Late Jurassic Mammals from Tendaguru, Tanzania, East Africa

Records of Mesozoic mammals are extremely rare in Africa. The only previous record from the Upper Jurassic of Africa is a fragmentary mandible without teeth of Brancatherulum tendagurense. Here I report the discovery of two new mammals from the Upper Jurassic of Tendaguru, Tanzania. The fossils were recovered from the Middle Saurian Bed of the Tendaguru Series. A lower molar of a triconodontid mammal is described as Tendagurodon janenschi gen. et sp. nov., and a fragmentary dentary of a eupantothere as Tendagurutherium dietrichi gen. et sp. nov. The eupantothere in particular contributes to documenting the evolution of mammals during the Mesozoic. The posterior portion of the mandible of Tendagurutherium dietrichi gen. et sp. nov. shows that the angular (tympanic) bone was not yet completely separated from the dentary, a previously undocumented stage of eupantotherian middle ear evolution.     

Tooth replacement pattern of Coloborhynchus robustus (Pterosauria) from the Lower Cretaceous of Brazil

The well preserved anterior upper and lower jaw fragment of an adult specimen of Coloborhynchus robustus (Pterosauria: Ornithocheiridae), SMNK 2302 PAL, allowed investigations of the replacement pattern of the dentition macroscopically and by using CT scans. The quantification of the dentition by Zahnreihen, Z-Spacing, and replacement waves indicates a complex pattern of different replacement stages in which large gaps within the dentition were avoided. The specialized prey-catching apparatus of Coloborhynchus thus could retain its function even following tooth replacement. The replacement process in the specimen took about 2/3 of the total life-time of a tooth, and damaged teeth in the anterior jaw region may have been replaced more rapidly than posterior teeth. The distolingual replacement of the functional teeth delayed the time of their shedding in comparison with the circular resorption present in crocodiles. In contrast to these, the distolingual position of the replacement tooth did not decrease the biomechanical stability of the functional tooth, which can also be observed as a convergence in other thecodont dentitions, e.g., recent carnivore mammals. Teeth were shed when their replacement had reached about 60% of the full-grown height. A comparison of the observed pattern is constricted by the preservation and preparation of other specimens. Unfortunately, no known specimen in public collections reaches the quality of Coloborhynchus robustus, SMNK 2302 PAL, so that comparable patterns in other specimens are not likely to be detected.     

Late Jurassic cockroaches (Insecta,Blattaria) from the Houtiyn-Hotgor locality in Mongolia

A low-diversity cockroach assemblage from the Upper Jurassic of the Houtiyn-Hotgor locality in Mongolia is described, comprising Solemnia alexandri gen. et sp. nov. (Caloblattinidae), Blattula choutinensis sp. nov. (Blattulidae) and a presumed Triassic relict Irreblatta relicta gen. et sp. nov. (incertae familiae). The carnivorous Raphidiomimidae supposedly originated directly from the Caloblattinidae.     

Neoselachian sharks from the Callovian–Oxfordian (Jurassic) of Ogrodzieniec,Zawiercie Region,southern Poland

Abstract: Callovian and Oxfordian strata in Ogrodzieniec near Zawiercie, southern Poland, have yielded two shark tooth assemblages that collectively include 14 neoselachian taxa. A previously unrecognised member of the Orectolobiformes, Akaimia altucuspis gen. et sp. nov., is described and characterised by a dentition remarkably similar to modern wobbegong sharks (Orectolobidae) by convergence. The assemblages also include the first anterior teeth ever found of the palaeospinacid ‘Synechodus’prorogatus Kriwet, in addition to teeth from two other palaeospinacids, Sphenodus spp., four different orectolobiforms, two hexanchids and Protospinax spp. These shark tooth assemblages contribute to the poorly known Callovian and Oxfordian neoselachian faunas and indicate that the diversity was higher than previously appreciated, particularly within the Orectolobiformes.     

