, 2009), a detailed interspecific study found no evidence for a similar effect between species (Nicholson et al., 2007). Another problem with Acalabrutinib particular relevance to the present discussion is that multiple contemporaneous, closely related species with overlapping geographic ranges is consistent with traits evolving under sexual selection as well as species recognition

(i.e. multiple, co-existing taxa within a clade spawning new forms distinguished primarily on the basis of sexually selected mating signals). More problematic still is the fact that the dinosaur fossil record does not support the second prediction of Padian & Horner. They cite several examples of multiple, contemporaneous,

closely related dinosaur species bearing bizarre structures (2010: table 2). Yet most of these examples span millions of years and a range of environments, bringing into question whether or not the animals within a given clade actually co-existed in the same habitats. Of the examples given, by far the best documented – stratigraphically and paleontologically – is the Late Cretaceous (Campanian) Dinosaur Provincial Park in Alberta, Canada, for which the authors cite the occurrence of 10 hadrosaur species, four pachycephalosaur species and at least 10 ceratopsid species. Yet a recent review of Dinosaur Park Formation ornithischians Selleck RG 7204 (Ryan & Evans, 2005) concluded that many dinosaur taxa had relatively short species durations (<1 million years), and that the dinosaurs may be divided into successive faunal communities characterized

by one or two species each of hadrosaurines, lambeosaurines, centrosaurines and chasmosaurines (the single exception is a time slice that may record three co-occuring lambeosaurines). This conclusion appears to apply to all reasonably well-sampled formations from the Campanian Western Interior Basin of North America (Gates et al., 2010; Sampson & Loewen, 2010), arguably the best sampled continent-scale ‘slice’ of time and geography known for the entire Mesozoic. To highlight a single example from the Dinosaur Park Formation (Ryan & Evans, 2005), it seems difficult to maintain that the centrosaurine ceratopsid Centrosaurus apertus evolved its Edoxaban highly derived horn and frill morphologies in order to distinguish conspecifics from individuals of its contemporary, the chasmosaurine Chasmosaurus russelli, with which it last shared a common ancestor more than 5 million years prior. Depending on the primary mode of macroevolutionary change (cladogenetic vs. anagenetic), it is certainly conceivable, perhaps even likely, that sister taxa within these clades (e.g. C. apertus and Styracosaurus albertensis within centrosaurine ceratopsids) lived briefly side-by-side in ecological time.