Tuesday, November 14, 2017

(Belated) Extinct Animal of the Week: Panphagia

From Infogalactic:  Panphagia is a genus of sauropodomorph dinosaur described in 2009. It lived around 231 million years ago, during the Carnian age of the Late Triassic period in what is now northwestern Argentina. The name Panphagia comes from the Greek words pan, meaning "all", and phagein, meaning "to eat", in reference to its inferred omnivorous diet. Panphagia is one of the earliest known dinosaurs, and is an important find which may mark the transition of diet in early sauropodomorph dinosaurs.

My first thought was; hey; 231 million years ago isn't in the Carnian, its in the Ladinian!  But I notice that in 2012, the IUGS seems to have updated the dates. My chart is now out of date! My second thought was that while I don't know of anyone who disagrees that Panphagia protos was probably a basal sauropodomorph, at the same time, the position of the Basals is really ugly and subject to a lot of uncertainty and disagreement.  Wedel and Hallet's new sauropod book, for instance, claims Eoraptor is such a basal, while Nesbitt et al.'s big definitive cladogram has it as a basal therapod.  It's also been called a basal saurischian, a basal dinosaur, and even a non-dinosaurian sister group.  As Wedel and Hallett point out, the whole assumption that carnivory is ancestral to Dinosauria comes into question now that we know that the silesaurs are a closer sister group to the dinosaurs than little Lagosuchus after all.  This suggests that herbivory could easily be the ancestral condition for dinosaurs instead of carnivory—or at least omnivory.  This would also help explain why it's so hard to sort out who belongs where at the base of the dinosaur (or at least saurischian) family tree.
In any case, Panphagia is an interesting little character; not much larger than a chicken, and apparently biologically adapted to an omnivorous diet—we think (although studies of iguanas and other animals with similar teeth show us that maybe that's not quite as cut and dried as we've tended to think in the past.  The same is true for almost all of the dinosaurs coming out of the Ischigualasto Formation in La Rioja and San Juan Argentina; it's the same formation as the original herrerasaurs (which come in more genus names than are valid, no doubt), Edodromeus, Eoraptor, and some slightly more defined animals, like Pisanosaurus and Chromogisaurus.  Of these, Panphagia's position as a sauropodomorph seems fairly secure compared to some of the alternatives, which have bounced around all over the place.  Whether or not Eoraptor turns out to be even more basal, or part of some other group, Panphagia seems fairly secure, as does our interpretation of its likely omnivorous diet. 

In any case, Panphagia would have closely resembled several other non-dinosaurian relatives from the same time and area, roughly.  Lagerpetids and silesaurs are also in the formation, as well as aetosaurs, rauisuchians, ornithosuchians, poposaurs, proterochampsians, rhynochosaurs, etc.  Cynodonts and dicynodonts with a fair degree of diversity are also found here, as are temnospondyl amphibians.  Rhyncosaurs and herbivorous cynodonts are the most common fossils found here, and herrerasaurs seem to be the most common carnivores.  The Ischigualasto area was a volcanically active floodplain with plenty of rivers and monsoon-style seasonal rains.  At the time, of course, it was part of the supercontinent of Pangaea, and it would have been located fairly close to the western Panthalassic Oceanic coastline—close to the back of the "pac-man" shape that Pangaea had.

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