NEOSELACHIAN SHARK AND RAY TEETH FROM THE VALANGINIAN, LOWER CRETACEOUS, OF WĄWAŁ, CENTRAL POLAND

Abstract:  Valanginian strata at Wąwał in central Poland have yielded the oldest marine neoselachian assemblages from the Cretaceous of Europe. The faunas comprise seven taxa including Heterodontus polonicus sp. nov., an indeterminate orectolobiform, Protolamna sp., Palaeoscyllium sp., Synechodus nitidus , Squatina cranei and Belemnobatis sp. Heterodontus polonicus is recognized primarily by the high amount of reticulate ornamentation on the lower labial side of the anterior teeth. The faunas from Wąwał are numerically dominated by neoselachian genera such as Synechodus , Heterodontus and Belemnobatis that were already well established in the Jurassic. More modern taxa include the oldest recorded occurrence of the true Squatina -lineage, and the presence of Protolamna is one of the earliest undoubted lamniform occurrences so far reported.     

Lamniform Shark Teeth from the Late Cretaceous of Southernmost South America (Santa Cruz Province,Argentina)

Here we report multiple lamniform shark teeth recovered from fluvial sediments in the (Campanian-Maastrichtian) Cerro Fortaleza Formation, Santa Cruz Province, Argentina. This small tooth assemblage is compared to various lamniform sharks possessing similar dental morphologies, including Archaeolamna, Cretalamna, Dwardius, Dallasiella, and Cretodus. Although the teeth share numerous morphological features with the genus Archaeolamna, including a developed neck that maintains a relatively consistent width along the base of the crown, the small sample size and incomplete nature of these specimens precludes definitive taxonomic assignment. Regardless, the discovery of selachian teeth unique from those previously described for the region broadens the known diversity of Late Cretaceous South American sharks. Additionally, the discovery of the teeth in fluvial sandstone may indicate a euryhaline paleobiology in the lamniform taxon or taxa represented by this tooth assemblage.     

REVISION OF THE ARCHOSAUROMORPH REPTILE TRILOPHOSAURUS, WITH A DESCRIPTION OF THE FIRST SKULL OF TRILOPHOSAURUS JACOBSI, FROM THE UPPER TRIASSIC CHINLE GROUP, WEST TEXAS, USA

Abstract: The first abundant, well‐preserved fossils of the unusual archosauromorph reptile Trilophosaurus jacobsi Murry are from an Upper Triassic bonebed in the lowermost Trujillo Formation of the Chinle Group in Borden County, Texas. A nearly complete left side of the skull and incomplete but articulated mandible of a juvenile individual demonstrate that Trilophosaurus jacobsi Murry is referable to Trilophosaurus, so the putative procolophonid genus Chinleogomphius is a junior objective synonym of Trilophosaurus. Features of T. jacobsi that diagnose it from T. buettneri include asymmetrical, tricuspate teeth in which the central cusp is taller than the marginal cusp, polygonal in cross‐section and displaced slightly lingually; the lingual cusp is low, transversely broadened and anteroposteriorly compressed; teeth with prominent cingula along the mesial and distal margins; and paired sagittal (parasagittal) crests composed of portions of the postfrontals and the parietals, as well as a relatively broad skull roof between the supratemporal fenestrae. We also re‐illustrate and re‐describe the holotypes of both Trilophosaurus buettneri Case and T. jacobsi Murry. T. jacobsi is primarily Adamanian in age, and the lowest occurrence of T. jacobsi is stratigraphically above that of T. buettneri. Therefore, T. buettneri is an Otischalkian–Adamanian index taxon, and T. jacobsi is an Adamanian–?earliest Revueltian index taxon. Trilophosaurus teeth are readily identifiable to species and therefore identifiable as isolated fossils.     

Eocene sand tiger sharks (Lamniformes,Odontaspididae) from the Bolca Konservat-Lagerstätte,Italy: palaeobiology,palaeobiogeography and evolutionary significance

Here we report the first record of one of the most common and widespread Palaeogene selachians, the sand tiger shark Brachycarcharias, from the Ypresian Bolca Konservat-Lagerstätte. The combination of dental character of the 15 isolated teeth collected from the Pesciara and Monte Postale sites (e.g. anterior teeth up to 25 mm with fairly low triangular cusp decreasing regularly in width; one to two pairs of well-developed lateral cusplets; root with broadly separated lobes; upper teeth with a cusp bent distally) supports their assignment to the odontaspidid Brachycarcharias lerichei (Casier, 1946), a species widely spread across the North Hemisphere during the early Palaeogene. The unambiguous first report of this lamniform shark in the Eocene Bolca Konservat-Lagerstätte improves our knowledge concerning the diversity and palaeobiology of the cartilaginous fishes of this palaeontological site, and provides new insights about the biotic turnovers that involved the high trophic levels of the marine settings after the end-Cretaceous extinction.     

