Named By: Alexander Petrovich Karpinsky - 1899.
Classification: Chordata, Chondrichthyes, Eugeneodontida, Agassizodontidae.
Species: H. bessonovi (type), H. davisii, H. ergasaminon, H. ferrieri, H. mexicanus, H. nevadensis, H. svalis.
Size: Uncertain but more recent estimates place larger Helicoprion at up to about 7.5 meters long. Many specimens are from smaller indviduals of about 3-4 meters long, suggesting a size variation between species.
Known locations: Australia - Wandagee Formation, Canada, Alberta - Ranger Canyon Formation, British Columbia - Fantasque Formation, Nunavut - Assistance Formation, China - Qixia Formation, Japan - Ochiai Formation andYagihawa limestone Formation, Kazakstan, Mexico - Patlanoaya Formation, Russia, USA, California - Goodhue Formation, Idaho - Phosphoria Formation, Montana - Phosphoria Formation, Nevada - Antler Peak Formation, Texas - Bone Spring Formation, Skinner Ranch Formation, Utah - Phosphoria Formation, Wyoming - Phosphoria Formation. The broad distribution of fossil locations suggests a global distribution.
Time period: Artinskian of the Permian through to the Carnian of the Triassic.
Fossil representation: Mostly only known from the 'tooth-whorls', at least one specimen has been preserved with crushed cartilage from the skull and jaw.
Helicoprion is one of the stranger 'sharks' in the fossil record, although at the time that Helicoprion swam the oceans there were actually many sharks that did not conform to the 'standard' form that we know today. The majority of the remains of this shark are the teeth which are fossilised in a spiral pattern like the shell of an ammonite, in fact when first discovered these fossils were actually thought to be some kind of exotic ammonite shell. These arrangements of fossil teeth are today referred to as a 'tooth-whorl'.
and where the tooth-whorl attached has been a source of puzzlement to
palaeoichthyologists ever since it was realised what it was, and
while the obvious choice might be to place the tooth-whorl within the
mouth, the whorl has on occasion been placed in different parts
including the dorsal fin and even the tail. Today the whorl is almost
always placed with the lower jaw, though for a long time not everyone
the exact location. If the whorl was mounted on the tip it would
significantly increase the drag that Helicoprion
experienced as it swam
through the water. Not only would it require more effort to swim,
the greater water turbulence would have revealed the presence of
Helicoprion to its potential prey. This is why
many people now
consider the whorl to have been further back into the mouth.
Then in 2013 a new study by Tapanila, Pruitt, Pradel, Wilga, Ramsay, Schlader and Didier was published, and this was a watershed moment in the study of Helicorpion as this was the first time that something other than the tooth whorl was studied; crushed cartilage that once formed the head and jaw. Although incomplete, the cartilage which was on a fossil found in Idaho in 1950 and officially described in 1966, was completely revealed by a CT scan which then enabled the researchers to use computer modelling to form a reconstruction of Helicoprion. This study led to a new depiction of Helicoprion with a tooth whorl within a shorter lower jaw.
Helicoprion used its whorl has also been another
matter of debate with
a variety of theories ranging from the whorl being used as a lash
against fish, to a rasp that cut its way through the shells of
ammonites with a sawing motion. However even a casual look at the
fossil tooth whorls reveals that the teeth have a surprising little
amount of wear, and since Helicoprion and
relative genera are not
thought to have had such a fast replacement of teeth modern day
sharks, there is now new speculation that Helicoprion
of soft bodied organisms such as molluscs, especially cephalopods
such as octopuses.
It may now only be a matter of time before more cartilaginous remains of Helicoprion are discovered, as other creatures with cartilaginous remains from genera such as Cladoselache, Fadenia and Stethacanthus amongst a growing number of many others are being found.
- Ueber die Reste von Edestiden und die neue Gattung Helicoprion. - Verhandlungen der Kaiserlichen Russischen Mineralogischen Gesellschaft zu St. Petersburg, Zweite Series 36:1-111 - A. Karpinsky - 1899.
- A new genus and species of fossil shark related to Edestus Leidy. - Science 26(653):22-24 - O. P. Hay - 1907.
- Helicoprion ivanovi, n. sp. Bulletin de l'Academie des Sciences de Russie 16:369-378 - A. Karpinsky - 1922.
- Helicoprion in the Anthracolithic (Late Paleozoic) of Nevada and California, and its stratigraphic significance. - Journal of Paleontology 13(1):103-114 - Harry E. Wheeler - 1939.
- Helicoprion from Elko County, Nevada. - Journal of Paleontology 29 (5): 918–919. - E. R. Larson & J. B. Scott - 1955.
- New investigations on Helicoprion from the Phosphoria Formation of South-east Idaho, USA. - Kongelige Danske Videnskabernes Selskab, Biologiske Skrifter 14(5):1-54 - S. E. Bendix-Almgreen - 1966.
- The first record of Helicoprion Karpinsky (Helicoprionidae) from China. - Chinese Science Bulletin 52 (16): 2246–2251. - Xiao-Hong Chen, Long Cheng, Kai-Guo Yin - 2007.
- The Orthodonty of Helicoprion. - National Museum of Natural History. Smithsonian Institution. p. 1. - Robert W. Purdy - 2008.
- A new specimen of Helicoprion Karpinsky, 1899 from Kazakhstanian Cisurals and a new reconstruction of its tooth whorl position and function. - Acta Zoologica 90: 171–182. - O. A. Lebedev - 2009.
- Jaws for a spiral-tooth whorl: CT images reveal novel adaptation and phylogeny in fossil Helicoprion. - Biology Letters 9 (2): 20130057 - L. Tapanila, J. Pruitt, A. Pradel, C. D. Wilga, J. B. Ramsay, R. Schlader & D. A. Didier - 2013.
- Unravelling species concepts for the Helicoprion tooth whorl. - Journal of Paleontology. 87 (6): 965–983. - L. Tapanila & J. Pruitt - 2013.
- Eating with a saw for a jaw: Functional morphology of the jaws and tooth-whorl in Helicoprion davisii: Jaw and Tooth Function in Helicoprion. - Journal of Morphology. 276 (1): 47–64. - Jason B. Ramsay, Cheryl D. Wilga, Leif Tapanila, Jesse Pruitt, Alan Pradel, Robert Schlader, & Dominique A. Didier - 2014.
- Saws, Scissors, and Sharks: Late Paleozoic Experimentation with Symphyseal Dentition. - The Anatomical Record. 303 (2): 363–376. - Leif Tapanila, Jesse Pruitt, Cheryl D. Wilga & Alan Pradel - 2020.