Alalcomenaeus
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Alalcomenaeus |
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| Temporal occurrence | ||||||||||||
| early to middle Cambrian | ||||||||||||
| 525 million years | ||||||||||||
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| Scientific name | ||||||||||||
| Alalcomenaeus | ||||||||||||
| Simonetta , 1970 | ||||||||||||
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Alalcomenaeus is an extinct genus of animals from the early to middle Cambrian . The numerous fossils of his representative Alalcomenaeus cambricus from the Maotianshan slate in the Chinese province of Yunnan and the Burgess slate in British Columbia in Canada suggest that Alalcomenaeus was one of the most common animal species of its time. Alalcomenaeus isdiscussedas an early representative of the arachnid line or the crustacean line.
Occurrence
Over 600 specimens of Alalcomenaeus cambricus have so far been found as fossils in the Burgess slate. With a frequency of around 1.2%, Alalcomenaeus is one of the most common genera of the Burgess slate biota . Numerous other finds come from the Maotianshan shale in China. Here, too, he was one of the more frequent representatives of the so-called Chengjiang Fauna Community . Other finds, such as from the Wheeler schist in Utah , underline the occurrence and distribution of this species of animal in the early to middle Cambrian. In addition, other finds of a species called Alalcomenaeus unbekanntcebrosus have been described, but their assignment to the genus Alalcomenaeus is not certain.
features
Alalcomenaeus cambricus was up to 60 mm in length. Its body consisted of a pronounced head shield (cephalon), eleven trunk segments ( somite ) and a final telson and was protected by an exoskeleton . On the head shield Alalcomenaeus wore five eyes, the two outer ones of which were stalked. Striking is some gap leg -like segmented appendages on the head, also called the Great Appendage be called ( "big notes"). Each of the 11 trunk segments carried a pair of split-bone-like extremities. The mouth at the front of the head was connected to the anus lying on the telson via the intestines.
behavior
Like most of its close relatives, Alalcomenaeus cambricus was believed to be a predator that fed on other animals. His physique suggests that he moved by swimming with the help of his torso and especially his paddle-like Telsons.
Systematics
Originally, Alalcomenaeus cambricus was considered an early descendant of the crustacean line. Based on its anatomy, it was considered to be the ideal ancestor of today's gillipers and the cephalocarida . This concept was largely rejected in the early 1990s. According to cladistic analyzes, the genus Alalcomenaeus, together with other representatives of the so-called Megacheira, belongs to the class of Arachnomorpha .
Individual evidence
- ^ A b Briggs DE, Collins D: The Arthropod Alalcomenaeus cambricus Simonetta, from the Middle Cambrian Burgess Shale of British Columbia . In: Palaeontology . 42, No. 6, 1999, pp. 953-977. doi : 10.1111 / 1475-4983.00104 .
- ↑ Hou XG: Two new arthropods from Lower Cambrian, Chengjiang, eastern Yunnan . In: Acta Palaeontologica Sinica . 26, 1987, pp. 236-256.
- ↑ Simonetta A, Delle Cave L: The Cambrian non trilobite athropods from the Burgess Shale of British Columbia. A study of their comparative morphology, taxonomy and evolutionary significance . In: Palaeontographia Italica . 59, 1975, pp. 1-37.
- ^ Wills MA, Briggs DE, Fortey RA: Disparity as an evolutionary metric: a comparison of Cambrian and Recent arthropods . In: Paleobiology . 20, 1994, pp. 93-130.
literature
- Briggs DE, Collins D: The Arthropod Alalcomenaeus cambricus Simonetta, from the Middle Cambrian Burgess Shale of British Columbia . In: Palaeontology . 42, No. 6, 1999, pp. 953-977. doi : 10.1111 / 1475-4983.00104 .