记甘肃晚侏罗世一蜥蜴新属

本文记述石龙子类 Scincomorpha 蜥蜴的—新属,甘肃拟贝氏蜥 Mimobefklesisaurus gansuensis gen. et sp. nov. 化石发现于甘肃省肃北县马宗山区晚侏罗世的赤金堡群.这是石龙子类化石在我国的第一次发现,也是目前所发现的这类动物在亚洲的最早的代表.     

A new tritylodontid from the Kayenta formation of Arizona

Kayentatherium wellesigen. sp. now is a new tritylodont (Thcrapsida: Synapsida) from the Kayenta Formation of Arizona, U.S.A. Only the skull and parts of the lower jaw are known. The first upper incisor is apparently absent, so the dentition consists of one upper incisor followed, after a diastema, by a row of postcanines, which are replaced posteriorly. The cusp formula of these upper postcanines is 2, 2 (+ a ) 2, a being a tiny mesial cusp. The mean breadth/length ratio of these teeth is 1.59. Kayentatherium is related to the Tritylodon Bienotherium lineage, but is considerably more advanced than the latter, which is of Upper Triassic Lower Jurassic age. This indicates that the Kayenta formation must be Lower or Middle Jurassic age, with agrees with the conclusions of Welles.     

Intercusp relationships of the permanent maxillary first and second molars in American whites

Much of a human molar's morphology is concentrated on its occlusal surface. In view of embryologists' recent attention on the determination of crown morphology by enamel knots that initiate cusp formation, we were interested in the arrangement of cusp apices in the definitive tooth. Computer-assisted image analysis was used to measure intercusp distances and angles on permanent maxillary M1 and M2 in a sample of 160 contemporary North American whites. The intent was to generate normative data and to compare the size and variability gradients from M1 to M2. There is little sexual dimorphism in intercusp distances or angles, even though the conventional mesiodistal (MD) and buccolingual (BL) crown size is 2.0% and 4.0% larger in males, respectively, in these same teeth. Dimensions decreased in size and increased in variability from M1 to M2, but differentially. Cusps of the trigon were more stable between teeth, especially the paracone-protocone relationship. Principal components analysis on the six M1 distances disclosed only one eigenvalue above 1.0, indicating that overall crown size itself is the paramount controlling factor in this tooth that almost invariably exhibits a hypocone. In contrast, four components were extracted from among the 12 angular cusp relationships in M1. These axes of variation may prove useful in studies of intergroup differences. A shape difference occurs in M2, depending on whether the hypocone is present; when absent, the metacone is moved lingually, creating more of an isosceles arrangement for the cusps of the trigon. Statistically, correlations are low between occlusal intercusp relationships and conventional crown diameters measured at the margins of the crowns that form later. Weak statistical dependence between cusp relationships and traditional MD and BL diameters suggest that separate stage- and location-specific molecular signals control these different parts (and different stages) of crown formation.     

Pathologic tooth deformities in modern and fossil chondrichthians: a consequence of feeding-related injury

Deformed teeth are found as rare components of the dentitions of both modern and fossil chondrichthians. Tooth deformities occur as bent or twisted tooth crowns, missing or misshaped cusps, atypical protuberances, perforations, and abnormal root structures. Deformed tooth files consisting of unusually overlapped or small teeth, or teeth misaligned in the jaw also occur in modern forms, but deformed tooth files generally are not recognizable in fossils due to post-mortem dissociation of teeth and jaws. A survey of 200 modern lamniform and carcharhiniform sharks as well as literature sources indicate that such deformities are produced by feeding-related injury to the tooth-forming tissue of the jaws, particularly by impaction of chondrichthian and teleost fin and tail spines. Tooth counts for several late Cretaceous genera, based on material recovered from coastal plain sites from New Jersey to Alabama, suggest that the frequency of occurrence of deformed teeth in a species varies from about 0.015% in Squalicorax kaupi to about 0.36% in Paranomotodon sp. Tooth counts for modern lamniform and carcharhiniform sharks yield a comparable range in frequency of tooth deformities. Variation in frequency of tooth deformity may reflect interspecific differences in feeding behavior and dietary preferences. There is no suggestion in our data of any strong patterns of temporal variation in tooth deformity frequency, or of patterns ­reflecting chondrichthian phylogenetic history and evolution. Skeletal components of the probable prey of the Cretaceous species are preserved in the same horizons as the deformed teeth, and also are found within co-occurring chondrichthian coprolites.     

