Plesiomorphic Characters Research Articles

Unusual karyotype diversity in the European spiders of the genus Atypus (Araneae: Atypidae)

Compared with araneomorph spiders, karyotypes of the spider infraorder Mygalomorphae are nearly unknown. In this study we investigated karyotypes of European species of the genus Atypus (Atypidae). The male karyotype of A. muralis and A. piceus comprises 41 chromosomes, whereas female complements contain 42 chromosomes. On the other hand, both sexes of A. affinis possess 14 chromosomes only. It is the lowest diploid number found in mygalomorph spiders so far. Furthermore, obtained data suggest X0 sex chromosome system in A. piceus, A. muralis and neo-XY system in A. affinis. Karyotypes of all three Atypus species are composed of biarmed chromosomes only. Thus they differ significantly from the karyotype of A. karschi, the only other species of this genus studied so far. Its karyotype was reported to be composed of acrocentric chromosomes and possesses X(1)X(2)0 sex chromosome system. All this shows that unlike in most genera of araneomorph spiders, mygalomorphs of the genus Atypus exhibit unusual diversity in the number, morphology of chromosomes, and the sex chromosome system. Considering high number of chromosomes being plesiomorphic character in spiders, then karyotypes of A. muralis and A. piceus represent ancestral situation and that of A. affinis being derived by multiple fusions. Karyotype differences in Atypus correspond with morphological differences, namely the number of segments of the posterior lateral spinnerets. Thus in contrast to published hypothesis, the 3-segmented posterior lateral spinnerets of A. affinis should present a derived state.

THE BASAL REPTILE THURINGOTHYRIS MAHLENDORFFAE (AMNIOTA: EUREPTILIA) FROM THE LOWER PERMIAN OF GERMANY

The skeletal anatomy of the Early Permian eureptile Thuringothyris mahlendorffae from the Bromacker Quarry, Germany, is redescribed on the basis of several new specimens. The taxon retains some plesiomorphic characters, such as an ectopterygoid and a tabular, but it also possesses low neural spines and nonswollen neural arches, a combination that is unique for early eureptiles. A phylogenetic analysis places Thuringothyris as the sister taxon of Captorhinidae, excluding any potential “protorothyridid” affinities. Implications of this study are that the swollen neural arches of captorhinids and araeosceloids might have evolved independently, that a downturned rostrum occurred only later in captorhinid evolution, and that the European Permian is important to the understanding of the origin of eureptiles.

Musculature of the male genitalia of Xylophagus cinctus (De Geer) and relationships within the superfamily Xylophagoidea (Diptera, Brachycera)

There is no general agreement on relationships within Xylophagoidea (Diptera, Brachycera). The musculature of the male genitalia of Xylophagus cinctus (De Geer) (Xylophagidae, the most primitive family of Brachycera) is described and compared with that of some other Xylophagoidea: Exeretonevridae (Exeretonevra angustifrons Hardy), Coenomyiidae (Anacanthaspis biafasciata Roder), and Rhagionidae (Rhagio montanus Becker, Chrysopilus dives Loew, and Ch. helvolus Meigen) discussed earlier (Ovtshinnikova, 1989, 1998; Palmer et al., 2000). In spite of the differences in the structure of the genital sclerites, Xylophagidae possess all the muscles found in Coenomyiidae and Rhagionidae. The musculature of the male genitalia of Xylophagus cinctus includes two muscle pairs of the aedeagus sheath (M1 and M2); three muscle pairs of the ejaculatory complex (M30, M31, and M32); one muscle pair of the gonocoxites (M33); two muscle pairs of the gonostyli (M27 and M28); one muscle pair of the proctiger (M21), one muscle pair of the cerci (M29); two pairs of the tergosternal muscles (M51 and M52); and two pairs of the pregenital muscles (M18 and M19). Muscles of the family Exeretonevridae are mostly the same, except for the muscles of the cerci M29, proctiger M29, and pregenital muscles M18 and M19, that are subdivided into two parts. This fact and also a different degree of the development of muscles M32 and M52 clearly distinguish Exeretonevridae from closely related families. The attachment places of the muscles of the aedeagus sheath M2 and of the gonostyli M28, as well as the split character of the tergosternal muscle pair M51 makes it possible to distinguish two sister groups, Xylophagidae plus Exeretonevridae, versus Coenomyiidae plus Rhagionidae. It should be noted that the muscles of the male genitalia of Xylophagidae, Exeretonevridae, Coenomyiidae, and Rhagionidae possess similar plesiomorphic characters, and these families should be united into the superfamily Xylophagoidea. This superfamily is the most primitive superfamily of Brachycera Orthorrhapha and possesses the most stable set and arrangement of male genital muscles within the entire suborder. An improved dendrogram of the phylogenetic relationships between the known groups of Xylophagoidea is proposed on the basis of the structure of male genital muscles.

