Anomalocaris
Name:
Anomalocaris
(Abnormal shrimp).
Phonetic: A-nom-ah-lo-ca-ris.
Named By: Joseph Frederick Whiteaves - 1892.
Synonyms: Anomalocaris lineata,
Anomalocaris nathorsti.
Classification: Arthropoda, Dinocaridida,
Radiodonta, Anomalocarida, Anomalocarididae.
Species: A. canadensis (type),
A.
briggsi, A. kunmingensis, A. magnabasis, A. pennsylvanica, A.
saron.
Diet: Carnivore.
Size: Specimens approach up to 50 centimetres long from head to
tip of tail (not including appendages). Some isolated remains have
indicated a larger size
for some species.
Known locations: Locations include, Australia,
Canada, China and the USA, indicating that Anomalcaris
potentially had a worldwide distribution.
Time period: Cambrian.
Fossil representation: Hundreds of specimens, though
often of isolated body parts.
Although
named in 1892, no one had any idea of the true identity of
Anomalocaris until towards the end of the twentieth
century. The
first specimen was originally thought to be a shrimp, but with
hindsight we now know this specimen to only represent one of the
frontal grasping appendages. The second clue was a mouth, although
this ended up being classified under the Peytoia
genus of jellyfish.
Not only does the fossilised mouth of Anomalocaris
look very much like
a jellyfish, it is also often referred to as a pineapple ring due to
its resemblance to a sliced pineapple. When discovered the body of
Anomalocaris was thought to be a sponge of the Laggania
genus.
Then
fossils started to occur where all of the parts were together,
although the usual identification would be along the lines of a
jellyfish preserved against a sponge, not a mouth connected to a
body. Eventually however they were pieced together and the
realisation came that these ‘composites’ were actually
representations of a single creature. Even though the creature was
nothing like it was first assumed to be, the name Anomalocaris
was
still valid because it was the first name assigned to a previously
unidentified specimen, the initial appendage. Peytoia
is now also a distinct genus of related anomolocarid.
Anomalocaris
is often termed a proto-arthropod, meaning that while it was of the
same lineage to arthropods, it may have been of a slightly
different evolutionary line as arthropods as we known them today.
Early on Anomalocaris was often depicted with a
hard chitinous body
like say a crab shell, but today it seems that this might not be
correct. The hardest parts seem to have been the forward appendages
and the mouth, hence the reason why fossils of these parts are fairly
common in relation to the preservation of the other parts. The main
body itself seems to have been softer in relation to these parts,
with lobes extending from the sides of the main body. These lobes
grew in such a way so that even though they were separate, each lobe
would be so large that it would grow under the one to the rear of it,
creating a more ‘complete’ surface to push against the water.
Modelling of undulating patterns that these lobes would have moved
in has revealed that this form of locomotion would have offered very
stable and efficient swimming with little need to move the main body.
Most
of the known creatures of the Cambrian seas were very small, but
Anomalocaris was a clear exception to this rule. Anomalocaris
Fossils
usually represent individuals between sixty and one hundred centimetres
in length.
When
depicted in popular culture and documentaries Anomalocaris
is often
depicted as an apex predator that chases after trilobites before
ripping them in two and crunching up the shells. However, some
people have questioned the classical view of Anomalocaris
crushing and
eating hard shelled arthropods because computer models have suggested
that Anomalocaris could not close its mouth
completely. Some also
point to the lack of hard prey shells that have not been found in
association with Anomalocaris specimens. While
the appendages at the
front could have been used for tearing, the spines that are
underneath might have conceivably been used for filtering sediment and
trapping smaller prey. Once prey was found, the appendage would
curl round to pass the food into its mouth. Such a feeding method
would not require the mouth to close fully, just enough to make
contact with the appendage. It is also worth noting that the tooth
like prongs of the mouth also extend inwards towards the gullet,
perhaps to cover the length of the inserted appendage, although this
feature only reveals the feeding method, not the diet.
Before
you decide whether Anomalocaris was some kind of
filter feeder instead
of an active apex predator, you have to take into account the
nutritional value of a trilobites shell, as well as the fact that
trilobites would have been soft on the inside. It’s just as likely
that this sucking mouth could have been used to suck the soft trilobite
flesh from their shells, with both feeding lifestyles being possible.
Anomalocris
is now the type genus of the Anomalocarida,
a whole group of
creatures similar to Anomalacris.
Further reading
- Anomalocaris, the largest known Cambrian
arthropod. - Palaeontology
vol 22, part 3, pp631-66. - D. E. G. Briggs - 1979.
- The Occurrence of the Giant Arthropod Anomalocaris
in the Lower
Cambrian of Southern California, and the Overall Distribution of the
Genus. - Journal of Paleontology 56 (5): 1112–8. - D. E. G. Briggs
& J. D. Mount - 1982.
- Exceptionally preserved nontrilobite arthropods and Anomalocaris
from
the Middle Cambrian of Utah. - University of Kansas Paleontological
Contributions (111). - D. E. G. Briggs & R. A. Robison - 1984.
- The largest Cambrian animal, Anomalocaris,
Burgess Shale, British
Columbia. - Philosophical Transactions of the Royal Society B 309
(1141): 569–609. - H. B. Whittington & D. E. G. Briggs - 1985.
- Anomalocaris and other large animals in the Lower
Cambrian Chengjiang
fauna of southwest China. - Geologiska F�reningens i Stockholm
Forhandlingar 117:163-183. - X.-G. Hou, J. Bergstr�m & P.
Ahlberg - 1995.
- Anomalocaris predation on nonmineralized and
mineralized trilobites.
- Geology 27 (11). - C. Nedin - 1999.
- Theoretical study on the body form and swimming pattern of
Anomalocaris based on hydrodynamic simulation. -
Journal of Theoretical
Biology 238 (1): 11–7. - Yoshiyuki Usami - 2006.
- Acute vision in the giant Cambrian predator Anomalocaris
and the
origin of compound eyes. - Nature 480 (7376). - John R. Paterson, Diego
C. Garc�a-Bellido, Michael S. Y. Lee, Glenn A. Brock, James B. Jago
& Gregory D. Edgecombe - 2011.
- The oral cone of Anomalocaris is not a classic 'Peytoia'.
-
Naturwissenschaften. - A. Daley & J. Bergstr�m - 2012.
- New anatomical information on Anomalocaris from
the Cambrian Emu Bay
Shale of South Australia and a reassessment of its inferred predatory
habits. - Palaeontology. - A. C. Daley, J. R. Paterson, G. D.
Edgecombe, D. C. Garcia-Bellido & J. B. Jago (Philip Donoghue,
ed.). - 2013.
- Arthropod appendages from the Weeks Formation Konservat-Lagerst�tte:
new occurrences of anomalocaridids in the Cambrian of Utah, USA. -
Bulletin of Geosciences: 269–282. R. Lerosey-Aubril, T. A. Hegna, L. E.
babcock, E. Bonino & C. Kier - 2014.
- On the Hydrodynamics of Anomalocaris Tail Fins. -
Integrative and
Comparative Biology. 58 (4): 703–711. - K. A. Sheppard, D. E. Rival
& J.B. caron - 2018.
- Exceptional multifunctionality in the feeding apparatus of a
mid-Cambrian radiodont. - Paleobiology. 47 (4): 704–724.. - J. Moysiuk
& J. B. Caron - 2021.
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