Late Devonian Ammonoids Research Articles

LITHOLOGY CONTROLS AMMONOID SIZE DISTRIBUTIONS

ABSTRACT Body-size distributions of organisms across environments in space and time are a powerful source of information on ecological and evolutionary processes. However, most studies only focus on selected parameters of size distributions (e.g., central tendency or extremes) and rarely take into account entire distributions and how they are affected by the collection style and facies. Here we analyze the impact of facies, region, taxonomy, and collection style over size distributions using diameter as a proxy of Late Devonian ammonoids in their entirety using non-metric multidimensional scaling and PERMANOVA based on Kolmogorov distance. The effects are then compared with effects on mean sizes. In all analyses, lithology was the dominant effect, with sizes greater by 59% in marls and by 33% in limestones, as compared to black shales. The effect of complete sampling style was a decrease in size by 11%. Kurtosis was an important parameter differentiating size distributions, with platykurtic distributions in marls and leptokurtic distributions in limestones, suggesting that this parameter may reflect different degrees of time averaging. Most size distributions were positively skewed, but most strongly in marls. Complete sampling led to skewness values close to zero (symmetrical distributions) and high kurtosis. Samples from higher paleolatitudes were on average smaller, but contained outliers with the largest sizes, highlighting the need to analyze entire distributions. Lithology and collection differences need to be accounted for when evaluating size differences across space (polar gigantism) and time (Lilliput effect). Similarly, differences in facies may affect species determination.

Revision of Tornoceras frechi Wedekind, 1918 and consequences for the Late Devonian ammonoid stratigraphy

Revision of Tornoceras frechi Wedekind, 1918 and consequences for the Late Devonian ammonoid stratigraphy

Gigantism in Late Devonian ammonoids from Chahriseh (Central Iran)

Gigantic representatives of the clymeniid genera Hoevelia and Protactoclymenia (Late Devonian ammonoids) with conch sizes up to 50 cm occur in small numbers in shallow-water carbonates at Chahriseh (Central Iran). Comparison with other occurrences of gigantic clymeniids (Central Europe, North Africa) suggests that taphonomic reasons rather than latitudinal effects with differences in sea water temperature and oxygen availability are responsible for this gigantism. The large size of the ammonoids at Chahriseh is interpreted as local phenomenon caused by accumulation of post-mortem drifted specimens. The new species Hoevelia megalomanica is described.

The Late Devonian ammonoid subfamily Paratornoceratinae

Ammonoids of the subfamily Paratornoceratinae are characterised by disc-shaped adult conchs; furthermore they display a wide range of ontogenetic pathways leading to a similar adult conch morphology. The subfamily Paratornoceratinae occurs in the late early Famennian shelf sediments of various regions from the Anti-Atlas of Morocco to the Canning Basin of Western Australia; where endemic species of the genera Paratornoceras and Acrimeroceras appear in stratigraphic succession. We revise the species Paratornoceras lentiforme (Sandberger, 1857) and describe the new species Paratornoceras thuringense Korn, Bartzsch & Weyer n. sp., P. harounense Korn & Ebbighausen n. sp., P. ayense Korn & Buchwald n. sp., P. peterseni Korn & Buchwald n. sp., Acri meroceras hoppeckense Korn & Buchwald n. sp., A. ropicense Korn, Bartzsch & Weyer n. sp. and A. saalense Korn, Bartzsch & Weyer n. sp.

The polyphasic ontogeny of the discoidal Late Devonian ammonoid Acrimeroceras

The Late Devonian ammonoid species Acrimeroceras falcisulcatum and A. stella have similar-shaped discoidal adult conchs. Their conch morphology and its ontogenetic development are described and analysed. Despite great similarities in their adult conch morphology, they can be clearly distinguished by differences in the shape of their juvenile whorl profile and by the growth trajectories of their cardinal conch parameters: conch width index, umbilical width index and whorl expansion rate. Quantification of ontogenetic change in the two species demonstrates that the stratigraphically younger species A. falcisulcatum possesses the less complex ontogeny compared to the stratigraphically older A. stella. The closely related genus Paratornoceras (early Famennian) and the unrelated Late Visean Calygirtyoceras show juvenile conch morphology and ontogenetic trajectories very similar to Acrimeroceras stella. This similarity can be seen as iterative independent unfolding of homoplastic characters, possibly linked to size-dependence of the functional morphology of the conchs.

Rare representatives of new Late Devonian ammonoids from the Rhenish Mountains and the Montagne Noire

The new genera and species of the early late Famennian (Late Devonian) ammonoids Hoevelia schindewolfi n. gen. n. sp. and Beulia wunderlichi n. gen. n. sp. are described from material collected in the Rhenish Mountains and attributed to the new family Hoeveliidae. The genus Falciclymenia Schindewolf, 1923 is revised with the description of the proposed new type species Falciclymenia cabrierensis n. sp. from the Montagne Noire.

