[Paleontology • 2024] Parvosuchus aurelioi • A New small-sized predatory pseudosuchian Archosaur (Pseudosuchia: Gracilisuchidae) from the Middle-Late Triassic of Southern Brazil

 Parvosuchus aurelioi  

Müller, 2024 

   

DOI: 10.1038/s41598-024-63313-3

 Artwork by Matheus Fernandes.

Abstract

Before the rise of dinosaurs and pterosaurs, pseudosuchians—reptiles from the crocodilian lineage—dominated the Triassic land ecosystems. This lineage diversified into several less inclusive clades, resulting in a wide ecomorphological diversity during the Middle and Late Triassic. Some giant pseudosuchians occupied the top of the trophic webs, while others developed extensive bony armor as a defense mechanism, which later evolved as a convergence in the avemetatarsalian lineage. On the other hand, there were groups like the Gracilisuchidae, which was composed of carnivorous forms with lightweight build and less than 1 m in length. The fossil record of gracilisuchids is geographically restricted to China and Argentina, with one ambiguous record from Brazil. In the present study, the first unambiguous gracilisuchid from Brazil is described. Parvosuchus aurelioi gen. et sp. nov. comes from the Dinodontosaurus Assemblage Zone of the Santa Maria Formation, which is associated with the Ladinian-Carnian boundary. Composed of a complete cranium, vertebrae, pelvic girdle and hindlimbs, the new species nests with Gracilisuchus stipanicicorum and Maehary bonapartei in a phylogenetic analysis. Its discovery fills a taxonomic gap in Brazilian pseudosuchian fauna and reveals the smallest known member of this clade from the Dinodontosaurus Assemblage Zone, highlighting the diversity of pseudosuchians during the moment that preceded the dawn of dinosaurs.

 

Skull and lower jaws of Parvosuchus aurelioi gen. et sp. nov.
Holotype (CAPPA/UFSM 0412)
 from the Pinheiros-Chiniquá Sequence (Ladinian-Carnian boundary) of the Santa Maria Supersequence, southern Brazil. 

Provenance of Parvosuchus aurelioi gen. et sp. nov. 
(a) Location and geological context of the Linha Várzea 2 site, Paraíso do Sul, Rio Grande do Sul, Brazil. (b) General view of the Linha Várzea 2 site (taken in January 2023).
(c) Hypothetical reconstruction of the skeleton of the Parvosuchus aurelioi gen. et sp. nov. depicting (in orange) the preserved portions of CAPPA/UFSM 0412. Unpreserved portions are based on the skeletal reconstruction of Gracilisuchus stipanicicorum by Jorge González.

Systematic paleontology

Archosauria Cope, 1869

Pseudosuchia Zittel, 1887–1890

Gracilisuchidae Butler et al., 2014

Parvosuchus aurelioi gen. et sp. nov. 

Holotype: CAPPA/UFSM 0412, a partial skeleton, including a skull with lower jaws, 11 dorsal vertebrae, two sacral vertebrae, a complete pelvic girdle, both femora (lacking the distal portion), partial left tibia, partial left fibula, and left calcaneum.

Etymology: The genus name combines the Latin word “parvus” (= small) and the Greek word “suchus” (= crocodile). The specific epithet honors Pedro Lucas Porcela Aurélio for his passion for paleontology and prospecting, as well as for having discovered the fossil material described here.

Results of the phylogenetic analysis and diversity of the Dinodontosaurus Assemblage Zone of Brazil. (a) Time-calibrated reduced strict consensus tree depicting the phylogenetic position of Parvosuchus aurelioi gen. et sp. nov. Number on nodes represent Bremer support values higher than 1. The temporal bars for each OTU represent the maximum and minimum ages of each geological unit. Divergence times set as approximately 1 million years. (b) Percentage of taxonomic groups recorded in the Dinodontosaurus Assemblage Zone according to the number of species. (c) Approximate body length of pseudosuchian species from the Dinodontosaurus ZA.

