Serial homology of the mandible and maxilla in the jumping bristletail Pedetontus unimaculatus Machida, based on external embryology (Hexapoda: Archaeognatha, Machilidae)

The development of the mandible and maxilla is examined with the scanning electron microscope in the Archaeognatha. Serial homology is discussed to elucidate the general construction of the hexapod mandible. The part comparable to the maxillary palp does not develop in the mandible. Thus, the mandible is coxopodal in origin, and not telognathic but coxognathic. The mandible proper is subdivided into two in late embryonic development, and the smaller proximal and larger distal parts are homologized with the maxillary cardo and stipes, respectively, being subcoxal and coxal in nature. The partition into the "mandibular cardo" in which the mandibular monocondyle is formed and the "mandibular stipes" is recognized as a cuticular ridge or the "mandibular basal ridge" in the postembryonic stages including the imaginal. The molar and incisor are comparable in position and homologized with the maxillary lacinia and galea, respectively. The lacinia and galea could be morphologically interpreted as being the endites of the maxillary coxae I and II, respectively, and the molar and incisor might represent the mandibular coxae I and II as their constituents or endites.     

New facial measurement used in the determination of palatine index and thickness of the mandibular body index

Measurements of the height of the mandibular body and the length of the palate rest on the assumption that the alveolar parts of the mandible and maxilla are not altered. Unfortunately, in the skeletal remains of the past population most of the molar teeth are often antemortem lost and this tooth loss is followed by resorption of the alveolar ridge. A new method of taking mandibular and palate measurements, which could be used in these cases is proposed in the study.     

On the structure and function of the mouthparts of the soil-inhabiting collembolan Folsomia Candida

The fine structure of the mouthparts of the collembolan Folsomia Candida is described, largely on the basis of a study with the scanning electron microscope. The structure of the maxilla and of die mandibular molar plate is clarified and its interpretation corrected. The grinding function, usually attributed to the collembolan molar plate is disputed. This possible change in function of the mouthparts may also mean that these insects play a slightly different role than hitherto believed in the breakdown of the litter and humus in the soil.
An alternative method to replace freeze-drying in the preparation of Collembola, and possibly other small arthropods for scanning electron microscope studies is described.     

Respiratory response of the deep-sea amphipod Stephonyx biscayensis indicates bathymetric range limitation by temperature and hydrostatic pressure

Depth zonation of fauna on continental margins is well documented. Whilst increasing hydrostatic pressure with depth has long been considered a factor contributing significantly to this pattern, discussion of the relative significance of decreasing temperature with depth has continued. This study investigates the physiological tolerances of fed and starved specimens of the bathyal lysianassoid amphipod Stephonyx biscayensis at varying temperature to acute pressure exposure by measuring the rate of oxygen consumption. Acclimation to atmospheric pressure is shown to have no significant interaction with temperature and/or pressure effects. Similarly, starvation is shown to have no significant effect on the interaction of temperature and pressure. Subsequently, the effect of pressure on respiration rate is revealed to be dependent on temperature: pressure equivalent to 2000 m depth was tolerated at 1 and 3°C; pressure equivalent to 2500 m depth was tolerated at 5.5°C; at 10°C pressure equivalent to 3000 m depth was tolerated. The variation in tolerance is consistent with the natural distribution range reported for this species. There are clear implications for hypotheses relating to the observed phenomenon of a biodiversity bottleneck between 2000 and 3000 metres, and for the potential for bathymetric range shifts in response to global climate change.     

Description de Falklandia gen.n. de I'Ocean Austral et définition des Lysianassoidea uristidiens (Crustacea, Amphipoda)

The revision of the antarctic–subantarctic species Orchomenopsis reducta Schellenberg, 1931, has led to its attribution to a new, highly apomorphic genus: Falklandia gen.n. A new definition of the uristid group is given and Falklandia with 36 other lysianassoid genera are attributed to this supposedly monophyletic group.     

