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Protoceratops juvenile aggregation from Mongolia

Ben Creisler

New in PLoS ONE:

David W. E. Hone, Andrew A. Farke, Mahito Watabe, Suzuki Shigeru &
Khishigjav Tsogtbaatar (2014)
A New Mass Mortality of Juvenile Protoceratops and Size-Segregated
Aggregation Behaviour in Juvenile Non-Avian Dinosaurs.
PLoS ONE 9(11): e113306.



Monodominant bonebeds are a relatively common occurrence for non-avian
dinosaurs, and have been used to infer associative, and potentially
genuinely social, behavior. Previously known assemblages are
characterized as either mixed size-classes (juvenile and adult-sized
specimens together) or single size-classes of individuals (only
juveniles or only adult-sized individuals within the assemblage). In
the latter case, it is generally unknown if these kinds of
size-segregated aggregations characterize only a particular size stage
or represent aggregations that happened at all size stages.
Ceratopsians (“horned dinosaurs”) are known from both types of

Methods/Principal Findings

Here we describe a new specimen of the ceratopsian dinosaur
Protoceratops andrewsi, Granger and Gregory 1923 from Mongolia
representing an aggregation of four mid-sized juvenile animals. In
conjunction with existing specimens of groups of P. andrewsi that
includes size-clustered aggregations of young juveniles and
adult-sized specimens, this new material provides evidence for some
degree of size-clustered aggregation behaviour in Protoceratops
throughout ontogeny. This continuity of size-segregated (and
presumably age-clustered) aggregation is previously undocumented in
non-avian dinosaurs.


The juvenile group fills a key gap in the available information on
aggregations in younger ceratopsians. Although we support the general
hypothesis that many non-avian dinosaurs were gregarious and even
social animals, we caution that evidence for sociality has been
overstated and advocate a more conservative interpretation of some
data of ‘sociality’ in dinosaurs.