Tooth development and replacement in the Atlantic Cutlassfish,Trichiurus lepturus,with comparisons to other Scombroidei

Atlantic Cutlassfish, Trichiurus lepturus, have large, barbed, premaxillary and dentary fangs, and sharp dagger-shaped teeth in their oral jaws. Functional teeth firmly ankylose to the dentigerous bones. We used dry skeletons, histology, SEM, and micro-CT scanning to study 92 specimens of T. lepturus from the western North Atlantic to describe its dentition and tooth replacement. We identified three modes of intraosseous tooth replacement in T. lepturus depending on the location of the tooth in the jaw. Mode 1 relates to replacement of premaxillary fangs, in which new tooth germs enter the lingual surface of the premaxilla, develop horizontally, and rotate into position. We suggest that growth of large fangs in the premaxilla is accommodated by this horizontal development. Mode 2 occurs for dentary fangs: new tooth germs enter the labial surface of the dentary, develop vertically, and erupt into position. Mode 3 describes replacement of lateral teeth, in which new tooth germs enter a trench along the crest of the dentigerous bone, develop vertically, and erupt into position. Such distinct modes of tooth replacement in a teleostean species are unknown. We compared modes of replacement in T. lepturus to 20 species of scombroids to explore the phylogenetic distribution of these three replacement modes. Alternate tooth replacement (in which new teeth erupt between two functional teeth), ankylosis, and intraosseous tooth development are plesiomorphic to Bluefish + other Scombroidei. Our study highlights the complexity and variability of intraosseous tooth replacement. Within tooth replacement systems, key variables include sites of formation of tooth germs, points of entry of tooth germs into dentigerous bones, coupling of tooth germ migration and bone erosion, whether teeth develop horizontally or immediately beneath the tooth to be replaced, and how tooth eruption and ankylosis occur. Developmentally different tooth replacement processes can yield remarkably similar dentitions.     

Sharks, Rays and A Chimaeroid from the Kimmeridgian (Late Jurassic) of Ringstead, Southern England

Sampling of a lenticular concentration of vertebrate debris and associated sediments from the lower Kimmeridgian of southern England has allowed the study of a diverse and abundant assemblage of chondrichthyan remains. A number of previously undescribed species are recorded, of which three new species are named; Squatina? frequens, Synechodus plicatus and Protospinax planus. Additional diagnosis of the genus Paracestracion Koken is given to allow its identification from dental remains. Several nominal batoid species are synonymised with Spathobatis bugesiacus Thiolliere. This assemblage is considered to be typical of Middle–Late Jurassic neritic environments, and is compared to other contemporaneous selachian faunas.     

中华山蝠牙齿的脱换模式

笔者于1997年对中华山蝠(Nyctalus velutinus)牙齿的脱换模式进行了研究。共观察幼蝠200只次。中华山蝠初生仔共有22枚乳齿,齿式为2.1.2.0/3.1.2.0,各乳齿略向舌侧倾斜,除乳前臼齿齿冠不分叉外,其余乳齿齿冠均分为三叶。4d龄开始换齿,31d龄左右脱换完毕。乳齿的脱落顺序是:上颌,PM2→PM1→C1→I1→I2;下颌,I1→PM2.I2→I3→PM1→C1;恒齿萌生的顺序为:上颌,M1→PM2.C1→M2→PM1.M3→I1→I2,下颌,M1→I1.PM2→I2.M2→I3.PM1→C1→M3。     

Tooth implantation and replacement in Sauropterygia

Tooth replacement and implantation of Sauropterygia is described with special reference to the generaPlacodus andNothosaurus. Tooth replacement is horizontal, with the exception of the enlarged crushing tooth plates on the maxilla, palatine, and dentary ofPlacodus (placodonts), which are replaced vertically. Tooth implantation is thecodont, with variable ankylosis of the base of the root. Sauropterygia is unique compared to other reptiles in that replacement teeth are “alveolarized.” The alveolarization of replacement teeth adds to the evidence supporting of a monophyletic Sauropterygia (Placodontia plus Eosauropterygia).      

