The Anacleto Formation is a geologic formation with outcrops in the Argentine Patagonian provinces of Mendoza, Río Negro, and Neuquén. It is the youngest formation within the Neuquén Group and belongs to the Río Colorado Subgroup. Formerly that subgroup was treated as a formation, and the Anacleto Formation was known as the Anacleto Member.Sánchez et al. (2006)
The type locality of this formation lies west of the city of Neuquén. At its base, the Anacleto Formation conformably overlies the Bajo de la Carpa Formation, also of the Río Colorado Subgroup, and it is in turn unconformably overlain by the Allen Formation of the younger Malargüe Group.Fossa Mancini et al. (1938), Leanza et al. (2004)
The Anacleto Formation varies between thick, and consists mainly of claystones and mudstones, purple and dark red in color, deposited in fluvial, lacustrine and floodplain environments. Geodes are often found scattered throughout this formation.Leanza et al. (2004), Sánchez et al. (2006)
Fossil content
The following animals are known from bones found in the Anacleto Formation: several species of lizards several species of mammals
Crocodylomorphs Crocodylomorphs reported from the Anacleto Formation Genus Species Presence Material Notes ImagesGasparinisuchusG. peirosauroidesCañadón Amarrillo, south Malargüe city, Mendoza Province.PV-CRIDC-12 (right premaxilla and maxilla, isolated teeth, and part of the postcranial skeleton).A peirosaurid also known from the Bajo de la Carpa Formation, originally referred to Peirosaurus
Dinosaurs Ornithischians Ornithischians reported from the Anacleto Formation Genus Species Stratigraphic position Presence Material Notes ImagesGasparinisauraG. cincosaltensisCinco Saltos, Río Negro Province.Multiple specimens.A small ornithopod.
Sauropods Nests of dinosaur eggs, many with preserved embryos inside, have been discovered in large quantities at the famous Auca Mahuevo locality, and have been attributed to titanosaurs.Salgado et al. (2005), Sánchez et al. (2006)
Sauropods reported from the Anacleto Formation Genus Species Stratigraphic Position Presence Material Notes ImagesAntarctosaurusA. wichmannianusA titanosaur.BarrosasaurusB. casamiquelaiLowerNeuquén Province.Vertebrae.A titanosaur.ChadititanC. calvoi LowerGeneral Roca city, Río Negro Province. A few fragment holotype consists of caudal vertebrae, partial humeri, femur bone, ulna, and pubis.A titanosaur. LaplatasaurusL. araukanicusUppermostSeveral localities in Patagonia.Multiple specimens.A titanosaur.NarambuenatitanN. palomoiLowerRemains of a subadult.A titanosaur.NeuquensaurusN. australisUppermostCinco Saltos, Río Negro Province. Six caudal vertebrae.A saltasaurine.PitekunsaurusP. macayai"Braincase, left frontal, one tooth, four cervical vertebrae, three dorsal vertebrae, four caudal vertebrae, right ulna and scapula, proximal extreme of left femur, rib fragments and uncertain remains".A titanosaur.TeratopodusT. malarguensisSouthern Mendoza Province.Footprint trackways.A titanosaur ichnotaxon.
Theropods The oldest known unequivocal bird footprints from South America were discovered in the Anacleto Formation. The small footprints were tentatively assigned to the ichnogenus Aquatilavipes and might have been produced by Patagopteryx (whose fossils were only found in the Bajo de la Carpa Formation however) or some unknown wader-like bird; they lack a hind toe. Ignotornis refers to similar footprints made by larger birds with a small hind toe; they might have been left by Neuquenornis, but this is also only known from the Bajo de la Carpa Formation. Footprints of these two ichnogenera have also been found elsewhere, but it must be understood that assignment to the same ichnogenus does not imply a close relatedness of the organisms that produced these traces, only a similar morphology.Coria et al. (2002), Lockley et al. (2006)
Even smaller and somewhat unusual footprints assigned to Barrosopus are only known from the Anacleto Formation. They were almost certainly made by some tiny theropod, but whether this was a bird is not quite clear: the innermost front toes of the animal leaving these tracks attached in a position higher than the others. In that, and in their dimensions, they are a very close match for the odd-footed enantiornithine bird Yungavolucris brevipedalis, but this is only known from the Maastrichtian Lecho Formation which is some 10 million years younger.Chiappe (1993), Coria et al. (2002), Lockley et al. (2006)
Theropods reported from the Anacleto Formation Genus Species Stratigraphic Position Presence Material Notes ImagesAbelisauridaeIndeterminateLowerNorthwest Patagonia.MPCN-PV 69, consisting of a partial premaxilla, fragmentary vertebrae, proximal portion of both humeri, distal portion of the pubis, and an incomplete pedal ungual.An indeterminate abelisaurid.AbelisaurusA. comahuensisLago Pellegrini stone quarries.Skull.An abelisaurid, originally thought to be from the Allen Formation.AerosteonA. riocoloradensis"Cañadon Amarillo (S 37.5°, W 70.5°), north of Cerro Colorado, 1 km north of the Río Colorado near the southern border of Mendoza Province, Argentina."Skeletal remains.A megaraptorid.AucasaurusA. garridoiUpperAuca Mahuevo.Skeleton of an adult (MCF-PVPH-236).An abelisaurid.Megaraptora indet.IndeterminateUpperAuca Mahuevo.MCF-PVPH-416, a fragmentary pubic boot with unfused proximal symphysial contact.A large megaraptoran.
