Primitive Species Research Articles

Expression and phylogeny of candidate genes for sex differentiation in a primitive fish species, the Siberian sturgeon, Acipenser baerii

The molecular mechanisms underlying testis differentiation in basal actinopterygian fish remains poorly understood. The sex differentiation period was investigated in the Siberian sturgeon, Acipenser baerii, by expression profiling of Sertoli cell transcription factors (dmrt1, sox9) that control testis differentiation in vertebrates; Leydig cell factors (cyp17a1, star) affecting androgen production; the androgen receptor (ar); a growth factor controlling testis development (igf1); and a gene coding for a gonadotropin hormone (lh). Two genes were characterised for the first time in the Siberian sturgeon (dmrt1, cyp17a1), while the others came from public databases. Sturgeon gonad development is very slow, with a late sexual differentiation time during their juvenile stage, and are still immature at 3 years of age. Immature fish showed a sex-dimorphic pattern; all the genes studied displayed a higher expression level in male gonads. We took advantage of the presence of juvenile fish with pre- and post-differentiated gonads (16 and 18 months old) to characterise them at the molecular level. The post-differentiated fish displayed a sex dimorphism of gene expression in their gonads for all genes studied, with the exception of sox9. The trends in undifferentiated fish lead us to propose that sturgeons undergoing male differentiation express high levels of Sertoli cell factors (dmrt1, sox9) and of genes involved in the production and receptivity of androgens (cyp17a1, star and ar) together with lh. Expression profiles and phylogenetic studies suggest that these genes are potential regulators of testis development in the Siberian sturgeon.

Development of a reliable method for determining sex for a primitive rodent, the Point Arena mountain beaver (Aplodontia rufa nigra)

The mountain beaver (Aplodontia rufa) is a primitive species of rodent, often considered a living fossil. The Point Arena mountain beaver (Aplodontia rufa nigra) is an endangered subspecies that occurs in a very restricted range in northern California. Efforts to recover this taxon have been limited by the lack of knowledge on their demography, particularly sex and age-specific vital rates. Recent studies have employed non-invasive genetic sampling to conduct capture-mark-recaptures to estimate abundance, survival and recruitment. Here we report on the development of a method using restriction fragment length polymorphisms to determine sex from tissues, bone and non-invasively collected hair samples for the Point Arena mountain beaver.

Analysis of aminoacids pattern in receptor tyrosine kinase using Boolean association rule.

Cancers are characterized by unrestricted cell division and independency of growth factor and other external signal responsiveness. Eukaryotic parental cells of tumors, on the other hand, constitute tissues and other higher structures like organs and systems and are capable of performing various functions in a highly co-ordinated fashion. Hence, cancer cells may be considered as entities capable of incessant growth and cell division but lacking any evolutionarily advanced intracellular or intercellular regulation. Since receptor tyrosine kinases are highly altered and exist in deregulated/constitutively active forms in cancer cells - achieved through various epigenetic mechanisms - we hypothesize the functional RTKs in cancer cells to resemble their counterparts in more primitive species. Analysis of RTK sequences of various species and of cancer is, therefore, expected to prove this hypothesis. Association rule in data mining can reveal the hidden biological information. This study utilizes the Boolean association rule to mine the occurrence pattern of glycine, arginine and alanine in receptor tyrosine kinases (RTKs) of invertebrates, vertebrates and cancer related vertebrate RTKs based on protein sequence informations. The results reveal that vertebrate cancer RTKs resembles prokaryotes and invertebrate RTKs showing an increasing trend of glycine, alanine and decreasing trend in arginine composition. The aminoacid compositions of vertebrates: invertebrates: prokaryotes: vertebrate cancer with respect to Glycine (>=6.1) were 42.86: 50.0: 85.71: 100%, Alanine (>=6.2) were 10.72: 66.67: 85.71: 100%, whereas Arginine (>=5.9) were 21.43: 16.67: 14.29: 0%, respectively. In conclusion, results from this study supports our hypothesis that cancer cells may resemble lower organisms since functionally cancer cells are unresponsive to external signals and various regulatory mechanisms typically found in higher eukaryotes are largely absent.

