Page 437 - Introduction to Paleobiology and The Fossil Record

424 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

Box 15.10 The Vetulicolians: protostomes, deuterostomes or phylogenetic
orphans?

Sometimes the fossil record throws out a weird animal that it is just impossible to classify. The
material may be common, distinctive and well preserved but there are simply not enough key
characters to link it with other groups. The vetulicolians have been characterized as unusual
arthropods, stem-group deuterostomes and even tunicates (Aldridge et al. 2007). They have been
reported from a number of Cambrian Lagerstätten and two classes have been recognized, the
Vetulicolida and Banffozoa. They were probably active, nektobenthic animals with the facility to

both deposit and filter feed. But what were they? In simple terms they lack limbs, making
assignment to the arthropods difficult, whereas they have gills similar to those of the deuterostomes

(Fig. 15.31). If they were, in fact, deuterostomes they probably lay close to the tunicates as stem
vertebrates. But despite well-preserved material from the Chengjiang fauna and careful phylogenetic
analyses, it remains impossible to classify them. Their unique combination of characters is thus still
an enigma awaiting the discovery of new animals that could link the vetulicolians to a crown
group.

(a)

(b)
Figure 15.31 (a) Photograph (scale bar, 5 mm) and (b) reconstruction of Vetulicola. (Courtesy of
Dick Aldridge.)