A new gomphodont cynodont (Traversodontidae) from the Middle–Late Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence,Brazil

The tetrapod faunas from the terrestrial Middle–Late Triassic basins of Africa and South America are among the richest in the world, especially in non‐mammalian cynodonts. Despite the great abundance of cynodont specimens found in these basins, there are few known taxa that exhibit interbasinal distributions. Here we describe a new species of traversodontid cynodont of the genus Scalenodon from the Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence, from the state of Rio Grande do Sul, Brazil. Scalenodon ribeiroae sp. nov. is based on a partial skull that possesses a combination of features not observed in any other South American traversodontid: ellipsoid upper postcanines with the transverse crest formed by three cusps, lacking a mesiobuccal accessory cusp, and with lingual cusp projected lingually creating a concave lingual surface on the upper postcanines; the paracanine fossa is positioned medially to the upper canine, and jugal lacks a suborbital process. A phylogenetic analysis places the new taxon in a basal position within the Family Traversodontidae, with the African Scalenodon angustifrons as sister‐taxon. The new specimen of Scalenodon represents the first record of this genus outside of the Manda Beds of Tanzania, and reinforces the biostratigraphical and biogeographical connection between Gondwanan Middle–Late Triassic tetrapod faunas. Although recent advances have been made, our current knowledge of these faunas is limited by the lack of absolute dates for most units and by uncertainties in the taxonomy and stratigraphical provenance of key fossils.     

A new trirachodontid cynodont from the lower levels of the Burgersdorp Formation (Lower Triassic) of the Beaufort Group, South Africa and the cladistic relationships of Gondwanan gomphodonts

We describe a new trirachodontid cynodont from the base of the Burgersdorp Formation (Subzone A fauna of the Cynognathus Assemblage Zone), of the South African Karoo Basin. Langbergia modisei gen. et sp. nov. is characterized by circular to ovoid in outline upper postcanines and the absence of a maxillary platform lateral to the postcanine series. Apart from the new taxon, we recognize two other species of this family in the Cynognathus Assemblage Zone: Trirachodon berryi and Cricodon metabolus , the latter also represented in the Tanzanian Manda Formation. A phylogenetic analysis of gomphodont cynodonts was conducted using a data matrix of 43 craniodental characters and 18 terminals. Trirachodontidae appears as a monophyletic assemblage, with Langbergia appearing as the sister taxon of Cricodon . The monophyly of trirachodontids is weakly supported, however, with one extra step breaking it. Traversodontid cynodont relationships were also inspected and compared with a recent phylogeny proposed for this group. Considering the resulting phylogeny and the sudden appearance and diversification of Cynognathia representatives, the origin of basal Cynognathia (i.e. Cynognathus , Diademodon , and trirachodontids) is suggested to predate their first appearance in the fossil record.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 147 , 383–413.     

The Chañares Formation: a window to a Middle Triassic tetrapod community

The Chañares Formation is known worldwide for its diverse and well‐preserved Ladinian non‐marine tetrapod assemblage, including a wide variety of archosauriform reptiles (proterochampsids, early offshoots of the crocodilian line and dinosaurian precursors) and synapsids represented by dicynodonts and cynodonts. This tetrapod record offers an opportunity to evaluate, within a taphonomic context, the palaeoecology of this Middle Triassic fauna. The taphonomic analysis of the Chañares assemblage, under precise stratigraphical control, indicates that it is a good representation of the original faunal composition allowing us to address the palaeoecological interactions between its components. Mass estimations and morphology‐based palaeobiological inferences of Chañares tetrapods are used to reconstruct the trophic structure of the community. Chañares tetrapod fauna was numerically dominated by middle‐sized herbivorous and small faunivorous cynodonts, whereas middle‐sized faunivorous cynodonts and large dicynodonts were less common. In contrast to the therapsids, which show a low species‐richness and high abundance, the archosauriforms are less abundant, but are the most taxonomically diverse group. The large paracrocodylomorphs (estimated body masses between 350 and 500 kg) are identified as the top predators of the community, and the traversodontid cynodonts and dicynodonts (estimated body masses reaching approximately 43 and 360 kg, respectively) are indentified as the base herbivores of the trophic pyramid. We conclude that the worldwide faunal composition in the Ladinian reveals two continental assemblages: an eastern Laurasian assemblage dominated by temnospondyl amphibians; and a western Gondwanan assemblage dominated by therapsids but including a wide diversity of archosauriforms.     

