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Hallucigenia sp.
Hallucigenia #1
Hallucigenia was found by Walcott (1911) from the Burgess Shale which is famous for yielding bizarre fauna of the Middle Cambrian 1).
"Hallucigenia refers to the bizarre and dream-like appearance of animal" 1), as its name suggests, Hallucigenia has an enigmatic form. Hallucigenia is a member of the "lobopodans", a group of ancient worms which possess pairs of leg-like extensions of body. The affinities of this group are controversial, may be a base group of Panarthropods or a stem group to modern Onychophorans (velvet worm) 2).
Hallucigenia #2
The length of Hallucigenia is between 0.5 and 3.0 cm 1), relatively small.
Hallucigenia has a worm-like body with 7 pairs of dorsal spines and also 7 pairs of slender legs terminated in a pair of claws. The neck has 2 or 3 pairs of slightly short appendages 2). The elongated head with a pair of simple eyes terminates with a mouth which has a radial array of aclerotized elements resemble to ones in targigrades 4).
Hallucigenia may have fed on sponges, or scavenged on decaying animal remains 2).
Hallucigenia #3
Hallucigenia was described as a genus of the Annelids (Polychaeta), but afterwards, it has redescibed and redifined as a new genus and a new family, not an annelid 1). Subsequently, it has been found that the not antero-posterior but also dorso-ventral orientations of Hallucigenia proposed until then are reversed 2).
Hallucigenia #4
Thanahita distos, a species of the family Hallucigeniidae and a distinct genus from Hallucigenia, found from the Silurian, suggesting that this clade would have survived to the Silurian 3).
Hallucigenia
Hallucigenia may have had a warning coloration on tips of its dorsal spines.
created in December 2014.
References:
  1. Conway Morris S (1977) A new metazoan from the Cambrian Burgess Shale of British Columbia. Palaeontology 20(3):623–640
  2. Royal Ontario Museum. The Burgess Shale, Fossil Gallery
  3. Siveter DJ, Briggs DEG, Siveter DJ, Sutton MD, Legg D (2018) A three-dimensionally preserved lobopodian from the Herefordshire (Silurian) Lagerstätte, UKR. Soc. open sci. 5:172101. (DOI:10.1098/rsos.172101).
  4. Smith M, Caron J (2015) Hallucigenia’s head and the pharyngeal armature of early ecdysozoans. [abstract] Nature 523, 75–78. (DOI:10.1038/nature14573).