| Xenusion auerswaldae Temporal range: | |
|---|---|
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| Fossil specimen | |
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| Life restoration | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| (unranked): | Panarthropoda |
| Phylum: | † "Lobopodia" |
| Class: | † Xenusia |
| Order: | † Protonychophora |
| Family: | † Xenusiidae |
| Genus: | † Xenusion Pompeckj, 1927 |
| Species: | †X. auerswaldae |
| Binomial name | |
| †Xenusion auerswaldae Pompeckj, 1927 | |
Xenusion auerswaldae is an early lobopodian known from three [1] specimens found in glacial erratics on the Baltic coast of Germany. [2] Another specimen, discovered shortly after the holotype, was briefly observed but soon went missing. Except for this lost specimen, the fossils probably originated in the Kalmarsund Sandstone of Southern Sweden, [3] which was deposited in the Lower Cambrian (Upper Tommotian–Lower Atdabanian; Stages 2→3). [4] It is the oldest currently known lobopodian with soft body fossils. [5]
The specimens are not especially well preserved. The older specimen is 10 cm or so in length with a narrow, weakly segmented body. Assuming it was the posterior section, the specimen was estimated to be part of an animal about 20 cm in length. [2] A depression runs up the bottom on all but the rearmost segments. There is a slightly bulbous termination, and each segment before that seems to have a single pair of tapering annulated legs similar to the modern onychophoran, but without specialized feet and claws. More than 10 body segments were present. [6] There is presumably a spine on each body bump and faint transverse parallel striations on the annulations on the legs. [2] [6] The legs of what is possibly the foremost segments are either absent or not preserved. The head is believed to be missing or poorly preserved. Based on a new specimen that shows the anterior section, it possibly had a long narrow proboscis, [2] but this also suggested to be a preservational artefact. [7]
Xenusion has been reinterpreted as an Ediacaran frond animal by Tarlo, and a drawing of that interpretation has been presented by McMenamin. [8] In a photograph presented in The Treatise on Invertebrate Paleontology Volume O, the organism's appearance seems to support the original interpretation more. Further studies of Xenusiid close the possibility of a Rangeomorphy affinity. [2] [6]