Maip macrothorax, the shadow of the death

Maip macrothorax. Image credit: Agustín Ozán

Patagonia has yielded the most comprehensive fossil record of Cretaceous theropods from Gondwana, including Megaraptora, a clade of medium-sized and highly pneumatized theropods characterized by their elongate skulls, and the formidable development of their manual claws on digits I and II. The enigmatic nature of this group has been a matter of discussion since the description of Megaraptor namunhaiquii in 1990s . Other representatives of the clade are Aoniraptor libertatem, Aerosteon riocoloradensis, Australovenator wintonensis, Murusraptor barrosaensis, Tratayenia rosalesi and Orkoraptor burkei. The phylogenetic position of Megaraptora is still controversial. But despite the lack of consensus, megaraptorans themselves remain a well-supported clade. Now, a new megaraptoran theropod dinosaur from the Upper Cretaceous of the Santa Cruz Province, Argentina, sheds light on on these enigmatic predators and their evolutionary radiation.

Maip macrothorax is a large-bodied megaraptorid from lower Maastrichtian Chorrillo Formation in Santa Cruz Province, Argentina. The holotype (MPM 21,545) includes the axis (only lacking both prezygapophyses and its right postzygapophysis), several dorsal and caudal vertebrae, three incomplete cervical ribs, numerous incomplete or fragmentary dorsal ribs, numerous gastral elements, left coracoid, distal end of a second metatarsal, and fragments of the scapula. The generic name, Maip, is derived from an evil entity in Aonikenk mythology that represents “the shadow of the death”. The specific name, macro, derives from the Greek word makrós (meaning long), and the Latin word thorax (meaning chest) in reference to its wide thoracic cavity (which has, approximately, more than 1.20 m width).

Axis of Maip in lateral (A, A´), anterior (B, B´), posterior (C, C´), dorsal (D, D´) and ventral (E, E´). Scale bar: 5 cm. From Aranciaga et al., 2022

The new specimen was discovered in 2019, but due the outbreak of the COVID-19 pandemic in early 2020 the dig was temporarily interrupted. The most striking feature of Maip is its large size. Maip macrothorax was between nine and 10 meters (30-33 feet) and weight about 5 tons. Several vertebrae and ribs of Maip show striations or rugosities interpreted as the attachment sites for the costovertebral and costotransversarium ligaments, a condition not commonly observed in other theropods.

The new study, lead by Aranciaga Rolando, recovered two new clades comprising some derived megaraptorids from South America. The first one, Clade A, comprises Megaraptor, Murusraptor, most of the Cenomanian–Turonian Patagonian forms with 6 or 7 m in length. The second one, Clade B, includes Orkoraptor, Tratayenia, Aerosteon and Maip, most of the Santonian through Maastrichtian megaraptorids from South America, with 8 or 10 m in length. This clade is supported by two synapomorphies: dorsal vertebrae with a bifurcated lamina anterior to the transverse process and forming an accessory fossa, and round and large articular facets of pre- and postzygapophyses of proximal caudal vertebrae. Additionally, the work suggests that after the Turonian, megaraptorids showed an increase in the body size and (with other theropod groups) replaced carcharodontosaurids in the role of apex predators within the Southern continents in the course of the Late Cretaceous.

 

References:

Aranciaga Rolando, A.M., Motta, M.J., Agnolín, F.L. et al. A large Megaraptoridae (Theropoda: Coelurosauria) from Upper Cretaceous (Maastrichtian) of Patagonia, Argentina. Sci Rep 12, 6318 (2022). https://doi.org/10.1038/s41598-022-09272-z

Novas, F.E., et al., Evolution of the carnivorous dinosaurs during the Cretaceous: The evidence from Patagonia, Cretaceous Research (2013), http://dx.doi.org/10.1016/j.cretres.2013.04.001

Reimagining Amargasaurus

Amargasaurus cazaui. MACN

Dicraeosauridae is a family of mid-sized sauropod dinosaurs characterized by a distinctive vertebral column with paired, long, neural spines. Argentinian dicraeosarids include Amargasaurus cazaui, Pilmatueia faundezi and Bajadasaurus pronuspinax. The group was first described in 1914 by Werner Janensch with the discovery of the nearly complete skeletons of Dicraeosaurus in the expeditions to the upper Jurassic beds of Tendaguru, Tanzania. The discovery of Amargasaurus cazaui in 1991, from the Early Cretaceous beds of La Amarga Formation of Northern Patagonia, renewed the discussion on the peculiar vertebral anatomy of these sauropod dinosaurs.

The hyperelongated hemispinous processes of dicraeosarids were interpreted by some authors as a support structure for a thermoregulatory sail, a padded crest as a display and/or clattering structure, a dorsal hump, or as internal cores of dorsal horn. A new study lead by Ignacio Cerda tested these hypotheses using internal microanatomy and bone microstructure from the holotype of Amargasaurus, and a fragmentary dicreaosaurid specimen (MOZ-Pv 6126-1, consisting of an almost complete anterior dorsal vertebra) also from the La Amarga Formation (Barremian–Aptian, Lower Cretaceous).

Skeletal silhouette of Amargasaurus cazaui. From Cerda et al., 2022.

