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Are gars champsosaur analogues?

December 6, 2012
Champsosaurus snout. Several workers have compared champsosaur teeth and snout shape to modern Lepisosteus gars.

Champsosaurus snout. Several workers have compared champsosaur teeth and snout shape to modern Lepisosteus gars.

As I’ve discussed previously, champsosaurs were basically like freshwater marine reptiles, being fully aquatic as opposed to modern amphibious crocodillians, turtles and water lizards. I even compared them to modern river dolphins, also fully aquatic freshwater predators with gavialine jaws that incidently also seem to display cryptic behaviour.

It came to my attention recently that a very good modern analogue for neochoristoderes might actually be lepisosteidid fish, aka gars. Again, both are slender jawed, fully aquatic freshwater hunters with cryptic behaviours, but gars take one step further by relying on their pectoral fins for propulsion (just like choristoderes used their paddle like limbs), co-existing with similar crocodillian faunas that occured in neochoristodere fossil sites, occuring in temperate latitudes and in salt water environments, having similar integrument (though lepisosteidids have far more robust scales) and even having eyes located in a medium, forward oriented position in the skull (unlike the eyes of crocodillians, hippos and amphibious vertebrates, with eyes on a very dorsal position), as indicative of the reliance of eyesight in hunting.

Recent studies appearently have shown that the snouts of Lepisosteus and Atractosteus are uncannily similar in shape to those of Champsosaurus and Simoedosaurus respectively, and neochoristodere teeth have historically been noted as very gar-like.

Considering modern gar genera co-existed with neochoristoderes, this is especially interesting for our understanding of early Cenozoic aquatic biomes. Studying gars might also shed light as to why these fish survived and neochoristoderes died out.

One Comment leave one →
  1. December 17, 2015 12:06 pm

    Not all turtles are semi-aquatic. There are some, like the Carettochelys insculpta, that even in morphology they have copied the marine turtles, and are almost entirely aquatic. Some soft-shells can also be considered completely aquatic, and snappers are a borderline case. Also there are the acrochordid snakes.

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