Hallucigenia
Encyclopedia
Hallucigenia is an extinct genus
of animal
found as fossils in the Middle Cambrian
-aged Burgess Shale
formation of British Columbia
, Canada
, represented by the species H. sparsa, and in the Lower Cambrian Maotianshan shale of China
, represented by the species H. fortis. The genus name was coined by Simon Conway Morris
when he re-examined the various specimens of Charles Walcott's Burgess Shale worm genus Canadia
in 1979. Conway Morris found that what Walcott had called one genus in fact included several quite different animals. One of them was so unusual that nothing about it made much sense. Since the species clearly was not a polychaete worm, Conway Morris had to provide a new generic name to replace Canadia. Conway Morris named the species Hallucigenia sparsa because of its "bizarre and dream-like quality" (like a hallucination
). Hallucigenia was initially considered by Stephen Jay Gould
to be unrelated to any living species, but most palaeontologists now believe that the species was a relative of modern arthropods.
Faced with an animal that had no obvious head and two types of appendages, neither of which seemed appropriate for any reasonable form of locomotion, Morris assigned the blob as the head and hypothesized that the spines were legs and that the tentacles were feeding appendages. Morris was able to demonstrate a workable, if improbable, method of walking on the spines. Only the forward tentacles could easily reach to the 'head', meaning that a mouth on the head would have to be fed by passing food along the line of tentacles. Morris suggested that a hollow tube within each of the tentacles might be a mouth. This raised questions such as how it would walk on the stiff legs, but it was accepted as the best available interpretation. A picture of the animal as reconstructed by Morris can be found at Yvonne Navarro
's website.
An alternative interpretation considered Hallucigenia to be an appendage of a larger, unknown animal. There had been precedent for this, as the species Anomalocaris
had been originally identified as three separate creatures before being identified as a single huge (for its time) 3 foot (0.9144 m) creature. Given the uncertainty of its taxonomy, Hallucigenia was tentatively placed within the phylum Lobopodia
, a catch-all clade
containing numerous odd "worms with legs."
In 1991, Lars Ramskold and Hou Xianguang, working with additional specimens of a "hallucigenid," Microdictyon
, from the lower Cambrian
Maotianshan shales
of China, reinterpreted Hallucigenia as an Onychophore (velvet worm). They inverted it, interpreting the tentacles, which they believe to be paired, as walking structures and the spines as protective. Interestingly, none of the 30 or so known Burgess Shale specimens shows any sign of pairing in the large tentacles; nor do their Chinese counterparts. The pairing is based on a dissection of the actual fossil, which revealed what is probably a second tentacle structure. Ramskold and Hou also believe that the blob-like 'head' is actually a stain
that appears in many specimens, not a preserved portion of the anatomy.
Though Ramskold and Hou's is the accepted modern interpretation, it is far from problem-free. Unlike its contemporary Aysheaia
, Hallucigenia has very little resemblance to modern Onychophora. The elongated, and clawed legs bear little resemblance to the paired annulated legs of the Onychophora. It is unknown what the spines were made of and how much 'protection' they offered. They do not seem to be preserved independent of the soft-shelled animals as carbonate
or chitin
ous shells would probably be. It is not easy to explain why 30 or more specimens — each hypothesized to have seven pairs of rather long, flexible legs — do not show even one example of paired legs. But at least this reconstruction of the animal can plausibly walk, and the spines serve a reasonable purpose. A picture of this reconstruction as well as a photograph of an actual fossil can be seen on the Geological Survey of Canada's website.
Some paleontologists accept Ramskold and Hou's interpretation of the animal's legs, spines, and head, but also believe that Hallucigenia might be an "armored lobopod" related to Anomalocaris
. This does not rule out this bizarre creature also being related to the Onychophora, but rather may point to it coming from some time during or near the split of the two closely related groups.
