The Jurassic ammonite Coelocerus: an atypical example of dimorphic progenesis elucidated by cladistics

Instances of convergence or parallelism among unrelated Lower Carixian ammonites are not uncommon. The case of polymorphitid-like ammonites is considered here, and the example of Coeloceras is investigated in detail. The small sexual dimorph (microconch) of Coeloceras pettos (Quensitedt) (Coeloceratidae), a progenetic species, provides a remarkable example of complex convergence with the microconch of Uptonia (Polymorphitidae). Homeomorphic morphology is here an amalgam of juvenile traits, of maturation-related transformations, and of completely new features bearing no obvious relation with either progenesis or maturation. A stratophenetic approach is hardly adequate for unravelling such an involved pattern of convergence. However, a cladistic analysis of ammonoid morphology suggests that Coeloceras was derived from the Tethyan Miltoceras. Indeed, greater biostratigraphic knowledge and the independent use of comparative shell morphology are both needed to improve ammonite phylogeny. □ Convergence, parallelism, progenesis, dimorphism, ammonites, Jurassic.     

Le jurassique supérieur et le Crétacé inférieurd'Ankilizato (bassin de Morandava,Madagascar)

Upper Jurassic and Lower Cretaceous from Beritsa, near Ankilizato, are an important landmark between well known cross sections of Northern (Antsalova) and Southern (Sikily) parts of the Morondava Basin. New ammonites and belemnites fauna point out an Upper Jurassic to Upper Valanginian age for this section. A paleogeographical scheme shows the dynamical structure of «Ankilizato gulf at that time.     

A juvenile eurysternid turtle (Testudines: Eurysternidae) from the upper Kimmeridgian (Upper Jurassic) of Nusplingen (SW Germany)

A juvenile turtle from the upper Kimmeridgian (Upper Jurassic) of Nusplingen is identified as an eurysternid turtle. It differs in plastral morphology from a juvenile eurysternid turtle from the latest Kimmerdigian of Kelheim described in the 19th century, which represents a comparably early developmental stage. Both juveniles have primordial ribs not yet transformed into costals and lack all other carapacial elements whereas the plastral elements are well developed. The new specimen from Nusplingen has a more robust plastron type when compared to the very gracile, bow- or arc-shaped plastron type of the formerly described juvenile. Both plastron types are also represented by yet undescribed additional juvenile, medium-sized and/or larger eurysternid specimens. The juvenile specimens thus likely document the presence of two morphologically very similar eurysternid taxa in the Upper Jurassic of southern Germany. Both plastron types are different from those described for Idiochelys and Solnhofia but may resemble plastron morphology of Eurysternum, which is, however, only incompletely known.     

Nubidites omarai n. g. n. sp., ein neuer ammonit aus dem nubischen sandstein Ägyptens

A loose ammonite from the Nubian Sandstone near Abu Darag, Eastern Desert, Egypt, is described asNubidites omarai n. g. n. sp. Since ammonites from the Nubian Sandstone (Carboniferous to Cretaceous) are extremely rare, the new form is of great importance. The specimen has been found in a Carboniferous section of the Sandstone, but since Jurassic and Cretaceous outcrops occur in the neighbourhood, also these ages have to be considered. An Upper Cretaceous age of the new genus, however, is suggested.     

The dispersal and colonisation behaviour of the marine polychaete <Emphasis Type="Italic">Nereis diversicolor</Emphasis> (O. F. Müller) in south-east England

Recent submarine caves are inhabited by endemic faunas adapted to oligotrophism, darkness and a tranquil environment. Many of their representatives are archaic types of animals resembling fossils from very early times in evolution. This article compares fossil fauna from Jurassic neptunian dykes (originally sea bed clefts) from the Western Carpathians with the Recent cave-dwelling fauna. The ostracods Pokornyopsis feifeli are particularly important. In the Western Carpathians, these were exclusively found in the Middle/Late Jurassic fissure fillings, but in the non-Tethyan Germanic Jurassic this species was found in deep-marine claystones. They are phylogenetic forerunners of the recent genus Danielopolina inhabiting both anchialine caves and deep seas. This indicates a Jurassic migration of deep-marine fauna to cryptic habitats. Other examples of cryptic communities include the Upper Jurassic cavity-dwelling fauna dominated by serpulids and scleractinian corals. Associated suspension feeders include thecideidine brachiopods, oysters, bryozoans, sponges, crinoids and sessile foraminifers. Serpulid-dominated bioconstructions have recent analogies in the Mediterranean and Carribean seas. Different type of dyke communities represent the Late Jurassic fauna of small sized ammonites which originated from both Tethyan and Boreal paleobioprovinces. It has not been established whether these amonites were juvenile, dwarfed specimens adapted to limited cave space or size-sorted adult specimens.     