Revision and phylogeny of Rhamnocercinae Monaco, Wood et Mizelle, 1954 (Monogenoidea: Diplectanidae)

Species of Rhamnocercinae Monaco, Wood et Mizelle, 1954 are gill parasites of sciaenid fishes (Perciformes). Seven are marine species (three in the western Atlantic and four in oriental Pacific) and one is a neotropical freshwater species (Rio Doce Basin, Brazil). While the status of the subfamily may be questioned, this assemblage of species is apparently supported by several shared apomorphic and plesiomorphic characters, such as: (1) peduncular spines with anterior and posterior roots; (2) haptor laterally expanded, armed with anchors (two pairs); bars (one ventral, two dorsal); 14 hooks and haptoral accessory spines; and (3) double (nested) tubes of the male copulatory organ (MCO), directed posteriorly with the genital pore lying posterior to the MCO. The phylogenetic hypothesis for the eight known species of this clade is: (Spinomatrix penteormos (Rhamnocercoides stichospinus, Rhamnocercoides menticirrhi) Rhamnocercus oliveri (Rhamnocercus rhamnocercus (Rhamnocercus stelliferi, Rhamnocercus bairdiella, Rhamnocercus margaritae)). This hypothesis indicates that Spinomatrix penteormos represents the sister group of all remaining rhamnocercines. The resulting phylogenetic sister-group relationships support the transfer of Rhamnocercus stichospinus Seamster et Wood, 1956 to Rhamnocercoides Luque et Iannacone, 1991 as Rhamnocercoides stichospinus (Seamster et Wood, 1956) n. comb.

Classification of flea families (Siphonaptera): I. Family Hystrichopsyllidae (first part)

A contribution is made to the previously elaborated classification of the order Siphonaptera (Medvedev, 1994, 1998). Host-parasite associations, geographical distribution, and morphology of the family Hystrichopsyllidae (sensu Hopkins and Rothschild, 1962, 1966) in comparison with other flea families are analyzed together with a position of the family within the infraorder Hystrichopsyllomorpha. The presence of two spermathecae, frequently used as a taxonomic character, is a character insufficient for the basic phylogenetic reconstructions, e.g., establishment of close relationship between the families Coptopsyllidae and Macropsyllidae or the tribes Ctenopariini and Hystrichopsyllini, because this character is a plesiomorphy of the order Siphonaptera. The subfamily Hystrichopsyllinae (sensu Hopkins and Rothschild, 1962) is characterized by a large number of morphological features which can be considered as plesiomorphic characters of the family Hystrichopsyllidae as a whole. The subfamily Hystrichopsyllinae should be restricted to the tribes Ctenopariini and Hystrichopsyllini. The family Macropsyllidae possesses a unique structure of the ctenidia and some other structures. It should be treated as a group closely related to Hystrichopsyllidae. The family Coptopsyllidae demonstrates another trend in the evolution of the head, thorax, and abdomen.