A Gigantic Shark from the Lower Cretaceous Duck Creek Formation of Texas

Three large lamniform shark vertebrae are described from the Lower Cretaceous of Texas. We interpret these fossils as belonging to a single individual with a calculated total body length of 6.3 m. This large individual compares favorably to another shark specimen from the roughly contemporaneous Kiowa Shale of Kansas. Neither specimen was recovered with associated teeth, making confident identification of the species impossible. However, both formations share a similar shark fauna, with Leptostyrax macrorhiza being the largest of the common lamniform sharks. Regardless of its actual identification, this new specimen provides further evidence that large-bodied lamniform sharks had evolved prior to the Late Cretaceous.     

Enigmatic teeth from the Jurassic–Cretaceous transition of Morocco: The latest known non-mammaliaform cynodonts (Synapsida,Cynodontia) from Africa?

Two tooth morphotypes corresponding to one or two tetrapod species from the Late Jurassic or Earliest Cretaceous locality of Ksar Metlili (KM), Anoual Syncline (eastern Morocco), are reported and described. These teeth cannot be related to any of the identified vertebrate major groups of this site. They are tricusped and uniradiculate, with a high and large main central cusp mesio-distally surrounded by two smaller accessory cusps. Their morphology is reminiscent of several taxa such as pterosaurs, notosuchians and mammals, with which they are compared here. These morphotypes are tentatively referred to cf. Cynodontia indet. They would be the most recent non-mammaliaform cynodonts reported in Africa and among the latest described. The KM specimens display remarkable plesiomorphic dental features with respect to known contemporaneous non-mammaliaform cynodonts. They might indicate the survival of a relict lineage in a North African refugium.     

The mineralization and hardness of the radular teeth of the limpet Patella vulgata L.

Summary A study of the Patella vulgata radula has been made using: the scanning electron microscope in its normal and compositional contrast modes of operation, the electron microprobe analyser, ion etching with argon ions and microhardness testing.Only iron, silicon and small amounts of sulphur were detected in the radula. The teeth can be subdivided into a cusp, a junctional area where the cusp is joined to the base, and the base which is embedded in the radular membrane. From a study of longitudinal vertical and transverse sections of the mature teeth it was found that the cusp could be subdivided into a posterior iron-rich area (44–51% Fe, 1–6% Si) and an anterior silicon-rich area (22–30% Fe, 27–32% Si). The junctional zone consisted of a poorly mineralised layer at its border with the cusp and an iron-rich layer where it joined the base. The upper part of the base (5% Fe, 16% Si) could be clearly differentiated from the silicon-rich anterior and lower parts of the base (3–4% Fe, 28–35% Si). No minerals were detected in the membrane. The changes in the mineral content of the teeth cusps along the length of the radula were studied. Iron appeared in the cusps at the 25th row and the concentration increased to 28% at the 50th row. The iron was here evenly distributed throughout the cusp. Silicon appeared in the anterior part of the cusp at the 50th row and as it increased in concentration so the iron was displaced, and at the same time the concentration of iron increased in the posterior part of the cusp. Mineralization appeared to be complete by the 150th row.The teeth cusps appear to consist of 800 Å fibres grouped into 1 thick bundles and the tooth appears to be covered by a thin enamel-like layer. It is suggested that the fibres contain the silicon-rich phase and the matrix the iron-rich phase.The significance of the arrangement of the fibres and the distribution of the minerals are discussed with relation to the function of the teeth.We wish to thank Mr. A. Rees and Mr. A. Davies for their technical assistance; Prof. Lewis and Dr. James for the use of the Electron Microprobe; and the S.R.C. for their financial support.     

Tooth development and histology patterns in lamniform sharks (Elasmobranchii,Lamniformes) revisited

The dentition of lamniforme sharks exhibits several characters that have been used extensively to resolve the phylogenetic relationships of extant taxa, yet some uncertainties remain. Also, the development of different teeth of a tooth file within the jaws of most extant lamniforms has not been documented to date. High‐resolution micro‐computed tomography is used here to re‐evaluate the importance of two dental characters within the order Lamniformes, which were considered not to be phylogenetically informative, the histotype and the number of teeth per tooth file. Additionally, the development and mineralization patterns of the teeth of the two osteodont lamniforms Lamna nasus and Alopias superciliosus were compared. We discuss the importance of these dental characters for phylogenetic interpretations to assess the quality of these characters in resolving lamniform relationships. The dental characters suggest that (1) Lamniformes are the only modern‐level sharks exhibiting the osteodont histotype, (2) the osteodont histotype in lamniform sharks is a derived state in modern‐level sharks (Elasmobranchii), (3) the osteodont type, conversely is convergently achieved when the clade Chondrichthyes is considered and thus might comprise a functional rather than a phylogenetic signal, and (4) there is an increase in the number of teeth per file throughout lamniform phylogeny. Structural development of the teeth of L. nasus and A. superciliosus is congruent with a previous investigation of the lamniform shark Carcharodon carcharias. J. Morphol. 277:1584–1598, 2016. © 2016 Wiley Periodicals, Inc.     

