Archegosauroids; The Frogodiles, and the first animals with a Crocodile type form
3 years of digging into papers and learning how to search Russian databases later, we got here basically the entirety of Archegosauroidea
- Prionosuchus in blue, smaller than usually depicted but with a much more robust skull. Older depictions off *Platyoposaurus watsoni* were done before the other Brazilian archegosaur, *Bageherpeton longignathus*, was discovered. Living close in proximity to Prionosuchus, it also shares interesting anatomical features, and the overall skull morphology fits better for the stray Prionosuchus bones. The larger specimen has a decent amount of material, but very little data. The information of a 105mm rostrum width, when reconstructed off smaller Prionosuchus, yields a 140cm long skull, which fits with the only other measurement (a 3cm long vertebra), and an approximately 4.9 - 5.7m long body (Depending on whether you scale to match Platyoposaurus' skull width, or skull length)
- *Platyoposaurus stuckenbergi* in purple, consistently coming out as the second largest Archegosaur. Skulls consistently cone in a size range from 30 - 70cm, with a reported 120cm long skull. The measurements for this are unconfirmed and from the late 1900s, but the same can be said about Prionosuchus so I included it regardless.
- *Bageherpeton longignathus* (pink) was the Rosetta stone for figuring this out. While not particularly large, it has some incredibly bizarre features, most importantly its bizarre mandibular symphysis. While in other Archegosaur mandibles, the symphysis usually is about 10 - 15% of the length, with Platyoposaurus reaching about 30%, Bageherpeton's mandible appears to have about 60 - 80% of the length of its mandible as symphysis. This alone is enough to be weird, but alongside this, the symphysis has developed into an elevated bar, while the alveolar platform of the dentary has reduced, and results in the teeth nearly sticking out sideways. This is likely an adaptation for piscivory, with the denticles on this elevated bar providing a secondary surface for prey restraint, combined with the enlarged teeth and many tusks of the upper palate.
However, with Bageherpeton, once compared to Prionosuchus, some very weird trends align.
- A significantly elongated prefrontal region
- Instead of an elevated mandibular bar, Prionosuchus possessed an extended *palatte* with a dense coverage of denticles.
This would fill the same overall mechanical function, and with how enlarged the teeth are proportionally near the terminal end of the jaw, could potentially imply the addition of both the mandibular bar, AND the elevated palate. This would create a secondary region of grip for slippery fish, while also stabbing deeply with large teeth, and impaling with the large tusks (sizeable enough that the mandible of Bageherpeton has explicit grooves in the bone to help fit). Combined with the still extremely elongate jaw, and the terminal end of the mandible (the spoon) in Platyoposaurus featuring a whopping 10 gigantic tusks (5 on each side), Prionosuchus could very well have been an incredibly specialized fisher.
Next up on the table!
- *Kashmirosaurus ornatus*, white. Kashmirosaurus is known from 3 skulls of varying completeness, all of which are from Larval forms. While this alone isn't noteworthy, what is noteworthy is their size. Developmentally, these 90 - 110mm long skulls are about equivalent to a 45mm long Archegosaurus larva, barely even started development. By crossreferencing skull width throughout development with the *incredibly* rigorous ontogeny known for *Archegosaurus decheni* (Florian Witzmann 2006), a reliably skull width of 30.3cm was able to be achieved. Unfortunately, skull length in Platyoposaurines, as demonstrated above, is extremely variable, so instead of attempting a proper reconstruction I just winged it and stretched the image of the skull. Based off of actual ontogenetic patterns in Archegosaurus, it is likely that *Kashmirosaurus ornatus* would be intermediate between Platyoposaurus and Collidosuchus, with a narrower snout than Collidosuchus, thicker than Platyoposaurus, but with nostrils migrated further up the snout than in Archegosaurus and Collidosuchus (or more accurately, an elongated prefrontal bone). Likely a 50 - 60cm long skull would be expected
- Bashkirosaurus is another Larval taxon like Kashmirosaurus. Overall unremarkable, it is less complete, less mature, and less robust. Would likely resemble something similar to *Platyoposaurus watsoni* when adult, in size and shape
- Melosaurus: A thick Archegosaur, black. 1/3 species (kamaensis) may have been predominantly terrestrial
- Collidosuchus: A robust Archegosaur, transitional between Archegosaurus type forms and Platyoposaurus type forms. While it existed alongside *Platyoposaurus stuckenbergi*, it adapted to a more robust form, with some minor adaptations for movement on land. This, and *Melosaurus kamaensis* are the only Archegosauroids, even amongst Tryphosuchus and Konzhukovia, which are omitted from the graph