Meeting Abstract
The Clypeasteroida is a diverse clade of sea urchins commonly known as sand dollars. The largely Indo-Pacific clypeasteroid genus Fibularia is significant among these because of extreme miniaturization (hence, “micro-echinoids”) — the smallest known extant echinoid is a Fibularia. Here, we greatly expand a dataset containing morphometry and morphological information on all known extant and fossil species of Fibularia. Graphical representations of several crucial parameters reassess relationships among all the known extant taxa of Fibularia, including new material from recent Philippine expeditions. These analyses reveal two new living species as well as previously unrecognized cases of sexual dimorphism among several taxa, underscoring unusual, unstudied, and therefore enigmatic life history traits. Fossil material sent to us by colleagues working in Australia, New Zealand, and Madagascar expands knowledge of the diversity of Oligocene and Eocene Fibularia. Among these localities, there are at least three new species. With this new knowledge of diversity within Fibularia, we attempt to derive phylogenetic relationships that illuminate evolution of significant features within Fibularia. However, extreme paedomorphic reduction (truncation of ontogenetic trajectories leading to loss of terminally-added apomorphies) among these micro-echinoids continues to make phylogenetic work challenging. Nevertheless, present results indicate that sexual dimorphism evolved more than once within the group, that brooding behavior has evolved at least once, and that there is a taxonomically confused subset (though possibly not monophyletic) of Fibularia in the Eocene of the western Indian Ocean, including Madagascar. [Supported by NSF BIO REU grant 1358680 to Mooi]
