. Early Devonian fishes from Utah : Arthrodira . Fig. 116. Cranial roof and cheek plates of hypothetical primitive arctolepid. CE, central; IN, internal; MG, marginal; NU, nuchal; PAN, paranuchal; PI, pineal; PMG, postmarginal; PN, postnasal; PRO, preorbital; PSO, post- suborbital; PTO, postorbital; RO, rostral; SO, suborbital; cc, central canal; ifc, infraorbital canal; Ic, main lateral line; mp, middle pit line; ope, "opercular" canal; pfc, profundus canal; poc, preopercular canal; pp, posterior pit line; smc, supramaxillary canal; soc, supraorbital canal; stc, supratemporal commis
. Early Devonian fishes from Utah : Arthrodira . Fig. 116. Cranial roof and cheek plates of hypothetical primitive arctolepid. CE, central; IN, internal; MG, marginal; NU, nuchal; PAN, paranuchal; PI, pineal; PMG, postmarginal; PN, postnasal; PRO, preorbital; PSO, post- suborbital; PTO, postorbital; RO, rostral; SO, suborbital; cc, central canal; ifc, infraorbital canal; Ic, main lateral line; mp, middle pit line; ope, "opercular" canal; pfc, profundus canal; poc, preopercular canal; pp, posterior pit line; smc, supramaxillary canal; soc, supraorbital canal; stc, supratemporal commissure. endocranium was low and broad, with large suborbital shelves and supraorbital processes and a short occipital region; probably it was perichondrally ossified, with the nasal capsules separately ossified. The possible arrangement of the cranial plates of a primitive euar- throdire is shown in figure 116. The trunk shield was low and broad. The median dorsal was short and broad with a central growth center, and the posterior dorsals were large. The anterior dorso-laterals lacked trochleae for the cranial roof, and both the anterior and posterior dorso-laterals were probably relatively long and low. The anterior laterals had nearly central ossi- fication centers, their anterior triangles were not modified into an inner wing, and their ventral triangles were large. The posterior laterals were well developed and probably rather long and low. The spinals were of moderate length. The anterior ventro-laterals had long spinal edges and bounded deep pectoral sinuses. The dorsal laminae of the intero-laterals were small and formed little or no inner wings. Paired antero-ventrals were present, and the posterior ventro-laterals
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Keywords: ., bookcentury1900, bookcollectionbiodiver, booksubjectfishesfossil
