Archaeopteryx fossil provides insights into the origins of flight
Research reveals earliest flight-related moulting strategy in 150- million-year ancient bird

Date:
December 9, 2020
Source:
The University of Hong Kong
Summary:
Molting is thought to be unorganized in the first feathered
dinosaurs because they had yet to evolve flight, so determining
how molting evolved can lead to better understanding of flight
origins. Recently researchers discovered that the earliest record
of feather molting from the famous early fossil bird Archaeopteryx
found in southern Germany in rocks that used to be tropical lagoons
~150 million years ago.



FULL STORY ========================================================================== Flying birds moult their feathers when they are old and worn because
they inhibit flight performance, and the moult strategy is typically
a sequential molt. Moulting is thought to be unorganised in the first
feathered dinosaurs because they had yet to evolve flight, so determining
how moulting evolved can lead to better understanding of flight origins.


========================================================================== However, evidence of the transition to modern moulting strategies is
scarce in the fossil record. Recently, Research Assistant Professor
Dr Michael PITTMAN from the Research Division for Earth and Planetary
Science, as well as Vertebrate Palaeontology Laboratory, at the Faculty
of Science of the University of Hong Kong (HKU), Thomas G KAYE of the Foundation for Scientific Advancement (Arizona, USA) and William R
WAHL of the Wyoming Dinosaur Center (Wyoming, USA), jointly discovered
the earliest record of feather moulting from the famous early fossil
bird Archaeopteryx found in southern Germany in rocks that used to be
tropical lagoons ~150 million years ago. The findings were published in Communications Biology.

Archaeopteryx moulting strategy used to preserve maximum flight
performance The most common moult strategy in modern birds is a sequential moult, where feathers are lost from both wings at the same time in a symmetrical pattern.

The sequence of feather loss follows two different strategies: The
first strategy is a numerically sequential molt where feathers are
lost in numerical order and is the most common among passerines birds,
also known as songbirds and perching birds; the second strategy is
a centre-out strategy where a centre feather is lost first, and then
subsequent feathers are shed outwards from this centre point; this is more common in non-passerine birds such as falcons. This strategy minimises
the size of the aerodynamic hole in the wing, which allows falcons to
better maintain their flight performance during the moult for hunting.

Laser-Stimulated Fluorescence imaging co-developed at HKU revealed
feather sheaths on the Thermopolis specimen of Archaeopteryx that are
otherwise invisible under white light. "We found feather sheaths mirrored
on both wings.

These sheaths are separated by one feather and are not in numerical
sequential order. This indicates that Archaeopteryx used a sequential centre-out moulting strategy, which is used in living falcons to preserve maximum flight performance," said Kaye. This strategy was therefore
already present at the earliest origins of flight.

"The centre-out moulting strategy existed in early flyers and would
have been a very welcome benefit because of their otherwise poor flight capabilities. They would have appreciated any flight advantage they
could obtain," said Pittman.

"This discovery provides important insights into how and when birds
refined their early flight capabilities before the appearance of iconic
but later flight-related adaptations like a keeled breastbone (sternum),
fused tail tip (pygostyle) and the triosseal canal of the shoulder,"
added Pittman.

This study is part of a larger long-term project by Pittman and Kaye and
their team of collaborators to better understand the origins of flight
(see notes).


========================================================================== Story Source: Materials provided by The_University_of_Hong_Kong. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Thomas G. Kaye, Michael Pittman, William R. Wahl. Archaeopteryx
feather
sheaths reveal sequential center-out flight-related molting
strategy.

Communications Biology, 2020; 3 (1) DOI: 10.1038/s42003-020-01467-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/12/201209115201.htm

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