The Plottier Formation is a geologic formation that outcrops in the Argentine Patagonian provinces of Río Negro and Neuquén. It is the younger of two formations belonging to the Río Neuquén Subgroup within the Neuquén Group of the Neuquén Basin, with the oldest rocks dating from the late Coniacian and its youngest maybe from the very start of the Santonian. Formerly, that subgroup was treated as a formation, and the Plottier Formation was known as the Plottier Member.Sánchez et al., 2006
Description A section near the Neuquén City airport, north of the town of Plottier, is the type locality of the Plottier Formation.Fossa Mancini et al., 1938 At its base, this formation grades into the Portezuelo Formation, and it is in turn overlain conformably by the Bajo de la Carpa Formation, a unit of the Río Colorado Subgroup.
The Plottier Formation is the thinnest formation within the Neuquén Group, with a maximum thickness of only . It is differentiated from the underlying Portezuelo Formation primarily by its higher content of argillites (mud deposits) and was deposited under fluvial conditions. In 2006, a detailed lithostratigraphic and paleoecological study of a section of the Plottier Formation was published. This section contained alluvial deposits laid down by what was essentially a low-gradient wandering river throughout the millions of years, but often was of a single-channel type with little meandering.Leanza et al., 2004
Fossil content
Few animal fossils are known from this formation, including:Plottier Formation at Fossilworks.org Crocodyliformes Crocodyliformes reported from the Plottier Formation Genus Species Presence Material Notes ImagesCrocodyliformes indet.IndeterminateEl AnfiteatroSeven osteoderms (MPCA-AT 251–257) Right dentary fragment (MPCA-AT 75)Resembles peirosaurids such as Peirosaurus and UberabasuchusLomasuchusL. palpebrosusEmbalse Cerros ColoradosSkull and partial mandibular ramusA peirosaurid, specimen originally claimed to originate from the Rio Colorado formation.Mesoeucrocodylia indet.IndeterminateYacimiento NarambuenaPartial skeleton (MAU-PV-N-280)Subadult specimen showing both derived and primitive traitsPeirosauridae indet.IndeterminatePuesto HernándezPartial skeleton (MAU-Pv-PH-437)A peirosaurid
Dinosaurs Ornithischians A footprint track of an ornithopod is known from the Middle Loma de la Lata site. Ornithischians reported from the Plottier Formation Genus Species Presence Material Notes ImagesOrnithopoda indet.IndeterminateEl AnfiteatroA pedal ungual phalanx (MPCA-AT 261)An ornithopod roughly the size of NotohypsilophodonIndeterminatePuesto Hernández quarryPartial dorsal neural arch (MAU-Pv-PH-458)An ornithopod similar to Macrogryphosaurus, estimated to be 6 meters long
Sauropods 12 footprint tracks of a sauropod are known from the site of Proyecto Dino. Sauropods reported from the Plottier Formation Genus Species Presence Material Notes ImagesAeolosaurini indet.IndeterminateYacimiento NarambuenaFour articulated caudal vertebrae (MAU-Pv-N-414)A titanosaurAntarctosaurusA. giganteusAguada del CañoPartial skeleton (MLP 26-316)A titanosaurMuyelensaurusM. pecheniLoma del LinderoPartial skeleton & additional vertebraeA titanosaur, specimens originally thought to be from the Portezuelo FormationNotocolossusN. gonzalezparejasiCerro GuillermoTwo partial skeletons (UNCUYO-LD 301 & UNCUYO-LD 302)A titanosaurPetrobrasaurusP. puestohernandeziRincón de los SaucesPartial skeletonA titanosaurSauropoda indet.Indeterminate5 kilometers north of PlottierPartial right tibia (MCF-PVPH-899)A sauropodIndeterminateCerro GuillermoIncomplete skeleton (IANIGLA-PV.113)A sauropodTitanosauria indet.IndeterminateEl AnfiteatroIncomplete dorsal vertebra (MPCA-AT 024)A large titanosaurIndeterminate5 kilometers north of PlottierLeft femur and partial ribs (MCF-PVPH-889) Right fibula (MCF-PVPH-900)Remains of titanosaurs