Despite that the organic components of mineralised tissues decay after death, the inorganic components of bone preserve the spatial orientation of organic components such as osteocyte lacunae, vascular canals, and collagen fibres. Armand de Ricqlès, in the 1960s and 1970s, observed that paleohistological features could be correlated with growth rates and thus could indirectly shed light on the thermal physiology of extinct organisms. Previous paleohistological studies in dicraeosarids revealed particular histological features regarding the vascularization pattern and cortical resorption. 

Bone histology of hyperelongate hemispinous processes of Amargasaurus cazaui. From Cerda et al., 2022

The hemispinous processes from Amargasaurus and MOZ-Pv 6126-1 essentially consist of compact bone tissue. The study lead by Ignacio Cerda also found that secondary remodelling is profuse not only in the perimedullary region but also in the outer cortex. The histological features analized comprise a highly vascularized fibrolamellar bone interrupted with CGMs (cyclical growth marks), presence of obliquely oriented Sharpey’s fibres, and abundant secondary osteons irregularly distributed within the cortex. 

The spatial distribution and orientation of the Sharpey’s fibres indicate the presence of an important system of interspinous ligaments, covered by the integumentary system, which resulted in the formation of a prominent cervical sail in this taxon. However, there is not anatomical or histological evidence that support the presence of a keratinized sheath. The new study also suggests that the cervical sail in Amargasaurus could be used as a display device, a term that includes ‘intraspecific agonistic, deterrent, or sexual display structures’. Unfortunately, the dicraeosaurid record is still too scarce to determine the existence of sexual dimorphism in this clade.

 

References:

Ignacio A. Cerda, Fernando E. Novas, José Luis Carballido, Leonardo Salgado (2022): Osteohistology of the hyperelongate hemispinous processes of Amargasaurus cazaui (Dinosauria: Sauropoda): Implications for soft tissue reconstruction and functional significance. In: Journal of Anatomy. DOI: 10.1111/joa.13659

Windholz, G. J., & Cerda, I. A. (2021). Paleohistology of two dicraeosaurid dinosaurs (Sauropoda; Diplodocoidea) from La Amarga Formation (Barremian–Aptian, Lower Cretaceous), Neuquén Basin, Argentina: Paleobiological implications. Cretaceous Research, 128, 104965. doi: 10.1016/j.cretres.2021.1049

Salgado, L. & Bonaparte, J. F. Un nuevo saurópodo Dicraeosauridae, Amargasaurus cazaui gen et sp. nov., de la Formación La Amarga, Neocomiano de la provincia del Neuquén, Argentina. Ameghiniana 28, 333–346 (1991).

Windholz, G. J., Baiano, M. A., Bellardini, F., & Garrido, A. (2020). New Dicraeosauridae (Sauropoda, Diplodocoidea) remains from the La Amarga Formation (Barremian–Aptian, Lower Cretaceous), Neuquén Basin, Patagonia, Argentina. Cretaceous Research, 104629. doi: 10.1016/j.cretres.2020.10462

 

Introducing Guemesia ochoai

Right lateral view of the braincase of Guemesia ochoai. Scale bar: 5 cm. From Agnolín et al, 2022.

Abelisauroidea is the best known carnivorous dinosaur group from Gondwana. The clade was erected by the legendary paleontologist Jose Bonaparte with the description of Abelisaurus Comahuensis. These theropods exhibit spectacular cranial ornamentation in the form of horns and spikes, and strongly reduced forelimbs. Abelisauroidea has been divided into two main branches: the Noasauridae and the Abelisauridae. The Noasauridae are known from Cretaceous beds in northern Argentina, Madagascar, India, and Niger. They are small and slender with sizes that range from 1 to 3 metres in length. The Abelisaurids are medium to large, robust animals, such as the Carnotaurus and the Majungasaurus of Madagascar. The group exhibits short, round snouts; thickened teeth; short, stocky arms; and highly reduced forearms. The Argentinean record of abelisauroid theropods begins in the Middle Jurassic with Eoabelisaurus mefi, and spans most of the Late Cretaceous. The clade includes Carnotaurus sastrei, Aucasaurus garridoi, Ekrixinatosaurus novasi, Skorpiovenator bustingorryi, Tralkasaurus cuyi, Viavenator exxoni, Niebla antiqua, and Llukalkan aliocranianus. All of them are from the Cretaceous of Patagonia.

Map indicating the locality that yielded Guemesia ochoai. From Agnolín et al, 2022.

Guemesia ochoai is the first definitive abelisaurid theropod from Northwestern Argentina. The holotype (IBIGEO-P 103) is represented by a nearly complete braincase, with parietals, frontals, supraoccipital, basioccipital, exoccipital-opisthotic complex, basisphenoid-parasphenoid, prootics, laterosphenoids, and orbito-sphenoids. It was recovered from Los Blanquitos Formation (Campanian, Late Cretaceous), near Amblayo town, Salta province, Argentina. The name honours General Martin Miguel de Güemes who defended northwestern Argentina during the War of Independence, and Javier Ochoa, technician of the Museo Regional “Florentino Ameghino,” who discovered the specimen. The braincase of Guemesia is small compared to other abelisaurids. Unfortunately, the absence of postcranial elements makes impossible to perform histological analysis and to corroborate if the specimen reached somatic maturity. The cranial endocast has a total length of 73 mm from the base of the olfactory tract to the foramen magnum, and the volume is 47.6 cm3 (almost 70% smaller than the cranial endocasts of Carnotaurus and Viavenator). But the most striking feature of Guemesia is a row of foramina close to the midline of the fused frontals that is unknown in other abelisaurids. These rows may be linked to a zone of thermal exchange.