Erratum to: Reassessment of the Morphology and Taxonomic Status of the Earliest Herpetotheriid Marsupials of Europe

The earliest Eocene locality of Dormaal (Belgium) has provided the oldest Cenozoic herpetotheriid marsupials of Europe. No herpetotheriid has ever been reported earlier than the Eocene in Europe, except for a questionable single upper molar from the Upper Cretaceous of the Belgian/Dutch border. The systematics of the herpetotheriids of Dormaal was formerly based on only a dozen dental specimens, which were assigned, after several revisions, to two species Peratherium constans and Amphiperatherium brabantense. Most importantly, these two species were considered at the root of most of the hepetotheriid lineages of the European Paleogene. Here we report a large sample of about 400 new dental remains that allow a better definition of both species as well as a testing of their systematic status. The evidence of significant morphological variability leads us to reconsider the diagnosis of Peratherium constans and to question the validity of Amphiperatherium brabantense. This study highlights that the primitive species Peratherium constans and Amphiperatherium brabantense are hardly distinguishable from each other, and therefore conclude that Peratherium constans was the only marsupial present at Dormaal. The important morphological variation exhibited by this herpetotheriid is similar to the variability observed in the type-species Peratherium elegans and in other fossil and extant metatherians. Consequently, our results suggest that several Amphiperatherium species from the Eocene could represent variants of the genus Peratherium. The question of the Amphiperatherium presence in Europe is therefore raised and a thorough discriminate analysis of both genera should be conducted in later works.

Mid-Mesozoic Flea-like Ectoparasites of Feathered or Haired Vertebrates

Parasite-host associations among insects and mammals or birds are well attended by neontological studies [1]. An Eocene bird louse compression fossil [2, 3] and several flea specimens from Eocene and Oligocene ambers [4-8], reported to date, are exceptionally similar to living louse and flea taxa. But the origin, morphology, and early evolution of parasites and their associations with hosts are poorly known [9, 10] due to sparse records of putative ectoparasites with uncertain classification in the Mesozoic, most lacking mouthpart information and other critical details of the head morphology [11-15]. Here we present two primitive flea-like species assigned to the Pseudopulicidae Gao, Shih et Ren familia nova (fam. nov.), Pseudopulex jurassicus Gao, Shih et Ren genus novum et species nova (gen. et sp. nov) from the Middle Jurassic [16] and P. magnus Gao, Shih et Ren sp. nov. from the Early Cretaceous in China [17]. They exhibit many features of ectoparasitic insects. Large body size and long serrated stylets for piercing tough and thick skin or hides of hosts suggest that these primitive ectoparasites might have lived on and sucked the blood of relatively large hosts, such as contemporaneous feathered dinosaurs and/or pterosaurs or medium-sized mammals (found in the Early Cretaceous, but not the Middle Jurassic).

New Micromomyid Plesiadapiforms (Mammalia, Euarchonta) from the Late Paleocene of Big Multi Quarry, Washakie Basin, Wyoming

ABSTRACT The family Micromomyidae includes diminutive plesiadapiforms characterized by highly specialized premolars and relatively primitive molars. Perhaps as a result of their small size, micromomyids show a spotty distribution through space and time, with documented records ranging from the middle Tiffanian of Alberta to the early Wasatchian of Wyoming. The micromomyids of Big Multi Quarry, an early Clarkforkian site in southwestern Wyoming that has yielded the most diverse plesiadapiform fauna known to date, are described here. Dryomomys dulcifer, new species, is the oldest and most primitive species of this rare micromomyid genus currently known. Tinimomys tribos, new species, retains primitive dental features that have been modified in Tinimomys graybulliensis Szalay, 1974. The apparent sympatry shown by Dryomomys and Tinimomys at Big Multi Quarry suggests that these closely related micromomyids occupied distinct ecological niches, although the nature of any such distinctions remains unknown.

