Data from: Evolution of vertebrate postcranial complexity: axial skeleton regionalization and paired appendages in a Devonian jawless fish

One of the major events in vertebrate evolution involves the transition
from jawless (agnathan) to jawed (gnathostome) vertebrates, including a
variety of cranial and postcranial innovations. It has long been assumed
that characters such as the pelvic girdles and fins, male intromittent
organs independent from the pelvic girdles, as well as a regionalized
axial skeleton first appeared in various basal gnathostome groups if not
at the origin of gnathostomes. Here we describe the first occurrence of
pelvic girdles and intromittent organs in the Late Devonian jawless
anaspid‐like fish Euphanerops longaevus Woodward (Miguasha Lagerstätte,
eastern Canada), associated with a morphologically differentiated region
of the axial skeleton. Morphological differentiation of the axial skeleton
is also described for the first time in an extant jawless fish, the sea
lamprey Petromyzon marinus Linnaeus. Our data indicate that
regionalization of the axial skeleton occurred earlier in vertebrate
evolutionary history than previously appreciated. This regionalization is
coupled with modifications of the appendicular skeleton in Euphanerops.
These new observations combined with a new phylogenetic analysis of early
vertebrates provide a more precise understanding of how the appendicular
and axial skeletons developed and evolved within vertebrate evolutionary
history.