[Paleontology • 2026] Craniomandibular osteology of Dinodontosaurus isiyavamanda sp. nov. (Therapsida: Anomodontia) from the Manda Beds of Tanzania and new support for a younger age for the alleged oldest dinosaurs

 

Dinodontosaurus isiyavamanda

George, Escobar, Moody, Saanane, Day & Larkin, 2026

DOI: doi.org/10.1080/02724634.2026.2692542

Life reconstruction by Gabriel Ugueto

 

ABSTRACT 

Fossils from the Manda Beds of Tanzania have greatly informed on the diversity and evolution of Triassic tetrapods, including on what might be the oldest dinosaurs. Here, a new dicynodont taxon from the Manda Beds is described. It lacks key anatomical traits of known dicynodonts from the Manda Beds, as well as the Sino-African genus Shansiodon to which some of this material was previously referred. The new taxon is referred to the otherwise South American Dinodontosaurus based on the diagnostic presence of frontals with “tab-like” anterior processes and a combination of other traits seen in the genus. This Tanzanian material possesses a predominantly bulbous posterior/median palatal ridge of the premaxilla and a midline groove along the temporal bar, among other traits that are absent in the South American Dinodontosaurus material, indicating it represents a distinct species, here named Dinodontosaurus isiyavamanda sp. nov. Phylogenetic analyses conducted with Bayesian estimation and parsimony support the inclusion of this species in Dinodontosaurus. The unique palate of D. isiyavamanda is hypothesized to be related to resource partitioning, representing different adaptations for food processing than coeval dicynodonts. The presence of Dinodontosaurus suggests the mid-to-upper Lifua Member of the Manda Beds is equivalent to the Dinodontosaurus Assemblage Zone of Brazil and the Chañares Formation of Argentina. Consequently, the mid-to-upper Lifua Member, which includes what are possibly the oldest records of dinosaurs globally, can be confidently interpreted as late Ladinian to Carnian in age, supporting recent research questioning its equivalency with the Cynognathus Assemblage Zone of South Africa.

SYSTEMATIC PALEONTOLOGY

SYNAPSIDA Osborn, 1903

THERAPSIDA Broom, 1905

ANOMODONTIA Owen, 1860

DICYNODONTIA Owen, 1859

DICYNODONTOIDEA Olson, 1944

KANNEMEYERIIFORMES Maisch, 2001

DINODONTOSAURUS Romer, 1943

Diodontosaurus Tupí-Caldas, 1936 [nomen suppressum].

Chanaria Cox, 1968.

Type Species––Dinodontosaurus oliveirai Romer, 1943 (=Dicynodon tener Huene, 1935).

Diagnosis––Medium- to large-sized kannemeyeriiform (maximum skull length ca. 40 cm) with the following unique combination of character states: frontals with a “tab-like” median anterior process; postorbital bone with elongate, curved suborbital process; elongate caniniform process sharply offset from zygomatic arch; and hypertrophied tusks present in large individuals (taken from Kammerer & Ordoñez, 2021).

DINODONTOSAURUS ISIYAVAMANDA sp. nov.

Ruhuhuungualasaurus croucheri Larkin, 1994, p. 2.

Shansiodon sp. Surkov and Benton, 2004, p. 627.

Shansiodon sp. Surkov and Benton, 2008, p. 1126.

Diagnosis––Can be distinguished from both Dinodontosaurus brevirostris and Dinodontosaurus tener by a premaxillary posterior/median palatal ridge that expands anteriorly into a wide, bulbous morphology (does not retain the ridge-like morphology throughout its length), and extends further anteriorly than the point of eruption of the tusks; a midline groove extending along the temporal bar from immediately posterior to the pineal foramen to the posterior end of the postparietal; and mandibular rami that diverge more laterally. Can be further distinguished from Dinodontosaurus brevirostris by the lack of a ridge along the anterior surface of the mandibular symphysis. Can be further distinguished from Dinodontosaurus tener by a wider interorbital region and snout, and a pineal foramen that is not completely anterior to the intertemporal bar (i.e., pineal foramen is at the same anteroposterior level as the anterior portion of the bar).

Etymology––From the Manda words ‘isi ya vamanda’ that translate to ‘country of the Wamanda.’ In reference to the Wamanda people, many of whom were crucial to the discovery of the holotype, but whose individual names were not documented and never credited.

two bulky Dinodontosaurus isiyavamanda walking through dense vegetation 

Life reconstruction by Gabriel Ugueto

Hady George, Juan A. Escobar, Edmund R.R. Moody, Charles B. Saanane, Michael O. Day and Nigel R. Larkin. 2026. Craniomandibular osteology of Dinodontosaurus isiyavamanda sp. nov. (Therapsida: Anomodontia) from the Manda Beds of Tanzania and new support for a younger age for the alleged oldest dinosaurs. Journal of Vertebrate Paleontology. e2692542. DOI: doi.org/10.1080/02724634.2026.2692542 [15 Sep 2026]

 

[Paleontology • 2024] Cranial Osteology and Paleoneurology of Tarjadia ruthae: An erpetosuchid pseudosuchian from the Triassic Chañares Formation (late Ladinian-?early Carnian) of Argentina

 

Tarjadia ruthae Arcucci & Marsicano, 1998
 

in Desojo, von Baczko, Ezcurra, Fiorelli, Martinelli, ... et Lacerda, 2026. 