Consequences of early chilling stress in two Triticum species: plastic responses and adaptive significance

Phenotypic plasticity of two primitive wheat species (Triticum monococcum L. and Triticum dicoccum S.) was studied in response to early chilling stress. Selection pressure differentials, gradients and plasticity costs on plant morphogenesis, growth and reserve carbohydrate consumption were estimated. Regression analysis was applied to investigate differential developmental changes and patterns between treatments. Four-day-old seedlings of T.monococcum and T.dicoccum, differing in plant stature and reserve carbohydrates, were given an early chilling temperature (4 °C for 42 day) and compared with control plants grown at 23 °C. Early chilling stress resulted in a significant increase in leaf mass ratio (LMR) and relative growth rate (RGR), a reduction in flag leaf size, total biomass, specific leaf area (SLA) and reserve carbohydrate storage at flowering, together with advanced onset of flowering. Selection pressure within the early chilling environment favoured early flowering, smaller SLA, higher LMR and lower reserve carbohydrates, suggesting the observed responses were adaptive. Furthermore, a regression of daily cumulative plant biomass derived from a crop growth simulation model (CERES-Wheat) on crop vegetation period revealed a divergent developmental pattern in early-chilled plants. Using selection pressure gradient analysis, we found similar responses among these traits, except for SLA and sucrose, indicating that these two traits have indirect effects on fitness. Thus, the total effects of SLA and reserve sucrose on relative fitness seem to be buffered via the rapid growth rate in chilled plants. While lower SLA may reduce early chilling stress effects at an individual leaf level, a higher LMR and use of reserve carbohydrates indicated that compensatory growth of chilled plants during the recovery period relied on the concerted action of altered resource allocation and reserve carbohydrate consumption. However, a significant cost of plasticity was evident only for flowering time, LMR and fructan levels in the early chilling environment. Our results demonstrate that morphological and intrinsic developmental (ontogenetic) patterns in two Triticum species respond to early chilling stress.

Una nueva especie de <i>Agriarctos</i> (Ailuropodinae, Ursidae, Carnivora) en la localidad de Nombrevilla 2 (Zaragoza, España)

Una nueva especie de úrsido primitivo, Agriarctos beatrix procedente de la localidad de Nombrevilla 2 (Zaragoza, cuenca de Calatayud-Daroca) es descrita en este trabajo. Los nuevos fósiles de Nombrevilla 2 se relacionan estrechamente con Agriarctos depereti de la localidad de Soblay (Vallesiense superior, Francia), pero en la forma española los caracteres derivados compartidos son más primitivos. Agriarctos beatrix es la primera aparición conocida hasta el presente de un miembro de la subfamilia Ailuropodinae en el registro fossil.

Phylogeny and Relationships of the Mountain Lizards of Europe and Near East ( Archaeolacerta Mertens, 1921, sensu lato ) and Their Relationships Among the Eurasian Lacertid Radiation