Shell morphology and phylogenetic origin of oysters

Marquez-Aliagaetal.(2005)presentedinthisjournalaninterestingpaperontheearlyphylogenyofoysters,inwhich they provided clues for ambivalent attachment(i.e.attachmentbytheleftorrightvalveindifferently)oftwo Middle Triassic cementing bivalve species from theGermanMuschelkalk.Chieflybasedonthisassumption,the species in question were transferred from theprospondylid? genus Enantiostreon to the ostreidgenus Umbrostrea, and a descent of the Ostreidaefrom prospondylid bivalves was postulated. Because ofthe far-reaching consequences of these conclusions forthe taxonomy of cementing bivalves, a re-discussion ofthe shell morphology of oysters in the light of theirenigmatic phylogenetic origin seems useful.Marquez-Aliaga et al. (2005, p. 129) stated that“there is a broad consensus that the most importantcharacter defining oysters is attachment to the substrateby the left valve”. However, this introductory statementof Marquez-Aliaga et al. (2005) is in contrast to thecentral find of their study, namely the occurrence ofambivalent attachment in some oyster-like species fromthe Middle Triassic Muschelkalk of the Germanic basin.If this observation was true, transferring the species inquestion (‘Ostracites’ cristadifformis Schlotheim, 1823and ‘O.’ spondyloides Schlotheim, 1823)totheOstreidae, as suggested by Marquez-Aliaga et al.(2005), would require to drop left-sided (sinistral)attachment as a key character of oysters. Even if thiswas accepted, the phylogenetic relationship of ambiva-lently cemented pteriomorphs would still be unclear.Marquez-Aliagaetal.(2005)proposedthatantimarginalribs were an additional shell morphological character ofthe Ostreidae, and that the presence of such ribs in theirspecimens would support its classification as ‘true’oysters.However,antimarginalribsalsooccurinseveralunrelated bivalve families (e.g. Checa and Jimenez-Jimenez, 2003, p. 147), which means that they haveeither developed convergently in different lineages, orthat they represent a plesiomorphic character state. Inorder to give an unambiguous definition of oysterswithout referring to sinistral attachment, it is necessaryto identify additional autapomorphic characters. As Ihave suggested earlier (Hautmann, 2001a, 2004),oysters have two other shell morphological peculiaritiesthat separate them from similar cementing bivalves:(1) Oysters lack a pallial line (Fig. 1), because theirpallial muscles begin and end within the mantlelobes. The only exception is Recent Saccostrea,where the mantle retractor muscles are directlyattached to the valves and a disjunct pallial line isdeveloped (e.g. Stenzel, 1971,p.N968).(2) The attachment surface of the ligament is usuallyarched, with the resilifer of the right valve beingelevated and the flanking attachment area of thelateral ligament impressed (Fig. 2). The shape of

Microsporogenesis and microgametogenesis of Excentrodendron hsienmu (Malvaceae s.l.) and their systematic implications

Flowers, microsporogenesis and microgametogenesis of Excentrodendron hsienmu in opening-functional flowers and non-opening flowers were studied to investigate the evolutionary relationships of Excentrodendron. E. hsienmu is a dioecious species that blossoms every 3–4 years, although large numbers of flower buds develop every year. The anther is tetrasporangiate, the tapetum is of the secretory type, the microspore tetrads are mainly tetrahedral, and the pollen grains are two-celled when shed. Four to six microsporocytes are seen on the transverse section of the anthers, and cytokinesis is simultaneous. The development of the anther wall conforms to the basic type and the anther wall is five or six cells thick, with a fibrous endothecium. The difference between the opening-functional and the non-opening flowers is mainly in the thickness of the anther wall. Early megasporogenesis in staminate flowers up to megaspore mother cell or megaspore tetrads has been observed. Excentrodendron shares with Dombeyeae only plesiomorphic features, but differs in anther wall development type and thickness. Most features of Excentrodendron are shared with Pterospermum, including such synapomorphic features as basic type of anther wall development, five- to six-cell-thick anther wall, biseriate tapetum at some places, and degeneration of microsporocytes, suggesting placement near Pterospermum.

Comparative Structure and Development of Pollen and Tapetum in Pandanales

The newly recircumscribed monocot order Pandanales now includes five families: Cyclanthaceae, Pandanaceae, Stemonaceae, Triuridaceae, and Velloziaceae. We present new data and a review of pollen morphology, microsporogenesis, and tapetal characters in Pandanales in a systematic context. Probable plesiomorphic character states include pollen dispersed as monads, pollen small to medium in size with an ovoid shape, monosulcate apertures, perforate to reticulate sculpturing, a columellate exine with a foot layer, successive microsporogenesis, and a secretory tapetum. These correspond to generalized monocot or lilioid pollen and anther character states, and all occur within Dioscoreales, the sister group to Pandanales. Within Pandanales, there are apparently homoplastic trends in each family toward either reduction in aperture size (e.g., from sulci to pores) or covering the aperture with exine (e.g., from monosulcate to monosulcate‐operculate), resulting in a reduction in the delicate apertural area exposed t...