DOI: doi.org/10.1002/ar.25382 

Reconstruction: Jorge Blanco

 x.com/AnatRecord

 

Abstract

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 of 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.

Keywords: anatomy, Archosauria, Erpetosuchidae, neuroanatomy, skull

Systematic paleontology

Archosauriformes Gauthier et al., 1988.

Archosauria Cope, 1869 sensu Gauthier & Padian, 1985.

Pseudosuchia von Zittel, 1887–1890 sensu Gauthier & Padian, 1985.

Erpetosuchidae Watson, 1917 sensu Nesbitt & Butler, 2013.

Tarjadia ruthae Arcucci & Marsicano, 1998

Life reconstruction of Tarjadia ruthae by Jorge Blanco.

J. B. Desojo, M. B. von Baczko, M. D. Ezcurra, L. E. Fiorelli, A. G. Martinelli, P. Bona, M. J. Trotteyn and M. Lacerda. 2024. Cranial Osteology and Paleoneurology of Tarjadia ruthae: An erpetosuchid pseudosuchian from the Triassic Chañares Formation (late Ladinian-?early Carnian) of Argentina. The Anatomical Record. DOI: doi.org/10.1002/ar.25382 [23 January 2024]

 x.com/AnatRecord/status/1751938238858854832

[Paleontology • 2026] Silescelida acristata • A New eucrocopodan Archosauriform from the Middle Triassic of southern Brazil and the Phylogeny of Euparkeriidae

Silescelida acristata 

Garcia, Cerqueira, Battista,  Andrade & Müller, 2026

DOI: doi.org/10.1038/s41598-026-53740-9 

life reconstruction by Matheus Fernandes Gadelha. 

Abstract

Archosauriformes comprise a diverse range of reptiles, including the crown-group Archosauria, which flourished during the Triassic Period. Early-diverging archosauriforms, such as proterosuchids and erythrosuchids, are becoming progressively well-known due to recent studies and consistently resolve at the base of the clade. More crownward, Eucrocopoda includes archosauriform taxa that increasingly approximate the ancestral archosaur body plan. Early-diverging eucrocopodan archosauriforms have a widespread paleogeographic record but remain poorly understood in terms of ingroup relationships. Within this radiation, Euparkeriidae is particularly challenging, because its ingroup composition and monophyly is debated, with some authors supporting a non-monospecific Euparkeriidae, whereas others fail to recover this hypothesis. The eponymous Euparkeria capensis is known from the Early to Middle Triassic of South Africa, whereas other putative euparkeriids are primarily known from the Early to Middle Triassic of China, Germany, Poland, and Russia. Here, we describe a new early-diverging eucrocopodan (Silescelida acristata gen. et sp. nov.) from the Middle Triassic of southern Brazil. Phylogenetic analyses incorporating this taxon suggest a possible placement within Euparkeriidae, though its position shows instability depending on the operational taxonomic units considered, especially among other putative euparkeriids. This discovery not only informs on the temporal and paleogeographic distribution of euparkeriids but also sheds light on the origin and early evolution of eucrocopodans, representing the first record of this archosauriform grade in the Triassic of Brazil. More broadly, the new taxon underscores the significance of South American Triassic deposits within the evolutionary history of archosauriforms.

Archosauromorpha von Huene, 1946 sensu Gauthier, 2020

Archosauriformes Gauthier et al., 1988 sensu Gauthier, 2020 

Eucrocopoda Ezcurra, 2016

cf. Euparkeriidae von Huene, 1920 sensu Sookias and Butler, 2013

Provenance and material of Silescelida acristata gen. et sp. nov.
 (A) Map of the Posto site and the surface distribution of the geologic units in the area. (B) General view of the Posto site. (C) Studied specimen MCP 4186-PV (holotype of Silescelida acristata gen. et sp. nov.) showing association between its elements prior to mechanical preparation.
(D) Silhouette and preserved skeletal elements (not to scale) of Silescelida acristata gen. et sp. nov. (ilium reversed).

Abbreviations: fe, femur; il, ilium; sc, scapula. Silhouette and life reconstruction of Silescelida acristata gen. et sp. nov. by Matheus Fernandes Gadelha. Map was generated with GIMP 3.0 (gimp.org) based on the geological map of Rio Grande do Sul (https://rigeo.sgb.gov.br/bitstream/doc/10301/2/Geologico_MDT.pdf).

Silescelida acristata gen. et sp. nov.  

Holotype. MCP 4186-PV, a left scapula, a right ilium, and a left femur (Fig. 1C, D). The elements were found in association (attached to each other) and are size-compatible; therefore, they are considered to belong to the same individual.

Type locality, age, and horizon. Posto (or Posto de Gasolina; Fogliarini) site (29°37’38.9”S 53°22’06.5”W), municipality of Dona Francisca, Rio Grande do Sul, Brazil (Fig. 1A, B). Dinodontosaurus AZ of the Pinheiros-Chiniquá Sequence of the Santa Maria Supersequence, Paraná Basin51,52. It is considered Ladinian in age30,35,53,54,55,56,57,58.

