Morphology of the palate and braincase of Dimetrodon milleri

The palate and partial braincase of the holotype of Dimetrodon milleri (MCZ 1365) are preserved in three dimensions, but have yet to be described in detail. Here, we describe these structures for the first time for this species, and compare them with the better-known specimens of D. limbatus. Interesting characteristics of the morphology include the patterns of articulation of the palatal elements, including the palatine and vomer, and anatomy of the pterygoid in the posterior region of the palatal vacuities. Dimetrodon milleri is found to differ from D. limbatus in the lack of teeth on the ectopterygoid, the shape of the basal process of the epipterygoid, and the anterior extent of the palatine and pterygoid. The two species are similar in the relative position of the basicranial articulation, but differ significantly from that in other sphenacodontids, including Secodontosaurus and Sphenacodon. The evolution of these cranial features will be the subject of future phylogenetic analyses of sphenacodontids.     

Morphology of the gynoecium and systematic position of the Ochnaceae

The gynoecium is syncarpous in all Ochnaceae. In the Ochnoideae carpels are peltate with a conventional cross-zone bearing one ovule, or, in Lophira , a very broad cross-zone with an horizontal ovular row. In Ochna and Brackenridgea , the style is gynobasic, each carpel develops transmitting tissue on its morphologically dorsal surface, and this tissue lines a canal or originates a solid inner strand in each carpel at style level. The style is tubular, with an inner cuticle, and compound, each component with its own transmitting tissue. In Ouratea the style is solid with a single compound transmitting strand. In Lophira and Elvasia the transmitting tissue seems to be developed by the morphologically ventral carpellary surfaces. Ovules are unitegmic with a bivalent integument.
In the Sauvagesioideae carpels are peltate, but with ovules above the cross-zones, on margins of the symplicate zone. In Euthemis , there is one ovule on each side of, and close to, each cross-zone. The single stylar canal is bounded by the morphologically dorsal carpellary surfaces. In Sauvagesia ovules occur on both sides of the cross-zones but most of them are above on carpel margins, as are all ovules of Cespedesia. The stylar canal of Sauvagesia is bounded by the ventral carpel surfaces, three strips of the outer surface passing inside at the sutures and developing into transmitting tissue. The stylar canal of Cespedesia is bounded by the dorsal carpel surfaces. The gynoecium of Wallacea has two epeltate carpels with a laminar placentation, the carpel margins being displaced on to the topographically ventral carpel surfaces with a row of ovules along each margin. Ovules are bitegmic.
The Ochnoideae, which shows relationships with the Rutaceae, Meliaceae, Simaroubaceae and Hippocastanaceae, is more advanced than the Sauvagesioideae, which clearly belongs in the Violales. The Ochnaceae is to be placed in the Violales.     

A new specimen of Biseridens qilianicus indicates its phylogenetic position as the most basal anomodont

A new well-preserved basal therapsid skull from the Xidagou Formation, Middle Permian of China, is identified as Biseridens qilianicus. The following synapomorphies distinguish Biseridens as an anomodont and not an eotitanosuchian as previously described: short snout; dorsally elevated zygomatic arch and septomaxilla lacking elongated posterodorsal process between nasal and maxilla. The presence of a differentiated tooth row; denticles on vomer, palatine and pterygoid; contact between tabular and opisthotic; lateral process of transverse flange of pterygoid free of posterior ramus and absence of mandibular foramen exclude it from other anomodonts. Our cladistic analysis indicates Biseridens to be the most basal anomodont, highlights separate Laurasian and Gondwanan basal anomodont clades and suggests that dicynodonts had their origins in the Gondwanan clade. The co-occurrence of the most basal anomodont (Biseridens) together with the most basal therapsid (Raranimus), basal anteosaurid dinocephalians, bolosaurids and dissorophids suggests that the earliest therapsid faunas are from China.     

