From Newsgroup: sci.bio.paleontology
Early evolvability in arthropod tagmosis exemplified by a new radiodont
from the Burgess Shale
Abstract
Much diversity in arthropod form is the result of variation in the
number and differentiation of segments (tagmosis). Fossil evidence to
date has suggested that the earliest-diverging arthropods, the
radiodonts, exhibited comparatively limited variability in tagmosis. We present a new radiodont, Mosura fentoni n. gen. and n. sp., from the
Cambrian (Wuliuan) Burgess Shale that departs from this pattern. Mosura exhibits up to 26 trunk segments, the highest number reported for any radiodont, despite being among the smallest known. The head is short,
with a small, rounded preocular sclerite, three prominent eyes and
appendages with curving endites tipped with paired spines, altogether suggesting a nektonic, macrophagous predatory ecology. The trunk is
divided into a neck, mesotrunk with large swimming flaps and
multisegmented posterotrunk with tightly spaced bands of gill lamellae
and reduced flaps. Detailed preservation of expansive circulatory
lacunae, closely associated with the gills, clarifies the nature of
similar structures in other Cambrian arthropod fossils, including
Opabinia. The morphology of the posterotrunk suggests specialization for respiration, unique among radiodonts, but broadly convergent with the xiphosuran opisthosoma, isopod pleon and hexapod abdomen. This
reinforces the hypothesis that multiple arthropod lineages underwent
parallel diversification in tagmosis, in tandem with their initial
Cambrian radiation.
https://royalsocietypublishing.org/doi/10.1098/rsos.242122
Cambrian fans are already familiar with such radiodonts as Anomalocaris
and Yorgia, but this beast is a little guy, only the sice on a human
index finger, unlike the meter-long Anomalodcartis.
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