Archaeolacerta s. l., in the currently utilized sense results to be a polyphyletic taxon, composed of three monophyletic and phylogenetically well differentiated taxa: a) Archaeolacerta (s. str.) Mertens, 1921, which includes three species: A. bedriagae , A. oxycephala , and A. mosorensis , distributed by the northern part of the Central Mediterranean (Corsica, Sardinia, and west Balcanic Peninsula). His most related genera seem to be Teira (his adelphotaxon in our study), Apathya , and Omanosaura . b) Iberolacerta gen. nov., with two subgenera: Iberolacerta s. str. and Pyrenesaura subgen. nov. includes six species: I. monticola , I. cyreni , I. bonnali , I. aranica , I. aurelioi , and I. horvathi . They are distributed by the mountains of Western Europe (Iberian Peninsula, Pyrenees, Central and Eastern Alps and the north of the Dinaric Chains). His adelphotaxon are the Caucasian and Near East species of Darevskia gen. nov. c) The third taxa is Darevskia gen. nov., which includes the species of the « L». saxicola complex besides « L». derjugini , « L». praticola , and « L». chlorogaster . They are distributed by Eastern Europe, Caucasus, and Near East. Other clear relationships among some taxa of the Eurasian Radiation [= «Eurasische linie» from (Mayer and Benyr, 1994)] have been found: Algyroides seems to be the sister group of the species considered of uncertain phylogenetic relationships belonging to the « L». danfordi-laevis group and of Podarcis . « L». brandtii seems to be a very primitive species within the Eurasian Radiation. Omanosaura and Apathya appear as sister taxa. « L». graeca occupies a very basal position in the sister group of Podarcis and relatives (see above). « L». andreanskyi is the sister species of the Darevskia nov. and Iberolacerta nov. clade. The assimilation of « L». andreanskyi to Teira is very problematic. Also the « L». parva group seems to be related to Timon . Some groups of species like « L». brandtii , « L». parva-fraasii and « L». danfordi-laevis probably merit generic rank, but it is necessary a more deep study before to take a decision.

Oldest known pantherine skull and evolution of the tiger.

The tiger is one of the most iconic extant animals, and its origin and evolution have been intensely debated. Fossils attributable to extant pantherine species-lineages are less than 2 MYA and the earliest tiger fossils are from the Calabrian, Lower Pleistocene. Molecular studies predict a much younger age for the divergence of modern tiger subspecies at <100 KYA, although their cranial morphology is readily distinguishable, indicating that early Pleistocene tigers would likely have differed markedly anatomically from extant tigers. Such inferences are hampered by the fact that well-known fossil tiger material is middle to late Pleistocene in age. Here we describe a new species of pantherine cat from Longdan, Gansu Province, China, Panthera zdanskyi sp. nov. With an estimated age of 2.55–2.16 MYA it represents the oldest complete skull of a pantherine cat hitherto found. Although smaller, it appears morphologically to be surprisingly similar to modern tigers considering its age. Morphological, morphometric, and cladistic analyses are congruent in confirming its very close affinity to the tiger, and it may be regarded as the most primitive species of the tiger lineage, demonstrating the first unequivocal presence of a modern pantherine species-lineage in the basal stage of the Pleistocene (Gelasian; traditionally considered to be Late Pliocene). This find supports a north-central Chinese origin of the tiger lineage, and demonstrates that various parts of the cranium, mandible, and dentition evolved at different rates. An increase in size and a reduction in the relative size of parts of the dentition appear to have been prominent features of tiger evolution, whereas the distinctive cranial morphology of modern tigers was established very early in their evolutionary history. The evolutionary trend of increasing size in the tiger lineage is likely coupled to the evolution of its primary prey species.

Genetic relationships among loquat cultivars and some wild species of the genus Eriobotrya based on the internal transcribed spacer (ITS) sequences

The phylogenetic relationships among seven wild species and 25 loquat cultivars of genus Eriobotrya were studied by comparing sequences of the internal transcribed spacer (ITS) region. The length of ITS1 region of Eriobotrya was 223 bp and the lengths of ITS2 were ranged from 201 bp to 203 bp. The G + C contents varied from 64.1% to 65.5% in ITS1 and from 68.5% to 72.1% in ITS2. The aligned sequences were analyzed by neighbor-joining (NJ) and maximum parsimony (MP) methods. The ITS1 spacer region comprised 223 characters, of which 44 were variable sites and 34 were parsimony informative sites. The NJ tree had very similar topology to the MP tree. E. malipoensis and E. seguinii had only one different character in ITS2 region and both of them could be the most primitive species of Eriobotrya genus. ITS2 evolved much faster and had more parsimony informative sites than ITS1. ITS2 presented much more precise information about the phylogenetic relationships. Based on ITS2 regions, the evolution order of the studied taxa in this paper could be concluded, which was E. bengalensis f. angustifolia, E. prinoides var. dadunensis, E. prinoides ( E. bengalensis), E. dayaoshanensis and E. japonica Lindl.

