Chroniosuchians were a clade of non-amniotic tetrapods known from the Guadalupian (middle Permian) to Late Triassic, mainly from Russia and China. The rarity of complete or articulated remains means that relatively little is known about this group in terms of its anatomy, palaeobiology, or evolutionary history. Based on a nearly complete skull with a left hemimandible, we describe the first chroniosuchian from Laos from rocks preserving the Permian-Triassic boundary in the Luang Prabang Basin, which is located on the tectonic Indochina Block. This specimen is referred to a new genus and species, Laosuchus naga, based on numerous diagnostic features, including an extremely reduced pineal foramen; absence of palatal dentition; well-developed transverse flange of the pterygoid that contacts the maxilla; internal crest on and above the dorsal side the palate; otic notch closed by the tabular horn and the posterior part of the squamosal, forming a continuous wall; thin and high ventromedial ridge on parasphenoid. A phylogenetic analysis of 51 characters and 25 taxa reveals a basal position for Laosuchus naga among Chroniosuchia. In addition, CT scan data reveal internal structures and provide new insights about the anatomy and palaeobiology of chroniosuchians. Laosuchus naga was likely amphibious and spent most of its time in water, rather than in terrestrial environments. As chroniosuchians are nonmarine tetrapods previously known on the North China Block, South China Block, and Laurussia, the occurrence of Laosuchus naga on the Indochina Block supports the hypothesis of physical connections between all these tectonic plates by the time of the Permo-Triassic boundary.

No abstract

No abstract

The Joggins Fossil Cliffs constitute an upper Carboniferous (Pennsylvanian) locality in Nova Scotia (Canada). This site, known for the rich record of fossils preserved in the palaeoenvironment in which they lived, sheds light on the late Carboniferous environment. More specifically, Joggins records one of the earliest Pennsylvanian ecosystems and is unique in preserving a rich diversity of terrestrial fauna compared with other Pennsylvanian communities, which mostly preserve aquatic fauna. For vertebrate palaeontology, the significance of Joggins lies in the discovery of the earliest amniotes (Hylonomus lyelli Dawson, Protoclepsydrops haplous Carroll, and Asaphestera platyris (Steen)) and the second earliest temnospondyl, Dendrerpeton (only Balanerpeton woodi Milner & Sequeira occurs earlier). Computed tomography of the most complete tetrapod specimen found at Joggins, the temnospondyl amphibian currently referred to Dendrysekos helogenes Steen, made accessible the internal anatomy and revealed previously obscured anatomical structures, including the stapes, scleral plates, and partial sphenethmoid. These newly accessible features enabled a redescription of this specimen. The resulting anatomical comparisons and phylogenetic analyses suggest that the genus Dendrysekos is a junior synonym of Dendrerpeton; the diagnostic characters previously distinguishing the two genera are considered to be instead a combination of ontogenetic and preservational parameters, and the two genera were not resolved as discrete. Additionally, the phylogenetic analyses show that the interrelationships between the main early temnospondyl groups (Edopoidea, Dvinosauria, Eryopoidea and Dissorophoidea) are neither robust nor well supported, due to the low number of shared derived characters.