Polacanthinae

{{Short description|Extinct subfamily of dinosaurs}} {{Automatic taxobox | name = Polacanthines | fossil_range = Late Jurassic - Late Cretaceous, {{fossilrange|earliest=155|130|125|latest=98.37}} | image = Polacanthus Pelvis.jpg | image_caption = Pelvis of ''Polacanthus'' | taxon = Polacanthinae | authority = Lapparent & Lavocat, 1955 | subdivision_ranks = Genera | subdivision = * {{extinct}}''Gargoyleosaurus''? * {{extinct}}''Gastonia''? * {{extinct}}''Hoplitosaurus'' * {{extinct}}''Peloroplites''? * {{extinct}}''Polacanthus'' * {{extinct}}''Taohelong''? |synonyms_ref=<ref name="madzia2021">{{cite journal|last1=Madzia|first1=D.|last2=Arbour|first2=V.M.|last3=Boyd|first3=C.A.|last4=Farke|first4=A.A.|last5=Cruzado-Caballero|first5=P.|last6=Evans|first6=D.C.|year=2021|title=The phylogenetic nomenclature of ornithischian dinosaurs|journal=PeerJ|volume=9|article-number=e12362|doi=10.7717/peerj.12362|pmid=34966571 |pmc=8667728 |doi-access=free}}</ref> |synonyms= *'''Polacanthidae''' <small>Jaekel, 1910</small> }}

'''Polacanthinae''' is a subfamily of ankylosaurs, most often nodosaurids, from the Late Jurassic through Early Cretaceous of Europe and potentially North America and Asia. The group is defined as the largest clade closer to ''Polacanthus foxii'' than ''Nodosaurus textilis'' or ''Ankylosaurus magniventris'', as long as that group nests within either Nodosauridae or Ankylosauridae. If ''Polacanthus'', and by extent Polacanthinae, falls outside either family-level clade, then the ''-inae'' suffix would be inappropriate, and the proper name for the group would be the informally defined '''Polacanthidae'''.<ref name="madzia2021"/>

Polacanthines were somewhat more lightly armoured than more advanced ankylosaurids and nodosaurids. Their spikes were made up of thin, compact bone with less reinforcing collagen than in the heavily armoured nodosaurids. The relative fragility of polacanthine armour suggests that it may have been as much for display as defense.<ref name=armor2010>{{cite journal | last1 = Hayashi | first1 = S. | last2 = Carpenter | first2 = K. | last3 = Scheyer | first3 = T.M. | last4 = Watabe | first4 = M. | last5 = Suzuki | first5 = D. | year = 2010 | title = Function and evolution of ankylosaur dermal armor | journal = Acta Palaeontologica Polonica| volume = 55 | issue = 2| pages = 213–228 | doi = 10.4202/app.2009.0103 | url = http://www.zora.uzh.ch/34072/1/vorschalt_.pdf | doi-access = free }}</ref> They appear to have become extinct about the same time a land bridge opened between Asia and North America.<ref>Kirkland, J. I. (1996). Biogeography of western North America's mid-Cretaceous faunas - losing European ties and the first great Asian-North American interchange. J. Vertebr. Paleontol. 16 (Suppl. to 3): 45A.</ref>

