Rare Primicaris Chengjiang Soft-bodied Arthropod
with Preserved Antennae

Primicaris larvaformis

Phylum Arthropoda

Geological Time: Early Cambrian (~525 million years ago)

Size (25.4 mm = 1 inch): Fossil is 4 mm long by 3 mm wide on a 70 mm by 60 mm matrix

Fossil Site: Chengjiang Maotianshan Shales - Quiongzhusi Section, Yu’anshan Member, Heilinpu Formation, Ercaicun Village, Anning, Kunming, Yunnan, China

Fossil Code: CF435

Price: Sold

PrimicarisDescription: The exact taxonomic status of this arthropod is in dispute. It has been termed a “larval trilobitomorph” by some researchers, showing their beliefs in its close affinity with the trilobites. While the Trilobitoorpha was listed in the Treatise, most now consider that this subphylum is invalid, a catchall much like some of the dustbin terms used by Walcott for a number of the Burgess Shale fauna. It was once thought to be a larval form of Naraoia. The Naraoiidae are arachnomorphs and include Misszhouia and Naraoia,. Studies of additional specimens in 1997 led to the establishment of a new genus Primicaris, with the genus name larvaformis drawing attention to its larval appearance. It is quite well preserved, certainly as good as the 70 specimens that were recovered over a decade ago. With a size range known of 2-6 mm, this one is right in the center of that range. The primitive aspects of body plan suggest it may be a basal arachnomorph with affinities to the Vendian arthropod-like animal Parvancorina. The most distinctive feature of this specimen is that it is displays many soft tissue features. The gut trace and internal organs can be clearly seen. Additionally both antennae are evident, with the left projecting upwards and the right off to the side. This is the ONLY example I have ever seen that displays the antennae.

Also see: Chengjiang Biota Fauna List Chengjiang Fossils

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