Bauer et al.—Blastoid hydrospire morphology 1 Hp 2 Hp 3 Hp


849


Hc Hc Ht Ht Lancet plate Side plate Hg Radial plate


Figure 2. Ambulacral plating in relation to hydrospires in several representative spiraculate species. (1) Orbitremites derbiensis Sowerby, 1825 possessed a single hydrospire fold with a thin hydrospire cleft leading to the hydrospire tube at the end. (2) Globoblastus norwoodi (Owen and Shumard, 1850) possessed paired hydrospire folds with a bifurcating cleft leading to two hydrospire tubes. (3) Pentremites godoni (DeFrance, 1819) possessed five hydrospire folds within the hydrospire group; an elongate hydrospire cleft along the plates accommodates the additional folds. Hc = hydrospire cleft; Hg = hydrospire group; Hp = hydrospire pore; Ht = hydrospire tube. Modified from Beaver (1967).


morphology of organisms (e.g., Beaver et al., 1967; Beerbower, 1968; Breimer and Dop, 1975; Katz and Sprinkle, 1976, 1977; Broadhead, 1984; Breimer, 1988a, b; Waters and Horowitz, 1993; Dexter et al., 2009; Schmidtling and Marshall, 2010). Thin sections and acetate peels of serially sectioned thecae have previously been used to render hydrospire morphology in 2D (Breimer and Macurda, 1972) as well as 3D (Schmidtling and Marshall, 2010; Huynh et al., 2015). A comprehensive investi- gation of hydrospire morphotypes has recently begun in three dimensions (Waters et al., 2014, 2015; Bauer et al., 2015). For a more detailed discussion on methodology, see Waters et al. (2014, 2015). Herein, we describe the digital transformation of 2D serial peels into 3D models of hydrospire morphology for examination and character coding.


Acetate peel data.—A collection of unpublished serial acetate peels contains serial sections of 19 fissiculate species and 27 spiraculate species spanning the taxonomic diversity of Blastoidea. Peels were taken perpendicular to the thecal axis, and some of the peels contain minor flaws (e.g., wrinkles, tears, and bubbles), which can mask internal morphology or result in data loss (Waters et al., 2015). Peels were scanned (by J.A.W.) with a Braun slide scanner at 3,600 dpi and 8-bit grayscale. Once scanned, the peels were resized and compiled in Adobe Photoshop (Fig. 3.1) and the hydrospires were located and traced on each peel (Fig. 3.2). Once completed, the original photo layers were hidden, and what remained was a series of drawings that traced the hydrospires vertically through the theca. The image was then compressed and transferred into Rhinoceros, an industrial design program used to render 2D images in 3D. Within Rhinoceros, the images were connected to generate complete hydrospire structures (Fig. 3.3, 3.4).


Phylogenetic analysis.—As this work is ongoing, a phylogeny incorporating all known blastoid taxa is not currently available. Previously utilized external character data are undergoing large- scale revision to provide a more complete data set to generate character suites that better characterize large morphological change (Supplemental Data 1). Herein, we investigate taxa that


1 2 Ht


Hc


34


Figure 3. Deltoblastus permicus is an example of anatomical model reconstruction methodology. (1) Digital transverse slices are cut out and aligned in the same direction. Target areas of internal morphology can be identified as seen by the white box. (2) This enlarged box of (1) shows the hydrospires in the target area traced in black. Scale bar represents 0.5 cm. (3) Aerial and (4) oblique lateral view of completed D. permicus model. (2) Scale bar = 0.5 cm; (3, 4) scale bar = 1 cm. Modified from Waters et al. (2014) and Bauer et al. (2015).


have completed internal models in addition to several other taxa that have been suggested to be closely related (Atwood, 2013). The objective is to assess whether the addition of hydrospire data, although currently limited, has an effect on tree topology. Phylogenetic analysis was performed via maximum parsimony in PAUP* 4.0b10 (Swofford, 2003). Characters were equally weighted and unordered and examined via exhaustive search parameters (Supplemental Data 2). The outgroup taxon was Stephanocrinus angulatus Conrad, 1842 based on sister taxon relationships identified in previous studies (Sprinkle, 1973; Broadhead, 1982, 1984; Brett et al., 1983).


{


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