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Mooi, R. & David, B. 1996. Phylogenetic analysis of extreme morphologies: deep-sea holasteroid echinoids. Journal of Natural History 30, 913-953.
10.1080/00222939600770501 [view]
Mooi, R.; David, B.
Phylogenetic analysis of extreme morphologies: deep-sea holasteroid echinoids
Journal of Natural History
30: 913-953
Available for editors  PDF available [request]
Because of their 'bizarre' features, some echinoids can be considered laboratories in which to analyse the origin of extreme morphologies. The holasteroid family Urechinidae Duncan, 1889 is such a group. It is composed of 18 previously named living species in three genera: Urechinus A. Agassiz, 1879, Plexechinus A. Agassiz, 1898, and Pilematechinus A. Agassiz, 1904. With Stereopneustes, the most closely related living taxon, and the calymnid-plus-pourtalesiid clade as outgroups, a phylogenetic analysis on 35 binary characters is produced. We focus on two major aspects of morphology: test features (apical system, basicoronals, interambulacrum 5, test shape, ambulacra) and external appendages (pedicellariae, spines, sphaeridia). New data on plate architecture, morphology, and appendages are illustrated, and the position of the fossil, Chelonechinus, is discussed. We show that the Urechinidae is paraphyletic: the genus Plexechinus shares more recent common ancestry with the calymnids and pourtalesiids than with other urechinids. In order to retain the well-circumscribed clade, Pilematechinus A. Agassiz, 1904, the phylogenetic classification also recognizes two additional genera: Cystechinus A. Agassiz, 1879, and Antrechinus new genus. A key to the species is provided. The production of extreme morphologies, such as internal parental care, is explored by mapping test size, the occurrence of fascioles, and periproct position onto the phylogeny. By adding plates early in ontogeny, Pilematechinus develops radically different plate architectures from another genus of large forms, Cystechinus. In contrast, the latter gets large by exaggerating allometric trends seen in other holasteroids. Paedomorphosis and miniaturization have evolved independently in Antrechinus and some Plexechinus, but always by truncation of allometric trajectories.
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2013-01-12 18:30:12Z
2014-03-21 09:39:14Z
2014-06-20 17:00:44Z

Antrechinus Mooi & David, 1996 (status source)
Antrechinus drygalskii (Mortensen, 1905) (new combination reference)
Antrechinus mortenseni (David & Mooi, 1990) (new combination reference)
Antrechinus nordenskjoldi (Mortensen, 1905) (new combination reference)
Cystechinus A. Agassiz, 1879 (status source)
Cystechinus giganteus (A. Agassiz, 1898) (new combination reference)
Cystechinus loveni A. Agassiz, 1898 (status source)
Cystechinus wyvillii A. Agassiz, 1879 (status source)
Pilematechinus A. Agassiz, 1904 (status source)
Pilematechinus belyaevi Mironov, 1975 (status source)
Pilematechinus rathbuni (A. Agassiz, 1898) (status source)
Pilematechinus vesica (A. Agassiz, 1879) (status source)
Plexechinidae Mooi & David, 1996 (original description)
Plexechinus A. Agassiz, 1898 (status source)
Plexechinus aoteanus (McKnight, 1974) (status source)
Plexechinus cinctus A. Agassiz, 1898 (status source)
Plexechinus hirsutus Mortensen, 1905 (status source)
Plexechinus nordenskioldi Mortensen, 1905 accepted as Antrechinus nordenskjoldi (Mortensen, 1905) (status source)
Plexechinus parvus (Mironov, 1978) (new combination reference)
Plexechinus planus (Mironov, 1978) (status source)
Plexechinus spectabilis Mortensen, 1948 (status source)
Urechinidae Duncan, 1889 (taxonomy source)
Urechinus A. Agassiz, 1879 (status source)
Urechinus antipodeanus McKnight, 1974 (status source)
Urechinus aoteanus McKnight, 1974 accepted as Plexechinus aoteanus (McKnight, 1974) (status source)
Urechinus drygalskii Mortensen, 1905 accepted as Antrechinus drygalskii (Mortensen, 1905) (status source)
Urechinus giganteus A. Agassiz, 1898 accepted as Cystechinus giganteus (A. Agassiz, 1898) (status source)
Urechinus loveni (A. Agassiz, 1898) accepted as Cystechinus loveni A. Agassiz, 1898 (status source)
Urechinus mortenseni David & Mooi, 1990 accepted as Antrechinus mortenseni (David & Mooi, 1990) (status source)
Urechinus naresianus A. Agassiz, 1879 (status source)
Urechinus planus Mironov, 1978 accepted as Plexechinus planus (Mironov, 1978) (status source)
Urechinus reticulatus H.L. Clark, 1913 (status source)
Urechinus wyvilli (A. Agassiz, 1879) accepted as Cystechinus wyvillii A. Agassiz, 1879 (status source)

Mooi & David (1996: p. 915) commented: "We do not here consider the taxonomically confused genus Carnarechinus ... [details]


Placed into the genus Antrechinus Mooi & David, 1996 by Mooi & David, 1996: 946 [details]