Osteohistology of the non-mammaliaform traversodontids Protuberum cabralense and Exaeretodon riograndensis from southern Brazil

Abstract

The current study presents a detailed analysis of the osteohistology of the Triassic non-mammaliaform traversodontid cynodonts Protuberum cabralense and Exaeretodon riograndesis. The data provided here adds new information on the growth patterns of South American traversodontids. A single subadult individual of P. cabralense revealed bone tissues comprising uninterrupted fibrolamellar bone. Patches of slower growing lamellar bone at the periphery of one of the elements suggests a transition to overall slower growth in later ontogeny. The bone tissues of E. riograndensis also exhibit uninterrupted fibrolamellar bone during early ontogeny, but growth became cyclical from mid-ontogeny. The early rapid, sustained growth observed in these taxa is similar to that seen in other traversodontids, and may be related to the achievement of large body size in the derived members of the clade.     

New traversodontid (Therapsida: Cynodontia) teeth from the Upper Triassic of Habay-la-Vieille (southern Belgium)

Dwarf traversodontids (Therapsida, Cynodontia) are rare components of Late Triassic terrestrial faunas from western Europe.Habayia halbardieri n. gen., n. sp., described and discussed in the present paper, is based on one isolated upper postcanine from the Rhaetian of Habay-la-Vieille (southern Belgium). Another tiny tooth from the same locality is tentatively identified as a traversodontid lower postcanine. Dwarf cynodonts were well diversified in western Europe at the end of the Triassic. Their radiation, coupled with the sudden origin of mammals, corresponds to the development of the Rhaetian transgression which transformed western Europe into an archipelago and led to a reorganization of the terrestrial faunas.     

A new phylogenetic classification for the gymnophthalmid genera Cercosaura , Pantodactylus and Prionodactylus (Reptilia: Squamata)

Because of the poor state of knowledge of many of the gymnophthalmid genera, systematic revision is necessary to render the classification consistent with evolutionary history. To that end, I conducted a review of the species of three genera of the Cercosaurinae which appear to form a monophyletic group: Cercosaura , Pantodactylus , and Prionodactylus . Phylogenetic analysis of 61 morphological characters was conducted after specimens of all species were examined to evaluate the composition of each taxon. The phylogenetic reconstruction suggested that the genus Prionodactylus was paraphyletic. A new phylogenetic classification is proposed that synonymizes Pantodactylus and Prionodactylus with Cercosaura. Cercosaura is redefined to include 11 species and seven subspecies. A key is provided to distinguish among species.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society, 2003, 137 , 101−115.     

Origin and relationships of the Ictidosauria to non-mammalian cynodonts and mammals

Abstract

Ictidosaurian genera are allocated to two families, Tritheledontidae and Therioherpetidae. This paper provides a diagnosis for Ictidosauria. The previously named family Brasilodontidae is shown to be a junior synonym of a family, Therioherpetidae. It is concluded that Ictidosauria originated from Late Permian procynosuchid non-mammalian cynodonts rather than from Middle Triassic probainognathid non-mammalian cynodonts. The structure of the skull and jaws of a derived traversodontid Ischignathus sudamericanus from the early Late Triassic of Argentina supports an earlier view that tritylodontids are more closely related to traversodontid than probainognathid non-mammalian cynodonts. Tritylodontids should not be included in Ictidosauria, nor should they considered to be a sister group to mammaliaforms.     

Phylogenetic analysis of Russian Permian dicynodonts (Therapsida: Anomodontia): implications for Permian biostratigraphy and Pangaean biogeography