Coronal organ of ascidians and the evolutionary significance of secondary sensory cells in chordates

A new mechanoreceptor organ, the coronal organ, in the oral siphon of some ascidians belonging to the order Pleurogona has recently been described. In contrast to the known mechanoreceptor organs of ascidian atrium that consist of sensory neurons sending their own axons to the cerebral ganglion, coronal sensory cells are secondary mechanoreceptors, i.e., axonless cells forming afferent and efferent synapses with neurites of neurons located in the ganglion. Moreover, coronal cells exhibit an apical apparatus composed of a cilium accompanied or flanked by rod-like microvilli (stereovilli). Because of the resemblance of these cells to vertebrate hair cells, their ectodermal origin and location in a linear array bordering the bases of the oral tentacles and velum, the coronal organ has been proposed as a homologue to the vertebrate acousticolateralis system. Here we describe the morphology of the coronal organs of six ascidians belonging to the suborders Phlebobranchia and Aplousobranchia (order Enterogona). The sensory cells are ciliated, lack typical stereovilli, and at their bases form synapses with neurites. In two species, the sensory cells are accompanied by large cells involved in synthesis and secretion of protein. We hypothesize that the coronal organ with its secondary sensory cells represents a plesiomorphic feature of ascidians. We compare the coronal organ with other chordate sensory organs formed of secondary sensory cells, i.e., the ventral lip receptors of appendicularians, the oral secondary sensory cells of cephalochordates, and the acousticolateralis system of vertebrates, and we discuss their homologies at different levels of organization.

The systematics of Parasitiformes, especially of Gamasina Leach (Acarina), with new species from Ecuador

This study critically reviews the classification of Parasitiformes, especially of Gamasina. Results indicate that the establishment of the following groups of Parasitiformes is based on plesiomorphic characters which renders the grouping invalid: Anactinochitinosi Grandjean, 1935, Monogynaspida Camin et Gorirossi, 1955, Trichopygidina Hirschmann, 1975 and, within the Gamasina: Dermanyssides (Dermanyssina) Evans et Till, 1978, Epicriides Evans et Till, 1978 and Ascidae Oudemans sensu Lindquist et Evans, 1965. Several taxa of the Ascidae sensu Lindquist et Evans belong to other taxa: Proctolaelaps Berlese and Melichares Hering to the Ameroseiidae Evans, Antennoseius Berlese to the Halolaelapidae Karg, Protogamasellus Karg to the Rhodacaridae Oudemans, Neojordensia Evans and Lasioseius Berlese to the Podocinidae Berlese and Blattisocius Keegan to the Phytoseiidae Berlese. The systematic of Gamasina is revised and a cladogram of 25 families is drawn. The taxon Gamasina is divided into three taxa: Eviphidides, Eugamasides and Ascides. The cladogram reveals that the Ascides first split off and that Eugamasides and Eviphidides have a common root. Further, 18 new species from Ecuador are described and illustrated. Differential diagnoses of new and related species are completed by keys. A total of 15 keys is provided for the taxa Gamasholaspis Berlese, Oloopticus Karg, Platyseius Berlese, Acuphis Karg, Gamasolaelaps Berlese, Proctofissus Karg, Hypoaspis Canestrini, Amblyseius Berlese, Proctolaelaps Berlese, Cheiroseius Berlese, Asca v. Heyden and Parasitus Latreille.

Shape variation in surface and cave populations of the armoured catfishes Ancistrus(Siluriformes: Loricariidae) from the São Domingos karst area, upper Tocantins River, Brazil

Body shape of four distinct populations of Ancistrus cryptophthalmus from different caves in the São Domingos karst area and the local epigean (surface)Ancistrus species were compared using geometric morphometrics. Angélica and Bezerra catfishes were closer to each other and successively to the studied sample of epigean catfishes than to Passa Três and São Vicente I catfishes. Greater similarity between catfishes from the Angélica‐Bezerra cave system to epigean catfishes than to other cave catfishes may represent a plesiomorphic feature. On the other hand, the present analyses allowed the distinction between Passa Três and São Vicente I catfishes, which inhabited the same cave system. Topographic isolation due to the presence of several waterfalls interposed between the stream reaches where these catfishes live may explain such morphological differentiation. Also, the presence of a waterfall downstream of the reach where the Angélica sample was obtained may have contributed to the partial isolation of these catfishes from those living in Bezerra Cave. Differences in population sizes probably influenced the degrees of morphological differentiation observed among the cave populations. The mosaic distribution of character states indicated that the four populations of A. cryptophthalmus have evolved rather independently, but the continuous variation suggests a recent connection between these populations, perhaps with a limited gene flow. Considering other features such as reduction of eyes and pigmentation, and changes in body shape, a separate species status for the epigean and hypogean Ancistrus species from the São Domingos karst area has been maintained.

