Dinomischus
Encyclopedia
Dinomischus is a rare fossil animal from the Cambrian
period. It reached 100 mm in height, was attached to the sea floor by a stalk, and looked loosely like a flower. The cup-shaped body at the top of the stalk probably fed by filtering
the surrounding seawater, and may have created a current to facilitate this. Its mouth and anus sat next to one another.
In his pioneering excavations of the Burgess shale
, Charles Doolittle Walcott
excavated the first, and at the time only, specimen. It had evidently caught his eye, for he had taken the trouble to carefully photograph it - but he never found the time to describe the organism, and it was not until 1977 that Simon Conway Morris
described the animal. He tracked down two further specimens, collected by further expeditions by teams from Harvard and the Royal Ontario Museum, allowing him to produce a reconstruction.
He was not able to say much about the organism. It consisted of a calyx (or body) on a long, thin stalk, surrounded by a whorl of 18 short "petals" which enclosed both openings of its U-shaped gut. The presence of this gut identified it as a metazoan, and the stem implied that it lived permanently attached to the sea floor by a small holdfast. The twenty or so "petals" borne by each organism were solid, plate-like structures, about two thirds the length of the calyx. It is speculated that they may have been covered with cilia - fine hairs - which would have wafted food down towards the organism's mouth. A number of affinities were considered, but on the basis of available evidence it didn't quite seem to fit into any extant phylum.
The most similar organisms were the much smaller entoprocts, but even these modern organisms are difficult to classify.
Further specimens have since been produced by similarly spectacular fossil sites in China. 13 have been found in the Chengjiang, then in 2006 one specimen was identified within the Kaili biota. These organisms merited the erection of a new species, D. venustus, as their corrugated "petals" possessed radial rays. However, these new data have added little to the debate; while a suggestion of echinoderm affinity has been floated, no phyla are compellingly similar to the organism.
Other modern ideas, even if a little tenuous, include a suggestion that the organism may have been parasitic, dwelling on the carapaces of larger organisms.
Dinomischus is not the only organism of its kind in the Cambrian; a similar, larger organism known as the "tulip animal" has also been recovered, but not yet described, from the Burgess shale
. It has also been likened to Eldonia
and Velumbrella
, although unlike Dinomischus these medusoid organisms have tentacles.
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...
period. It reached 100 mm in height, was attached to the sea floor by a stalk, and looked loosely like a flower. The cup-shaped body at the top of the stalk probably fed by filtering
Filter feeder
Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...
the surrounding seawater, and may have created a current to facilitate this. Its mouth and anus sat next to one another.
In his pioneering excavations of the 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...
, Charles Doolittle Walcott
Charles Doolittle Walcott
Charles Doolittle Walcott was an American invertebrate paleontologist. He became known for his discovery in 1909 of well-preserved fossils in the Burgess Shale of British Columbia, Canada.-Early life:...
excavated the first, and at the time only, specimen. It had evidently caught his eye, for he had taken the trouble to carefully photograph it - but he never found the time to describe the organism, and it was not until 1977 that 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...
described the animal. He tracked down two further specimens, collected by further expeditions by teams from Harvard and the Royal Ontario Museum, allowing him to produce a reconstruction.
He was not able to say much about the organism. It consisted of a calyx (or body) on a long, thin stalk, surrounded by a whorl of 18 short "petals" which enclosed both openings of its U-shaped gut. The presence of this gut identified it as a metazoan, and the stem implied that it lived permanently attached to the sea floor by a small holdfast. The twenty or so "petals" borne by each organism were solid, plate-like structures, about two thirds the length of the calyx. It is speculated that they may have been covered with cilia - fine hairs - which would have wafted food down towards the organism's mouth. A number of affinities were considered, but on the basis of available evidence it didn't quite seem to fit into any extant phylum.
The most similar organisms were the much smaller entoprocts, but even these modern organisms are difficult to classify.
Further specimens have since been produced by similarly spectacular fossil sites in China. 13 have been found in the Chengjiang, then in 2006 one specimen was identified within the Kaili biota. These organisms merited the erection of a new species, D. venustus, as their corrugated "petals" possessed radial rays. However, these new data have added little to the debate; while a suggestion of echinoderm affinity has been floated, no phyla are compellingly similar to the organism.
Other modern ideas, even if a little tenuous, include a suggestion that the organism may have been parasitic, dwelling on the carapaces of larger organisms.
Dinomischus is not the only organism of its kind in the Cambrian; a similar, larger organism known as the "tulip animal" has also been recovered, but not yet described, from the 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...
. It has also been likened to Eldonia
Eldonia
Eldonia is a soft-bodied animal of unknown affinity, best known from the Fossil Ridge outcrops of the Burgess Shale, particularly in the 'Great Eldonia layer' in the Walcott Quarry...
and Velumbrella
Velumbrella
Velumbrella is a medusoid organism with tentacles known from the Middle Cambrian of Poland, and perhaps related to Rotadiscus; it's a scleritosed disk with a U-shaped gut. It was originally related to members of the Ediacara biota but is now thought to be related to the paropsonemids....
, although unlike Dinomischus these medusoid organisms have tentacles.