Artistic representation of a Middle-Late Triassic landscape of southern Brazil.
(a) A large Prestosuchus chiniquensis feeds on the carcass of a dicynodont while individuals of Parvosuchus aurelioi gen. et sp. nov. compete for scraps. (b) and (c) depict details of individuals of Parvosuchus aurelioi gen. et sp. nov. Artwork by Matheus Fernandes.

Rodrigo T. Müller. 2024. A New small-sized predatory pseudosuchian Archosaur from the Middle-Late Triassic of Southern Brazil. Scientific Reports. 14, 12706. DOI: 10.1038/s41598-024-63313-3

[Paleontology • 2023] Amanasaurus nesbitti • A New silesaurid (Archosauria: Silesauridae) from Carnian Beds of Brazil fills A Gap in the Radiation of Avian line Archosaurs

Amanasaurus nesbitti 

 Müller & Garcia, 2023

 DOI: 10.1038/s41598-023-32057-x 

 Researchgate.net/publication/369946312

Abstract

Comprising the oldest unequivocal dinosauromorphs in the fossil record, silesaurs play an important role in the Triassic radiation of dinosaurs. These reptiles provide the main source of information regarding the ancestral body plan of dinosaurs, as well as the basis for biogeographic models. Nevertheless, the co-occurrence of silesaurs and the oldest unequivocal dinosaurs is rare, which hampers reliable ecological inferences. Here we present the first species of silesaur from the oldest unequivocal dinosaur-bearing beds from Brazil. Amanasaurus nesbitti gen. et sp. nov. possesses a unique set of femoral traits among silesaurs, including the oldest occurrence of an anterior trochanter separated by the femoral shaft by a marked cleft. Its femoral length indicates that the new species rivals in size with most coeval dinosaurs. This find challenges the assumption that in faunas where silesaurs and unambiguous dinosaurs co-occurred, silesaurs were relatively smaller. Moreover, the presence of dinosaur-sized silesaurs within ecosystems with lagerpetids, sauropodomorphs and herrerasaurids reinforces the complex scenario regarding the early radiation of Pan-Aves. Silesaurs—independent of their phylogenetic position—persisted during most of the Triassic Period, with its plesiomorphic body size advancing through the dawn of dinosaurs, instead of silesaur lineages decrease in body size through time.

Systematic paleontology

Archosauria Cope, 1869

Pan-Aves Gauthier & de Queiroz, 2001

Dinosauromorpha Benton, 1985

Silesauridae Nesbitt et al., 2010

Amanasaurus nesbitti gen. et sp. nov. 

Diagnosis: Amanasaurus nesbitti differs from all other known silesaurs with comparable material in (*local autapomorphies): posteromedial tuber of the femoral head reduced to absent; ventral margin of the anteromedial tuber exceeding the femoral head margin; presence of a fossa trochanterica; absence of a raised anterolateral scar; presence of a semi-circular scar on the posterodorsal surface of the femoral head*; cleft between the proximal tip of the anterior trochanter and the femoral shaft ...

Etymology: The genus combines the Tupi word “amana” (= rain) and the Greek “saurus” (= lizard), referring to the Carnian pluvial episode. The specific epithet honors Dr. Sterling J. Nesbitt, a prominent North American paleontologist, for his contribution and studies on silesaurs and Triassic archosaurs.

Rodrigo T. Müller and Maurício S. Garcia. 2023. A New silesaurid from Carnian Beds of Brazil fills A Gap in the Radiation of Avian line Archosaurs. Scientific Reports.  13: 4981. DOI: 10.1038/s41598-023-32057-x

  Researchgate.net/publication/369946312_A_new_silesaurid_from_Carnian_beds_of_Brazil

 www.ufsm.br/2023/04/14/paleontologos-descobrem-nova-especie-pre-historica 

[Paleontology • 2021] New Specimens provide insights into the Anatomy of the Dinosauriform Lewisuchus admixtus Romer, 1972 from the upper Triassic Levels of the Chañares Formation, NW Argentina

Lewisuchus admixtus Romer, 1972

in  Agnolín, Egli, ... et Novas, 2021.

