Charles Messing's Crinoid Pages: Crinoid Taxonomy
Crinoid Taxonomy
Crinoid taxonomy has been, until recently, almost entirely based on skeletal morphology. Many original species diagnoses were muddled and based on inconsistent character analyses. Many of the problems associated with distinguishing crinoid species and genera exist, because it has turned out that many traditionally applied features vary with growth, habitat, depth and/or location, and because many species were originally described from one or a few specimens with little if any understanding of growth or variability among and within populations. Even today, a significant percentage of accepted crinoid species are based on five or fewer specimens.
Much of contemporary feather star classification derives from Austin H. Clark’s monograph (1915, 1921, 1931, 1941, 1947, 1950, and, with Ailsa M. Clark, 1967). On one hand, Clark was an unadulterated splitter, often maintaining species as distinct despite exhibiting, in the author’s own estimation, minor variations (e.g., A. H. Clark 1947). From 1907 to 1909, he described 75 genera and 17 family-level taxa, almost all feather stars, derived from a combination of new material (e.g., Albatross) and revisions of previous collections (e.g., Blake, Challenger). He published 21 papers in 1909 alone. As examples, he maintained Dichrometra, Liparometra, and Lamprometra as separate genera based only on the relative lengths of the first three pinnules. In 1931 (p. 434), he wrote: “An examination of the notes given herewith on specimens determined as C. multifida and as C. gracilis shows that in no single feature is there a sharp dividing line between the two. Nevertheless, in most cases they are very easily distinguishable. It can therefore scarcely be doubted that these two forms are representatives of the same specific type. What their true relation is must be left for future determination.” On the other hand, he placed numerous previously described species names in synonymy, e.g., 14 under Lamprometra palmata alone.
For stalked species, family-level and higher classification has varied widely, with multiple different arrangements proposed, e.g., for Isocrinida (Rasmussen & Sieverts-Doreck 1978, Roux 1981, Simms 1988, Klikushkin 1982, Simms et al. 1993, Hess 2011a), and with some taxa bounced around multiple higher groups, e.g., Bourgueticrinidae and Bathycrinidae in a separate order Bourgueticrinida (Rasmussen 1978), and in a suborder within orders Millericrinida (Roux 1977), Comatulidina (Simms et al. 1993; Jagt 1999) and Comatulida (Hess 2011b).
In some cases, a combination of newly collected specimens and re-examination of existing ones have supported placing species and genera in synonymy, especially for taxa distinguished on the basis of size, arm number, and number of cirrals that appear to form growth series. Messing et al. (2000) placed Aglaometra incerta under A. valida, because the former differed only in size (smaller) and degree of ornamentation but separated chiefly shallower- versus deeper-water specimens into two species—Atelecrinus balanoides and A. helgae—based on multiple morphological features (Messing 2013). Rankin & Messing (2008) reduced six species of Stephanometra to two, and Messing (1998) placed Comatella maculata under C. stelligera, both cases based on large numbers of intermediate specimens. Correction of such errors could reduce the number of recognized feather star species from about 540 to 490.
In many cases, however, it is difficult to tell if similar but consistently distinct forms found at different depths or habitats represent different species or merely varieties. Much of a crinoid’s anatomy is suspension-feeding apparatus that may develop differently under different flow regimes. For example, specimens of Anneissia bennetti from shallower, often turbulent reef crests in the western Pacific (1-20 m) have more numerous, shorter arms than those found in deeper (>15-40 m) or quieter waters (Messing 2007). Similarly, Meyer & Macurda (1980) and Messing (2007) found a form of Capillaster multiradiatus at depths as shallow as 1 m at Palau that differed in behavior (diurnally cryptic) and color from specimens recorded from deeper water on other western Pacific reefs. Thus, although many species may be reduced to synonymy, many others may contain cryptic or sibling species currently unrecognized within named taxa.
Molecular work is clarifying the status of more and more crinoid taxa at all categorical levels, in some cases supporting existing taxonomy; in others, revealing new relationships. On one hand, Taylor et al. (2017a) placed Himerometra magnipinna and H. martensi under H. robustipinna, and (2014b) synonymized the genera Lamprometra and Liparometra under Dichrometra, and Summers et al. (2017) placed Comaster nobilis under C. schlegelii. On the other hand, Hemery et al. (2012) found seven genetically distinct lineages (phylogroups) of the Antarctic Promachocrinus kerguelensis that may represent two cryptic species with no morphological differences (see also Eléaume et al. 2014).