Revision of the genus Noculacia Mayer, 1903 (Crustacea: Amphipoda: Caprellidea) with the description of two new species

The genus Noculacia Mayer, 1903 is reviewed. Two new species, N. africana n. sp. and N. australiensis n. sp., are described based on material collected from southeast Africa and western-southern Australia, respectively. Noculacia bullata Mayer, 1903, the type species of the genus, is redescribed. Noculacia bogisa Mayer, 1903 is transferred to the genus Pseudoprotella Mayer, 1890 mainly on the basis of the presence of a well developed molar, the structure of pereopods 3 and 4, and the setal formula of the mandibular palp being 2-x-1. The genus Noculacia is presently composed of three species: N. africana n. sp., N. australiensis n. sp, and N. bullata Mayer, 1903. The genus Pseudoprotella is composed of P. bogisa (Mayer, 1903), P. inermis Chevreux, 1927, and P. phasma (Montagu, 1804).     

The Mouthparts in Some North Atlantic Species of the Genus Orchomene Boeck (Crustacea, Amphipoda)

The mouthparts of five North Atlantic species of the genus Orchomene have been studied in detail. The species are: O. serrata (Boeck, 1861), O. amblyops G. O. Sars, 1890, O. crispata (Goes, 1866). O. humilis (A. Costa, 1853) and O. pectinate. G. O. Sars, 1882. The structure of the mandibular molar has been studied with the aid of the scanning electron microscope. Some features of the mouthparts, common to the species examined, are interpreted as generic criteria which should justify retaining the genus Orchomene Boeck, 1870, separated from the closely related genera OrchomeneUa G. O. Sars, 1890, and Orchomenopsis G. O. Sars. 1891.     

Temporospatial cell interactions regulating mandibular and maxillary arch patterning

The cellular origin of the instructive information for hard tissue patterning of the jaws has been the subject of a long-standing controversy. Are the cranial neural crest cells prepatterned or does the epithelium pattern a developmentally uncommitted population of ectomesenchymal cells? In order to understand more about how orofacial patterning is controlled we have investigated the temporal signalling interactions and responses between epithelium and mesenchymal cells in the mandibular and maxillary primordia. We show that within the mandibular arch, homeobox genes that are expressed in different proximodistal spatial domains corresponding to presumptive molar and incisor ectomesenchymal cells are induced by signals from the oral epithelium. In mouse, prior to E10, all ectomesenchyme cells in the mandibular arch are equally responsive to epithelial signals such as Fgf8, indicating that there is no pre-specification of these cells into different populations and suggesting that patterning of the hard tissues of the mandible is instructed by the epithelium. By E10.5, ectomesenchymal cell gene expression domains are still dependent on epithelial signals but have become fixed and ectopic expression cannot be induced. At E11 expression becomes independent of epithelial signals such that removal of the epithelium does not affect spatial ectomesenchymal expression. Significantly, however, the response of ectomesenchyme cells to epithelial regulatory signals was found to be different in the mandibular and maxillary primordium. Thus, whereas both mandibular and maxillary arch epithelia could induce Dlx2 and Dlx5 expression in the mandible and Dlx2 expression in the maxilla, neither could induce Dlx5 expression in the maxilla. Reciprocal cell transplantations between mandibular and maxillary arch ectomesenchymal cells revealed intrinsic differences between these populations of cranial neural crest-derived cells. Research in odontogenesis has shown that the oral epithelium of the mandibular and maxillary primordia has unique instructive signaling properties required to direct odontogenesis, which are not found in other branchial arch epithelia. As a consequence, development of jaw-specific skeletal structures may require some prespecification of maxillary ectomesenchyme to restrict the instructive influence of the epithelial signals and allow development of maxillary structures distinct from mandibular structures.     

Function and functional groupings of the complex mouth apparatus of the squat lobsters Munida sarsi Huus and M. tenuimana G.O. Sars (Crustacea: Decapoda).