New ommatids from the Late Jurassic of western Liaoning, China （Coleoptera： Archostemata）

A new genus Amblomma gen. nov. of fossil beetles is erected and can be assignedto the family Ommatidae because its two procoxal cavities are contiguous and the articulations of the abdominal ventrites are abutting. The new genus is similar to Zygadenia Handlirsch, 1906 (=Notocupes Ponomarenko, 1964), Tetraphalerus Waterhouse, 1901,Rhobdocupes Ponomarenko, 1966 and Sinocupes Lin, 1976, but can be distinguished from other genera according to the following characters: the second segment of antennae is shorterthan the third one in length; the posterior tarsi with the basal segment is obviously shorter than the three following taken together in length; the antennae reach the posterior ridge of prothroax in length, and the sides of the prothroax with serrulate margin. Four new species of the new genus are described and figured: Amblomma psilata gen. et sp. nov., Amblomma rudis gen. et sp. nov., Amblomma epicharis gen. et sp. nov., and Amblomma stabilis gen. etsp. nov. A key to species within this new genus is provided. All the specimens are collected from the Late Jurassic Yixian Formation of western Liaoning and are now housed in the College of Life Science, Capital Normal University, Beijing, China.     

New evidence of Ceratosaurus (Dinosauria: Theropoda) from the Late Jurassic of the Lusitanian Basin,Portugal

A theropod assigned to Ceratosaurus was previously reported from the Portuguese Lusitanian Basin based on a limited number of elements of a single individual. Here, we describe newly discovered elements that likely pertain to same, earlier described, specimen. The new elements provide additional evidence that the range of Ceratosaurus spanned from what is now North America into Europe. Previously, some differences were noted between the Portuguese specimens and the North American Ceratosaurus. We consider these differences to be trivial and attribute them to individual variation and/or ontogeny. The following set of features (lesser trochanter positioned low on the femur; crista tibiofibularis obliquely oriented with respect to the axis of the femoral shaft; infrapopliteal ridge present posteriorly on the femur; large cnemial crest; and medial condyle of the tibia continuous with proximal end) indicate that the Portuguese specimen is assignable to Ceratosaurus. This record constitutes one of the scarce evidence of basal ceratosaurian theropods in the Late Jurassic of Europe. Despite the abundance, diversity and wide geographical distribution of ceratosaurs during the Late Cretaceous, its early evolutionary history remains poorly understood. The Portuguese specimens constitute an important evidence for the knowledge of the paleobiogeographic evolution of the clade during the Late Jurassic.     

Ontogenetic transition from unicuspid to multicuspid oral dentition in a teleost fish: Astyanax mexicanus, the Mexican tetra (Ostariophysi: Characidae)

Teleost fishes display a remarkable diversity of adult dentitions; this diversity is all the more remarkable in light of the uniformity of first-generation dentitions. Few studies have quantitatively documented the transition between generalized first-generation dentitions and specialized adult dentitions in teleosts. We investigated this transition in the Mexican tetra, Astyanax mexicanus (Characidae), by measuring aspects of the dentition in an ontogenetic series of individuals from embryos to 160 days old, in addition to adults of unknown age. The first-generation dentition and its immediate successors consist of small, unicuspid teeth that develop extraosseously. Multicuspid teeth first appear during the second tooth replacement event, and are derived from single tooth germs, rather than from the fusion of multiple conical tooth germs. We document that the transition from unicuspid to multicuspid teeth corresponds to a change in the location of developing tooth germs (from extraosseous to intraosseous) and in patterns of tooth replacement (from haphazard to simultaneous within a jaw quadrant). In addition, while the size of the largest teeth scales with positive allometry to fish size, the transition to multicuspid teeth is accompanied by an exceptionally large increase in tooth size.  © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society , 2005, 145 , 523–538.     

