Rhenanid

Presence in the fossil record

The fossil record of Rhenanida is very sparse, with most fossils being isolated tubercles and skull fragments that are identified as being similar to Gemuendina stuertzi, the most well-known rhenanid, known from several specimens from the Hunsruck slates. Given the rhenanids' worldwide distribution, this paupacity probably did not reflect a scarcity of living individuals (when the order was alive), but reflects the fact that rhenanid armor disintegrated into isolated fragments, and scattered soon after the owner's demise. Most fossils of rhenanids are from the Early Devonian, primarily in the United States and Germany. The recently discovered Nefudina qalibahensis is known from Northeastern Saudi Arabia. Asterosteus stenocephalus is known from Mid Devonian Ohio. Another species of rhenanid was Bolivosteus chacomensis, of the Lower to Middle Devonian Malvinokaffric Fauna of Western Gondwana, in what is now Bolivia, South America. The youngest rhenanid, Jagorina pandora is known from Upper Devonian Germany.