Laurasian Origin Research Articles

Miocene Dispersal Drives Island Radiations in the Palm Tribe Trachycarpeae (Arecaceae)

The study of three island groups of the palm tribe Trachycarpeae (Arecaceae/Palmae) permits both the analysis of each independent radiation and comparisons across the tribe to address general processes that drive island diversification. Phylogenetic relationships of Trachycarpeae were inferred from three plastid and three low-copy nuclear genes. The incongruent topological position of Brahea in CISP5 was hypothesized to be caused by a gene duplication event and was addressed using uninode coding. The resulting phylogenetic trees were well-resolved and the genera were all highly supported except for Johannesteijsmannia and Serenoa. Divergence time analysis estimated the stem of the tribe to be approximately 86 Ma and the crown to be 38 Ma, indicating that significant extinction may have occurred along this branch. Historical biogeographic analysis suggested that Trachycarpeae are of southern North American, Central American, or Caribbean origin and supports previous hypotheses of a Laurasian origin. The biogeography and disjunctions within the tribe were interpreted with respect to divergence times, the fossil record, and geological factors such as the formation of the Greater Antilles--Aves Ridge, the Bering and the North Atlantic land bridges, tectonic movement in Southeast Asia, climatic shifts between the Eocene and Pliocene, and volcanism in the Pacific basin. In considering the three major island radiations within Trachycarpeae, Miocene dispersal appears to have been the driving force in allopatric speciation and is highlighted here as an emerging pattern across the tree of life.

First evidence of fossil Cryosophileae (Arecaceae) outside the Americas (early Oligocene and late Miocene of France): Anatomy, palaeobiogeography and evolutionary implications

A recent anatomical study of living palm stems shows that the five palm subfamilies and their tribes have useful identification characters. This study intends to show that identification of fossil palm stems from anatomical descriptors is potentially possible at the tribe level. As a concrete application, we study the holotype of Palmoxylon vestitum (Saporta) Stenzel and some other stems of two localities: five fossil palm stems from the lower Oligocene of Apt (Vaucluse, France) and two from the upper Miocene of Castellane (Alpes-de-Haute-Provence, France). These seven palm stems belong to the same species (P. vestitum). With a referential of living stems, we improve the identification of this species within the palm family. This species is a Cryosophileae (Coryphoideae) and the closer living genus is Coccothrinax Sargent This discovery has important consequences on the history of the palm family. Indeed, it is the first record of this tribe outside the Americas. Currently the living Cryosophileae are mainly restricted to Central America and this identification provides evidence for a Laurasian origin of this tribe, during the early Eocene as for its sister tribe (Sabaleae). Furthermore, the ecology of this tribe and of this genus gives more information about the palaeoclimatical conditions of these two localities (dry area to subtropical dry forest).

On the Affinities ofTetraceratops insignis, an Early Permian Synapsid

The affinities of the Early Permian synapsid Tetraceratops insignis have been reevaluated several times since the early 20th century, being considered as an eothyridid, a sphenacodontid, or a therapsid. This controversy continues into the 21st century, with recently raised doubts about the interpretation of Tetraceratops as the oldest known therapsid, a hypothesis supported by the only redescription of this fossil in the second half of the 20th century. Our study examines the arguments proposed to refute therapsid affinities, and concludes that Tetraceratops indeed is the sister-group of all other known therapsids. The most recently published phylogenetic data matrix that includes Tetraceratops fails to confirm its therapsid affinities. However, adding seven characters to that matrix leads to the conclusion that Tetraceratops is the basal-most and oldest therapsid. The recent suggestion of a Laurasian origin of therapsids appears poorly supported; too few data are available on the distribution of Permian ...

Mitochondrial genomes of acrodont lizards: timing of gene rearrangements and phylogenetic and biogeographic implications

