Monura
| Monura | ||||||||||
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| Temporal occurrence | ||||||||||
| Carboniferous to Triassic | ||||||||||
| Systematics | ||||||||||
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| Scientific name | ||||||||||
| Monura | ||||||||||
| Sharov , 1957 |
The Monura are extinct insects (Insecta) that occurred in the Paleozoic era from the Carboniferous to Permian period . More recent finds from Switzerland have also proven their occurrence with a species in the Triassic . This is noteworthy as they apparently survived the mass extinction on the Permian-Triassic boundary .
The rank and status of the Monura is disputed in science. All editors agree, however, that it was a group of primarily wingless "primal" insects, which were formerly grouped together as the (non-holophyletic) " Thysanura ". While in the past numerous editors saw them as an independent insect order, possibly the sister group (Adelphotaxon) of the Ectognatha ( Dicondylia and Archaeognatha , rock jumpers, summarized), today most editors consider them to belong to the Archaeognatha, possibly in the rank of subordination. But it has also been suspected that it could only be a question of juvenile rock jumpers or fish (zygentoma). Today, all Monura are usually assigned to the Dasyleptidae family with the only genus Dasyleptus , but there are also different opinions about this.
Eidonomy
Monura are small insects with a length of approx. 5 to 15 millimeters (measured without the terminal filum) with an elongated physique that is reminiscent of recent fish or rock jumpers. In contrast to these, there is only a long tail thread (terminal filum) at the end of the body, cerci are missing. The group was named after this characteristic (Mon-Ura, "single tails"). The mandibles have only one joint (monocondyle mandible). The antennae are short or of moderate length with a distinct antenna whip , in Dasyletus bongniarti they are shorter than the head. Relatively long maxillary palps are also noticeable on the head. The head also has complex eyes ( compound eyes ), in which the individual ommatidia are slightly separated from each other, so the eye is not closed. The three trunk segments are similar to each other, with the first (pronotum) being the shortest. The legs have a pretarsus with paired claws at the end. The abdomen consists of 11 segments and is narrowed towards the end. Difficult to assess, but important for the interpretation of the relationships are extremities on the abdomen, which are known as styli. In the case of different fossils, these can be found on different segments; some editors also see the same fossil styli whose existence is denied (or at least not mentioned) by others. Some processors interpret the findings as segmented styli (up to four segments), while others say they are unsegmented. In some fossils from Russia, claws can be recognized by the styli, but these are usually no longer interpreted as belonging to the Monura, but presumably belong to other, more original, insect lineages. Females have an ovipositor at the end of their abdomen (segments 8 and 9), the structure of which corresponds to that of recent insects.
Numerous peculiarities of the Monura could be explained by the fact that it is a group of animals with juvenile characteristics, since they can also be detected in young animals or embryos of recent insects. Some fossils are obviously not based on body remains, but on shells ( exuvia ) left behind after moulting . It would be possible that these are juvenile stages of species whose adults are so far unknown. A group that reached sexual maturity prematurely in the juvenile stage (neoteny or pedomorphosis ) is also not unlikely .
Paleoecology
Since the animals are often found curved towards the ventral side (ventral), some investigators suspect that the animals may have had a jumping ability (similar to recent rock jumpers). According to the find conditions and the accompanying fauna, one suspects a way of life in the bank area of fresh or brackish water accumulations, lakes or running waters (supralitoral), similar to some recent rock jumpers (e.g. Dilta littoralis ).
species
Family Dasyleptidae Sharov, 1957, genus Dasyleptus Brongniart , 1885
species
- Dasyleptus lucasi Brongniart, 1885 type species . Oberkarbon (France)
- Dasyleptus sharovi Durden, 1978. Unterperm (Kansas, USA)
- Dasyleptus brongniarti Sharov, 1957. Oberperm (Russia)
- Dasyleptus artinskianus Engel, 2009. Unterperm (Kansas, USA)
- Dasyleptus noli Rasnitsyn, 2000 Oberkarbon (France)
- Dasyleptus rowlandi Rasnitsyn et al., 2004 Unterperm (New Mexico, USA)
- Dasyleptus triassicus Bechly & Stockar, 2011. Middle Triassic (Switzerland)
literature
- A. Kaestner: Volume I Invertebrates - V Part Insecta . Holger. H. Dathe, Berlin 2003, ISBN 3-8274-0930-6 .
- Günther Bechly & Rudolf Stockar (2011): The first Mesozoic record of the extinct apterygote insect genus Dasyleptus (Insecta: Archaeognatha: Monura: Dasyleptidae) from the Triassic of Monte San Giorgio (Switzerland). Palaeodiversity 4: 23-37.
Individual evidence
- ↑ David Grimaldi & Michael Engel: Evolution of the Insects. Cambridge University Press, 2005 ISBN 9780521821490 . p.149.
- ↑ Michael S. Engel (2009): A new Lower Permian bristletail from the Wellington Formation in Kansas (Archaeognatha: Dasyleptidae). Transactions of the Kansas Academy of Science Vol. 112, No. 1/2: 40-44.