Anomalocarid
Encyclopedia
AnomalocarididsNeolatin compound word from Greek ἀνώμαλος anomalos and καρίς karis (gen.: καρίδος), meaning "strange shrimp
". Note that while "Anomalocarid" is a widely used alternative spelling, the double "id" at the end is technically the correct form, for the reasons given in . are a group of very early marine animals known primarily from fossils found in Cambrian
deposits in China
, USA, Canada
, Poland
and Australia
. They were long thought to be restricted to this range, but the discovery of large Ordovician
specimens extended this somewhat. The later Devonian
Schinderhannes
, a great appendage arthropod that retains many anomalocaridid features, extended their record by some hundred million years — their non-mineralised nature means they are absent from the intermediate fossil record. Anomalocarids are the largest Cambrian animals known — some Chinese forms may have reached 2 m (7 ft) in length — and most of them were probably active carnivore
s.
. The mouth was a circular structure resembling a pineapple
slice, but with a ring of hard sharp teeth in the central orifice. The mouth was more rectangular than round, and the teeth did not meet in the middle. It has been hypothesised that the mouth enabled anomalocaridids to eat hard-shelled organisms such as trilobites; for a full discussion of this matter, see Anomalocaris
. Anomalocarids also had large eyes and a body half-flanked with a series of swimming lobes.
Parapeytoia yunnanensis, one species of anomalocaridid (many scientists debate whether or not Parapeytoia was a true anomalocaridid, or rather more closely related to Yohoia
or Haikoucaris), may even have had legs.
Compared with many of the other sea-dwelling creatures of its time, anomalocaridids were extremely agile. The flaps along its body could probably be moved in a wave-like formation, allowing it to move at great speeds or to 'hover'. This motion could be compared to present-day Batoidea
(rays), or perhaps cuttlefish
. The cuticle of the anomalocaridids was more flexible than those of its prey, allowing it easier movement.
After death this large organism tended to disintegrate and fall apart into separate pieces; the same happened to its moulted skins
. Completely intact fossil remains are very rare. When the fossils were originally described, the jointed arms in front of the mouth were classified as separate arthropods (precipitating quite a mystery; the fossils were mistakenly identified as "shrimp
", but always with their "heads" missing), the mouth was thought to have been a fossilized jellyfish
called "Peytoia", and the body, thought to be a sponge named "Laggania" was not associated with either. Since the pieces were reassembled in the 1980s, a number of genera
and species
have been described that differ in the details of the grasping appendages, as to whether a tail is present, mouth location, and other features.
The name Anomalocaris (meaning "strange shrimp") originally referred to the detached arms (which were the first part to be named), and was later used for the whole animal because of the biological name priority rules
. Curiously enough, when fully assembled, these animals outwardly resemble a gigantic brine shrimp
with a pair of finger-like appendages near its mouth.
The anomalocaridids thrived in the Early and Mid Cambrian
, and are rarer in later deposits mainly due to the scarcity of post-Cambrian lagerstatten.
, Laggania
, Schinderhannes
, Amplectobelua
and Hurdia
. A variety of other related animals including Parapeytoia
, Pambdelurion and Kerygmachela are sometimes classified as anomalocarids, but probably belong to different clades. Anomalocaridids are quite common throughout the Cambrian, and are known from the earliest Burgess shale-type fauna, in the early Cambrian of Poland, predating the first appearance of trilobites.
Compared with Anomalocaris species, Laggania species lacked tail structures and had a considerably larger head with the eyes placed behind instead of in front of the mouth, which would have been disadvantagous for active hunting. Because of these characteristics, some scientists have described Laggania as a cruising, plankton feeder. Amplectobelua species, in contrast to Anomalocaris, were smaller and had a much wider body front with eyes placed lateral to the mouth.
The anomalocarids appear to be closely related to the opabinidids
, and they fall somewhere in the arthropod stem. The discovery of a Devonian anomalocarid suggests that the group is a paraphyletic group, containing the arthropods.