Diagnosis. The holotype of Silescelida acristata differs from all other known non-archosaurian archosauriforms in the following combination of traits: scapular blade without an anteroposterior constriction at its base; asymmetrical expansion of the scapular blade at its dorsal portion; straight posterior margin of the scapular blade, forming a right angle with the dorsal margin of the glenoid; elliptical tuber for the m. triceps dorsal to the glenoid; dorsal margin of the dorsal iliac blade straight in dorsal and lateral views; dorsal iliac blade as deep as the acetabulum; notch between the ischiadic peduncle and the ventral apex of the medial acetabular wall; medially expanded femoral head; absence of a longitudinal groove on the proximal surface of the femoral head; posteromedial tuber as the only well-developed tuber on the femoral head; absence of an elevated mound or crest-like structure as the attachment site for the m. caudofemoralis (local autapomorphy); extensor fossa on the anterior surface of the femoral distal end; distal femoral condyles with the same degree of ventral development (not uneven).

Etymology. The generic name combines the Latin siles (“silence”) and the Greek skelēs (“hind leg”), referencing the loss of the proximal femur bearing the specimen’s collection code, which obscured its provenance until its recent rediscovery. The specific epithet derives from the Latin prefix a- (“without”) and cristāta (“crested”), referring to the absence of a crest or flange attachment site for the m. caudofemoralis (= fourth trochanter), a diagnostic feature of the taxon.

Silescelida acristata gen. et sp. nov. life reconstruction.

 Artwork by Matheus Fernandes Gadelha. 

Biogeography of early-diverging eucrocopodans and paleoart depicting Silescelida acristata gen. et sp. nov. in life.
 (A) Triassic world map depicting the paleogeographic distribution of early-diverging eucrocopods. Classification is based on the phylogenetic analyses in this contribution. Silhouettes (not to scale) based on the skeletal reconstruction of Euparkeria capensis by Demuth et al.83. Dorosuchus neoetus is based on the type-series and Osmolskina czatkowicensis is based on the holotype.
(B) Silescelida acristata gen. et sp. nov. life reconstruction. Artwork by Matheus Fernandes Gadelha. Map was generated with GIMP 3.0 (gimp.org) based on The Paleobiology Database (paleobiodb.org).

 

Maurício S. Garcia, Gabriela M. Cerqueira, Francesco Battista, Marco B. de Andrade and Rodrigo T. Müller. 2026. A New eucrocopodan Archosauriform from the Middle Triassic of southern Brazil and the Phylogeny of Euparkeriidae. Scientific Reports. 16: 16585. DOI: doi.org/10.1038/s41598-026-53740-9  [10 June 2026]

 

[Paleontology • 2023] Samsarasuchus pamelae • A New archosauriform Species (Archosauriformes: Proterosuchidae) from the Panchet Formation of India and the Diversification of Proterosuchidae after the end-Permian Mass Extinction

Samsarasuchus pamelae 

Ezcurra, Bandyopadhyay, Sengupta, Sen, Sennikov, Sookias, Nesbitt & Butler, 2023

 DOI: 10.1098/rsos.230387 

 twitter.com/ButlerLabBham

artwork: Gabriel Lio

Abstract

Proterosuchidae represents the oldest substantial diversification of Archosauromorpha and plays a key role in understanding the biotic recovery after the end-Permian mass extinction. Proterosuchidae was long treated as a wastebasket taxon, but recent revisions have reduced its taxonomic content to five valid species from the latest Permian of Russia and the earliest Triassic (Induan) of South Africa and China. In addition to these occurrences, several isolated proterosuchid bones have been reported from the Induan Panchet Formation of India for over 150 years. Following the re-study of historical specimens and newly collected material from this unit, we erect the new proterosuchid species Samsarasuchus pamelae, which is represented by most of the presacral vertebral column. We also describe cf. proterosuchid and proterosuchid cranial, girdle and limb bones that are not referred to Samsarasuchus pamelae. Phylogenetic analyses recovered Samsarasuchus pamelae within the new proterosuchid clade Chasmatosuchinae. The taxonomic diversity of Proterosuchidae is substantially expanded here, with at least 11 nominal species and several currently unnamed specimens, and a biogeographical range encompassing present-day South Africa, China, Russia, India, Brazil, Uruguay and Australia. This indicates a broader taxonomic, phylogenetic and biogeographic diversification of Proterosuchidae than previously thought in the aftermath of the end-Permian mass extinction.

Keywords: phylogeny, biogeography, Proterosuchidae, Archosauromorpha, Induan, Mesozoic

 

Diapsida Osborn, 1903

Archosauromorpha von Huene, 1946

Archosauriformes Gauthier, Kluge & Rowe, 1988

Proterosuchidae von Huene, 1908 sensu Ezcurra, Butler & Gower, 2013

Chasmatosuchinae nov.