Acoustic communication and burrow acoustics are reflected in the ear morphology of the coruro (Spalacopus cyanus, Octodontidae), a social fossorial rodent

We studied the middle and inner ears of seven adult coruros (Spalacopus cyanus), subterranean and social rodents from central Chile, using free-hand dissection and routine staining techniques. Middle ear parameters that were focused on here (enlarged bullae and eardrums, ossicles of the "freely mobile type") are believed to enhance hearing sensitivity at lower frequencies. The organ of Corti was of a common mammalian type and revealed three peaks of higher inner hair cell densities. Based on a position frequency map, frequencies were assigned to the respective peaks along the basilar membrane. The first peak at around 300-400 Hz is discussed with respect to the burrow acoustics, while the peak around 10-20 kHz is probably a plesiomorphic feature. The most pronounced peak at around 2 kHz reflects the frequency at which the main energy of vocal communication occurs. The morphology of the ear of the coruro corresponds to the typical pattern seen in subterranean rodents (low frequency and low-sensitivity hearers), yet, at the same time, it also deviates from it in several functionally relevant features.

Evolutionary Studies on an α-amylase Gene Segment in Bats and other Mammals

Comparative studies of salivary glands showed that they maybe related to the adaptive radiation of bats, especially in the family Phylostomidae. In this study we have been searching for a likely relationship between different feeding habits found in bats and possible adaptive changes in a coding segment of the alpha-amylase enzyme. We have also tested some hypothesis about the phylogenetic relationship of bats and other mammals. A 663 bp segment of the alpha-amylase gene, corresponding to the exon 4 and part of the intron c, was sequenced in nine bat species. The exon 4 was also sequenced in further ten mammalian species. The phylogenetic trees generated with different methods produced the same results. When the intron c and the exon 4 were independently analyzed, they showed distinct topologies involving the bat species Sturnira lilium, different from the traditional bat phylogeny. Phylogenetic analysis of bats, primates and rodents supports the Euarchontoglires-Laurasiatheria hypothesis about the relationship among these groups. Selection tests showed that the alpha-amylase exon 4 is under strong purifying selection, probably caused by functional constraints. The conflicting bat phylogenies could not be explained by evolutionary convergence due to adaptive forces, and the different topologies may be likely due to the retention of plesiomorphic characters or the independent acquisition by evolutionary parallelism.

Megasporogenesis and embryo sac development in Excentrodendron hsienmu (Malvaceae) with reference to the systematic affinities of Excentrodendron

Segregation of Excentrodendron and Burretiodendron has hardly been accepted despite their distinct pollen morphology. Megasporogenesis and embryo sac development were studied in Excentrodendron hsienmu in order to examine the basis of segregation of Excentrodendron and Burretiodendron and to study the affinity of Excentrodendron. Excentrodendron hsienmu is dioecious and a large number of flower buds developed every year on mature male and female trees but flower blossoming and fruiting did not occur every year and there was a cycle of 3–4 years. Staminate and pistillate flowers were not distinguishable in the early development stages since both microsporogenesis and megasporogenesis were observed in staminate and pistillate flowers, respectively. Megasporogenesis in staminate flowers degenerated after demarcation of megaspore mother cell or rarely after megaspore tetrads. The monosexual flowers of Excentrodendron were probably derived from bisexual flowers. The ovule was anatropous, bitegmic, and crassinucellate. The primary archesporium of ovules consisted of usually one cell and integument initials were not demarcated at the time of the differentiation of the archesporium. The outer and inner integument of the mature embryo sac was 3–4 and 3 cells thick, respectively. The megaspore mother cell was usually deeply seated in the nucellus before meiosis and gave rise to a linear or rarely T-shaped tetrad. The development of embryo sac conforms to the Polygonum Type. Degeneration was observed commonly after demarcation of megaspore mother cells; 88% of embryo sacs degenerated and only 9% of ovules developed to seeds. Excentrodendron shares with Burretiodendron a number of plesiomorphic characters that are commonly found in members of Malvales. It differs from Burretiodendron mainly in the thickness of the inner integument which is 3 cells thick in Excentrodendron but 4–5 in Burretiodendron. In addition, archesporium is usually unicelled in Excentrodendron but multicelled in Burretiodendron. Segregation of Excentrodendron is therefore supported by the present study. Embryologically, Excentrodendron differs also from Pterospermum, Dombeyeae, and other taxa of the expanded Malvaceae, mainly in the thickness of integuments and number of archesporial cells. The present study does not support the placement of Excentrodendron in the tribe Dombeyeae of Malvaceae s.l.