A new Early Cretaceous lamniform shark (Chondrichthyes,Neoselachii)

Eoptolamna eccentrolopha gen. et sp. nov. (Chondrichthyes, Lamniformes) from the near coastal upper Barremian Artoles Formation (Early Cretaceous) of Castellote (northwestern Spain) is described on the basis of about 50 isolated teeth. This taxon represents one of the earliest lamniform sharks known to date. We hypothesize that most pre‐Aptian lamniforms belong to an ancient group characterized, amongst others, by a very weak gradient monognathic heterodont dental pattern, and by tearing‐type dentition. There is a nutritive groove in the lingual root protuberance in juveniles of Eoptolamna, which persists in adults. A single pair of symphysial and a pair of upper intermediate teeth might have been present. Consequently, a new family, Eoptolamnidae, is introduced to include the new form, as well as Protolamna and probably Leptostyrax. The Eoptolamnidae represent an ancient family within Lamniformes. The origin of lamniform sharks remains, however, ambiguous despite recent advances. The new Spanish taxon is widespread in the Barremian of north‐eastern Spain, and occurs in a wide range of facies from near‐coastal to lake deposits. This lamniform also occurs in the Lower Cretaceous of northern Africa. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 278–290.     

Age-related variability in occlusal wear planes

Investigation of two populations of 136 individuals shows several patterns of occlusal wear plane change which are positively correlated with age. For individuals up to the age of 18, there is a characteristic pattern in which the occlusal wear planes of the mandibular teeth are lingually sloped and those of the maxillary dentition buccally sloped, with the exception of the maxillary premolars, which are also lingually sloped. The long axes of the mandibular teeth give them a lingual orientation relative to the maxillary teeth, and the long axes of the maxillary molars, by contrast, are buccally oriented. In the 18-30 age range for all sexes, the mandibular M1 becomes buccally sloped on its occlusal surface while the occlusal wear plane on the maxillary M1 becomes lingually sloped. Later age changes indicate a trend for the mandibular premolars to become buccally sloped, while the wear planes of the maxillary premolars remain lingually sloped. There is a corresponding tendency for the maxillary and mandibular second molars to undergo changes in the initial orientation of the occlusal wear planes.     

湖北长阳青铜时代人类乳齿特征的研究

对在湖北长阳县深潭湾崖葬墓出土的青铜时代人类乳齿形态特征的观察研究显示在人类恒齿出现的大多数具有种族识别价值的形态特征在乳齿有相等程度的表现,其中部分特征的出现率和表现程度高于恒齿。与其他地区人群相比,长阳青铜时代人类乳齿特征在总体上与东北亚人类具有的“中国型牙齿”特征接近。同时,在个别牙齿特征上呈现出南亚蒙古人种的特点。作者对产生这种现象的原因进行了分析。本文还就长阳青铜时代人类乳齿测量数据的表现特点进行了探讨。     

全新世中国北方人群第一臼齿齿冠面积和齿尖相对面积的测量分析

通过对532枚中国北方地区新石器时代到青铜时代和铁器时代人类上、下颌骨第一臼齿(M1和M1)齿冠面积和齿尖面积的测量和分析, 得到以下关于中国北方近代人群牙齿尺寸的准确数据和变异情况的结果: 两性M1和M1齿冠面积存在显著性差异, 男性齿冠面积大于女性齿冠面积, 齿尖相对面积不存在性别差异; 从新石器时代到青铜时代男性M1和M1分别缩小了1.16%和4.96%, 女性分别缩小了5.68%和6.11%,青铜时代到铁器时代齿冠面积无明显变化; M1颊侧尖相对基底面积大于舌侧尖, 形成齿尖大小差异的原因很可能是在人类演化过程中, 齿冠面积整体缩小的趋势下, 为使咬合面最大化使用, 各齿尖朝着更利于扩大咬合面基底面积的方式进化的结果; 世界各地区近代人群M1和M1各齿尖大小顺序基本一致, 其中M1为原尖>前尖>后尖>次尖, M1下原尖最大, 下次小尖最小, 其他三个齿尖面积非常接近, 不存在明显大小变化。     