References:

Federico L. Agnolín et al, First definitive abelisaurid theropod from the Late Cretaceous of Northwestern Argentina, Journal of Vertebrate Paleontology (2022). DOI: 10.1080/02724634.2021.2002348

A new giant titanosaur sauropod from the Upper Cretaceous of Argentina

Image credit: Jose Luis Carballido/CTyS-UNLaM/AFP

Since the discovery of dinosaur remains in the Neuquen basin in 1882, Argentina has gained the title of Land of the Giants. The tittle was reinforced by the discoveries of titanosaurs like Argentinosaurus, Dreadnoughtus, Notocolossus, Puertasaurus, and Patagotitan. The study of this diverse group of sauropod dinosaurs embrace an extensive list of important contributions, which started with Richard Lydekker’s pioneering work on Patagonian dinosaurs. 

Titanosauria is a diverse clade of sauropod dinosaurs represented by nearly 80 genera described worldwide. The group includes the smallest (e.g. Rinconsaurus, and Saltasaurus; with estimated body masses of approximately 6 tonnes) and largest sauropods known to date. The Argentinean record of titanosaurs is particularly abundant with almost 50% of the total world record. For years, Argentinosaurus huinculensis was considered the largest dinosaur that ever walked the Earth. The tittle is now in possession of Patagotitan mayorum, discovered in 2010. The first estimations of Patagotitan body mass suggested that it weigh around 70 tons and reached 40 metres (131 feet) long. But a new study published in 2020 indicates that the body mass of Patagotitan ranges between 42–71 tons, with a mean value of 57 tons.

 

Figure 2. Caudal sequence of MOZ-Pv 1221 and detail of caudal vertebrae 3, 4, 11 and posterior element. From Otero et al., 2021

A new specimen from the Candeleros Formation (98 Ma) of Neuquén Province probably exceeds Patagotitan in size. This new giant titanosaur sauropod was discovered in 2012 and is the second taxon from Candeleros Formation, in addition to Andesaurus. The new specimen, identified as MOZ-Pv 1221, includes a sequence of anterior and middle caudal vertebrae, consisting of the first 20 mostly articulated caudal vertebrae and haemal arches plus isolated posterior caudals, pelvis and other appendicular elements. The preserved caudal sequence corresponds to approximately the anterior half of the tail. The neural spines of the anterior caudal vertebrae in MOZ-Pv 1221 are transversely wider than anteroposteriorly long.

Compared to other giant titanosaurs, the recovered appendicular bones of MOZ-Pv 1221 are larger than any known titanosaur described to date. The maximum dorsoventral height at the proximal section of the scapula is 17% higher than in Patagotitan, 26% higher than in Dreadnoughtus, and 130% higher than in Mendozasaurus. The maximum proximo distal length of the pubis of MOZ-Pv 1221 is 166 cm, which is 10% longer than in Patagotitan, 18% longer than in Dreadnoughtus, and 21% longer than in Futalognkosaurus. Although it is not currently possible to estimate the body mass of MOZ-Pv 1221 because of the fragmentary nature of this specimen, it is clear that this new titanosaur partially recovered from the Candeleros Formation can be considered one of the largest titanosaurs that ever walked the Earth.

 

References:

Otero A, Carballido JL, Salgado L, Canudo JI, Garrido AC (2021), Report of a giant titanosaur sauropod from the Upper Cretaceous of Neuquén Province, Argentina, Cretaceous Research https://doi.org/10.1016/j.cretres.2021.104754

Carballido JL, Pol D, Otero A, Cerda IA, Salgado L, Garrido AC, Ramezani J, Cúneo NR, Krause JM. 2017 A new giant titanosaur sheds light on body mass evolution among sauropod dinosaurs. Proc. R. Soc. B 284: 20171219.
DOI: 10.1098/rspb.2017.1219

Otero, A., J. L. Carballido, A. Pérez Moreno. 2020. The appendicular osteology of Patagotitan mayorum (Dinosauria, Sauropoda). Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2020.1793158

Benson, R. B. J., Campione, N. E., Carrano, M. T., Mannion, P. D., Sullivan, C., Upchurch, P., & Evans, D. C. (2014). Rates of Dinosaur Body Mass Evolution Indicate 170 Million Years of Sustained Ecological Innovation on the Avian Stem Lineage. PLoS Biology, 12(5), http://doi.org/10.1371/journal.pbio.1001853.

Introducing Bagualia alba, the oldest known eusauropod.

