New Permian fauna from tropical Gondwana

Terrestrial vertebrates are first known to colonize high-latitude regions during the middle Permian (Guadalupian) about 270 million years ago, following the Pennsylvanian Gondwanan continental glaciation. However, despite over 150 years of study in these areas, the biogeographic origins of these rich communities of land-dwelling vertebrates remain obscure. Here we report on a new early Permian continental tetrapod fauna from South America in tropical Western Gondwana that sheds new light on patterns of tetrapod distribution. Northeastern Brazil hosted an extensive lacustrine system inhabited by a unique community of temnospondyl amphibians and reptiles that considerably expand the known temporal and geographic ranges of key subgroups. Our findings demonstrate that tetrapod groups common in later Permian and Triassic temperate communities were already present in tropical Gondwana by the early Permian (Cisuralian). This new fauna constitutes a new biogeographic province with North American affinities and clearly demonstrates that tetrapod dispersal into Gondwana was already underway at the beginning of the Permian.


Occiput.
47. Occipital condyles do not project beyond the posterior margin of the skull table [0]; condyles project beyond the posterior margin of the skull table [1]; condyles at approximately the same level of the posterior margin of the skull table [2].
48. Quadrate condyles well posterior to the occipital condyles [0]; in approximately the same transverse plane as the occipital condyles [1]; anterior to the occipital condyles [2]. 49. Ascending ramus of the pterygoid contacts the squamosal [0]; ascending ramus does not contact the squamosal creating an upper palatoquadrate fissure [1]. 50. Ascending ramus of the pterygoid thickened by an ascending column positioned towards its medial edge [1]; column absent [0]. 51. Ascending ramus of the pterygoid forms a continuous curve with the posterior edge of the quadrate ramus [0]; ascending ramus of the pterygoid arises from the dorsal surface of the pterygoid as a shallow curved lamina [1]; ascending ramus of the pterygoid arises from the dorsal surface as a shallow uncurved lamina [2]; ascending ramus of the pterygoid arises from the dorsal surface as a gently concave lamina which is also curved posteriorly in vertical section [3]; ascending ramus of the pterygoid arises from the dorsal surface as a gently concave lamina not curve posteriorly [4]. 52. Posterior face of quadrate ramus of the pterygoid lacking an oblique ridge [0]; a large, sharp lamina (oblique ridge) rises vertically from the occipital surface of the quadrate ramus at the level of the dorsalmost tip of the quadrate when see from behind and partially conceals the ascending ramus in occipital view [1]; the oblique ridge is a relatively low lamina that does not conceal the ascending ramus from behind [2]. 53. Post temporal fenestra markedly wider than deep [0]; about as wide as deep or deeper than wide [1]; post temporal fenestra reduced to small foramen or entirely closed [2]; post temporal fenestra slit-shaped [3]. 54. Quadratojugal foramen absent [0]; present on the occipital surface of the quadratojugal but occupying less than one third of the width of the surface [1]; present and occupying at least one-third of the surface width [2]. 55. Quadrate ramus of the pterygoid level with palate [0]; quadrate ramus slightly downturned [1]; quadrate ramus strongly downturned [2].