P2X receptor homologs in basal fungi

P2X receptor homologs in basal fungi

Five million years of pocket gopher history in the Meade Basin of southwestern Kansas and northwestern Oklahoma

ABSTRACT The Meade Basin record of pocket gophers extends from the latest Miocene (Buis Ranch local fauna) to modern time. A primitive species with hypsodont but rooted cheek teeth, Pliogeomys buisi, characterizes the late Hemphillian. Another species of Pliogeomys, P. louderbachi, is described here as a new species from the early Blancan. It is intermediate in dental and mandibular morphology between Pliogeomys and Geomys. The Geomys minor (= G. smithi) lineage displays a stepped dwarfing trend prior to its extinction, whereas the G. jacobi lineage demonstrates an overall pattern of stasis in size. G. jacobi is replaced by G. quinni at the end of the Pliocene, within which there is a significant directional size increase. A late Pliocene immigrant, the new species G. floralindae, appears in the Sanders assemblage. It is briefly replaced by an indeterminate small species in the Nash 72 local fauna. G. tobinensis is found in the Cudahy local fauna. Morphologically modern G. bursarius appears in the Meade Basin during the early Rancholabrean. A small, primitive species, Geomys adamsi, appears only during the early Pliocene at Fox Canyon, and transient Thomomys appear at various times during the Pleistocene, both apparently during cold intervals. A phylogenetic analysis suggests two clades, one uniting Pliogeomys russelli and Geomys adamsi and another including the remaining Meade Basin geomyines. Enhanced species turnover and the last push for modern mandibular morphology is most pronounced in sediments younger than about 2.6 million years ago, corresponding to the first global cooling heralding the Pleistocene.

New Brontotheriidae (Mammalia, Perissodactyla) from the early and middle Eocene of Pakistan with implications for mammalian paleobiogeography

Brontotheriids are common in Eocene faunas of North America and Asia but are poorly known from the Indian subcontinent. Here we describe three new late early Eocene brontotheriids from Pakistan, found in the upper part of the upper Ghazij Formation and representing the oldest Asian brontotheres. Eotitanops pakistanensis n. sp. is a small, primitive species, Balochititanops haqi n. gen. n. sp. is slightly larger and more derived, and fragmentary specimens identified as cf. Balochititanops sp. appear to represent a third, larger taxon.Improved knowledge of early brontotheres from North America permits better taxonomic resolution of some middle Eocene brontothere remains from Pakistan. ‘Eotitanops’ dayi from the Kuldana Formation is shown to be closer to Palaeosyops and is renamed Palaeosyops dayi n. comb. A new astragalus from the Baska Formation probably represents Pakotitanops latidentatus. A previously described humerus and a new calcaneum, both from the Subathu Formation, are tentatively referred to Mulkrajanops moghliensis.Phylogenetic interpretation suggests that Eotitanops pakistanensis is as primitive as the North American species of this basal brontothere genus, and also, within the limits of stratigraphic resolution, Eotitanops appeared on both continents at the same time. The origin of brontotheres is therefore equally likely to have been in Asia or in North America. The presence of the primitive brontotheres Eotitanops and Palaeosyops in Indo-Pakistan and North America indicates faunal exchange, almost certainly through Asia, although the direction of dispersal cannot be determined. The postulated high-latitude exchange coincides with a warm interval known as the Early Eocene Climatic Optimum.

