The case of alleged inversion of septal sutures in ammonites

Reexamination of the specimen of Hystoceroceras varicosum (Sow.) 'var. angolana' Haas with allegedly inverted last septal sutures (Haas, 1941) has proved Schindewolf's (1968) assumption to be correct, i.e., the relevant whorl fragment had been inserted inversely during reassembly. The specimen is a nonpathologic adult H. varicosum angolantrm     

Shell abnormalities in scaphitid ammonites

The kinds incidence of shell abnormalities were investigated in over 2000 adult Late Cretaceous scaphitid ammonites. Most are species of Hoploscaphites Discoscaphites from the Maastrichtian Fox Hills Formation; for comparison, four older species of Scaphites were also studied. Four kinds of abnormalities vary in their incidence among the Fox Hills taxa but display no general trends. (1) Morton's syndrome, shell asymmetry unrelated to external injury, occurs in 3 to 6% of the Fox Hills scaphites. (2) Suture wander. veering-off of the ventral lobe of the suture from the midline of the venter, occurs in most Fox Hills taxa with an incidence ranging from 1 to 11%. (3) Stretch pathology, an attenuation of the shell on the posterior part of the adult body chamber, is confined to Hoploscaphifes nicolleti. (4) Externally inflicted injury, indicated by repaired damage on mature shells, has an average incidence of 10% in Fox Hills scaphites except in the stratigraphically youngest H. nebrascensis H. cheyennewis which approach 25 40% respectively. Good correlation between percent injuries adult size ornamentation is obtained only in Discoscaphifes; all morphs of the co-occurring Hoploscaphites display nearly the same incidence of injuries regardless of their morphologic variation. The stratigraphically youngest H. nebrascensis becomes larger more nodose simultaneously sustains more injuries. However, its dimorph H. cheyennensis remains morphologically unchanged although its incidence of injuries quadruples. These injury data, in themselves, do not support the hypothesis that predators were contributing more heavily to the mortality of Maastrichtian ammonites precipitated their extinction.     

小切口双8字缝合加外牵引法矫正乳头凹陷

目的:介绍一种疗效确切,操作简单,创伤小,矫正乳头凹陷的新术式.方法:设计乳头两侧乳晕横切口,长约1.0～1.5cm松解切断乳头基底纤维素,于乳头基底及乳晕深面行双8字缝合,术后外牵引器牵引一周.结果.31例乳头凹陷患者术后随访3月～2年,均获满意效果.结论:该术式矫正乳头凹陷具有切口小,创伤轻微,操作简单,;疗效确切,不宜复发,并发症少等优点.     

Limpet home depressions in Cretaceous ammonites

Remarkable large pits were found on the shell surface of many ammonites from the Turonian-Maastrichtian sediments of Hokkaido, northern Japan, and Sakhalin, Russia. These pits are (1) round to elliptical in shape; (2) up to 20 mm (usually around 10 mm) in diameter; (3) shallow depressions to deep holes that almost penetrate the shell: (4) occasionally healed by a thin shell blister from inside the shell; (5) often overlapping one another; (6) several to more than 170 in number on one flank of the ammonites; (7) found on both flanks and predominantly on the body chamber and the final volution of the phragmocone; and (8) found only in the two families Pachydiscidae and Puzosiidae, predominantly of more than 300 mm in shell diameter. They can best be interpreted as the home depressions of patellogastropod limpets. The presence of pits on both flanks of the ammonites and those healed from inside the shell strongly suggest that the limpets were dwelling on mature swimming ammonites. Host specifity, their very small shell size compared with the host ammonites, and sparse Occurrence in sediments favor a mode of life as obligate pseudoplankton. We suggest that this remarkable limpet-ammonite association was well established in northwestern Pacific bioprovinces during the late Cretaceous. Taking this live association and the depth limit of algal growth as food for the limpets into consideration, the mature ammonites dwelled or periodically visited the upper layer of the euphotic zone, probably less than around 20 m in depth. *** Ammonite, limpet, home depression, life mode, pseudoplankton, Cretaceous.     

The impossibility and necessity of quality of life research

There are probably a number of reasons why the medical community pays surprisingly little systematic attention to quality of life, either in research or in clinical care. Possibly our society's fascination with high technology and the rescue of endangered lives has encouraged the medical profession to focus on acute care, where their interventions can bring dramatic results. And perhaps because such high-tech acute care requires great knowledge and skill, medical educators have not devoted as much time to educating students and residents about the more mundane matters of medicine. Another reason, on which I will focus here, is the fact that scientific research into quality of life is particularly difficult, methodologically. It does not lend itself easily to the crisp, clean answers for which we strive in basic science. It is "soft," inexact, not "hard." In this article I hope to explain why such research is indeed fraught with hazard. The scientists are attempting a task that is, in a profound philosophical sense, impossible. They have no direct access to the data they most need, and every method of validating their results is fundamentally flawed. Nevertheless, I will also suggest how we can fruitfully undertake such research and, equally important, why we must.     

Swimming abilities of ammonites and limitations

Using some typial ammonites from the Posidonia shales, the aperture orientation, the ideal direction of propulsive thrust, the stability and the buoyancy of the living animals and of the empty shells were investigated as a function of the body chamber length. The emerging limitations indicate that ammonites were hardly suited for a nectonic mode of life. Only in case of favourable conditions empty shells could ascend to the surface and drift.     