Morphology,systematic position,and distribution of Bothriocidaroid echinoids

This is a brief review of conceptions of morphology, distribution and systematic position of the most ancient echinoid group—order Bothriocidaroida. It comprises 3 genera: Bothriocidaris, Neobothriocidaris, and Unibothriocidaris. More than 20 species of these genera are distributed from Upper Ordovician (Caradocian) to Lower Silurian (Llandoveri) in North Western Europe and North America. The question of whether this group belongs to the class Echinoidea or not has been the subject to discussions several times, particularly based on cladistic methodology. In my opinion the peculiarities of bothriocidaroids are quite typical of archetype definition of this class, however, so-called unique modalities of its merons are actually prone to variation both inside the group and among other echinoid groups. For example, Bothriocidaris maquoketensis has a structure transitional from uniserial to biserial interambulacra, however uniserial interambulacra are found in Paleozoic family Cravenechinidae and in some Cretaceous holasteroids and Cenozoic clypeasteroids. Unfortunately, such an important feature as the apical system is found only in one genus Bothriocidaris.     

Morphology of the family Rhoipteleaceae in relation to its systematic position

The present paper is devoted to a study of the basic morphological and anatomical characteristics of the endemic family Rhoipteleaceae from China. The fundamental pattern of the morphological and anatomical characteristics of the Rhoipteleaceae is similar to those of the Juglandaceae in wood anatomy, resinous peltate scales, apetaly, bicarpellate pistils, one-seeded fruits and exalbuminous seeds. Whereas Rhoipteleaceae has stipules; perfect flowers with superior 2-loculed ovaries, anatropous ovules and two integuments; vessel elements of the secondary xylem with the scalariform perforation, and 2–8 (18) pores on the oblique plate being observable; vascular rays heterocellular and tricolporate pollen. The above characteristics–at least most of them, agree pretty well with those depicted by Manning in his “Pre-Juglandaceae”. It is quite possible that the Juglandaceae is derived from “Pre-Juglandaceae”by way of the Rhoipteleaceae, as the morphological and anatomical features as indicated above tend to show that the Rhoipteleaceae is more primitive than Juglandaceae. The Rhoipteleaceae was previously considered as related to the Betulaceae or Ulmaceae, a view, which the present study does not prove to be acceptable. Both Takhtajan (1969) and Cronquist (1968) pointed out that the Juglandales, Urticales, Myricales, Fagales are all direct derivatives from the Hamamelidales. However, since the Rhoipteleaceae is simillar to the Betulaceae in wood anatomy and pollen, it seems that there too could have certain relationships between the Rhoipteleaceae and the Betula-ceae in the course of evolution.     

Floral ontogeny and systematic position of the Didiereaceae

Floral ontogenetical data from all four genera of the Didiereaceae (s.str.) are presented for the first time. All Didiereaceae s.str. are dioecious, having unisexual flowers with organ rudiments of the opposite sex. Two median bracts followed by a tetramerous perianth (two alternating dimerous ``whorls'), a slightly complex androecium with 6–12 stamens in a single row (on a common ring primordium), four of which mostly alternating with the perianth members, and one basal ovule connecting three free septa at their very base are flower characters in Didiereaceae, supporting phylogenetic analyses based on nucleotide sequence data. Closest relatives are the (formerly) portulacaceous genera Portulacaria (5 stamens alternating with the perianth), Ceraria (5 stamens alternating with the perianth), and Calyptrotheca (many stamens), all with pentamerous perianths, from which the tetramerous perianth in Didiereaceae can be derived. Applequist and Wallace (2003) included these three genera in an expanded family Didiereaceae (with three subfamilies).     

