Anomalocaridid
Reconstruction of Laggania cambria
The Anomalocarididae (Greek ἀνώμαλος anomalos and καρίς karis (Gen.: καρίδος ) " unusual shrimp " ) are a group of marine animals that are very early mainly of fossils from the Cambrian deposits in China, the USA, Canada, Poland and Australia known. Although colloquially is often spoken of " Anomalocarida " or " Anomalocariden " represents the name Anomalocarididae or " Anomalocarididen " the technically correct term
For a long time it was assumed that Anomalocarididen died out at the end of the Cambrian, but the discovery of a large specimen from Morocco has shown that representatives of Anomalocarididae survived at least into the Ordovician. The discovery of frühdevonischen Schinderhannes bartelsi, an arthropod with large appendages and a number of anomalocarididen features, expanded to 100 million years to the early Devonian 400 million years ago, the stratigraphic range of the Anomalocarididen beyond. The unmineralisierte body composition of the animals has the consequence that in intervening geological layers no fossils have been preserved. Anomalocarididen were the biggest known animals of the Cambrian - some Chinese species probably reached a length of two meters - and most forms were probably active predators.
Features
The floating in open water Anomalocarididen had flat, segmented body, which were equipped with two spiked gripping arms in front of the mouth, recalls the shape of the body of shrimp. The mouth opening had a circular structure, resembling a slice of pineapple. The mouth was filled with a ring of sharp plates, but did not touch in the middle, because the mouth opening was rectangular rather than round. It has been suggested that these teeth have enabled some Anomalocarididen, to feed on hard-shelled trilobites. Anomalocarididen had big eyes and her body was flanked on each side, of a series of movable flap-like appendages, which served the movement in the water.
Parapeytoia yunnanensis, which must probably be asked to Anomalocarididen, ( whether Parapeytoia was one of the real Anomalocarididae or was rather more closely related to Yohoia or Haikoucaris is controversial in science) could have had legs.
Compared to many other creatures meeresbewohnenden his time Anomalocarididen were very mobile. The flap-like extensions on the body flanks were likely to be wavy moved so that the animals were able to move fast or to float in the water. This type of locomotion is similar to that of modern Batoidea (skates and rays ) or the cuttlefish. The cuticle of the Anomalocarididen was more flexible than that of their prey, thus allowing a greater freedom of movement.
After the death of the organism tended to disintegrate into several parts. Fully preserved fossils are therefore scarce. In the first description of the fossils of Anomalocaris you classified the hinged gripper arms first as a separate species of arthropods. Before the fossils could be assembled correctly, cared for the fact astonishment that the alleged shrimp were always found without a head. The round mouth opening was thought to be a fossil jellyfish which was provided with the generic name " Peytoia ". Also the body has been associated with the sponges under the name Laggania. Only in the 1980s, the three different fossils were assembled correctly. Since then a number of genera and species within the Anomalocarididae have been described, which differ mainly in the structure of the gripper arms, the presence of a tail, the position of the mouth, etc..
The name Anomalocaris originally denoted only the wrongly held for a shrimp gripping arms, but was later extended in accordance with the rules of biological nomenclature on the whole animal, since the fossil gripping arms were first described.
The Anomalocarididen experienced in the early and middle Cambrian blossom, fossil traditions from younger rock strata are rare, but this also with the lack of suitable deposits can be explained from a later period, as the soft body of the Anomalocarididen preserved only under special circumstances.
Classification
Within the Anomalocarididae exist ten genera, most of which are known only with some kind:
- Amplectobelua Amplectobelua symbrachiata
- Amplectobelua stephenensis
- Anomalocaris briggsi
- Anomalocaris canadensis
- Anomalocaris pennsylvanica
- Anomalocaris saron
- Caryosyntrips serratus
- Villa Leon infracambriensis
- Cucumericrus decoratus
- Hurdia victoria
- Laggania cambria
- Schinderhannes bartelsi
- Stanley Caris hirpex
- Tamisiocaris borealis
Some other related genera are sometimes asked to Anomalocarididae, but may belong to other clades:
- Jianshanopodia
- Kerygmachela
- Pambdelurion
- Parapeytoia
The already known from the earliest Cambrian faunas in Poland Anomalocarididae were widespread during the Cambrian and were still functioning before the trilobites.
Compared with the species of the genus Anomalocaris Laggania lacked a tail structure. The latter also had a larger head in which the eyes were placed behind rather than in front of the mouth opening, which would have been in the hunt of a disadvantage. Because of these characteristics, some scholars have referred to as a Laggania plankton feeders. Amplectobelua species were in contrast to Anomalocaris smaller and had placed a wider body with the eyes laterally to the mouth.
The Anomalocarididae seem to be closely related to the Opabinididae and fall somewhere in the root group of arthropods. The discovery of a Anomalocarididen from the Devonian suggests that the group is paraphyletic and includes the arthropods.