From Newsgroup: sci.bio.paleontology

Fossil evidence for the ancient link between clonal fragmentation,
six-fold symmetry and an epizoic lifestyle in asterozoan echinoderms

Abstract

Asexual reproduction by means of splitting, also called fissiparity, is
a common feature in some asterozoan groups, especially in ophiactid
brittle stars. Most fissiparous brittle stars show six instead of the
usual five rays, live as epibionts on host organisms, and use clonal fragmentation to rapidly colonize secluded habitats and effectively
expand the margins of their distribution area. While the biology and
ecology of clonal fragmentation are comparatively well understood,
virtually nothing is known about the evolution and geological history of
that phenomenon. Here, we describe an exceptional fossil of an
articulated six-armed brittle star from the Late Jurassic of Germany,
showing one body half in the process of regeneration, and assign it to
the new species Ophiactis hex sp. nov. Phylogenetic inference shows that
the fossil represents the oldest member of the extant family
Ophiactidae. Because the Ophiactis hex specimen shows an original
six-fold symmetry combined with a morphology typically found in epizoic ophiuroids, in line with recent fissiparous ophiactid relatives, we
assume that the regenerating body half is an indication for fissiparity. Ophiactis hex thus shows that fissiparity was established as a means of asexual reproduction in asterozoan echinoderms by the Late Jurassic.

https://royalsocietypublishing.org/doi/10.1098/rspb.2023.2832

This mode of reproduction is well-known in current brittle stars, but
not the origin of this capability. It's now known to be at least 150 Mya.
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