The distribution and systematic position of the Thermosbaenacea

Summary The oasis of El Hamma, southern Tunisia, was visited in September 1950 and 714 specimens of Thermosbaena mirabilis Monod were collected from two baths fed by hot-springs, Ain el Bordj, the type-source, and Ain Sidi Abd el Kadar where the animal had not previously been recorded. The specimens consisted of 164 males, 123 females (73 non-breeding; 50 with brood-pouches), and 94 juveniles; 333 specimens were unfortunately lost on the return journey. Thermosbaena lives in warm brackish water and can survive temperatures fluctuating between 37° and 47° C. but becomes moribund around 35° and dies around 30° C.Apart from examining the springs and baths at El Hamma, a search was made for Thermosbaena in 14 wells and 11 springs scattered over a wide area around El Hamma and Gabès; the River El Hamma was also sampled. The search proved negative in all but the two El Hamma baths already specified. It is suggested that the animal occupies an interstitial habitat in the thermal ground-water at El Hamma, and that it has been collected in the baths not because it has been brought there by the springs flowing into them (as previously believed), but because in the baths the collector has by chance had access to the interstitial habitat. There are grounds for believing that the three species of Monodella discovered on the Italian and Yugoslavian coasts (M. stygicola, M. argentarii, and M. halophila) are also interstitial forms, and that an ancestral habitat in the sea-bed of that part of the Mesogean (Tethys) Sea now represented by the Mediterranean was common to all members of the Thermosbaenacea. The palaeogeographic history of the Mesogean in the North African, Italian, and Yugoslavian areas is discussed and two hypotheses are formulated to account for the present-day habitat of Thermosbaena. The first would regard the organism as a legacy from the final retreat of the Mesogean from southern Tunisia in the lower Eocene. The second envisages the establishment of ancestral stock in a lake lying nearby El Hamma at a time during the Quaternary when a rise in the level of the Mediterranean had converted the lake into a brackish lagoon. This lake subsequently dried out to form the present-day Chott Djerid and it is suggested that Thermosbaena colonized the thermal brackish ground-water at El Hamma as a measure of survival in face of the increasingly saline ground-water of the developing chott. The second hypothesis is regarded as the most plausible. It is considered that the coastal locations of the Monodella species so far discovered indicate a comparatively recent colonization from the sea-bed of the Mediterranean via littoral ground-water. It is pointed out, however, that the palaeogeographic history of Italy and Yugoslavia renders the occurrence of as yet undiscovered species in the Italian and Balkan interior a distinct possibility, the organisms persisting as freshwater or brackish survivors of the Mesogean regression which followed the Pliocene.The systematic position of the Thermosbaenacea is reviewed in the light of recent work and it is concluded that little significance should be attached to the intermediate position of the order between the Peracarida and Syncarida suggested by Taramelli (1954), or to the stomatopodan affinities of the group suggested by Glaessner (1957). It would appear that these relict malacostracans should either be included in the Peracarida, or placed in a pre-peracaridan position as advocated by Siewing (1956, 1958), but the inclusion of the Thermosbaenacea in a new division Pancarida (Siewing, 1958), equivalent in rank to the Peracarida, is clearly premature.