BackgroundAcrodonta consists of Agamidae and Chamaeleonidae that have the characteristic acrodont dentition. These two families and Iguanidae sensu lato are members of infraorder Iguania. Phylogenetic relationships and historical biogeography of iguanian lizards still remain to be elucidated in spite of a number of morphological and molecular studies. This issue was addressed by sequencing complete mitochondrial genomes from 10 species that represent major lineages of acrodont lizards. This study also provided a good opportunity to compare molecular evolutionary modes of mitogenomes among different iguanian lineages.ResultsAcrodontan mitogenomes were found to be less conservative than iguanid counterparts with respect to gene arrangement features and rates of sequence evolution. Phylogenetic relationships were constructed with the mitogenomic sequence data and timing of gene rearrangements was inferred on it. The result suggested highly lineage-specific occurrence of several gene rearrangements, except for the translocation of the tRNAPro gene from the 5' to 3' side of the control region, which likely occurred independently in both agamine and chamaeleonid lineages. Phylogenetic analyses strongly suggested the monophyly of Agamidae in relation to Chamaeleonidae and the non-monophyly of traditional genus Chamaeleo within Chamaeleonidae. Uromastyx and Brookesia were suggested to be the earliest shoot-off of Agamidae and Chamaeleonidae, respectively. Together with the results of relaxed-clock dating analyses, our molecular phylogeny was used to infer the origin of Acrodonta and historical biogeography of its descendant lineages. Our molecular data favored Gondwanan origin of Acrodonta, vicariant divergence of Agamidae and Chamaeleonidae in the drifting India-Madagascar landmass, and migration of the Agamidae to Eurasia with the Indian subcontinent, although Laurasian origin of Acrodonta was not strictly ruled out.ConclusionsWe detected distinct modes of mitogenomic evolution among iguanian families. Agamidae was highlighted in including a number of lineage-specific mitochondrial gene rearrangements. The mitogenomic data provided a certain level of resolution in reconstructing acrodontan phylogeny, although there still remain ambiguous relationships. Our biogeographic implications shed a light on the previous hypothesis of Gondwanan origin of Acrodonta by adding some new evidence and concreteness.

<p class="HeadingRunIn"><strong>The Late Jurassic fossil from Asian ancestory to a recent genus, <em>Nothotrichocera</em> Alexander 1926 (Diptera: Trichoceridae)</strong></p>

A new trichoceriid species of a fossil genus Zherikhinina Krzeminska, Krzeminski & Dahl 2009 is described from Shar Teg, a well known Upper Jurassic locality in Mongolia. Its plausible ancestry to a Recent genus Nothotrichocera Alexander 1926 supports the Laurasian origin of this latter genus, now of strictly circum-Antarctic distribution.

Taxonomy and systematics of the genus Pinus based on morphological, biogeographical and biochemical characters

For a long time, systematists have subdivided the genus Pinus into Diploxylon and Haploxylon according to morpho-anatomy and the number of needles. Nevertheless, divergent views remain regarding the structure of these two subgenera, mainly at the section and subsection levels. We propose to clarify some of these uncertainties by studying 45 Pinus taxa of different origins. Our results, based on morphometric and biochemical (flavonoids) parameters, complement those obtained from classical anatomical and morphological studies, and also modern macro-molecular markers (proteins, DNA). We confirm the subdivision of the genus into Pinus = Diploxylon versus Strobus = Haploxylon and the further sectioning of the first subgenus into sections Pinus and Trifoliae. Moreover, we specify the different subsections, whereby the contents of the methylated flavonol isorhamnetin coupled with needle morphometry play a significant role (subsections Pinus vs. Pinaster in section Pinus, Australes + Ponderosae vs. Contortae in section Trifoliae). Given that isorhamnetin proceeds from quercetin by the irreversible action of an O-methyl-transferase, this methylated flavonol becomes a dynamic marker in such way that the taxa rich in isorhamnetin can be considered as more “derived = evolved”. In addition, there exists a highly significant negative correlation between methylation index and number of needles. Consequently, the pines from the Holarctic Strobus group (with five needles and low isorhamnetin contents) can be considered as “ancestral”, in reference to a Laurasian origin of the genus. In the subgenus Pinus, the Nearctic group (=section Trifoliae) remains near the ancestral base. On the other hand, the Holarctic subset “densiflorae” is connected to the other members (mainly European) of the polyphyletic subsection Pinus, in particular with series “sylvestres”. Because of their very high contents of isorhamnetin, the Mediterranean pines result from an accentuation of this evolutionary trend (=subsection Pinaster). In fact, the pines growing under hot and dry climates (Mediterranean region) are highly evolved compared to those from cold and/or wet regions (Eurasia and North America but also, to a lesser extent, the south-eastern USA and East Asia). Our dynamic propositions based on plant phenolics data complete those from more modern macromolecular (DNA, proteins) studies.

