Sérgio Dias-da-Silva

Phylogenetic reappraisal of Rhytidosteidae (Stereospondyli: Trematosauria), temnospondyl amphibians from the Permian and Triassic

All stereospondyl taxa previously placed within Rhytidosteidae are reviewed in a phylogenetic context. A parsimony analysis shows that Pneumatostega, Trucheosaurus, Rhytidosteus and Nanolania are placed outside Rhytidosteidae. If an implied weighting method is introduced in order to downweight homoplastic characters, then these taxa are placed within rhytidosteids (with the exception of Rhytidosteus), thus forming a resolved monophyletic group. This group is supported by four synapomorphies, including a twisted pterygoid quadrate ramus and sculpture consisting of a reticulate pattern with pustules or nodules at the junction between adjacent crests and ridges. Based on the topology of a majority rule consensus tree, we postulate a close relationship among all eastern Gondwanan rhytidosteids (Australian and Indian taxa) and among western Gondwanan taxa (South America, South Africa and Madagascar). Laurasian Boreopelta and Peltostega are successive paraphyletic taxa of both eastern and western groups. The Australian family ‘Derwentiidae’ is nested within Rhytidosteidae and is redefined as a subfamily (Derwentiinae nov.) which also includes Indobrachyops. Peltosteginae and Indobrachyopidae as currently defined in the literature are not supported. Rhytidosteinae is also not supported because Laidleria, Pneumatostega and Rhytidosteus do not emerge as a clade. The presence of the rhytidosteid Trucheosaurus major in the Late Permian of Australia suggests that rhytidosteids were already diversified at that time. Increasing efforts to collect Upper Permian and Lower Triassic rhytidosteids should help to improve stratigraphical, palaeogeographical and phylogenetic information regarding this widespread group of temnospondyls.

Occurrence of giant stereospondyl remains in the Santa Maria Formation (Middle/Upper Triassic of southern Brazil)

The first occurrence of stereospondyl remains in the Santa Maria Formation (Middle/Upper Triassic) of the Paraná Basin is reported. The material is fragmentary but indicates the presence of large stereospondyls in the Carnian of this unit. The lack of informative characters is an obstacle, but the specimens probably belong to metoposaurids, trematosaurids or mastodonsauroids. Most South American reports of stereospondyls record fragmentary remains (except for the Argentinean chigutisaurids, and the Brazilian Australerpeton cosgriffi—a rhinesuchoid, and Sangaia lavinai—a rhytidosteid), and this situation constrains generalized attempts to understand their likely sequence of occupation in this part of Gondwana during the upper Palaeozoic and lower Mesozoic. Nevertheless, this new record is important, since it increases the representation of stereospondyls in southern Brazil. Moreover, it expands their biostratigraphic range in the Rosário do Sul Group.

Middle Devonian Crinoids from the Parnaiba Basin (Pimenteira Formation, Tocantins State, Brazil)

Abstract This contribution presents the first description of crinoids from western margin of Parnaíba Basin. It also presents their first description in the Pimenteira Formation (Devonian of the Parnaíba Basin, state of Tocantins, Brazil). The material is represented by hundreds of columnals, pluricolumnals, as well as isolated calyx plates. Columnal and pluricolumnal morphology allowed the identification of Laudonomphalus aff. L. tuberosus, and Exaesiodiscus dimerocrinosus n. sp. Based upon calyx plate morphology a new Rhodocrinitidae species was erected, Monstrocrinus incognitus n. sp. The genera Exaesiodiscus, Laudonomphalus, and Monstrocrinus were previously described from the Devonian of Amazonas Basin. Exaesiodiscus dimerocrinosus is also identified from the northwest margin of Paraná Basin. The Monstrocrinus occurrence is rare in the Middle Devonian, until now known in Germany, Spain, and Algeria Lower Devonian (upper Emsian) and only in northern Brazil in the Middle Devonian (Eifelian.) These facts provide valuable arguments for paleogeographic interpretations regarding the pattern of distribution of invertebrates in this region of Gondwana and suggest potential migration routes in northern Gondwana during the Devonian.

