| Kylinxia | |
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| Artist's restoration, following three eye interpretation | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Genus: | †Kylinxia |
| Species: | †K. zhangi |
| Binomial name | |
| Kylinxia zhangi Zenget al., 2020 | |
Kylinxia is agenus of extinctarthropod described in 2020. It was described from six specimens discovered in Yu'anshan Formation (Maotianshan Shales) in southernChina. The specimens are assigned to one speciesKylinxia zhangi.[1] Dated to 518 million years, the fossils falls under theCambrian period.[2] Announcing the discovery on 4 November 2020 at a press conference,Zeng Han of the Nanjing Institute of Geology and Paleontology, said that the animal "bridges the evolutionary gap fromAnomalocaris to true arthropods and forms a key ‘missing link’ in the origin of arthropods,"[3] which was "predicted byDarwin’s evolutionary theory."[4] The same day the formal description was published inNature.[1]
Kylinxia zhangi was discovered among the Maotianshan Shales from Yu'anshan Formation at Yunnan in southern China in 2019. Zeng Han, Zhao Fangchen, and Huang Diying of the Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences, made the formal description and taxonomy inNature in 2020. They found six specimens which are well preserved and complete. The original specimens (holotype) is kept at the Nanjing Institute of Geology and Palaeontology, while the additional specimens (paratypes) are maintained at the Yingliang Stone Natural History Museum.[1]
The genus nameKylinxia refers to a mixture of arthropod characters;kylin (qilin) is derived from the chimeric creature in Chinese mythology, whilexia (蝦) is a Chinese word for shrimp-like arthropod. The species namezhang is after Yehui Zhang who contributed the additional specimens (paratypes).[1][2]
Kylinxia is a tiny shrimp-likearthropod, measuring about 5 centimetres (2.0 in) long and about 1.2 cm (0.47 in) broad at the widest part of the body.[1] Its body is segmented and divisible into three regions, namely head, trunk and thepygidium.[1][7]Kylinxia possesses a mixture of characters resembling various Cambrian arthropod taxa, notablyOpabinia (eyes),radiodonts (frontalmost appendages) andmegacheirans (trunk).[1]
The head ofKylinxia covered by a fusedcarapace with rounded genal corner comparable to those of the megacheiranHaikoucaris.[8][1] Similar to the purported basal arthropodOpabinia,[9][10] the head was initially suggested to have borne five eyes that were attached through eye stalks,[1] however a later 2023 study suggested that there were only three eyes, one central medial eye and two lateral eyes.[6] In contrast to the fusedproboscis ofOpabinia[11] and the hand-likegreat appendages of megacheirans, the head region ofKylinxia has a pair of unfused, 16-jointed frontalmost appendages each of which has terminal and paired, serrated inner spines (endites), similar to those seen in the radiodont[2] generaAnomalocaris (overall proportion) andRamskoeldia (endites).[12][1] Unlike radiodonts, the frontalmost appendages face upward and lack outer spines, which is a feature shared by the great appendages of megacheirans.[8][1]
Similar to the multisegmented megacheirans, the trunk ofKylinxia covers most of the body length and is composed of up to 26[6] metameric segments (tergites) each corresponded to a pair of appendages.[1] Within the post-oral appendages, the anteriormost 4 pairs are considered as reduced flap-like structures which arose from the head and two anterior trunk segments,[1] later 2023 study considered these are two-branched (biramous) and all from head.[6] The remaining appendages are all biramous, with the leg-like inner branches (endopod) each composed of at least seven segments and the suboval outer branches (exopods) each possess marginal lamellae.[1] The triangular pygidium covers at least 5 pairs of appendages, terminated with a three-lobed tail fan consisting of a middle and a pair of lateral lobes as seen in several Cambrian arthropods such ashymenocarine andfuxianhuiids.[13]
Kylinxia has generally been placed as one of the most basal members ofDeuteropoda. A close relationship with the genusFengzhengia has been proposed. Cladogram after O’Flynn et al, 2023:[6]
| Total group Arthropoda |
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Cladogram after Zhang et al. 2023:[14]
| Total group Arthropoda |
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