Bagualia alba. From Pol et al., 2020

During the Early Jurassic the southwestern margin of Gondwana was affected by a voluminous magmatic episod related to the emplacement of t heKaroo-Ferrar-Chon Aike Large Igneous Provinces (LIPs). That pulse of volcanism led to global warming, with at least four times the present level of atmospheric CO2, and ocean acidification that resulted in a mass extinction of marine invertebrates and turnover among groups of marine plankton. The period is also characterized by a floristic turnover and the diversification of the conifers, especially modern families, with small coriaceous leaves. Biostratigraphic and high-precision geochronologic results indicate that a major faunal turnover of the sauropodomorph dinosaurs took place in the Early Jurassic, which led to the rise of the eusauropods. Cañadón Asfalto Basin (part of the Chon Aike Igneous Province of Patagonia) in the Chubut Province of Argentina preserves an extraordinary record of Jurassic fauna and flora that marks key events in the evolution of Mesozoic life. The recently described Bagualia alba, recovered from the base of the Cañadón Asfalto Formation, lived 179 million years ago and is the oldest known eusauropod. The name of the new specimen refers to Cañadón Bagual, the site where the fossil was found, and alba (dawn, in Spanish), for its early age.

Reconstruction of Bagualia alba. Credit: Jorge Gonzalez

Discovered in 2007 by an international team of researchers led by Argentinean paleontologist Diego Pol, the holotype of Bagualia alba (MPEF PV 3301) consists of a posterior half of a skull found in articulation with seven cervical vertebrae. It was found in close association with multiple cranial and postcranial remains belonging to at least three individuals. Body mass estimated suggests that Bagualia weighted 10 tons, approximately the size of two African elephants. Among the characters that distinguish Bagualia from other early sauropods area pointed process on the anteroventral end of the premaxilla and anterodorsal end of the dentary; orbital margin of the frontal with a close V-shape pointed medially that results in a short contribution to the orbit; supratemporal fenestra about as anteroposteriorly long as lateromedially wide; and strongly marked proatlantal facets on the laterodorsal margin of the foramen magnum. The teeth have a D-shaped cross section, apical denticles, and buccal and lingual grooves. But the most striking feature of Bagualia is the enamel layer which is extremely thick, seven times that of other pre-volcanic herbivores, and is heavily wrinkled on its outer surface.

In Patagonia, prior to the Toarcian palaeoenvironmental crisis the plant assemblage consisted of sphenophytes, dipteridacean ferns, conifers, seed ferns, Bennetitales and cycads. This diversity is indicative of more humid conditions. By contrast, the less diverse palynologycal assemblage postdating the volcanic event is indicative of seasonally dry and warm conditions, and are largely dominated by the conifers Araucariaceae, Cheirolepidiaceae and Cupressaceae. These large conifers with coriaceous leaves as the dominant trees likely acted as a strongly selective regime favouring the survival and success of eusauropods, which had powerful jaws and an oversized gut. Conversely, the disappearance of many elements of the diverse pre-Toarcian flora could have influenced the extinction of the diverse lineages of smaller non-sauropods, which lacked adaptations to high-fibre herbivory as their gracile skulls and mandibles were less mechanically efficient and their teeth were small, with thin enamel (less than 200 μm) and lacked tooth–tooth occlusion.

 

 

References:

Pol D., Ramezani J., Gomez K., Carballido J. L., Carabajal A. Paulina, Rauhut O. W. M., Escapa I. H. and Cúneo N. R., (2020) Extinction of herbivorous dinosaurs linked to Early Jurassic global warming eventProc. R. Soc. B.28720202310 http://doi.org/10.1098/rspb.2020.2310
 
Cúneo, R., Ramezani, J., Scasso, R., Pol, D., Escapa, I., Zavattieri, A. M., & Bowring, S. A. (2013). High-precision U–Pb geochronology and a new chronostratigraphy for the Cañadón Asfalto Basin, Chubut, central Patagonia: Implications for terrestrial faunal and floral evolution in Jurassic. Gondwana Research, 24(3-4), 1267–1275. doi:10.1016/j.gr.2013.01.010 

Meet Niebla antiqua

Silhouette of Niebla antiqua showing the preserved bones in white. Scale bar: 0.5 meters. From Aranciaga et al., 2020.

The Abelisauridae represents the best-known carnivorous dinosaur group from Gondwana. Their fossil remains have been recovered in Argentina, Brazil, Morocco, Niger, Libya, Madagascar, India, and France. The group was erected by Jose Bonaparte with the description of  Abelisaurus Comahuensis. These theropods exhibit spectacular cranial ornamentation in the form of horns and spikes and strongly reduced forelimbs and hands. The Argentinean record of abelisauroid theropods begins in the Middle Jurassic (Eoabelisaurus mefi) and spans most of the Late Cretaceous. The clade includes Carnotaurus sastrei, Abelisaurus comahuensis, Aucasaurus garridoi, Ekrixinatosaurus novasi, Skorpiovenator bustingorryi, Tralkasaurus cuyi and Viavenator exxoni.  Niebla antiqua, a new specimen from the Late Cretaceous of Río Negro province, is an important addition to the knowledge of abelisaurid diversity.

