Opabiniidae

Opabiniidae Temporal range: Middle Cambrian - Middle Ordovician, 507–475  Ma PreꞒ Ꞓ O S D C P T J K Pg N
Opabinia (top) and Utaurora (bottom)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Stem group:	† Dinocaridida
Family:	† Opabiniidae Walcott, 1912
Genera
† Opabinia † Utaurora † Mieridduryn † Myoscolex ?

Opabiniidae is an extinct family of marine stem-arthropods. ^[1] Its type and best-known genus is Opabinia . It also contains Utaurora, and Mieridduryn . Opabiniids closely resemble radiodonts, but their frontal appendages were basally fused into a proboscis. Opabiniids also distinguishable from radiodonts by setal blades covering at least part of the body flaps and serrated caudal rami. ^[2]

Cross section

Size comparison

History of study

Opabiniidae was named by Charles Doolittle Walcott in 1912, alongside its type species Opabinia. Walcott interpreted Opabiniidae as a family of anostracan crustaceans, most closely related to Thamnocephalidae. ^[3] Opabinia was restudied in the 1970s, and reinterpreted as a stranger animal. Stephen Jay Gould referred to Opabinia as a "weird wonder", and an illustration of Opabinia prompted laughter when it was first revealed at a paleontological conference. ^[4] In 2022, more opabiniids were discovered. That being Utaurora , and Mieridduryn . ^[2]

Myoscolex from Emu Bay Shale is sometimes suggested to be an opabiniid, ^[5] but morphological features supporting this interpretation are controversial. ^{[6] [2]}

References

1. Tamisiea, Jack (8 February 2022). "One of Evolution's Oddest Creatures Finds a Fossilized Family Member - Opabinia, which swam the seas of Earth's Cambrian era some 500 million years ago, was not just a one hit wonder". The New York Times . Retrieved 10 February 2022.
2. Pates et al. 2022.
3. Walcott 1912.
4. Whittington 1975.
5. Briggs, D. E. G.; Nedin, C. (1997). "The Taphonomy and Affinities of the Problematic Fossil Myoscolex from the Lower Cambrian Emu Bay Shale of South Australia". Journal of Paleontology. 71 (1): 22–32. doi:10.1017/S0022336000038919. JSTOR   1306537. S2CID   131851540.
6. Dzik, Jerzy (2004). "Anatomy and relationships of the Early Cambrian worm Myoscolex" . Zoologica Scripta. 33 (1): 57–69. doi:10.1111/j.1463-6409.2004.00136.x. ISSN   1463-6409. S2CID   85216629.

Works cited

• Pates, Stephen; Wolfe, Joanna M.; Lerosey-Aubril, Rudy; Daley, Allison C.; Ortega-Hernández, Javier (9 February 2022). "New opabiniid diversifies the weirdest wonders of the euarthropod stem group". Proceedings of the Royal Society B: Biological Sciences. 289 (1968). doi:10.1098/rspb.2021.2093. PMC   8826304 . PMID   35135344.
• Walcott, Charles D. (13 March 1912). "Cambrian geology and paleontology II: No. 6.—Middle Cambrian Branchiopoda, Malacostraca, Trilobita, and Merostomata". Smithsonian Miscellaneous Collections. 57 (6).
• Whittington, H. B. (26 June 1975). "The enigmatic animal Opabinia regalis, Middle Cambrian, Burgess Shale, British Columbia". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 271 (910): 1–43. Bibcode:1975RSPTB.271....1W. doi:10.1098/rstb.1975.0033. JSTOR   2417412.