Supplementary files for: The oldest complete jawed vertebrates from the early Silurian of China

Molecular studies suggest that the origin of jawed vertebrates was no
later than the Late Ordovician period (around 450 million years ago (Ma)).
Together with disarticulated micro-remains of putative chondrichthyans
from the Ordovician and early Silurian period, these analyses suggest an
evolutionary proliferation of jawed vertebrates before, and immediately
after, the end-Ordovician mass extinction. However, until now, the
earliest complete fossils of jawed fishes for which a detailed
reconstruction of their morphology was possible came from late Silurian
assemblages (about 425 Ma). The dearth of articulated, whole-body fossils
from before the late Silurian has long rendered the earliest history of
jawed vertebrates obscure. Here we report a newly discovered
Konservat-Lagerstätte, which is marked by the presence of diverse,
well-preserved jawed fishes with complete bodies, from the early Silurian
(Telychian age, around 436 Ma) of Chongqing, South China. The dominant
species, a ‘placoderm’ or jawed stem gnathostome, which we
name Xiushanosteus mirabilis gen. et sp. nov., combines
characters from major placoderm subgroups and foreshadows the
transformation of the skull roof pattern from the placoderm to the
osteichthyan condition. The chondrichthyan Shenacanthus
vermiformis gen. et sp. nov. exhibits extensive thoracic armour plates
that were previously unknown in this lineage, and include a large median
dorsal plate as in placoderms, combined with a conventional chondrichthyan
bauplan. Together, these species reveal a previously unseen
diversification of jawed vertebrates in the early Silurian, and provide
detailed insights into the whole-body morphology of the jawed vertebrates
of this period.