Theropods Theropods reported from the Plottier Formation Genus Species Presence Material Notes ImagesAbelisauridae indet.IndeterminateCañadon AmarilloToothAn abelisaur tooth formerly thought to be part of the holotype specimen of AerosteonIndeterminateEl AnfiteatroTooth (Endemas-PV 16)An abelisaur, tooth originally reported as that of a carcharodontosaurid in 2009 but reclassified in 2021Alvarezsauria indet.IndeterminateRincón de los SaucesRight femur (MAU-Pv-PH-453)An alvarezsaurBrachyrostra indet.IndeterminateLoma del LinderoVertebrae, teeth and possible sacrum (MAU-Pv-LL-75)An abelisaurCoelurosauria indet.IndeterminateEl AnfiteatroTwo teeth (MPCA-AT 263 & 269)A coelurosaurManiraptoriformes indet. cf. UnenlagiinaeIndeterminateEl AnfiteatroTooth (Endemas-PV 15)Possible unenlagiine tooth, though more material is needed to confirm thisTheropoda indet.IndeterminateEl AnfiteatroIncomplete caudal vertebra (MPCA-AT 082)A "moderately sized" theropod
Pterosaurs Pterosaurs reported from the Plottier Formation Genus Species Presence Material Notes ImagesThanatosdrakonT. amaruAgua del PadrilloPartial skeleton (UNCUYO-LD 307) Left humerus (UNCUYO-LD 350)An azhdarchid
Turtles Turtles reported from the Plottier Formation Genus Species Presence Material Notes ImagesChelidae? indet.IndeterminateEl AnfiteatroPlastron plate (MPCA-AT 089)A chelidLinderochelysL. rinconensisLoma de LinderoPartial skeleton (MAU-PV-LL-69)A chelid, locality originally assigned to the Rio Neuquén Subgroup with no specific formation.RionegrochelysR. caldieroiEl AnfiteatroShell elementsA chelid, type specimen first reported as an indeterminate chelid in 2009
Ichnofossils Scoyenia sp. Taenidium sp. There are also ichnofossils left on the river's mudflats, as well as fossil freshwater bivalves.
Ostracods Ostracods reported from the Plottier Formation Genus Species Presence Material Notes ImagesCypridoidea indet.IndeterminateZampalA few specimensA cypridoidIlyocyprisI. aff. bauruensisZampalA few moltsAn ilyocyprididI. cf. riograndensisZampalAn ilyocyprididI. wichmanniZampalAn ilyocyprididNeocyprideisN.? sp.ZampalAn ilyocyprididN. zampalensisBabilonia4 valvesAn ilyocyprididNeuquenocyprisN. calfucurensisBabilonia3 valve fragmentsAn ilyocyprididN. cf. minorZampalAn ilyocyprididN. nahuelniyuensisBabilonia6 valvesAn ilyocyprididN. tenuipunctataBabilonia5 adult and 3 juvenile valvesAn ilyocyprididParalimnocythereP.? sp.ZampalSeveral carapaces and valvesA limnocytheridTalicyprideinae sp.IndeterminateZampalVery scarce number of carapacesAn ilyocyprididVecticyprisV. sp.Babilonia2 valvesA limnocytheridWolburgiopsisW. cf. neocretaceaZampalA limnocytherid
Plants Plants reported from the Plottier Formation Genus Species Presence Material Notes ImagesAngiospermae? indet.IndeterminateZampalA few seedsA possible angiospermHenrisporitesH. sp.ZampalAbundant megasporesA lycopodLychnothamnusL. barbosaiZampalOver 400 microfossilsA stonewortNitellaN. sp.Zampal21 microfossilsA stonewortSpermatitesS. sp. 1ZampalSeedsAn angiospermS. sp. 2ZampalSeedsAn angiosperm
See also List of fossil sites List of dinosaur bearing rock formations
References
Bibliography (1993): Enantiornithine (Aves) Tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates 3083: 1-27. [English with Spanish abstract] PDF fulltext (2002): Bird footprints from the Anacleto Formation (Late Cretaceous), Neuquén, Argentina. Ameghiniana 39(4): 453-463. [English with Spanish abstract] PDF fulltext
(2006): Bird tracks from Liaoning Province, China: New insights into avian evolution during the Jurassic-Cretaceous transition. Cretaceous Research 27(1): 33-43. (HTML abstract). Erratum: (2005): Osteology of the sauropod embryos from the Upper Cretaceous of Patagonia. Acta Palaeontologica Polonica 50(1): 79–92. PDF fulltext