{{Short description|Genus of dinosaurs}} {{Speciesbox | fossil_range = <br>Late Jurassic, {{fossilrange|Kimmeridgian}} | genus = Trimucrodon | parent_authority = Thulborn, 1973<ref name="thulborn1973">{{cite journal|last=Thulborn|first=R.A.|year=1973|title=Teeth of ornithischian dinosaurs from the Upper Jurassic of Portugal|journal=Memórias dos Serviços Geológicos de Portugal|volume=22|pages=89–134}}</ref> | species = cuneatus | authority = Thulborn, 1973 | display_parents = 2 }}
'''''Trimucrodon''''' is a genus of ornithischian dinosaur from the Late Jurassic Lourinhã Formation of Portugal. The type, and currently only, species is '''''T. cuneatus'''''.<ref name="thulborn1973" />
== Discovery and naming == Three isolated teeth found at the Porto Dinheiro (or Pinhiero) locality in the Lisboa District of Portugal were given the name in 1973 by Richard A. Thulborn, derived from the Latin words for "three" and a dagger point, {{wikt-lang|la|tri-}} and {{wikt-lang|la|mucro}}, and the Ancient Greek word {{wikt-lang|grc|ὀδούς}} for "tooth". The only species in the taxon is '''''Trimucrodon cuneatus''''', taken from the wedge shape of the teeth.<ref name="thulborn1973" /> Though the unit the specimens came from was originally unnamed,<ref name="thulborn1973" /> it was referred to the Alcobaça,<ref name="weishampel2004">{{cite book|last1=Weishampel|first1=D.B.|last2=Barrett|first2=P.M.|last3=Coria|first3=R.A.|last4=Le Loeuff|first4=J.|last5=Xu|first5=X.|last6=Zhao|first6=X.|last7=Sahni|first7=A.|last8=Gomani|first8=E.M.P.|last9=Noto|first9=C.R.|year=2004|chapter=Dinosaur Distribution|editor-last=Weishampel|editor-first=D.B.|editor2-last=Dodson|editor2-first=P.|editor3-last=Osmólska|editor3-first=H.|title=The Dinosauria|edition=2nd|publisher=Indiana University Press|pages=517–606|isbn=978-0-520-25408-4}}</ref> and then Lourinhã Formations, specifically the late Kimmeridgian Amoreira–Porto Novo Member.<ref name="ribeiro2018">{{cite journal|last1=Ribeiro|first1=C.|last2=Mateus|first2=O.|year=2018|title=Stratigraphic position of the Late Jurassic tetrapods from Porto Dinheiro (Lourinhã, Portugal)|journal=1st Palaeontological Virtual Congress|doi=10.13140/RG.2.2.13524.65929}}</ref><ref name="mateus2014">{{Cite journal | doi = 10.1080/02724634.2013.822875| title = ''Zby atlanticus'', a new turiasaurian sauropod (Dinosauria, Eusauropoda) from the Late Jurassic of Portugal| journal = Journal of Vertebrate Paleontology| volume = 34| issue = 3| pages = 618| year = 2014| last1 = Mateus | first1 = O. V. | last2 = Mannion | first2 = P. D. | last3 = Upchurch | first3 = P. | bibcode = 2014JVPal..34..618M| s2cid = 59387149}}</ref> The type specimen, uncovered between 1962 and 1967 by German zoologist and paleontologist Georg Krusat, is distinguished by prominent denticles at the front and rear ends of the crown, and comes from an individual under {{convert|2|m|ft|abbr=on}} long.<ref>G. Krusat, 1969, "Ein Panthotheria-Molar mit dreispitzigem Talonid aus dem Kimmeridge von Portugal", ''Paläontologische Zeitschrift'' '''43'''(1/2): 52-56</ref><ref name="sereno1991">{{cite journal|last=Sereno|first=P.C.|year=1991|title=''Lesothosaurus'', "Fabrosaurids," and the early evolution of Ornithischia|journal=Journal of Vertebrate Paleontology|volume=11|issue=2|pages=168–197|doi=10.1080/02724634.1991.10011386|bibcode=1991JVPal..11..168S }}</ref><ref name="mateus2009">{{cite journal|last1=Mateus|first1=O.|last2=Milàn|first2=J.|year=2009|title=A diverse Upper Jurassic dinosaur ichnofauna from central-west Portugal|journal=Lethaia|volume=43|issue=2|pages=1–13|doi=10.1111/j.1502-3931.2009.00190.x|url=http://doc.rero.ch/record/209161/files/PAL_E4024.pdf}}</ref> It is currently kept in the collections of the Museu Geológico do Instituto Geológico e Mineiro in Lisbon, Portugal, formerly having been kept in the collections of the Free University of Berlin.<ref name="mateus2009" />
== Description == The holotype tooth of ''Trimucrodon'' is {{convert|4.4|mm|in|abbr=on}} wide, similar to some of the referred specimens, with the crown about as tall as wide. Other specimens have crowns as small as {{convert|1.5|mm|in|abbr=on}} wide and only half as tall as wide. The crowns are of varying amounts of asymmetry, though each edge bears the same number of tapering denticles. Tooth enamel is present of an equal thickness on both sides of the tooth crown, and both faces are smooth without ridges. The denticles increase in size away from the apex of the crown, ending with two widely divergent and sharply-pointed denticles at the front and rear ends of the base.<ref name="galton1994"/>