Niebla antiqua is much smaller than other abelisaurids like Carnotaurus and Abelisaurus, with only 4–4.5 metres (13–15 ft) long. It was found near Matadero Hill, located within the Arriagada Farm, at 70 km south from General Roca city, Río Negro province, Argentina. The generic name derived from the Spanish word for “mist”, referring to the foggy days during the excavation of the specimen. The specific name “antiqua”, comes from the Latin “old” and makes reference to the age of the specimen.

 

Digital reconstruction of the braincase of Niebla antiqua in right lateral (A), dorsal (B), and posterior (C) views. From Aranciaga et al., 2020

Digital reconstruction of the braincase of Niebla antiqua in right lateral (A), dorsal (B), and posterior (C) views. From Aranciaga et al., 2020

 

The holotype (MPCN-PV-796) is represented by a nearly complete braincase, incomplete left dentary, isolated teeth, relatively complete scapulocoracoid, dorsal ribs and incomplete vertebrae. The braincase of Niebla is exquisitely preserved, allowing the recognition of most cranial nerves and vascular foramina. The cranial endocast has a total length of 144 mm and has an approximate volume of 64.2 cm3. The scapulocoracoid is notably similar to that of Carnotaurus with a narrow and elongate scapular blade, a glenoid surface posteriorly oriented, and a dorsoventrally expanded and wide coraco-scapular plate. Paleohistological analysis indicates that despite of its relatively small size, the holotypic specimen represents a somatically mature individual.

 

References:

Aranciaga Rolando, M., Cerroni, M. A., Garcia Marsà, J. A., Agnolín, F. l., Motta, M. J., Rozadilla, S., Brisson Eglí, Federico., Novas, F. E. (2020). A new medium-sized abelisaurid (Theropoda, Dinosauria) from the late cretaceous (Maastrichtian) Allen Formation of Northern Patagonia, Argentina. Journal of South American Earth Sciences, 102915. doi:10.1016/j.jsames.2020.102915

A window into Late Triassic biodiversity.

Reconstruction of the paleocommunity of Cerro Las Lajas. Credit: Lucas Fiorelli.

The Ischigualasto Formation, formed along the western margin of Argentina during the breakup of Gondwana, represents one of the most continuous continental Triassic succesions in South America, and it is known worldwide for its tetrapod assemblage, which include the oldest known record of dinosaurs. The most accepted hypothesis gives the name “Ischigualasto” a Quechua origin, meaning “place where the moon sets”. A second hypothesis suggested that the name “Ischigualasto” has Diaguita roots and means “place of death”. Adolf Stelzner in 1889 published the first data on the geology of Ischigualasto, but it was not until 1911, that Bondenbender briefly refers to the fossils of the site. The Ischigualasto Formation consists of four lithostratigraphic members which in ascending order include the La Peña Member, the Cancha de Bochas Member, the Valle de la Luna Member, and the Quebrada de la Sal Member. The northernmost known outcrops of the Ischigualasto formation are exposed at a site know as Hoyada del Cerro Las Lajas, in La Rioja Province, consisting of more than 1,000 m of fluvial-channel and flood overbank deposits with high volcanic input. This site is known as the place where the holotype and only known specimen of Pisanosaurus mertii (PVL 2577) was found.

Ischigualasto Formation in the Hoyada del Cerro Las Lajas locality. From Desojo et al., 2020

In 1962, José F. Bonaparte, Rafael Herbst, Galileo J. Scaglia, and Martín Vince carried out an expedition to the site. Bonaparte’s field notes indicate that they collected rhynchosaur and cynodont material at the site, but never described. In 2013, on the occasion of the XVII Argentine Conference of Vertebrate Paleontology, a group of researchers lead by Julia Desojo, from the National University of La Plata Museum, improvised a brief exploration to the site. Over the course of three more expeditions between 2016 to 2019, the team collected fossils and rocks from various layers of the Las Lajas outcrop, and more than 100 new fossil specimens, including Teyumbaita, a extinct genus of hyperodapedontine rhynchosaur, only previously known in the Late Triassic beds of the Santa Maria Supersequence in southern Brazil.

Teyumbaita. From Desojo et al., 2020

The team analyzed samples of volcanic ash collected from several layers of the Las Lajas outcrops and found that the layers were deposited between 230 million and 221 million years ago. They also found a correlation between the Hyperodapedon and Teyumbaita biozones at the Hoyada del Cerro Las Lajas, respectively, to the lower and upper parts of the Scaphonyx-Exaeretodon-Herrerasaurus biozone in the Hoyada de Ischigualasto and to the upper Hyperodapedon Assemblage Zone of the Santa Maria Supersequence in southern Brazil. Teyumbaita-rich faunas of both Brazil and Argentina persisted into the Norian, before it was eventually replaced by tetrapod assemblages that witnessed the humidity increase of southwestern Pangaean climate.

