Cranial osteology of Exostinus serratus (Squamata: Anguimorpha), fossil sister taxon to the enigmatic clade Xenosaurus

Within the squamate clade Anguimorpha, Xenosaurus is an enigmatic taxon combining several apparently primitive features with a highly specialized set of autapomorphies. This combination makes the fossil record along the Xenosaurus stem particularly important for resolving the relationships of Xenosaurus with other anguimorphs, and between species of Xenosaurus.Exostinus serratus Cope, 1873 from the Oligocene of the western United States is currently hypothesized to be the immediate sister taxon to Xenosaurus. The cranial osteology of this pivotal taxon is described here for the first time from all known material, using high‐resolution X‐ray computerized tomography (CT) scanning to visualize individual elements. Exostinus serratus displays a mosaic of ancestral anguimorph features that are transformed in Xenosaurus, as well as unique synapomorphies shared with Xenosaurus. The region of the external nares is less transformed than in Xenosaurus, as are the general proportions of the bones surrounding the cartilaginous nasal capsule. However, the forms of the teeth and of the osteodermal sculpture, as well as several details of maxillary and mandibular morphology, are distinctly Xenosaurus‐like. Several autapomorphies are also present, including an abbreviated tooth row and an unusually wide palatal shelf of the maxilla. An understanding of the ways in which the non‐ossified tissues of the head influenced the development of the bones is crucial to interpreting their morphology. Furthermore, subtle anatomical features often provide important comparative information, and are emphasized herein. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 159 , 921–953.     

Anatomy and phylogenetic value of the mandibular and coronoid canals and their associated foramina in proboscideans (Mammalia)

Characters associated with the mandibular canal are differently distributed amongst proboscidean lineages and provide useful information on the systematics and relationships of proboscideans. The aim of this paper is to describe the pattern of the mandibular canal and its associated foramina in proboscideans in order to fully appreciate the extent of interspecific variation of these structures within the group and to discuss its systematic and phylogenetic value. Outgroup comparison indicates that the condition presented by the basal proboscidean Phosphatherium is morphotypic for proboscideans. Primitive proboscidean characters are: the low position of the mandibular foramen, and its crescent‐shaped outline, the occurrence of a coronoid foramen (canal), the occurrence of two lateral mental foramina, the posterior one at the level of (or slightly behind) the posterior margin of the symphysis, the anterior one in a more distal position, the absence of a medial mental foramen (MMF), the mandibular canal set just below the tooth row. The occurrence of a single lateral mental foramen may represent a shared derived character of Daouitherium, Numidotherium, and Barytherium. A unique derived feature of the Elephantinae mandible is the occurrence of a medial mental foramen on the medial side of the incisive part of the mandible. MMFs have never been observed in other proboscideans excluding elephantines. The very high frequency of MMFs observed in Mammuthus meridionalis–Mammuthus trogontherii–Mammuthus primigenius (>93 per cent of the studied specimens) could be considered a synapomorphy of this group. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161 , 391–413.     

Cranial anatomy of Shunosaurus, a basal sauropod dinosaur from the Middle Jurassic of China

Shunosaurus, from the Middle Jurassic of China, is probably the best‐known basal sauropod and is represented by several complete skeletons. It is unique among sauropods in having a small, bony club at the end of its tail. New skull material provides critical information about its anatomy, brain morphology, tooth replacement pattern, feeding habits and phylogenetic relationships. The skull is akinetic and monimostylic. The brain is relatively small, narrow and primitively designed. The tooth replacement pattern exhibits back to front replacement waves in alternating tooth position. The teeth are spatulate, stout and show well‐developed wear facets indicative of coarser plant food. Upper and lower tooth rows interdigitate and shear past each other. Tooth morphology, skull architecture, and neck posture indicate that Shunosaurus was adapted to ground feeding or low browsing. Shunosaurus exhibits the following cranial autapomorphies: emargination of the ventral margin of the jugal/quadratojugal bar behind the tooth row; postorbital contains a lateral pit; vomers do not participate in the formation of the choanae; pterygoid is extremely slender and small with a dorsal fossa; quadrate ramus of the pterygoid is forked; quadratojugal participates in the jaw articulation; tooth morphology is a combination of cylindrical and spatulate form; basipterygoid process is not wrapped by the caudal process of the pterygoid; trochlear nerve has two exits; occlusal level of the maxillary tooth row is convex downward, whereas that of the dentary is concave upward, acting like a pair of garden shears; dentary tooth count is 25 or more; and the replacing teeth invade the labial side of the functional teeth. Cranial characters among the basal sauropods are reviewed. As Shunosaurus is the earliest sauropod for which cranial remains are known, it occupies an important position phylogenetically, showing the modification of skull morphology from the prosauropod condition. Although the skull synapomorphies of Sauropoda are unknown at present, 27 cranial synapomorphies are known for the clade Eusauropoda. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136 , 145?169.     

