Átila Augusto Stock Da-Rosa

Discovery of a 240 million year old nematode parasite egg in a cynodont coprolite sheds light on the early origin of pinworms in vertebrates

BackgroundWe report the discovery of a nematode parasite egg (Nemata: Oxyurida) from a coprolite closely associated with the remains of several species of Cynodontia, dated to 240 million years old. This finding is particularly significant because this is the oldest record of an oxyurid nematode yet discovered, and because the cynodonts are considered a stem-group of the mammals.MethodsWe extracted material from a fully mineralized coprolite by both scraping the surface, and removing fragments from its interior with clean dental instruments used a single time. A single drop of glycerol from a new vial was added as a clearing reagent. Each slide was sealed with wax and examined with an optical microscope at 100× to 400× magnification.ResultsFrom one coprolite, 550 slides were examined; from 275 of these slides, sediment was examined that was scraped from the surface of the coprolite, and from the other 275 slides, material was examined that was extracted from the interior of the coprolite. All microscopic structures encountered were photographed, measured, and identified when possible.ConclusionsFrom the coprolite examined, we discovered an egg representing a new species of pinworm that, based on the egg structure, clearly places it in the family Heteroxynematidae. Nematodes of the order Oxyurida have very constrained life-histories, occurring only in animals that are not strictly carnivorous and also ingest large amounts of plant material. This fact enabled us to determine which species of cynodont, from several collected at the site in Brazil, are most likely the depositors of the coprolite, and therefore were the putative host of the parasite.

A new ascarid species in cynodont coprolite dated of 240 million years

Cynodonts represent the transition from reptiles to mammals. They are classified as synapsids, or tetrapod animals with mammalian characteristics. We present here the finding of helminth eggs in a coprolite identified as of cynodont origin dated of nearly 240 million years. Microscopy revealed the presence of very well preserved intestinal parasite eggs. Up to now we identified an ascarid egg by morphological characteristics. Based on a previous description of the new genus Ascarites Poinar Jr and Boucot 2006 in coprolites of iguanodons from Belgium, we propose a new species, Ascarites rufferi n.sp. in cynodonts, a host that inhabited the Southern Region of Brazil in the Triassic period.

The African cynodont Aleodon (Cynodontia, Probainognathia) in the Triassic of southern Brazil and its biostratigraphic significance

In this contribution we report the first occurrence of the enigmatic African probainognathian genus Aleodon in the Middle-early Late Triassic of several localities from the state of Rio Grande do Sul in southern Brazil. Aleodon is unusual among early probainognathians in having transversely-expanded postcanine teeth, similar to those of gomphodont cynognathians. This genus was previously known from the Manda Beds of Tanzania and the upper Omingonde Formation of Namibia. The Brazilian record of this genus is based upon multiple specimens representing different ontogenetic stages, including three that were previously referred to the sectorial-toothed probainognathian Chiniquodon theotonicus. We propose a new species of Aleodon (A. cromptoni sp. nov.) based on the specimens from Brazil. Additionally, we tentatively refer one specimen from the upper Omingonde Formation of Namibia to this new taxon, strengthening biostratigraphic correlations between these strata. Inclusion of A. cromptoni in a phylogenetic analysis of eucynodonts recovers it as the sister-taxon of A. brachyrhamphus within the family Chiniquodontidae. The discovery of numerous specimens of Aleodon among the supposedly monospecific Chiniquodon samples of Brazil raises concerns about chiniquodontid alpha taxonomy, particularly given the extremely broad geographic distribution of Chiniquodon. The discovery of Brazilian Aleodon and new records of the traversodontid Luangwa supports the hypothesis that at least two subzones can be recognized in the Dinodontosaurus Assemblage Zone.

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.

