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Re: Triceratops survived till very end of Cretaceous (citation)

From: Ben Creisler

Here's the full citation for the article about the discovery of a
Triceratops horn right under the K/Pg (K-T) boundary.

Tyler R. Lyson, Antoine Bercovici, Stephen G. B. Chester, Eric J. Sargis,
Dean Pearson and Walter G. Joyce (2011) 
Dinosaur extinction: closing the '3 m gap'.
Biology Letters (advance online publication)
doi: 10.1098/rsbl.2011.0470 

Modern debate regarding the extinction of non-avian dinosaurs was ignited
by the publication of the Cretaceous-Tertiary (K-T) asteroid impact theory
and has seen 30 years of dispute over the position of the stratigraphically
youngest in situ dinosaur. A zone devoid of dinosaur fossils reported from
the last 3 m of the Upper Cretaceous, coined the '3 m gap', has helped
drive controversy. Here, we report the discovery of the stratigraphically
youngest in situ dinosaur specimen: a ceratopsian brow horn found in a
poorly rooted, silty, mudstone floodplain deposit located no more than 13
cm below the palynologically defined boundary. The K-T boundary is
identified using three criteria: (i) decrease in Cretaceous palynomorphs
without subsequent recovery, (ii) the existence of a 'fern spike', and
(iii) correlation to a nearby stratigraphic section where primary
extraterrestrial impact markers are present (e.g. iridium anomaly,
spherules, shocked quartz). The in situ specimen demonstrates that a gap
devoid of non-avian dinosaur fossils does not exist and is inconsistent
with the hypothesis that non-avian dinosaurs were extinct prior to the K-T
boundary impact event. 

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