The holotypes of the upper Pleistocene Crocuta crocuta spelaea (Goldfuss, 1823: Hyaenidae) and Panthera leo spelaea (Goldfuss, 1810: Felidae) of the Zoolithen Cave hyena den (South Germany) and their palaeo‐ecological interpretation

The rediscovered holotype skulls of Late Pleistocene Panthera leo spelaea ( Goldfuss, 1810 ) (Felidae) and Crocuta crocuta spelaea ( Goldfuss, 1823 ) (Hyaenidae) from the Zoolithen Cave at Burggeilenreuth, southern Germany, are discussed. The cave became famous mainly due to its rich cave bear bone remains from the late Saalian (OIS 6–8) to Eemian/Weichselian (OIS 3–6) including additionally a third holotype of Ursus spelaeus Rosenmüller, 1794 (Ursidae). The ‘Felis spelaea’ holotype represents an adult male with a strong bite mark on the saggital crest, which was in an early stage of healing. Compared with other European Late Pleistocene lion skulls and skeletons, and with modern African lions, it provides evidence of intraspecific conflict between male Ice Age lions. The holotype of ‘Hyaena spelaea’ is one of several hundred hyena remains from a well‐frequented hyena den cave. The cave was used intensively by Late Pleistocene hyena clans, for collecting lion carcasses in addition to their accustomed prey, as happened in many caves throughout Europe. Ice Age spotted hyena clans might have killed Ice Age steppe lions for many reasons, such as fights over prey and territory, and the protection of cubs, but they did not always scavenge on their carcasses. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 822–831.     

The skull of the Upper Cretaceous snake Dinilysia patagonica Smith‐Woodward, 1901, and its phylogenetic position revisited

The cranial anatomy of Dinilysia patagonica, a terrestrial snake from the Upper Cretaceous of Argentina, is redescribed and illustrated, based on high‐resolution X‐ray computed tomography and better preparations made on previously known specimens, including the holotype. Previously unreported characters reinforce the intriguing mosaic nature of the skull of Dinilysia, with a suite of plesiomorphic and apomorphic characters with respect to extant snakes. Newly recognized plesiomorphies are the absence of the medial vertical flange of the nasal, lateral position of the prefrontal, lizard‐like contact between vomer and palatine, floor of the recessus scalae tympani formed by the basioccipital, posterolateral corners of the basisphenoid strongly ventrolaterally projected, and absence of a medial parietal pillar separating the telencephalon and mesencephalon, amongst others. We also reinterpreted the structures forming the otic region of Dinilysia, confirming the presence of a crista circumfenestralis, which represents an important derived ophidian synapomorphy. Both plesiomorphic and apomorphic traits of Dinilysia are treated in detail and illustrated accordingly. Results of a phylogenetic analysis support a basal position of Dinilysia, as the sister‐taxon to all extant snakes. The fossil taxa Yurlunggur, Haasiophis, Eupodophis, Pachyrhachis, and Wonambi appear as derived snakes nested within the extant clade Alethinophidia, as stem‐taxa to the crown‐clade Macrostomata. The hypothesis of a sister‐group relationship between Dinilysia and Najash rionegrina, as suggested by some authors, is rejected by the results of our analysis. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 194–238.     

