Yanjiahella is a stem-group echinoderm

[Halichoeres]

Tired of reading about who the biggest Ty***nosaurus was? In actual paleontology news, this species was first described in 2012 as one of the many Cambrian problematica (taxa whose phylogenetic affinities are hard to discern). This study analyzes dozens of specimens and work out that it is a stem-group echinoderm. Echinoderms are famous for having radial symmetry, although they come from bilaterian ancestors (and their larvae are still bilaterally symmetric). Yanjiahella biscarpa is a bilaterally symmetric, armor plated animal from the Cambrian of China, showing that the characteristic skeleton of echinoderms precedes their bizarre symmetry-shifting morphology. Fans of Paleozoic echinoderms will know that there were many non-symmetric species in the stem-group, shown here in this cladogram with illustrations by Nobu Tamura:



And a reconstruction of Yanjiahella as it might have lived:



Paper (open access): https://www.nature.com/articles/s41467-019-09059-3

[Halichoeres]

A new paper reanalyzes the character matrix of Topper et al. and finds that the support for its being an echinoderm specifically is weak. It's possible that it could be an early ambulacrarian or even a hemichordate: Zamora et al., open access in Nature Communications: https://www.nature.com/articles/s41467-020-14920-x