 

 Phylogenetic definition: The most inclusive clade containing Chasmatosuchus rossicus von Huene, 1940, but not Proterosuchus fergusi Broom, 1903, ‘Chasmatosaurus’ yuani Young, 1936, Proterosuchus alexanderi (Hoffman, 1965), Proterosuchus goweri Ezcurra & Butler, 2015, Erythrosuchus africanus Broom, 1905, or Alligator mississippiensis Daudin, 1802. This is a maximum clade definition.

   Composition: The composition is based on the reference phylogeny. Chasmatosuchinae includes Chasmatosuchus rossicus, Jaikosuchus magnus, Samsarasuchus pamelae, Archosaurus rossicus, Gamosaurus lozovskii, Tsylmosuchus spp., Vonhuenia friedrichi and indeterminate specimens from the Arcadia Formation and Bulgo Sandstone of the Sydney Basin of Australia and the Sanga do Cabral Formation of Brazil.

 Diagnosis: Chasmatosuchines differ from other proterosuchids in the presence of anterior–middle and sometimes posterior postaxial cervical vertebrae with distally restricted transverse expansion of the neural spines (not mammillary process); third to eighth or ninth presacral vertebrae with diagonal, anterodorsally-to-posteroventrally oriented ridge that reaches the base of the prezygapophysis and is not connected to the diapophysis on the lateral surface of the neural arch; fourth to eight presacral vertebrae with posterior expansion of the dorsal portion of the neural spine, resulting in a posterodorsally tilted posterior margin set at an angle higher than 15° with respect to the anterior margin of the neural spine in lateral view; ninth presacral centrum with a ventral keel and anterior caudal vertebrae with surface lateral to the base of the neural spine with a very deep fossa, well-defined laterally and that transversely constricts the anterior half of the neural spine.

  Geographical and stratigraphic occurrence of specimens of Samsarasuchus pamelae gen. et sp. nov. and Panchet cf. proterosuchid and proterosuchid specimens.
(a) Gondwana basins of peninsular India showing the studied area of the Damodar Basin, which has yielded specimens of Samsarasuchus pamelae; (b) geological map showing the location of the Deoli locality that yielded Samsarasuchus pamelae bones discovered by the 2015 fieldtrip; (c) composite stratigraphic column of the Panchet Formation, including the occurrence of the Samsarasuchus pamelae bones discovered by the 2015 fieldtrip; (d) general overview of the sandstones of the Deoli locality on the shore of the Damodar River (January 2015); and (e) close up of the holotype of Samsarasuchus pamelae (ISIR 1091) as found in the field.

Samsarasuchus pamelae gen. et sp. nov.

Diagnosis: Samsarasuchus pamelae is a chasmatosuchine proterosuchid that differs from other non-archosaurian archosauriforms in the following autapomorphies (among non-archosaurian archosauriforms) present in its holotype (ninth cervical vertebra): posteriormost cervical vertebra (ninth cervical vertebra) with two pairs (i.e. four in total) of mammillary processes on the neural spine; and posteriormost cervical vertebra (ninth cervical vertebra) with dorsolaterally oriented mammillary processes on the anterior region of the neural spine. In addition, the holotype of Samsarasuchus pamelae and the other postaxial cervical and anterior–middle dorsal vertebrae referred to this species share the following unique combination of character states that allow the species to be distinguished from other non-erythrosuchid, non-eucrocopod archosauriform nominal species: third cervical to anterior dorsal vertebrae ....

Etymology: The genetic epithet is formed by the Sanskrit word ‘Saṁsāra’ (Samsara) that in Hinduism is related to the cycle of re-birth, existence and death, and ‘Σοῦχος’ (Suchus), which is the name of the Egyptian crocodile-headed deity Sebek or Sobek in ancient Greek, referring to the re-birth of ecosystems after the end-Permian mass extinction and the most common ending (-suchus) of archosauromorph genera. The specific epithet is for the first name of the British palaeontologist Pamela Lamplugh Robinson (1919–1994) in honour of her contributions to Indian vertebrate palaeontology and especially for having prompted a renewed interest in the vertebrate palaeontology of the Panchet Formation in the 1960s after a long gap in research since the end of the ninteenth century. In addition, Pamela Robinson led the fieldtrip that resulted in the discovery of several referred specimens of this new proterosuchid species (NHMUK collection).

 

Martín D. Ezcurra, Saswati Bandyopadhyay, Dhurjati P. Sengupta, Kasturi Sen, Andrey G. Sennikov, Roland B. Sookias, Sterling J. Nesbitt and Richard J. Butler. 2023. A New archosauriform Species from the Panchet Formation of India and the Diversification of Proterosuchidae after the end-Permian Mass Extinction. R. Soc. open sci. 10230387. DOI: 10.1098/rsos.230387

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[Paleontology • 2023] On A skeletally Immature Individual of Unaysaurus tolentinoi (Dinosauria: Sauropodomorpha) from the upper Triassic of southern Brazil

Unaysaurus tolentinoi  Leal, Azevodo, Kellner & da Rosa, 2004

in Müller, Garcia, Bem, Damke, Fonseca & Da-Rosa, 2023. 