Spatial distribution of Late Pliensbachian (Early Jurassic) calcareous nannofossils within the Lusitanian basin (Portugal)

Quantitative analyses of Pliensbachian calcareous nannofossils have been carried out on a proximal-distal transect in the Lusitanian Basin (Portugal). The studied sections Vale Venteiro near Tomar and Peniche represent proximal and distal environments with respect to the emerged land of the Iberian Meseta (to the East). The upper portion of the Vale das Fontes Fm (Davoei and Margaritatus ammonite Zones) is studied in both sections and correlated by means of ammonite and nannofossil integrated biostratigraphy. A careful analysis of the preservation state of nannofossils is performed. Preservation state is moderate to good in the two settings; changes in nannofossil assemblages are therefore considered as primary. Samples were analysed for nannofossil absolute and relative abundances, species diversity and wt%CaCO₃. The analysis of calcareous nannofossils (absolute abundance, percentage, average abundance) shows changes in the community structure in space (i.e., from proximal to distal), and vertically within the water column. This pattern suggests a partitioning of habitats within the photic zone, and with respect to emerged lands. Proximal environments within the Lusitanian Basin were probably more eutrophic, because of the proximity of emerged lands to the East (Iberian Meseta). This was the source area for nutrients delivered into the basin by river transport. Distal environments were likely characterized by a greater water depth and by a deeper light penetration leading to a relatively more expanded photic zone. The assemblages recorded in the proximal setting exhibit high mean relative abundance of placolith-bearing coccolithophorids (Lotharingius spp., Biscutum spp. and Similiscutum spp.) and of Schizosphaerella spp., while distal assemblages are dominated by Crepidolithus crassus and Schizospharella spp. Crepidolithus crassus is interpreted as a deep-dweller coccolithophorid, inhabiting preferentially distal and deeper settings in the Lusitanian Basin. Placolith-bearing coccolithophorids were more abundant in proximal settings with respect to emerged lands, under relatively elevated trophic conditions. The probable calcareous dinocyst Schizospharella spp. proliferated in surface waters of both proximal and distal environments.     

A new cryptoclidid Plesiosaur from the Oxfordian (Late Jurassic) of Cuba

Cryptocleidus ? cuervoi caroliDE LA TORRE & ROJAS, 1949, a partial skull with associated mandible and atlas-axis from the Oxfordian of Cuba, has been completely prepared for the first time. It is here redescribed and assigned to a new cryptoclidid genus, Vinialesaurus, for which the species caroli is retained. Vinialesaurus is mainly diagnosed by palatal characters such as double internal nares, an anteriorly rounded vomer and a lack of anterior interpterygoid vacuities. It shares with other cryptoclidids large orbits and external nares, a small vertical jugal and a reduced tooth ornamentation. The occurrence of Vinialesaurus caroli in association with pliosauroids, ophthalmosaurian ichthyosaurs, metriorhynchid crocodilians and pleurodiran marine turtles, strongly suggests that a marine seaway was present in the Caribbean during the Oxfordian, connecting the western Tethys with the Oriental Pacific.     

Itatodon tatarinovi (Tegotheriidae, Mammalia), a docodont from the Middle Jurassic of Western Siberia and phylogenetic analysis of Docodonta

Itatodon tatarinovi Lopatin et Averianov, 2005 is represented by two lower molars and a lower molar fragment from the upper part of the Itat Formation (Bathonian Stage) of the Berezovskii quarry (southern Krasnoyarsk Region). Based on the presence of a pseudotalonid, bordered by the crests a-b, b-e, e-g, and a-g, Itatodon is assigned to the endemic Asian family Tegotheriidae. In this genus, the crest a-b is reduced and the thick lingual cingulid is better developed than that of other docodonts. Phylogenetic analysis of Docodonta shows paraphyly of Morganucodonta relative to docodonts and independent development of the pseudotalonid in the Tegotheriidae and the clade comprising Krusatodon, Castorocauda, Cyrtlatherium, and Dsungarodon.     

New Chironomidae (Diptera) with elongate proboscises from the Late Jurassic of Mongolia

Four new species of Chironomidae with well-developed elongate proboscises are described from a Late Jurassic site Shar Teg in SW Mongolia. These are named Cretaenne rasnicyni sp. n., Podonomius blepharis sp. n., Podonomius macromastix sp. n., ?Podonomius robustus sp. n.     