Like all other decapods, the anomuran squat lobsters Munida sarsi and M. tenuimana have a mouth apparatus composed of six pairs of mouthparts plus labrum and paragnaths (upper and lower lips). To study the functional significance of this complexity, we examined the mouthparts with scanning electron microscopy and also observed their function directly, under laboratory conditions, using macro-video equipment. No differences were found between the two species. The movement patterns of the mouthparts are described in detail and illustrated as serial drawings. Proceeding from maxillipeds 3 towards the mandibles, the movement pattern gets increasingly stereotypical, with the mandibles performing but a single movement in a medio-lateral plane. From morphology, the mouthparts are subdivided into 20 parts, but from the functional analyses the 20 parts form 8 functional groups: 1, transporting mouthparts (maxilliped 2 endopod and maxilliped 3 endopod); 2, transporting-aligning mouthparts (maxilliped 1 basis); 3, sorting-aligning mouthparts (maxilla 1 basis and maxilla 2 basis); 4, current-generating mouthparts (flagella of maxilliped 2 and maxilliped 3 exopods); 5, cutting-crushing mouthparts (incisor and molar processes, labium, and mandibular palp); 6, ingesting mouthparts (maxilla 1 coxa, maxilla 2 coxa, and maxilliped 1 coxa); 7, respiratory mouthparts (scaphognathite, maxilliped 1 epipod, and maxilliped 2 and maxilliped 3 exopods); and 8, dorso-ventral mouthparts (maxilla 1 endopod, maxilla 2 endopod, maxilliped 1 endopod, and maxilliped 1 exopod). These groupings apply mostly to the processes of food handling and have little significance with respect to grooming. When comparing our results to the literature on other decapods, we found much resemblance to conditions in other anomurans.     

Third molar agenesis in human prehistoric populations of the Canary Islands

The occurrence of third molar agenesis was recorded in a sample of 1,492 maxillary and 1,718 mandibular arches belonging to the prehistoric settlers of the Gan Canaria, Tenerife, and La Gomera Islands (Canary Islands). There were significant sex differences only in the Tenerife sample for the maxilla, the incidence in females being higher than in males. In the Gran Canaria sample, the total frequency (male and female combined) of third molar agenesis (individual count method) was 8.7% for the maxilla and 9.3% for the mandible. In the Tenerife and La Gomera samples, the frequencies were 11.1% and 10.7% for the maxilla and 14.6% and 13.3% for the mandible. In the Tenerife sample, the differences between both jaws were statistically significant. The incidence of missing third molars in the mandible was significantly higher in Tenerife than in Gran Canaria, but the other sample differences were statistically nonsignificant. Bilateral absence of third molars was observed in about two-thirds of the specimens examined. Some correlation between both jaws for the occurrence of third molar agenesis was found. The hypotheses that have been proposed in order to explain third molar agenesis in man are discussed. It is suggested that the loss of the third molar in Homo sapiens could be produced by a heterochronic phenomenon of postdisplacement, as a consequence of the phylogenetic tendency toward the delay of the onset of the third molar formation, and that the genetic factors responsible for the absence of these teeth could be related to the general process of delay in tooth formation.     

云南禄丰晚中新世的长臂猿类化石

本文记述的是在禄丰腊玛古猿化石产地发现的长臂猿类化石,它是一种与上猿较为相似而又具有一些进步性质的长臂猿类。它的发现从根本上改变了晚中新世此类化石记录稀少的状况,使我们对这一时期的长臂猿类有了新的认识;同时,对现生长臂猿起源的研究提供了较为充分的化石依据。鉴于它的形态特征和地史分布,作者把它订为一新属新种Laccopithecusrobussus gen.et sp.nov.     

