Publication Date:
2024-01-12
Description:
The neurocranium is an integral part of the vertebrate head, itself a major evolutionary
\ninnovation1,2
\n. However, its early history remains poorly understood, with great
\ndissimilarity in form between the two living vertebrate groups: gnathostomes ( jawed
\nvertebrates) and cyclostomes (hagfshes and lampreys)2,3
\n. The 100\xe2\x80\x89Myr gap separating
\nthe Cambrian appearance of vertebrates4\xe2\x80\x936
\n from the earliest three-dimensionally
\npreserved vertebrate neurocrania7
\n further obscures the origins of modern states.
\nHere we use computed tomography to describe the cranial anatomy of an Ordovician
\nstem-group gnathostome: Eriptychius americanus from the Harding Sandstone of
\nColorado, USA8
\n. A fossilized head of Eriptychius preserves a symmetrical set of
\ncartilages that we interpret as the preorbital neurocranium, enclosing the fronts of
\nlaterally placed orbits, terminally located mouth, olfactory bulbs and pineal organ.
\nThis suggests that, in the earliest gnathostomes, the neurocranium flled out the
\nspace between the dermal skeleton and brain, like in galeaspids, osteostracans and
\nplacoderms and unlike in cyclostomes2
\n. However, these cartilages are not fused into
\na single neurocranial unit, suggesting that this is a derived gnathostome trait.
\nEriptychius flls a major temporal and phylogenetic gap in our understanding of the
\nevolution of the gnathostome head, revealing a neurocranium with an anatomy unlike
\nthat of any previously described vertebrate.
Keywords:
Multidisciplinary
Repository Name:
National Museum of Natural History, Netherlands
Type:
info:eu-repo/semantics/article
Format:
application/pdf
Permalink