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Figure 8 in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 8. Geological sketch map of the Heathcote area showing Wenlock-Lochkovian fossil localities yielding homalonotids. For other fossil localities see also Thomas (1940a, 1940b, 1941, 1956), Talent (1964, fig. 1), Sandford (2002, fig. 1A; 2005, fig. 4).

Figure 3 in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 3. Sandstone slab from PL2204 (Thomas' F4, Parish of Dargile), Heathcote with bedding plane showing numerous isolated pygidia and cranidia of Digonus wenndorfi in various orientations and with large bivalves and brachiopods indicative of Boucot and Johnson's (1967) 'big shell' community.

Figure 5 A, D in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 5 A, D. Moult assemblages of Trimerus (Edgillia) kinglakensis in the upper siltstones at PL252, Middendorps Quarry, Kinglake West, Humevale Siltstone. A, upper right, displaced and inverted cephalon lying underneath thoracopygon (only anterior margin visible); left, thoracopygon with displaced and rotated cephalon. D, thoracopygon with displaced and rotated cephalon. B–C. Complete dorsal exoskeletons in sandstone bioclastic coquinas. B, Trimerus (Trimerus) harrisoni from PL1820, Brunswick, Melbourne Formation. C, Wenndorfia lilydalensis from PL1805, Coldstream. Humevale Siltstone.

Figure 4 in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 4. Relationship between trilobite faunal diversity and homalonotid relative abundance. Only homalonotid-bearing faunas represented by more than 10 specimens are plotted. The curve connects plot-points of hypothetical faunas where species are represented in equal proportional relative abundance. Homalonotid faunas cluster in two groups, lower diversity faunas with homalonotids over-represented (above the line) and high diversity faunas with homalonotids generally under-represented (below the line).

Figure 2 in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 2. Stratigraphic distribution of homalonotids in the Heathcote, Springfield-Kinglake West and Lilydale sequences in central Victoria, and in Tasmania and New Zealand. Stratigraphic scheme for the Llandovery-Ludlow of central Victoria follows Rickards and Sandford (1998), and for the Ludlow-Lochkovian follows Sandford (2002).

Figure 1 in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 1. Distribution of fossil marine faunas with homalonotids in south eastern Australia and New Zealand. Localities for the Heathcote, Springfield-Kinglake West and Lilydale areas are detailed in Figures 8, 11 and 23.

Figure 11 in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 11. Geological sketch map of the Springfield-Kinglake West area showing Llandovery-Lochkovian fossil localities yielding homalonotids. For other fossil localities see also Jutson (1908, pl. 3), Thomas (1960), Talent (1964, fig. 1), Williams (1964, fig. 2), Garratt (1972, 1977), Rickards and Sandford (1998, fig. 6), Sandford (2002, fig. 1C; 2005, figs 2–3).

Figure 23 in Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)

Figure 23. Geological sketch map of the Lilydale area showing Lochkovian-basal Pragian fossil localities yielding homalonotids. For other fossil localities see also Gill (1940, fig.1, 1945, fig. 2), Moore (1965, fig.1), VandenBerg (1970), Garratt (1972), Wall et al. (1995, fig. 1), Sandford (2003, text-fig. 1A, 2004, fig. 1).

FIGURE 5 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 5. Principal components analysis of 3D fixed and semi landmarks. 1, PC 1 vs PC 2; point size represents relative centroid size of specimen. 2-4, Landmark configuration of shape represented by low PC 1 score, typical of largest specimens, in dorsal, anterior, and right lateral views, respectively. 5-7, Landmark configuration of shape represented by high PC 1 score, typical of smallest specimens, in dorsal, anterior, and right lateral views, respectively.

FIGURE 4 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 4. Slice through volume rendering of Cryptolithus tesselatus (AMNH FI-101479), shown in dorsal view in inset. Red line in inset shows the orientation of the slice across the specimen. Bright white area is sediment trapped within the bilaminar structure of the cephalon. Blue arrows point to suture between upper and lower lamellae; red arrows point to fringe-pits.

FIGURE 1 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 1. Cephalon of Cryptolithus tesselatus (AMNH FI-101479) showing morphological terms used in this paper, following Whittington (1968) and Hughes et al. (1975). Concentric arcs are labeled according to their placement relative to the girder (expressed on the ventral side): E = external; I = internal. "Fringe-pits" are circled in yellow; the "F-pits" represent a subset of these interior to the labeled concentric arcs. Specimen is 6.6 mm long.

FIGURE 8 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 8. Length vs width of Cryptolithus tesselatus cephala, coded for the number of concentric arcs of fringe-pits expressed in each specimen. The first three concentric arcs (E, I1, and I2) are complete when first expressed. Based on clustering, I3 is likely completed over three molts, first by only 1-3 fringe-pits, then 8-10 fringe-pits, then 13-15 fringe-pits with the anteriormost in line with the 10th radial rows of fringe-pits in arcs E-I. The dataset includes the 23 2 specimens, which were CT-scanned as well as 31 additional silicified specimens from the collection; specimens that were CT-scanned are outlined in red. Arrows indicate the specimens shown in Figures 1 and 7. Inset in upper right corner is a magnified view of the specimens in the dashed box. The scaling component describing the relationship between length and width is 1.153 (1 = isometric growth).

