Plourdosteus

{{Automatic taxobox

| fossil_range = Devonian: Givetian–Frasnian, {{Fossil range|391.8|374.5}}

| image = Plourdosteus speciesDB15 2.jpg

| image_caption = Various species of Plourdosteus, from Late Devonian of Canada, Russia and Baltic countries

| taxon = Plourdosteus

| authority = Ørvig, 1951

| subdivision_ranks = Species

| subdivision =

Plourdosteus canadensis (Woodward, 1892)
Plourdosteus livonicus (Eastman, 1896)
Plourdosteus mironovi (Obruchev, 1933)
Plourdosteus trautscholdi (Eastman, 1897)

}}

File:Plourdosteus trautscholdi.jpg

Plourdosteus is an extinct genus of placoderm arthrodire which was relatively widespread in Euramerica during the Givetian to Frasnian ages of the Devonian.{{cite journal |author=S. V. Moloshnikov |year=2008 |title=The placoderm Plourdosteus livonicus (Eastman) in the early Frasnian of the Central Devonian Field and the trophic structure of the Mikhailovskii Fish Assemblage |journal=Paleontological Journal |volume=42 |issue=6 |doi=10.1134/S0031030108060063 |pages=607–614|bibcode=2008PalJ...42..607M }} It was a small placoderm, with P. canadensis specimen MNHM 2-177 measuring {{cvt|37.5|cm|in||}} long.{{cite journal|last=Engelman|first=Russell K.|year=2023|title=A Devonian Fish Tale: A New Method of Body Length Estimation Suggests Much Smaller Sizes for Dunkleosteus terrelli (Placodermi: Arthrodira)|journal=Diversity|volume=15|issue=3|at=318|doi=10.3390/d15030318 |doi-access=free }}

Etymology

The name Plourdosteus commemorates the Plourde family at Miguasha National Park.{{cite web |url=http://miguasha.ca/mig-en/plourdosteus.php |title=Plourdosteus |publisher=Miguasha National Park |year=2007 |access-date=June 21, 2010}}

Taxonomy

Plourdosteus was previously assigned to the family Plourdosteidae within the Coccosteomorphi. However, subsequent studies found the family Plourdosteidae to be polyphyletic and should be dismissed. Plourdosteus was then proposed to be a member of Panxiosteidae.{{Cite journal |last1=Carr |first1=R.K. |last2=Hlavin |first2=W.J. |title=Two new species of Dunkleosteus Lehman, 1956, from the Ohio Shale Formation (USA, Famennian) and the Kettle Point Formation (Canada, Upper Devonian), and a cladistic analysis of the Eubrachythoraci (Placodermi, Arthrodira) |journal=Zoological Journal of the Linnean Society |volume=159 |issue=1 |pages=195–222 |year=2010 |doi=10.1111/j.1096-3642.2009.00578.x |doi-access=free }}{{Cite journal |author1=You-An Zhu |author2=Min Zhu |title=A redescription of Kiangyousteus yohii (Arthrodira: Eubrachythoraci) from the Middle Devonian of China, with remarks on the systematics of the Eubrachythoraci | journal=Zoological Journal of the Linnean Society |volume=169 |issue=4 |pages=798–819 |year=2013 |doi=10.1111/zoj12089 |doi-access=free }} In the 2010 Carr & Hlavin phylogenetic study, Panxiosteidae was recognized as the sister taxon to the family Dunkleosteidae, which together comprised the superfamily Dunkleosteoidea (one of the three major clades of Eubrachythoraci).

The phylogeny of Plourdosteus within Panxiosteidae is shown in the cladogram below from the 2013 Zhu & Zhu study:

{{clade| style=font-size:85%;line-height:85%

|grouplabel1={{clade labels |width=10em; |label1=Pachyosteomorphi |top1=65% |color1=green}}

|label1=Eubrachythoraci

|1={{clade

|label1=Coccosteomorphi

|1={{clade

|1=Coccosteus cuspidatus

|2={{clade

|1=Harrytoombsia elegans

|2={{clade

|1=Mcnamaraspis kaprios

|label2=Incisoscutoidea

|2={{clade

|1=Compagopiscis croucheri

|2={{clade

|1=Incisoscutum ritchiei

|2=Incisoscutum sarahae }}

|label3=Camuropiscidae

|3={{clade

|1=Latocamurus coulthardi

|2=Camuropiscis laidlawi

|3={{clade

|1=Rolfosteus canningensis

|2=Tubonasus lennardensis

|3=Fallacosteus turneri }} }} }} }} }} }}

|label2=Aspinothoracidi

|2={{clade

|1=Dinichthys herzeri |barbegin1=green

|2={{clade

|1=Hadrosteus rapax |bar1=green

|2={{clade

|1=Gorgonichthys clarki |bar1=green

|2={{clade

|1=Heintzichthys gouldii |bar1=green

|label2=Selenosteidae

|2={{clade

|1=Stenosteus angustopectus |bar1=green

|2={{clade

|1=Gymnotrachelus hydei |bar1=green

|2={{clade

|1=Rhinosteus parvulus |bar1=green

|2=Pachyosteus bulla |bar2=green }} }} }} }} }} }} }} }}

|label2=Dunkleosteoidea

|2={{clade

|1=Westralichthys uwagedensis |bar1=green

|2={{clade

|1={{clade

|1=Protitanichthys rockportensis |bar1=green

|label2=Panxiosteidae

|2={{clade

|1=Panxiosteus ocullus |bar1=green

|2=Janiosteus timanicus |bar2=green

|3=Plourdosteus canadensis |bar3=green }} }}

|label2=Dunkleosteidae

|2={{clade

|1={{clade

|1=Eastmanosteus calliaspis |bar1=green

|2=Xiangshuiosteus wui |bar2=green }}

|2={{clade

|1=Eastmanosteus pustulosus |bar1=green

|2=Kiangyousteus yohii |bar2=green

|3=Golshanichthys asiatica |bar3=green

|4={{clade

|1=Dunkleosteus amblyodoratus |bar1=green

|2=Dunkleosteus terrelli |bar2=green

|3=Dunkleosteus raveri |barend3=green }} }} }} }} }} }} }}

However, the subsequent 2016 Zhu et al. study using a larger morphological dataset recovered Panxiosteidae well outside of Dunkleosteoidea, instead within Coccosteomorphi and then Coccosteoidea as the sister group of Coccosteidae, as shown in the cladogram below:{{Cite journal |last1=Zhu |first1=You-An |last2=Zhu |first2=Min |last3=Wang |first3=Jun-Qing |date=1 April 2016 |title=Redescription of Yinostius major (Arthrodira: Heterostiidae) from the Lower Devonian of China, and the interrelationships of Brachythoraci |journal=Zoological Journal of the Linnean Society |volume=176 |issue=4 |pages=806–834 |doi=10.1111/zoj.12356|issn=0024-4082 |doi-access=free }}

{{clade| style=font-size:85%;line-height:85%

|label1=Eubrachythoraci

|1={{clade

|label1=Coccosteomorphi

|1={{clade

|label1=Coccosteoidea

|1={{clade

|label1=Coccosteidae

|1={{clade

|1=Millerosteus minor

|2=Coccosteus cuspidatus }}

|2={{clade