Before you read this new paper you should read this older one:
Nesbitt, S.J. and M.R. Stocker. 2008. The vertebrate assemblage of the Late Triassic Canjilon Quarry (Northern New Mexico, USA), and the importance of apomorphy-based assemblage comparisons. Journal of Vertebrate Paleontology 28:1063-1072.
I'm afraid that I don't find the identifications in this paper to be rigorously determined (see the Nesbitt and Stocker paper for further discussion) nor the ecological implications to be strongly supported, thus I have doubts about the overall findings in this paper. I'm also not convinced that all phytosaur genera with robust and gracile morphs represent sexual dimorphs (as proposed in passing for Nicrosaurus and Mystriosuchus). The data to support this (i.e. monotaxic bonebeds showing both morphs) simply do not exist with the possible exception of Pseudopalatus pristinus and P. buceros from the Canjilon Quarry (Chinle Formation) of New Mexico. This quarry contains over a dozen skulls of robust and gracile morphs of these two species and has been interpreted first by Colbert (1947) and later by Ziegler et al (2002) as representing sexual dimorphs. Nonetheless the ecological criteria proposed in this new paper suggests different feeding strategies for the dimorphs (which have different dentitions), thus males and females would have different food sources (e.g., piscivorous vs. generalist).
Kimmig, J., and G. Arp. 2010. Phytosaur remains from the Norian Arnstadt Formation (Leine Valley, Germany), with reference to European phytosaur habitats. Palaeodiversity 3: 215–224.
Abstract - Most inferences on phytosaur ecology are based on comparisons with extant crocodilians, in particular with reference to similarities in their skull morphology. In addition, the sedimentary environment of their place of embedding provides information on their life habitat and the potential lifestyle of these animals. Here we report on newly discovered phytosaur remains from the Norian Arnstadt Formation, which support the interpretation that the European phytosaur genera Mystriosuchus and Nicrosaurus had different ecological preferences. While Mystriosuchus, similar to Paleorhinus, was semi-aquatic and piscivorous, Nicrosaurus had a terrestrial lifestyle and probably preyed on tetrapods. Comparing the habitats of the different European phytosaur genera reported in literature, it is also concluded, that Mystriosuchus and Paleorhinus tolerated, contrary to Nicrosaurus, a wide range of salinity.
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