Dimorphismus des Jugendkleides und Nestbau beiAgapornis

Ohne Zusammenfassung     

Solgerites Reeside, 1932 (Cretaceous Ammonoidea) a synonym ofForresteria Reeside, 1932, with a revision ofSolgerites brancoi (Solger, 1904) (Cretaceous Ammonoidea) from Cameroon

A revision of the surviving “Barroisiceras” specimens from Cameroon described by SOLGER (1904) suggests thatBarroisiceras brancoi, type species ofSolgerites REESIDE, 1932, including varietiesmitis andarmatus of SOLGER, andBarroisiceras hoberfellneri alstadenensis SOLGER non SCHLüTER are variants of a single species and thatSolgerites is a synonym ofForresteria (Forresteria) REESIDE, 1932, of whichEboroceras BASSE, 1947 also is a synonym.     

Phylogeny of the Permian family Metalegoceratidae (Goniatitida,Ammonoidea)

The paper discusses the evolution of the Permian ammonoid family Metalegoceratidae, and a new phylogenetic reconstruction is proposed. Three subfamilies are recognized in this family: Metalegoceratinae Plummer et Scott, 1937; Pericycloceratinae Zhao et Zheng, 1977; and Eothinitinae Ruzhencev, 1956. The genus Metalegoceras Schindewolf, 1931 is subdivided into three subgenera: Metalegoceras s. str., Mesometalegoceras subgen. nov., and Artimetalegoceras subgen. nov. Five species of the endemic South Chinese metalegoceratids are described: Pseudometalegoceras shangraoense (Zhao et Zheng, 1977), P. liratum (Zhao et Zheng, 1977), P. platyventrum (Zhao et Zheng, 1977), P. spirale (Zhao et Zheng, 1977), and Pericycloceras costatum (Zhao et Zheng, 1977).     

Evolution of the Permian family Spirolegoceratidae (Goniatitida,Ammonoidea)

The evolution of the Permian ammonoid family Spirolegoceratidae is discussed and a new phylogenetic reconstruction is proposed based on new data. Two subfamilies are recognized within the family Spirolegoceratidae: Spirolegoceratinae Nassichuk and Sverdrupitinae subfam. nov. A new genus, Archboldiceras, is proposed to accommodate the Australian species Uraloceras lobulatum and U. whitehousei. Species of the genus Sverdrupites Nassichuk, 1970 are described based on new material from the Volga-Urals Region. The new species S. bogoslovskayae from the Gerkinskaya Formation of Novaya Zemlya previously identified by M.F. Bogoslovskaya as S. amundseni is described.     

The jaw apparatuses of Cretaceous Phylloceratina (Ammonoidea)

The jaw apparatuses of two species of Late Cretaceous Phylloceratina (Ammonoidea), Hypophylloceras subramosum and Phyllopachyceras ezoensis, are described on the basis of well‐preserved in situ material from Hokkaido, Japan. Gross morphological and X‐ray CT observations reveal that the upper and lower jaws of the two species are essentially similar in their overall structure. Their upper jaws consist of a shorter outer lamella and a pair of larger, wing‐like inner lamellae that become narrower and join together in the anterior portion, as in those of other ammonoids. The upper jaws of the two phylloceratid species are, however, distinguishable from those of other known ammonoids by the presence of a thick, arrowhead‐shaped calcified rostral tip. The lower jaws of the two species consist of a short, reduced inner lamella and a large, gently convex outer lamella covered with a thin calcareous layer, the features of which are common with the rhynchaptychus‐type lower jaws of the Cretaceous Lytoceratina. In the presence of a sharply pointed, thick calcareous tip on upper and lower jaws, the jaw apparatuses of the Phylloceratina resemble those of modern and fossil nautilids, suggesting that they were developed to serve a scavenging predatory feeding habit in deeper marine environments. This and other studies demonstrate that at least some Mesozoic rhyncholites and conchorhynchs are attributable to the Phylloceratina and Lytoceratina.     

Aptychi microstructure in Late Cretaceous Ancyloceratina (Ammonoidea)

The microstructure of aptychi (bivalved calcareous coverings on lower jaws) of three genera of Late Cretaceous Ancyloceratina, Baculites, Polyptychoceras and Jeletzkytes is described for the first time on the basis of well-preserved and in situ material from the Western Interior of the USA and Hokkaido, Japan. Optical and scanning electron microscope observations of aptychi on polished median and cross-sections reveal some variation in their relative size, shape and microstructure among the three genera. The aptychus of Baculites is composed of two calcitic layers: one with tilted lamellae and the other one with horizontal lamellae, whereas those of Polyptychoceras and Jeletzkytes consist of a thin layer with horizontal lamellae. Comparison with aptychi (e.g. Laevaptychus) of Jurassic Ammonitina shows that the aptychi of Ancyloceratina differ from those of Jurassic Ammonitina in the smaller number of layers and the absence of a sponge-like structure. We propose for the first time growth models for a sponge-like aptychus of Jurassic Ammonitina and the lamellar aptychus of Cretaceous Ancyloceratina. The remarkable microstructural variation of aptychi observed in Mesozoic Ammonoidea is probably related to the diversity of their modes of feeding and the secondary function of the lower jaws as opercula.     