Toward understanding the distribution of Laurasian frogs: A test of Savage’s biogeographical hypothesis using the genus Bombina

Several anuran groups of Laurasian origin are each co-distributed in four isolated regions of the Northern Hemisphere: central/southern Europe and adjacent areas, Korean Peninsula and adjacent areas, Indo-Malaya, and southern North America. Similar distribution patterns have been observed in diverse animal and plant groups. Savage [Savage, J.M., 1973. The geographic distribution of frogs: patterns and predictions. In: Vial, J.L. (Ed.), Evolutionary Biology of the Anurans. University of Missouri Press, Columbia, pp. 351–445] hypothesized that the Miocene global cooling and increasing aridities in interiors of Eurasia and North America caused a southward displacement and range contraction of Laurasian frogs (and other groups). We use the frog genus Bombina to test Savage’s biogeographical hypothesis. A phylogeny of Bombina is reconstructed based on three mitochondrial and two nuclear gene fragments. The genus is divided into three major clades: an Indo-Malaya clade includes B. fortinuptialis, B. lichuanensis, B. maxima, and B. microdeladigitora; a European clade includes B. bombina, B. pachypus, and B. variegata; and a Korean clade contains B. orientalis. The European and Korean clades form sister-group relationship. Molecular dating of the phylogenetic tree using the penalized likelihood and Bayesian analyses suggests that the divergence between the Indo-Malaya clade and other Bombina species occurred 5.9–28.6 million years ago. The split time between the European clade and the Korean clade is estimated at 5.1–20.9 million years ago. The divergence times of these clades are not significantly later than the timing of Miocene cooling and drying, and therefore can not reject Savage’s hypothesis. Some other aspects of biogeography of Bombina also are discussed. The Korean Peninsula and the Shandong Peninsula might have supplied distinct southern refugia for B. orientalis during the Pleistocene glacial maxima. In the Indo-Malaya clade, the uplift of the Tibetan Plateau might have promoted the split between B. maxima and the other species.

Hemiplasy: A New Term in the Lexicon of Phylogenetics

Waddell, P. J., and S. Shelley. 2003. Evaluating placental interordinal phylogenies with novel sequences including RAG1, γ -fibrinogen, ND6, and mt-tRNA, plus MCMC-driven nucleotide, amino acid, and codon models. Mol. Phylogenet. Evol. 28:197–224. Waters, P. D., G. Dobigny, P. J. Waddell, and T. J. Robinson. 2007. Evolutionary history of LINE-1 in the major clades of placental mammals. PLoS ONE 2:e158. Wible, J. R., G. W. Rougier, M. J. Novacek, and R. J. Asher. 2007. Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary. Nature 447:1003–1006.

Afrotherian mammals: a review of current data

The supraordinal mammalian clade Afrotheria was first recognized in its entirety based on DNA analysis dating to the mid-1990s. Since then, this “African clade”, which includes proboscideans, sirenians, hyracoids, tubulidentates, elephant-shrews, tenrecs and chrysochlorids, has been supported by numerous molecular and genomic studies. According to these molecular inferences, the origin of crown Afrotheria goes back into the Cretaceous, with estimates from over 100 to under 80 Mya. Morphological phylogenies have not completely recovered Afrotheria, although its paenungulate core (proboscideans, sirenians and hyracoids) was named in 1945 by the paleontologist George Simpson. Recent paleontological studies concur with molecular ones in evoking some affinities between paenungulates, aardvarks and elephant-shrews. Moreover, the position of tenrecs and golden moles within afrotherians is supported by some recent concatenations of morphological and molecular phylogenetic datasets. The phylogenetic position of Afrotheria relative to the other supraordinal placental clades has been debated, the most recent analyses of genomic and concatenated data support a basal position within Placentalia. Molecular data suggest an African origin for Afrotheria and a long period of endemism on that continent. When adding the paleontological data to this scenario, the paleobiogeographic history of Afrotheria becomes more complex. For instance, these data argue for the broad distribution of afrotherians during the Tertiary and do not exclude their Laurasian origin. In fact, some Laurasian taxa could be closely related to the earliest afrotherians (hyracoids, proboscideans and elephant-shrews) found in the early Eocene of North Africa. Other Afrotherian groups are known with certitude from East Africa since the beginning of the Miocene.

