Ontogeny, evolution and palaeogeographic distribution of the world's largest ammonite Parapuzosia (P.) seppenradensis (Landois, 1895).

The world's largest ammonite, Parapuzosia (P.) seppenradensis (Landois, 1895), fascinated the world ever since the discovery, in 1895, of a specimen of 1.74 metres (m) diameter near Seppenrade in Westfalia, Germany, but subsequent findings of the taxon are exceedingly rare and its systematic position remains enigmatic. Here we revise the historical specimens and document abundant new material from England and Mexico. Our study comprises 154 specimens of large (< 1 m diameter) to giant (> 1m diameter) Parapuzosia from the Santonian and lower Campanian, mostly with stratigraphic information. High-resolution integrated stratigraphy allows for precise cross-Atlantic correlation of the occurrences. Our specimens were analysed regarding morphometry, growth stages and stratigraphic occurrence wherever possible. Our analysis provides insight into the ontogeny of Parapuzosia (P.) seppenradensis and into the evolution of this species from its potential ancestor P. (P.) leptophylla Sharpe, 1857. The latter grew to shell diameters of about 1 m and was restricted to Europe in the early Santonian, but it reached the Gulf of Mexico during the late Santonian. P. (P.) seppenradensis first appears in the uppermost Santonian- earliest Campanian on both sides of the Atlantic. Initially, it also reached diameters of about 1 m, but gradual evolutionary increase in size is seen in the middle early Campanian to diameters of 1.5 to 1.8 m. P. (P.) seppenradensis is characterized by five ontogenetic growth stages and by size dimorphism. We therefore here include the many historic species names used in the past to describe the morphological and size variability of the taxon. The concentration of adult shells in small geographic areas and scarcity of Parapuzosia in nearby coeval outcrop regions may point to a monocyclic, possibly even semelparous reproduction strategy in this giant cephalopod. Its gigantism exceeds a general trend of size increase in late Cretaceous cephalopods. Whether the coeval increase in size of mosasaurs, the top predators in Cretaceous seas, caused ecological pressure on Parapuzosia towards larger diameters remains unclear.

A new comb-star (Asteroidea, Astropectinidae) from the Upper Triassic (Carnian) of China.

A new astropectinid asteroid, Eoastropecten sechuanensis gen. et sp. nov. is described from the Upper Triassic (Carnian) of Sechuan Province, China, based upon marginal ossicles. This occurrence extends the known fossil record of the family Astropectinidae back by 50 myr from the Lower Jurassic, and indicates that a significant part of the radiation of the neoasteroids probably took place around 240 Ma, only 12 myr after the P-T boundary extinction.

The fossil record of the asteroid (Echinodermata) family Chaetasteridae Sladen, 1889 and subfamily Hyalothricinae Fisher, 1911.

The Cretaceous asteroid Arthraster is referred to the living family Chaetasteridae on the basis of similarities in ossicular arrangement in the abactinal disc and arms. Chaetasterina, previously identified as a chaetasterid, is transferred to the family Asterinidae, subfamily Hyalothricinae, and constitutes the first fossil record of the subfamily.