A capitosauroid from the Lower Triassic of South America (Sanga do Cabral Supersequence: Paraná Basin), its phylogenetic relationships and biostratigraphic implications

Abstract Surviving through the end-Permian mass extinction, stereospondyls reemerged reaching a widespread distribution during the Early Triassic. A well representative lineage of this clade, Capitosauroidea, became worldwide abundant from Early to Late Triassic, in which their first undoubtful representatives were recovered from Lower Triassic deposits. Here, we describe a new capitosauroid, Tomeia witecki gen. et sp. nov., from the Sanga do Cabral Supersequence (Paraná Basin). Although relatively incomplete, the material presents a particular combination of early and late-diverging capitosauroid characters. Supporting Tomeia witecki as a new capitosauroid, our phylogenetic analysis placed the taxon as part of a clade that comprises only Early Triassic capitosauroids, specifically as the sister-taxon of the madagascarian Edingerella madagascariensis and close to Watsonisuchus spp., from Australia, South Africa and Madagascar. The status of Tomeia witecki as a new capitosauroid from western Gondwana supports a continuous record of the Stereospondyl lineage, since their first appearance during the Middle Permian in this supercontinent. Additionally, the temporal range of the Sanga do Cabral Supersequence during the Early Triassic was specifically reinforced as Olenekian, mainly based on the overall faunal content previously reported to this unit, associated with the known temporal distribution from those taxa phylogenetically closer to Tomeia witecki. http://zoobank.org/urn:lsid:zoobank.org:pub:7AA9F874-BED5-4A99-B098-B50656E706C1

ARCHOSAUROMORPH REMAINS FROM THE TARJADOS FORMATION (EARLY–MIDDLE TRIASSIC, NW ARGENTINA)

Abstract. The Agua de la Peña Group of the Ischigualasto-Villa Unión Basin (northwestern Argentina) documents the evolution of archosauromorph assemblages in western Gondwana during the late Middle and Late Triassic. However, the South American archosauromorph record in the aftermath of the Permo/Triassic mass extinction (Early—early Middle Triassic) is remarkably scarce and restricted to isolated bones. Here, we describe a recently collected isolated second sacral vertebra and rib that represents one of the few fossils known from the Lower—Middle Triassic Tarjados Formation, the unit that underlies the Agua de la Peña Group. This specimen is identified as an archosauromorph because of the presence of a non-notochordal vertebra and a bifurcated distal end of the second sacral rib. A quantitative phylogenetic analysis places the new specimen as an archosauromorph more derived than protorosaurs. In particular, this specimen resembles Pamelaria, Prolacerta and early rhynchosaurs in the presence of a squared posterior projection of the bifurcated second sacral rib. The new specimen represents the first body fossil of a diapsid formally described in the Tarjados Formation and the oldest member of the group in the Ischigualasto-Villa Unión Basin. As a result, this specimen increases the high-level taxonomic richness of Archosauromorpha in South America in the aftermath of the Permo/ Triassic mass extinction.

Osteology of the first skull of Aetosauroides scagliai Casamiquela 1960 (Archosauria: Aetosauria) from the Upper Triassic of southern Brazil (Hyperodapedon Assemblage Zone) and its phylogenetic importance

Aetosauria, which includes 30 species, is a diverse group of armored pseudosuchian archosaurs restricted to Upper Triassic beds. Three species occur in Brazil, and one of these, Aetosauroides scagliai Casamiquela, 1960, also occurs in Argentina. The specimen UFSM 11505, found at Faixa Nova–Cerrito I Outcrop, Santa Maria Formation (Hyperodapedon Assemblage Zone), Santa Maria, Rio Grande do Sul State, Brazil, is here referred to as Aetosauroides scagliai. This specimen preserves most of the skull with both hemimandibles in association with most of the postcranium, thus representing one of the most complete aetosaur skeletons found in Brazil. The premaxilla, one of the key elements of the cranial morphology of aetosaurs, along with the posterior portion of the mandible, was not described until now for A. scagliai. In contrast to the typothoracinae aetosaurs, the premaxilla of UFSM 11505 presents a shovel-shaped tip, but it is not as prominent as the lateral expansion of desmatosuchian aetosaurs, including both species of Stagonolepis, S. robertsoni Agassiz, 1844 and S. olenkae Sulej, 2010. The retroarticular process of the mandible is elongate and not tall, as in Stenomity huangae Small & Martz, 2013 and other typothoracinae aetosaurs. Unlike previous descriptions of A. scagliai, the maxillary teeth are recurved ziphodont-like with serrations on the entire length of both margins. Premaxillary teeth are also present, being less recurved than the maxillary teeth and cylindrical. We recovered Aetosauroides scagliai as the most basal taxon within Aetosauria, like previous phylogenetic analyses. Furthermore, our analyses reinforce that recurved and unconstricted maxillary teeth, the shovel-shaped premaxilla and the presence of a tuber on the surangular are plesiomorphic features of Aetosauria.