Evolutionary transformations of fetal membrane characters in Eutheria with special reference to Afrotheria

Analysis of molecular data sets has provided new insights into higher-level relationships of living Eutheria, including the recognition of Afrotheria as a novel taxon. This offers an opportunity to take a fresh look at the evolution of organ systems, including some that are little used in traditional systematics. In the present study, we attempted a reconstruction of the evolution of characters associated with placentation, the fetal membranes and the female reproductive tract. The evolutionary history of 21 characters has been traced, based on a current hypothesis of eutherian relationships, by applying the computer program MacClade. Accordingly, the analysis provides a first comprehensive interpretation of the stem species pattern of Eutheria. Of particular note, this pattern includes an endotheliochorial chorioallantoic placenta. The reconstructed pattern of Eutheria does not change in the basal nodes of the group. Thus, no character transformations occur on the stem lineages of Laurasiatheria or Euarchontoglires, and even Afrotheria has mostly plesiomorphic character conditions. However, two character transformations occur on the common stem lineage of Afrotheria and its sister taxon Xenarthra, i.e., amniogenesis by cavitation instead of folding and the precocial state of the newborn. In addition, we recognized one character transformation on the stem lineage of Afrotheria, i.e., the occurrence of a four-lobed allantoic sac. Thus, contrary to previous assertions, it is possible to identify morphological characters that could be synapomorphic for this novel taxon.

A Tiny Barbet-Like Bird From the Lower Oligocene of Germany: The Smallest Species and Earliest Substantial Fossil Record of The Pici (Woodpeckers and Allies)

Abstract Rupelramphastoides knopfi, a new genus and species of the Pici (barbets, woodpeckers, and allies), is described from Frauenweiler, a Lower Oligocene (30–34 mya) fossil site in Germany. The disarticulated skeleton of the new species constitutes the first associated remains of a fossil member of the Pici and is the smallest known species and earliest substantial fossil record of this taxon. Despite an overall resemblance to modern Ramphastidae, R. knopfi appears to be distinguished from crown group Pici by several plesiomorphic characteristics. It is classified “family incertae sedis,” pending discovery of additional, better-preserved specimens. The fossil record and geographic occurrence of the basal lineages within the crown group are in concordance with an Old World origin of the Pici. The reasons that led to extinction of tiny Pici in Europe remain uncertain, but food competition with passeriform birds during periods of limited food availability may have played a major role. Ein winziger bartvogelähnlicher Vogel aus dem Unter-Oligozän Deutschlands: die kleinste Art und der älteste substantielle Fossilnachweis der Pici (Spechte und Verwandte)

Molecular Phylogenetics of the Leafy Cactus Genus <I>Pereskia</I> (Cactaceae)

Abstract Members of Pereskia exhibit some presumably plesiomorphic characters for the Cactaceae including shrubby habit, non-succulent or partially succulent leaves, and in some species, nearly superior ovaries. In addition, the members show a transition from perigynous flowers with half-inferior ovaries to those species having true receptacular epigyny (the predominant condition in the Cactaceae). To examine interspecific relationships within Pereskia we utilized cpDNA restriction-site data and sequences from two non-coding regions of the plastid genome—the psbA-trnH intergenic spacer and the rpl16 intron. Maximum parsimony and Bayesian analyses identified three major clades: a clade containing the widespread P. aculeata and the Andean species, a clade containing six species found primarily in southeastern Brazil, Paraguay, Uruguay, Argentina, and Bolivia, and a third clade centered in southern Central America and the Caribbean. The relationship between these three clades and the rest of the Cactaceae re...