Progenetic species in polychaetes (Annelida) and problems assessing their phylogenetic affiliation

Progenesis is defined as the retention of ancestral juvenilecharacters by adult stages of descendants due to an accelerationof the sexual maturation and thus is often regarded as a fastevolutionary process. Several small, meiofaunal polychaetes,such as Dinophilidae, some "Dorvilleidae" (for example, Parapodrilus),and Protodrilida, exhibit morphological simplicity in that theylack features typical of larger polychaetes, for example, parapodiaand/or head appendages. Due to the general resemblance of adultmeiofaunal polychaetes to juveniles of larger forms, progenesishas been invoked to explain evolutionary origins of many smallertaxa with increasing frequency over the past 4 decades. In thisreview, I summarize the interstitial species of polychaetesfor which progenetic origin has been suggested on the basisof morphology. However, critical examination of morphologicaldata that includes larval features reveals that autapomorphiccharacters uniting supposed progenetic taxa to specific annelidlineages are often missing. Typically larval and juvenile characters,which are argued to support hypotheses of progenetic origin,are often widely dispersed, homoplastic features. Because ofthis situation, molecular data seem to be the most reliablesource for phylogenetic inference. However, other biologicaldata, for example, from life history and morphology, are necessitiesto substantiate the progenetic evolution of these species.     

The earliest known Salamanders (Amphibia,Caudata):A record from the Middle Jurassic of England

Marmorerpeton gen. nov. represented by M. kermackisp. nov. and M. freemani sp. nov., is the earliest known genus of fossil salamander from the Upper Bathonian, Middle Jurassic of Kirtlington, Oxfordshire, England. Marmorerpeton is more primitive than any other known salamander in the absence of intravertebral spinal nerve foramina in the atlantal centrum, but in other features it resembles members of the family Scapherpetontidae, neotenous salamanders otherwise known from the Upper Cretaceous and Palaeocene. The Kirtlington herpetofauna is a unique freshwater assemblage of Middle Jurassic small amphibians and reptiles, several of which represent the earliest known occurrences of their respective groups.     

Ammonite eggs and ammonitellae from the Kimmeridge Clay Formation (Upper Jurassic) of Dorset, England

Eight clusters of small spherical and subspherical objects, some isolated and some associated with shells of perisphinctid ammonites, have been recovered from the Lower and Upper Kimmeridge Clay (Upper Jurassic) of the Dorset coast, England. They have been interpreted as ammonite egg sacs and represent the freshest and best-preserved examples known so far. Their structures and the ecological framework in which they occur are discussed. The parents are thought to be members of the two eudemic genera Aulacostephanus and Pectinatites that dominate the biostratigraphy of the ammonites in the range of the Kimmeridge Clay in which they occur. Isolated nuclei of ammonitellae have also been recovered.     

New choristoderes (Reptilia: Diapsida) from the Upper Cretaceous and Palaeocene, Alberta and Saskatchewan, Canada, and phylogenetic relationships of Choristodera

New choristoderan fossils from the Late Cretaceous and Palaeocene of Alberta and Saskatchewan, Canada, are described: incomplete maxillae and dentaries from the Upper Cretaceous Oldman Formation, Alberta, extend the range of the primitive Cteniogenys from the Jurassic in the North American Western Interior; an incomplete dentary from the Palaeocene Ravenscrag Formation, Saskatchewan, comprises the first occurrence of the crocodile-like Simoedosaurus in Canada and the earliest record of the genus; well-preserved skulls and mandibles from the Oldman and Horseshoe Canyon formations, Alberta, document a new species of Champsosaurus and clarify the status of previously known species of the genus. New information about Asian choristoderes supports a Tchoiria- ( Ikechosaurus + Simoedosaurus ) relationship, contrary to previous work. Choristoderes share no convincing synapomorphies with either Lepidosauromorpha or Archosauromorpha, but occupy a more basal position within Diapsida, possibly as a sister-taxon with Neodiapsida (Younginiformes + Sauria).     

Progenesis in dicyemids

Dicyemids (Phylum Dicyemida) are the most common and characteristic endosymbiont living in the renal sac of benthic cephalopod molluscs. Precocious development of a hermaphroditic gonad occurs in the larvae and smaller juveniles of 40 dicyemid species from 17 cephalopod species so far and is the usual phenomenon in dicyemids. Based on the developmental and morphological features of precocious individuals, progenesis (a form of heterochrony) is the appropriate term for such precocious development. In general, progenetic individuals have much lower fecundity than normal ones because of their smaller body size, and therefore, it appears to be a disadvantageous reproductive trait. Nonetheless, the number of progenetic individuals consists of 30%–50% of the population, a relatively large proportion suggesting that the presence of progenetic individuals probably plays an important role in life history strategy. Precocious development significantly reduces growth time and enables early maturation. Progenetic individuals are common in short-living cephalopod species, in which precocious development seems appropriate for dicyemids, enabling fast larval release before the end of the host's life span.     

