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Hesperornis osteohistology compared to penguins (free pdf)

Ben Creisler

A new paper in open access:

Laura E. Wilson & Karen Chin (2014)
Comparative osteohistology of Hesperornis with reference to pygoscelid
penguins: the effects of climate and behaviour on avian bone
Royal Society Open Science 1: 140245
doi: http://dx.doi.org/10.1098/rsos.140245

The broad biogeographic distribution of Hesperornis fossils in Late
Cretaceous Western Interior Seaway deposits has prompted questions
about whether they endured polar winters or migrated between mid- and
high latitudes. Here, we compare microstructures of hesperornithiform
long bones from Kansas and the Arctic to investigate whether migration
or Late Cretaceous polar climate affected bone growth. We also examine
modern penguin bones to determine how migration and climate may
influence bone growth in birds with known behaviours. Histological
analysis of hesperornithiform samples reveals continuous bone
deposition throughout the cortex, plus an outer circumferential layer
in adults. No cyclic growth marks, zonation or differences in
vasculature are apparent in the Hesperornis specimens. Comparatively,
migratory Adélie and chinstrap penguin bones show no zonation or
changes in microstructure, suggesting that migration is not
necessarily recorded in avian bone microstructure. Non-migratory
gentoos show evidence of rapid bone growth possibly associated with
increased chick growth rates in high-latitude populations and large
body size. The absence of histological evidence for migration in
extinct Hesperornis and extant pygoscelid penguins may reflect that
these birds reached skeletal maturity before migration or
overwintering. This underscores the challenges of using bone
microstructure to infer the effects of behaviour and climate on avian