In 1878, Edward Cope gave the name
Dimetrodon to a particularly nasty-looking, apparently sail-backed Permian mammal-like reptile. In the earliest years of the 20th century, Charles Sternberg discovered something similar, and had it named
Naosaurus. Subsequently, the American Museum of Natural History had a reconstruction made, and a painting by Charles Knight (below).
As Brian Switek has shown in an excellent blog post, Naosaurus came to be increasingly identified with Dimetrodon, although there were as many reasons to regard it as more equivalent with Dimetrodon's herbivorous contemporary Edaphosaurus, particularly considering the similarity in spine protrusions between the remains of Edaphosaurus and Naosaurus.
Although Ermine Case made this point in his 1910 paper on Dimetrodon, in the same year German paleontologist Otto Jaekel (of later Tendaguru fame) published a decidedly Dimetrodon-like reconstruction of Naosaurus. In the Zeitschrift der Deutschen Geologischen Gesellschaft he described what he considered as a new species, Naosaurus credneri, based on remains found near Dresden, Germany. You'll find the paper below. As we're mainly concerned with reconstruction, though, what stands out in this respect is Jaeckel's beautiful, almost impressionistic reconstruction of Naosaurus.
Despite its clearly Dimetrodon-like skull (an assumption, given the absence of cranial elements in the find), Jaekel does not automatically assumes anything about Naosaurus' life habits. Also, there is no trace of a sail. Jaeckel assumes quite a different purpose for the elongated spines:
"In the case of a closed skin connection, the enormously enlarged spines would have been totally without purpose. [...] The spines could only serve an organic and genetic purpose, if they protruded freely from the back of the animal and served as a strong defense for their carrier. [...] I assume, that these animals, like almost all other organisms that are strongly defensively oriented, generally moved slowly across the ground; and that in case of danger, they would by curling up their backs and lateral movement of the vertebral column the spines were drawn widely apart, thus drastically improving their defensive merit". (my translation)
Because Jaeckel also sees a strong connection with Dimetrodon (and comments on the Pelycosaur's apparent global success), his arguments against a sail should also be applied to the latter.
It is difficult to gauge the motivation for Jaeckel's apparent opposition to earlier views on Pelycosaurs; interestingly, around the same time the Berlin Museum's Gustav Tornier - a colleague of Jaekel's - locked horns with the American establishment over the posture of the sauropod dinosaur Diplodocus (about which I will say much, much more at a later time); and likewise, this argument was based on a type of animal which, while originally American, had suddenly become German (or at least German East African) as well - and therefore a good source for scientific appropriation.
References:
- Case, Ermine Cowles (1910), "Description of a skeleton of Dimetrodon incisivus Cope", Bulletin of the AMNH 28, p. 189-196.
- Jaeckel, Otto (1910), "Naosaurus Credneri im Rotliegenden von Sachsen", Zeitschrift der Deutschen Geologischen Gesellschaft 62 (1910), p. 526-535.
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