In 2002, Desmond Collins suggested that new Hallucigenia fossils showed male and female forms, one with "a rigid trunk, robust neck and a globular head" and the other thinner, and with a small head.
robotics, a Japanese technology company, took inspiration from the Hallucigenia's unique anatomy in designing their Hallucigenia-I and Halluc-II concept vehicles. Working prototypes of these vehicles, which have 8 wheels on the end of 8 robotic appendages, can move in any direction and can climb over uneven terrain.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
found as fossils in the Middle Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
-aged Burgess Shale
Burgess Shale
The Burgess Shale Formation, located in the Canadian Rockies of British Columbia, is one of the world's most celebrated fossil fields, and the best of its kind. It is famous for the exceptional preservation of the soft parts of its fossils...
formation of British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, represented by the species H. sparsa, and in the Lower Cambrian Maotianshan shale of China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, represented by the species H. fortis. The genus name was coined by Simon Conway Morris
Simon Conway Morris
Simon Conway Morris FRS is an English paleontologist made known by his detailed and careful study of the Burgess Shale fossils, an exploit celebrated in Wonderful Life by Stephen Jay Gould...
when he re-examined the various specimens of Charles Walcott's Burgess Shale worm genus Canadia
Canadia (genus)
Canadia is a genus of extinct annelid worm present in Burgess Shale type Konservat-Lagerstätte. It is found in strata dating back to the Delamaran stage of the Middle Cambrian around 505 million years ago, during the time of the Cambrian explosion. It was about 3 centimeters in length...
in 1979. Conway Morris found that what Walcott had called one genus in fact included several quite different animals. One of them was so unusual that nothing about it made much sense. Since the species clearly was not a polychaete worm, Conway Morris had to provide a new generic name to replace Canadia. Conway Morris named the species Hallucigenia sparsa because of its "bizarre and dream-like quality" (like a hallucination
Hallucination
A hallucination, in the broadest sense of the word, is a perception in the absence of a stimulus. In a stricter sense, hallucinations are defined as perceptions in a conscious and awake state in the absence of external stimuli which have qualities of real perception, in that they are vivid,...
). Hallucigenia was initially considered by Stephen Jay Gould
Stephen Jay Gould
Stephen Jay Gould was an American paleontologist, evolutionary biologist, and historian of science. He was also one of the most influential and widely read writers of popular science of his generation....
to be unrelated to any living species, but most palaeontologists now believe that the species was a relative of modern arthropods.
Description and investigation
The 0.5 to 3 cm-long animal is wormlike — that is, long and narrow — with a poorly defined blob, or stain, on one end. This "blob" was arbitrarily designated the 'head' even though it had none of the features generally associated with heads: mouth, eyes, or other sensory organs. According to Morris' original interpretation, the animal has seven pincer-tipped tentacles lined up on one side and seven pairs of jointed spines on the other. Six of the tentacles were paired with spines, with one in front of the spines. There were also six smaller tentacles which may be configured in three pairs behind the seven larger ones. In addition, the body continued with a flexible, tube-like, tail-like extension behind the tentacles.Faced with an animal that had no obvious head and two types of appendages, neither of which seemed appropriate for any reasonable form of locomotion, Morris assigned the blob as the head and hypothesized that the spines were legs and that the tentacles were feeding appendages. Morris was able to demonstrate a workable, if improbable, method of walking on the spines. Only the forward tentacles could easily reach to the 'head', meaning that a mouth on the head would have to be fed by passing food along the line of tentacles. Morris suggested that a hollow tube within each of the tentacles might be a mouth. This raised questions such as how it would walk on the stiff legs, but it was accepted as the best available interpretation. A picture of the animal as reconstructed by Morris can be found at Yvonne Navarro
Yvonne Navarro
Yvonne Navarro is an American author who has published over twenty books. Of those twenty, the titles AfterAge, deadrush, Final Impact, Red Shadows, DeadTimes, That's Not My Name and Mirror Me were solo novels, or fiction created solely by her...
's website.
An alternative interpretation considered Hallucigenia to be an appendage of a larger, unknown animal. There had been precedent for this, as the species Anomalocaris
Anomalocaris
Anomalocaris is an extinct genus of anomalocaridid, which are, in turn, thought to be closely related to the arthropods. The first fossils of Anomalocaris were discovered in the Ogygopsis Shale by Joseph Frederick Whiteaves, with more examples found by Charles Doolittle Walcott in the famed...
had been originally identified as three separate creatures before being identified as a single huge (for its time) 3 foot (0.9144 m) creature. Given the uncertainty of its taxonomy, Hallucigenia was tentatively placed within the phylum Lobopodia
Lobopodia
Lobopodia is a group of poorly understood animals, which mostly fall as a stem group of arthropods. Their fossil range dates back to the Early Cambrian. Lobopods are segmented and typically bear legs with hooked claws on their ends....