Dicynodont therapsids have been known from the Upper Permian of Eastern Europe since the beginning of the twentieth century, but the phylogenetic relationships of these taxa have not been examined cladistically. Here we present the results of a phylogenetic analysis that includes eight Permian dicynodonts from Russia as well as 18 taxa best known from southern Africa. Our results do not conflict with much of the established picture of Permian dicynodont phylogeny, but are consistent with several novel hypotheses. Most importantly, our analysis suggests that the genus Dicynodon is paraphyletic, and we question its use in correlating widely separated basins. However, we cannot strongly reject a monophyletic Dicynodon . Our results also indicate that the closest Permian relatives of Kannemeyeria lived in Russia, suggesting a Laurasian origin for the lineage that includes this important Triassic taxon. The phylogeny presented here also suggests a Laurasian origin for several other dicynodont clades, but a Gondwanan origin is equally likely given the data at hand. Regardless of where these groups originated, there appears to be some endemism among Late Permian dicynodont faunas. Although our understanding of dicynodont phylogeny is improving, this study emphasizes the disparity in sampling of the dicynodont record between Gondwana and Laurasia and the need for a large scale phylogenetic analysis of Permian and Triassic dicynodonts.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society, 2003, 139 , 157−212.     

The oldest cynodont: new clues on the origin and early diversification of the Cynodontia

Early mammaliaforms and their extinct relatives, nonmammaliaform cynodonts, have long been the focus of intense research in attempting to unravel how and when major changes toward mammalness occurred. The earliest well-known representatives of cynodonts are latest Late Permian in age. Here, we describe Charassognathus gracilis gen. et sp. nov. , from the early Late Permian of South Africa, representing the oldest cynodont yet found. This specimen displays a notch on the dentary in the same location as the base of the masseteric fossa in the basal cynodonts Procynosuchus and Dvinia , and represents the first indication in theriodonts of an invasion of occlusal musculature onto the dentary. A phylogenetic analysis of seven therocephalians and ten non-mammaliaform cynodonts and equally weighted characters resulted in nine most parsimonious trees, the strict consensus of which shows a basal polytomy in cynodonts, including Charassognathus , Dvinia , Procynosuchus and a clade including the remaining cynodonts. The basal polytomy in the majority rule consensus tree is reduced, as Procynosuchus and Dvinia form a clade. One most parsimonious tree, from an analysis using implied weights, positions Charassognathus as the most basal cynodont. This result implies that the Cynodontia initially diversified in Permian Gondwana, in what is now southern Africa.  © 2007 The Linnean Society of London, Zoological Journal of the Linnean Society , 2007, 149 , 477–492.     

Molecular systematics of North American phoxinin genera (Actinopterygii: Cyprinidae) inferred from mitochondrial 12S and 16S ribosomal RNA sequences

The cyprinid fish fauna of North America is relatively large, with approximately 300 species, and all but one of these are considered phoxinins. The phylogenetic relationships of the North American phoxinins continue to pose difficulties for systematists. Results of morphological analyses are not consistent owing to differences interpreting and coding characters. Herein, we present phylogenetic analyses of mitochondrial 12S and 16S ribosomal RNA sequence data for representatives of nearly all genera of North American phoxinins. The data were analysed using parsimony, weighted parsimony, maximum likelihood and bayesian analyses. Results from weighted parsimony, likelihood and the bayesian analysis are largely consistent as they all account for differing substitution rates between transitions and transversions. Several major clades within the fauna can be recognized and are strongly supported by all analyses. These include the western clade, creek chub–plagopterin clade and the open posterior myodome clade. The shiner clade is nested in the open posterior myodome clade and is the most species-rich clade of North American phoxinins. Relationships within this clade were not well resolved by our analyses. This may reflect the inability of the mitochondrial RNA genes to resolve recent speciation events or taxon sampling within the shiner clade.  © 2003 The Linnean Society of London, Zoological Journal of the Linnean Society , 2003, 139 , 63–80.     

A new stereospondyl from the German Middle Triassic, and the origin of the Metoposauridae

Recent finds of well-preserved temnospondyl skeletons from the Lower Keuper (Ladinian, Middle Triassic) in southern Germany are assigned to a new genus and species, Callistomordax kugleri . This taxon is characterized by the following autapomorphies: (1) wide unpaired frontal; (2) vomerine fangs greatly enlarged to occupy entire width of element; (3) intercentra elongated and massive, anterior face being convex; (4) humerus semilunar with enlarged deltopectoral crest; (5) cleithrum strongly curved and bow-shaped; (6) trunk extremely elongated to reach three times the length of the skull. Callistomordax shares with the Metoposauridae the pattern of dermal ornamentation, the proportion of both posterior skull table and snout, the position of the lacrimal, the morphology of the basicranial region, and the structure of the clavicle and interclavicle. Phylogenetic analysis suggests Callistomordax to be the sister taxon of the Metoposauridae, nested within a grade formed by various trematosaurian taxa. In this assemblage, Lyrocephaliscus and a clade formed by Almasaurus , Rileymillerus , Callistomordax , and the Metoposauridae are sister taxa. In all variants of the cladistic analysis, Callistomordax and the Metoposauridae form immediate sister groups. According to the present findings, neither plagiosaurids nor brachyopoids and rhytidosteids are closely related to this 'trematosaurian' monophylum, although these taxa share a range of homoplasies.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 79–113.     

