Rise and fall of †Pycnodontiformes: Diversity, competition and extinction of a successful fish clade.

†Pycnodontiformes was a successful lineage of primarily marine fishes that broadly diversified during the Mesozoic. They possessed a wide variety of body shapes and were adapted to a broad range of food sources. Two other neopterygian clades possessing similar ecological adaptations in both body morphology (†Dapediiformes) and dentition (Ginglymodi) also occurred in Mesozoic seas. Although these groups occupied the same marine ecosystems, the role that competitive exclusion and niche partitioning played in their ability to survive alongside each other remains unknown. Using geometric morphometrics on both the lower jaw (as constraint for feeding adaptation) and body shape (as constraint for habitat adaptation), we show that while dapediiforms and ginglymodians occupy similar lower jaw morphospace, pycnodontiforms are completely separate. Separation also occurs between the clades in body shape so that competition reduction between pycnodontiforms and the other two clades would have resulted in niche partitioning. Competition within pycnodontiforms seemingly was reduced further by evolving different feeding strategies as shown by disparate jaw shapes that also indicate high levels of plasticity. Acanthomorpha was a teleostean clade that evolved later in the Mesozoic and which has been regarded as implicated in driving the pycnodontiforms to extinction. Although they share similar body shapes, no coeval acanthomorphs had similar jaw shapes or dentitions for dealing with hard prey like pycnodontiforms do and so their success being a factor in pycnodontiform extinction is unlikely. Sea surface temperature and eustatic variations also had no impact on pycnodontiform diversity patterns according to our results. Conversely, the occurrence and number of available reefs and hardgrounds as habitats through time seems to be the main factor in pycnodontiform success. Decline in such habitats during the Late Cretaceous and Palaeogene might have had deleterious consequences for pycnodontiform diversity. Acanthomorphs occupied the niches of pycnodontiforms during the terminal phase of their existence.

A new pycnodont fish, Scalacurvichthys naishi gen. et sp. nov., from the Late Cretaceous of Israel.

A new pycnodont fish from the early-mid Cenomanian, Late Cretaceous, of the 'Ein Yabrud quarry near the village of Beit Eil in Israel is the first pycnodont fish to be described from this locality. Due to the locality where it was found, Scalacurvithys naishi gen. et sp. nov. is considered an inhabitant of reefal waters interspersed with lagoons in the eastern Tethys Sea. Scalacurvichthys naishi is notable for its protruding, hook-shaped first dorsal ridge scale above a large triangular dermatocranium, a deeply sloped and antero-posteriorly shortened skull and bifurcated cloacal scales. The bifurcating scales are a new character previously unknown in pycnodontomorph fishes but have been discovered in two more taxa, which indicates a new type of character that will be useful for future phylogenetic analyses of pycnodontomorph fishes. The new taxon is a member of Pycnodontidae and we conducted a phylogenetic analysis to establish its relationships to other pycnodont fishes. Our results reveal that Scalacurvichthys naishi is a well-resolved member of the subfamily Pycnodontinae. http://zoobank.org/urn:lsid:zoobank.org:pub:04383E2A-551A-4F57-8996-68E06EFA52E0.

New information about late cretaceous pycnodont fishes (Actinoptergyii, Pycnodontiformes) from the near east.

Over roughly the last decade, the Lebanese Cenomanian localities have revealed high numbers of newly discovered pycnodont taxa and even two new families of pycnodonts. Here, two new taxa of pycnodont fishes from the Near East are presented, one from Lebanon and the other from Israel. The new Lebanese specimens show us that Lebanon is still a major site for discovering new pycnodont taxa and can give major insights into their evolution and possible life history. Conversely, the new taxon from Israel shows that lesser known fossiliferous sites may tell us more about the true state of diversity of pycnodonts in the Late Cretaceous.

Possible sexual dimorphism in Pankowskichthys libanicus (Neopterygii, Pycnodontiformes) from the Cenomanian of Lebanon.

Sexual dimorphism is a commonly observed phenomenon in the natural world today but it is far more difficult to determine how common it was in extinct taxa. Here, we describe a new specimen of Pankowskichthys libanicus (Pycnodontiformes, Gladiopycnodontidae) from Haqel, Lebanon (MNHN HAK 1950), which has distinct morphological differences from the holotype of this taxon (IRSNB P9278) which occurs in Hjoula, Lebanon but has also been found at Haqel. Since most of the cranial and pectoral girdle morphologies as well as other postcranial characters are similar to that seen in IRSNB P9278, the distinctive characters seen in MNHN HAK 1950 are unlikely to define a second species but rather represent sexual dimorphic traits.

A remarkable [2.2.2]propellane.

To explore the effects of fluorine substitution on the highly strained [2.2.2]propellane skeleton, a new representative of this ring system, perfluorotricyclo[2.2.2.01,4]octan-2-one ethylene ketal, was prepared by a rapid and quantitative [2+2] cycloaddition to the strained alkene perfluorobicyclo[2.2.0]hex-1(4)-ene. The propellane displays impressive thermal stability, and the vulnerable C-C bond joining the bridgeheads is very resistant to attack by electrophilic reagents. On the other hand, that electron-deficient bond is cleaved quickly at room temperature by a variety of nucleophiles and mild reducing agents. The behavior of this compound contrasts dramatically with that of the only known [2.2.2]propellane lacking fluorine substituents.

A randomized, prospective, double-blinded evaluation of selective bowel decontamination in liver transplantation.

BACKGROUND: Bacterial infection is a frequent, morbid, and mortal complication of liver transplantation. Selective bowel decontamination (SBD) has been reported to reduce the rate of bacterial infection after liver transplantation in uncontrolled trials, but benefits of this intervention have been less clear in controlled studies. METHODS: Eighty candidates for liver transplantation were randomly assigned in a double-blinded fashion to an SBD regimen consisting of gentamicin 80 mg+polymyxin E 100 mg+nystatin 2 million units (37 patients) or to nystatin alone (43 patients). Both treatments were administered orally in 10 ml (increasing to 20 ml, according to predefined criteria), four times daily, through day 21 after transplantation. Anal fecal swab cultures were performed on days 0, 4, 7, and 21. Rates of infection, death, and charges for medical care were assessed from day 0 through day 60. RESULTS: More than 85% of patients in both treatment groups began study treatment more than 3 days before transplantation. Rates of infection (32.4 vs. 27.9%), death (5.4 vs. 4.7%), or charges for medical care (median $194,000 vs. $163,000) were not reduced in patients assigned to SBD. On days 0, 4, 7, and 21, growth of aerobic gram-negative flora in fecal cultures of patients assigned to SBD was significantly less than that of patients taking nystatin alone; growth of aerobic gram-positive flora, anaerobes, and yeast was not significantly different. CONCLUSION: Routine use of SBD in patients undergoing liver transplantation is not associated with significant benefit.