Tetrapod burrows from the Middle–Upper Triassic Chañares Formation (La Rioja, Argentina) and its palaeoecological implications

Fiorelli, Lucas E.; Rocher, Sebastián; Martinelli, Agustín G.; Ezcurra, Martín D.; Hechenleitner, E. Martín; Ezpeleta, Miguel

doi:10.1016/j.palaeo.2018.01.026

Cited by 27 publications

(25 citation statements)

References 63 publications

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“…The Massetognathus – Chanaresuchus Assemblage Zone ( M‐Ch AZ), and the CRILAR‐Pv 552‐bearing level in particular, corresponds to volcaniclastic deposits emplaced in alluvial and lacustrine settings. Huge volumes of these sediments were transported downslope during the syneruptive periods of the basin (Fiorelli et al ., ). These geological and palaeoenvironmental features strongly signed the pattern of preservation and taphonomic attributes observed in the CRILAR‐Pv 552‐bearing level and contiguous fossiliferous levels.…”

Section: Discussionmentioning

confidence: 97%

“…In sum, the sediments of the Chañares Formation were deposited in a fluvial‐alluvial to lacustrine setting affected by volcanism within an active rift basin (López Gamundí et al ., ; Rogers et al ., ). A wax‐wane volcanic cycle through the entire Chañares Formation has been recognized (Fiorelli et al ., ). Sedimentation started, – Tarjadia AZ– with flood‐deposited volcaniclasts distributed in shallow braided channels that aggraded and progressively filled the palaeotopography of the Tarjados Formation.…”

Section: Introductionmentioning

confidence: 97%

“…The volcanic activity increased subsequently – M‐Ch AZ–, large volumes of volcaniclastic sediments were available and redistributed by high‐discharge, sediment‐laden flows originated during or following eruptions. Vast volumes of sediments were transported downslope by mass‐flow and high‐sediment‐concentration flow processes (Lahar‐type flood events) during the syneruptive periods of the basin (Fiorelli et al ., ; Perez Loinaze et al ., ). The widespread syneruption aggradation resulted in a broad alluvial‐plain or volcaniclastic apron that characterized the M‐Ch AZ of the Chañares region 236 million years ago.…”

Section: Introductionmentioning

confidence: 99%

“…The unit overlies the Lower–Middle Triassic Tarjados Formation through a marked regional unconformity surface of chert and carbonate stringers, and a palaeorelief of up to 10 m (Milana and Alcober, ; Rogers et al ., ; Fiorelli et al ., , ; Ezcurra et al ., ). The lowland areas were filled by superimposed flood cycles of sheet flood to distally braided rivers partially pedogenized, consisting of sandstones and conglomerates of the Tarjadia AZ (Ezcurra et al ., ; Fiorelli et al ., ). CRILAR‐Pv 552 was found 10 m above the base of the M‐Ch AZ.…”

Section: Introductionmentioning

confidence: 99%

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New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina

Ezcurra

Nesbitt

Fiorelli

et al. 2019

The Anatomical Record

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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.

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina

Ezcurra

Nesbitt

Fiorelli

et al. 2019

The Anatomical Record

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“…Moreover, complex tetrapod burrows discovered in several Lower Triassic to Jurassic continental sequences of South America, Africa and Antarctica are considered as being produced by non-mammaliaform cynodonts [137–140]. The thickened bone in the femur of the Andescynodon was interpreted as suggestion of a fossorial lifestyle [141].…”

Section: Discussionmentioning

confidence: 99%

The postcranial anatomy of Brasilodon quadrangularis and the acquisition of mammaliaform traits among non-mammaliaform cynodonts