Brief communication: Identification reassessment of the isolated tooth Krapina D58 through occlusal fingerprint analysis

High variability in the dentition of Homo can create uncertainties in the correct identification of isolated teeth. For instance, standard tooth identification criteria cannot determine with absolute certainty if an isolated tooth is a second or third maxillary molar. In this contribution, using occlusal fingerprint analysis, we reassess the identification of Krapina D58 (Homo neanderthalensis), which is catalogued as a third maxillary molar. We have hypothesized that the presence/absence of the distal occlusal wear facets can be used to differentiate second from third maxillary molars. The results obtained confirm our hypothesis, showing a significant difference between second and third maxillary molars. In particular we note the complete absence of Facets 7 and 10 in all third molars included in this analysis. The presence of these facets in Krapina D58 eliminates the possibility that it is a third maxillary molar. Consequently it should be reclassified as a second molar. Although this method is limited by the degree of dental wear (i.e., unworn teeth cannot be analyzed) and to individual molars in full occlusion, it can be used for tooth identification when other common criteria are not sufficient to discriminate between second and third maxillary molars. Am J Phys Anthropol 143:306–312, 2010. © 2010 Wiley‐Liss, Inc.     

Cone Beam Computed Tomography Assessment of the Maxillary Incisive Canal and Foramen: Considerations of Anatomical Variations When Placing Immediate Implants

IntroductionThe maxillary incisive canal connects the roof of the oral cavity with the floor of nasal cavity and has the incisive and nasal foramina respectively at its two opposite ends. Its close proximity with the anterior incisors affects one’s ability to place immediate implants in ideal position.ObjectiveTo avoid causing complication, variations in their dimensions were studied.ResultsThe mean labiopalatal and mesiodistal measurements of the incisive foramen were 2.80mm and 3.49 mm respectively, while the labiopalatal width of the nasal foramen was 6.06mm. The incisive canal was 16.33mm long and 3.85 mm wide. The anterior maxillary bone has an average thickness of 7.63 mm. The dimensions of the incisive foramen and incisive canal, and anterior maxillary bone thickness demonstrated gender differences with males showing greater values. The anterior maxillary bone thickness was affected by age but this difference was not observed in canal dimensions. The majority of subjects have a funnel shape-like incisive canal with the broader opening located at its superior. They seem to have a longer slanted-curve canal with one channel at its middle portion and a narrower incisive foramen opening than those reported elsewhere.ConclusionsThis study found that gender is an important factor that affected the characteristics of the IC and the amount of bone anterior to it. Male generally had bigger IC and thicker anterior bone. In addition, the anterior maxillary bone thickness was affected by aging, where it becomes thinner with increased age even though the subjects were fully dentate.     

Cranial osteology and phylogenetic position of the theropod dinosaur Proceratosaurus bradleyi (Woodward, 1910) from the Middle Jurassic of England

The cranial osteology of the small theropod dinosaur Proceratosaurus from the Bathonian of Minchinhampton, England, is described in detail, based on new preparation and computed tomography (CT) scan images of the type, and only known, specimen. Proceratosaurus is an unusual theropod with markedly enlarged external nares and a cranial crest starting at the premaxillary–nasal junction. The skull is highly pneumatic, with pneumatized nasals, jugals, and maxillae, as well as a highly pneumatic braincase, featuring basisphenoid, anterior tympanic, basipterygoid, and carotid recesses. The dentition is unusual, with small premaxillary teeth and much larger lateral teeth, with a pronounced size difference of the serrations between the mesial and distal carina. The first dentary tooth is somewhat procumbent and flexed anteriorly. Phylogenetic analysis places Proceratosaurus in the Tyrannosauroidea, in a monophyletic clade Proceratosauridae, together with the Oxfordian Chinese taxon Guanlong. The Bathonian age of Proceratosaurus extends the origin of all clades of basal coelurosaurs back into the Middle Jurassic, and provides evidence for an early, Laurasia‐wide, dispersal of the Tyrannosauroidea during the late Middle to Late Jurassic. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009.     