The Late Devonian ammonoid Mimimitoceras in the Anti-Atlas of Morocco

Mimimitoceras is the most abundant late Famennian goniatite genus in the Anti-Atlas of Morocco and the Saoura Valley of Algeria. Based on conch morphology, conch ontogeny, suture line and ornament, six new species can be separated, which occur in three successive rock intervals. The new species M. carnatum, M. comtum, M. endocuboide, M. taourirtense, M. alidrisii and M. ibnishaqi are compared with time equivalent Central European species.

A morphometric approach to conch ontogeny of <i>Cymaclymenia</i> and related genera (Ammonoidea, Late Devonian)

Abstract. Representatives of the Late Devonian ammonoid family Cymaclymeniidae were studied for their conch ontogeny. Two methods were applied: (1) the analysis of classical morphometric conch parameters and (2) an outline analysis of the aperture using elliptic Fourier analysis. Application of both methods leads to similar results, allowing a separation of some of the species by means of their ontogenetic pathways. The new species Procymaclymenia ebbighauseni n. sp., Cymaclymenia subvexa n. sp., Cymaclymenia formosa n. sp., Cymaclymenia lambidia n. sp., Cymaclymenia carnata n. sp., Cymaclymenia aulax n. sp., Cymaclymenia serotina n. sp. and Postclymenia calceola n. sp. are described in the systematic part.

Size distribution of the Late Devonian ammonoid Prolobites: indication for possible mass spawning events

Worldwide, the ammonoid genus Prolobites is only known from a few localities, and from these fossil beds almost all of the specimens are adults as shown by the presence of a terminal growth stage. This is in marked contrast to the co-occurring ammonoid genera such as Sporadoceras, Prionoceras, and Platyclymenia. Size distribution of specimens of Prolobites from three studied localities show that, unlike in the co-occurring ammonoid species, most of the material belongs to adult individuals. The morphometric analysis of Prolobites delphinus (Sandberger & Sandberger 1851) demonstrates the intraspecific variability including variants with elliptical coiling and that dimorphism is not detectable. The Prolobites material shows close resemblance to spawning populations of Recent coleoids such as the squid Todarodes filippovae Adam 1975. Possible mass spawning events are discussed in the context of the size distribution and limited geographic range of Prolobites. Finally, the potential fecundity and brooding behaviour of Prolobites is hypothesized using the examples of post spawning egg care in Recent coleoids.

Conch geometry and ontogenetic trajectories in the triangularly coiled Late Devonian ammonoid Wocklumeria and related genera

The species of the genera Wocklumeria and Parawocklumeria are investigated in terms of their conch geometry, intraspecific variability, and ontogenetic trajectories using a rich material. Both genera are closely related, as indicated by a number of characters regarding conch geometry, ornament, and suture line. Some of the peculiar conch characters, including adult modifications, such as opening of the umbilicus, a terminal constriction, lateral narrowing of the mature aperture, and extreme septal crowding that is paralleled by the loss of suture characters can be seen in Wocklumeria. Wocklumeria sphaeroides (RICHTER, 1848) and Wocklumeria denckmanni (WEDEKIND, 1918) are distinguished on the base of degree of triangular coiling in intermediate whorls. Wocklumeria oblivia n. sp. and Wocklumeria boulmanensis n. sp. are newly described from the Anti-Atlas of Morocco.

Late Devonian ammonoids from Ohio and adjacent states

Three late Devonian ammonoid-bearing levels are described from the area of Cleveland, Ohio. These appear to represent the German Platyclymenia, Clymenia and Wocklumeria Stufen, clear evidence for which has been lacking previously in eastern North America. The lowest level, around the base of the Cleveland Shale, yieldsSporadoceras, Cyrtoclymenia, Platyclymeniaand a new species,Pleuroclymenia(?)ohioense. The middle level, near the top of the Cleveland Shale, bearsCymaclymenia, SporadocerasandPrionoceras. The highest level, just above the base of the Bedford Shale, hasPrionoceras quadripartitum. This species, and a fauna of the basal Bedford, have been located also in the area of Columbus, Ohio. AnEpiwocklumeria(?) sp. is recorded from Indiana. Attention is drawn to the international importance of the late Famennian and Lower Carboniferous ammonoid sequence which can now be recognized in Ohio.

A late devonian ammonoid faunula from himachal pradesh, india

From the uppermost parts of the Muth Quartzite Formation the following ammonoids are described which here are reponed from the Himalayas for the first time:Discoclymenia cucullata (v. Buch);Prionoceras (Imitoceras) intermedium Schindewolf;Pr. (I.) cf.rotundum Petter;Cyrtodymenia sp.; andDiscoclymenia striata (Munster). The levels containing ammonoids appear in the Famennian V(Clymenia zone). Their extension up to the earliest Tournaisian(Gattendorfia zone) is not likely although theoretically it cannot be excluded.