The two phases of the Cambrian Explosion

Abstract The dynamics of how metazoan phyla appeared and evolved – known as the Cambrian Explosion – remains elusive. We present a quantitative analysis of the temporal distribution (based on occurrence data of fossil species sampled in each time interval) of lophotrochozoan skeletal species (n = 430) from the terminal Ediacaran to Cambrian Stage 5 (~545 – ~505 Million years ago (Ma)) of the Siberian Platform, Russia. We use morphological traits to distinguish between stem and crown groups. Possible skeletal stem group lophophorates, brachiopods, and molluscs (n = 354) appear in the terminal Ediacaran (~542 Ma) and diversify during the early Cambrian Terreneuvian and again in Stage 2, but were devastated during the early Cambrian Stage 4 Sinsk extinction event (~513 Ma) never to recover previous diversity. Inferred crown group brachiopod and mollusc species (n = 76) do not appear until the Fortunian, ~537 Ma, radiate in the early Cambrian Stage 3 (~522 Ma), and with minimal loss of diversity at the Sinsk Event, continued to diversify into the Ordovician. The Sinsk Event also removed other probable stem groups, such as archaeocyath sponges. Notably, this diversification starts before, and extends across the Ediacaran/Cambrian boundary and the Basal Cambrian Carbon Isotope Excursion (BACE) interval (~541 to ~540 Ma), ascribed to a possible global perturbation of the carbon cycle. We therefore propose two phases of the Cambrian Explosion separated by the Sinsk extinction event, the first dominated by stem groups of phyla from the late Ediacaran, ~542 Ma, to early Cambrian stage 4, ~513 Ma, and the second marked by radiating bilaterian crown group species of phyla from ~513 Ma and extending to the Ordovician Radiation

Hyoliths are Palaeozoic lophophorates

Hyoliths are abundant and globally distributed ‘shelly’ fossils that appear early in the Cambrian period and can be found throughout the 280 million year span of Palaeozoic strata1, 2. The ecological and evolutionary importance of this group has remained unresolved, largely because of their poorly constrained soft anatomy and idiosyncratic scleritome, which comprises an operculum, a conical shell and, in some taxa, a pair of lateral spines (helens)3, 4, 5. Since their first description over 175 years ago, hyoliths have most often been regarded as incertae sedis4, 6, related to molluscs7, 8 or assigned to their own phylum1, 2. Here we examine over 1,500 specimens of the mid-Cambrian hyolith Haplophrentis from the Burgess Shale and Spence Shale Lagerstätten. We reconstruct Haplophrentis as a semi-sessile, epibenthic suspension feeder that could use its helens to elevate its tubular body above the sea floor3, 9, 10, 11, 12. Exceptionally preserved soft tissues include an extendable, gullwing-shaped, tentacle-bearing organ surrounding a central mouth, which we interpret as a lophophore, and a U-shaped digestive tract ending in a dorsolateral anus. Together with opposing bilateral sclerites and a deep ventral visceral cavity, these features indicate an affinity with the lophophorates (brachiopods, phoronids and tommotiids), substantially increasing the morphological disparity of this prominent group

A case of the kidney apparatus perfusion as a detector of errors in personnel actions. A graft edema “cure” by perfusion

Utilization of kidneys donated from uncontrolled donors after cardiac death (UDCD) became an additional source of organs for transplantation worldwide in the light of ongoing global organ shortage. Machine perfusion proven to be a promising perspective for selection, rehabilitation and treatment of kidneys from expanded criteria donors, however, exact mechanisms of these effects remains unclear. On presented clinical case we are trying to clarify the essence of them. In 2006-2007 a pilot study was carried out by our team for use of machine perfusion to perform selection of kidney obtained from UDCD and improve their quality. According to study design each couple of grafts were divided and transplanted to different recipients. During ordinary procedure a staff mistake occurred, which, fortunately, helped us to understand one of the treatment mechanisms of hypothermic machine perfusion