嫁[虫戚]的齿舌带及其齿片的形态差异分析

在光镜和电镜下对嫁[虫戚]（Cellana toreuma）的齿舌形态进行观察研究。嫁[虫戚]的齿舌带每1横列具有2枚侧齿和2枚缘齿,缺乏中央齿,齿式为1.1.0.1.1。齿舌带前端弯曲,齿片排列松散且存在明显的磨损现象;中段齿片排列紧密、整齐;后端齿片无色且宽度有略微的缩小。侧齿呈镰刀型,具1个齿尖,基部呈三角形且具突起,尖齿部分细长;缘齿具3个齿尖,第2尖齿靠近第3尖齿。采用多个比例参数来比较嫁齿舌带及其前、中、后3段上的齿片形态,发现嫁齿舌带前、中、后3段各比例参数的值存在一定的关系,即中段大于前段、中段大于后段。     

山西垣曲先炭兽类一新种

本文主要报道1983年9月,在山西省垣曲县寨里发现的一件较完整的先炭兽类老年个体上颌骨.带有颇为完整的左、右齿列. I~1-P~2 各齿前、后均有较长的齿隙. P~1、P~2、P~3 前的齿隙颌骨上,保留有乳前臼齿的齿槽.这块标本在大小及形态特征上,与目前所知先炭兽属 Anthracokeryx 中任何种都有相当大的差异.它代表了该属中的一个新种.     

A new Late Jurassic species of the rare synechodontiform shark, <Emphasis Type="Italic">Welcommia</Emphasis> (Chondrichthyes,Neoselachii)

A new Jurassic species of the very rare and incompletely known synechodontiform shark, Welcommia, is described. The new species, Welcommia cappettai, is represented only by a single tooth, precluding reconstruction of its dentition in detail. Nevertheless, this specimen provides sufficient information and characteristics to establish its taxonomic status. Welcommia cappettai n. sp. occurs in the middle Oxfordian (Upper Jurassic) of south-western Germany. This is the first unambiguous record and named species of Welcommia from the Late Jurassic, substantially reducing the rather large gap in the fossil record of this synechodontiform taxon. So far, two Welcommia species from the Lower Jurassic of Belgium and the Lower Cretaceous of southern France have been described. An additional, still unnamed species seemingly occurs in the Oxfordian of southern France. The new species has plesiomorphic and apomorphic characteristics and, probably, an intermediate dental pattern that tentatively enables reconstruction of evolutionary trends in the dentition of this shark from small and compact teeth with broad, almost triangular cusps, to mesio-distally lengthened teeth with elongated mesial heels resulting in an extremely extended mesial cutting edge in addition to more delicate cusp and cusplets in advanced forms. These differences might be related to improved feeding mechanisms. It is hypothesized that Welcommia was predominantly a component of the Mediterranean faunal province. The disappearance of Welcommia in the Early Cretaceous remains ambiguous and might be related to competition by other sharks, for example hexanchiforms, or might represent a collecting bias and/or taxonomic misidentification of isolated teeth.     

嫁(虫戚)属2种的齿舌形态差异分析

在光镜和电镜下对嫁(虫戚)(Cellana toreuma)和斗嫁(虫戚)(C.grata)的齿舌形态进行观察比较。2种嫁(虫戚)的齿式都为1.1.0.1.1,即具有1枚侧齿和1枚缘齿,缺乏中央齿。齿舌前端都有1小段弯曲,齿片排列松散且存在明显的磨损现象。嫁(虫戚)和斗嫁(虫戚)的侧齿形状很相似,侧齿呈镰刀型且具1个齿尖,基部近似三角形且具突起,尖齿部分细长。两种嫁(虫戚)的缘齿存在一定的差异,嫁(虫戚)缘齿具3个齿尖,第2尖齿靠近第3尖齿。斗嫁(虫戚)缘齿具2个齿尖且比较细长,第2尖齿靠近缘齿基部。本文用17个参数对这两种嫁(虫戚)的齿舌带及其前中后3段上的齿片进行了测量比较,发现斗嫁(虫戚)齿舌带的长宽比明显大于嫁(虫戚)齿舌带的长宽比,即斗嫁(虫戚)的齿舌带显得更加细长。齿舌带前、中、后3段各比例参数的值存在一定的关系,即中段大于前段、中段大于后段。据此认为用齿舌作为2种嫁(虫戚)的分类依据是可行的。