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Sommaire En septembre 1950, au cours d'une visite à El Hamma, oasis au sud de la Tunisie, 714 spécimens appartenant au genre Thermosbaena mirabilis Monod furent récoltés dans deux bassins alimentés par des sources thermales, Ain el Bordj, source typique, et Ain Sidi Abd el Kadar, où jamais encore de tels échantillons n'avaient été trouvés. Cette collection comprenait: 164 mâles, 123 femelles (73 stériles et 50 avec poches reproductrices) et 94 non-adultes. Malheureusement 333 de ces animaux furent perdus durant le voyage de retour. Thermosbaena vit dans une eau chaude et saumâtre, elle peut survivre à des temperatures variant de 37° à 47° C., mais elle commence à s'éteindre aux environs de 35° et meurt aux approches de 30° C.Une recherche pour trouver Thermosbaena fut entreprise, non seulement dans les deux bassins à El Hamma, mais aussi dans 14 puits et sources disséminés sur une large étendue autour d'El Hamma et de Gabès, ainsi que dans la rivière El Hamma dont des échantillons furent analysés. Rien ne fut trouvé en dehors des deux sources mentionnées en premier lieu. On suppose que ces animaux habitent certains interstices dans les fonds des sources thermales d'El Hamma, et qu'ils y ont été trouvés, non pas parce que amenés la par l'écoulement des eaux, mais parce que le collectionneur eut la chance d'acceder à leur terrain d'habitat. Il est raisonnable de croire que les 3 espèces de Monodella trouvées sur les côtes d'Italie et de Yougoslavie (M. stygicola, M. argentarii, et M. halophila) sont aussi du genre habitant des interstices et qu' un ancien habitat, dans les fonds de cette partie de la Mer mésogéenne (Tethys) maintenant réprénté par la Méditerranée était commun à tous les membres des thermosbenacés. L'histoire paléogéographique du Mésogée dans les régions nord-africaines, italiennes, et yougoslaves est en discussion et on formule deux hypothèses pour expliquer le présent habitat de Thermosbaena. La première considérait l'organisme comme un legs de la retraite finale du Mésogée depuis la Tunisie méridionale dans l'Eocène inférieure. La seconde envisage l'établissement d'une réserve ancestrale dans un lac se trouvant près d'El Hamma à une époque où un relèvement du niveau de la Méditerranée avait converti le lac en un lagon saumâtre. Ensuite ce lac s'est asséché pour former l'actuel Chott Djerid et on formule la suggestion que les Thermosbaena ont colonisé l'eau thermale saumâtre à El Hamma comme mesure de survie devant l'eau de plus en plus salée du chott en voie de dévéloppement. La deuxième hypothèse est estimée comme la plus plausible. On considère que la position sur la côte de l'espèce Monodella, dans la mesure où elle a été découverte, indique une colonisation comparativement récente partant du lit de la Méditerranée par l'intermédiaire des eaux littoraux. On souligne, cependant, que l'histoire paléogéographique de l'Italie et de la Yougoslave fait de la trouvaille d'espèces non encore découvertes dans l'Italie et l'intérieur des Balkans une possibilité distincte, les organismes persistant comme survivants d'eau douce ou saumâtre de la regression mésogéene qui suivit le Pliocène.La position systématique des thermosbenacés a été mise au point au cours de trauvaux récents, et l'on arrive à conclure que la position intermédiaire de l'ordre entre la Peracarida et la Syncarida, comme suggeré par Taramelli (1954), ou les affinités stomatopodéennes au groupe suggeré par Glaessner (1957) signifient peu de choses. Il semblerait que ces résidus malacostracéens devraient être inclus à la Peracarida ou placés dans une position pré-peracaridéenne, comme le recommande Siewing (1956, 1958), mais établir que les thermosbenacés sont une branche nouvelle Pancarida (Siewing, 1958) à un rang semblable à la Peracarida, serait certainement une conclusion prematurée.

     

Reevaluation of the systematic position of Scenella

Specimens originally illustrated from Lower Cambrian rocks of the Sierra Morena in Badajoz and Sevilla Provinces, southwestern Spain are supplemented by new material from another locality and are described as Scenella morenensis n. sp. Although Scenella was originally considered to be a patelliform gastropod, for three decades now the genus has been classified as a monoplacophoran. The type species of Scenella, S. reticulata Billings, does not show any paired muscles scars, nor does this new species; such scars are indicative of the Monoplacophora. This new species of Scenella does exhibit features which suggest assignment to the chondrophorine coelenterates. If so, Scenella cannot represent the ancestral form of mollusk.     

Floral anatomy and systematic position ofVivianiaceae

The floral anatomy of four species ofViviania has been studied. In the basic floral plan and essential floral anatomical featuresViviana closely resembles theGeraniaceae. Evidence from vegetative and floral anatomy, ultrastructural studies on phloem as well as phytochemistry supports geranialean affinity ofViviania; the placement within thePittosporales sensuHutchinson being unnatural.     

