Never-before-seen ammonite muscles revealed in 3D from Jurassic fossil
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Never-before-seen ammonite muscles
revealed in 3D from Jurassic fossil
8 December 2021, by Nicky Jenner, Caroline Brogan
ammonites than previously thought.
Study co-author Dr. Alan Spencer, from Imperial's
Department of Earth Science and Engineering and
the Natural History Museum, said: "This ammonite
is remarkably well preserved, which is very rare.
New imaging techniques allowed us to visualize the
internal soft parts of ammonites that have so far
resisted all our previous efforts to describe them.
This is a major breakthrough in ammonite
palaeobiology."
Left: 3D reconstruction. Right: Labelled internal organs.
Credit: Cherns et al. Squid-like propulsion
Ammonites, which became extinct around 66
million years ago, once thrived in oceans as
For the first time, researchers have revealed the dinosaurs ruled the Earth. They are among the
soft tissues of a 165-million-year-old ammonite most common fossils worldwide, but almost
fossil using 3D imaging. everything we know about them so far is based on
their hard shells as these are more easily
They found that the now-extinct molluscs sported preserved over millennia than bodily tissues. Thus,
hyponomes: tube-like siphons through which water ammonite fossils with preserved muscles and
is expelled to jet propel animals forward in water, organs are extremely rare.
as found in modern squid and octopuses. They
also found strong muscles that ammonites used to To carry out the study, the researchers studied the
retract into their shells to defend against predators. five-centimeters-across ammonite fossil which was
found within an exposed Jurassic sediment at a
The team, led by researchers from Cardiff Gloucestershire site in 1998. They looked at the
University and including Imperial College London, fossil's remaining soft tissues and scarring where
found this by analyzing the muscles and organs of muscles once attached to the inside of its shell.
an exceptionally well-preserved ammonite fossil
found over 20 years ago in Gloucestershire, UK.
The research, published in Geology, marks the first
time an ammonite's softer parts have been
visualized in three dimensions—and is thanks to a
combination of modern technology, the fossil's
exceptional preservation, and collaboration across
interdisciplinary teams and facilities.
The findings add insight into how ammonites lived
and are evidence that coleoids, the sub-group of
animals containing squid, octopuses, and
cuttlefish, might be evolutionarily closer to
1/3
preserved, scientists have used modern Nautilus as
a 'body-plan' for reconstructing ammonite biology.
However, this study highlights that ammonites and
Nautilus may not be as similar as previously
thought.
Backlit shell with visible organs (to the left). Credit:
Cherns et al.
By combining high-resolution X-ray and high-
contrast neutron imaging, they created a detailed
3D computer reconstruction of the structure, size
and orientation of its muscles and organs. From
this detailed model, they were able to infer the One half of the block of rock in which the ammonite was
functions of the muscles and organs. discovered. Credit: Cherns et al.
The arrangement and relative strength of the
muscles suggests ammonites swam by expelling
water through their hyponomes, found next to the The study's lead author Dr. Lesley Cherns of
opening to the body chamber. This type of Cardiff University said: "Preservation of soft parts is
swimming, called jet propulsion, is used by a wide exceptionally rare in ammonites, even in
range of living animals, including cephalopods—the comparison to fossils of closely related animals like
larger group to which ammonites belong. squid. We found evidence for muscles that are not
present in Nautilus, which provided important new
The imaging also revealed paired muscles insights into the anatomy and functional
extending from the ammonite's body, likely used to morphology of ammonites."
retract the animal deep into the body chamber for
protection. This would have been an important anti- The findings demonstrate that combining different
predator adaptation in ammonites, which lacked imaging techniques can be highly effective for
defensive features like the ink sac seen in modern investigating fossil soft tissues, highlighting exciting
relatives like octopuses, squid, and cuttlefish. possibilities for studying the internal structure of
well-preserved specimens.
Patience yields results
Dr. Spencer added: "Despite being discovered over
Because ammonites' soft tissues are rarely 20 years ago, scientists have resisted the
2/3
destructive option of cutting it apart to see what's
inside. Although this would have been much
quicker, it risked permanent loss of some
information. Instead, we waited until non-
destructive technology caught up—as it now has.
This allowed us to understand these interior
structures without causing this unique and rare
fossil any damage.
"This result is a testament to both the patience
shown and the amazing ongoing technological
advances in paleontology."
More information: Lesley Cherns et al,
Correlative tomography of an exceptionally
preserved Jurassic ammonite implies hyponome-
propelled swimming, Geology (2021). DOI:
10.1130/G49551.1
Provided by Imperial College London
APA citation: Never-before-seen ammonite muscles revealed in 3D from Jurassic fossil (2021,
December 8) retrieved 22 June 2022 from https://phys.org/news/2021-12-never-before-seen-ammonite-
muscles-revealed-3d.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.
3/3
Powered by TCPDF (www.tcpdf.org)
You can also read