Ceratobranchials absent or unossified in adults [0]
; present in adults [1]. 57. Anterior palatal fossa not perforated [0]; anterior palatal fossa perforated to form an anterior palatal vacuity [1]. 58. Maxilla and vomer not in contact or in point contact [0]; maxilla and vomer forming a suture [1]. 59. Vomer contacts the palatine ramus of the pterygoid on the anterior edge of the interpterygoid vacuity [0]; palatine ramus of the pterygoid contacts the vomer on the anterolateral border of the interpterygoid vacuity [1]; palatine ramus of the pterygoid not in contact with the vomer [2]. 60. Palatine ramus of the pterygoid meets palatine on the lateral margin of interpterygoid vacuity [0]; pterygoid retracted so ectopterygoid is exposed in the interpterygoid vacuity and contributes to strut between interpterygoid and subtemporal vacuities [1]; pterygoid markedly retracted so ectopterygoid makes a large contribution to strut between interpterygoid and subtemporal vacuities [2]. corpus of the pterygoid forming a flat suture (basicranial suture) with the parasphenoid plate [2]; the basicranial suture extends anteroposteriorly along the lateral margins of the parasphenoid plate for more than the 50 % of the total length of the plate [3]. 66. Foramen for the internal carotid artery on the ventral surface of the parasphenoid plate [0]; foramen for the internal carotid located on the lateral side of the parasphenoid plate, posterior to the pterygoid articulation [1]; internal carotid and the palatine and intracranial branches pass through the dorsal surface of the parasphenoid plate, either leaving foramina where they pass below the surface or grooves where they lie upon it [2]; internal carotid artery passes along the ventral surface of the parasphenoid plate, leaving a groove, with a foramen on the lateral side of the parasphenoid at the base of the cultriform process, where the intracranial branch enters the parasphenoid [3]. 67. The width of the cultriform process of the parasphenoid at its midpoint is less than 10% of the length of the process (length of the cultriform process measured as the length between the anterior and posterior ends of the interpterygoid vacuities) [0]; width of cultriform process more than 10% of its length [1]. 68. Ventral surface of the cultriform process narrow and rounded [0]; gently convex [1]; with flat ventral surface and unexpanded anteriorly [2]; flat and expanded anteriorly between the vomers [3]; ventral surface of the cultriform process flat with a median keel [4]. 69. Cultriform process of the parasphenoid projects anteriorly between the vomers beyond the anterior border of the interpterygoid vacuities [0]; cultriform process ends at the level of or behind the anterior border of the interpterygoid vacuities [1]. 70. Vomerine depression or foramen just anterior to cultriform process of the parasphenoid absent [0]; present [1]; present as a vacuity [2]. 71. Prefenestral division of the palate (vomerine plate anterior to the interpterygoid vacuities) wider than long [0]; longer than wide [1]; approximately as wide as long [2]. 72. Posterior extension of the vomer present on the lateral border of the interpterygoid vacuity until the level of the palatine fangs [0]; posterior extension of the vomer absent [1]. 73. Ectopterygoid with enlarged tusks at its anterior end [0]; ectopterygoid tusks absent [1]. 74. Ectopterygoid with only one or two teeth [0]; ectopterygoid with a tooth row of more than three teeth [1]; ectopterygoid with two rows of teeth [2]; ectopterygoid without teeth [3]. 75. Absence of a tooth row behind the palatine tusks [0]; four to six palatine teeth [1]; more than seven palatine teeth [2]. 76. Medial margin of the choana without teeth [0]; medial margin of the choana with a row of teeth [1]. 77. Vomers without a row of teeth between the vomerine fangs [0]; with a straight tooth row running transversely between the vomerine fangs [1]; transverse vomerine tooth row 'V' shaped [2]; transverse vomerine tooth row anteriorly concave [3]; transverse vomerine tooth row anteriorly convex [4].  [1]; crista muscularis absent [2].
The composition of Dvinosauria obtained through the present analysis is very similar to that presented in previous cladistic studies 1,4,[18][19][20]  Dvinosaurus appeared in a more basal position compared to previous analyses and Eobrachyopidae and Tupilakosauridae resolved as sister groups. He also failed to recover a monophyeltic Trimerorhachide.
Our dataset is mainly focused on Dvinosauria and includes fewer taxa than those in the previous analyses 1,4,18-20 , but our results are essentially equivalent. Dvinosauria is recovered as a well supported (Decay index 5, see Fig. 3) monophyletic group, which includes two subclades: Trimerorhachidae plus Tupilakosauridae and its allies. The main difference between our analysis and those of other authors is the content and order of the taxa on the tupilakosaurid stem. In order to check the stability of the Brazilian taxa as representatives of the two main dvinosaur clades we ran our matrix with Perryella 18 included. Although previously considered a dvinosaur, it has recently been suggested that it is more probably a dissorophoid 20 . The inclusion of Perryella in our analysis did not change the position of Procuhy as the sister-taxon of Trimerorhachis or the position of Timonya at the base of the clade containing Tupilakosauridae and allied taxa. Perryella nested within the non-tupilakosaurid dvinosaurs and slightly altered the arrangement of taxa above Timonya: (Timonya + (Perryella + (Dvinosaurus + (Acroplous + (Isodectes + (Tupilakosauridae)))))).