Ecophenotypic variation and phylogenetic inheritance in first lower molar shape of extant Italian populations of Microtus (Terricola) savii (Rodentia)

Seventeen extant populations of Microtus (Terricola) savii have been investigated for correlations of first lower molar shape to climatic variables by means of geometric morphometrics, and controlling for phylogenetic inheritance. Comparative methods revealed that climatic variables and phylogeography provide a very similar contribution to variation in first lower molars morphology, whereas tooth size does not appear to be affected by climatic conditions. Climate‐related changes have been recognized in the anteroconid portion of the tooth. This indicates that molar tooth variation is strongly influenced by climatic conditions, although in a complex way. Calabrian populations, often ascribed to Microtus (Terricola) brachycercus, form a distinct cluster, in agreement with the most recent genetic analyses. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 632–647.     

Influences of age and maxillary anterior teeth status on patient's satisfaction with dental appearance and tooth colour

doi: 10.1111/j.1741‐2358.2011.00543.x Influences of age and maxillary anterior teeth status on patient’s satisfaction with dental appearance and tooth colour Objectives: To study the impact of age, gender, tooth colour and maxillary anterior teeth status on patient’s satisfaction with their dental appearance. Material and methods: A total of 259 Caucasian subjects participated in the study (119 men, mean age 56 years; 140 women, mean age 61 years) divided into three age groups (young <35 age; middle aged 35–54 age; old ≥55 age). Their maxillary anterior teeth status was classified into three groups: (1) natural teeth (NTG) group; (2) composite filling group (CFG) and (3) porcelain‐fused‐to‐metal fixed prosthodontic restoration group (FPDG). The participants judged appearance and tooth colour using a scale with three categories: completely dissatisfied, moderately dissatisfied and completely satisfied. Results: Almost half of the participants were completely satisfied with their dental appearance and tooth colour. Half of the ‘young’ and ‘middle‐aged’ participants with natural maxillary anterior teeth were completely satisfied and half of the ‘old’ participants were moderately satisfied with their dental appearance and tooth colour. The majority of participants with composite restorations (45–51%) were moderately satisfied with their dental appearance, one‐third of ‘young’ and ‘middle‐aged’ participants were moderately satisfied or dissatisfied with their tooth colour and more than 70% of older participants were dissatisfied with their tooth colour (p > 0.05). Conclusions: Satisfaction with the appearance of the maxillary anterior teeth differed both between individuals of different age and different dental status.     

The morphology and systematics of Mammalodon colliveri (Cetacea: Mysticeti), a toothed mysticete from the Oligocene of Australia

Mammalodon colliveri is an unusual toothed archaic mysticete (Cetacea) from the Upper Oligocene Jan Juc Formation of south‐east Australia. The morphology of the holotype skull and postcrania are described in detail. Superimposed on the generally plesiomorphic archaeocete‐like morphology of Mammalodon are subtle mysticete synapomorphies. Derived features of Mammalodon include a short and bluntly rounded rostrum, reduced premaxillae, and anterodorsally directed orbits. Within Mysticeti, this suite of features is unique. The aberrant rostral morphology of Mammalodon suggests specialization for suction feeding. Janjucetus hunderi is placed in an expanded family Mammalodontidae. Phylogenetic analysis corroborates the monophyly of Basilosauridae, Neoceti, Odontoceti, and Mysticeti, and yields a novel hypothesis of toothed mysticete relationships: a basal clade of undescribed toothed mysticetes from South Carolina, a Llanocetidae + Mammalodontidae clade, and monophyletic Aetiocetidae are posited as successive sister taxa to edentulous baleen whales (Chaeomysticeti). Toothed archaic mysticetes clearly employed diverse prey capture strategies, with exaptations for filter feeding evolving sequentially in stem group Mysticeti. A stratigraphically calibrated phylogeny implies that the initial diversification of Mysticeti occurred during the Late Eocene. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158 , 367–476.     