On the presence of a pustulated temnospondyl in the Lower Triassic of southern Brazil

The fossil record of temnospondyls in South America has been greatly expanded in the last 10 years, increasing their overall significance. They occur in Argentina, Brazil, and Uruguay, and range from the Guadalupian to the Late Triassic. The Early Triassic temnospondyl record in southern Brazil is mainly composed of fragmentary specimens, usually represented by dermal skull bones from the Sanga do Cabral Formation. Some of these fragments were tentatively referred to Lydekkerinidae and Rhytidosteidae based on their characteristic ridge-grooved “spider-web” pattern of ornamentation. In this contribution we report, for the first time, a temnospondyl skull fragment with pustulated sculpturing pattern, which is tentatively ascribed to Plagiosauridae. This new record could indicate the presence of a new temnospondyl taxon for the Lower Triassic of South America.

The femoral anatomy of Pampadromaeus barberenai based on a new specimen from the Upper Triassic of Brazil

Femora of the holotype and only previously known specimen of the early sauropodomorph Pampadromaeus barberenai are incomplete and fractured. Here, we describe a new complete femur assigned to Pampadromaeus barberenai, quarried from the same outcrop of original type specimen: ‘Janner’ site, (Carnian of the Paraná Basin). It shares with the holotype of Pampadromaeus barberenai a unique combination of features: anteromedial tuber slightly posteromedially displaced; lesser trochanter proximodistally oriented with the proximal tip gently connected to the femoral shaft; fourth trochanter located on the medial margin along the mediolateral axis of the femur and with an assymetrical outline. In addition, we propose a femoral autapomorphy for Pampadromaeus barberenai: lateral condyle of the distal end of the femur extremely reduced lateromedially. Two distinct phylogenetic analyses place the new specimen as the sister-group of the Pampadromaeus barberenai type-specimen and, in one of them, they are nested within Sauropodomorpha, corroborating the original description and taxonomic assignation.

New Dinosauriform (Ornithodira, Dinosauromorpha) Record from the Upper Triassic of Southern Brazil

1Laboratorio de Paleobiologia, Campus de Sao Gabriel, Universidade Federal do Pampa, Avenida Antonio Trilha, 1847, Bairro Centro, CEP 97.300-000, Sao Gabriel, Rio Grande do Sul, Brazil (e-mail: sergiosilva@unipampa.edu.br) 2Departamento de Biologia, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo (USP), Av. Bandeirantes, 3900, CEP 14040-901, Ribeirao Preto, Sao Paulo, Brazil 3Universidade Regional Integrada do Alto Uruguai e das Missoes (URI) Campus de Frederico Westphalen, Rio Grande do Sul, Brazil

A new Permian temnospondyl with Russian affinities from South America, the new family Konzhukoviidae, and the phylogenetic status of Archegosauroidea

A new Permian temnospondyl from South America is described and considered to represent a new species – Konzhukovia sangabrielensis sp. nov. – of the genus Konzhukovia previously recorded exclusively from Russia. It consists of the anterior half and partial right side of the skull roof and palate. A comprehensive phylogenetic analysis was performed with several archegosauroids and other well-supported groups of temnospondyls in order to access the affinities of the new Brazilian species and test the monophyly of Archegosauroidea. Archegosauroidea was not recovered as a monophyletic group, comprising successive paraphyletic taxa. The only monophyletic group of ‘archegosauroids’ is the ‘Tryphosuchinae’ (in a sister-group relationship with Stereospondyli), composed of Tryphosuchus paucidens, Konzhukovia vetusta, K. tarda and K. sangabrielensis. As the diagnosis of T. paucidens is unclear and based on incomplete material, nested among three species of Konzhukovia, we consider this taxon to be a nomen dubium and purge it from the strict consensus tree. An alternative solution would be to erect a new taxonomic combination for T. paucidens. In order to solve these taxonomic problems, it is necessary to discover more complete material with a clear set of diagnostic characters, to either revalidate this taxon or provide a new combination for it. The phylogenetic results support the erection of a new family – Konzhukoviidae – to replace ‘Tryphosuchinae’ and accommodate Konzhukovia vetusta, K. tarda and K. sangabrielensis, the new Brazilian species basal to the Russian forms. An early diverging konzhukoviid in Gondwana leads to interesting insights regarding the evolution of the new family, stereospondyl origins, their early diversification and their palaeobiogeographical patterns of distribution. http://zoobank.org/urn:lsid:zoobank.org:pub:4772DC7E-C427-4F5F-89FD-9E68E3B0BFD5