吉林省中部早白垩世泉头组-原始鸟脚类恐龙

报道了在松辽盆地白垩纪沉积中首次发现的原始鸟脚类恐龙化石,并根据其头部特征建立一新属新种——娇小长春龙(Changchunsaurus parvus gen.etsp.nov.)。化石产于吉林省公主岭市刘房子镇山前泉头组上部紫红色含砾泥质砂岩中,同一层位还产有兽脚类、鳄类、恐龙蛋、哺乳类等化石。娇小长春龙是一种混合了原始的和衍生性状的小型鸟脚类恐龙。它具有某些比多数鸟脚类和头饰龙类要原始的特征,例如,5颗前上颌齿、前上颌骨吻部只有很短一段齿缺、前上颌骨与上颌齿之间的间隙较小、颊齿两侧的釉质对称、前上颌骨腹侧边缘与上颌骨腹侧边缘基本处于同一水平线等。同时,娇小长春龙也具有一些与真鸟脚类类似的进步特征,比如眶前孔小、外下颌孔缺失。娇小长春龙具有颧骨突,这在鸟脚类恐龙中较为罕见,它的颧骨突表面具有鲕状构造,这一特征未见于其他已知鸟脚类。娇小长春龙的前齿骨形态与角龙类接近,腹支明显长于侧支,前齿骨与齿骨的愈合方式同角龙类相似。娇小长春龙的确切系统分类位置需要进一步的工作来确定。     

山西榆社上新世沙鼠化石

本文记述了六件短齿假沙鼠(Pseudomeriones abbreviatus abbreviatus)的上下颌骨,并对在庆阳发现的正型标本和国外有关的新材料做了补充记述和讨论。     

New remains of the dryolestoid mammal <Emphasis Type="Italic">Leonardus cuspidatus</Emphasis> from the Los Alamitos Formation (Late Cretaceous,Argentina)

The great diversity of mammals from the Los Alamitos Formation (Campanian–Maastrichtian) in Río Negro Province, Argentina has provided significant information about the evolution of South American dryolestoids. Among these mammals the alleged dryolestid Leonardus cuspidatus Bonaparte was described based on a fragment of maxilla with four molariforms. A right mandibular fragment with two molariforms from the same site as the maxilla is here assigned to L. cuspidatus. The lower molariforms are compatible in the expected morphology with those from the holotype. Even though referred to Dryolestidae, Leonardus shows unique features: (1) the presence of a huge and dome-like stylocone, disconnected and more centrally placed from the other cusps than in other dryolestoids such as Groebertherium, but contacting the preparacrista in the first preserved molar; (2) the absence of cingulae in both upper and lower molars, the latter being similar in shape to the former; (3) the presence of three roots in at least one of the lower molars, which has only been documented in the mesungulatid Coloniatherium for the m1. These characters confirm the diversity and uniqueness of the South American Mesozoic mammals.     

Association of relatively delayed emergence of mandibular molars with molar reduction and molar position

Among 234 children examined annually from age three to 20 years at the Burlington Growth Centre, there was statistically significant cooccurrence of early and late emergence sequences of the permanent first and second molars relative to the central incisors and second premolars in the same jaw and in both jaws. Alternatively, mandibular molar delay was not accompanied by corresponding maxillary molar delay, and the mandibular molars emerged later than the maxillary molars. This was strongly associated with Angle Class II malocclusion, indicating a relationship between relative time of emergence and relative position of opposing molars. Delay of the mandibular molar relative to the successional teeth or maxillary molars was associated with increased frequency of four cusped first and second molars and agenesis of third molars, indicating a tendency for co-occurrence of delay in timing of molar emergence with reduction in structure of the molars. These relationships were evident even though emergences were affected by early loss of a deciduous second molar which increased M1I1 and M2P2 sequences by earlier emergence of M1 and delayed emergence of P2.     

