> library(survival)

> coxph.fit<-coxph( Surv(LT50duration, eventLT50, type=c('right')) ~ meanTDG + maxdepth + meantempC + gas.ratio + maxdepth*meanTDG , na.action = na.omit, data=LT50data, weights=LT50replicates)
> coxph.spline<-coxph( Surv(LT50duration, eventLT50, type=c('right')) ~ pspline(meanTDG) + maxdepth + meantempC +  gas.ratio + maxdepth*meanTDG , na.action = na.omit,  data=LT50data, weights=LT50replicates)

> anova(coxph.fit,coxph.spline)

Analysis of Deviance Table
 Cox model: response is  Surv(LT50duration, eventLT50, type = c("right"))

Model 1: ~ meanTDG + maxdepth + meantempC + gas.ratio + maxdepth * meanTDG
Model 2: ~ pspline(meanTDG) + maxdepth + meantempC + gas.ratio + maxdepth * meanTDG

  loglik  Chisq Df P(>|Chi|)
1 -632.83
2 -619.24 27.174