Cecilia Apaldetti

• National University of San Juan

Probainognathia is a derived lineage of cynodonts which encompass Mammalia as their crown-group. The rich record of probainognathians from the Carnian of Argentina contrasts with their Norian representation, with only one named species. Here we describe a new probainognathian, Tessellatia bonapartei gen. et sp. nov., from the Norian Los Colorados F...

Carnian (Late Triassic) deposits of South America provide the oldest unequivocal dinosaur records worldwide, most of which has been assigned to the sauropodomorph lineage. This includes Eoraptor lunensis, Panphagia protos, and Chromogisaurus novasi, from the Ischigualasto Formation, Argentina, and Saturnalia tupiniquim, Pampadromaeus barberenai, Bu...

Sauropodomorpha was an herbivorous clade of dinosaurs that lived through nearly the entire Mesozoic Era. Sauropodomorphs appeared at the end of the Triassic as small and gracile forms and evolved into the largest land animals that ever lived on Earth. This evolutionary path towards giant forms implied several skeletal modifications and anatomical i...

Pterosaurs were the first vertebrates to evolve powered flight. The timing of their origin is still debated, and hypotheses range from the end of the Permian Period, to the lower Mesozoic Era, and through to the Middle–Late Triassic epochs. Regardless of when they originated, the oldest records are restricted to the Upper Triassic Norian Stage in t...

Probainognathia is a derived lineage of cynodonts which encompass Mammalia as their crown-group. The profuse record of probainognathians from the Carnian of Argentina contrasts with their Norian representation, with only one named species. Here we describe a new probainognathian, Tessellatia bonapartei gen. et sp. nov., from the Norian Los Colorado...

Sauropodomorph dinosaurs were the dominant medium to large-sized herbivores of most Mesozoic continental ecosystems, being characterized by their long necks and reaching a size unparalleled by other terrestrial animals (> 60 tonnes). Our study of morphological disparity across the entire skeleton shows that during the Late Triassic the oldest known...

Sauropodomorpha is the first major dinosaurian group that radiated during the Triassic. During this time the group underwent major changes in body plan, including the acquisition of features related to herbivory, large body size, and quadrupedality. By the end of the Late Triassic, approximately 30 million years after the origin of dinosaurs, sauro...

The origin and homology of the turtle shell is one of the most captivating topics in amniote evolution. In this contribution, we present a new species of turtle from the Late Triassic of Argentina whose peripheral plates raise questions about the homology of these bones in turtles. The external morphology of the peripheral plates of Waluchelys cavi...

We present a systematic revision of the ‘prosauropod’ dinosaur Unaysaurus tolentinoi. Past phylogenetic treatments of this taxon have presented it as a key constituent of the low-diversity Plateosauridae. This clade, along with Massospondylidae, is currently regarded as a relatively non-controversial example of monophyly within non-sauropodan sauro...

We present a new locality with fossil woods in the southern outcrops of the Rickard Member, Carrizal Formation (Upper Triassic) of the El Gigantillo area in San Juan Province, Argentina. We analyzed the anatomical characters, systematic affinity and taphonomic conditions of permineralized trunks. A total of 58 trunks were found, although only two s...

Dinosaurs dominated the terrestrial ecosystems for more than 140 Myr during the Mesozoic era, and among them were sauropodomorphs, the largest land animals recorded in the history of life. Early sauropodomorphs were small bipeds, and it was long believed that acquisition of giant body size in this clade (over 10 tonnes) occurred during the Jurassic...

Coelophysoids are the most abundant theropod dinosaurs known from the Late Triassic through Early Jurassic and represent the earliest major radiation of Neotheropoda. Within Coelophysoidea sensu lato, the most stable clade is Coelophysidae, which are small theropods characterized by long necks, and light and kinetic skulls. Coelophysids are the mos...

Sauropod dinosaurs include the largest terrestrial animals and are considered to have uninterrupted rapid rates of growth, which differs from their more basal relatives, which have a slower cyclical growth. Here we examine the bone microstructure of several sauropodomorph dinosaurs, including basal taxa, as well as the more derived sauropods. Altho...

Los coelophysoideos son dinosaurios carnívoros que vivieron en casi todos los continentes durante el Triásico Tardío al Jurásico Temprano, y son considerados la primera radiación de Neotheropoda. A pesar de su abundante registro, en América del Sur sólo se conoce Zupaysaurus rougieri (Noriano medio de Argentina), un 'coelophysoideo' de controvertid...

Basal sauropodomorphs include the non-sauropod portion of Sauropodomorpha, which lived in all continental landmasses between the Late Triassic and Early Jurassic. The early evolution of the group is well recorded in Carnian beds of Argentina and Brazil, achieving a rapid diversification during Norian and Rhaetian, adding records from South Africa,...