Reconstructed skeleton reflecting the traditional interpretation of Pisanosaurus (Royal Ontario Museum)

Pisanosaurus mertii was originally described by Argentinian paleontologist Rodolfo Casamiquela in 1967, based on a poorly preserved but articulated skeleton from the upper levels of the Ischigualasto Formation. The holotype and only known specimen (PVL 2577) is a fragmentary skeleton including partial upper and lower jaws, seven articulated dorsal vertebrae, four fragmentary vertebrae of uncertain position in the column, the impression of the central portion of the pelvis and sacrum, an articulated partial hind limb including the right tibia, fibula, proximal tarsals and pedal digits III and IV, the distal ends of the right and left femora, a left scapular blade (currently lost), a probable metacarpal III, and the impressions of some metacarpals (currently lost). The new study constrains the age of Pi. mertii as ca. 229 Ma, showing that this species is latest Carnian. Additonally, certain key anatomical features, like the external mandibular fossa and the anteroposteriorly short cervical vertebrae, indicate that Pisanosaurus is the earliest preserved Ornithiscian specimen.

 

References:

Desojo, J.B., Fiorelli, L.E., Ezcurra, M.D. et al. The Late Triassic Ischigualasto Formation at Cerro Las Lajas (La Rioja, Argentina): fossil tetrapods, high-resolution chronostratigraphy, and faunal correlations. Sci Rep 10, 12782 (2020). https://doi.org/10.1038/s41598-020-67854-1

Federico L. Agnolín & Sebastián Rozadilla (2017): Phylogenetic reassessment of Pisanosaurus mertii Casamiquela, 1967, a basal dinosauriform from the Late Triassic of Argentina, Journal of Systematic Palaeontology DOI: 10.1080/14772019.2017.1352623

Florentino Ameghino, the father of Argentinian paleontology.

Portrait of Florentino Ameghino (1854-1911) by Luis De Servi (1863-1945).

Portrait of Florentino Ameghino (1854-1911) by Luis De Servi (1863-1945).

Florentino Ameghino was born on September 18, 1854. He came from a family of Italian immigrants who settled in 1854 in the town of Lujan, Buenos Aires, Argentina, where the extraction and exportation of fossils were a lucrative activity. The first well known fossil from South America, Megatherium americanum, was recovered by Fray Manuel Torres in this place and later described by George Cuvier in 1796. Fossil collectors and museum commissioners visited the Lujan area pursuing the colossal fossil bones. Darwin himself described the small city in his famous Notebook: “The houses at Luxan are all of one ground-floor, except that of the Cabildo, on the east side of the plaza, which has rooms above. They are all built with sun-burnt bricks, called adobes, not white-washed. The church is a small plain building, with a little turret, and a cupola top.”

Despite being a self-taught naturalist, Ameghino became an international authority in the field of paleontology of vertebrates, geology, and archeology. He was portrayed by his biographers as the incarnation of materialism, leftist culture and national genius. Throughout his scientific career, Ameghino was seconded by his younger brother Carlos Ameghino (1865–1936), who was a “travelling naturalist” for the Museo de La Plata. During his trips, he gathered a remarkable collection of fossil mammals, later described by Florentino.

Ameghino ́s house at Las Heras 466. (ca. 1920). From Ludueña, 2011.

Thanks to the financial support obtained by members of the Genovese community in Argentina, Ameghino traveled to Paris in 1878 and presented his archaeological and paleontological collections at the Paris Anthropological Exhibition. He studied with various French experts, including Paul Gervais and Gabriel de Mortillet, and sold part of his collection to the North American paleontologist Edward Drinker Cope. In 1879, he married Léontine Poirier. She became an important part of Ameghino’s scientific career helping him with his writings, their bookstore, and hosting her husband’s visitors in their home in La Plata. In 1880, Ameghino published La antigüedad del Hombre en el Plata (Man’s Antiquity in the la Plata Basin). He and Léontine stayed in France until 1881.

In 1884, Ameghino published Filogenia, his most important theoretical work which evidenced that Ameghino was a true Darwinist. The book was shaped by Haeckel’s reconstruction of the human ancestral tree, and Gabriel de Mortillet’s ideas. A year later, Ameghino was appointed professor of zoology at Universidad de Córdoba a position that he quit for the vice-directorship of the recently founded Museo de La Plata.

Photo from the Archives of the Museo de La Plata. Although it has no references, it is thought to portray Carlos and Florentino during the latter’s only visit to Patagonia. From Sergio F. Vizcaíno, 2011.

Between the 1880s and 1890s, Ameghino’s descriptions revolutionized scientific opinion regarding primitive mammals. He began corresponding with Hermann von Ihering, a German scientist who had settled in São Paulo, Brazil. They both studied the Tertiary geological formations in South America and elaborated the idea that all mammals had originated in Patagonia and then moved to Africa through the continental bridges connecting the ancient continents. This partnership was internationally known as Ameghino, von Ihering & Co. At the time, Ameghino had alredy published his monograph Contribución al conocimiento de los mamíferos fósiles de la República Argentina. The work was praised by Karl von Zittel in his History of Geology and Paleontology of 1899, who remarked that “the most important paleontological event of the last two decades of the nineteenth century has been the disclosure made by Florentino Ameghino of a rich Mammalian fauna in the Tertiary rocks of Patagonia.”