Performance of shark teeth during puncture and draw: implications for the mechanics of cutting

The performance of an organism's feeding apparatus has obvious implications for its fitness and survival. However, the majority of studies that focus on chondrichthyan feeding have largely ignored the role of teeth. Studying the functional morphology of shark teeth not only elucidates the biological role that teeth play in feeding, but also provides insight specifically into the evolution of shark feeding because teeth are often the only structures available in the fossil record. In the present study, we investigate the puncture and draw performance of three general categories of extant teeth, tearing‐type, cutting‐type, and cutting–clutching type, as well as three fossil morphologies, utilizing a universal testing system. Differences in puncturing performance occurred among different prey items, indicating that not all ‘soft’ prey items are alike. The majority of teeth were able to puncture different prey items, and differences in puncture performance also occurred among tooth types; however, few patterns emerged. In some cases, broader triangular teeth were less effective at puncturing than narrow‐cusped teeth. There were no differences between the maximum draw forces and maximum puncture forces. Many of the shark teeth in the present study were not only able to perform draw and puncture equally well, but also many tooth morphologies were functionally equivalent to each other. The findings obtained in the present study lend little support to the belief that shark tooth morphology is a good predictor of biological role. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 271–286.     

Evolution of the zygomasseteric construction in Rodentia,as revealed by a geometric morphometric analysis of the mandible of Graphiurus (Rodentia,Gliridae)

Graphiurus is a peculiar taxon among the monophyletic Gliridae (order Rodentia) in showing hystricomorphy of the zygomasseteric architecture of the skull [large infraorbital foramen (IOF), and correlative muscular arrangements). We analysed 34 extant genera taken from two groups of sciurognath rodents that share a large IOF (hystricomorph and myomorph) using elliptical Fourier transform in order to appraise whether this feature of cranial morphology was also accompanied by similar changes in mandible shape. The mandible of Graphiurus is distinct from those of all other hystricomorph sciurognath rodents in showing a more elongated coronoid process and a shorter angular process. Thus, two distinct zygomasseteric organizations (i.e. myomorphy and hystricomorphy of graphiurines) are associated with a similar mandible shape characterized by a well‐developed coronoid process. Results show that hystricomorphy of graphiurines was achieved convergently with other hystricomorph rodents. Protrogomorphy is the plesiomorphic condition in Gliridae and hystricomorphy is an autapomorphic feature of Graphiurus. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society, 2008, 154 , 807–821.     

Heterochrony and tooth evolution in hyperodapedontine rhynchosaurs (Reptilia, Diapsida)

The tooth arrangement of hyperodapedontine rhynchosaurs shows clear patterns of morphological derivation, which can be summarized as three main apomorphic trends: the increase in the number of tooth rows lateral to the main maxillary groove, the loss of dental structures (medial groove and lingual teeth) medial to the main maxillary groove, and the loss of dental structures (medial crest and lingual teeth) medial to the main dentary crest. The analysis of these trends from a heterochronic viewpoint reveals that acceleration was the most probable process involved in the increase in number of the lateral maxillary tooth rows, while the loss of the medial structures of the maxilla and dentary seem to be related respectively to neoteny and post-displacement. Both peramorphic and paedomorphic processes are, therefore, thought to have directed the main modifications seen in the tooth arrangement of the hyperodapedontine rhynchosaurs. Heterochrony plays an important role in the evolution of the Late Triassic rhynchosaurs, which are differentiated mainly on the basis of their dental morphology.     

Insertion and withdrawal of extremely elongated genitalia: a simple mechanism with a highly modified morphology in the leaf beetle,Lema coronata

Complicated genital structures are widely known in many animals. It is assumed that an increasing morphological complexity of genital structures would also increase the difficulty of inserting and withdrawing the structures. We examined the insertion and withdrawal mechanisms of extremely elongated genitalia in the Japanese leaf beetle, Lema (Lema) coronata. Insertion and withdrawal processes are completed quickly. Investigation of genital morphology showed that there are no protractor or retractor muscles attached to the elongated part. Instead, the elongated part is tightly enveloped by a membrane. Because of the close fit between the elongated part and its surrounding membrane, eversion of the membrane allows for insertion of the elongated part, and retraction of the membrane induces withdrawal of the elongated part. This surrounding membrane makes it possible to store the median ejaculatory guide (MEG) in a small genital cavity, with the basal portion of the elongated part extending internally against the entrance. This unusual character state is observed only in members of the subgenus Lema, which also have the elongated part. This condition can be considered to be a preadaptation for extreme elongation of genitalia. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 512–520.     