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
". Note that while "Anomalocarid" is a widely used alternative spelling, the double "id" at the end is technically the correct form, for the reasons given in . are a group of very early marine animals known primarily from fossils found in 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...
deposits in 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...
, USA, 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...
, Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
and Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. They were long thought to be restricted to this range, but the discovery of large Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
specimens extended this somewhat. The later Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
Schinderhannes
Schinderhannes bartelsi
Schinderhannes bartelsi is an anomalocarid known from one specimen from the lower Devonian Hunsrück Slates. Its discovery was astonishing because previously, anomalocaridids had only been known from exceptionally preserved fossil beds from the Cambrian, 100 million years earlier.Anomalocaridids...
, a great appendage arthropod that retains many anomalocaridid features, extended their record by some hundred million years — their non-mineralised nature means they are absent from the intermediate fossil record. Anomalocarids are the largest Cambrian animals known — some Chinese forms may have reached 2 m (7 ft) in length — and most of them were probably active carnivore
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
s.
Characteristics
Anomalocaridids were flat, free-swimming, segmented animals that possessed two appendages in front of their mouths that resembled the bodies of shrimpShrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
. The mouth was a circular structure resembling a pineapple
Pineapple
Pineapple is the common name for a tropical plant and its edible fruit, which is actually a multiple fruit consisting of coalesced berries. It was given the name pineapple due to its resemblance to a pine cone. The pineapple is by far the most economically important plant in the Bromeliaceae...
slice, but with a ring of hard sharp teeth in the central orifice. The mouth was more rectangular than round, and the teeth did not meet in the middle. It has been hypothesised that the mouth enabled anomalocaridids to eat hard-shelled organisms such as trilobites; for a full discussion of this matter, see 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...
. Anomalocarids also had large eyes and a body half-flanked with a series of swimming lobes.
Parapeytoia yunnanensis, one species of anomalocaridid (many scientists debate whether or not Parapeytoia was a true anomalocaridid, or rather more closely related to Yohoia
Yohoia
Yohoia is a tiny, extinct animal from the Cambrian period that has been found as fossils in the Burgess Shale formation of British Columbia, Canada. It has been placed among the arachnomorphs, a group of arthropods that includes the chelicerates and trilobites. Their sizes range from 7 to 23 mm...
or Haikoucaris), may even have had legs.
Compared with many of the other sea-dwelling creatures of its time, anomalocaridids were extremely agile. The flaps along its body could probably be moved in a wave-like formation, allowing it to move at great speeds or to 'hover'. This motion could be compared to present-day Batoidea
Batoidea
Batoidea is a superorder of cartilaginous fish commonly known as rays and skates, containing more than 500 described species in thirteen families...
(rays), or perhaps cuttlefish
Cuttlefish
Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda . Despite their name, cuttlefish are not fish but molluscs....
. The cuticle of the anomalocaridids was more flexible than those of its prey, allowing it easier movement.
After death this large organism tended to disintegrate and fall apart into separate pieces; the same happened to its moulted skins
Ecdysis
Ecdysis is the moulting of the cuticula in many invertebrates. This process of moulting is the defining feature of the clade Ecdysozoa, comprising the arthropods, nematodes, velvet worms, horsehair worms, rotifers, tardigrades and Cephalorhyncha...
. Completely intact fossil remains are very rare. When the fossils were originally described, the jointed arms in front of the mouth were classified as separate arthropods (precipitating quite a mystery; the fossils were mistakenly identified as "shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
", but always with their "heads" missing), the mouth was thought to have been a fossilized jellyfish
Jellyfish
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
called "Peytoia", and the body, thought to be a sponge named "Laggania" was not associated with either. Since the pieces were reassembled in the 1980s, a number of genera
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...
and species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
have been described that differ in the details of the grasping appendages, as to whether a tail is present, mouth location, and other features.