DOI: 10.1002/ar.24731 

  facebook.com/LACEVmacn 

 Abstract

Lewisuchus admixtus is an early dinosauriform described by Alfred Romer in 1972 on the basis of a single, incomplete skeleton, collected in lower Upper Triassic rocks of the renowned Chañares Formation, at the Los Chañares type-locality, La Rioja Province, north-western Argentina. Recent field explorations to the type-locality resulted in the discovery of two partial articulated skeletons, which provide significant novel information. The cranial bones, presacral series, femur, tibia, and proximal tarsals of the new specimens match the preserved overlapping anatomy of the holotype and previously referred specimens of L. admixtus, including the presence of unique combination of character states among dinosauriforms (anterior presacral column with additional ossification on the top of neural spines, dorsal neural spines fan-shaped, anterior surface of the astragalus with a dorsally curved groove, and an inflated area on the anterior portion of the medial surface of this bone). This new information improves our understanding of the anatomy and taxonomy of early dinosauriforms and reinforces the role of Argentinean beds on the study of the origin of dinosaurs.

Keywords: Archosauria, Dinosauriformes, Late Triassic, Lewisuchus admixtus, South America

Lewisuchus admixtus.
preserved bones of PULR V-111. Scale bar: 2 cm.  

Posterior cervical and anterior dorsal vertebrae of Lewisuchus admixtus (PULR V-111)

CONCLUSIONS: 

New specimens reported here add valuable information on the anatomy of Lewisuchus admixtus. Outstanding novel features described here for this taxon include an iliac portion of the acetabulum that is medially closed, elongated ischium and pubis (representing at least 2/3 of the femoral length), fan-shaped dorsal neural spines with a spine tables, and gastralia well separated from one another. Besides, the cranial bones, presacral series, femur, tibia, and proximal tarsals of the new specimens match the preserved overlapping anatomy of the holotype of L. admixtus and some of the specimens previously referred to “Pseudolagosuchus major” (e.g., MACN-Pv 18954), including the presence of unique combination of character states among dinosauriforms. This provides stronger evidence for the association of specimens that currently form the hypodigm of L. admixtus. An improved understanding of the anatomy and taxonomy of the Chañares Formation dinosauriforms is crucial to shed new lights on the phylogenetic relationships among nondinosaurian dinosauriforms and the dawn of dinosaur evolution.

Federico Agnolín, Federico Brissón Egli, Martín D. Ezcurra, Max C. Langer and Fernando Novas. 2021. New Specimens provide insights into the Anatomy of the Dinosauriform Lewisuchus admixtus Romer, 1972 from the upper Triassic levels of the Chañares Formation, NW Argentina. The Anatomical Record. DOI: 10.1002/ar.24731

   facebook.com/LACEVmacn/posts/239708901497849

[Paleontology • 2020] Lewisuchus admixtus • New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina

Lewisuchus admixtus Romer, 1972

in Ezcurra, Nesbitt, Fiorelli & Desojo, 2020.

