1999/06/14 by Carole J. Burrow, Susan Turner · 1 citation
Earth and Planetary Sciences · Environmental Science · #Paleontology and Evolutionary Biology #Paleontology and Stratigraphy of Fossils #Ichthyology and Marine Biology #Sister group #Sensu stricto #Biology #Vertebrate #Synapomorphy #Paleontology #Evolutionary biology #Phylogenetic tree #Zoology #Clade
paper · doi:10.1080/02724634.1999.10011135
openalex publication_date 1999/06/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/29
An historical review of the literature relating to placoderm scales preserved in association with articulated dermal plates, or as isolated units in microvertebrate assemblages, is followed by a discussion of their relevance in phylogenetic analyses of the Placodermi. The dentinous tissue forming the tubercles of Early Devonian acanthothoracid scales and dermal bone is similar to that of the dermal bone ornament of some osteostracans, and denticles of the vertebrate Skiichthys from the Ordovician Harding Sandstone. This similarity supports the proposition that the gnathostomes are the sister-group of the Osteostraci, with the Placodermi branching earliest within the gnathostomes, and the Acanthothoraci branching earliest within the Placodermi. The meso-semidentine in acanthothoracid tubercles, rather than semidentine (sensu stricto), is most likely to be synapomorphic for the Placodermi.