Bernardo J. González Riga

A gigantic new dinosaur from Argentina and the evolution of the sauropod hind foot.

Titanosauria is an exceptionally diverse, globally-distributed clade of sauropod dinosaurs that includes the largest known land animals. Knowledge of titanosaurian pedal structure is critical to understanding the stance and locomotion of these enormous herbivores and, by extension, gigantic terrestrial vertebrates as a whole. However, completely preserved pedes are extremely rare among Titanosauria, especially as regards the truly giant members of the group. Here we describe Notocolossus gonzalezparejasi gen. et sp. nov. from the Upper Cretaceous of Mendoza Province, Argentina. With a powerfully-constructed humerus 1.76 m in length, Notocolossus is one of the largest known dinosaurs. Furthermore, the complete pes of the new taxon exhibits a strikingly compact, homogeneous metatarsus—seemingly adapted for bearing extraordinary weight—and truncated unguals, morphologies that are otherwise unknown in Sauropoda. The pes underwent a near-progressive reduction in the number of phalanges along the line to derived titanosaurs, eventually resulting in the reduced hind foot of these sauropods.

A New Titanosaur (Dinosauria, Sauropoda) from the Upper Cretaceous (Cerro Lisandro Formation) of Mendoza Province, Argentina

Abstract. Quetecsaurus rusconii gen. et sp. nov. is a new titanosaur (Dinosauria, Sauropoda) from the Neuquén Basin of Mendoza Province, Argentina. The specimen comes from red mudstones of the Cerro Lisandro Formation (middle-late Turonian, Upper Cretaceous), and is the first sauropod with well-preserved remains to be discovered in this formation. The holotype includes a postorbital, teeth, the atlas, a posterior cervical vertebra, an incomplete dorsal vertebra, a posterior caudal centrum, dorsal ribs, a coracoid, fragments of a humerus, radius and ulna, and five metacarpals. It is characterized by the following combination of autapomorphies: (1) intercentrum of atlas with a prominent anteroventral border and expanded posteroventral processes; (2) posterior cervical neural spines with incipient lateral expansions; and (3) humerus with strongly sigmoid proximal border, rounded proximomedial border, and angular proximolateral corner. A preliminary cladistic analysis placed Quetecsaurus as a sister taxon of Lognkosauria (Mendozasaurus + Futalognkosaurus). Quetecsaurus shares with the lognkosaurs the presence of cervical neural spines with ‘lateral laminae’, but relatively reduced in comparison with those taxa. This discovery provides new information on the diagnosis of Lognkosauria within South American titanosaurs.

Un nuevo hadrosáurido (Dinosauria, Ornithopoda) de la Formación Allen, Provincia de La Pampa, Argentina

Abstract. A NEW HADROSAURID (DINOSAURIA, ORNITHOPODA) FROM ALLEN FORMATION, LA PAMPA PROVINCE, ARGENTINA. New studies of a Hadrosauridae specimen collected in the Allen Formation, Late Campanian/Early Maastrichthian from La Pampa Province, Argentina, allow recognizing a new taxon, Lapampasaurus cholinoi gen. et sp. nov., which is diagnosed by the following combination of characters: anterior cervical vertebrae with lateral foramina on the dorsal side of the diapophyses, scapula with laterally sharp deltoid crest and convex dorsal surface, pedal ungual phalanx longer than wide with superficial grooves and foramina, and shallow, longitudinal ventral ridge. The identification of Lapampasaurus as a member of Hadrosauridae is confirmed by the recognition of several synapomorphies, such as cervical neural arches with zygapophysial peduncles that elevate above the neural canal, long and dorsally arched postzygapophyses, coracoid relatively small when compared with the scapula, with concave anterior margin and well developed bicipital knob, and hoof-shaped pedal ungual phalanx. The record of Lapampasaurus in the Late Cretaceous of Patagonia suggests the presence of a more diverse hadrosaurid fauna than previously recorded.

Sharks (Neoselachii) and palynomorphs from Mendoza (Argentina): new evidence of the Late Cretaceous Atlantic marine transgression

Prámparo, M.B., Cione, A.L. & Gonzalez Riga, B., 2013. Sharks (Neoselachii) and palynomorphs from Mendoza (Argentina): new evidence of the Late Cretaceous Atlantic marine transgression. Alcheringa 38, 000–000. ISSN 0311–5518. Neoselachian (modern shark) teeth and palynomorphs have been recovered from the Late Cretaceous Jagüel Formation in the Province of Mendoza, Argentina. The fossiliferous beds were deposited during the Atlantic transgression that covered northern Patagonia and other parts of South America from the Maastrichtian to the Danian. Teeth of several lamniform sharks are attributed to the anacoracid Squalicorax pristodontus and cf. Serratolamna serrata of indeterminate familial affinity. These taxa became extinct at the end of the Cretaceous and confirm the late Maastrichtian age previously assigned to the Jagüel Formation in this northwestern part of the Neuquén Basin. For the first time, the selachian faunas are described together with algae and dispersed organic matter assemblages (palynofacies), revealing new elements of the neritic biota leading up to the Cretaceous–Paleogene (K–Pg) mass extinction in South America. The palynoflora consists exclusively of the prasinophyte algae Tasmanites, Cymatiosphaera and Pterospermella, indicative of stratified saline waters. Dispersed organic components in the profile (mainly opaque equidimensional phytoclasts and prasinophytes) are consistent with an inner neritic environment, with evidence (a great variety of particle sizes, lath-shaped phytoclasts increasing slightly in number and decreasing number of marine components) of slightly more nearshore conditions towards the upper part of the profile. These marine biotas confirm the presence of an epeiric sea over northern Patagonia, which extended westwards to the volcanic arc on the western flank of the Andean Cordillera in Mendoza. Mercedes B. Prámparo [mprampar@mendoza-conicet.gov.ar], IANIGLA-CONICET, CCT-Mendoza. Avda. R. Leal s/n, Parque Gral. San Martín, (5500) Mendoza, Argentina; Alberto Luis Cione [acione@museo.fcnym.unlp.edu.ar], División Paleontología de Vertebrados. Museo de La Plata. 1900 La Plata, Argentina; Bernardo González Riga [bgonriga@mendoza-conicet.gov.ar] IANIGLA-CONICET, CCT, Mendoza. Avda. R. Leal s/n, Parque Gral. San Martín, (5500) and ICB, Universidad Nacional de Cuyo, Argentina. Received 28.5.2013, revised 17.9.2013, accepted 24.9.2013.