Varanops brevirostris (Williston 1914) Late Permian ~260 mya, over 1 m in length was derived from a sister to the much smaller, Protorothyris and phylogenetically preceded Varanodon and Archaeothyris.
Distinct from Protorothyris, the skull of Varanops was relatively smaller. The orbit length was shorter than the postorbital skull length. A large lateral temporal fenestra was present. The quadratojugal was essentialy straight. The frontal length to width ratio was less than 4:1. The jugal and postorbital extended as far as the nearest part of the posterior skull roof. The occiput was anterior to the jaw joint. The internal nares were close together. A relatively solid palate was present. The medial premaxillary teeth were larger than the lateral ones. A retroarticular process was present and it was raised. The mandible included a fenestra.
The cervical ribs were not robust and did not enter the torso. Transverse processes appeared on each vertebra. The dorsal ribs were much larger, enclosing a much larger torso. The sacral spines were taller than the acetabulum diameter.
The scapulocoracoid was relatively robust and larger in keeping with the deeper torso. The manus and pes were subequal in size and the fingers and toes were relatively shorter and more robust.
The ilium was longer than tall and more robust overall. Metarsal I was less than half the length of metatarsal III. Pedal 5.1 did not extend beyond mt IV.
Varanops's diet included large vertebrates rather than insects. Sturdy limbs and a robust torso gave it the strength to chase and kill prey as large as itself, nipping meat off the bone with its elongated incisors. It was too large to clamber on fallen timber, but probably preferred flat land and perhaps water.
Chronologically the Synapsida (including mammals and humans) had their start with Archaeothyris 50 million years earlier. Varanops and Varanodon represents a primitive clade that split off earlier and survived for tens of millions of years. So such lack of change in so much time is notable.
All prior textbooks and studies included Casea, Eothyris and Odaleops as basal members of the Synapsida, but they are unrelated as shown by the present tree. The present study is the first to present this new nesting. |