DOI: 10.1002/ar.24243 

  Researchgate.net/publication/335384605 

ABSTRACT

The lower Carnian levels of the Chañares Formation (Ischigualasto-Villa Unión Basin, La Rioja Province) have yielded some of the most informative dinosaur precursor species known so far. However, these species are based on partial skeletons that in several cases hamper the comparison between them because of the absence of overlapping bones. This has generated a contentious debate during the last 20 years about the synonymy between two of these species, Lewisuchus admixtus and Pseudolagosuchus major. Here, we describe a new dinosauriform partial skeleton (CRILAR-Pv 552) recently collected in the Chañares Formation that preserves previously unknown anatomical regions for the dinosaur precursors of this unit (e.g., premaxilla, inner ear, anterior zeugopodium) and allows comparisons with other dinosauriform specimens. CRILAR-Pv 552 is referred to Lewisuchus admixtus because it possesses a proportionally large skull, a laterally projected, shelf-like ridge on the jugal, and recurved, finely serrated middle–posterior maxillary and dentary teeth ankylosed to the bone, and the absence of a coracoid foramen. The new specimen preserves a dorsally bowed dentary with a lateroventral shelf that is identical to a dentary associated with the holotype of Lewisuchus admixtus. Additionally, the morphology of the new specimen is completely congruent with that of specimens of Pseudolagosuchus major, bolstering the hypothesis that the latter species is a subjective junior synonym of Lewisuchus admixtus. A preliminary phylogenetic analysis with updated scorings for Lewisuchus admixtus found this species at the base of Silesauridae. 

 

Keywords: Lewisuchus admixtus, Pseudolagosuchus major, Archosauria, Dinosauriformes, Ischigualasto-Villa Unión Basin, Late Triassic, South America

Fig. 3. Skeleton of Lewisuchus admixtus.
(A) Preserved bones of CRILAR-Pv 552 in approximate anatomical arrangement.
(B) Skeletal reconstruction of Lewisuchus admixtus based on the holotype and referred specimens (see Discussion). 

Scale bar equals 10 cm in B. Skeletal reconstruction drawn by Lucas E. Fiorelli.

 

Martín D. Ezcurra, Sterling J. Nesbitt, Lucas E. Fiorelli and Julia B. Desojo. 2020. New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina. The Anatomical Record. 303; 1393–1438. DOI: 10.1002/ar.24243 

  Researchgate.net/publication/335384605_Anatomy_and_Taxonomy_of_the_Early_Late_Triassic_Dinosauriforms

[Paleontology • 2020] A Paraphyletic ‘Silesauridae' as An Alternative Hypothesis for the Initial Radiation of Ornithischian Dinosaurs

in Müller & Garcia, 2020.

DOI: 10.1098/rsbl.2020.0417

 facebook.com/CAPPAUFSM 

Abstract

Whereas ornithischian dinosaurs are well known from Jurassic and Cretaceous deposits, deciphering the origin and early evolution of the group remains one of the hardest challenges for palaeontologists. So far, there are no unequivocal records of ornithischians from Triassic beds. Here, we present an alternative evolutionary hypothesis that suggests consideration of traditional ‘silesaurids' as a group of low-diversity clades representing a stem group leading to core ornithischians (i.e. unambiguous ornithischians, such as Heterodontosaurus tucki). This is particularly interesting because it fills most of the ghost lineages that emerge from the Triassic. Following the present hypothesis, the lineage that encompasses the Jurassic ornithischians evolved from ‘silesaurids' during the Middle to early Late Triassic, while typical ‘silesaurids' shared the land ecosystems with their relatives until the Late Triassic, when the group completely vanished. Therefore, Ornithischia changes from an obscure to a well-documented clade in the Triassic and is represented by records from Gondwana and Laurasia. Furthermore, according to the present hypothesis, Ornithischia was the first group of dinosaurs to adopt an omnivorous/herbivorous diet. However, this behaviour was achieved as a secondary step instead of an ancestral condition for ornithischians, as the earliest member of the clade is a faunivorous taxon. This pattern was subsequently followed by sauropodomorph dinosaurs. Indeed, the present scenario favours the independent acquisition of an herbivorous diet for ornithischians and sauropodomorphs during the Triassic, whereas the previous hypotheses suggested the independent acquisition for sauropodomorphs, ornithischians, and ‘silesaurids'.

