Tubercles bearing spines that have different functions are generally morphologically distinct. It is therefore possible to use tubercle structure and distribution to be more precise about how fossil ...

Fossils collected by ROM reveal Odaraia had ... found an intricate system of small and large spines. According to the authors, these spines could intertwine, capturing smaller prey as though ...

Finally, a single interambulacral plate may be found towards the posterior of the plastron in some holasteroids and spatangoids; this is the rostral plate. The plastron may be entirely covered in ...