says Dr. Martin Kundrát, dinosaur expert from the group of Professor Per Erik Ahlberg at Uppsala University.
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Bonapartenykus

Name: »Bonaparte claw«
Length: 1,5 m
Height: 0,5 m
Weight: 7 kg
Diet: carnivore
Time: Cretaceous (70 MYA)
Location: South America (Argentina)

“Bonapartenykus” is a genus of alvarezsaurid theropod dinosaurs known from the Late Cretaceous (Campanian/Maastrichtian stage) of northwestern Patagonia, Argentina. The type species has been designated “B. ultimus”. This name of this species and its initial description appeared in an online manuscript in December 2011, but will not be formally published until at least 2012.

The species was named and described in the 2011/2012 year, by Federico Angolinom, Jaime Powell, Emilio Fernando Novas and Martin Kundratom. The genus name was given in honor of José Fernando Bonaparte, linking his name with the ancient Greek word onyx – meaning “claw.” Specific name “ultimus” is Latin for “last”, referring to the fact that the dinosaur is one of the last members of the group Alvarezsauridae.
Bonapartenykus is rather large dinosaur of the family alvareszavridov, with a body length of about five feet (1,5 m) and weighing about fifteen pounds (7 kg).

The Alvarezsauridae represents a branch of peculiar basal coelurosaurs with an increasing representation of their Cretaceous radiation distributed worldwide. Here we describe a new member of the group, Bonapartenykus ultimus gen. et sp. nov. from Campanian–Maastrichtian strata of Northern Patagonia, Argentina. Bonapartenykus is represented by a single, incomplete postcranial skeleton.

The morphology of the known skeletal elements suggests close affinities with the previously described taxon from Patagonia, Patagonykus, and both conform to a new clade, here termed Patagonykinae nov. Two incomplete eggs have been discovered in association with the skeletal remains of Bonapartenykus, and several clusters of broken eggshells of the same identity were also found in a close proximity. These belong to the new ooparataxon Arraigadoolithus patagoniensis of the new oofamily Arraigadoolithidae, which provides first insights into unique shell microstructure and fungal contamination of eggs laid by alvarezsaurid theropods.

The detailed study of the eggs sheds new light on the phylogenetic position of alvarezsaurids within the Theropoda, and the evolution of eggs among Coelurosauria. We suggest that plesiomorphic alvarezsaurids survived in Patagonia until the latest Cretaceous, whereas these basal forms became extinct elsewhere.

The new clade Patagonykinae is established in order to include Patagonykus and the new genus Bonapartenykus- The alvarezsaurid-type eggs is unique and constitutes the ootaxon Arraigadoolithidae- Fossil eggshells indicate the presence of fungal contamination- Basal alvarezsaurids persisted in South America until Latest Cretaceous times.

The alvarezsaur was not in good shape when the researchers found it. While some of the bones, particularly those of the leg, were close to their original articulation, Bonapartenykus is represented by an incomplete set of partially damaged bones, without a skull. (Subtle characteristics of the preserved vertebra, shoulder girdle, and hips are what led Agnolin and co-authors to identify this animal as an alvarezsaur despite the paucity of bones.) But there was also something else. Next to the bones were the battered remnants of at least two dinosaur eggs. Could these be fossil evidence of a Bonapartenykus that was protecting its nest?
Determining who laid those eggs is a difficult task. No evidence of embryos has been found inside the egg, so we can’t entirely be sure of what kind of dinosaur was growing inside. The close association between the fossils is the primary line of evidence that the eggs might be attributable to Bonapartenykus. This is the hypothesis favored by Agnolin and co-authors, but they doubt that the small site represents parental care. There is no evidence of a nest. Instead the scientists suggest that the two eggs may still have been inside the dinosaur when it died—a hypothesis based on the previous discovery of an oviraptorosaur from China with a pair of eggs preserved where the dinosaur’s birth canal would have been. When the alvarezsaur perished, the eggs may have fallen out of the body and been preserved with the bones.

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Alvarezsauridae
Genus: Bonapartenykus
Species: B. ultimus Agnolin et al., 2012

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