DOI: 10.1002/ar.25285

 twitter.com/AnatRecord

 www.UFSM.br

artwork: Caetano Soares

 

Abstract

The lineage of sauropodomorph dinosaurs raised some of the most impressive animals that ever walked on Earth. However, the massive titans of the Mesozoic Era originated from far smaller dinosaurs. The Triassic beds from Brazil yielded the earliest part of this evolutionary history. Despite the diverse fossil record of early sauropodomorphs, juvenile specimens, as well as certain species are poorly sampled. This is the case for Unaysaurus tolentinoi, an unaysaurid sauropodomorph from Caturrita Formation (ca. 225 Ma; early Norian, Late Triassic). The holotype and only specimen of U. tolentinoi was excavated from the Água Negra Locality (São Martinho da Serra, Rio Grande do Sul, Brazil) in 1998. More than two decades later, no other fossil vertebrates have been reported from the same fossiliferous site. Here we describe a skeletally immature specimen which was found in association with the holotype of U. tolentinoi. The specimen was discovered after a first-hand examination of the holotype and comprises some isolated vertebrae and elements from the posterior autopodium. According to linear regressions, its metatarsal I is approximately 41.7 mm in length, compared to approximately 75.9 mm in the holotype. The repeated elements and reduced size indicates that it does not belong to the elements originally used to erect U. tolentinoi. Rather, the specimen is assigned to U. tolentinoi by topotypy and shared morphology. In addition to the reduced size, distinct lines of evidence (e.g., neurocentral sutures; bone texture) support its assignment to a skeletally immature individual. In sum, the new material expands the record of U. tolentinoi, and represents an additional juvenile dinosaur from the Caturrita Formation.

Keywords: Archosauriformes, Brazil, Middle-Late Triassic, Proterochampsidae, Santa Maria Supersequence

 

Rodrigo T. Müller, Maurício S. Garcia, Fabiula P. Bem, Lísie V. S. Damke, André O. Fonseca and Átila A. S. Da-Rosa. 2023. On A skeletally Immature Individual of Unaysaurus tolentinoi (Dinosauria: Sauropodomorpha) from the upper Triassic of southern Brazil. The Anatomical Record. DOI: 10.1002/ar.25285

 twitter.com/AnatRecord/status/1679826828335120384

 www.UFSM.br/2023/07/12/fossil-de-dinossauro-jovem

[Paleontology • 2023] Kuruxuchampsa dornellesi & Pinheirochampsa rodriguesi • New rhadinosuchine proterochampsids from the late Middle-early Late Triassic of southern Brazil enhance the Diversity of Archosauriforms

Pinheirochampsa rodriguesi

Paes-Neto, Lacerda, Ezcurra, Raugust, Trotteyn, Soares, Schultz, Pretto, Francischini & Martinelli, 2023

DOI: 10.1002/ar.25294 

 twitter.com/voltairearts 

 twitter.com/AnatRecord

Abstract

Proterochampsidae is a clade of non-archosaurian archosauriforms restricted to the Middle to the Late Triassic of the Ischigualasto-Villa Unión Basin of Argentina and the Santa Maria Supersequence of Brazil. A reappraisal of proterochampsid specimens from the Brazilian Dinodontosaurus Assemblage Zone (AZ) of the Pinheiros-Chiniquá Sequence (late Ladinian-early Carnian) is presented here. One of the specimens was preliminary assigned to Chanaresuchus sp., whose type species comes from the Massetognathus-Chanaresuchus AZ of the Chañares Formation of Argentina. However, our revision indicates that it differs from Chanaresuchus, being more closely related to the middle-late Carnian Rhadinosuchus gracilis. We therefore propose the new taxon, Pinheirochampsa rodriguesi, to reallocate this specimen. Additionally, we present a revision of other putative Chanaresuchus occurrences in Brazil, including the only known specimen described for the Santacruzodon AZ (Santa Cruz do Sul Sequence; early Carnian), also proposing it as a new taxon: Kuruxuchampsa dornellesi. Both new species are characterized, among other features, by transverse expansion of the anterior end of the rostrum, similar to the condition present in Rhadinosuchus, but absent in Chanaresuchus, Gualosuchus, Pseudochampsa, and non-rhadinosuchine proterochampsids. These two new species expand the growing knowledge of the non-archosaurian archosauriform diversity during the Middle-Late Triassic in South America and enhance faunal and chronological comparisons between approximately coeval geological units between Argentina and Brazil.

Pinheirochampsa rodriguesi

Kuruxuchampsa dornellesi

Voltaire D. Paes-Neto, Marcel B. Lacerda, Martín D. Ezcurra, Tiago Raugust, María J. Trotteyn, Marina B. Soares, Cesar L. Schultz, Flávio A. Pretto, Heitor Francischini and Agustín G. Martinelli. 2023. New rhadinosuchine proterochampsids from the late Middle-early Late Triassic of southern Brazil enhance the Diversity of Archosauriforms. The Anatomical Record. DOI: 10.1002/ar.25294

  twitter.com/voltairearts/status/1698780552042631334

  twitter.com/AnatRecord/status/1695074792720965716

[Paleontology • 2023] Colossosuchus techniensis • A Giant Phytosaur (Diapsida: Archosauria) from the Upper Triassic of India with New insights on Phytosaur Migration, Endemism and Extinction

Colossosuchus techniensis

Datta & Ray, 2023 

 

