Field of Science

Latest Literature - November 2009

Many recent and upcoming Triassic papers, mostly from Brazil.

Marynowski, L., and B. R. T. Simoneit. 2009. Widespread Upper Triassic to Lower Jurassic wildfire records from Poland:evidence from charcoal and pyrolytic polycyclic aromatic hydrocarbons. Palaios 24:785-798. DOI: 10.2110/palo.2009.p09-044r

Abstract - Laboratory tests indicate that 15% O2, instead of 12%, is required for the propagation of a widespread forest fire, a 3% increase from what was previously assumed. The presence of widespread wildfire records in the Upper Triassic and Lower Jurassic of Central Europe suggests that the lower limit for O2 during this time was at least 15%. Wildfire records are based on the co-occurrence of charcoal fragments and elevated concentrations of pyrolytic polycyclic aromatic hydrocarbons (PAHs). In all samples charcoal fragments are large to medium-sized and angular, suggesting that they were transported by rivers only short distances after charcoalification. Calculated combustion temperatures vary with stratigraphic position and average 295 377 uC, which is characteristic for ground or near-surface wildfires. The most extensive wildfires occurred in the earliest Jurassic and their intensities successively decreased with time. Average concentrations of the sum of pyrolytic PAHs for the lowermost Jurassic Zagaje Formation reached ~1253 mg/g total organic carbon (TOC), whereas for the Upper Triassic–Lower Jurassic Skłoby Formation they did not exceed ~16 mg/g TOC. Charcoal-bearing sequences were also characterized by the presence of phenyl-PAHs (Ph-PAHs) and oxygen-containing aromatic compounds. The dominance of the more stable Ph-PAH isomers in these immature to low-maturity sedimentary rocks supports their pyrolytic origin. The oxygenated PAHs may also be derived from combustion processes.

Veiga de Oliveira, T., Schultz, C. L., and M. B. Soares. 2009. A partial skeleton of Chiniquodon (Cynodontia, Chiniquodontidae) from the Brazilian Middle Triassic. Revista Brasileira de Paleontologia 12: 113-122. doi:10.4072/rbp.2009.2.02

Abstract - In this paper, we describe new postcranial remains of Chiniquodon cf. C. theotonicus, a chiniquodontid cynodont from the Therapsid Cenozone, from the Santa Maria Formation, Middle Triassic of Southern Brazil. In the described specimen are preserved almost all presacral vertebrae, the sacral vertebrae, an incomplete pelvic girdle, the left femur, and two metapodials. Some of these bones show slight differences relative to those already described for C. theotonicus, especially in the femur and in the pelvic girdle. Since the species can actually include the materials attributed to the genera Probelesodon (except from P. sanjuanensis) and Belesodon, however, these differences may represent normal ontogenetic variation in the species rather than being of taxonomically diagnostic value.

Stock Da-Rosa, A. A., Piniero, G., Dias-Da-Silva, S. Cisneros, J. C., Feltrin, F. F., and L. W. Neto. 2009. Bica São Tomé, a new fossiliferous site for the Lower Triassic of Southern Brazil. Revista Brasileira de Paleontologia 12:67-76. doi: 10.4072/rbp.2009.1.06

Abstract - Bica São Tomé, a new fossiliferous locality for the Sanga do Cabral Formation is described from southern Brazil. It consists in orange and reddish fine sandstones with sandy and calcareous concretions and intercalated fossiliferous intraformational conglomerates. This Lower Triassic locality is particularly interesting due to very well preserved and partially articulated specimens of continental tetrapods, an unusual feature in this unit, since the fossils in other outcrops are mostly disarticulated. Temnospondyl amphibians, procolophonoid and probable archosauromorph reptiles have been found in this new Lower Triassic locality. Further studies in this locality will allow the complement and a better acknowledged of the affinities of the Sanga do Cabral fauna with those from the basal Triassic Gondwanan and Laurasian.

De Amorim Arantes, B., Soares, M. B., and C. L. Schultz. 2009. Clevosaurus brasiliensis (Lepidosauria, Sphenodontia) from the Upper Triassic of Rio Grande do sul: post-cranial anatomy and phylogenetic relationships.Revista Brasileira de Paleontologia 12: 43-54. doi:10.4072/rbp.2009.1.04

Abstract - Sphenodontia is the most abundant taxon from the Caturrita Formation (Upper Triassic) paleofauna, which is composed predominantly by microvertebrates. However, only two syncrania (UFRGS-PV0613T e UFRGS-PV0748T) were formally described by Bonaparte & Sues in 2006 so far. Based on these materials, a new species Clevosaurus brasiliensis, was erected and the Clevosauridae family was formalized being composed by Clevosaurus, Brachyrhinodon and Polysphenodon. This work presents an anatomic description of the post-cranial skeleton of C. brasiliensis based on more than 25 specimens. Among the materials, dorsal, sacral and caudal vertebrae, femora, tibiae and fibulae were identified. Generally, the post-cranial skeleton presents the typical features of the sphenodontians, and the morphology of the bones is very similar to those of other species of Clevosaurus (e.g. C. hudsoni, C. bairdi). However, the adult individuals of the Brazilian species are notably smaller than most of the other sphenodontians. The anatomic information obtained was used, together with the cranial characters, in a phylogenetic analysis to establish the position of C. brasiliensis in the Sphenodontia clade. The data matrix was built with 18 taxa and 67 characters. The resulting cladogram confirms the close relationship between the Brazilian species with Clevosaurus hudsoni and attests the consistency of the Clevosauridae family.

Bardola, T. P., Schmidt, I. D., Sommer, M. G., and C. L. Schultz. 2009. Ginkgophyta wood in petrified forest of the Upper Triassic from Rio Grande do Sul, Brazil. Revista Brasileira de Paleontologia 12:139-148. doi:10.4072/rbp.2009.2.04

Abstract - The anatomic analysis of an assemblage of silicified fossil wood fragments from the Santa Maria Formation, southern Paraná Basin, Brazil, led to the identification of parameters compatible with the morphospecies Baieroxylon cicatricum, registered and described here for the first time for the Brazilian Gondwana. The secondary wood is homogeneous, picnoxylic and characterized by the presence of growth zones. In the radial walls of the tracheids there are bordered pits in a predominantly uniserial arrangement. Typical spiral thickening is present in longitudinal radial and tangential sections. The rays are in a uniserial arrangement and homogeneous. The cross-field pits, one to four per crossfield, are inconspicuous, circular, small and randomly arranged. Phloem and cortex are unpreserved. A common pattern found on the external surface of the wood fragments corresponds to simple eye-shaped scars, which would correspond to branch connections, and hollow, double and triple eye-shaped scars in alternating arrangement, which would correspond to leaf insertions.

Cabreira, S. F., and J. C. Cisneros. in press. Tooth histology of the parareptile Soturnia caliodon from the Upper Triassic of Rio Grande do Sul, Brazil. Acta Palaeontologica Polonica in press.

Abstract - A histological analysis of the dentition of the small procolophonid parareptile Soturnia caliodon reveals detailed information concerning tooth implantation and replacement for this taxon. The presence of acrodont tooth implantation is verified, which contradicts current models for procolophonid dentition. A heterogeneous enamel layer, that reaches large thickness on the cusps, and a broad secondary dentine are also recorded. These structures provide a very stable occlusal morphology that extends the useful life of the teeth. During the process of replacement, old teeth were not pushed out but reabsorbed. The evidence indicates that Soturnia caliodon had a very low rate of tooth replacement which constitutes a valuable adaptation for its high-fibre herbivorous niche.

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