How the ‘Terrible Heads’ Became World Travelers

ByRiley Black
January 17, 2012
5 min read

Earlier this week, paleontologists described another of our distant, ancient cousins. This was no hominin, early primate, or even archaic mammal, but a much, much older variety of creature that would superficially seem to have more in common with terrible primeval reptiles than with us. Named Pampaphoneus biccai, this knobby-headed, 260-million-year-old predator is a clue to one of life’s major events in the time before the dinosaurs.

There is no common name for the peculiar group of animals Pampaphoneus belonged to. Researchers and science writers alike used to call such creatures “mammal-like reptiles”, but that title has been tossed. The old phrase no longer makes any sense.

At a broad level, Pampaphoneus was a synapsid – a member of the major vertebrate group that includes mammals and all creatures more closely related to mammals than to diapsids (the group which contains lizards, dinosaurs, snakes, and other reptiles). The position and arrangement of openings at the back of the skull are a quick and dirty way to tell the difference between the two lineages. Synapsids (including us) have a single opening, while diapsids have two (or at least did ancestrally).

The very first synapsids looked very much like lizards. During the early part of the Permian period, however, these archaic forms were adapted into a wider variety of creatures, including the famous sail-backed synapsids Dimetrodon and Edaphosaurus. These were some of the world’s first large carnivores and herbivores, but, by about 260 million years ago, this particular flavor of synapsid had virtually disappeared. (Late last year, paleontologist Sean Modesto and colleagues described the last known member of the archaic synapsid dynasty – a roughly 260 million year old creature known as a varanopid, found in the strata of South Africa.) But one lineage of these early varieties was adapted into swifter, more specialized forms. These animals, which replaced the likes of Dimetrodon and the varanopids, were called therapsids. Pampaphoneus was one of them.

So far, all we know of Pampaphoneus is the skull. The foot-long fossil has been briefly described by paleontologist Juan Carlos Cisneros and co-authors in PNAS. At the front of the long, oval-shaped skull were a set of pointed, interlocking incisors, followed by prominent canines and a set of eight smaller, serrated teeth. This appears to be the dental toolkit of an omnivore, if not a dedicated carnivore, and makes Pampaphoneus the first large predator found in the Middle Permian deposits of Brazil.

Pampaphoneus was also a relatively well-ornamented hunter. The animal’s skull features small ridges which extend from the eye socket to the upper jaw, and the region around the eyes is decorated with a midline ridge and prominent bosses of bone over the eyes. This ornamentation is consistent with the particular group of therapsid to which Pampaphoneus belongs – the Dinocephalia, or “terrible heads.” In many of these animals, the skull was thickened to create lumps of reinforced bone or strange ornamentation. You have probably seen at least one of these creatures – Estemmenosuchus, a tubby animal with weird, antler-like flanges of bone projecting out of its skull – in museum displays and on book covers. More specifically, Pampaphoneus belonged to a subset of this bizarre group called the anteosaurids, and that conclusion may be a clue to how these animals dispersed through the ancient supercontinent Pangea.

The significance of Pampaphoneus isn’t how weird the animal was, or, as played up to hyperbolic levels by Discovery News, how vicious a killer it might have been. What the discovery of Pampaphoneus indicates is that the particular group of animals to which it belonged quickly spread through Pangea shortly after their origin. The previous discovery of similar dinocephalians in Russia, China, and South Africa – all of which were stuck together in a giant landmass around 260 million years ago – supports the hypothesis that animal lineages spread all over the world to create a cosmopolitan fauna. If you could visit prehistoric South Africa, Brazil, Russia, and China, you would see the same sorts of creatures. There must have been some central connection which allowed the animals to spread between the areas of the continent which would later split and drift to become Asia, Africa, and South America. Pampaphoneus wasn’t the first creature of its kind to be discovered, nor was it the weirdest, but its existence at a critical time and place may help paleontologists figure out how our distant synapsid cousins took over the world.

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Top Image: Pampaphoneus strikes a pose. Image from Cisneros et al., 2012.

References:

Cisneros, J.; Abdala, F.; Atayman-Güven, S.; Rubidge, B.; Sengör, A.; Schultz, C. 2012. Carnivorous dinocephalian from the Middle Permian of Brazil and tetrapod dispersal in Pangaea. PNAS.  (This paper has not yet been released to the public. When the paper is published, it will appear here.)

Modesto, S., Smith, R., Campione, N., & Reisz, R. (2011). The last “pelycosaur”: a varanopid synapsid from the Pristerognathus Assemblage Zone, Middle Permian of South Africa Naturwissenschaften, 98 (12), 1027-1034 DOI: 10.1007/s00114-011-0856-2

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