DOI: 10.1002/spp2.1476 

  twitter.com/ThePalAss 

Abstract

A new Mystriosuchinae phytosaur, Colossosuchus techniensis, is described from the Upper Triassic Tiki Formation of India. Colossosuchus is diagnosed by multiple apomorphies, including a strongly downturned terminal rosette (c. 70°), closely spaced mediolateral band-like ornamentation on dorsal surface of the nasal, dorsolaterally oriented supratemporal fenestra, ventrolaterally inclined postorbital–squamosal bars depressed below the skull table, dorsally convex parietal–squamosal bar that descends ventrolaterally below the skull roof, dome-shaped skull in lateral view, prominent neural arch laminae and fossae, three sacral vertebrae, robust proximal end of the tibia, and fibula with high anteroposterior flaring of the distal end. The total body length of the largest individual recovered from the bonebed is estimated to be more than 8 m, suggesting that Colossosuchus is one of the largest phytosaurs known. Phylogenetic analysis nests Colossosuchus and other undescribed specimens from India within Mystriosuchinae. These form a distinct clade and represent the earliest record of endemism among Gondwanan phytosaurs. This clade is recovered as sister taxa to ((Volcanosuchus + Rutiodon) + Leptosuchomorpha), where the depressed supratemporal fenestra first appeared in the phytosaur lineage, a feature previously used to diagnose the derived leptosuchomorphs. Early-diverging phytosaur diversification may have coincided with the final stages of the Carnian Pluvial Event with their possible migratory routes along the circum-Tethyan coastline. The lineage continued to evolve mostly through endemic radiations and experienced an extinction event during early Norian, which marked the disappearance of most of the non-leptosuchomorph taxa. This is attributed to post-CPE aridification, although more study is required.

Keywords: archosaur, Gondwana, India, Upper Triassic, phytosaur, phylogeny

Colossosuchus techniensis

Debajit Datta and Sanghamitra Ray. 2023.  A Giant Phytosaur (Diapsida, Archosauria) from the Upper Triassic of India with New insights on Phytosaur Migration, Endemism and Extinction. Papers in Palaeontology. DOI: 10.1002/spp2.1476 

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[Paleontology • 2022] Stenoscelida aurantiacus • A New Proterochampsid (Archosauriformes: Proterochampsia) from the Late Triassic of southern Brazil and the Emergence of Archosaurian Hind Limb Traits

Stenoscelida aurantiacus

Müller, Garcia & Oliveira Fonseca, 2022

DOI: 10.1080/14772019.2022.2128913  

Researchgate.net/publication/365070083

 Abstract

Characterized by an elongated snout, proterochampsids are carnivorous non-archosaur archosauriforms. The clade is endemic to South America and its fossil record extends from the early Carnian to the late Carnian/early Norian. Nesting close to Archosauria, it is a key clade for understanding the origin and evolution of archosaurian traits. Unfortunately, hind limb elements are usually poorly preserved for the group. Therefore, the hind limb anatomy of proterochampsids still lacks detailed descriptions. In the present study, we partially fill this gap with the description of a new proterochampsid represented by a complete and well-preserved hind limb. Stenoscelida aurantiacus gen. et sp. nov. was excavated from the late Carnian/early Norian (Late Triassic) beds of southern Brazil. A phylogenetic investigation recovers the new taxon as a non-rhadinosuchine proterochampsid. The species bears an unusual set of traits for the group, which provides clues on the evolutionary origins of some muscle attachment structures. For instance, the femur of Stenoscelida aurantiacus gen. et sp. nov. possesses an anterior trochanter and an anterolateral scar. So far, these features have not been reported in other non-archosaurian archosauriforms. Therefore, the new specimen indicates that some typical archosaurian features evolved earlier than previously thought. The taxon also carries additional uncommon features for proterochampsids, such as an iliofibularis tubercle on the anterior margin of the fibula and a vestigial phalanx in digit V. In sum, Stenoscelida aurantiacus has one of the best-preserved hind limbs within Proterochampsidae and sheds light on the polarization of important traits regarding the evolutionary context of Archosauria.

 

Keywords: Archosauria, Archosauromorpha, Carnian, Gondwana, Proterochampsidae, South America

Provenance of Stenoscelida aurantiacus gen. et sp. nov. (CAPPA/UFSM 0293).
A, location and geological context of the Varzea do Agudo site (Agudo, Rio Grande do Sul, Brazil; modified from Muller et al. 2020a); B, general view of the site;
C, reconstruction of the skeleton of Stenoscelida aurantiacus gen. et sp. nov. (CAPPA/UFSM 0293) depicting the preserved elements.

 Holotype of Stenoscelida aurantiacus gen. et sp. nov. (CAPPA/UFSM 0293). Right hind limb in A, medial and B, lateral views.

Abbreviations: 4t, fourth trochanter; a, astragalus; als, anterolateral scar; at, anterior trochanter; c, calcaneum; cc, cnemial crest; f, femur; fh, femoral head; fi, fibula; ift, iliofibularis tubercle; mc, medial condyle; mt, metatarsal; pf, popliteal fossa; ph, phalanx; t, tibia.