The name Anomalocaris (meaning "strange shrimp") originally referred to the detached arms (which were the first part to be named), and was later used for the whole animal because of the biological name priority rules
Nomenclature Codes
Nomenclature codes or codes of nomenclature are the various rulebooks that govern biological taxonomic nomenclature, each in their own broad field of organisms...
. Curiously enough, when fully assembled, these animals outwardly resemble a gigantic brine shrimp
Brine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...
with a pair of finger-like appendages near its mouth.
The anomalocaridids thrived in the Early and Mid 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...
, and are rarer in later deposits mainly due to the scarcity of post-Cambrian lagerstatten.
Classification
Five genera of anomalocarids are known: AnomalocarisAnomalocaris
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...
, Laggania
Laggania
Laggania cambria was a species of Anomalocarid that lived in the Cambrian period. Its two mouth appendages had long bristle-like spines, it had no fan tail, and its short stalked eyes were behind its mouth appendages...
, Schinderhannes
Schinderhannes bartelsi
Schinderhannes bartelsi is an anomalocarid known from one specimen from the lower Devonian Hunsrück Slates. Its discovery was astonishing because previously, anomalocaridids had only been known from exceptionally preserved fossil beds from the Cambrian, 100 million years earlier.Anomalocaridids...
, Amplectobelua
Amplectobelua
Amplectobelua is an extinct genus of anomalocaridid, a group of very early marine animals. While completely different from any animal alive today, some scientists do believe that the very primitive anomalocarids were in fact somewhat related to arthropods...
and Hurdia
Hurdia
Hurdia victoria is an extinct species of anomalocaridid that lived 500 million years ago during the Cambrian era. It is part of the ancestral lineage that led to Arthropods and is related to Anomalocaris.-Description:...
. A variety of other related animals including Parapeytoia
Parapeytoia
Parapeytoia was a prehistoric animal that lived over 530 million years ago that lived in Maotianshan shales of prehistoric China. Like the anomalocarids that it resembled , Parapeytoia had two head appendages in front of the also anomalocarid like round mouth, eyes on stalks, and fleshy lobed...
, Pambdelurion and Kerygmachela are sometimes classified as anomalocarids, but probably belong to different clades. Anomalocaridids are quite common throughout the Cambrian, and are known from the earliest Burgess shale-type fauna, in the early Cambrian of Poland, predating the first appearance of trilobites.
Compared with Anomalocaris species, Laggania species lacked tail structures and had a considerably larger head with the eyes placed behind instead of in front of the mouth, which would have been disadvantagous for active hunting. Because of these characteristics, some scientists have described Laggania as a cruising, plankton feeder. Amplectobelua species, in contrast to Anomalocaris, were smaller and had a much wider body front with eyes placed lateral to the mouth.
The anomalocarids appear to be closely related to the opabinidids
Opabinia
Opabinia is an animal genus found in Cambrian fossil deposits. Its sole species, Opabinia regalis, is known from the Middle Cambrian Burgess Shale of British Columbia, Canada. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed,...
, and they fall somewhere in the arthropod stem. The discovery of a Devonian anomalocarid suggests that the group is a paraphyletic group, containing the arthropods.
See also
- CassubiaCassubiaCassubia is an anomalocaridid-like genus from the Early Cambrian of Poland....
- Kerygmachela
- OpabiniaOpabiniaOpabinia is an animal genus found in Cambrian fossil deposits. Its sole species, Opabinia regalis, is known from the Middle Cambrian Burgess Shale of British Columbia, Canada. Fewer than twenty good specimens have been described; 3 specimens of Opabinia are known from the Greater Phyllopod bed,...
- Pambdelurion
- Walking with MonstersWalking with MonstersWalking with Monsters is a three-part British documentary film series about life in the Paleozoic, bringing to life extinct arthropods, fish, amphibians, synapsids, and reptiles...