Curtisia (Cornales) from the Eocene of Europe and its phytogeographical significance

Fossil remains of Curtisia Aiton (Cornales) are recognized for the first time from the Tertiary of Europe, based on early Eocene anatomically preserved fruits from the London Clay and Poole Formations of southern England. The modern distribution of this monotypic genus is limited to the cape of South Africa. Curtisia quadrilocularis (Reid & Chandler) comb. nov. fruits have globose tetralocular endocarps composed of isodiametric sclereids with a single seed per locule, a prominent axial vascular canal, apical placentation, and four germination valves. All of these characters, as well as size, correspond to extant Curtisia. Although many fossil taxa from the Eocene of Europe have been shown to have their closest extant relatives in Asia, this occurrence of Curtisia highlights Tertiary floristic exchange between Europe and Africa. The newly recognized fossil occurrences suggest a Laurasian origin for Curtisia, in conformity with the fossil record for several other genera of the Cornales. In addition, our rejection of the former assignment of this species to Leucopogon causes us to question whether Epacridaceae were present in the Tertiary of Europe. © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society, 2007, 155, 127‐134.

Cretaceous eutherians and Laurasian origin for placental mammals near the K/T boundary

Estimates of the time of origin for placental mammals from DNA studies span nearly the duration of the Cretaceous period (145 to 65 million years ago), with a maximum of 129 million years ago and a minimum of 78 million years ago. Palaeontologists too are divided on the timing. Some support a deep Cretaceous origin by allying certain middle Cretaceous fossils (97-90 million years old) from Uzbekistan with modern placental lineages, whereas others support the origin of crown group Placentalia near the close of the Cretaceous. This controversy has yet to be addressed by a comprehensive phylogenetic analysis that includes all well-known Cretaceous fossils and a wide sample of morphology among Tertiary and recent placentals. Here we report the discovery of a new well-preserved mammal from the Late Cretaceous of Mongolia and a broad-scale phylogenetic analysis. Our results exclude Cretaceous fossils from Placentalia, place the origin of Placentalia near the Cretaceous/Tertiary (K/T) boundary in Laurasia rather than much earlier within the Cretaceous in the Southern Hemisphere, and place afrotherians and xenarthrans in a nested rather than a basal position within Placentalia.

Spiny Norman in the Garden of Eden? Dispersal and early biogeography of Placentalia

The persistent finding of clades endemic to the southern continents (Afrotheria and Xenarthra) near the base of the placental mammal tree has led molecular phylogeneticists to suggest an origin of Placentalia, the crown group of Eutheria, somewhere in the southern continents. Basal splits within the Placentalia have then been associated with vicariance due to the breakup of Gondwana. Southern-origin scenarios suffer from several problems. First, the place of origin of Placentalia cannot be reconstructed using phylogenetic reasoning without reference to outgroups. When available outgroups are considered, a Laurasian origin is most parsimonious. Second, a model of pure vicariance would require that basal placental splits occurred not with the breakup of Gondwana, but of Pangea in the Late Triassic—Early Jurassic. This event long preceded even the oldest molecular divergence estimates for the Placentalia and was coeval only with the earliest mammals in the fossil record. Third, a problem with the number of dispersal events that would be required emerges under different southern-origin scenarios. In considering the geographic distribution of the major placental clades at their first appearance (mostly Early Cenozoic), it becomes clear that a Laurasian center of origin would require fewer dispersal events. Southern-origin models would require at least twice the number of dispersal events in comparison with a model of Laurasian origins. This number of required dispersal events increases if extinct groups of placental mammals are also considered. Results are similar assuming a morphology-based phylogeny. These facts, along with earlier findings speaking against a major placental radiation deep in the Cretaceous without leaving fossil evidence, suggest an origin of Placentalia somewhere in Laurasia with few supraordinal splits occurring before the last 5–10 million years of the Cretaceous.

Paleobiogeography of Africa: How distinct from Gondwana and Laurasia?