Keywords: evolution, Dinosauria, Mesozoic era, phylogenetics, feeding behaviours, Dinosauromorpha 

Rodrigo Temp Müller and Maurício Silva Garcia. 2020. A Paraphyletic ‘Silesauridae' as An Alternative Hypothesis for the Initial Radiation of Ornithischian Dinosaurs. Biology Letters. 16:20200417. DOI: 10.1098/rsbl.2020.0417

 facebook.com/CAPPAUFSM/photos/3290688631026919/

Sacisaurus helps to fill the hole in the evolution of ornithischians

 phys.org/news/2020-08-sacisaurus-hole-evolution-ornithischians.html

[Paleontology • 2020] Erythrovenator jacuiensis • A New Theropod Dinosaur from A Peculiar Late Triassic Assemblage of southern Brazil

Erythrovenator jacuiensis 

Müller, 2020

DOI: 10.1016/j.jsames.2020.103026

Illustration: Márcio L. Castro.

 twitter.com/MarcioLCastro 

Highlights: 

• A new theropod dinosaur from the Late Triassic of Brazil is described.

• It is one of the oldest known theropods worldwide.

• This sheds light on some of the earliest theropod features.

• The new theropod comes from a peculiar fauna dominated by traversodontid cynodonts.

• The new theropod represents the first carnivorous dinosaur from this assemblage.

Abstract

The early evolution of theropod dinosaurs is poorly understood. Whereas sauropodomorphs are well-known from the oldest dinosaur bearing outcrops, the record of theropods is fragmentary and ambiguous. The Triassic deposits from Brazil yielded some of the oldest dinosaurs worldwide. These dinosaurs came from two distinct Assemblage Zones (AZ): the Hyperodapedon AZ (Carnian) and the Riograndia AZ (early Norian). Here, a specimen previously assigned to cf. Dinosauromorpha is reassessed. CAPPA/UFSM 0157 comes from an enigmatic assemblage with predominance of the traversodotind cynodont Siriusgnathus. This assemblage has been tentatively assigned to the Riograndia AZ. However, the absence of index fossils still hampers a reliable assignation. The specimen, which comprises a proximal portion of a left femur, belongs to a new theropod taxon erected here as Erythrovenator jacuiensis gen. et sp. nov. The new dinosaur differs from all other known Triassic dinosaurs based on the absence of a raised dorsolateral trochanter of the femur. Erythrovenator jacuiensis gen. et sp. nov. is regarded as a theropod on the basis of the pyramidal shape of the anterior trochanter in anterior view. The results of a phylogenetic analysis corroborate this assignation. Therefore, the new dinosaur represents one of the oldest theropod dinosaurs worldwide, shedding lights on some of the earliest theropod features. Finally, the new specimen also represents the first carnivorous dinosaur from the assemblage dominated by the traversodontid cynodont Siriusgnathus, increasing our knowledge of the faunal content of this enigmatic assemblage.

Keywords: Archosauria, Candelária sequence, Carnian, Dinosauromorpha, Norian, Theropoda, Saurischia, South America

 Photographs, 3D scans, and line drawings of Erythrovenator jacuiensis gen. et sp. nov. (CAPPA/UFSM 0157), from the Niemeyer Site, Agudo, Rio Grande do Sul, Brazil; Carnian–early Norian, Late Triassic.
 Proximal portion of the left femur in (A) anterior, (B) lateral, (C) proximal, (D) medial, and (E) posterior views.

Abbreviations: alt, anterolateral tuber; amt, anteromedial tuber; ar, anterior ridge; as, anterior scar; at, anterior trochanter; ce, concave emargination; faa, facies articularis antitrochanterica; gt, greater trochanter; pmt, posteromedial tuber; ps, posterior scar; s, scar; slcf, sulcus for ligamentum capitis femoris.

 CoelhopreCambriano.blogspot.com

 Systematic Paleontology 

Dinosauriformes Novas, 1992 

Dinosauria Owen, 1842 

Theropoda Marsh, 1881 

Erythrovenator gen. nov. 

 Etymology. ‘Erythro’ comes from the Greek erythrós, meaning “red” or “reddish”, referring to the red color of the holotype fossil; ‘venator’ is the Latin word for hunter. 