== Classification == ''Trimucrodon'' was originally referred to as a member of the ornithopod family Fabrosauridae by Thulborn in 1973, closest to ''Echinodon'' but also related to ''Alocodon'' and ''Fabrosaurus''.<ref name="thulborn1973"/> Peter M. Galton retained it in the family in 1978, though he noted that there were significant differences between ''Trimucrodon'' and ''Echinodon'', and the Middle to Late Jurassic fabrosaurids ''Alocodon'', ''Trimucrodon'' and ''Echinodon'' were representative of three independent and only distantly related branches of the family, with ''Nanosaurus'' not preserving enough material to determine its relationships.<ref name="galton1978">{{cite journal|last=Galton|first=P.M.|year=1978|title=Fabrosauridae, the basal family of ornithischian dinosaurs (Reptilia: Ornithopoda)|journal=Paläontologische Zeitschrift|volume=52|issue=1/2|pages=138–159|doi=10.1007/BF03006735|bibcode=1978PalZ...52..138G |s2cid=84613826}}</ref> Given that the species was only represented by teeth, ''Trimucrodon'' was designated as a ''nomen dubium'' in 1990 by David B. Weishampel and Lawrence M. Witmer, as an indeterminate member of Ornithischia outside Ornithopoda.<ref name="weishampel1990">{{cite book|last1=Weishampel|first1=D.B.|last2=Witmer|first2=L.M.|year=1990|chapter=''Lesothosaurus'', ''Pisanosaurus'' and ''Technosaurus''|editor-last=Weishampel|editor-first=D.B.|editor2-last=Dodson|editor2-first=P.|editor3-last=Osmólska|editor3-first=H.|title=The Dinosauria|edition=1st|publisher=Indiana University Press|pages=416–425|isbn=978-0-520-06726-4}}</ref> While a basal ornithischian position outside Ornithopoda was retained by Paul Sereno in 1991, it was considered a possibly valid taxon based on its prominent anterior and posteriormost denticles.<ref name="sereno1991">{{cite journal|last=Sereno|first=P.C.|year=1991|title=''Lesothosaurus'', "Fabrosaurids," and the early evolution of Ornithischia|journal=Journal of Vertebrate Paleontology|volume=11|issue=2|pages=168–197|doi=10.1080/02724634.1991.10011386|bibcode=1991JVPal..11..168S }}</ref> Galton revised his classification of the taxon in 1994, considering it only referrable to Ornithopoda, and not closely related to ''Echinodon''.<ref name="galton1994">{{cite journal|last=Galton|first=P.M.|year=1994|title=Notes on Dinosauria and Pterodactylia from the Cretaceous of Portugal|journal=Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen|volume=194|issue=2/3|pages=253–267|doi=10.1127/njgpa/194/1994/253 |bibcode=1994NJGPA.194..253G |s2cid=247534474 }}</ref> ''Trimucrodon'' was then compared favourable by Galton in 1996 to the also Portuguese taxon ''Taveirosaurus'', previously considered a pachycephalosaur. With the later reclassifications of ''Taveirosaurus'' as more similar to nodosaurids, ''Trimucrodon'' was identified by José Ruiz-Omeñaca in 1999 to either be a member of Heterodontosauridae alongside ''Echinodon'', or a member of Nodosauridae related to ''Taveirosaurus''.<ref name="ruizomenaca1999">{{cite journal|last=Ruiz-Omeñaca|first=J.I.|year=1999|title=Dinosaurios hipsilofodóntidos (Ornithischia: Ornithopoda) en la Península Ibérica|journal=Actas de las I Jornadas Internacionales sobre Paleontología de Dinosaurios y su Entorno|pages=175–266}}</ref> While the identity as a possible heterodontosaurid was upheld by Ruiz-Omeñaca and José Canudo in 2004,<ref name="ruizomenaca2004">{{cite journal|last1=Ruiz-Omeñaca|first1=J.I.|last2=Canudo|first2=J.I.|year=2004|title=Dinosaurios ornitópodos del Cretácico inferior de la Península Ibérica|journal=Geo-Temas|volume=6|issue=5|pages=63–65}}</ref> in the same year Weishampel, Witmer and colleague David B. Norman followed their 1990 opinion on ''Trimucrodon'', placing it as a dubious ornithischian, though they noted that further study could potentially support the validity of the taxon.<ref name="norman2004">{{cite book|last1=Norman|first1=D.B.|last2=Witmer|first2=L.M.|last3=Weishampel|first3=D.B.|year=2004|chapter=Basal Ornithischia|editor-last=Weishampel|editor-first=D.B.|editor2-last=Dodson|editor2-first=P.|editor3-last=Osmólska|editor3-first=H.|title=The Dinosauria|edition=2nd|publisher=Indiana University Press|pages=325–334|isbn=978-0-520-25408-4}}</ref>
== Paleoecology == ''Trimucrodon'' was found at the top of a cliff south of Porto Dinheiro, in the lower beds of the Lournihã Formation alongside a tooth referred to the ornithischian ''Hypsilophodon'', teeth from rhamphorhynchoid pterosaurs, the crocodylomorphs ''Lusitanisuchus'' and ''Goniopholis'', the choristoderan ''Cteniogenys'', the lizard ''Saurillus'', and over 800 teeth of various groups of mammals.<ref name="ribeiro2018"/> Other deposits from the Amoreira–Porto Novo Member at Porto Dinheiro have contained material from the sauropods ''Zby'' and ''Dinheirosaurus'', the theropods ''Lourinhanosaurus'', ''Torvosaurus'' and ''Ceratosaurus'', ornithischian remains from the stegosaur ''Miragaia'' and an intermediate member of Iguanodontia, a possible pleurosternid turtle, and scales from the fish ''Lepidotes''.<ref name="mateus2014"/>
== References == {{Reflist}}
{{Ornithischia}} {{Taxonbar|from=Q1826783}}
Category:Ornithischia Category:Dinosaur genera Category:Kimmeridgian dinosaurs Category:Lourinhã Formation Category:Taxa named by Richard A. Thulborn Category:Fossil taxa described in 1973 Category:Dinosaurs of Portugal