Convergent Evolution Among Reptiles – part 1

Convergence in evolution/biology (aka homoplasy) is the independent evolution of similar features in species of different lineages.  Wiki examples include the evolution of flight in various tetrapods;  ichthyosaurs, dolphins and sharks

Here, as we shall see below,
are several reptile taxa converging with others. Unfortunately,
many of these honodairings are not recognized as examples of convergence among traditional paleontologists. Those scientists still lack their own large reptile tree to test relationships. The data deniers among them continue to avoid testing these touchy subjects despite  online publication several years ago.

  1. Tritosaurs and protorosaurs: Tritosaurs are a clade of lepidosaurs while protorosaurs are a clade basal to archosauriforms. Several tritosaurs, such as Tanystropheus, Macrocnemus, Cosesaurus, Langobardisaurus, Longisquama and pterosaurs have been (and still are in some circles) considered protorosaurs, like Protorosaurus and Prolacerta. The two clades do share a long list of traits developed in convergence, but the large reptile tree demonstrates their separation going back to basal amniotes. Tritosaurs have an ossified sternum and often an elongate p5.1 lacking in protorosaurs. Wiki reports, “Protorosaurs are distinguished by their long necks formed by elongated cervical vertebrae, which have ribs that extend backward to the vertebrae behind them. Protorosaurs also have a gap between the quadrate bones and the jugal bones in the back of the skull near the jaw joint, making their skulls resemble those of lizards. Whether or not protorosaurs represent a monophyletic group (i.e. a distinct evolutionary grouping within Archosauromorpha) is uncertain. Only recently has Protorosauria been defined in a phylogenetic sense as the most inclusive clade containing taxa such as ProtorosaurusMacrocnemus, and Tanystropheus.” Perhaps due to this convergence, protorosaurs in Wikipedia nest close to lepidosaurs and rhynchosaurs (see #2).
  2. Rhynchosaurs, trilophosaurs and protorosaurs: In like fashion, rhynchosaurs, like Mesosuchus, Rhynchosaurus and Hyperodapedon, have been traditionally allied with protorosaurus, but the large reptile tree demonstrates rhynchosaurs are derived from Rhynchocephalians (aka Sphenodotians) like Clevosaurus, with Trilophosaurus and Azendohsaurus related to the transitional taxa. Again, the last common ancestor was a basal amniote. At the rhynchocephalian/rhynchosaur transition neotony produced teeth with roots, rather than teeth fused to the jaws, as seen in basal rhynchocephalians.
  3. Caseasaurs and synapsids: Caseasaurs, like Cotylorhynchus have long been associated with basal synapsids, like Edaphosaurus. The large reptile tree nests caseasaurs with millerettids, like Australothyris and Acleistorhinus, both of which also have lateral temporal fenestra developed by convergence with synapsids.
  4. Turtles, armored placodonts and sinosaurosphargids: These three clades independently developed a carapace (shell) to cover the dorsal region of the postcrania. Turtles, like Meiolania, arose from pareiasaurs like Sclerosaurus. Armored placodonts like Placochelys and Henodus arose from Placodus. Sinosaurophargids, like Sinosaurosphargis, arose from unarmored Adelosaurus and Claudiosaurus.
  5. Champsosaurs, Parasuchians (phytosaurs) and Crocodiliformes (crocodilians): These three clades independently evolved a long low skull and a long slow body and tail. Parasuchians, like Parasuchus, had nostrils close to the eyes. Crocs, like Caiman, and champsosaurus, like Champsosaurus, had nostrils close to the tip of snout.
  6. Draco volans and prehistoric so-called rib gliders: Draco volans is a small lizard with enormous ribs able to open laterally for gliding. Similar, but different, is the clade of basal lepidosauriformes between Coelurosauravus and Xianglong that glide with enormous dermal extensions.
  7. More later.

And now a word from Carl Sagan (writing in the Demon Haunted World).
“Science has built-in error-correcting mechanisms—because science recognizes that scientists, like everybody else, are fallible, that we make mistakes, that we’re driven by the same prejudices as everybody else. There are no forbidden questions. Arguments from authority are worthless. Claims must be demonstrated. Ad hominem arguments—arguments about the personality of somebody who disagrees with you—are irrelevant; they can be sleazeballs and be right, and you can be a pillar of the community and be wrong.”


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.