Although Africa was south of the Tethys Sea and originally belonged to the Gondwana, its paleobiogeographical history appears to have been distinct from those of both Gondwana and Laurasia as early as the earliest Cretaceous, perhaps the Late Jurassic. This history has been more complex than the classical one reconstructed in the context of a dual world (Gondwana vs. Laurasia). Geological and paleobiogeographical data show that Africa was isolated from the Mid-Cretaceous (Albian–Aptian) to Early Miocene, i.e., for ca. 75 million years. The isolation of Africa was broken intermittently by discontinuous filter routes that linked it to some other Gondwanan continents (Madagascar, South America, and perhaps India), but mainly to Laurasia. Interchanges with Gondwana were rare and mainly “out-of-Africa” dispersals, whereas interchanges with Laurasia were numerous and bidirectional, although mainly from Laurasia to Africa. Despite these intermittent connections, isolation resulted in remarkable absences, poor diversity, and emergence of endemic taxa in Africa. Mammals suggest that an African faunal province might have appeared by Late Jurassic or earliest Cretaceous times, i.e., before the opening of the South Atlantic. During isolation, Africa was inhabited by vicariant West Gondwanan taxa (i.e., taxa inherited from the former South American–African block) that represent the African autochthonous forms, and by immigrants that entered Africa owing to filter routes. Nearly all, or all immigrants were of Laurasian origin. Trans-Tethyan dispersals between Africa and Laurasia were relatively frequent during the Cretaceous and Paleogene and are documented as early as the earliest Cretaceous or perhaps Late Jurassic, i.e., perhaps by the time of completion of the Tethys between Gondwana and Laurasia. They were permitted by the Mediterranean Tethyan Sill, a discontinuous route that connected Africa to Laurasia and was controlled by sea-level changes. Interchanges first took place between southwestern Europe and Africa, but by the Middle Eocene a second, eastern route — the Iranian route — involved southeastern Europe and southwestern Asia. The Iranian route was apparently the filtering precursor of the definitive connection between Africa and Eurasia. The relationships and successive immigrations of mammal (mostly placental) clades in Africa allow the recognition of five to seven phases of trans-Tethyan dispersals between Africa and Laurasia that range from the Late Cretaceous to the Eocene–Oligocene transition. These Dispersal Phases involve dispersals toward Laurasia and/or toward Africa (immigrations). The immigrations in Africa gave rise to faunal assemblages, the African Faunal Strata (AFSs). All successful and typical African radiations have arisen from these AFSs. We recognize four to six AFSs, each characterized by a faunal association. Even major, old African clades such as Paenungulata or the still controversial Afrotheria, which belong to the oldest known AFS involving placentals, ultimately originated from a Laurasian stem group. Africa was an important center of origin of various placental clades. Their success in Africa is probably related to peculiar African conditions (endemicity, weak competition). Although strongly marked by endemicity, the African placental fauna did not suffer extinctions of major clades when Africa contacted Eurasia. The present geographic configuration began to take shape as early as the Mid-Cretaceous. At that time, the last connections between Africa and other Gondwanan continents began to disappear, whereas Africa was already connected to Eurasia by a comparatively effective route of interchange.

A new genus and species of pangolin (Mammalia, Pholidota) from the late Eocene of Inner Mongolia, China

ABSTRACT A partial postcranial skeleton from the late Eocene of the Shara Murun region of northern China is described as a new genus and species of fossil pangolin, Cryptomanis gobiensis. Cryptomanis displays numerous diagnostic pangolin characteristics, including enrolled lumbar zygapophyses and fissured ungual phalanges. Like the anatomically similar North American Eocene pangolin Patriomanis, it retains primitive mammalian features such as a convex astragalar head and a prominent femoral third trochanter that are lost in extant pangolins. The systematic position of Cryptomanis within Pholidota is not unambiguously resolved. It is tentatively placed in the family Patriomanidae, which we restrict to Cryptomanis and the closely similar Patriomanis. Cryptomanis differs from modern pangolins in its more robust proximal limb elements, its lack of a greatly enlarged third manual digit, its slender tail, and its more elongate, grasping pedal digits. These traits suggest an animal well adapted for digging but with a tendency toward a semi-arboreal lifestyle. This new genus and species represents the oldest and most northerly Asian record of pangolins, and indicates that pangolins were widely distributed throughout Laurasia during the Eocene. It is consistent with a Laurasian origin for pangolins.

Phylogeny and Evolutionary History of Old World Suboscine Birds (Aves: Eurylaimides)

Molecular and morphological data were used to derive a phylogenetic hypothesis for the Eurylaimides, an Old World bird group now known to be distributed pantropically, and to investigate the evolution and biogeography of the group. Phylogenetic results indicated that the Eurylaimides consist of two monophyletic groups, the pittas (Pittidae) and the broadbills (Eurylaimidae sensu lato), and that the broadbills consist of two highly divergent clades, one containing the sister genera Smithornis and Calyptomena, the other containing Pseudocalyptomena graueri, Sapayoa aenigma, the asity genera Philepitta and Neodrepanis, and five Asian genera. Our results indicate that over a ,10 million year time span in the early Tertiary, the Eurylaimides came to inhabit widely disjunct tropical regions and evolved disparate morphology, diet, and breeding behavior. Biogeographically, although a southern origin for the lineage is likely, time estimates for major lineage splitting do not correspond to Gondwanan vicariance events, and the biogeographic history of the crown clade is better explained by Laurasian climatic and geological processes. In particular, the timing and phylogenetic pattern suggest a likely Laurasian origin for the sole New World representative of the group, Sapayoa aenigma.