 Results of the phylogenetic analysis depicting the position of Stenoscelida aurantiacus.
 A, time-calibrated reduced strict consensus tree (number on nodes represent Bremer support values higher than 1); B, strict consensus tree depicting the occurrence and distribution of the anterior trochanter (at) and the anterolateral scar (als) in the proximal portion of the femora of some panarchosaurs.

Stenoscelida aurantiacus gen. et sp. nov.

 

Rodrigo Temp Müller, Mauricio Silva Garcia and André de Oliveira Fonseca. 2022. A New Proterochampsid (Archosauriformes: Proterochampsia) from the Late Triassic of southern Brazil and the Emergence of Archosaurian Hind Limb Traits. Journal of Systematic Palaeontology. 20(1);  2128913. DOI: 10.1080/14772019.2022.2128913  

Researchgate.net/publication/365070083_A_new_proterochampsid_from_the_Late_Triassic_of_southern_Brazil

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[Paleontology • 2022] Taphonomy of Drought afflicted Tetrapods in the Early Triassic Karoo Basin, South Africa

Mummified skin on spreadeagled Lystrosaurus 

in Smith, Botha & Viglietti, 2022. 

DOI: 10.1016/j.palaeo.2022.111207

Highlights: 

• Outcrop containing hundreds of Early Triassic tetrapod fossils interpreted as evidence of drought.

• Clusters of articulated skeletons interpreted as drought-induced aggregations.

• Mummified skin on spreadeagled Lystrosaurus suggest rapid desiccation after death by starvation.

• Bone histology confirms that all the Lystrosaurus were juveniles or early sub-adult.

• Bonebeds of juvenile Lystrosaurus are interpreted as sheet-washed behavioural aggregations.

Abstract

The sedimentology and taphonomy of in-situ fossils from earliest Triassic strata (Induan) in the southern Karoo Basin of South Africa is presented as evidence for episodes of drought-induced mass death of the resident tetrapods. Abundant skeletons are preserved in a 2 m-thick tabular silty-sandstone capping a multi-storeyed low-sinuosity channel sandstone interpreted as a wide shallow channel that became progressively abandoned, with more ephemeral flow regime than in the underlying channels and subjected to intermittent flows of low-density sediment-laden floodwaters. Stratigraphic and planimetric distribution of 170 in-situ tetrapod fossils shows several clusters of up to eight closely-spaced articulated Lystrosaurus skeletons preserved in prone and spread-eagled body position. These are interpreted as drought-stricken carcasses that collapsed and died of starvation in and alongside dried-up water sources. Two of the specimens display an unusual micritic envelope with a distinctive pustular texture interpreted as permineralised mummified skin indicative of rapid desiccation after death. Bonebeds of disarticulated bones of multiple juvenile Lystrosaurus occur in shallow depressions within the rubified mudstones. Layering of different skeletal elements suggests some hydraulic sorting but the initial aggregation was likely a behavioural response to drought. Osteohistology of spread-eagled Lystrosaurus (L. declivis and L. murrayi species) skeletons show that they represent early juvenile stage which is in accordance with previous findings that throughout Pangaea Early Triassic Lystrosaurus died relatively young due to environmental stressors. Our results support the hyperthermal hypothesis that ~252 Mya increased continental aridity, already a consequence of the coalescence of Pangaea, was critically intensified by volcanogenic greenhouse gasses from the Siberian traps. We propose that in the aftermath of the End-Permian mass extinction event, a succession of climatic drying episodes orchestrated a series of fully-functioning terrestrial ecosystems that were markedly different to those of the pre-extinction, and likely had a profound and lasting influence on the evolution of tetrapods.

Keywords: Early Triassic, Katberg Formation, Lystrosaurus, Drought accumulations, Bonebeds, Mummified skin

Roger M.H. Smith, Jennifer Botha and Pia A. Viglietti. 2022. Taphonomy of Drought afflicted Tetrapods in the Early Triassic Karoo Basin, South Africa. Palaeogeography, Palaeoclimatology, Palaeoecology. In Press, 111207. DOI: 10.1016/j.palaeo.2022.111207 

[Paleontology • 2021] Syntomiprosopus sucherorum • A New Short-faced Archosauriform from the Upper Triassic Placerias/Downs’ Quarry Complex, Arizona, USA, expands the Morphological Diversity of the Triassic Archosauriform Radiation

Syntomiprosopus sucherorum

 Heckert, Nesbitt, Stocker, Schneider, Hoffman & Zimmer, 2021

 

