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Dinosaur behavior and reproduction constraints in the Late Cretaceous High Arctic



Ben Creisler
bcreisler@gmail.com


A new online paper:



Alexei B. Herman, Robert A. Spicer & Teresa E.V. Spicer (2015)
Environmental Constraints on Terrestrial Vertebrate Behaviour and
Reproduction in the High Arctic of the Late Cretaceous.
Palaeogeography, Palaeoclimatology, Palaeoecology  (advance online publication)
doi:10.1016/j.palaeo.2015.09.041
http://www.sciencedirect.com/science/article/pii/S0031018215005519


Highlights

Late Cretaceous high Arctic vegetation and climates are described and quantified
Climate and light regimes are used to determine times of leaf bud
break and leaf fall
Large dinosaur migration distances to avoid freezing could have been
less than 600 km
Reproduction is needed for permanent residency: egg incubation
environments discussed
Ambient palaeoconditions suggest brooding and/or sophististicated nest
management



Abstract

Reconstructions of temperature and moisture regimes based on fossil
leaves, combined with tree ring studies, detail the light regime,
length of the growing season, and summer and winter temperatures of
the Late Cretaceous Arctic. Such constraints have important
implications for dinosaur feeding and reproductive behaviour, and the
capacity to reside year-round in near-polar environments.

At the highest palaeolatitudes where dinosaurs have been found (82-85
°N) winter darkness lasted for ~ 120 days and the spring and autumn
twilight periods for ~ 15 days. A mostly cloud and mist-shrouded
environment witnessed a mean annual temperature (MAT) of 6-7 °C, a
warm month mean temperature (WMMT) of 14.5 ± 3.1 °C and a cold month
mean temperature (CMMT) of -2 ± 3.9 °C. Growth rings in wood suggest
summer temperatures frequently fell below + 10 °C. Winter temperatures
as low as -10 °C were likely for short periods. Spring bud break in
late February to early March and leaf fall in early October limited
the time when fresh food was available in any quantity to not more
than 6 months.

The diversity of Arctic dinosaur body sizes implies a range of
overwintering strategies but year-round residency requires
reproduction. Burrowing and enclosed nest building no doubt
facilitated overwintering for small animals, but for larger dinosaurs
shelter was problematical. No dinosaur egg remains have yet been found
as far north as 82° palaeolatitude, but they occur 6° further south in
the Early Maastrichtian Kakanaut Formation, Northeastern Russia. Here
the winter darkness was shorter (45 days), and the temperature regime
warmer (MAT 10 °C, WMMT 19 °C, CMMT + 3 °C). The growing season
(temperatures > 10 °C) was ~ 6.3 months and fresh food was available
in quantity for slightly longer. These summer temperatures constrain
the thermal regime of nest environments and suggest sophisticated nest
management and possibly brooding strategies for the necessary rapid
incubation and hatching before the onset of winter.

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