Twopictonia (perisphinctidae) from the subbetic upper jurassic of spain

Two ammonites belonging to the genusPictonia Bayle, 1878 (subgenusPachypictonia Schneid, 1940) are described from the Lower Kimmeridgian of the Subbetic of Western Andalusia, this being the first evidence of the presence of this genus in the Mediterranean (Tethydian) Upper Jurassic.     

FIRST FOSSIL EVIDENCE FOR THE PRIMITIVE ANGIOSPERM FAMILY LACTORIDACEAE

Pollen of the primitive angiosperm family Lactoridaceae has been recovered from Turonian-Campanian (Upper Cretaceous) sediments from eleven boreholes off the southwest coast of southern Africa. This is the first report of the Lactoridaceae in the fossil record. The one extant species of the Lactoridaceae is confined to the Juan Fernandez Islands located off the coast of Chile. The occurrence of lactoridaceous pollen in Cretaceous deposits of southern Africa suggest that this primitive angiosperm family may have been more widespread in the Southern hemisphere during the Cretaceous.     

Heterochronic differentiation of sexual dimorphs among Jurassic ammonite species

Ontogenetic and then heterochronic approaches are used here to analyze sexual differentiation within two well-known Jurassic dimorphic species. This analysis compares two ways of determining the relative biological age of ammonites, one using size (diameter) and the other the number of septa as a proxy of age. The shape standard is established from factor analysis of morphological and growth parameters. Size-age-shape relationships are analyzed on the basis of a new heterochronic representation. When diameter is used as a proxy of age, microconch morphs are globally considered to be progenetic compared with macroconch morphs. When size and age are determined separately and shape is included, (1) Ebrayiceras jactatum (microconch morph) has a shorter period of growth (progenesis) with acceleration of shape compared with its macroconch morph ( Morphoceras macrescens ), (2)( Cardioceras cordatum (microconch morph) has a shorter period of growth (progenesis) coupled with a slower rhythm of growth (dwarfism) compared with its macroconch morph. These findings emphasize the complex relationship between supposed sexual dimorphs in ammonites when size and age standards can be separated, as well as the need for an ontogenetic approach.     

Upper jurassic to lower cretaceous carbonate facies of african affinities in a Peri-European area: Chalkidiki Peninsula, Greece

Summary The Epanomi-New Iraklia area (West coast of the Chalkidiki peninsula) is considered to belong to the Prepeonias subzone (or Gevgeli unit), with a palaeogeographic position near the European margin, represented by the Serbo-Macedonian massif, and at a considerable distance from the fragmented African plate, the marginal block of which is here the Pelagonian Domain. In some boreholes in the area an Upper Jurassic to Lowei Cretaceous limestone sequence has been observed, ending with an unconformity and followed by an Upper Middle-Lower Upper Eocene transgressive bioclastic limestone, an Upper Eocene to Lower Oligocene clastic series and Neogene deposits. This Upper Jurassic to Lower Cretaceous carbonate platform sequence and probably the Upper Jurassic limestones with bauxites of the nearby Mt. Katsika, show African affinities, viz: the presence of the essentially Aptian algal speciesSalpingoporella dinarica, an African plate marker; the chlorozoan type association and the bauxite formation during the Late Jurassic indicating tropical conditions; finally, the chloralgal type association and the sporadic presence of radial-fibrous ooids during the Early Cretaceous indicating peritropical conditions. Lower Cretaceous limestones are apparently missing in the innermost Hellenides. In the Pelagonian Domain s.l., on the other hand, Upper Jurassic to Lower Cretaceous limestones are found in some places, with same characteristics as in the Epanomi-New Iraklia boreholes. On the contrary, the Upper Eocene to Lower Oligocene clastic series of the boreholes can be correlated with the Axios (=Vardar) molassic basin, inline with its present situation. During the Mesozoic, the Epanomi area therefore belonged to a micro-block, next to the NE margin of the Pelagonian Domain, in contrast to earlier interpretations. Its present time position results from Early Cenozoic tectonic phases.     

