Ricardo N MartinezNational University of San Juan | UNSJ · Instituto y Museo de Ciencias Naturales
Ricardo N Martinez
Doctor en Ciencias Geológicas
About
78
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Introduction
Additional affiliations
January 1995 - present
Position
- Chief of Vertebrate Paleontology Section and Curator of the Collection of Vertebrate Paleontology
Publications
Publications (78)
Upper Triassic rocks in northwestern Argentina preserve the most complete record of dinosaurs before their rise to dominance in the Early Jurassic. Here, we describe a previously unidentified basal theropod, reassess its contemporary Eoraptor as a basal sauropodomorph, divide the faunal record of the Ischigualasto Formation with biozones, and brack...
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...
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...
The early evolution of diapsid reptiles is marked by a deep contrast between our knowledge of the origin and early evolution of archosauromorphs (crocodiles, avian and non-avian dinosaurs) to that of lepidosauromorphs (squamates (lizards, snakes) and sphenodontians (tuataras)). Whereas the former include hundreds of fossil species across various li...
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...
Dinosauria debuted on Earth’s stage in the aftermath of the Permo-Triassic Mass Extinction Event, and survived two other Triassic extinction intervals to eventually dominate terrestrial ecosystems. More than 231 million years ago, in the Upper Triassic Ischigualasto Formation of west-central Argentina, dinosaurs were just getting warmed up. At this...
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...
En el año 1964 se creó por ley provincial el Museo de Ciencias Naturales de San Juan. Esta ley fue una reacción al drenaje de fósiles
que se sacaban de la provincia, después del descubrimiento científico de Ischigualasto en 1958, porque no había en San Juan un repositorio
habilitado. Sancionada la ley, el Museo solo existió en el papel por varios a...
En el sureste de la provincia de San Juan y noroeste de la provincia de San Luis afloran las sucesiones estratigráficas de las cuencas Marayes-El Carrizal (Triásico-Jurásico) y San Luis (Cretácico). El límite entre ambas fue establecido en la sierra del Gigante en la discordancia de la base de la Formación Los Riscos, asignada al Cretácico por crit...
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...
Aetosaurs are an early-diverging clade of “crocodile-line” archosaurs whose oldest records come from Argentina and Brazil. Articulated skeletons of aetosaurs are rare, but offer insight into their paleobiology. We describe here an incomplete, articulated posterior skeleton of an aetosaur from the Upper Triassic Ischigualasto Formation of San Juan P...
In this contribution we introduce a new Late Triassic archosaur, Incertovenator longicollum gen. et sp. nov., with an unusual combination of character states that are present in certain early avemetatarsalian and pseudosuchian archosaur clades. The holotype consists of a partial postcranial skeleton, preserving most of the axial skeleton and displa...
The Late Triassic represents many of the most critical biotic crises in life-history (from Carnian to the end-Triassic extinction, ETE). Some hypotheses propose that these life changes were linked with shifts in the environmental setting during the initial stages of the Pangea breakup. These crises were likely not sudden events but a series of step...
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...
Beaks are an edentulous dietary modification present in numerous forms in turtles, birds, cephalopods, and some actinopterygian fishes today. Beaks have a rich fossil record and have independently evolved at least nine times over the past 300 million years in early reptiles, dinosaurs and their relatives, and crocodile and mammal relatives. Here, w...
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 describe a new probainognathian cynodont, Pseudotherium argentinus, from the early Late Triassic Ischigualasto Formation of Argentina. Pseudotherium adds to a growing assemblage of small Triassic cynodonts that offers new insight into events leading up to the origin of crown Mammalia and the successively more inclusive Mammaliaformes and Mammali...
Crocodylomorpha es un clado de arcosaurios que representa el único linaje de pseudosuquios que sobrevive al límite Triásico-Jurásico e incluye a los cocodrilos vivientes. Uno de los taxones más antiguos de este grupo es Trialestes romeri Reig 1963, proveniente de la Fm. Ischigualasto. En el presente trabajo se describe un nuevo crocodilomorfo no-cr...
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...
Ecteniniidae comprises an endemic radiation of carnivore probainognathian cynodonts from the Late Triassic of South America. Three taxa have been included in this clade: Ecteninion lunensis Martínez et al., 1996 and Diegocanis elegans Martínez et al., 2013 from Argentina, and Trucidocynodon riograndensis Oliveira et al., 2010 from Brazil. Herein, a...
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...
Protosuchids are known from the Late Triassic to the Early Cretaceous and form a basal clade of Crocodyliformes. We report here a new protosuchid crocodyliform, Coloradisuchus abelini, gen. et sp. nov., from the middle Norian Los Colorados Formation, La Rioja, northwestern Argentina. Our phylogenetic analysis recovers Coloradisuchus abelini within...
Paracrocodylomorpha es un clado de arcosaurios pseudosuquios que incluye a los crocodilomorfos, poposauroideos y varios taxones tradicionalmente conocidos como "rauisuquios". En el presente trabajo se describe un nuevo paracrocodilomorfo (PVSJ 397) proveniente de niveles medios del miembro Cancha de Bochas en los afloramientos australes de la Forma...
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...
