Protomelission

Protomelission
Temporal range: Cambrian stage 3
Microfossil of Protomelission from Wirrealpa. Reproduced from Zhang et al. 2021[2]
Scientific classification Edit this classification
Clade: Viridiplantae
Division: Chlorophyta
Class: UTC clade
Order: Dasycladales (?)
Genus: †Protomelission
Brock, G. A. & Cooper, B. J. 1993[1]

Protomelission is a Cambrian fossil taxon of contested affinity. It comprises cataphract arrays of box-like chambers, forming a club-shaped thallus surrounding a hollow central cavity. It was first described from phosphatized microfossils whose individual chambers were interpreted as housing the zooids of a non-mineralized bryozoan, which would make it the only affinity representative of that phylum – implying that all animal phyla originated in the Cambrian period.[3] The subsequent discovery of articulated macrofossils from the Xiaoshiba[4] biota called into question the biological nature of the distal apertures, showing that the surface was instead covered with leaf-like triangular flanges. This has led to the reinterpretation of the fossil material as a "seaweed", strictly as a dasycladalean green alga.[5]

  1. ^ Brock, Glenn A.; Cooper, Barry J. (1993). "Shelly fossils from the Early Cambrian (Toyonian) Wirrealpa, Aroona Creek, and Ramsay Limestones of South Australia". Journal of Paleontology. 67 (5): 758–787. doi:10.1017/S0022336000037045. S2CID 132278189.
  2. ^ Zhang, Zhiliang; Zhang, Zhifei; Ma, Junye; Taylor, Paul D.; Strotz, Luke C.; Jacquet, Sarah M.; Skovsted, Christian B.; Chen, Feiyang; Han, Jian; Brock, Glenn A. (2021). "Fossil evidence unveils an early Cambrian origin for Bryozoa". Nature. 599 (7884): 251–255. Bibcode:2021Natur.599..251Z. doi:10.1038/s41586-021-04033-w. PMC 8580826. PMID 34707285.
  3. ^ Ernst, Andrej; Wilson, Mark A. (2021). "Bryozoan fossils found at last in deposits from the Cambrian period". Nature. 599 (7884): 203–204. Bibcode:2021Natur.599..203E. doi:10.1038/d41586-021-02874-z. PMID 34707263. S2CID 240073927.
  4. ^ https://www.mindat.org/paleo_loc.php?id=23464
  5. ^ Yang, Jie; Lan, Tian; Zhang, Xi-Guang; Smith, Martin R. (2023). "Protomelission is an early dasyclad alga and not a Cambrian bryozoan". Nature. 615 (7952): 468–471. doi:10.1038/s41586-023-05775-5. PMID 36890226. S2CID 257425218.