Phylloceras (Hypophylloceras) (Ammonoidea) from the Turonian of North Germany

PalZ - Representatives of the Phylloceratida are described from the Turonian of North Germany for the first time. The specimens are referred toPhylloceras (Hypophylloceras) sp. All phylloceratids...     

Taxonomic and biostratigraphic re-evaluation ofPerisphinctes internispinosus Krantz, 1926 (Upper Jurassic, Ammonoidea)

The lectotype ofPerisphinctes internispinosus Krantz, 1926, type species ofWindhauseniceras Leanza, 1945, from the upper Middle Tithonian of Cerro Lotena (Neuquén-Mendoza Basin, Argentina) is designated. The type series, housed in the Paläontologisches Institut der Universität Bonn, was originally illustrated by hand-drawings of two of the eleven specimens. The lectotype is illustrated by a photograph for the first time. The specimen is probably a large microconch; the most likely corresponding macroconch appears to beH. aff.steinmanni (Steuer, 1897) from Cerro Lotena.Windhauseniceras internispinosum is the index and guide species of theInternispinosum Biozone, upper Middle Tithonian, most probablyPonti Zone in age. The occurrence in Arroyo del Yeso (Mendoza) below a succession ofMicracanthoceras species includingM. mirum (Leanza, 1945) which is very close toM. microcanthum, strongly supports this correlation. The species occurs throughout the Neuquén-Mendoza Basin and probably also in the Tarapacá Basin, Northern Chile.     

Über den Kieferapparat der Lytoceratacea (Ammonoidea)

The jaw apparati of Paleozoic and Triassic ammonoids are simìlar in shape to parrots’ beaks; they possess sharp cutting-edges and consist of chitinous material. Together with the similar jaw apparati of recent Coleoids, they constitute the Normal-Type of cephalopod jaws. The jaw apparati of the Jurassic-Cretaceous ammonites possess wide, shovel-like lower jaws without cutting-edges. They consist either of an undivided chitinous plate (Anaptychus) or of this and two additional calcitic plates (Aptychi) on its outer flanks. Jaw apparati of this type are here called Aptychus-Type jaws. New finds in the Upper Cretaceous of Japan suggest the existence of a third type of jaw apparatus which is here called the Rhynchaptychus-Type. Jaws of this type are mainly characterized by possession of calcitic rostra on the tips of the jaws. They seem to be restricted to members of the order Lytoceratacea (excluding the Heteromorphs).     

Gastropoden aus dem oberen Toarcium/unteren Aalenium (Jura) von Norddeutschland

Borings from northeastern Germany yielded a gastropod fauna with 31 species from the Upper Toarcian and Lower Aalenian. Eight species have already been described, nine species are new and 14 species are described in open nomenclature. The fauna comes from soft-bottom sediments and is a typical offshore fauna (relatively great distance from the coast, relatively great depth). The fauna has close relationships to faunas of the same age in southern Germany (Franconia).     

The Late Namurian genusCancelloceras (Carboniferous Ammonoidea) and its distribution

The genusCancelloceras (family Gastrioceratidae) comprises three subgeneraCancelloceras, Crencelloceras n. subgen. andMonitoceras differing in conch ornamentation.Cancelloceras is cosmopolitan and regarded as the index genus for the Upper Namurian G₁ Zone, the Yeadonian. The lower boundary of the G₁ Zone is defined by the entry ofCancelloceras (Crencelloceras) branneroides, whereas the first representatives of the genus appeared earlier, in the Middle Namurian R₂ Zone. The upper boundary of the G₁ Zone is marked by the extinction ofCancelloceras and the entry of its descendant genusGastrioceras. Cancelloceras comprises 27 species.     

New ancyloceratidae (Ammonoidea) from the Aptian of the Ulyanovsk region,Middle Volga

A new genus Pseudoancyloceras gen. nov. with the type species P. calinovense sp. nov. and five new species of Ancyloceratidae (Australiceras (Proaustraliceras) elegans sp. nov., Audouliceras vyrystaykense sp. nov., A. brusyankense sp. nov., A. mordovense sp. nov., Tropaeum (Tropaeum) elaurkense sp. nov.) are described from the Aptian of the Ulyanovsk region, Middle Volga.     

