Luolishania
| Luolishania | ||||||||||||
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| Temporal occurrence | ||||||||||||
| Cambrian | ||||||||||||
| 530 million years | ||||||||||||
| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Luolishania | ||||||||||||
| Hou & Chen , 1989 | ||||||||||||
Luolishania is an extinct, fossilized inhabitant of the sea floor from the Cambrian . Only one species is describedwithin the genus , Luolishania longicruris , which wasnewly discovered in1989 as part of the Chengjiang Fauna Community in southern China. Luolishania is one of the lobopods , a group of marine " worms with legs"known only from fossil sources, whichare similarin physique to the recent but terrestrial (on land) living velvet worms .
description
They were slender, worm-like animals. according to the previous finds from 8.5 to 14.3 millimeters in length and about 0.9 millimeters maximum diameter. The body was divided into two sections ( tagmata ), an oval, slightly broadened head and a trunk section.
head
The head shows oval, somewhat elongated shape and was set off slightly neck-like compared to the trunk. At the front of the head sat two long and thin, feel-like appendages that were flexible but not clearly segmented or curled. In a few specimens, a pair of simple eyes can also be seen, which apparently sat on the upper side (dorsolateral) of the head, behind the antennae. The top of the head may have been protected with a thin head shield. At the back of the head was also a transverse row of three more sclerotized sclerites , each of which ended in a curved, horn-like spine. The mouth opening was at the front end of the animal, mouthparts or other special features are not recognizable here. In a few specimens, however, there are possible indications of a flexible, trunk-like structure.
Trunk section
The trunk bore 14 (possibly up to 16) lobopods, leg-shaped outgrowths. Each pair of legs was assigned a transverse row of three sclerites lying next to one another on the torso itself, so with the additional row of sclerites on the head there is a total of 15 rows. The sclerites each had a thorn-like outgrowth (often difficult to recognize due to the compression during storage or only appearing as a button-like tubercle), similar to that of the Hallucigenia genus . In some specimens a row of spiky, but obviously soft and not sclerotized outgrowths can be seen in the trunk section between the sclerites. Overall, this results in a body structure that appears to be made up of segments . It is noticeable that there were two mutually differentiable sections within the trunk: Both the first five pairs of lobopods and the sclerotized spines that accompanied them were considerably longer than those further to the rear end, the transition was not gradual but rather abrupt. After the compression fossils have been stored, it can be assumed that the anterior pairs of lobopods were oriented differently in life; they may have been carried forward. All lobopods, long or short, were of uniform construction. They were finely curled on the surface, but without any recognizable sections or links. At the end they each had four sclerotized, curved claws, these were needle-thin in the anterior lobopods, and more massive and hook-shaped in the posterior ones. At least some of them. possibly also on all, also had hair bristles arranged in rows (setae). Inside the body of some specimens, a long, straight intestine (or its organic filling material) is visible as a dark band.
Locations
Luolishania longicruris is only known from the Chengjiang Fauna Community of Southwest China, from the Heilinpu Formation, which is assigned to the second series of the Cambrian with an age of around 530 million years . It was only one of several, in total about 6 to 10 lobopod species living here at the same time. The type specimen comes from the Maotianshan slate near Chengjiang, which is now protected as a World Heritage site . More specimens were later discovered in Haikou near Kunming , about 50 kilometers away. A total of about 40 to 50 specimens of the species have been found.
Ecology and way of life
Luolishania was a benthic organism living on the sea floor . Due to the unspecialized morphology, only guesses can be made about his way of life. Since the intestine was not filled with sediment, nutrition as a substrate eater appears unlikely. There is speculation about a possible diet as a filter feeder , whereby the front extremities could have formed a kind of filter basket, possibly together or in association with sponge species .
Taxonomy and systematics
Due to the relatively differentiated morphology for a lobopod, a cladistic analysis reconstructed a position for Luolishania in a species group with the lobopod genera Cardiodictyon , Hallucigenia and Onychodictyon as well as an undescribed species from the Australian fossil deposit Emu Bay ; this grouping was also formally described as the order Archonychophora. If this hypothesis were correct, Luolishania would be more closely related to the arthropods and forms such as Kerygmachela , Anomalocaris and Opabinia , sometimes understood as the order Dinocaridida, than to other lobopods (and also the recent Onychophora). In this case the lobopods would be paraphyletic . However, after different weighting and inclusion of other characteristics, a position in the parent group of the Onychophora itself appears conceivable. Probably all of these forms belong as an extended stem group in the line leading to the Arthropoda .
In the revision by Xiaoya Maa and colleagues (see under Sources), another Lobopod species, Miraluolishania haikouensis Liu et Shu 2004, was synonymous with Luolishania longicruris .
swell
- Xiaoya Maa, Xianguang Hou, Jan Bergström (2009): Morphology of Luolishania longicruris (Lower Cambrian, Chengjiang deposit SW China) and the phylogenetic relationships within lobopodians. Arthropod Structure & Development 38: 271-291. doi : 10.1016 / j.asd.2009.03.001
Individual evidence
- ^ XG Hou & JY Chen (1989) Early Cambrian arthropod-annelid intermediate sea animal, Luolishania gen. Nov. from Cheng-Jiang, Yunnan. Acta Palaeontologica Sinica 28: 207-213. (in Chinese, only viewed English summary)
- ↑ Xiaoya Maa, Xianguang Hou, Jan Bergström (2009): Morphology of Luolishania longicruris (Lower Cambrian, Chengjiang deposit, SW China) and the phylogenetic relationships within lobopodians. Arthropod Structure & Development 38: 271-291. doi : 10.1016 / j.asd.2009.03.001
- ↑ Martin R. Smith & Javier Ortega-Hernañdez (2014): Hallucigenia's onychophoran-like claws and the case for Tactopoda. Nature 514: 363-366. doi : 10.1038 / nature13576
- ↑ Javier Ortega-Hernández (2014): Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848. Biological Reviews of the Cambridge Philosophical Society 2014 doi : 10.1111 /brv.12168 (online before print).