Erythrovenator jacuiensis sp. nov. 

 Etymology. The species name ‘jacuiensis’ is in reference to ‘Rio Jacuí’, a river that runs in Agudo. 

 Rodrigo T. Müller. 2020. A New Theropod Dinosaur from A Peculiar Late Triassic Assemblage of southern Brazil. Journal of South American Earth Sciences. In Press. DOI: 10.1016/j.jsames.2020.103026

  twitter.com/MarcioLCastro/status/1333430627199291392

   CoelhopreCambriano.blogspot.com/2020/11/paleontologo-identifica-possivel.html

    

    

 

[Paleontology • 2019] Nhandumirim waldsangae • A New Dinosaur with Theropod Affinities from the Late Triassic Santa Maria Formation, South Brazil

Nhandumirim waldsangae 

Marsola, Bittencourt, Butler, Da Rosa, Sayão & Langer, 2019

  DOI: 10.1080/02724634.2018.1531878 

 jornal.usp.br/ciencias

ABSTRACT

The Late Triassic (Carnian) upper Santa Maria Formation of south Brazil has yielded some of the oldest unequivocal records of dinosaurs. Here, we describe a new saurischian dinosaur from this formation, Nhandumirim waldsangae, gen. et sp. nov., based on a semiarticulated skeleton, including trunk, sacral, and caudal vertebrae, one chevron, right ilium, femur, partial tibia, fibula, and metatarsals II and IV, as well as ungual and non-ungual phalanges. The new taxon differs from all other Carnian dinosauromorphs through a unique combination of characters, some of which are autapomorphic: caudal centra with sharp longitudinal ventral keels; brevis fossa extending for less than three-quarters of the ventral surface of the postacetabular ala of the ilium; dorsolateral trochanter ending well distal to the level of the femoral head; distal part of the tibia with a mediolaterally extending tuberosity on its cranial surface and a tabular caudolateral flange; conspicuous, craniomedially oriented semicircular articular facet on the distal fibula; and a straight metatarsal IV. This clearly distinguishes Nhandumirim waldsangae from both Saturnalia tupiniquim and Staurikosaurus pricei, which were collected nearby and at a similar stratigraphic level. Despite not being fully grown, the differences between Nhandumirim waldsangae and those saurischians cannot be attributed to ontogeny. The phylogenetic position of Nhandumirim waldsangae suggests that it represents one of the earliest members of Theropoda. Nhandumirim waldsangae shows that some typical theropod characters were already present early in dinosaur evolution, and it represents possibly the oldest record of the group known in Brazil.

  Silhouette depicting the preserved bones of Nhandumirim waldsangae, gen. et sp. nov. (LPRP/USP 0651).

SYSTEMATIC PALEONTOLOGY 

DINOSAURIFORMES Novas, 1992, sensu Nesbitt, 2011 

DINOSAURIA Owen, 1842, sensu Padian and May, 1993 

SAURISCHIA Seeley, 1887, sensu Gauthier, 1986 

cf. THEROPODA Marsh, 1881, sensu Gauthier, 1986 

NHANDUMIRIM WALDSANGAE, gen. et sp. nov

Etymology— The generic name combines the Portuguese derivatives of the indigenous Tupi-Guarani words ‘Nhandu’ (running bird, common rhea) and ‘Mirim’ (small), in reference to the size and inferred cursorial habits of the new dinosaur. The specific epithet name refers to the Waldsanga site, the historic outcrop (Langer, 2005a) that yielded this new species.

Júlio C. A. Marsola, Jonathas S. Bittencourt, Richard J. Butler, Átila A. S. Da Rosa, Juliana M. Sayão and Max C. Langer. 2019. A New Dinosaur with Theropod Affinities from the Late Triassic Santa Maria Formation, South Brazil. Journal of Vertebrate Paleontology. e1531878 DOI: 10.1080/02724634.2018.1531878   

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