Dinosaurs include two main branches, Ornithischia and Saurischia, with a minimum divergence time of approximately 231 Ma (late Carnian) based on the age of the oldest known members of the group. Argentinean non-dinosaurian dinosauromorphs are known from the Upper Triassic Chañares, Ischigualasto and Quebrada del Barro formations, including five or...
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...
Dinosaurs are unique among terrestrial tetrapods in their body sizes, which range from less than 3 gm in hummingbirds to 70,000 kg or more in sauropods. Studies of the microstructure of bone tissue have indicated that large dinosaurs, once believed to be slow growing, attained maturity at rates comparable to or greater than those of large mammals....
Background
Dinosaurs are unique among terrestrial tetrapods in their body sizes, which range from less than 3 gm in hummingbirds to 70,000 kg or more in sauropods. Studies of the microstructure of bone tissue have indicated that large dinosaurs, once believed to be slow growing, attained maturity at rates comparable to or greater than those of lar...
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,...
Significance
Uncertainties in reported ⁴⁰ Ar/ ³⁹ Ar dates from the Ischigualasto Formation of Argentina allow its dinosaur-bearing fauna to be Norian in age and possibly contemporaneous with some of the older U-Pb dated dinosaur-bearing units in the Chinle Formation of the American Southwest. Our magnetochronology of the previously undated Los Colo...
FIRST RECORD OF COXOFEMORAL DYSPLASIA IN A LATE TRIASSIC RYNCHOSAUR. Paleopathology deals with diseases that have left evidence in the fossil record. This field includes the identification of the pathology, and its consequences that on the animal that suffered it. We present the first record of a coxofemoral dysplasia in an Upper Triassic rhynchosa...
The record of non-mammaliaformes eucynodonts from the Carnian-Norian Ischigualasto Formation is diverse and abundant, including a medium to large size herbivore and small carnivores. Here is described a new small eucynodont from the
Ischigualasto Formation, on the basis of a partial skull. The new taxon is characterized by palatal process of the pr...
Paleopathology deals with diseases that have left evidence in the fossil record. This field includes the identification of the pathology, and its consequences that on the animal that suffered it. We present the first record of a coxofemoral dysplasia in an Upper Triassic rhynchosaur, being also the first identification of this pathology in the foss...
Large-diameter ichnofossils comprising three morphotypes have been identified in the Upper Triassic Ischigualasto and Los Colorados formations of northwestern Argentina. These burrows add to the global record of the early appearance of fossorial behavior during early Mesozoic time. Morphotypes 1 and 2 are characterized by a network of tunnels and s...
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...
We describe the basal sauropodomorph Eoraptor lunensis, based on the nearly complete holotypic skeleton and referred specimens, all of which were discovered in the Cancha de Bochas Member of the Ischigualasto Formation in northwestern Argentina. The lightly built skull has a slightly enlarged external naris and a spacious antorbital fossa with a pr...
The proterochampsids are a group of crocodile-like archosauri-forms usually considered as one of the potential successive sister taxa of the crown group Archosauria (e.g., Sereno and Ar-cucci, 1990; Sereno, 1991; Dilkes and Sues, 2009; Ezcurra et al., 2010). The clade is currently endemic to the late Middle and early Late Triassic of South America....
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...
La Formación Cañón del Colorado aflora en el extremo sur de la sierra de Mogna, al noreste de la provincia de San Juan. Esta formación ha sido objeto de debate en cuanto a su estratigrafía y edad. En el presente trabajo, se caracterizó la Formación Cañón del Colorado en base a cinco perfiles estratigráficos (P1, P2, P3, P4, y P5) distribuidos unifo...
The Cañón del Colorado Formation crops out in the south of Sierra de Mogna, northeast of San Juan province. The stratigraphy and age of this formation has been controversial. In this paper, the Cañón del Colorado Formation is characterized using five stratigraphic sections (P1, P2, P3, P4, P5) uniformly distributed along the outcrops. The P3 sectio...
Herrerasauridae comprises a basal clade of dinosaurs best known from the Upper Triassic of Argentina and Brazil, which have yielded remains of Herrerasaurus ischigualastensis and Staurikosaurus pricei, respectively. Systematic opinion regarding the position of Herrerasauridae at the base of Dinosauria has varied. Here we describe a new herrerasauri...
Prosauropods are basal sauropodomorphs that were the major terrestrial faunal components from the Norian until their extinction during the Toarcian. Their status as a natural group is debatable. In the present work I describe Adeopapposaurus mognai, a new sauropodomorph from the Cañón del Colorado Formation, in northwestern Argentina. Diagnostic au...
The earliest dinosaurs are from the early Late Triassic (Carnian) of South America. By the Carnian the main clades Saurischia and Ornithischia were already established, and the presence of the most primitive known sauropodomorph Saturnalia suggests also that Saurischia had already diverged into Theropoda and Sauropodomorpha. Knowledge of Carnian sa...
Living birds possess a unique heterogeneous pulmonary system composed of a rigid, dorsally-anchored lung and several compliant air sacs that operate as bellows, driving inspired air through the lung. Evidence from the fossil record for the origin and evolution of this system is extremely limited, because lungs do not fossilize and because the bello...