Subnasal alveolar morphology and the systematic position of Sivapithecus

Recent collecting in the Potwar Plateau of Pakistan has produced several new maxillae attributable to Sivapithecus. Since the subnasal region is preserved in most of these specimens, comparisons with early Miocene hominoid and Pliocene hominid maxillae become possible. On the basis of these comparisons, it has become clear that subnasal/premaxillary morphology distinguishes Asian and African hominoids. Ramapithecus and Sivapithecus share with Pongo an "Asian" subnasal pattern. The Proconsul species from the early Miocene of western Kenya and Australopithecus afarensis from the Hadar Formation of Ethiopia present two subsets of an "African" subnasal pattern. We think it likely that Ramapithecus and Sivapithecus represent a lineage that postdates the last common ancestor of African and Asian hominoids.     

Morphology of the nasal capsule of Heloderma suspectum with comments on the systematic position of helodermatids (Squamata: Helodermatidae)

A serially sectioned embryonic head of Heloderma suspectum formed the basis for a three-dimensional reconstruction of the cartilaginous nasal capsule and its membrane bones. Further, the soft parts of the nasal capsule were analysed microscopically. The embryonic nasal capsule is described and compared to the morphological conditions in other lizards, especially the varanids, which many recent authors believe to be their closest relatives.
The results support the close affinities between the helodermatids and the varanids. Both groups have a well developed recessus lateralis in a cartilaginous capsule, entered by the nasal concha. Further, in both groups a fragmentation of the cartilago paraseptalis occurs in a comparable location and form. Heloderma has no double lacrimal duct, in contrast to previous accounts, but the two canaliculi at the origin of the duct fuse noteworthy far ahead (in other squamates they fuse in front of the bulbus oculi). In the varanids the two branches of the lacrimal duct remain separate and open separately.
Some unique features of Heloderma are presented as well, above all the presence of a second concha.     

Chitinous cuticle and systematic position of tardigrada

The chitinous nature of the cuticle, jaws and stomodaeum of three species of Tardigrada has been definitely proven using a specific micromethod involving a preparation of purified chitinase. These chemical characteristics are in favour of the phylogenetic closeness between Tardigrada and the Arthropoda.     

The jaw function and adaptive radiation of the dicynodont mammal-like reptiles of the Karoo basin of South Africa

The structure and functioning of the dicynodont jaw system are described. A pivoting action of the lower jaw around the palate posteromedian to the caniniform processes is as basic to the jaw movement as is the well-known double-convex jaw articulation. The sequence of origin of the characteristic features of the dicynodonts is analysed cladistically; this demonstrates the patterns of association of these characters into functional character-complexes. The structures of the palate and lower jaw, and their functional integration in feeding, are described and illustrated in standard format. Five different lineages of dicynodont can be identified: Eodicynodon; the robertoids (including Diictodon ); the dicynodontoids (including Dicynodon and the majority of the large dicynodont genera of the Permian and Triassic); the endothiodontoids (including Prodicynodon [='Chelydontops'] and Pristerodon ), and the emydopoids (including Cistecephalus, Myosaurus and Kingoria ). Eodicynodon or a similar form could have been ancestral to the other four lineages. The robertoids probably fed upon the stems and rhizomes of equisetaleans, while the varied dicynodontoids probably fed upon the varied glossopterid seed-ferns. The endothiodontoids, too, were probably herbivorous, but many, perhaps all, of the small emydopoids were burrowing and may have been omnivorous. The dicynodonts were probably ectothermal, and the dicynodontoids may have migrated to warmer latitudes in the winter. Only c. 20 genera of Karoo dicynodont are now recognized as valid, and it is suggested that this fauna is now almost completely known. Their distribution in the Karoo biozones is reviewed and correlated with environmental changes. The Permian ancestors of the Triassic dicynodonts, including Lystrosaurus , probably lived on higher, drier ground, and were therefore already adapted to the more fibrous food that spread into the basins as the climate became drier in the Triassic.     