Squamates Squamates reported from the Anacleto Formation Genus Species Presence Material Notes ImagesDinilysiaD. sp.Aguada Toledo, south of Mari Menuco Lake.24 articulated mid-posterior trunk vertebrae with the base of their respective ribs (UNC-CIP 1).A large snake.
Testudines Testudines reported from the Anacleto Formation Genus Species Stratigraphic Position Presence Material Notes ImagesProchelidellaP. palomoiAguada Grande site, Neuquén Province.A partially preserved skull, carapace remains, an almost complete plastron, and a left ilium (MAU-Pv-AG-452).A chelid turtle. YaminuechelysY. aff. maiorLower Neuquén Province.Two specimens (MAU-Pv-N-475 & MAU-Pv-PR-455). A long-necked chelid turtle.
See also
List of fossil sites Los Alamitos Formation Los Blanquitos Formation Adamantina Formation
References
Bibliography Chiappe, Luis M. (1993): Enantiornithine (Aves) Tarsometatarsi from the Cretaceous Lecho Formation of Northwestern Argentina. American Museum Novitates 3083: 1-27. [English with Spanish abstract] PDF fulltext Coria, Rodolfo A.; Currie, Philip J.; Eberth, David & Garrido, Alberto (2002): Bird footprints from the Anacleto Formation (Late Cretaceous), Neuquén, Argentina. Ameghiniana 39(4): 453-463. [English with Spanish abstract] PDF fulltext
Lockley, Martin; Matsukawa, Masaki; Ohira, Hiroto; Li, Jianjun; Wright, Joanna; White, Diane & Chen, Peiji (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: Salgado, L.; Coria, R.A. & Chiappe, Luis M. (2005): Osteology of the sauropod embryos from the Upper Cretaceous of Patagonia. Acta Palaeontologica Polonica 50(1): 79–92. PDF fulltext
Further reading S. Brizuela and A. Albino. 2011. A Scincomorpha lizard from the Campanian of Patagonia. Cretaceous Research 32:781-785 I. A. Cerda. 2008. Gastroliths in an ornithopod dinosaur. Acta Palaeontologica Polonica 53(2):351-355 L. M. Chiappe, R. A. Coria, L. Dingus, F. Jackson, A. Chinsamy and M. Fox. 1998. Sauropod dinosaur embryos from the Late Cretaceous of Patagonia. Nature 396:258-261 R. A. Coria and L. M. Chiappe. 2000. Un nuevo terópodo abelisaurio de la Fm. Río Colorado (Cretácico Superior) de la Provincia del Neuquén [A new abelisaur theropod from the Río Colorado Fm. (Upper Cretaceous) of Neuquén province]. Actas XVI Jornadas Argentinas de Paleontología de Vertebrado, San Luis, Argentina 13 L. S. Filippi and A. C. Garrido. 2012. Nuevo registro del género Dinilysia (Squamata, Serpentes) para la Formación Anacleto (Campaniano inferior-medio), Rincón de los Sauces, Neuquén, Argentina. Ameghiniana 49(1):132-136 B. J. González Riga. 2011. Speeds and stance of titanosaur sauropods: analysis of Titanopodus tracks from the Late Cretaceous of Mendoza, Argentina. Anais da Academia Brasileira de Ciências 83(1):279-290 A. M. Praderio, A. G. Martinelli, and C. R. A. Candeiro. 2008. Mesoeucrocodilos en el Cretácico de Malargüe: primer registro de Peirosaurus tormini (Crocodyliformes, Peirosauridae) para la provincia de Mendoza (Argentina). Actas del 4to. Encuentro Internacional del International Center of Earth Sciences (E-ICES-4), Malargüe, Mendoza 1-7 L. Salgado, S. Apesteguía, and S. Heredia. 2005. A new specimen of Neuquensaurus australis, a Late Cretaceous saltasaurine titanosaur from North Patagonia. Journal of Vertebrate Paleontology 25(3):623-634 L. Salgado, R. A. Coria, and S. E. Heredia. 1996. Nuevos materiales de ornitópodos (Ornithischia) en la Formación Rio Colorado (Cretácico Superior) de la Provincia de Rio Negro [New materials of ornithopods (Ornithischia) in the Rio Colorado Formation (Upper Cretaceous) of Rio Negro province]. Ameghiniana 33(4):471 P. C. Sereno, R. N. Martínez, J. A. Wilson, D. J. Varricchio, O. A. Alcober and H. C. E. Larsson. 2008. Evidence for avian intrathoracic air sacs in a new predatory dinosaur from Argentina. PLoS ONE 3(9):e3303:1-20