Variation in the Late Triassic Canjilon quarry (Upper Chinle Group, New Mexico) phytosaur skulls: a case for sexual dimorphism

A new phytosaur (Archosauriformes, Phytosauria) from the Lot’s Wife beds (Sonsela Member) within the Chinle Formation (Upper Triassic) of Petrified Forest National Park, Arizona

“…The small size and lack of a rostral crest are characteristics often said to indicate immaturity (Camp, 1930;Long and Murry, 1995). However, the observation of a rostral crest as a simple 'present/absent' character was shown to be a simplification of a complex of taxonomically informative characters (Stocker, 2010) and has also been inferred as a possible sexually dimorphic characteristic for some phytosaurs (e.g., Long and Murry, 1995;Zeigler et al, 2002Zeigler et al, , 2003. Unfortunately, no postcranial material exists for PEFO 34034, and therefore the degree of neurocentral suture closure (sensu Brochu, 1996;Irmis, 2007) cannot be used to determine relative ontogenetic status for PEFO 34034.…”

The vertebrate assemblage of the Late Triassic Canjilon Quarry (Northern New Mexico, USA), and the importance of apomorphy-based assemblage comparisons

“…Following Hungerbühler (2002), P. buceros and P. pristinus are sister taxa based on the following characters: alveolar rim laterally distinctly concave at the lateral extent of maxilla, dorsal edge of parietal-squamosal bar steeply sloping, medial rim of squamosal along supratemporal fenestra (and posterior process) with a sinuous course, and medial half of parietal-squamosal bar ‫ס(‬ lateral wall of supraoccipital shelf) low and basally thickened. However, others (Colbert, 1947;Zeigler et al, 2002) hypothesized that P. buceros and P. pristinus represent sexual dimorphs. Here, we separate the taxa based on recognized character differences, whereas others (e.g., Zeigler et al, 2002) would consider the variation to be within a single species.…”

“…However, others (Colbert, 1947;Zeigler et al, 2002) hypothesized that P. buceros and P. pristinus represent sexual dimorphs. Here, we separate the taxa based on recognized character differences, whereas others (e.g., Zeigler et al, 2002) would consider the variation to be within a single species.…”

The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades

“…Additionally, Zeigler et al (2002Zeigler et al ( , 2003 proposed that Pseudopalatus pristinus represents a sexual morph opposite Pseudopalatus buceros.…”