STYLOPATHIDAE OPRESKO, 2006

Brugler, Mercer R., Opresko, Dennis M. & France, Scott C., 2013, The evolutionary history of the order Antipatharia (Cnidaria: Anthozoa: Hexacorallia) as inferred from mitochondrial and nuclear DNA: implications for black coral taxonomy and systematics, Zoological Journal of the Linnean Society 169 (2), pp. 312-361 : 341-342

STYLOPATHIDAE OPRESKO, 2006

Based on external morphology, the familiy Stylopathidae (three genera, nine species) appears intermediate between the Antipathidae and the schizopathid Parantipathes . Stylopathids are characterized by a limited amount of morphological variation in the growth form of the corallum; colonies are pinnulate and bottlebrush in shape, or flabellate. There are no unbranched forms known. In those forms that are pinnulate, there is a tendency for the pinnules to occur in subopposite pairs or to be arranged in verticils of three or four; in some species, adjacent pinnules and branches may fuse or anastomose to form cylindrical, reticulated worm-runs (i.e. a tube that houses a polychaete) along the stem or branches ( Opresko, 2006). The spines are conical, smoothsurfaced, and often distally directed (i.e. growing at an acute angle with the spine tip pointing in the direction of axial growth); they do not become more needle-like on the branches or antler-like on the stem and holdfast as in the Myriopathidae . The polyps are generally less than 1.5 mm in transverse diameter and tend to be somewhat elongated in an axial direction, slightly more so than the Myriopathidae . There is some evidence suggesting that the tentacles in expanded polyps are relatively short and rounded, thus similar to those in the Myriopathidae (D.M.O., personal observation).

Based on morphological analyses, three species, representing two genera, were obtained for sequencing, of which two could be referred with certainty to valid nominal species ( Table 1 & Supporting information Table S1). We were only able to obtain complete mt-contig sequence data for species within the genus Stylopathes . A small fragment (125 bp) of igrN from the holotype of Triadopathes triadocrada ( Opresko, 1999) (USNM 99410) was also obtained. Except for a single ambiguity in igrN of T. triadocrada , its sequence was identical to that from a specimen of Stylopathes sp. (NIWA 16047) collected from the Kermadec Ridge (north-east of New Zealand). Without additional taxon sampling within Triadopathes Opresko, 2006 and Tylopathes Brook, 1889 , the monophyly of the Stylopathidae could not be determined. In particular, the genus Tylopathes is morphologically dissimilar from both Stylopathes and Triadopathes , and from the Myriopathidae , in that it is non-pinnulate and flabellate. The possibility remains that phenotypes are diverging faster than genotypes, and thus the genetic markers are simply reflecting ancient relationships between these two families. Alternatively, the Stylopathidae and Myriopathidae may be hybridizing, leading to close genetic relationships and disparate morphologies (indeed, D.M.O. notes that an undescribed species from the Atlantic appears to be a hybrid).

In all mt-contig phylogenies, Antipathes dendrochristos grouped within the Stylopathes clade, sister to S. litocrada Opresko, 2006 . This result is not too surprising as there are some morphological features that suggest a relationship among A. dendrochristos , Stylopathes columnaris ( Duchassaing, 1870) , and related species, i.e. the shape of the spines, the tendency for the branchlets to be subopposite in a few places, and the length of the tentacles relative to the size of the polyps. Based on polyp and spine morphologies, Opresko (2005a) noted that A. dendrochristos and related species [ A. speciosa ( Brook, 1889) and A. minor ( Brook, 1889) ] may be taxonomically distinct from more typical members of the genus Antipathes and that molecular data might help resolve the issue. Based on the results presented here, it is clear that A. dendrochristos belongs in the family Stylopathidae . Morphologically, this species is closer to Tylopathes than to the other genera in the family. Obtaining sequences from species of Tylopathes will be instrumental in determining if A. dendrochristos should be placed in Tylopathes or a separate genus.

Only a single representative of the Stylopathidae [ Stylopathes sp. (NIWA 16047)] was included in the nuc-contig phylogenies, and it grouped sister to the single representative of the Myriopathidae [ Tanacetipathes barbadensis (USNM 1116465); BS and BPP: 100], and this S + M complex grouped sister to E. abietina (BS: 90.6; BPP: 68–99), as seen in the mt-contig phylogenies.