Teratopodus, a new ichnotaxon made by titanosaurian sauropods

Paper: New titanosaurian sauropod tracks with exceptional preservation of ungueal phalangeal prints from the Upper Cretaceous of Argentina - ScienceDirect

New titanosaurian sauropod tracks with exceptional preservation of ungueal phalangeal prints from the Upper Cretaceous of Argentina | Request PDF (researchgate.net)

Abstract. A new titanosaur sauropod ichnotaxon named Teratopodus malarguensis gen. et sp. nov is erected based on a unique association of 10 characters. It is represented by new tracks discovered in the upper section of the Anacleto Formation outcropping in the southern Mendoza Province (middle Campanian, Neuquén Basin). Teratopodus diagnosis includes pes tracks with suboval shaped, with a slightly obtuse ‘V-shaped’ heel and three large claws impressions laterally deflected corresponding to the digits I, II and III; and symmetrical kidney-shaped manus tracks with a slightly concave posterior border. Teratopodus has a medium-gauge trackway and a medium degree of heteropody (∼1/3). In addition, a new characterization of the heels impressions in sauropod tracks is proposed here including the postero-latero-medial angle (PLM°); according to this, Teratopodus pes track can be classified into slightly ‘V-shaped’ heel (PLM° = 95°–100°). The trackmakers are two titanosaurs specimens of relatively small-medium sized of ca. 11 m and 14 m length. These tracks are preserved in a poorly drained floodplain deposits with ephemeral channels controlled by flash flood episodes. In this context, the trackmakers walked from a humid ground to a more flooded one, leaving behind one of the best-preserved pes tracks ever recorded in South America.

 

PALEOENVIRONMENTAL CONTEXTS OF SOUTH AMERICAN CRETACEOUS SAUROPODS TRACKS

The ichnological Cretaceous sauropod record of South America is analyzed for the first time in relation with skeletal and paleoenvironmental data. The updated database includes 39 tracksites and 71 valid species (53 titanosaurs and 18 non-titanosaurs) from Colombia, Ecuador, Peru, Chile, Brazil and Argentina. The track and bone records analyzed evidence a relationship with continental environments, specifically with fluvial ones. This is observed in all Sauropoda records, indicating an ecological association of the Cretaceous sauropods for these environments. In addition, the paleogeographic reconstruction integrating these records does not evidence any correlation between the distribution of sauropods and the latitudinal range. During the late Campanian–Maastrichtian interval, when the Atlantic transgression event was established, the titanosaur record started to show a singular panorama. The tracksites are preserved not only in continental paleoenvironments but also in marginal-marine ones, being the only last records of titanosaurs associated with that environment in South America. Both the paleoecological aspects based on sauropod Cretaceous record and the paleoenvironmental data collected in this work support the hypothesis that these tracksites were used by titanosaurs as ‘transit areas’ to move among the environments they inhabited.

South America during the Late Cretaceous (Maastrichtian) showing schematically the distribution of the first Atlantic marine transgression (Fig. 5, Tomaselli et al. 2021).

Comments: This study is based on a careful recording of all the findings, which are mentioned in two supplementary tables, one of footprints and the other of bones. A first thing we see is that many of the published records have focused on purely systematic paleontological aspects, leaving aside detailed sedimentological and taphonomic studies. It is therefore necessary to promote this type of study in all dinosaur finds. A second important aspect is that the record shows us a direct correlation between sauropods and fluvial environments and, to a lesser extent, lake environments. There are, to date, no bone deposits in marginal marine facies, which indicates that most likely, South American sauropods (most titanosaurs) did not inhabit marginal marine environments, and their footprints only evidence their transit, when the epicontinental sea of ​​the end of the Cretaceous covered more than half of the continent. This reduction in terrestrial environments produced a reduction in the resources available for sauropods (space and vegetation).

