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Studies of trilobites using geometric morphometrics

Abe, F.R. and Lieberman, B.S. 2012. Quantifying morphological change during an evolutionary radiation of Devonian trilobites. Paleobiology , 38:292-307.

Adrain, J.M. 2005. Aulacopleurid trilobites from the Upper Ordovician of Virginia. Journal of Paleontology, 79:542-563.

Adrain, J.M. and Westrop, S.R. 2006. New earliest Ordovician trilobite genus Millardicurus : the oldest known hystricurid. Journal of Paleontology, 80:650-671.

Bignon, A. and Crônier, C. 2012. Evolutionary modifications of ontogeny of three Dechenella species (Proetidae), from the Middle Devonian of the Ardenne Massif (France). Journal of Paleontology, 86:558-566.

Crônier, C. and Fortey, R. 2006. Morphology and ontogeny of an Early Devonian phacopid trilobite with reduced sight from southern Thailand. Journal of Paleontology, 80:529-536.

Crônier, C., Auffray, J.C., and Courville, P. 2005. A quantitative comparison of the ontogeny of two closely‐related Upper Devonian phacopid trilobites. Lethaia, 38:123-135.

Cronier, C., Feist, R., and Auffray, J.C. 2004. Variation in the eye of Acuticryphops (Phacopina, Trilobita) and its evolutionary significance: a biometric and morphometric approach. Paleobiology , 30:471-481.

Delabroye, A. and Crônier, C. 2008. Ontogeny of an Ordovician trinucleid (Trilobita) from Armorica, France: a morphometric approach. Journal of Paleontology, 82:800-810.

Fusco, G., Hughes, N.C., Webster, M., and Minelli, A., 2004, Exploring developmental modes in a fossil arthropod: growth and trunk segmentation of the trilobite Aulacopleura koninckiAmerican Naturalist, 163:167-183.

Gendry, D., Courville, P., Saucède, T., Laffont, R., and Paris, F. 2013. Contribution of morphometrics to the systematics of the Ordovician genus Neseuretus (Calymenidae, Trilobita) from the Armorican Massif, France. Journal of Paleontology, 87:456-471.

Gerber, S. and Hopkins, M.J. 2011. Mosaic heterochrony and evolutionary modularity: the trilobite genus Zacanthopsis as a case study. Evolution, 65:3241-3252.

Hong, P.S., Hughes, N.C., and Sheets, H.D. 2014. Size, shape, and systematics of the Silurian trilobite Aulacopleura koninckii. Journal of Paleontology, 88:1120-1138.

Hopkins, M.J. 2011. How species longevity, intraspecific morphological variation, and geographic range size are related: a comparison using Late Cambrian trilobites. Evolution, 65:3252-3273.

Hopkins, M.J. 2013. Decoupling of taxonomic diversity and morphological disparity during decline of the Cambrian trilobite family Pterocephaliidae. Journal of Evolutionary Biology, 26:1665-1676.

Hopkins, M.J. and Webster, M. 2009. Ontogeny and geographic variation of a new species of the corynexochine trilobite Zacanthopsis (Dyeran, Cambrian). Journal of Paleontology, 83:524-547.

Hughes, N.C. and Chapman, R.E. 1995. Growth and variation in the Silurian proetide trilobite Aulacopleura konincki and its implications for trilobite palaeobiology. Lethaia, 28:333-353.

Hughes, N.C. and Chapman, R.E. 2001. Morphometry and phylogeny in the resolution of paleobiological problems--unlocking the evolutionary significance of an assemblage of Silurian trilobites, p. 29-54. In Adrain, J.M., Edgecombe, G.D., and Lieberman, B.S. (eds.), Fossils, Phylogeny, and Form. Springer.

Hunda, B.R. and Hughes, N.C. 2007. Evaluating paedomorphic heterochrony in trilobites: the case of the diminutive trilobite Flexicalymene retrosa minuens from the Cincinnatian series (Upper Ordovican), Cincinnati region. Evolution and Development, 9:483-498.

Kim, K., Sheets, H.D., Haney, R.A., and Mitchell, C.E. 2002. Morphometric analysis of ontogeny and allometry of the Middle Ordovician trilobite Triarthrus becki. Paleobiology, 28:364-377.

Kim, K., Sheets, H.D., and Mitchell, C.E. 2009. Geographic and stratigraphic change in the morphology of Triarthrus beckii (Green) (Trilobita): a test of the Plus ça change model of evolution. Lethaia, 42:108-125.

MacLeod, N. 2002. Phylogenetic signals in morphometric data, p. 100-138. In MacLeod, N. and Forey, P.L. (eds.), Morphology, Shape and Phylogeny. CRC Press.

McCormick, T. and Fortey, R.A. 1999. The most widely distributed trilobite species: Ordovician Carolinites genacinaca. Journal of Paleontology, 73:202-218.

McCormick, T. and Fortey, R.A. 2002. The Ordovician trilobite Carolinites, a test case for microevolution in a macrofossil lineage. Palaeontology, 45:229-257.