Genome-wide analysis of plastome sequence variation and development of plastidial CAPS markers in common potato and related Solanum species

The plastome sequence of the European cultivated potato, Solanum tuberosum subsp. tuberosum (tbr, GenBank accession no. DQ386163), was compared with that of S. bulbocastanum, a wild potato relative (blb, GenBank accession no. DQ347958), in order to characterize the degree and type of variability in different genomic regions, and develop molecular markers relevant to genetics, breeding and biotechnology of potato. One hundred forty-two and 251 PICs (Potentially Informative Characters) were found in coding and non-coding sequences (NCSs), respectively. Further, while variation in coding regions was almost exclusively due to nucleotide substitutions, 25% of PICs in NCSs of tbr and blb were due to indels, most of them mononucleotide or longer tandem repeats (micro and minisatellites). Four intergenic regions were selected for further analyses in other 16 tuber-bearing Solanum species. The rps16-trnQ UUG gene spacer was found to be the most variable, forty-six PICs in this region distinguishing 18 haplotypes. Analysis of haplotype relationships, based on variability in the four intergenic regions, confirmed that the most primitive species from Central America were the most distant to S. tuberosum. Finally, polymorphic sites in the same regions were used to develop a set of CAPS (Cleaved Amplified Polymorphic Sequences) markers for species/cytoplasm identification in Solanum spp.

THE LATE CRETACEOUS GENERA CUVILLIERINELLA, CYCLOPSEUDEDOMIA, AND RHAPYDIONINA (RHAPYDIONINIDAE, FORAMINIFERIDA) IN SHALLOW-WATER CARBONATES OF PYLOS (PELOPONNESE, GREECE)

Shell architectures of the larger foraminiferal genera Cuvillierinella , Cyclopseudedomia , and Rhapydionina were studied by comparing topotypes of previously described species with new specimens retrieved from Late Cretaceous shallow-water carbonates of Pylos (Peloponnese, Greece), where the three genera are found in association. The megalospheric generation of each genus exhibits a distinctive shell shape in adult specimens (i.e., fan-shaped in Cyclopseudedomia , conical in Rhapydionina , and cylindrical in Cuvillierinella ). Although their microspheric adults are similarly thin, flat, and discoidal, they can be identified at the genus level by means of a detailed structural analysis. Cuvillierinella shows the septula to be interrupted by a large preseptal space, while Cyclopseudedomia and Rhapydionina exhibit continuous, non-interrupted septula. In addition, Cyclopseudedomia presents only one row of medullar chamberlets, whereas Rhapydionina shows numerous medullar chamberlets distributed in a thick basal layer. Two new species, Cuvillierinella pylosensis and Rhapydionina fleuryi , are described. The former is a more complex taxon than the type species, C. salentina , while the latter corresponds to a more primitive species, R. liburnica . Strontium-isotope stratigraphy indicates an uppermost Campanian–lowermost Maastrichtian age for these new species.

Sex pheromone desaturase functioning in a primitive Ostrinia moth is cryptically conserved in congeners’ genomes

(E)-11- and (Z)-11-tetradecenyl acetate are the most common female sex pheromone components in Ostrinia moths. The Δ11-desaturase expressed in the pheromone gland (PG) of female moths is a key enzyme that introduces a double bond into pheromone molecules. A single Δ11-desaturase of Ostrinia nubilalis, OnubZ/E11, has been shown to produce an ∼7:3 mixture of (E)-11- and (Z)-11-tetradecenoate from the substrate tetradecanoate. In contrast, the sex pheromone of Ostrinia latipennis, a primitive species of Ostrinia, is (E)-11-tetradecenol. This pheromone is unique in that it is not acetylated, and includes no Z isomer. In the present study, through the cloning and functional analysis of a PG-specific Δ11-desaturase in O. latipennis, we showed that the absence of the Z isomer in the pheromone is attributable to the strict product specificity of the Δ11-desaturase in this species, LATPG1. Phylogenetic analysis revealed that LATPG1 was not closely related to OnubZ/E11. Rather, it was closely related to retroposon-linked cryptic Δ11-desaturases (ezi-Δ11) found in the genomes of O. nubilalis and Ostrinia furnacalis. Taken together, the results showed that an unusual Δ11-desaturase is functionally expressed in O. latipennis, although the genes encoding this enzyme appear to be cryptic in congeners.