In 1887, Ameghino described a large, toothless jaw from the Miocene of the Province of Santa Cruz, naming it Phorusrhacos longissimus and assigning it to a new family of edentulous mammals. He used this finding as a critical evidence for his contention that modern mammalian lineages originated in Argentina and later spread across the globe. At that time, Ameghino and Francisco P. Moreno, Director of the Museo de la Plata, were in the middle of a bitter dispute. The feud between the two men was in many aspects similar to the well-known feud between E.D. Cope and O.C. Marsh, which took place in the United States at roughly the same time. Four years later, Moreno and Alcides Mercerat recognized for the first time that the mandible described by Ameghino was really that of a bird.

Images of the type specimen of the Santacrucian sloth
Proschismotherium oppositum Ameghino, 1902. From Vizcaino et al., 2017-

Ameghino resigned from his position at the Museo de La Plata in 1888, and Moreno denied him access to the paleontological collection. From that moment, and until became head of the Museo Argentino de Ciencias Naturales in Buenos Aires in 1902, the Ameghino brothers continued with their palaeontological exploration, without any permanent official support, but they managed to get the funds to run their paleontological investigations as a private enterprise. Karl von Zittel, subsidized their explorations, receiving in exchange fossils for the collection of the Munich University. Meanwhile Moreno, in order to gain priority over his rivals, published a series of brief reports about the new palaeontological discoveries made by his field researchers.

In 1895, the critical financial situation forced Florentino Ameghino to sell his fossil bird collection, in order to support his further work in Patagonia. The collection was purchased by the London Museum by the sum of 350 £ in 1896. When Florentino became director of the Museo Nacional de Buenos Aires in 1902 the selling of fossils ceased, and he started making claims for the return of the museum’s collections. He also proposed for the most remarkable specimens of Patagonian and Pampean fossil faunas to be cast and stored in Buenos Aires and La Plata museums to be used in Argentinean schools. The same casts were sent to Museums all over the world and in exchange, Ameghino received casts of the oldest fossil mammals from Africa and the Northern Hemisphere to compare with the Patagonian faunas. It was a clever way to prevent the sale of the original fossils.

Florentino Ameghino in his archaeological deposit, 1902. Archivo General de la Nación Argentina. Inventario 4738.

Florencio Ameghino died on August 6, 1911. After his death, he became a national icon for his role in creating national science and culture. The Ameghino collection is still today the reference collection of the entire Cenozoic Era biostratigraphic system for the South American continent. The Florentino Ameghino Partido, situated in the north-west of Buenos Aires Province, was named after him, as well as various educational institutions across the country, libraries and museums, squares, schools, parks and other locations. The Ameghino Crater, located to the north of the Sinus Successus on the Moon, is also named in his honor. A very rare privilege for a paleontologist.

References:

Ameghino, F. 1889. Contribución al conocimiento de los mamíferos fósiles de la República Argentina. Actas de la Academia Nacional de Ciencias en Córdoba 6: 1-1028.

Podgorny, I. (2016). The Daily Press Fashions a Heroic Intellectual: The Making of Florentino Ameghino in Late Nineteenth-Century Argentina. Centaurus, 58(3), 166–184. doi:10.1111/1600-0498.12125

Ludueña, E. 2011. La Casa era de los Ameghino. Monumento Histórico Nacional. La Graphica, Luján, 176 pp.

Sergio F. Vizcaíno, Gerardo De Iuliis, Paul D. Brinkman, Richard F. Kay, and Daniel L. Brinkman (2017). On an album of photographs recording fossils in the “Old collections” of the Museo de la Plata and Ameghino’s private collection at the beginning of the XXTH century. Publicación Electrónica de la Asociación Paleontológica Argentina 17 (1): 14–23.
Vizcaíno, Sergio Fabián; Cartas para Florentino desde la Patagonia: Crónica de la correspondencia édita entre los hermanos Ameghino (1887-1902); Asociación Paleontológica Argentina; Publicación Especial – Asociación Paleontológica Argentina; 12; 1; 12-2011; 51-67 http://hdl.handle.net/11336/80957

A Short History of the Early Female Geoscientists from Argentina

Mathilde Dolgopol de Saez. Image credit: Asociación Paleontológica Argentina (A.P.A.)

Women have played various and extensive roles in the history of geology. Unfortunately, their contribution has not been widely recognised by the public or academic researchers. In the 18th and 19th centuries women’s access to science was limited, and science was usually a ‘hobby’ for intelligent wealthy women. Early female scientists were often born into influential families, like Grace Milne, the eldest child of Louis Falconer and sister of the eminent botanist and palaeontologist, Hugh Falconer; or Mary Lyell, the daughter of the geologist Leonard Horner. They collected fossils and mineral specimens, and were allowed to attend scientific lectures, but they were barred from membership in scientific societies. Thanks to the pioneer work of these women, the 20th century saw the slow but firm advance of women from the periphery of science towards the center of it.

Edelmira Inés Mórtola (1894-1973)

In Argentina, during the 1870s, public schools were organized and expanded for the training of teachers in different cities of the country. North American teachers were hired, some of whom promoted among their students the interest in pursuing university studies. Cecilia Grierson (1859-1934) was the first woman to earn a PhD in Medicine and Surgery in 1889. She was an important reference for other women, collaborating in the women’s movement in the early twentieth century.