A new genus and species of fossil myliobatoid ray from the Fishburne Formation (lower Eocene/Ypresian) of Berkeley County,South Carolina,USA

Elasmobranch fossils recovered from the Fishburne Formation (lower Eocene/Ypresian) of Berkeley County, South Carolina, USA, include species from four genera of sharks and six genera of rays. Of particular interest was the recovery of multiple isolated teeth from a new genus and species of the cownosed ray family Rhinopteridae, which is the focus of this study. The unique crown morphology separates this genus and species from Rhinoptera. Eorhinoptera grabdai, gen. et sp. nov., is represented by small, bar-shaped teeth in the shape of greatly elongated hexagons. These teeth are the isolated elements of a dental plate. The holotype, with 12 wide root lobes, is the most elongated in the sample being 1 cm long and 1.5 mm wide, indicating an origin in the central region of the plate. Paratypes are less elongated, have 4–8 root lobes and are from more lateral rows. The crown is smooth and has a distinctly convex occlusal surface. Eorhinoptera is only the second genus of cow-nosed ray. Its distinctive crown morphology may have allowed it to exploit different kinds of prey than those favoured by rays that lacked convex tooth crowns.     

Contribution to the taxonomic status of the Chinese rats Niviventer confucianus and N. fulvescens

The status of Niviventer confucianus and N. fulvescens as separate species or color variants of the same species has been debated for a long time. A detailed study of 157 specimens (119 N. confucianus and 34 N. fulvescens) collected 1937/1938 in Fukien, South East China, was conducted in order to shed more light on the taxonomic status of the two taxa. Because all measured skull parameters strongly correlate with age, age classes were formed on the basis of tooth wear. Student's t-tests for differences between N. confucianus and N. fulvescens were performed using age-independent unstandardized residuals. These were derived from linear regressions of each measured parameter against age class. Statistical significant differences between the taxa were revealed in residuals based on interorbital constriction, length and width of incisive foramen, length of bulla, diastema, width of rostrum and width of nasal. Discriminant analysis using the unstandardized residuals shows a clear separation between N. confucianus and N. fulvescens on the basis of the first discriminant function mainly influenced by interorbital width and length of incisive foramen. Additionally, qualitative morphological differences in the skulls are described, concerning the anterior rim of the zygomatic plate, the mandible and the maxillary teeth. The differences in outer morphology including the brighter, more reddish and more shiny pelage of N. fulvescens, white tail tip occurring in N. confucianus only, the relatively longer tail in N. confucianus, and the higher frequency of a fulvous marking on the chest in N. confucianus are supported.     

A new stereospondyl from the German Middle Triassic, and the origin of the Metoposauridae

Recent finds of well-preserved temnospondyl skeletons from the Lower Keuper (Ladinian, Middle Triassic) in southern Germany are assigned to a new genus and species, Callistomordax kugleri . This taxon is characterized by the following autapomorphies: (1) wide unpaired frontal; (2) vomerine fangs greatly enlarged to occupy entire width of element; (3) intercentra elongated and massive, anterior face being convex; (4) humerus semilunar with enlarged deltopectoral crest; (5) cleithrum strongly curved and bow-shaped; (6) trunk extremely elongated to reach three times the length of the skull. Callistomordax shares with the Metoposauridae the pattern of dermal ornamentation, the proportion of both posterior skull table and snout, the position of the lacrimal, the morphology of the basicranial region, and the structure of the clavicle and interclavicle. Phylogenetic analysis suggests Callistomordax to be the sister taxon of the Metoposauridae, nested within a grade formed by various trematosaurian taxa. In this assemblage, Lyrocephaliscus and a clade formed by Almasaurus , Rileymillerus , Callistomordax , and the Metoposauridae are sister taxa. In all variants of the cladistic analysis, Callistomordax and the Metoposauridae form immediate sister groups. According to the present findings, neither plagiosaurids nor brachyopoids and rhytidosteids are closely related to this 'trematosaurian' monophylum, although these taxa share a range of homoplasies.  © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 79–113.