Osteology of Rauisuchus tiradentes from the Late Triassic (Carnian) Santa Maria Formation of Brazil,and its implications for rauisuchid anatomy and phylogeny

As the eponymous type species for rauisuchians, Rauisuchus tiradentes von Huene, 1938 represents an important but inadequately known specimen. The revision of the type material from the Upper Triassic (Carnian) Santa Maria Formation of Brazil reveals new anatomical data and previously unrecognised characters, including three new possible autapomorphies: a knob‐like thickening on the base of the posterior process of the premaxilla; short and ventrally keeled cervicals lacking postzygodiapophyseal laminae; and mid‐caudal vertebrae with an accessory neural spine and a postspinal lamina. Several elements are re‐identified, including a postorbital (originally identified as postfrontal) and a pterygoid (originally identified as a prefrontal), and additional material from a secondary fossil site, originally assigned to R. tiradentes, including a left ilium, is excluded. Based on the recovered information and new morphological data, the systematic position of R. tiradentes is tested in a comparison of two phylogenetic reanalyses. Both analyses differ in respect to the phylogenetic position of R. tiradentes, and recover ‘rauisuchians’ as a paraphyletic assemblage of non‐crocodylomoprh archosaurs. © 2014 The Linnean Society of London     

On the systematic status of the desert plated lizard (Angolosaurus skoogi): phylogenetic inference from DNA sequence analysis of the African Gerrhosauridae

The desert plated lizard ( Angolosaurus skoogi ), a 'sand sea' endemic of the northern Namib Desert, exhibits remarkable morphological convergence with other dune-dwelling lizards worldwide. This distinct ecomorphic condition sets Angolosaurus apart from the remaining genera in the family Gerrhosauridae. Indeed, a morphological phylogeny addressing generic relationships within the Cordyliformes (Cordylidae + Gerrhosauridae) identified Angolosaurus as the earliest diverging taxon among African gerrhosaurids. We re-evaluated the basal status of Angolosaurus , conducting a molecular phylogenetic analysis of the African and Madagascan gerrhosaurid genera. Our survey involved a comprehensive species-level comparison among the four nominal genera of mainland Africa ( Angolosaurus , Cordylosaurus , Tetradactylus and Gerrhosaurus ). Mitochondrial DNA sequence data from the cytochrome b , ND2, 12S and 16S rRNA genes were combined for analysis using both parsimony and maximum likelihood procedures. In contrast to the morphological hypothesis, our results do not depict Angolosaurus as the sister taxon to other African gerrhosaurids. Rather, the molecular analyses consistently place Angolosaurus within Gerrhosaurus , rendering the latter genus paraphyletic.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 78 , 253–261.     

Isoetes fluitans sp. nov.: the identity of Spanish plants of 'I. longissimum'

Recent revision of North African specimens of Isoetes velata A. Braun and the closely related taxon I. longissimum Bory, together with Spanish material conventionally designated I. longissimum , suggests that the Spanish specimens constitute a new species, I. fluitans . This is described and illustrated. The North African taxon I. longissimum is probably not specifically distinct from I. velata .  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 146 , 231–236.     

Minuartia graminifolia (Caryophyllaceae), a south-east European species

A re-evaluation of Minuartia graminifolia has been undertaken based on comparative morphological studies. M. graminifolia subsp. rosani (an endemic of the south-central Apennines and Sicily) and subsp. hungarica (an endemic of the Banat region of Romania) are accepted infraspecific taxa. M. graminifolia subsp. hungarica is lectotypified. M. graminifolia subsp. clandestina is confirmed for Italy; the taxon is neotypified. The type subspecies is considered an endemic to the east-central Alps. Keys to the species of Minuartia ser. Graminifoliae and to the subspecies of M. graminifolia are provided.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 143 , 419–432.