Biostratigraphic significance of a new early sauropodomorph specimen from the Upper Triassic of southern Brazil

Abstract The Wachholz site (Caturrita Formation, Late Triassic), in Agudo, Rio Grande do Sul (RS), southern Brazil, has yielded several sauropodomorphs. This includes CAPPA/UFSM 0002, described here based on associated elements from the basalmost portion of the site. The specimen possesses a set of traits shared with typical ‘prosauropods’: a concave caudal margin of the trunk neural spines and a broadly convex proximal end of metacarpal V. However, it also retains some plesiomorphic features, for instance, the slender pedal digit I. Some bones closely resemble those of Unaysaurus tolentinoi, the other definitive sauropodomorph from the Caturrita Formation, an affinity corroborated by a new phylogenetic analysis. An updated biostratigraphic framework correlates the Wachholz, Água Negra (São Martinho da Serra/RS) and Botucaraí Hill (Candelária/RS) sites based on their sample of sauropodomorphs. In addition, the record of Jachaleria in the Botucaraí Hill site, a dicynodont also known from early Norian deposits of Argentina, indicates an equivalent age to deposits bearing U. tolentioni. Accordingly, a more constrained age is proposed for the Água Negra site. This is important as the early Norian marks the transition from an epoch of low sauropodomorphs representativeness to a period of extreme abundance of the group in Early-to-Middle Mesozoic ecosystems.

New information on the postcranial skeleton of Massetognathus ochagaviae Barberena, 1981 (Eucynodontia, Traversodontidae), from the Middle Triassic of Southern Brazil

Abstract New postcranial remains of Massetognathus ochagaviae are described based on a new specimen collected at the Dinodontosaurus Assemblage Zone from the Middle Triassic of Southern Brazil. Several isolated teeth collected together with the postcranial skeleton allowed a taxonomic assignation of the specimen to M. ochagaviae. Its postcranial morphology is quite similar to Massetognathus pascuali, especially regarding the morphology of the transverse process of presacral vertebrae (i.e. laminar in the anterior most and rounded in the posterior most presacral vertebrae); humerus (i.e. the head is dorsally deflected with a ‘fan-shaped’ distal end a deltopectoral crest abruptly ending at the middle of shaft); and femur (with a bulbous and dorsomedially inclined femoral head, lesser trochanter which abruptly begins near the intertrochanteric fossa and extending up to the middle of the femoral shaft and the medial condyle more pronounced and ventrally projected than the lateral one). On the other hand, the clavicle of M. ochagaviae is less lateromedially elongated than in M. pascuali.

The pustulated temnospondyl revisited—a plagiosternine plagiosaurid from the Lower Triassic of Brazil

A recent contribution published in this journal (Dias-da-Silva and Ilha 2009) reported a dermal skull fragment indicating the presence of a putative plagiosauroid temnospondyl in the Lower Triassic Sanga do Cabrai Formation of the Parana Basin, Southern Brazil. The taxonomic assignation of this specimen was necessarily tentative as it was based on circumstantial evidence, specifically the presence of a dense pustular ornamentation over four partial dermal skull bones, consideration of the described taxa known to bear such ornamentation, and the stratigraphic and paleobiogeographic range of such taxa. Therefore, Dias-da-Silva and Ilha (2009) could not be totally certain about the plagiosauroid affinities of the new specimen and ascribed it to ?Plagiosauridae. It was particularly difficult to make a precise osteological identification of the specimen and six alternative osteological interpretations were made in comparison to both Gerrothorax and Peltobatrachus (see Dias-da-Silva and Ilha 2009: fig. 2). In spite of the poor taxonomic resolution, the new specimen raised interesting questions regarding the presence of plagiosauroid stereospondyls in western Gondwana, as well as their evolutionary patterns, biostratigraphic and paleobiogeographic implications. After Dias-da-Silva and Ilhas (2009) contribution was published, new data from Damiani et al. (2009) raised the possibility of narrowing down the taxonomic identity of the plagiosauroid from Brazil. Accordingly, this brief report provides a more precise taxonomic assignation for this material.