==Classification== The family Polacanthidae was named by Ernst Jaekel in 1910 to refer to a group of ankylosaurs which seemed to him intermediate between the ankylosaurids and nodosaurids. This grouping was ignored by most researchers until the late 1990s, when it was used as a subfamily (Polacanthinae) by Kirkland for a natural group recovered by his 1998 analysis suggesting that ''Polacanthus'', ''Gastonia'', and ''Mymoorapelta'' were closely related within the family Ankylosauridae, and he additionally referred ''Hoplitosaurus'' and ''Hylaeosaurus'' to the subfamily, though they were too incomplete to analyze.<ref name="kirkland1998"/> Kenneth Carpenter resurrected the name Polacanthidae for a similar group which he also found to be closer to ankylosaurids than to nodosaurids. Carpenter became the first to define Polacanthidae as all dinosaurs closer to ''Gastonia'' than to either ''Edmontonia'' or ''Euoplocephalus''.<ref name="carpenter-2001">{{cite book|title=The Armored Dinosaurs|year=2001|chapter=Phylogenetic analysis of the Ankylosauria|editor=Carpenter, Kenneth|author=Carpenter K|pages=455–484|publisher=Indiana University Press|isbn=0-253-33964-2}}</ref> Most subsequent researchers placed polacanthines as primitive ankylosaurids, though mostly without any rigorous study to demonstrate this idea. The first comprehensive study of 'polacanthid' relationships, published in 2011, found that they are either an unnatural grouping of primitive nodosaurids, or a valid subfamily at the base of Nodosauridae.<ref name="thompson2012"/> In the act of formally defining Polacanthinae in line with the requirements of the PhyloCode, Madzia and colleagues chose for the analysis of Yang ''et al.'' (2013) to be the primary reference for Polacanthinae, supplemented by similar results found by Kirkland (1998), Thompson ''et al.'' (2012), Arbour ''et al.'' (2016), Rivera-Sylva ''et al.'' (2018), and Zheng ''et al.'' (2018).<ref name="madzia2021"/><ref name="yang2013">{{cite journal|last1=Yang|first1=J.|last2=You|first2=H.|last3=Li|first3=D.|last4=Kong|first4=D.|year=2013|title=First discovery of polacanthine ankylosaur dinosaur in Asia|journal = Vertebrata PalAsiatica|volume=51|issue=4|pages=265–277}}</ref><ref name="kirkland1998">{{cite book|last=Kirkland|first=J.I.|year=1998|chapter=A polacanthine ankylosaur (Ornithischia: Dinosauria) from the Early Cretaceous (Barremian) of eastern Utah|editor-last=Lucas|editor-first=S.G.|editor2-last=Kirkland|editor2-first=J.I.|editor3-last=Estep|editor3-first=J.W.|title=Lower and Middle Cretaceous Terrestrial Ecosystems|journal=New Mexico Museum of Natural History and Science Bulletin|volume=14|pages=271–281}}</ref><ref name="thompson2012">{{cite journal|last1=Thompson|first1=R.S.|last2=Parish|first2=J.C.|last3=Maidment|first3=S.C.R.|last4=Barrett|first4=P.M.|year=2012|title=Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)|journal=Journal of Systematic Palaeontology|volume=10|issue=2|pages=301–312|doi=10.1080/14772019.2011.569091|bibcode=2012JSPal..10..301T }}</ref><ref name="arbour2016">{{cite journal|last1=Arbour|first1=V.M.|last2=Zanno|first2=L.E.|last3=Gates|first3=T.|year=2016|title=Ankylosaurian dinosaur palaeoenvironmental associations were influenced by extirpation, sea-level fluctuation, and geodispersal|journal=Palaeogeography, Palaeoclimatology, Palaeoecology|volume=449|pages=289–299|doi=10.1016/j.palaeo.2016.02.033|bibcode=2016PPP...449..289A }}</ref><ref name="rivera2018">{{cite journal|last1=Rivera-Sylva|first1=H.E.|last2=Frey|first2=E.|last3=Stinnesbeck|first3=W.|last4=Carbot-Chanona|first4=G.|last5=Sanchez-Uribe|first5=I.E.|last6=Guzmán-Gutiérrez|first6=J.R.|year=2018|title=Paleodiversity of Late Cretaceous Ankylosauria from Mexico and their phylogenetic significance|journal=Swiss Journal of Palaeontology|volume=137|issue=1 |pages=83–93|doi=10.1007/s13358-018-0153-1|doi-access=free|bibcode=2018SwJP..137...83R }}</ref><ref name="zheng2018">{{cite journal|last1=Zheng|first1=W.|last2=Jin|first2=X.|last3=Azuma|first3=Y.|last4=Wang|first4=Q.|last5=Miyata|first5=K.|last6=Xu|first6=X.|year=2018|title=The most basal ankylosaurine dinosaur from the Albian–Cenomanian of China, with implications for the evolution of the tail club|journal=Scientific Reports|volume=8|issue=1 |page=3711|doi=10.1038/s41598-018-21924-7|pmid=29487376 |pmc=5829254 |doi-access=free|bibcode=2018NatSR...8.3711Z }}</ref>

{{clade| style=font-size:85%;line-height:80% |label1=Nodosauridae |1={{clade |1=''Antarctopelta'' |2={{clade |1={{clade |1=''Mymoorapelta'' |2={{clade |1=''Anoplosaurus'' |2=''Hylaeosaurus'' }} }} |2={{clade |1=''Tatankacephalus'' |2=''Horshamosaurus'' |label3=Nodosaurinae |3={{clade |1={{clade |1=''Zhejiangosaurus'' |2={{clade |1=''Struthiosaurus languedocensis'' |2=''Struthiosaurus austriacus'' }} }} |2={{clade |1=''Hungarosaurus'' |2={{clade |1=''Animantarx'' |2={{clade |1=''Niobrarasaurus'' |2=''Nodosaurus'' |3=''Pawpawsaurus'' |4=''Sauropelta'' |5=''Silvisaurus'' |6=''Stegopelta'' |7=''Texasetes'' |8={{clade |1=''Edmontonia'' |2=''Panoplosaurus'' }} }} }} }} }} |label4='''Polacanthinae''' |4={{clade |1=''Hoplitosaurus'' |2={{clade |1=''Gargoyleosaurus'' |2={{clade |1=''Gastonia'' |2={{clade |1=''Peloroplites'' |2={{clade |1=''Taohelong'' |2=''Polacanthus'' }} }} }} }} }} }} }} }} }}

While the clade is frequently referenced in literature, a majority of taxa considered to be polacanthines have instead been found to not form any natural groups with ''Polacanthus'', representing both primitive nodosaurids, primitive ankylosaurids, or outside the Nodosauridae-Ankylosauridae clade.<ref name="madzia2021"/> In the analysis of Arbour ''et al.'' in 2016, and its subsequent modifications by Rivera-Sylva ''et al.'' and Zheng ''et al.'' in 2018, only ''Hoplitosaurus'' was resolved as a polacanthine alongside ''Polacanthus'', with ''Peloroplites'' and ''Taohelong'' falling within Nodosaurinae, ''Gargoyleosaurus'', ''Gastonia'', and ''Mymoorapelta'' being more basal nodosaurids outside both subclades, and ''Hylaeosaurus'' representing an early-diverging ankylosaurid.<ref name="arbour2016"/><ref name="rivera2018"/><ref name="zheng2018"/>

==References== {{Reflist}}

{{Thyreophora|N.}} {{Taxonbar|from=Q21711005}}

Category:Ankylosauria Category:Dinosaur subfamilies Category:Early Cretaceous dinosaurs