The systematic position of Psilotum and Tmesipteris

Several interpretations concerning the relationships of the Psilotaceae are discussed. The conclusion that the Psilotaceae are filicalean ferns is defended. New evidence which has appeared since earlier papers on the subject confirms this basic conclusion.     

Mesozoic Araucariaceae: Morphology and systematic relationships

The Southern Hemisphere conifer family Araucariaceae has a very restricted present day distribution, but was more widespread in the past. The genusAraucaria is represented by good fossil material in both hemispheres as early as the Jurassic, whileAgathis is only known from the Southern Hemisphere beginning in the Cretaceous. Cuticle studies of extant araucarians have enabled accurate comparisons of fossil leaves to living taxa.Araucaria SectionBunya is represented by cones of several types in the Jurassic. In addition to these remains, a suite of araucarian cones showing affinities to several sections of the genusAraucaria have been described from England, Japan and North America. Evidence that fossil araucarian cones may have produced seeds with hypogeal germination is discussed in light of recent work on germination of extant bunya seedlings and the discovery of new fossil shoots from the Jurassic Morrison Formation of Utah.     

The systematic position of Phaeocryptopus gaeumannii

Phaeocryptopus gaeumannii, causal agent of the Douglas-fir foliar disease Swiss needle cast, is the only known pathogenic species of the genus. Current classifications place Phaeocryptopus in the Venturiaceae (Pleosporales), typified by the apple-scab pathogen Venturia inaequalis. All core members of this family have hyphomycetous anamorphs. We sought to confirm these relationships by means of phylogenetic analyses of the small (SSU) and large (LSU) subunits and internal transcribed spacer (ITS) region of nuclear ribosomal gene sequences (nrDNA). Analyses indicated that both the genus Phaeocryptopus and the family Venturiaceae, as currently defined, are unnatural groups. Phaeocryptopus nudus, type of the genus, is aligned in the Dothioraceae (Dothideales) and P. gaeumannii in the Mycosphaerellaceae (Capnodiales) near species of Mycosphaerella and Rasutoria. Core representatives of Venturiaceae formed an unambiguous clade but ordinal placement was unresolved. The family apparently is not included in the Pleosporales, Dothideales, Myriangiales or Capnodiales. Coelomycetous Rhizosphaera form-species are accepted generally as anamorphic states of Phaeocryptopus, however the relationship never has been established conclusively. Species of Rhizosphaera are closely related to P. nudus but not to P. gaeumannii, supporting an anamorph-teleomorph connection between Rhizosphaera and Phaeocryptopus and providing further evidence that P. gaeumanii is not congeneric with P. nudus.     

On the systematic position of the lichen genus Heppia

The systematic position of the lichen genus Heppia in the order Lichinales was investigated. 18S rDNA sequence data were analyzed using a Bayesian approach to infer phylogeny using Markov chain Monte Carlo methods. The Lichinales are divided at family level into the sister groups Lichinaceae and Peltulaceae. The genus Heppia forms a highly supported clade in the family Lichinaceae. It is shown that the genus Heppia is morphologically well circumscribed within the Lichinaceae. As a nomenclatural consequence, the family name Heppiaceae is placed into synonymy under the older name Lichinaceae.     

The evolution of the dicynodont feeding system

The skull structure of dicynodonts may be regarded as a complex adaptation towards herbivorous feeding. The present work examines how and why this adaptation may have evolved. A cladogram of the dicynodonts is presented and from it a sequence of hypothetical ancestral forms is inferred. The jaw musculature of dicynodonts and other therapsids is described and in particular the early dicynodont Eodicynodon oosthuizeni is described in detail. This information is used to draw up a sequence of ancestral stages whose basic skull anatomy, jaw muscle organization and masticatory properties are described. Differences in masticatory properties between these stages are pinpointed and an explanation to account for the development of these differences is advanced. It is concluded that the changes in skull organization seen during the evolution of dicynodonts are consistent with the hypothesis that a propalinal jaw action was being improved by selection, and that this was required to permit dicynodonts to be efficient herbivores.