Arackar, a new titanosaur from Chile

In the 2021 we published a new and a relativelly small sauropod dinosaur discovered in the desert of Atacama, Chile. We named this new species Arackar licanantay, and the news was spread throughout the world. The presence of "small" titanosaurs such as Arackar from Chile and Saltasaurus, Neuquensaurus and Rocasaurus from Argentina, present at the end of the Cretaceous, seems to indicate a reduction in size of these herbivores before their extinction.

Schematic representation of the skeleton of Arackar licanantay gen. et sp. nov. Preserved bones are highlighted. Modified scheme from Hechenleitner et al. (2020). Human scale ¼ 1.7 m (Fig. 3, Rubilar-Rogers et al. 2021).

Strict consensus tree based on a data matrix of 87 taxa and 405 characters recovered Arackar licanantay as a derived lithostrotian titanosaur, placing it as a sister taxon of Isisaurus colberti and close to Rapetosaurus krausei (500 MPTs of 1323 steps, CI: 0.367; RI: 0.721). (Fig. 12 from Rubilar-Rogers et al. (2021)

Abstract. A new lithostrotian sauropod, Arackar licanantay gen. et sp. nov. is described based on a partial skeleton from the Upper Cretaceous (Campanian–Maastrichtian) beds of the Hornitos Formation, Atacama Region, northern Chile. The holotype consists of axial (cervical and dorsal vertebrae) and appendicular (humerus, femur and ischium) elements of a sub-adult specimen (ca. 6.3 m long). Autapomorphies characterizing this new titanosaur include: middle neural arches with wide and tall centroprezygapophyseal fossa + parapophyseal centroprezygapophyseal fossa (cprf + pacprf) extending on the entire anterior faces of the pedicles, but not above the neural canal, and reduced spinopostzygapophyseal laminae, shorter than the postzygapophyseal facet length. A phylogenetic analysis based on a data matrix of 87 taxa and 405 characters recovered Arackar as a derived lithostrotian titanosaur, placing it in a clade that includes Rapetosaurus + (Arackar + Isisaurus). This is the third dinosaur named from Chile and the third titanosaur from the western side of the Andes in South America.

REFERENCES

Rubilar-Rogers, D.; Vargas, A. O.; González Riga, B.; Soto-Acuña, S.; Alarcón-Muñoz, J.; Iriarte-Díaz, J.; Arévalo, C.; Gutstein, C. S. (2021). Arackar licanantay gen. et sp. nov. a new lithostrotian (Dinosauria, Sauropoda) from the Upper Cretaceous of the Atacama Region, northern Chile. Cretaceous Research. doi:10.1016/j.cretres.2021.104802. 

Arackar licanantay gen. et sp. nov. a new lithostrotian (Dinosauria, Sauropoda) from the Upper Cretaceous of the Atacama Region, northern Chile - ScienceDirect

SCIENTIFIC OUTREACH

2021. Hallan fósiles de una nueva especie de titanosaurio que vivió a fines del Cretácico en la región de Atacama - (conicet.gov.ar)

2021. DIARIO LA NACION. Presentan una nueva especie de dinosaurio chileno: el Arackar licanantay - La Nación (lanacion.cl)

2021. DIARIO CLARIN. Un argentino participó del descubrimiento de una nueva especie de dinosaurio en Chile (clarin.com)

2021. DIARIO PAGINA 12. Bernardo González Riga  | HECHO EN CASA  | Página12 (pagina12.com.ar)

2021. DIARIO LOS ANDES. Gran hallazgo: un mendocino de la UNCuyo descubrió uno de los últimos titanosaurios en Chile | Sociedad (losandes.com.ar)

2021. DIARIO MDZ. Descubren restos de un dinosaurio nunca visto y un argentino participa del estudio - MDZ Online (mdzol.com)

2021. DIARIO VIA PAIS. Histórico hallazgo: mendocino descubre un Titanosaurio en el desierto chileno de Atacama | Vía Mendoza (viapais.com.ar)