On a larger scale, molecular analyses have returned some family-level taxa as monophyletic, e.g., Comatulidae (formerly Comasteridae), Charitometridae, and Thalassometridae, and others as polyphyletic, e.g., Colobometridae, Antedonidae, Antedonacea, and Tropiometracea. They have also squarely placed some stalked groups (Bourgueticrinina, Guillecrinina) within order Comatulida, which formerly included only feather stars (Hemery 2011, Hemery et al. 2013, Rouse et al. 2013). Unfortunately, new clades revealed by robust molecular data sometimes have no supporting morphological characters, e.g., Comatellinae, Neocomatellini, and previously used morphological characters sometimes prove to be convergent, e.g., arm branching patterns, pinnule comb form (Summers et al. 2014).
A great deal of work remains to be done, using both molecular and morphological approaches, and new species continue to be discovered (e.g., Messing 2020).
References
Clark AH 1915. A monograph of the existing crinoids, 1(1). Bull. U. S. Nat. Mus. (82): vi + 406, 17 pls.
Clark AH 1921. A monograph of the existing crinoids. 1(2). Bulletin of the United States National Museum (82), xxvi + 795, 57 pls.
Clark AH 1931. A monograph of the existing crinoids. 1(3) Superfamily Comasterida. Bulletin of the United States National Museum 82. viii + 816 pp., 82 pls.
Clark, A.H. 1941. A monograph of the existing crinoids. 1(4a). Bull. U. S. Natl. Mus. 82:1-603, 61 pls.
Clark, A.H. 1947. A monograph of the existing crinoids. 1(4b). Bull. U. S. Natl. Mus. 82:1-473, 43 pls.
Clark, A.H. 1950. A monograph of the existing crinoids. 1(4c). Bull. U. S. Natl. Mus. 82:1-383, 32 pls.
Clark AH & Clark, A. M. 1967. A monograph of the existing crinoids 1(5). Bulletin of the United States National Museum (82):1-860.
Eléaume, M., Hemery, L.G., Améziane, N., Roux, M. 2014. Chapter 10.7, Phylogeographic patterns of the Southern Ocean crinoids (Crinoidea: Echinodermata). Pp. 448-455 IN: De Broyer C., et al. (eds.), Biogeographic Atlas of the Southern Ocean. Scientific Committee on Antarctic Research, Cambridge.
Hemery, L.G., Eléaume, M., Roussel, V., Améziane, N., Gallut, C., Steinke, D., Cruaud, C., Couloux, A. and Wilson, N.G. 2012. Comprehensive sampling reveals circumpolarity and sympatry in seven mitochondrial lineages of the Southern Ocean crinoid species Promachocrinus kerguelensis (Echinodermata). Molecular Ecology 21(10): 2502-2518.
Hess, H. 2011a. Isocrinida. Treatise on Invertebrate Paleontology. Part T, Echinodermata 2, Revised, Crinoidea, Vol. 3. Pp. 42-69 IN Seldon, P. (ed.), Ausich, W.I. (coord. author). Lawrence, Kansas, The University of Kansas Paleontological Institute.
Hess, H. 2011b. Bourgueticrinina. Treatise on Invertebrate Paleontology.Part T, Echinodermata 2, Revised, Crinoidea, Vol. 3. Pp. 146-159 IN: Seldon, P. (ed.), Ausich, W.I. (coord. author). Lawrence, Kansas, The University of Kansas Paleontological Institute.
Jagt, J.W.M. 1999. Late Cretaceous - Early Palaeogene echinoderms and the K/T boundary in the south-eastern Netherlands and north-eastern Belgium. Pt. 1, Introduction and stratigraphy; Pt. 2, Crinoids. Scripta Geologica 116: 1-255.
Klikushin, V.G., 1982. Taxonomic survey of fossil isocrinids with a list of the species found in the USSR. Geobios, 15(3): 299-325.
Messing, C.G. 1998. An initial re-assessment of the distribution and richness of the East Indian shallow-water crinoid fauna. IN: Mooi, R., Telford, M. (eds.), Echinoderms, San Francisco. Balkema, Rotterdam.