Park, T.-Y. and Choi, D.K. 2011. Ontogeny of the Furongian (late Cambrian) remopleuridioid trilobite Haniwa quadrata Kobayashi, 1933, from Korea: implications for trilobite taxonomy. Geological Magazine, 148:288-303.

Park, T.-Y.S. and Kihm, J.-H. 2015. Post-embryonic development of the Early Ordovician (ca. 480 Ma) trilobite Apatokephalus latilimbatus Peng, 1990 and the evolution of metamorphosis. Evolution & Development,17:289-301.

Park, T.-Y.S., Kihm, J.-H., Kang, I., and Choi, D.K. 2014. Ontogeny of a new species of the Cambrian Series 3 (Middle Cambrian) trilobite genus Liostracina Monke, 1903 from North China and the taxonomic position of the superfamily Trinucleoidea. Journal of Paleontology, 88:395-402.

Sheets, H.D., Kim, K., and Mitchell, C.E. 2004. A combined landmark and outline-based approach to ontogenetic shape change in the Ordovician trilobite Triarthrus becki, p. 67-82. In Elewa, A.M.T. (ed.), Morphometrics: Applications in Biology and Paleontology. Springer, Berlin.

Simpson, A.G., Hughes, N.C., Kopaska-Merkel, D.C., and Ludvigsen, R. 2005. Development of the caudal exoskeleton of the pliomerid trilobite Hintzeia plicamarginis new species. Evolution & Development , 7:528-541.

Smith, L.H. 1998. Asymmetry of Early Paleozoic trilobites. Lethaia, 31:99-112.

Smith, L.H. 1998. Species level phenotypic variation in lower Paleozoic trilobites. Paleobiology, 24:17-36.

Smith, L.H. and Lieberman, B.S. 1999. Disparity and constraint in olenelloid trilobites and the Cambrian radiation. Paleobiology, 25:459-470.

Webber, A.J. and Hunda, B.R. 2007. Quantitatively comparing morphological trends to environment in the fossil record (Cincinnatian Series, Upper Ordovician). Evolution, 61:1455-1465.

Webster, M. 2015. Ontogeny and intraspecific variation of the early Cambrian trilobite Olenellus gilberti, with implications for olenelline phylogeny and macroevolutionary trends in phenotypic canalization. Journal of Systematic Palaeontology, 13:1-74.

Webster, M. and Hughes, N.C. 1999. Compaction-related deformation in Cambrian olenelloid trilobites and its implications for fossil morphometry. Journal of Paleontology, 73:355-371.

Webster, M. and Zelditch, M.L. 2005. Evolutionary modifications of ontogeny: heterochrony and beyond. Paleobiology, 31:354-372.

Webster, M. and Zelditch, M.L. 2011. Evolutionary lability of integration in Cambrian ptychoparioid trilobites. Evolutionary Biology, 38:144-162.

Webster, M. and Zelditch, M.L. 2011. Modularity of a Cambrian ptychoparioid trilobite cranidium. Evolution and Development, 13:96-109.


Description of 3D landmarks taken from each Cryptolithus tesselatus cephalon. All of the following orientations describe a specimen with the anterior margin facing upwards unless otherwise specified.

1. Anterior pit at edge tangent to axial furrow, right side

2. Anterior pit at edge tangent to axial furrow, left side

3. Anterior apodome at edge tangent to axial furrow, right side

4. Anterior apodome at edge tangent to axial furrow, left side

5. Posterior (occipital) apodome at edge tangent to axial furrow, right side

6. Posterior (occipital) apodome at edge tangent to axial furrow, left side

7. Apex of anterior pit (left side in ventral view)

8. Apex of anterior pit (right side in ventral view)

9. Apex of anterior apodome (left side in ventral view)

10. Apex of anterior apodome (right side in ventral view)

11. Apex of posterior (occipital) apodome (left side in ventral view)

12. Apex of posterior (occipital) apodome (right side in ventral view)

13. Node at junction between occipital lobe and posterior margin, right side

14. Node at junction between occipital lobe and posterior margin, left side

15. Fulcrum on posterior border, right side

16. Fulcrum on posterior border, left side

17. Median glabellar tubercle

18. Intersection of preglabellar furrow with sagittal axis

19. Intersection of suture between upper and lower lamellae and sagittal axis

20. Intersection of occipital furrow with sagittal axis

21. Lateral-most extent of furrow along posterior margin of genal lobe, right side. Usually just above interior-most F-pit.

22. Lateral-most extent of furrow along posterior margin of genal lobe, left side

23. Anchor point for semi-landmarks along first internal list, placed where list intersects with posterior margin, left side

24-41. Semi-landmarks along first internal list

42. Anchor point for semi-landmarks along first internal list, placed where list intersects with posterior margin, right side.


Three-dimensional landmark data used in this study in TPS format. Fixed landmarks: 1-23, 42. Semi-landmarks along a curve: 24-41, numbered from left to right. Surface semi-landmarks: 43-67. Landmarks 1, 2, 17, and 18 are redundant with landmarks 63, 67, 55, and 65, respectively. See text and Appendix 2 for more details. Replicates are designated as “A” and “B” (available as txt file).

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