DOI: 10.1007/s00114-021-01733-1

Illustration: twitter.com/clepsydrops 

Abstract

The Placerias/Downs’ Quarry complex in eastern Arizona, USA, is the most diverse Upper Triassic vertebrate locality known. We report a new short-faced archosauriform, Syntomiprosopus sucherorum gen. et sp. nov., represented by four incomplete mandibles, that expands that diversity with a morphology unique among Late Triassic archosauriforms. The most distinctive feature of Syntomiprosopus gen. nov. is its anteroposteriorly short, robust mandible with 3–4 anterior, a larger caniniform, and 1–3 “postcanine” alveoli. The size and shape of the alveoli and the preserved tips of replacement teeth preclude assignment to any taxon known only from teeth. Additional autapomorphies of S. sucherorum gen. et sp. nov. include a large fossa associated with the mandibular fenestra, an interdigitating suture of the surangular with the dentary, fine texture ornamenting the medial surface of the splenial, and a surangular ridge that completes a 90° arc. The external surfaces of the mandibles bear shallow, densely packed, irregular, fine pits and narrow, arcuate grooves. This combination of character states allows an archosauriform assignment; however, an associated and similarly sized braincase indicates that Syntomiprosopus n. gen. may represent previously unsampled disparity in early-diverging crocodylomorphs. The Placerias Quarry is Adamanian (Norian, maximum depositional age ~219 Ma), and this specimen appears to be an early example of shortening of the skull, which occurs later in diverse archosaur lineages, including the Late Cretaceous crocodyliform Simosuchus. This is another case where Triassic archosauriforms occupied morphospace converged upon by other archosaurs later in the Mesozoic and further demonstrates that even well-sampled localities can yield new taxa.

Keywords: Crocodylomorpha, Convergent evolution, Norian, Jaw, Diversity, Archosauriformes

Systematic paleontology

ARCHOSAUROMORPHA von Huene 1946 sensu Benton 1985

ARCHOSAURIFORMES Gauthier et al. 1988

?CROCODYLOMORPHA Walker 1968 sensu Sereno et al. 2005

Syntomiprosopus gen. nov.

 Syntomiprosopus sucherorum gen. et sp. nov.

Locality and horizon: The Downs’ Quarry, at a stratigraphic level slightly above the primary “Placerias Quarry” bone level but approximately 1 m below the principal Downs’ Quarry horizon (see stratigraphy and age; Fig. 2). Detrital zircons indicate a maximum depositional age of 219.39 ± 0.16 Ma for this assemblage (Ramezani et al. 2014).

Diagnosis:

The presence of denticulated thecodont teeth and an external mandibular fenestra constrain Syntomiprosopus sucherorum to at least within Archosauriformes (Nesbitt 2011). Syntomiprosopus sucherorum differs from all other archosauromorphs by the following combination of character states: a small external mandibular fenestra is present; an interdigitating suture of the surangular with the dentary; a laterally extensive, rounded, and heavily sculptured surangular ridge on the lateral side of the surangular; a low length-to-depth ratio of the mandible (length:depth ~2.5:1)*; a surangular ridge that completes a 90° arc posteriorly on the lateral side of the surangular*; a dentition restricted to the anterior half of the dentary and consisting of 8 or fewer teeth; anterior and posterior teeth separated by a large (“caniniform”) tooth in the third or fourth position; teeth with a lingual “heel” at their bases; procumbent anterior dentition; uniquely and coarsely sculptured lateral surfaces of the angular, surangular, and dentary*; a well-defined foramen intermedius oralis caudalis bordered medially by the splenial and angular; fine sculpturing consisting of low grooves on the medial surface of the splenial*; well-defined dentary symphysis located on the ventral half of the anteriormost portion of the medial side of the element. Local autapomorphies are identified with an asterisk.

Together with the paratypes, Syntomiprosopus is also unique in that it has a variable number of tooth positions anterior and posterior to the identified “caniniform” tooth and high variability in sculpturing of the lateral surfaces of the angular, surangular, and dentary and the medial surface of the splenial.

Etymology: The genus name comes from the Greek syntomi- meaning “short” and -prosopus, meaning “face” in reference to the greatly shortened mandible relative to contemporaneous archosauriforms. The specific epithet sucherorum is in honor of Scott (“Major”) and Karen Sucher, who have spent much time and effort over the last 22 years supporting paleontological excavations by ABH and his crews, including participating in and otherwise supporting excavations at the Downs’ Quarry that yielded Syntomiprosopus.

 

Conclusions: 

Syntomiprosopus represents a new taxon with a morphology that is dramatically different from any contemporaneous relative, regardless of whether it is a non-archosaurian archosauriform or a crocodylomorph. If Syntomiprosopus is a non-archosaurian archosauriform, it is a relatively late-surviving taxon coexisting with diverse crown-group archosaurs. If, as the associated posterior portion of the skull suggests, it represents an early diverging crocodylomorph, then it reveals a surprising range of morphological innovation among early members of this clade. This new taxon is another example of a Triassic archosauriform taxon whose general morphology is converged upon by later Mesozoic taxa, in this case the short-snouted crocodyliform Simosuchus from the Late Cretaceous of Madagascar. Finally, in spite of the extensive history of collecting vertebrates at the Placerias/Downs’ Quarry complex, which is the most diverse nonmarine Triassic tetrapod locality currently known, Syntomiprosopus demonstrates that even well-studied localities have the potential to yield surprising new taxa.

Andrew B. Heckert, Sterling J. Nesbitt, Michelle R. Stocker, Vince P. Schneider, Devin K. Hoffman and Brian W. Zimmer. 2021. A New Short-faced Archosauriform from the Upper Triassic Placerias/Downs’ Quarry Complex, Arizona, USA, expands the Morphological Diversity of the Triassic Archosauriform Radiation. The Science of Nature. 108, 32. DOI: 10.1007/s00114-021-01733-1

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