Cieneguiticeras, a new genus of Tithonian oppeliids (Ammonoidea, Late Jurassic)

The new genus Cieneguiticeras, assigned to the family Oppeliidae, is described on the basis of Andean lower-middle Tithonian ammonites from Arroyo Cieneguita, west-central part of the Neuquén-Mendoza Basin, Argentina. The macroconchs are closely homoeomorphic with Neochetoceras Spath and the microconchs have a ‘glochiceratid’-type morphology. The stratigraphic range of Cieneguiticeras nov. gen. includes the lower and middle Tithonian by means of a succession of two or three species which are interpreted as members of a phyletic lineage. Ammonites from the Tithonian of Cuba, Mexico and France are more or less confidently included in this new genus.     

Double function of aptychi (Ammonoidea) as jaw elements and opercula

Lehmann, U. & Kulicki, C. 1990 10 15: Double function of aptychi (Ammonoidea) as jaw elements and opercula. Lethaia , Vol. 23, pp. 325–331. Oslo. ISSN 0024–1164.
Aptychi are calcitic coverings on the outer surface of organic ammonite lower jaws. They are similar in shape to that of the corresponding ammonite apertures. This observation and additional features of many aptychi are in harmony with their former interpretation as protective opercula. We suggest that they served as opercula in addition to functioning as jaws. The primary function of the lower jaws was thus secondarily extended to that of protective shields when they acquired their calcitic covering, while as lower jaws their importance dwindled to that of a more passive abutment. Phylogenetically, this seems to have started slowly in some anaptychi and became obvious with the first aptychi. ▭ Ammonites, aptychus, operculum, jaw apparatus, evolution, function .     

Taxonomic revision of the Kimmeridgian (Upper Jurassic) genusMesosimoceras (Ammonoidea) and institution of the new genusPresimoceras (Ammonitina,Idoceratinae)

Presimoceras is a new genus of Idoceratinae. The biostratigraphical range ofPresimoceras is limited to theStrombecki, Divisum and lower part of theAcanthicum Zone within the Kimmeridgian (in the Southern European sense). The genusMesosimoceras (Idoceratinae) was instituted by Spath (1925), withSimoceras cavouri Gemmellaro as type species; this genus is here emended with the institution ofPresimoceras n. gen. The species groupcavouri-risgoviense is preserved in the emended genusMesosimoceras, while the groupherbichiludovicii-teres is accommodated inPresimoceras on account of the radical and numerous differences and the stratigraphical gap betweenMesosimoceras andPresimoceras. As type species of the new genusAmmonites nodulatus Quenstedt is designated. The new genus is here subdivided into three groups of species:herbichi, ludovicii andteres. Phylogenetically,Presimoceras is derived fromPassendorferia, Mesosimoceras fromNebrodites.     

Sexual dimorphism and polymorphism in a Callovian Phlycticeras (Ammonoidea) assemblage of Kutch, India

An assemblage of Phlycticeras Hyatt from a precisely dated zone of Middle Callovian in Kutch, India has been analyzed. Systematic study reveals that this sample can be divided into two size groups. The larger set shows different adult modifications leading to ornamental polymorphism. Polymorphs are very similar, if not identical, to different chronospecies of Europe, which range between Middle to Upper Callovian. They are grouped under well-known Phlycticeras polygonium (Zieten). The group of smaller specimens on the other hand, strongly resembles a species, which has been previously described as Phlycticeras schaumburgi (Waagen) from the younger Upper Callovian horizons in Kutch. It has a peculiar ‘rooster’-like septicarinate keel in the venter near adult aperture. Phlycticeras-Oecoptychius have been considered as a possible dimorphic pair since long, but here shown to have many inconsistencies to support these views. Instead, sexual dimorphism is explored within Phlycticeras and P. polygonium-P. schaumburgi is proposed as possible antidimorphs. A similar association is found in different stratigraphic assemblages of Europe. Interestingly these two morphs show parallel evolutionary changes within the Phlycticeras genus.     

Hourcquia Collignon, 1965 (Cretaceous Ammonoidea) from the upper Turonian of the southern United States

Hourcquia Collignon, 1965, previously described only from the upper Turonian of Madagascar, Venezuela, South Saghalien and Hokkaido, Japan, is documented from New Mexico and Texas in the United States. The material is referred to a single variable species,H. mirabilis Collignon, 1965, previously known only from Madagascar and Hokkaido, Japan.