WHEN THEORETICAL MORPHOLOGY GETS REAL: 3-D PRINTING OF IDEALIZED TURRITELLID GASTROPOD SHELLS TO BETTER UNDERSTAND THE FUNCTION OF SCULPTURE AND WHORL SHAPE (Invited Presentation)

3-D printing offers the opportunity to test hypotheses of functional morphology in ways that fossil or modern materials cannot. 3-D printing replaces the need for destructive or potentially destructive analyses when form is the only subject of a hypothesis. Further, 3-D printed models are not restricted to exact replication of natural objects, allowing us to not only increase standardization, but also to disentangle the importance of morphological features which may not be found independently in nature.

The majority of turritellid gastropods are semi-infaunal suspension feeders, burying themselves just below the sediment-water interface. Previous experiments on standardized replicas of six extant and fossil species indicated that strong spiral sculpture may reduce unburial in wave-influenced conditions, but not under strong unidirectional currents.

In order to disentangle the effects of whorl profile, spiral sculpture, and beading/minor sculpture we generated nine artificial turritellid morphologies – straight-sided, rounded, and carinate whorl profiles with zero, one, or two spiral ribs— in Blender and printed these in VeroWhitePlus. These models were then tested in 10 fifteen-minute trials in a wave tank to examine sediment retention.

The unribbed straight-sided and double-ribbed carinate forms had the highest incidence of complete exposure, but no whorl profile or sculptural condition out-performed any other in a statistically significant manner, either individually or in aggregate. When carinate whorl profile is considered with the ribbed/carinate condition there is a lower incidence of complete exposure when compared with the smooth straight-sided and smooth round models, but exposure occurs in both populations.

Similar whorl profile and sculptural morphologies occur repeatedly through the 160 million year evolutionary history of turritellid gastropods, which is highly suggestive of adaptive significance. It is possible that the medium-coarse sand environment of testing was not ideal for any of the sculptural patterns examined, or that sculpture is adaptive for an untested reason. One possibility is resistance to crushing predation, which is also amenable for testing using 3-D printed models.