2019

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Brasilodon quadrangularis (Cynodontia, Probainognathia) is an iconic non-mammaliaform cynodont from the Late Triassic of Brazil ( Riograndia Assemblage Zone, Candelária Sequence), being considered as the sister taxon of Mammaliaformes. Although its phylogenetic position is very important, several aspects of its postcranial anatomy remain unclear or unstudied. Here, we present a detailed description of the postcranial elements referred to Brasilodon , including previously mentioned specimens and new ones, which add relevant information about its postcranial morphology and provide a new insight into the anatomical transition between advanced non-mammaliaform cynodonts and early mammaliaforms. Functional and ecological implications are also investigated, based on the postcranial morphology and muscular reconstructions. The postcranium of Brasilodon differs from most non-mammaliaform cynodonts and presents similarities with tritylodontids, early mammaliaforms and extant therians, such as a ventrally oriented scapular glenoid facet, a distinct and ossified greater humeral tubercle, lack of ectepicondylar foramen, olecranon process, hemispherical humeral and femoral heads and a prominent intertrochanteric crest. The humeral torsion, the length of the deltopectoral crest, the large bicipital groove and the well-developed lesser tubercle, indicate that the forelimb of Brasilodon was hold in a semi-sprawling position, with well-developed adductor muscles to maintain the body off the ground. The short femoral neck and the strong medial projection of the femoral head indicate the femur was held in a more erect posture than in basal non-mammaliaform cynodonts. The anterodorsally projected iliac blade with reduced postacetabular process, reduction of the anterior part of the pubis, medially located lesser trochanter indicate a basically mammalian pattern of pelvic musculature, able to swing the femur in a nearly parasagittal plane.

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Cranial osteology and paleoneurology of Tarjadia ruthae: An erpetosuchid pseudosuchian from the Triassic Chañares Formation (late Ladinian‐?early Carnian) of Argentina

Desojo,

von Baczko,

Ezcurra

et al. 2024

The Anatomical Record

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Tarjadia ruthae is a quadrupedal terrestrial pseudosuchian from the Middle‐early Upper Triassic of the Chañares Formation, La Rioja Province, Argentina. Originally, this species was identified as an indeterminate archosaur and later as a doswelliid archosauriform based on very fragmentary specimens characterized by the ornamentation of the skull roof and osteoderms. Additional specimens (including skulls and postcrania) recovered in the last decade show that Tarjadia is an erpetosuchid, an enigmatic pseudosuchian group composed ofby six species registered in Middle‐Upper Triassic continental units of Tanzania, Germany, Scotland, North America, Brazil, and Argentina. Tarjadia ruthae from Argentina and Parringtonia gracilis from Tanzania are the best preserved and more abundant species. Although the monophyly of Erpetosuchidae is well supported, alternative high‐level positions within Archosauria have been suggested, such as sister taxon to Crocodylomorpha, Aetosauria, or Ornithosuchidae. In order to improve the knowledge about the erpetosuchids, we performed a detailed description and paleoneurological reconstruction of the skull of Tarjadia ruthae, based on two articulated partial skulls (CRILAR‐Pv 478 and CRILAR‐Pv 495) and other fragmentary specimens. We analyzed the stratigraphic and geographic occurrence of historical and new specimens of Tarjadia and provided a new emended diagnosis (the same for the genus as for the species, due to monotypy) along with a comparative description of the cranial endocast. The skull of Tarjadia is robust, with a thick and strongly ornamented skull roof, triangular in dorsal view, with concave lateral margins at mid‐length that form an abrupt widened posterior region. The external nares are the smallest openings of the skull. The antorbital fossa is deeply excavated and has a small heart‐shaped fenestra with both lobes pointing anteriorly. The supratemporal fenestrae are as large and rounded as the orbits, and the infratemporal fenestrae are L‐shaped with an extensive excavation along the jugal, quadratojugal and quadrate. The hemimandibles are low, slightly concave on the dentigerous region and strongly convex on the posterior region, conferring them a S‐shaped profile in dorsal view. The external mandibular fenestra is small and elliptic, being twice longer than high. The maxillary dentition is restricted to the anterior to mid region of the rostrum. Since the braincase of both specimens is partially damaged, the dorsal surface of the brain could not be entirely reconstructed. As a result, the endocast is anteroposteriorly elongated and seemingly flat, and the cephalic flexure seems to be lower than expected for a suchian. The labyrinth is twice wider than high, the semicircular canals are remarkably straight, and the anterior canal is longer than the posterior one.

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Tetrapod burrows from the Middle–Upper Triassic Chañares Formation (La Rioja, Argentina) and its palaeoecological implications

Cited by 27 publications

References 63 publications

New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina

New Specimen Sheds Light on the Anatomy and Taxonomy of the Early Late Triassic Dinosauriforms from the Chañares Formation, NW Argentina

The postcranial anatomy of Brasilodon quadrangularis and the acquisition of mammaliaform traits among non-mammaliaform cynodonts

Cranial osteology and paleoneurology of Tarjadia ruthae: An erpetosuchid pseudosuchian from the Triassic Chañares Formation (late Ladinian‐?early Carnian) of Argentina

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