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Re: Enantiornithine nesting colony found in Romania



From: Ben Creisler
bh480@scn.org


Since this story is now public, I assume there is no longer an embargo.
Here's the abstract with more technical detail than the online article:

A DROWNED MESOZOIC BIRD BREEDING COLONY
SVP Abstracts 2011
DYKE, Gareth, University College Dublin, Dublin, Ireland; VREMIR, Matyas,
Transylvanian Museum Society, Cluj Napoca, Romania; KAISER, Gary, Royal
British Columbia Museum, Victoria, BC, Canada; NAISH, Darren, University of
Portsmouth, Portsmouth, United Kingdom 

Despite a rapidly improving fossil record, the reproductive biology of
Mesozoic birds remains poorly known: only a handful of undisputed, isolated
Cretaceous eggs (some containing embryonic remains) are known. We report
fossil evidence for a breeding colony of Mesozoic birds, preserved at the
Upper Cretaceous (Maastrichtian) Oarda de Jos (Od) site in the Sebes area
of Transylvania, Romania. This assemblage, preserved as a single, massive,
lens-like accumulation deposited by foodwater and collected from the basal
fuvio-paludal portion of the Sebe? section, includes the bones of adult
enantiornithine birds, neonate skeletal elements, near-complete eggs, and a
huge accumulation of eggshell fragments. Other non-avialian fossils are
absent. 
The Od accumulation shows clear zonation of eggshell indicating primarily
hydrodynamic  deposition: the lower layers comprise densely packed
fragments concave-side-up (45-50 percent of matrix) while the upper layers
include near-complete eggs and a mélange of shell and identifable bone
fragments (preserving enantiornithine synapomorphies). This, alongside
consistent orientation and high abundance of shell fragments (more than 46
eggs per 100 cm3 of sediment estimated in the lower layer), preservation of
tiny bones and almost complete eggs in a high pH water-logged environment,
suggests gradual settling after short transport. Our interpretation is a
large enantiornithine breeding colony that was swamped by rising water,
washed a short distance and deposited in a shallow, low-energy pond. The
same fate often befalls modern bird colonies. 
Such a large concentration of breeding birds must indicate aquatic feeding
and implies both the ability to disperse on foraging expeditions and a
seasonally abundant food resource. These new data augment our understanding
of enantiornithine biology and show that colonial nesting and synchronous
breeding were not unique to crown-birds (Neornithes). Synchronous breeding
in large colonies is a widespread and successful strategy in modern birds,
with the largest examples often found at secure sites like small offshore
islands or sandbars surrounded by flowing water.


===========

An online news story about the discovery of a nesting colony of
enantiornthine birds in Romania announced at the SVP meeting.

http://news.discovery.com/animals/drowned-dino-era-birds-111103.html



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