The first papers in natural sciences signed by women were published around 1910. Edelmira Inés Mórtola was the first woman to earn her Ph. D in geology in Argentina, in 1921. She was also the first woman to work for the Dirección General de Minas, Geología, e Hidrología (DGMGH) in 1919. She focus on teaching and was an inspiring figure for young women. In 1924, she was appointed Professor at the Universidad de Buenos Aires (UBA). The Museum of Mineralogy “Dr. E. Mórtola “, that she helped to organize, honors her extraordinary career. She died on May 28, 1973.

Noemí Violeta Cattoi. Image credit: Asociación Paleontológica Argentina (A.P.A.)

Mathilde Dolgopol de Saez was born on March 6, 1901. She was one of the first female paleontologist from Argentina (graduated in 1927), along with Ana Cortelezzi (1928?), Dolores López Aranguren (1930), Andreína Bocchino de Ringuelet (1930?) y Enriqueta Vinacci Thul (1930). Unfortunately, only her thesis and the one of López Aranguren were formally published. The mayor part of her research was focused on fossil fish and birds. She died on June 27, 1957.

Noemí Violeta Cattoi was born in Buenos Aires on December 23, 1911. She received her PhD degree in Natural Science at the University of Buenos Aires, but before her graduation she was trained at the Museo Argentino de Ciencias Naturales. She was head of Paleozoology at the Museum, and adjunt professor at the Museo de la Plata. Her research was mainly focused on extinct birds and mammals from South America. She was also one of the founding member of the Asociación Paleontológica Argentina (A.P.A), along with María Bonetti de Stipanicic, Andreína B. de Ringuelet, Elsa F. de Alvarez and Hildebranda A. Castellaro. Noemí Cattoi died on January 29, 1965.

Reference:.

Rafael Herbst, Luisa M. Anzótegui, Las mujeres en la paleontología argentina, Revista del Museo de La Plata (2016) Volumen 1, Número Especial: 130-13 DOI:https://doi.org/10.24215/25456377e024

GARCIA, Susana V.. Ni solas ni resignadas: la participación femenina en las actividades científico-académicas de la Argentina en los inicios del siglo XX. Cad. Pagu [online]. 2006, n.27, pp.133-172 https://doi.org/10.1590/S0104-83332006000200007.

Link: https://www.apaleontologica.org.ar/

Introducing Tralkasaurus cuyi, the thunder lizard.

Photo: AFP/MUSEO ARGENTINO DE CIENCIAS NATURALES

The Abelisauridae represents the best-known carnivorous dinosaur group from Gondwana. Their fossil remains have been recovered in Argentina, Brazil, Morocco, Niger, Libya, Madagascar, India, and France. The group was erected by the legendary paleontologist Jose Bonaparte with the description of  Abelisaurus Comahuensis. These theropods exhibit spectacular cranial ornamentation in the form of horns and spikes and strongly reduced forelimbs and hands. The clade includes Carnotaurus sastrei, Abelisaurus comahuensis, Aucasaurus garridoi, Ekrixinatosaurus novasi, Skorpiovenator bustingorryi, Eoabelisaurus mefi and Viavenator exxoni.

Abelisauroids were traditionally divided into two main clades: large-sized Abelisauridae, and small-sized Noasauridae. Although represented by relatively well-known skeletons, the phylogenetic relationships within abelisaurids remain debated. The Argentinean record of abelisauroid theropods begins in the Middle Jurassic (Eoabelisaurus mefi) and spans most of the Late Cretaceous. Now, a new abelisaurid from the upper section of the Huincul Formation (Cenomanian-Turonian) at the Violante Farm fossil site, Río Negro province, northern Patagonia, Argentina, is an important addition to the knowledge of abelisaurid diversity.

Map of El Cuy region showing the Violante farm fossil site. From Cerroni et al., 2020.

The holotype MPCA-Pv 815 is represented by an incomplete specimen including a right maxilla, distorted and incomplete dorsal, sacral and caudal vertebrae, cervical ribs, and pubis. Tralkasaurus is a medium-sized abelisaurid, much smaller than large abelisaurids as Abelisaurus and Carnotaurus. The name derived from Tralka, thunder in Mapudungun language, and saurus, lizard in Ancient Greek. The specific name “cuyi” derived from the El Cuy, the geographical area at Rio Negro province, Argentina, where the fossil was found.

This four-meter-long (13-foot-long) theropod exhibits a unique combination of traits, including deeply incised and curved neurovascular grooves at the lateral maxillary body that originate at the ventral margin of the antorbital fossa, and shows an extensive antorbital fossa over the maxillary body that is ventrally delimited by a well-marked longitudinal ridge that runs from the promaxillary fenestra level towards the rear of the maxilla.
Because body mass is usually indicative of an ecological niche, the new taxon probably occupied a different ecological niche within the predatory guild.

 

References:

Cerroni, M.A., Motta, M.J., Agnolín, F.L., Aranciaga Rolando, A.M., Brissón Egli, F., & Novas, F.E. (2019). A new abelisaurid from the Huincul Formation (Cenomanian-Turonian; Upper Cretaceous) of Río Negro province, Argentina. Journal of South American Earth Sciences https://www.sciencedirect.com/science/article/abs/pii/S0895981119304766