Cladistic analysis of Albian heteromorph ammonites

A computer-based parsimony analysis of Albian heteromorph ammonites from the Tethyan and European faunal provinces is demonstrated. The results indicate that whilst Anisoceratidae, Baculitidae, Scaphitidae and Turrilitidae are monophyletic, Hamitidae is not. Previous studies of ammonite phylogenetics have used the coiling mode, ornamentation of the shell and the suture line as sources of characters. Comparison of the consistency and retention indices of these character suites indicates that whereas ornamentation is relatively consistent within clades, suture line morphology is highly homoplastic. The earliest known Sciponoceras , S. skipperae sp. nov., is described.     

The complex nature of progenetic species — examples from Mesozoic ammonites

Several examples of progenetic species among Mesozoic ammonites are investigated. The ammonites are Middle Jurassic kosmoceratids, Upper Jurassic oppeliids, and Upper Cretaceous scaphites. As assessed through outgroup comparison, the progenetic species in each of these examples is characterized by small size at maturity and the presence of morphological features typical of those of the juveniles of more primitive species. However, in none of these examples is the progenetic species a duplicate form of the juvenile stage of more primitive species. There are at least three kinds of features of progenetic species that differ from those of the juveniles of more primitive species: (1) symplesiomorphous features associated with maturation, (2) unique features whose presence is not clearly related to progenetic processes, and (3) unique features that may represent epigenetic outgrowths of juvenile morphology. This novel combination of juvenile. adult. and unique features may endow progenetic species with the evolutionary potential to play a role in the origin of higher taxa. □ Progenesis, heterochrony, Ammon-oidea. Jurassic, Cretaceous.     

Mode of life and habitat of scaphitid ammonites

Scaphitid ammonites (scaphites) are among the most common ammonites in the Upper Cretaceous of the U.S. Western Interior. We have examined species of Hoploscaphites from the Campanian and Maastrichtian Pierre Shale and Bearpaw Shale for clues about their mode of life and habitat. Like most other ammonites, scaphites exhibit determinate growth. The “morphogenetic countdown” begins at the point at which the shell departs from the spiral coil and develops into a shaft and recurved hook. This is accompanied by a reduction in the spacing of ribs and tubercles on the hook and the formation of a constriction and varix at the aperture. Internally, this coincides with a decrease in septal spacing. The common association of scaphites and benthic fossils (e.g., Inoceramus) is interpreted as reflecting oxygen-rich episodes in the history of the Western Interior Seaway. Habitat depths are estimated at less than 100 m, based on faunal associations and studies of the mechanical strength of the septa and siphuncle. Analyses of the isotopic composition of the shells suggest that the animals lived near the sea floor. The high angle of orientation of the aperture at maturity (approximately 100°) seems incompatible with a nektobenthic mode of life. The constricted aperture ending in a thin lip may also have restricted unimpeded movement of long, muscular arms protruding from the aperture. Adults were probably poor swimmers, based on a comparison of their musculature (as inferred from their muscle scars) with that of nautilus (assuming that such a comparison is valid). The lack of a hyponomic sinus on the midventer would have prevented the animal from extending its hyponome below the shell in order to swim forward. As a consequence, scaphites may have been limited in their movement to swimming backward or downward, and may have exploited a low-energy lifestyle, remaining at a single site for an extended period of time. They may have consumed small prey in the water column, which is consistent with the presence of an aptychus-type lower jaw.     

Morphogenesis in ammonites - differences linked to growth pattern

This paper analyzes the relationship existing between septa and ornamentation in ammonites showing two basic growth patterns: cyclic and uniform. In both CMCS there exists a strong correlation between ornamentation size and interseptal distance, both characters, being related to each other through growth rate. Nevertheless, in the case of cyclic growth, regulation mechanisms appear which prevent the formation of non-adaptative structures induced by extreme deviations in growth rate.     

Enigmatic hook-like structures in Cretaceous ammonites (Scaphitidae)

In the last few decades, hook-like structures have been reported in the Mesozoic ammonite family Scaphitidae. Despite their exceptional preservation and debates about their function, no detailed reconstruction has been available until now. For the first time, we describe the composition and details of the morphology of these structures found in the body chambers of six specimens of the Campanian ammonite Rhaeboceras halli (Meek & Hayden) using high resolution x-ray imaging. The hook-like structures are composed of a thin layer of brushite. The base of each hook is open on one side forming an internal cavity, now filled with sediment. The tips of the hooks end in one or two cusps or, rarely, exhibit a blunt end. We used geometric morphometrics to capture the morphological disparity of the bicuspidate morphotypes comprising 98% of the hooks. Principal component analysis revealed chirality among the hooks and a cluster analysis recognized five morphologies. Contrary to the previous interpretation of these structures, we conclude that they are not radular teeth. They are much larger and more variable in size and shape than any known ammonite radulae and completely out of proportion with respect to the size of the jaw. The chirality, the hook-like shape, and the absence of a size relationship between the hooks and the body chambers in which they occur, lead us to propose that these hooks could represent elements of the brachial crown related to copulatory behaviour. If so, these would be the first reported remnants of brachial crowns in ammonites.