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What did the first snakes look like?
The original snake ancestor was a nocturnal, stealth-hunting predator that had
tiny hindlimbs with ankles and toes, according to research published in the open
access journal BMC Evolutionary Biology.
The study, led by Yale University,
USA, analyzed fossils, genes, and
anatomy from 73 snake and lizard
species, and suggests that snakes
first evolved on land, not in the
sea, which contributes to a
longstanding debate. They most
likely originated in the warm,
forested ecosystems of the
Southern Hemisphere around 128
million years ago.
Snakes show incredible diversity, with over 3,400 living species found in a wide
range of habitats, such as land, water and in trees. But little is known about
where and when they evolved, and how their original ancestor looked and
behaved.
Lead author Allison Hsiang said: “While snake origins have been debated for a
long time, this is the first time these hypotheses have been tested thoroughly
using cutting-edge methods. By analyzing the genes, fossils and anatomy of 73
different snake and lizard species, both living and extinct, we’ve managed to
generate the first comprehensive reconstruction of what the ancestral snake was
like.”
By identifying similarities and differences between species, the team constructed
a large family tree and illustrated the major characteristics that have played out
throughout snake evolutionary history.
Their results suggest that snakes originated on land, rather than in water, during
the middle Early Cretaceous period (around 128.5 million years ago), and most
likely came from the ancient supercontinent of Laurasia. This period coincides
with the rapid appearance of many species of mammals and birds on Earth.
The ancestral snake likely possessed a pair of tiny hindlimbs, and targeted softbodied vertebrate and invertebrate prey that were relatively large in size
compared to prey targeted by lizards at the time. While the snake was not
limited to eating very small animals, it had not yet developed the ability to
manipulate prey much larger than itself by using constriction as a form of attack,
as seen in modern Boa constrictors.
While many ancestral reptiles were most active during the daytime (diurnal), the
ancestral snake is thought to have been nocturnal. Diurnal habits later returned
around 50-45 million years ago with the appearance of Colubroidea - the family
of snakes that now make up over 85% of living snake species. As colder night
time temperatures may have limited nocturnal activity, the researchers say that
the success of Colubroidea may have been facilitated by the return of these
diurnal habits.
The results suggest that the success of snakes in occupying a range of habitats
over their evolutionary history is partly due to their skills as ‘dispersers’. Snakes
are estimated to be able to travel ranges up to 110,000 square kilometres,
around 4.5 times larger than lizards. They are also able to inhabit environments
that traditionally hinder the dispersal of terrestrial animals, having invaded
aquatic habitats multiple times in their evolutionary history.
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BioMed Central
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Notes to editor:
1.
Image: Reconstruction of the ancestral crown-group snake, based on this study.
Artwork by Julius Csotonyi. Full resolution image available to download from:
http://bit.ly/1FmWwiw
You are free to re-use this image on the condition that you credit Julius Csotonyi.
2.
Research article
Allison Y Hsiang, Daniel J Field, Timothy H Webster, Adam DB Behlke, Matthew B Davis,
Rachel A Racicot and Jacques A Gauthier
The origin of snakes: revealing the ecology, behavior, and evolutionary history of early
snakes using genomics, phenomics, and the fossil record
BMC Evolutionary Biology 2015
doi: 10.1186/s12862-015-0358-5
During embargo, article available here: http://bit.ly/1JL3mMz
After embargo, article available at journal website here:
http://dx.doi.org/10.1186/s12862-015-0358-5
Please name the journal in any story you write. If you are writing for the web, please
link to the article. All articles are available free of charge, according to BioMed Central's
open access policy.
3.
BMC Evolutionary Biology is an open access, peer-reviewed journal that considers
articles on all aspects of molecular and non-molecular evolution of all organisms, as well
as phylogenetics and palaeontology.
BMC Evolutionary Biology is part of the BMC series which publishes subject-specific
journals focused on the needs of individual research communities across all areas of
biology and medicine. We offer an efficient, fair and friendly peer review service, and are
committed to publishing all sound science, provided that there is some advance in
knowledge presented by the work.
4.
BioMed Central is an STM (Science, Technology and Medicine) publisher which has
pioneered the open access publishing model. All peer-reviewed research articles
published by BioMed Central are made immediately and freely accessible online, and are
licensed to allow redistribution and reuse. BioMed Central is part of Springer
Science+Business Media, a leading global publisher in the STM sector.
www.biomedcentral.com