Foraminiferan tests and dasycladalean thalli as cryptic microhabitats for thaumatoporellacean algae from Mesozoic (Late Triassic–Late Cretaceous) platform carbonates

Thaumatoporellacean algae are widespread constituents in Middle Triassic–Cretaceous shallow-marine carbonates of the Tethyan realm. Based on various examples from Mesozoic limestones of Mediterranean platforms (e.g., Dinaric, Apenninic, Apulia) and rare records of Iberia (Pyrenees), Saudi Arabia and Mexico, it is shown that thaumatoporellaceans commonly dwelt as cryptoendoliths in the tests of larger benthic foraminifera and the thalli of dasycladalean algae. Their high morphological plasticity allowed the test invasion and the adaptation to the available interior spaces (chambers, apertures). The temporal distribution of cryptoendolithic thaumatoporellaceans with first records in the Late Triassic, shows acme intervals in Early–Middle Jurassic and Early–Late Cretaceous times. Within the foraminiferans, the thaumatoporellaceans were erroneously considered as an integral part of the test, respectively, phrenoteca-like structures (species Biokovina gradacensis) in the Lower Jurassic and trematophore (species Scandonea? mediterranea) in the Upper Cretaceous. Therefore, the presence of phrenoteca-like structures in the Biokovinidae, being part of the family diagnosis, is challenged. The comparably thin walls of the cryptoendolithic thaumatoporellacean algae are interpreted as an adaptation to the poorly illuminated microhabitats (photoadaptation) in order to maximize light capture for photosynthesis.     

A reconsideration of the origins of the 'typical' Cretaceous inoceramid calcitic hinge plate in the light of new ultrastructural observations from some Jurassic 'inoceramids'

Abstract:  Marked differences occur between the hinge plates of Jurassic and Upper Cretaceous British 'inoceramid' species. Albian and Upper Cretaceous inoceramids had the poiriform calcite hinge plate with closely spaced resiliifers that is widely associated with this extinct bivalve family. The whole structure was dominated by compressible ligament. Jurassic species, in contrast, had an ultrastructurally less familiar aragonite hinge plate with widely spaced resiliifers and a ligament reminiscent of Isognomon with equally spaced elastic and compressional components. The wider taxonomic relationships of the Inoceramidae still remain uncertain, although the majority of the evidence links the family to the Pterioida. This study, however, suggests that the ancestral inoceramid did not necessarily have a calcitic hinge plate, but rather that a Jurassic 'inoceramid' species could have been developing such a structure via an aragonite precursor. Observations on British Kimmeridgian 'inoceramid' specimens indicate that calcite was being incorporated into the aragonite hinge plate by these times. Structures in the ligamentat of Jurassic species suggest that the fundamental change in mineralogy was initiated by valve architectural modification at the byssal notch, linked to inoceramid epifaunalism. Worldwide poor preservation of Lower Cretaceous inoceramids makes it very difficult to further prove this hypothesis via intermediate evolutionary stages leading to the fully poiriform calcite hinge plate observed in Albian and Upper Cretaceous species of Inoceramidae.     

The jaw apparatus of the Cretaceous ammonite Reesidites

Jaws are preserved within the body chambers of three specimens of a collignoniceratid ammonite Reesidites minimus (Hayasaka and Fukada) from the Upper liuoniaq of Hokkaido, Japan. Light microscopic and SEM observations of sections indicate that both upper and lower jaws consist mainly of a thick, double-walled chitinous lamella with a beak-like anterior projection. The outer chitinous lamella of the lower jaw is covered by a thick calcareous layer. The jaw apparatus of this species morphologically resembles aptychus-type jaws of Jurassic ammonites, but is distinguished by the presence of an anterior beak-like projection with serrated ridges and grooves in the lower jaw. These observations strongly suggest a biting ability in this species.     

Ostéologie et affinités de Trematochampsa taqueti (Crocodylia,Mesosuchia) du Sénonien inférieur d'In Beceten (République du Niger)

Among the abundant remains of Mesosuchia that have been yielded by the early Senonian locality of In Beceten (Niger), the most numerous belong to the species Trematochampsa taquetiBuffetaut, 1974. The osteology of this species is described here. This medium-sized crocodilian, with a moderately elongated skull, is characterized, among other features, by its antorbital fenestra, its surangular-quadratojugal articulation, its slightly displaced post-orbital pillar, its teeth with wrinkled enamel, and its amphicoelous vertebrae. In its general outlook, this animal is rather reminiscent of the Goniopholidae, from the Upper Jurassic and the Cretaceous of Laurasia, but it is more primitive than them, and resemblances are probably due to convergence phenomena. The family Trematochampsidae is probably essentially Gondwanian, and could persist until the Senonian thanks to a certain isolation from Laurasia, where more progressive Crocodylia became predominant much earlier than in Africa and South America.