A revision of Danielssenia perezi Monard, D. paraperezi Soyer, D. eastwardae Coull (Harpacticoida; Paranannopidae) and their transfer to a new genus

The harpacticoid copepod Danielssenia perezi Monard, 1935 is redescribed on the basis of the only available material from the Scilly Isles off south-west Britain. Sentirenia gen. nov is erected because this species exhibits significant differences from the type species Danielssenia typica Boeck, 1872 in the structure of the antennule; the presence of sensory aesthetascs on, and structure of, the mandible, maxillula and maxilla; the form of the female P5; the setation of the swimming legs and details of the sexual dimorphism on the endopod of the male P2. Further, it is shown that the characters by which D. paraperezi Soyer, 1970 was originally distinguished from D. perezi are no longer valid and D. paraperezi is a junior synonym of S. perezi which now assumes a boreo-mediterranean distribution. A re-examination of the type material of D , eastwardae Coull, 1971 shows that this species is identical to S. perezi in the structure of the mouthparts (including the presence of aesthetascs on the mandible, maxillula and maxilla) and setation of P1–P5. However, within the genus Sentirenia, its specific status is maintained by virtue of a 5-segmented female antennule; a difference in the shape of the endopodal lobe of the female P5; the sexually dimorphic characters of the male P2 endopod; and variation in the ornamentation of some appendages.     

New platyrrhine monkeys from the Solimões Formation (late Miocene, Acre State, Brazil)

We report here a new fossil primate from the late Miocene of Brazil. The material consists of a lower first molar and a maxilla with P3-4. The fossils were collected in the Solim?es Formation at the locality of Patos, upper Acre River, Acre State, Brazil. The locality is assigned to the Huayquerian South American Land Mammal Age based on faunal content (late Miocene; dated to between 9 and 6 Ma). The new material is the oldest known occurrence of fossil primates in Brazil and is recognized as a new genus and species, Solimoea acrensis. Solimoea is the oldest known member of the ateline subfamily, which includes the living genera Ateles, Lagothrix, and Brachyteles. By analogy with the molar structures and diets of extant platyrrhines, Solimoea primarily had a diet of fruit, perhaps similar to that of the spider monkey, Ateles. Two other primate teeth described previously from the same formation in Bolivia document the occurrence of alouattines and cebines. One of those specimens is a late Miocene representative of the middle Miocene Colombian genus Stirtonia. The other represents one of the largest known platyrrhine primates, for which is erected a new primate genus, Acrecebus fraileyi.     

下颌第三磨牙拔除中预防下唇麻木和舌麻木的方法探讨

目的:探讨下颌第三磨牙拔除导致下唇和舌麻木的有关因素。方法:按照三种分类标准进行分组。第一种分组:以不同年龄段分成两组。第二种分组:以下颌第三磨牙根尖与下颌神经管的关系分成三组。第三种分组:以不同拔牙方法分为三组。结果:1.下颌第三磨牙拔除后引起下唇麻木和舌麻木与年龄无明显关系。2.460例下颌第三磨牙拔除术后出现下唇麻木31例(占6.74%),其中第二组和第三组占26例(占5.65%),第一组和第二组分别与第三组相比具有统计学意义(P0.05);出现舌神经损伤17例(占3.70%),其中第二组和第三组占14例(占3.04%),第一组和第二组分别与第三组相比具有统计学意义(P0.05)。3.口腔全景片显示的66例下颌第三磨牙根尖与下颌神经管重叠中,CBCT显示根尖多位于下颌神经管舌侧,而跨于下颌神经管最少见。4.拔牙方法越复杂,引起下唇和舌麻木的几率就越大。结论:本组病例的方法评估对拟定合适的治疗方案和安全指导拔牙以降低下唇和舌麻木具有重要的临床意义。     

New evidence of the genus Homo from East Rudolf, Kenya. I

Three new fossil hominid specimens that were recovered in 1970 from the Plio-Pleistocene sediments to the east of Lake Rudolf are described. They include the left side of the body and the symphyseal region of an adult mandible that contains three molar teeth (KNM-ER 730), an edentulous left-sided mandibular fragment (KNM-ER 731) and the shaft of a left femur (KNM-ER 737). The specimens are described in anatomical detail, illustrated and selected measurements given. It is concluded that they should be attributed to the genus Homo sp. indet. Detailed comparative studies will be published in due course.