Messing, C.G. 2007. The crinoid fauna (Echinodermata: Crinoidea) of Palau. Pacific Science 61(1): 91-111. https://doi.org/10.1353/psc.2007.0010
Messing, C.G. 2013. A revision of the genus Atelecrinus PH Carpenter (Echinodermata: Crinoidea). Zootaxa 3681 (1): 001–043. http://dx.doi.org/10.11646/zootaxa.3681.1.1
Messing CG (2020) Erratum: A revision of the unusual feather star genus Atopocrinus with a description of a new species (Echinodermata: Crinoidea). Zootaxa 4772 (3): 600–600. https://doi.org/10.11646/zootaxa.4772.3.11
Messing CG (2020) A revision of the unusual feather star genus Atopocrinus with a description of a new species (Echinodermata: Crinoidea). Zootaxa 4731 (4): 471–491. https://doi.org/10.11646/zootaxa.4731.4.2
Messing, C.G., Améziane, N., Eléaume, M. 2000. Comatulid crinoids of the KARUBAR Expedition to Indonesia: the families Comasteridae, Asterometridae, Calometridae and Thalassometridae (Echinodermata: Crinoidea). IN: Crosnier, A., Bouchet, P. (eds.) Résultats des Campagnes MUSORSTOM 21. Mémoires de la Museum national d'Histoire naturelle 184: 627-702.
Meyer, D.L., Macurda, D.B., Jr. 1980. Ecology and distribution of shallow-water crinoids of Palau and Guam. Micronesica, 16(1): 59-99.
Rankin, D.L., Messing, C.G. 2008. A revision of the comatulid genus Stephanometra A.H. Clark with a rediagnosis of the genus Lamprometra A.H. Clark (Echinodermata: Crinoidea). Zootaxa 1888: 1-35.https://doi.org/10.5281/zenodo.184295
Rasmussen, H.W. 1978. Evolution of articulate crinoids. Treatise on Invertebrate Palaeontology. Part T Echinodermata 2. Vol. 1. Pp. T302-T316 IN: Moore, R.C., Teichert, C. (eds.) Lawrence, Kansas, The Geological Society of America, Inc.: Boulder, Colorado and The University of Kansas.
Rasmussen, H.W., Sieverts-Doreck, H. 1978. Articulata. Treatise on Invertebrate Paleontology. Part T. Echinodermata 2. Crinoidea. Vol. 3. Pp. T813-T1027 IN: Moore, R.C., Teichert (eds.), C. Kansas, Geological Society of America and University of Kansas Press.
Rouse, G.W., Jermiin, L.S., Wilson, N.G., Eeckhaut, I., Lanterbecq, D., Oji, T., Young, C.M., Browning, T., Cisternas, P., Helgen, L.E., Stuckey, M., Messing, C.G. 2013. Fixed, free, and fixed: the fickle phylogeny of extant Crinoidea (Echinodermata) and their Permian-Triassic origin. Molecular Phylogenetics and Evolution 66(1):161-81. https://doi.org/10.1016/j.ympev.2012.09.018
Roux, M. 1977. Les Bourgueticrinina (Crinoidea) recueillis par la Thalassa dans le golfe de Gascogne: anatomie comparée des pédonculés et systématique. Bulletin du muséum d'Histoire Naturelle, Section A Zoologie Biologie et Ecologie Animales 4(2): 31-57.
Roux, M. 1981. Echinodermes: Crinoïdes Isocrinidae. Resultats des Campagnes MUSORSTOM. 1 Philippines (18–28 mars 1976). Mémoires de ORSTOM 91: 477–543.
Simms, M.J., Gale, A.S., Gilliland, P., Rose, E.P.F., Sevastopulo, G.D. 1993. Echinodermata. The Fossil Record 2. Pp. 491-528 IN: Benton, M.J. Ed.) London, Chapman & Hall.
Summers, M., Messing, C.G., Rouse, G.W. 2014. Phylogeny of Comatulidae (Echinodermata: Crinoidea: Comatulida): A new classification and an assessment of morphological characters for crinoid taxonomy. Molecular Phylogenetics and Evolution 80: 319-39. https://doi.org/10.1016/j.ympev.2014.06.030
Summers, M.M., Messing, C.G., Rouse, G.W. 2017. The genera and species of Comatulidae (Comatulida: Crinoidea): taxonomic revisions and a molecular and morphological guide. Zootaxa, 4268(2), 151-190. http://dx.doi.org/10.11646/zootaxa.4268.2.1
Taylor, K., Rouse, G., Messing, C. 2017a. Systematics of Himerometra (Echinodermata: Crinoidea: Himerometridae) based on Morphology and Molecular Data. Zoological Journal of the Linnean Society 181(2): 342–356. https://doi.org/10.1093/zoolinnean/zlx009
Taylor, H.K., Rouse, G.W., Messing, C.G. 2017b. Revising Mariametridae: the genera Dichrometra, Lamprometra, and Liparometra (Echinodermata: Crinoidea). Systematics and Biodiversity 16(2): 142-159. http://dx.doi.org/10.1080/14772000.2017.1375044