, a catch-all clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
containing numerous odd "worms with legs."
In 1991, Lars Ramskold and Hou Xianguang, working with additional specimens of a "hallucigenid," Microdictyon
Microdictyon
Microdictyon is an extinct "armored worm" coated with dot-likescleritic scales, known from the Early CambrianMaotianshan shale of Yunnan China. Microdictyon is sometimes included...
, from the lower Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
Maotianshan shales
Maotianshan shales
The Maotianshan Shales are a series of lower Cambrian deposits in the Chiungchussu formation, famous for their Konservat Lagerstätten, or high number of fossils preserved in place...
of China, reinterpreted Hallucigenia as an Onychophore (velvet worm). They inverted it, interpreting the tentacles, which they believe to be paired, as walking structures and the spines as protective. Interestingly, none of the 30 or so known Burgess Shale specimens shows any sign of pairing in the large tentacles; nor do their Chinese counterparts. The pairing is based on a dissection of the actual fossil, which revealed what is probably a second tentacle structure. Ramskold and Hou also believe that the blob-like 'head' is actually a stain
Dark stain
A dark stain is often associated with fossils of the Burgess Shale, representing decay fluids that were squashed out of the organism during the taphonomic process.-Occurrence:...
that appears in many specimens, not a preserved portion of the anatomy.
Though Ramskold and Hou's is the accepted modern interpretation, it is far from problem-free. Unlike its contemporary Aysheaia
Aysheaia
Aysheaia was a genus of soft-bodied, caterpillar-shaped organisms average body length of 1–6 cm. The genus name commemorates a mountain peak named "Ayesha" due north of the Wapta Glacier. This peak was originally named Aysha in the 1904 maps of the region, and was re-named Ayesha after the heroine...
, Hallucigenia has very little resemblance to modern Onychophora. The elongated, and clawed legs bear little resemblance to the paired annulated legs of the Onychophora. It is unknown what the spines were made of and how much 'protection' they offered. They do not seem to be preserved independent of the soft-shelled animals as carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
or chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
ous shells would probably be. It is not easy to explain why 30 or more specimens — each hypothesized to have seven pairs of rather long, flexible legs — do not show even one example of paired legs. But at least this reconstruction of the animal can plausibly walk, and the spines serve a reasonable purpose. A picture of this reconstruction as well as a photograph of an actual fossil can be seen on the Geological Survey of Canada's website.
Some paleontologists accept Ramskold and Hou's interpretation of the animal's legs, spines, and head, but also believe that Hallucigenia might be an "armored lobopod" related to Anomalocaris
Anomalocaris
Anomalocaris is an extinct genus of anomalocaridid, which are, in turn, thought to be closely related to the arthropods. The first fossils of Anomalocaris were discovered in the Ogygopsis Shale by Joseph Frederick Whiteaves, with more examples found by Charles Doolittle Walcott in the famed...
. This does not rule out this bizarre creature also being related to the Onychophora, but rather may point to it coming from some time during or near the split of the two closely related groups.
In 2002, Desmond Collins suggested that new Hallucigenia fossils showed male and female forms, one with "a rigid trunk, robust neck and a globular head" and the other thinner, and with a small head.
Robotic application
FuRoFuro
is a Japanese word for bath. Specifically it is used to refer to a type of bath which originated as a short, steep-sided wooden bathtub. Baths of this type are found all over Japan in houses, apartments and traditional Japanese inns but are now usually made out of a plastic or stainless steel.A...
robotics, a Japanese technology company, took inspiration from the Hallucigenia's unique anatomy in designing their Hallucigenia-I and Halluc-II concept vehicles. Working prototypes of these vehicles, which have 8 wheels on the end of 8 robotic appendages, can move in any direction and can climb over uneven terrain.
External links
- http://www.nmnh.si.edu/paleo/shale/phallu.htm - (Internet ArchiveInternet ArchiveThe Internet Archive is a non-profit digital library with the stated mission of "universal access to all knowledge". It offers permanent storage and access to collections of digitized materials, including websites, music, moving images, and nearly 3 million public domain books. The Internet Archive...
) - http://www.arrakis.es/~owenwang/articulos/pasados.htm (Spanish)