FIGURE 7 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 7. Additions of fringe-pits associated with early meraspid stages of ontogeny in Cryptolithus tesselatus. 1, meraspid stage 2 showing two concentric arcs of fringe-pits, AMNH FI-101498, x35. 2, meraspid stage 2 showing two concentric arcs of fringe-pits, AMNH FI-101499, x35. 3, merapid stage 3 showing three concentric arcs of fringe-pits and first few fringe-pits of I3, FI-101496, x20. 4, later meraspid stage showing complete set of fringe-pits, AMNH FI- 101494, x15. Scale bars are 1 mm.

FIGURE 3 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 3. Placement of points defining patch on glabella. Points in red are redundant to fixed landmarks as described in the text and Appendix 2. After the surface landmarks were extracted using Landmark Editor, the redundant landmarks were removed from the final data file. Specimen shown is AMNH FI-101482; specimen is 7.1 mm long.

FIGURE 10 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 10. Allometry in the cranidia/cephala of other trilobite species as described by 2D geometric morphometrics. 1, Marrolithus bureaui, data from figure 5 of Delabroye and Crônier (2008), breakpoint shown is at 2.8, which was the best supported threshold model (Table 2). 2, Aulacopleura koninckii, data from figure 3 of Hong et al. (2014), breakpoint set at 2.0. 3, Triarthrus becki, data from figure 6 of Kim et al. (2002); breakpoint at 0.6. 4, Zacanthopsis palmeri, data from figure 13 of Hopkins and Webster (2009), breakpoint set at 0.8. 5, Haniwa quadrata, data from figure 5 of Park and Choi (2011b), breakpoint set at 1.4. 6, Liostracina tangwangzhaiensis, data from figure 3 of Park et al. (2014), breakpoint set at 1.55. 7, Apatokephalus latilimbatus, data from figure 4 of Park and Kihm (2015), breakpoint set at 0.85. 8, Olenellus gilberti, data from figure 23B of Webster (2015), breakpoint set at 1.0. Breakpoints are all in units of natural log of centroid size. Red lines = linear regression models; blue lines = threshold models.

FIGURE 2 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 2. Different views of 3D surface model rendering of Cryptolithus tesselatus showing placement of fixed landmarks. All landmarks are indicated at least once, with the exception of 11 (paired with 12). Unpaired landmarks = 17– 20; paired landmarks = 1–16, 21–23, 42; semi-landmarks along first internal list shown by dashed line and represented by landmarks 24–41. See Appendix 2 for full description of all landmarks. Surface reconstruction is of AMNH FI-101479.

FIGURE 9 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 9. Ontogeny of Cryptolithus tesselatus based on 2D geometric morphometrics. 1, Fixed landmarks consistently recognizable in dorsal view. Red dashed line shows curve described by first internal list along which were placed 21 semi-landmarks. Specimen shown is AMNH FI- 101479; specimen is 6.7 mm long. 2, Principal components analysis of 2D fixed- and semi-landmarks. Point size represents relative centroid size of specimen. Insets are deformation plots showing shapes represented by largest and smallest PC 1 values. 3, Allometric curve; amount of shape change represented by the Procrustes distance between each specimen and the smallest specimen. Red solid line = linear regression model; blue solid line = threshold model 1; thin black dashed line = threshold model 2; thick black dashed line = threshold model 3. Threshold model 1 is the best supported model (Table 1).

FIGURE 6 in Non-linear ontogenetic shape change in Cryptolithus tesselatus (Trilobita) using three-dimensional geometric morphometrics

FIGURE 6. Allometric growth in Cryptolithus tesselatus. Size (x-axis) is represented by the natural log of centroid size. Change in shape (y-axis) is represented by the Procrustes distance between each specimen and the smallest specimen in the dataset; the Procrustes distances in this case represent the relative amount of change that specimens underwent during development. Red solid line = linear regression model; blue solid line = threshold model 1; thin black dashed line = threshold model 2; thick black dashed line = threshold model 3. Threshold model 1 is the best supported model.

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FIG. 8 in Diversification of Asaphellus Callaway, 1877 (Asaphidae: Trilobita) during the Tremadocian in South West Gondwana (Cordillera Oriental, Argentina)

FIG. 8. — Asaphellus stenorhachis (Harrington, 1938): A, cranidium, dorsal view, CEGH-UNC 25736; B, cephalon, latex cast, dorsal view, CEGH-UNC 25737; C, hypostoma, dorsal view, CEGH-UNC 25738; D, right free cheek, dorsal view, CEGH-UNC 25739; E, dorsal view of a complete specimen, CEGH-UNC 25740; F, right free cheek, dorsal view, CEGH-UNC 25741; G, pygidium and articulated thorax, dorsal view, CEGH-UNC 25742; H, cranidium with incomplete thorax and fragmentary pygidium, latex cast, dorsal view, CEGH-UNC 25743; I, cranidium with articulated thorax and pygidium, dorsal view, CEGH-UNC 25744; J-L, pygidia, dorsal view; J, CEGH-UNC 25745; K, CEGH-UNC 25746; L, CEGH-UNC 25747; M, pygidium and fragmentary articulated thorax, dorsal view, CEGH-UNC 25748. A, D, J, K, are preserved in coquinas. All specimens come from Quebrada del Arenal, Santa Rosita Formation, Santa Victoria Group; A-C, E, G-I, L, come from DLA 32; D, J, K, from DLA 37; F, from DLA 34; M, from DLA 31. Scale bars: B, E-G, I, L, 0.5 cm; A, C, D, H, J, K, M, 0.25 cm.