A new species of Theriosuchus (Atoposauridae, Crocodylomorpha) from the Late Jurassic (Kimmeridgian) of Guimarota, Portugal

A new species of an atoposaurid crocodilian, Theriosuchus guimarotae, is described from the Late Jurassic (Kimmeridgian) of Portugal. Theriosuchus guimarotae can be distinguished from other species of Theriosuchus by a lateral surface of squamosal bevelled ventrally; a rounded, caudally projecting and dorsally sculptured caudolateral corner of the squamosal; a premaxillomaxillary suture aligned caudomedially in dorsal aspect; a minimum space between the supratemporal foramina that comprises one third of the total width of the cranial table; a minimum width of the frontal between the orbits that comprises one third of the maximum width of the skull at the orbits; a dentition that comprises only pseudocaniniform and lanceolate-shaped teeth; the presence of an external mandibular fenestra and all vertebral bodies amphicoelous. Its osteology also sheds light on the diagnosis of Theriosuchus within Atoposauridae. The material additionally includes specimens representative of several ontogenetic stages, each of which is discussed here. With its Late Jurassic age, T. guimarotae represents the oldest well-preserved material of Theriosuchus and reveals further knowledge about the palaeobiogeography of the genus in western Europe.     

New evidence concerning relationships within Artiodactyla,Mammalia: radicular morphology of the dp/4

Abstract

A synapomorphy of Artiodactyla is the three-lophed lower fourth deciduous molar (dp/4). Only a few non-artiodactyl mammals possess three lobes in the dp/4, among which are Macroscelididae and Deinotheriidae (both Afrotheria). Despite the general acceptance of this character for diagnosing the order Artiodactyla, there has been a curious lack of discussion about variability in root morphology of the tooth. This paper establishes the presence of three subgroups of Artiodactyla on the basis of root morphology of the dp/4. The first has a root under the protoconid (buccal side of the middle lophid) coalescent with the one under the paraconid (Cebochoeridae and some Choeropotamidae), the second group has a buccal root beneath the protoconid, well separated from the paraconid root (selenodont artiodactyls (ruminants and anthracotheres) and some Suiformes (suids, schizoporcids, sanitheres)), and the third group has no root associated with the protoconid (other Suiformes : Hippopotamidae, Doliochoeridae and Siderochoeridae, and non-suiform Camelidae and Diacodexidae (Diacodexis)). Further research is needed on the families Choeropotamidae and Anthracotheriidae, both of which appear to contain taxa with two kinds of root systems in the dp/4. The evidence of the radicular system of the dp/4 weakens the hypothesis that Anthracotheriidae represent the sister taxon of Hippopotamidae.     

Late Jurassic sea-level fluctuations in NW Switzerland (Late Oxfordian to Late Kimmeridgian): closing the gap between the Boreal and Tethyan realm in Western Europe

In Late Jurassic times, the Swiss Jura carbonate platform occupied the transition between the Paris Basin and the Tethys and thus connects the Boreal and Tethyan realm. Up to now, the lack of index fossils in the Reuchenette Formation prevented a reliable correlation between both areas (its sediments are characterised by a prominent sparseness of index fossils). Now, seven recently in situ collected species of ammonites helped to establish a new sequence-stratigraphical frame for the platform sediments of the Reuchenette Formation in NW Switzerland. Based on biostratigraphical data, five third-order sedimentary sequences were assigned to the Late Oxfordian to Late Kimmeridgian. The upper three third-order sequences correspond to the Boreal sequences Kim3–5 of Hardenbol et al. (1998). The deduced large-scale sea-level fluctuations match those from other European regions (Spain, Russia). This biostratigraphically based sequence-stratigraphical frame is a prerequisite to refine correlations within a wider area covering the Swiss Jura and parts of adjacent France and Germany. Electronic Supplementary Material Supplementary material is available for this article at