Teeth and Fossils

Teeth in the fossil record are massively over-represented. However, as one of the hardest bits of the body and a portion that is replaced often and with some regularity, the discovery of teeth more than any other portion of a fossilized body is not at all surprising. Placodus teeth have been recovered for centuries in fossil deposits and at one point or another various species of the genus were identified mainly by teeth. A species named by Owen in 1858 (and another species given the same name in 1863 by Meyer) was described using teeth and partial cranial remains, but has since been reassigned to another genus of placodonts (Cyamodus). The cranium and skull (cranium plus mandible) have been described numerous times with different goals in mind. Sues (1987) described the phylogenetic relationships of the placodonts using a description of the skull of P. gigas. Fifteen years later the skull of P. gigas was again described, but with a more specific goal in mind. Neenan and Scheyer (2012) specifically described the anatomy of the inner ear and the braincase of a specimen of P. gigas using computed tomography (CT).

Not all of the studies conducted with Placodus are description based or anatomy centered of course. A number of studies such as Diedrich 2010 and Diedrich 2013 have assessed the paleoecology of Placodus. Diedrich 2013, specifically, describes the life of a Placodus as very "sea cow" like; in other words, Placodus was, as we mentioned on Saturday, very much like a Triassic manatee. Bone beds of "several thousand individual 'Triassic sea cows'" are used to describe the communal living of Placodus in the shallow seas covering an immense portion of what is now Europe. Diedrich 2013 was based partially off of the conclusions of Diedrich 2010 which discussed the paleocological role of Placodus using anatomical characteristics and laying the foundation of the "sea cow" - like analogy.