Craniodental Morphology and Systematics of a New Family of Hystricognathous Rodents (Gaudeamuridae) from the Late Eocene and Early Oligocene of Egypt

Background Gaudeamus is an enigmatic hystricognathous rodent that was, until recently, known solely from fragmentary material from early Oligocene sites in Egypt, Oman, and Libya. Gaudeamus' molars are similar to those of the extant cane rat Thryonomys, and multiple authorities have aligned Gaudeamus with Thryonomys to the exclusion of other living and extinct African hystricognaths; recent phylogenetic analyses have, however, also suggested affinities with South American caviomorphs or Old World porcupines (Hystricidae).Methodology/Principal FindingsHere we describe the oldest known remains of Gaudeamus, including largely complete but crushed crania and complete upper and lower dentitions. Unlike younger Gaudeamus species, the primitive species described here have relatively complex occlusal patterns, and retain a number of plesiomorphic features. Unconstrained parsimony analysis nests Gaudeamus and Hystrix within the South American caviomorph radiation, implying what we consider to be an implausible back-dispersal across the Atlantic Ocean to account for Gaudeamus' presence in the late Eocene of Africa. An analysis that was constrained to recover the biogeographically more plausible hypothesis of caviomorph monophyly does not place Gaudeamus as a stem caviomorph, but rather as a sister taxon of hystricids.Conclusions/SignificanceWe place Gaudeamus species in a new family, Gaudeamuridae, and consider it likely that the group originated, diversified, and then went extinct over a geologically brief period of time during the latest Eocene and early Oligocene in Afro-Arabia. Gaudeamurids are the only known crown hystricognaths from Afro-Arabia that are likely to be aligned with non-phiomorph members of that clade, and as such provide additional support for an Afro-Arabian origin of advanced stem and basal crown members of Hystricognathi.

New Species of Cricetid Rodents (Mammalia) from the Late Miocene (Hemphillian) Previously Referred toPeromyscus pliocenicusWilson

ABSTRACT Specimens previously identified as the Hemphillian cricetid Basirepomys pliocenicus (Wilson, 1937) (=Peromyscus pliocenicus Wilson, 1937) by Korth and De Blieux (2010) have been re-examined, and several distinct species are here recognized. Specimens from the early Hemphillian Rome fauna of Oregon are referred to a new, more primitive species of Basirepomys Korth and De Blieux, 2010, here named Basirepomys romensis, new species, which differs from other species of the genus in having lower-crowned cheek teeth and incomplete alternation of cusps on some molars. Specimens from the early Hemphillian Juniper Creek and Little Valley faunas of Oregon are referable to Paronychomys Jacobs, 1977, rather than Basirepomys, and represent a new species, Paronychomys shotwelli, which is distinguished from other species of the genus by its larger size and relatively longer lower third molar. A specimen previously referred to Peromyscus pliocenicus from the early Hemphillian of Kansas is referable to Paronychomy...

The Roles and Evolutionary Patterns of Intronless Genes in Deuterostomes

Genes without introns are a characteristic feature of prokaryotes, but there are still a number of intronless genes in eukaryotes. To study these eukaryotic genes that have prokaryotic architecture could help to understand the evolutionary patterns of related genes and genomes. Our analyses revealed a number of intronless genes that reside in 6 deuterostomes (sea urchin, sea squirt, zebrafish, chicken, platypus, and human). We also determined the conservation for each intronless gene in archaea, bacteria, fungi, plants, metazoans, and other eukaryotes. Proportions of intronless genes that are inherited from the common ancestor of archaea, bacteria, and eukaryotes in these species were consistent with their phylogenetic positions, with more proportions of ancient intronless genes residing in more primitive species. In these species, intronless genes belong to different cellular roles and gene ontology (GO) categories, and some of these functions are very basic. Part of intronless genes is derived from other intronless genes or multiexon genes in each species. In conclusion, we showed that a varying number and proportion of intronless genes reside in these 6 deuterostomes, and some of them function importantly. These genes are good candidates for subsequent functional and evolutionary analyses specifically.