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|Morphology||Ecology and taphonomy||External Literature Search||Age range and collections|
If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
|M. Stein and J. S. Peel 2008||Examination of the type suite illustrated by Blaker et al. (1997, fig. 7) indicates shortening, stretching and oblique
distortion of individual specimens, presumably as a result of
tectonic deformation. Thus, the holotype is antero-posteriorly
shortened relative to the paratype illustrated here (Fig. 2A).
The presence of pleural spines on the lateral border of the
pygidium (Fig. 2A) sheds doubt on the reported presence of
seven thoracic segments in the holotype (LACMIP 7716) of P.
triangulata. The tagma boundary between thorax and pygidium is not readily identified in that specimen (Fig. 2B). At least one
of the supposed thoracic segments may belong to the pygidium.
For other specimens (e.g. LACMIP 7417, 7418), seven thoracic
segments can be confirmed. As the holotype specimen is larger than the remainder, it seems unlikely that it represents a late
meraspis. It should be noted that the cephalothoracic boundary is
poorly preserved, the posterior cephalic border being somewhat
deformed. It is possible that the anteriormost thoracic tergite
partly underlies the posterior margin of the cephalon and hence
is not recognized.