Phylogeny and Historical Biogeography of <I>Anaxagorea</I> (Annonaceae) Using Morphology and Non-Coding Chloroplast Sequence Data

The Annonaceae are a pantropical angiosperm family, in which Anaxagorea is sister to the rest of the family based on previous phylogenetic studies. Anaxagorea is the only genus of Annonaceae with a disjunct distribution in South and Central America and southeast Asia. Earlier arguments on the biogeographic history of Annonaceae led to the hypothesis of a Laurasian origin for Anaxagorea. A detailed phylogenetic study was conducted using 75 morphological characters and molecular sequences from the atpB-rbcL, psbA-trnH, and trnL-trnF spacer regions and the trnL intron. Molecular analyses alone do not support the monophyly of the Asian species, but the morphological and combined molecular and morphological analyses do. All analyses place most Central American species in a clade, but none support an Asian-Central American clade. South American species form a basal grade, thereby refuting the hypothesis of a Laurasian origin for the genus and indicating instead a Gondwanan origin. Parsimony optimizations and DIVA reconstructions of biogeographic data indicate separate dispersals from South America to Central America and to Asia. Molecular age estimates indicate an Eocene origin for the genus. The clade containing the Asian and Central American species is dated to be younger than the Oligocene climatic deterioration, which reduces support for the North Atlantic land bridge as a dispersal route from South America to Asia.

Phylogeny and biogeography ofOrobanchaceae

Orobanchaceae, as it is currently defined, includes all levels of parasitic ability ranging from nonparasitic (Lindenbergia) to facultative and obligate hemiparasites to obligate holoparasites. Several genera are of economic importance as crop weeds and have been studied by scientists interested in developing methods of control, but most genera have not been studied in a comparative framework. In this study we have used ITS sequence data to build a phylogenetic framework with which to examine previous systematic hypotheses of relationships among genera, and biogeographic hypotheses of either a Cretaceous, Gondwanan or mid-Tertiary, Laurasian origin of the family. A single-most parsimonious ITS tree was produced from a combined data set of nucleotides and gap characters. Our results support the current classification ofOrobanchaceae and a hypothesis of a mid-Tertiary, Laurasian origin of the family.

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.

Timing and biogeography of the eutherian radiation: fossils and molecules compared

Theria includes Eutheria and its sister taxon Metatheria. Placentalia includes extant eutherians plus their most recent common ancestor. The oldest eutherian is from 125 mya (million years ago). Molecular studies place this origin at about 130–185 mya. Older dates cannot be refuted based on fossil evidence as earliest eutherian remains are scarce. Earliest superordinal clades (hence Placentalia) range from 64–104 mya (median 84 mya) based on molecules, similar to 85–90 mya based on fossils. Superordinal clades Archonta, Ferungulata, Glires, and Paenungulata based on fossils are similar to molecularly based clades, except Afrotheria was not predicted by fossils. Both fossils and molecules recognize 16 of 18 extant placental orders. Fossils place the origins of orders around 65 mya as do some molecular studies, but others suggest ordinal diversification as old as 100 mya. Fossil evidence supports a Laurasian origin for Eutheria (and Metatheria) and Placentalia, although some molecular studies suggest a Gondwanan origin for both taxa.

Biogeography of Southeast Asia and the West Pacific

The biogeography of Southeast Asia and the West Pacific is complicated by the fact that these are regions on the border of two palaeocontinents that have been separated for a considerable period of time. Thus, apart from any patterns of vicariance, two general patterns relating to dispersal can be expected: a pattern of Southeast Asian elements, perhaps of Laurasian origin, expanding into Australian areas, and a reverse pattern for Australian elements, perhaps of Gondwanan origin. On top of this, both Australian and Southeast Asian elements occur in the Pacific. They dispersed there as the Pacific plate moved westward, bringing the different islands within reach of Southeast Asia and Australia. In order to reconstruct the biotic history of these areas, two large data sets consisting of both plants and animals were generated, one for each pattern, which were analysed using cladistic methods. The general patterns that emerged were weakly supported and do not allow general conclusions.