The first Triassic microfossil bonebed found in Argentina is located 80 meters from the top of the Quebrada del Barro Formation in the Marayes-El Carrizal Basin, in the province of San Juan. It consists of specimens from at least 63 individuals from an anomalously high concentration of fossils distributed laterally and vertically in a meter-thick f...

The early evolution of Ornithodira -the clade including pterosaurs and dinosaurs- is poorly known. Until a decade ago, the basal radiation of Dinosauromorpha, the clade including dinosaurs and birds, was poorly understood because of the poor fossil record restricted to specimens known from the Ladinian Chañares Formation in Argentina. Over the last...

The Marayes-El Carrizal Basin, Southeast San Juan province, Argentina, is composed of a continental succession deposit in a rift basin. The classical stratigraphy of the basin is defined in ascending order as follows: Esquina Colorada, Carrizal and Quebrada del Barro Formations. Remote sensing on satellite images, as well as sedimentological and pa...

La Formación Quebrada del Barro (FQB) de la Cuenca continental Marayes-El Carrizal aflora al Sureste de la Provincia de San Juan, Noroeste de Argentina. La asociación faunística de la FQB está caracterizada por una gran diversidad de vertebrados de edad Noriano Tardío.

The cranial anatomy of the basal sauropodomorph Coloradisaurus brevis from the upper levels of the Norian Los Colorados Formation is here redescribed and comparisons made based on the holotype skull and mandible. Coloradisaurus brevis is diagnosed by most of the features proposed in the original description and an additional set of autapomorphies,...

The Quebrada del Barro Formation (QBF) is part of the continental Marayes-El Carrizal Basin, in NW Argentina. Here we report a diverse faunal assemblage recently discovered in the Quebrada del Barro Formation, along with a preliminary discussion of the taxonomic status and affinities of numerous vertebrate specimens found at two localities where th...

Sphenodontians were a successful group of rhynchocephalian reptiles that dominated the fossil record of Lepidosauria during the Triassic and Jurassic. Although evidence of extinction is seen at the end of the Laurasian Early Cretaceous, they appeared to remain numerically abundant in South America until the end of the period. Most of the known Late...

Basal sauropodomorphs from the Upper Triassic Los Colorados Formation of north-western Argentina have been known for several decades but most of them are only briefly described. New postrcanial remains of Coloradisaurus brevis, the most gracile sauropodomorph from this unit, are described here and evaluated within a phylogenetic context. These mate...

The Upper Triassic (Carnian–Norian) Ischigualasto Formation has yielded a diverse vertebrate fauna that records the initial phase of dinosaur evolution. Radioisotopic dates from ash layers within the formation provide a chronostratigraphic framework, and stratigraphic and sedimetological studies have subdivided the formation into four members and t...

We describe a partial braincase of the basal sauropodomorph Panphagia protos from the Upper Triassic (mid-Carnian) horizons of the Ischigualasto Formation. The disarticulated braincase from a subadult individual includes one frontal, both parietals, one prootic, and the supraoccipital. The frontal is longer anteroposteriorly than it is wide transve...

Basal sauropodomorphs from the Ischigualasto Formation include Eoraptor lunensis, Panphagia protos, and Chromogisaurus novasi. Few comparisons have been made between these taxa, because Eoraptor was only recently reassessed as a basal sauropodomorph and because Panphagia and Chromogisaurus were described nearly simultaneously. We describe in detail...

The Late Triassic rocks document the first steps of the early dinosaur evolutionary radiation. Although the oldest dinosaurs were not abundant in their assemblages, sauropodomorphs achieved a wide taxonomic diversity and high abundance towards the Triassic–Jurassic boundary. In South America, this pattern is documented in the Ischigualasto-Villa Un...

1) Character scorings changed for Coloradisaurus brevis in comparison with scorings provided by Yates et al. [46] (a) and Smith and Pol [45] (b). 2) Character scorings changed for Adeopapposaurus mognai in comparison with scorings provided by Sertich and Loewen [47]. 3) Scorings for all taxa analysed in the phylogenetic analyses of the modified ver...

Measurements (in millimeters) of the preserved bones of the new basal sauropodomorph Leyesaurus marayensis (PVL 706). Abbreviations: C3-7, cervical vertebrae from 3 to 7; Ca, caudal vertebra; dt, distal tarsal; mt, metatarsal; ph, phalanx; *, incomplete; ∼, deformed. (DOC)

Strict consensus of the phylogenetic analysis of sauropodomorph dinosaurs. Analysis was based on the dataset of Yates [34] modified by other authors [8], [45]–[49] and including Leyesaurus marayensis gen. et sp. nov., showing the strict consensus of 18 MPTs. Bremer decay indices are listed above the nodes and Bootstrap values are listed below the n...

Background: Argentinean basal sauropodomorphs are known by several specimens from different basins; Ischigualasto, El Tranquilo, and Mogna. The Argentinean record is diverse and includes some of the most primitive known sauropodomorphs such as Panphagia and Chromogisaurus, as well as more derived forms, including several massospondylids. Until now...