Ultrastructure of the spermatozoon of Apus apus (Linnaeus 1758), the common swift (Aves; Apodiformes; Apodidae), with phylogenetic implications

AbstractThe spermatozoon of Apus apus is typical of non‐passerines in many respects. Features shared with palaeognaths and the Galloanserae are the conical acrosome, shorter than the nucleus; the presence of a proximal as well as distal centriole; the elongate midpiece with mitochondria grouped around an elongate distal centriole; and the presence of a fibrous or amorphous sheath around the principal piece of the axoneme. The perforatorium and endonuclear canal are lost in A. apus as in some other non‐passerines. All non‐passerines differ from palaeognaths in that the latter have a transversely ribbed fibrous sheath whereas in non‐passerines it is amorphous, as in Apus, or absent. The absence of an annulus is an apomorphic but homoplastic feature of swift, psittaciform, gruiform and passerine spermatozoa. The long distal centriole, penetrating the entire midpiece, is a remarkably plesiomorphic feature of the swift spermatozoa, known elsewhere only in palaeognaths. The long centriole of Apus, if not a reversal, would be inconsistent with the former placement of the Apodiformes above the Psittaciformes from DNA–DNA hybridization. In contrast to passerines, in A. apus the microtubules in the spermatid are restricted to a transient single row encircling the cell. The form of the spermatozoon fully justifies the exclusion of swifts from the passerine family Hirundinidae.

Dallasaurus turneri, a new primitive mosasauroid from the Middle Turonian of Texas and comments on the phylogeny of Mosasauridae (Squamata)

AbstractA new genus and species of primitive-limbed mosasauroid, Dallasaurus turneri, from the Middle Turonian (∼92 Ma) of north-central Texas, is described on the basis of two incomplete skeletons. The new taxon retains plesiomorphic characters such as facultatively terrestrial limbs (plesiopedal) but also exhibits certain characters shared with derived mosasaurs of the subfamily Mosasaurinae. In phylogenetic analysis, the new taxon reconstructs as the basal member of that clade. Other plesiopedal taxa previously included in the family Aigialosauridae reconstruct in basal positions within three different, major clades that include members that achieved the derived (hydropedal) fin-like limb condition. In addition, Opetiosaurus and Aigialosaurus reconstruct as successive outgroup taxa to all other mosasauroids, thereby demonstrating the paraphyletic nature of the current concept of Aigialosauridae. Interpretation of our phylogenetic analysis suggests that three different lineages of mosasauroids independently achieved the derived mosasaur body plan, including fully marine limb modifications culminating in the development of flippers or paddle-like appendages. The inclusion of plesiopedal forms within lineages of well-established hydropedal clades requires a reorganisation of our concepts of Mosasauridae to include these basal forms. In order to avoid continued use of the paraphyletic taxon ‘Aigialosauridae’ as currently defined, we recommend ‘Aigialosauridae’ as a formal taxonomic name be used only for inclusion of Aigialosaurus dalmaticus and potential members of its own independent lineage. This also avoids the implicit polyphyletic use of ‘Mosasauridae’. Additionally, the diagnosis of Mosasauridae should be modified to exclude limb characters that discriminate between more terrestrial versus more aquatic adaptations.

Phylogenetic relationships of the enigmatic species Serratula chinensis and Serratula forrestii (Asteraceae - Cardueae)

The phylogenetic relationships of the Chinese species Serratula forrestii and S. chinensis within the subtribe Centaureinae (Asteraceae – Cardueae) were investigated based on nuclear ribosomal DNA external and internal transcribed spacer sequences. Results indicated that Serratula s. l. is clearly polyphyletic, none of the two species showing close affinities to either Serratula s. str. or Klasea, a genus traditionally included in Serratula. Serratula forrestii has a basal position within the subtribe and has retained most plesiomorphic character states. Serratula chinensis is related to the genera of the Rhaponticum group. Its chromosome number was determined as 2n = 26, and the relationship between this species and the Rhapon-ticum group is discussed from a morphological and karyological point of view.