Huellas de dinosaurios en la costa oeste del embalse Ezequiel Ramos Mexía y alrededores (Cretácico Superior, Provincia de Neuquén, República Argentina)

Abstract

In Argentina, some of the most important dinosaur tracksites are found on the west coast of the Ezequiel Ramos Mexía reservoir, in the Neuquén province. In the last 30 years, more than 100 km of coastline have yielded hundreds of dinosaur tracks. The tracks are part of the Albian?-lower Cenomanian Candeleros Formation, Neuquén Group. An extensive study and review of the dinosaur tracks described in the past 30 years is reinterpreted and revised. Candeleroichnus canalei ichnogen. nov. ichnosp. nov. is described. A neotype is chosen for Deferrariischnium mapuchensis Calvo, 1991 and an emended diagnosis improves the ichnospecies. In addition, new information of the trackway diagnosis of Picunichnus benedettoi Calvo, 1991, such as length of pace and pace angle is given. We analyze all the dinosaur sites discovered until now and we identify all described ichnoforms such as Sousaichnium monettae, Limayichnus major, Abelichnus astigarrae and Sauropodichnus giganteus. We include unpublished figures, photos and tables of the ichnotypes.

Gregarious behaviour among non-avian theropods inferred from trackways: A case study from the Cretaceous (Cenomanian) Candeleros Formation of Patagonia, Argentina

“…Among the theropod ichnospecies documented by Calvo (1991) and Calvo and Rivera (2018) in the present unit, A. astigarrae displays the largest track size, with a mean length and width of 48.5 and 43.5 cm, respectively (FL/FW ratio = 1.11). Also, it was defined as a tridactyl track with wide and very prominent digit imprints, AT l/w ratio of 0.21 and mean stride, pace and pace angle of 255 cm, 130 cm and 146º-150º, respectively.…”

“…The finger III imprint is longer and more robust than the lateral ones and the divarication of digits II-IV is in the range of 13º and 31º (measured from Figs. 10 and 11, Calvo and Rivera, 2018). The trackways are very narrow and straight, the pace angle ranges between 175-180° while the stride and pace is in the range of 91-101cm (mean 94 cm) and 41-53 cm (mean 47 cm), respectively.…”

“…The Candeleros Formation presents one of the most diverse theropod faunas from any Cretaceous formational unit in South America (Canale et al, 2016;Novas et al, 2012Novas et al, , 2013. This Taking into account the theropod track record documented from the Cenomanian Candeleros Formation, Calvo (1991Calvo ( , 1999 and Calvo and Rivera (2018) suggested trackmakers for the registered ichnotaxa: A. astigarrae could have been produced by carcharodontosaurids; B. patagonicus and D. mapuchensis, by a medium-sized theropod (probably a coelurosaurid); and both P. benedettoi and C. canalei could have been produced by undetermined theropods. Also, Krapovickas (2010) proposed that the ichnospecies Limayichnus major Calvo, 1991 previously attributed by Calvo (1991Calvo ( , 1999 to ornithopods, is actually a theropod track: the blunt digit imprints would be due to extra anatomical issues influenced by the consistency of the soft substrate.…”

“…The ichnological record of the Candeleros Formation in the Neuquén Province is well constrained to the border of the basin (easternmost outcrops), where several dinosaur track ichnotaxa are known from the west coast area of the Ezequiel Ramos Mexía dam, close to the El Chocón locality (Calvo and Rivera, 2018, and references therein). The theropod ichnospecies known from the Candeleros Formation include Abelichnus astigarrae Calvo, 1991, Bressanichnus patagonicus Calvo, 1991, Deferrariischnium mapuchensis Calvo, 1991, Picunichnus benedettoi Calvo, 1991 Candeleroichnus canalei Calvo and Rivera, 2018. To compare the degree of mesaxony using the same criteria sensu Lockley (2009), the AT l/w ratio was calculated for the five theropod ichnotaxa known from the Candeleros Formation, and the corresponding length and width AT values were obtained by measuring from the figures from Calvo and Rivera (2018;Figs. 3, 4, 7, 10 and 11).…”

“…The only footprint record of non-avian theropods from South America that has been suggested to indicate gregariousness corresponds to tracks from the Early Cretaceous of Chile: two parallel trackways showing similar pace lengths and footprint morphologies were attributed to spinosaurids and carcharodontosaurids (Moreno et al, 2012). In Argentina, another track record from the Cenomanian Candeleros Formation (Isla del Cerrito tracksite) comprises five theropod trackways attributable to Candeleroichnus canalei (Calvo and Mazzetta, 2004;Calvo and Rivera, 2018). Three of these trackways are parallel (see Fig.…”