Hairy Museum of Natural History

While temnospondyls seemed particularly suited towards making their way as aquatic ambush predators, during the Carboniferous and Permian periods they underwent a few experiments in alternative lifestyles. One of the most successful of these evolutionary excursions was undertaken by a temnospondyl family known as the Dissorophids.

The Dissorophids were more fully committed to a terrestrial lifestyle than most other temnospondyls. They developed a series of overlapping bony plates that covered their spinal column, which added strength to their backbones as they clambered across the Paleozoic landscape, and helped protect them from larger predators. Based on this feature, some workers have informally referred to the group as “armadillo toads.”

Big-headed Cacops is one of the best known dissorophids, but the showiest was undoubtedly Platyhystrix, shown here running from the varanopseid pelycosaur Ruthiromia. Platyhystrix (whose name means “flat porcupine”) had a sail along its back supported by dramatically curved and textured extensions of its vertebrae, and in lieu of bony plates along its back it had roughened bony armor stuck to its ribs. While this might not have been sufficient protection from the largest predators of the Permocarboniferous, it doubtless allowed Platyhystrix to cut quite a profile as it strutted through the swamps.

Dissorophids like Cacops and Platyhystrix went extinct at the end of the Permian, but they may have spawned a legacy more successful than any of their temnospondyl kin. Some researchers think that all modern amphibians—frogs, toads, salamanders, and the wormlike caecilians—can trace their ancestry back to these “armadillo toads.” Other scientists disagree, and conclude that temnospondyls ultimately left no descendants that are alive today. Whatever the case, temnospondyls were a particuarly successful group of early terrestrial vertebrates whose lineage stretched from the Early Carboniferous to at least the Middle Cretaceous—350 million to 100 million years ago. Few other vertebrate groups can claim such longevity or tenacity.

—Matt Celeskey.

File under: Carboniferous, Permian, Tetrapods.

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Tracks that were probably made by temnospondyls are known from many Pennsylvanian and Permian sediments. Track fossils are given their own scientific names because it is almost impossible to say for certain what specific animal made a particular track, although the age and shape of a footprint can often suggest what general type of animal made a certain type of track.

This image was based on two different types of tracks found in Permian sediments in southern New Mexico. A small temnospondyl leaving behind Limnopus tracks confronts a scorpion, who has made a series of Permichnium traces. This specific confrontation is not based on a particular trackway, although some paleoichnologists (scientists who study fossil footprints) have suggested that fine-grained rocks from the Permian of New Mexico show evidence of predatory interactions between vertebrates and invertebrates. The direct evidence for such confrontations is equivocal. But it seems certain that scenarios like this would have taken place along sandy shorelines towards the end of the Paleozoic, whenever two such disparate trackmakers scuffled over a few square feet of beachfront property.

—Matt Celeskey.

File under: Carboniferous, Permian, Tetrapods.

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University of Michigan paleontologist Jeffrey Wilson has recently published a new study of the skull of Nemegtosaurus.

Nemegtosaurus belongs to a group of sauropods known as titanosaurs, which were extremely diverse yet remain relatively poorly known. Most well-known sauropods, like Apatosaurus, Brachiosaurus, and Diplodocus, had their heyday during the Jurassic Period, then went into decline at the beginning of the Cretaceous period which followed. Titanosaurs, however, thrived while these other sauropods went extinct, and titanosaur fossils are known from Cretaceous rocks on every continent.

Exactly why this happened is still uncertain. Wilson’s study shows that the Nemegtosaurus skull had a series of openings and grooves at the tip of its snout, which might have had some function in a particular feeding strategy.

Wilson worked with Bonnie Miljour, an artist at the U-M Museum of Paleontology, to create a new reconstruction of the skull of Nemegtosaurus. Their work literally helps put a new face on these enigmatic giants.

Found on Dr. Michael Ryan’s excellent Palaeoblog.

—Matt Celeskey.

File under: Cretaceous, Dinosaurs, Recent Discoveries.

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The temnospondyls were a stubborn group of early amphibians who refused to part with portions of their anatomy that they had inherited from their aquatic ancestors. While their contemporaries were overhauling their fish-grade physiques to take advantage of opportunities available on dry land, the temnospondyls looked at their newly evolved hands, threw them up, and crawled back into the nearest river in an attempt to thwart evolution through sheer amphibious obstinacy.

I am, of course, exaggerating. Temnospondyls were subjected to the same forces of modification and selection that shaped every other animal lineage, and throughout their long dynasty they did undertake some noteworthy evolutionary experiments. But they are unusual in that they retained the complex, multi-part vertebrae and intricately folded teeth that most other backboned animals modified shortly after making the transition from surf to turf. And looking at the flat, toothy, textured skull of a temnospondyl, one gets the impression that instead of wasting their time adapting to their environment, they had decided to hunker down and force their environment to deal with them.

Eryops, shown here lunging after a xenacanth shark, exemplifies the niche that temnospondyls returned to time and time again—that of the “crocamander” or “frogodile”. Long before the first alligators swam through any prehistoric bayou, Eryops and its kin were cruising the Carboniferous waterways. One hundred million years later, when dinosaurs first appeared, a group of temnospondyls called metoposaurs were still prowling the swamps, snapping at prey with heads so broad and flat that they resembled sharp-toothed toilet seats. And one hundred million years after that, when true crocodiles had muscled in on their territory in most of the world, the last of the”crocamanders” were still hunting in the relatively isolated waters of Australia.

Eryops is typically pictured as a squat, fat beast with a large, frog-like head and a somewhat insipid grin. This is probably not entirely inaccurate. However, restorations such as these fail to show the dozens of sharp, recurved teeth that line the edges of its mouth, or the extremely nasty-looking fangs that projected from its palate (a trait shared by all tempnospondyls). This portrait of Eryops, inspired by a skull collected from the Permocarboniferous of New Mexico, was drawn with those features in mind.

More temnospondyls to come…

—Matt Celeskey.

File under: Carboniferous, Permian, Tetrapods.

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Yamaha Motors has an impressive collection of Rare Animal Paper Sculptures as PDFs to download, cut out, and assemble. Clutter up your desk with Giant Armadillos and Little Spotted Kiwis.

—Matt Celeskey.

File under: Miscellany.

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