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re: Effigia placement



I tested the placement of Effigia and found it nested with Ticinosuchus,
which is the sister taxon to the aetosaurs, Aetosaurus and Stagonlepis.

I noted the following from the pdf:

The postfrontal is probably present. Two identical ?cracks? suggest so.
They extend almost to the prefrontals.

The postorbital portion of the skull is rounded posteriorly and appears
to be rotated ventrally, so the upper temporal fenestrae open more
posteriorly. Norrell and Nesbitt ?fixed? it in the recon. When left
alone the jugal descends.

In dorsal view the rostrum has a 90º divergence angle and the rami
appear rather straight, but the reconstruction rounds it. Maybe the
ventral view shows this better.

Like Effigia, Ticinosuchus also has an enlarged orbit, an offset femoral
head, lacrimal separate from frontal, posteroventral rotation of
squamosal, the posterolateral/ventral portion of the pmx is greatly
reduced.

Like Effigia, Aetosaurus has the anteroventrally rotated quadrate, the
anteriorly elongated ilium, tiny manus, enlarged naris, brevity of the
dentary, length of the mandibular fenestra, reduced premaxillary teeth,
ascending retroarticular process.

Were armor plates or scutes found? I overlooked the note if so.

To move Effigia closer to aetosaurs requires one more step. To move it
to the base of the Ticinosuchus + aeotosaurs requires 5 more steps. To
move it close to Lotosaurus requires 13 more steps. The clade
Ticiniosuchus + aetosaurs is the sister to the Archosauria,which
includes Turfanosuchus + (Dinosauria + Crocodylomorpha).

The use of suprageneric taxa in Nesbitt and Norrell 2006 is the probable
reason for their oversight and error.

Would have been interesting to see the strange mandibles, but they were
only reconstructed. This also gives kudos to PAUP which identified a
sister taxon relationship between two overall and at first glance
unlikely sisters.

David Peters
St. Louis